Welcome Welcome to IC-03, the 2003 National Conference of the Inorganic Chemistry Division of the Royal Australian Chemical Institute.
An outstanding group of international researchers have contributed plenary papers to the meeting across a range of key current themes in inorganic chemistry. Building on these, the program has been enriched and broadened by the contributions that all of you will present as poster and as session lecture papers.
The plenary lectures, shorter oral and poster paper sessions have important roles in our program. The plenary lectures set the stage for the major themes, the session lectures have been selected to develop these themes, and the daily poster sessions deliberately cover all the topics, to encourage each of us to look beyond our expert comfort zone, perhaps deliberately or perhaps serendipitously, the way many good ideas come from noticing the paper next to the one we went looking for in a printed journal.
The conference is an opportunity to recognize outstanding career contributions from among our colleagues as well as showcase the exciting work from our many student members. The Burrows Award and the D.R.Stranks Award sessions are highlights of the conference program.
Using the poster sessions, breaks, reception and dinner, we hope you will catch up with old friends and make many new connections. We are delighted to welcome you to Melbourne and to The University of Melbourne. While you are here, we hope to share and enjoy your company as well as your science.
Peter Tregloan
Organising Committee Associate Professor Peter Tregloan, School of Chemistry, The University of Melbourne (Chair) Dr Stephen Best, School of Chemistry, The University of Melbourne Dr Peter Junk, Chemistry Department, Monash University Dr David McFadyen, School of Chemistry, The University of Melbourne Professor Richard Robson, School of Chemistry, The University of Melbourne Professor Tony Wedd, School of Chemistry, The University of Melbourne Associate Professor Charles Young, School of Chemistry, The University of Melbourne
Meeting Organiser Meetings First 4/184 Main Street LILYDALE VIC 3140
Sponsors The Organising Committee and the Inorganic Chemistry Division of the RACI would like to gratefully acknowledge the support of the following sponsors:
Centre for Green Chemistry, Monash University Australian Journal of Chemistry Varian Australia Pty Ltd Campbell Microanalytical Laboratory Pearson Education Australia General Information Registration and enquiries will be in the foyer of the Prince Philip Lecture Theatre near the Conference rooms. Meetings First staff will be in attendance as follows:
Sunday February 2 4.00 pm - 6.00 pm Monday February 3 8.00 am - 6.00 pm Tuesday February 4 8.00 am - 6.00 pm Wednesday February 5 8.00 am - 1.00 pm Thursday February 6 8.00 am - 6.00 pm
Conference sessions will be held in the Prince Philip Lecture Theatre (Architecture Building) or Old Geology Lecture Theatre 1 (Old Geology Building)
Morning and afternoon teas will be held in the Atrium on Level 1 of the Architecture Building. Delegates should make their own lunch arrangements – Union House or Lygon Street provide a wide range of options.
The Welcome Reception will be held in The Ian Potter Museum of Art (on Swanston Street near Gate 3, opposite 800 Swanston Street) from 7.00 pm until 8.30 pm on Sunday, February 2.
The Conference Dinner will be held at the San Remo Ballroom (365 Nicholson Street, Carlton) from 7.30 pm on Thursday, February 6. Complimentary parking is available at St Brigid’s Primary School at 378 Nicholson Street. For those without cars, it would take about 20 minutes to walk from the colleges or somewhat less in a taxi.
University visitors are advised that parking is generally available at all times at weekends. A fee of $2 is payable into the coin machines at Monash Road (Gate 4) off Swanston Street, and Grattan Street (Gate 10). Please note that coins only are accepted. Between 7am and 11pm Monday to Friday the University Square Carpark is open to the public. The entrance is off Berkeley Street and is $2.50 per hour or a maximum of $7.00 all day.
Presenter Guidelines The time you have been allocated on the program includes questions - please allow at least 5 minutes for questions within the time allotted.
Plenary Lectures will be limited to 50 minutes plus 10 minutes questions. Session speakers will be limited to 25 minutes plus 5 minutes questions. Stranks Award finalists will be limited to 10 minutes plus 5 minutes questions.
A PC and a Mac, each with PowerPoint 2000, overhead projectors and 35 mm slide projectors are available in each lecture theatre
Because of the larger projection area, speakers are encouraged to use computer projection. There will be no facilities for personal laptop computers to be used. Please save your file onto a floppy disk, 100 Mb Zip disk or CD-ROM. Don't forget to check your fonts. We recommend you use Arial, Times and Symbol only. PowerPoint tip: if you have PowerPoint XP, click "Embed fonts".
For a smoothly running program it is important that speakers make sure their presentation runs using the ‘local’ computer/projector arrangement before their session. All presentation files will be loaded to the appropriate theatre computer and tested prior to the sessions each day.
Regardless of what media you are using, please go the appropriate theatre during the morning tea/poster session, to familiarise yourself with the equipment and, if using data projection, to have your files loaded onto the computer. Support staff will be in attendance.
Poster Presentations Daily poster sessions have been scheduled. All poster presenters are asked to ensure their poster is ready for viewing by 8.30 am on the scheduled day. Posters can be mounted on the poster boards after 4.30 pm on the day before they are scheduled for display.
Please check your abstract number in the abstract book and display your poster on the corresponding panel. Velcro dots are available from Meetings First.
Presenting authors should be in attendance for the duration of the morning tea/poster session.
Posters may be removed at any time after the poster session but must be taken down by 4.00 pm each day.
Chair Guidelines All chairpersons are asked to familiarize themselves with the equipment prior to the commencement of their session. Chairpersons are asked to keep presenters strictly to time.
Getting Around The maps below show the general University area and the key locations for IC-03.
The CAL Laboratory, just inside the main door of the School of Chemistry, is available as a drop in centre for delegates to check and send email. The iMac computers in the lab have web and Telnet access. There are no facilities for members to connect their own computers to the University network. There are no printing facilities in the lab.
Program Outline
PMO Poster Session Monday PTU Poster Session Tuesday PWE Poster Session Wednesday PTH Poster Session Thursday
MP Monday, Prince Philip Theatre MG Monday, Old Geology Theatre 1 TP Tuesday, Prince Philip Theatre TG Tuesday, Old Geology Theatre 1 RP Thursday, Prince Philip Theatre RG Thursday, Old Geology Theatre 1
Sunday, 2 February 2003
4:00 pm to 7:00 pm Registration Prince Philip Theatre Foyer
5:30 pm to 7:00 pm Conference Opening Prince Philip Theatre Chair: A/Professor Peter Tregloan Professor Richard Keene Chair, Inorganic Chemistry Division Professor Frank Larkins The University of Melbourne
Plenary Lecture 1 Prince Philip Theatre Chair: Dr Richard Robson 01 18:00 Molecular Self-assembly Through Coordination: From Professor Makoto Fujita Squares to Polyhedra to "Cavity-directed Synthesis" University of Tokyo
7:00 pm to 8:30 pm Welcome Reception Ian Potter Museum of Art
Monday, 3 February 2003
9:00 am to 10:00 am Plenary Lecture 2 Prince Philip Theatre Chair: Professor Glen Deacon 02 9:00 Bifunctional Ligands in the Synthesis of Mono- and Professor Evamarie Oligonuclear Transition Metal Complexes Hey-Hawkins, Universität Leipzig
10:00 am to 11:30 am Poster Session (PMO) and Morning Tea Architecture Atrium 03 Carbonate-Based Coordination Polymers Abrahams BF, Hawley A, Haywood M, Robson R, Slizys DA 04 Complexes of Divalent and Trivalent Ruthenium Adams JR, Martin BA, Incorporating Tethered Arenes Yellowlees LJ 05 Reactivity Studies of Ainscough EW, Brodie AM, 1-Benzoyl-3-(2,4,6-tri-tert-butylphenyl)thiourea and Burrell AK, Indira Chandrasena Related Ligands ILKG, Bowmaker GA 06 195m-Pt Radiolabelling of Cisplatin: An Improved Smith SV, Di Bartolo N, Synthetic Pathway Alderden R, Alexander M, Jackson T, Papazian V, Nygen V, 07 Lumen Loading of Halloysite Nanotubes Antill SJ, Green MER, Kepert CJ 08 Differences in Ligand Donor Preferences Between Appleton TG, Hoang HN, Palladium(II) and Platinum(II) in Reactions with Tronoff A S-Methylglutathione 09 Direct Evidence for CN- Binding to the Nitrogenase Vincent K, Ibrahim S, Fairhurst S, Cofactor: New Redox States and New Chemistry Gormal C, Smith B, Pickett C, Best S 10 An Homologous Series of Metal Complexes: Co(III) Jaffray PM, Clark CR, Blackman Carbonato and Bicarbonato Complexes Containing AG Tripodal Pyridine Ligands
11 Fe2(pdt)(CO)6, a Model of the CO Inhibited {2Fe2S} Borg SJ, Razavet M, Pickett CJ, Subsite of the Hydrogenase H-Cluster? Best SP 12 Photoinduced Electron Transfer in Metal Ion Activated Bradbury AJ, Campbell R, Fluorescent Molecular Receptors Wainwright KP, Lincoln SF 13 Di- and Poly-nuclear Cobalt(II) Pyridazine Complexes as Brooker S, de Geest DJ, Kelly Potential Nano-components RJ, Plieger PG, Moubaraki B, Murray KS 14 Stereochemical Effects on Intervalence Charge Transfer D'Alessandro DM, Keene FR in Polymetallic Supramolecular Assemblies 15 Cyclen-based Water Soluble Metal Ion Activated Molecular Damsyik A, Wainwright KP, Receptors Lincoln SF 16 Tunable Crystal Host Properties in Ainscough EW, Brodie AM, (Pyridyloxy)Cyclotetraphosphazenes Derwahl A 17 Novel Reactivity of high Valent Biomimetic Molybdenum Doonan CJ, Young CG Complexes 18 Near Naked Cationic Lanthanoid Complexes Deacon GB, Evans DJ, Forsyth CM, Junk PC 19 Structural Investigations into the Unexplored Hydroxamic Failes TW, Hall MD, Hambley Acid Chemistry of Pt(II) TW 20 Synthesis, Electrochemistry and Spectroscopy of Curnow OJ, Fern GM, Jenkins Substituted bis(indenyl)iron(II) Complexes EM, Klaib S, Lang H 21 The Preparation and Reaction of Some Crowded Fester VD, Nicholson BK, Main L Ortho-manganated Aryl Ketones 22 New Square-Planar Cationic Platinum(II) Compounds: A Fisher DM, Fenton RR, Cure for Cancer? Aldrich-Wright JR 23 Complexes of Vanadium(III) with Acetate Brasch NE, Edwards AJ, Fry FH, MaCann NC 24 Radical Cleavage and Aggregation Processes in Goh LY Cyclopentadienylchromium Chemistry 25 Guest-Dependent Spin Crossover in Nanoporous Halder GJ, Kepert CJ, Molecular Framework Materials Moubaraki B, Murray KS, Cashion JD 26 Does Platinum(IV) Survive in Tumour Cells? Hall MD, Amjadi S, Beale P, Cai Z, Dillon CT, Foran GJ, Lai B, Stampfl AP, Zhang M, Hambley TW
Monday, 3 February 2003
27 Rare Earth Complexes From High Temperature Syntheses Deacon GB, Junk PC, Harika R, Leary SG, Skelton BW, White AH 28 Synthesis and Structural Studies of Some Lanthanoid(III) Deacon GB, Harika R, Junk 1,2-Benzenedisulfonates PC, Skelton BW, White AH 29 Self-Assembly of Di- and Tetranuclear Copper(II) Hausmann J, Brooker S Complexes of Two Homologous Bis-Terdentate Diamide Ligands 30 Towards Soluble Heavy Alkaline Earth Metals: Calcium, Hitzbleck J, Ruhlandt-Senge K Strontium, and Barium Complexes of Anthracene Derivatives 31 Synthesis and Structure of a Series of Boron Porphyrins- Hodgson MC, Brothers PJ, Highlighting the Different Structural Motifs Rickard CEF, Weiss A, Siebert W 32 Electrochromic Linear and Nonlinear Optical Properties of Humphrey MG, Powell CE, Alkynylbis(diphosphine)ruthenium Complexes Cifuentes MP, Morrall JP, Stranger R, Samoc M, Luther-Davies B, Heath GA 33 Stabilisation of Double a-Helix Conformers of Dinuclear Kitto HJ, Wild SB Metal Helicates Containing Tetra(tertiary phosphines) 34 Copper(II) Binding Proteins in Bacteria Koay MS, Xiao Z, Wedd AG
35 New Coordination Polymers using Dicyanamide and Kutasi AM, Batten SR, Nitrogen-Donor Heterocyclic Ligands Moubaraki B, Murray KS 36 New Super- and Supramolecular Receptor Systems, Beves J, Dong Y, Chartres J, Cages, Chains, Squares and Dendrimers Incorporating Lindoy LF, Meehan GV Macrocycles as Structural Elements 37 Cobalt Hub-Caps: Keeping the Wheel on the Axle Lock JS, Lincoln SF, May BL, Easton C 38 Photoactivated Ligand Release From Cobalt(III) Boyd S, Ghiggino KP, Anthrylmethyl Cyclam Derivatives McFadyen WD 39 A New Single Molecule Magnet: Price DJ, Batten SR, Moubaraki [Mn16O16(OMe)6(OAc)16(MeOH)3(H2O)3]·6H2O B, Murray KS 40 Charge-Transfer in Fluorescent Ferrocenium Dyads McAdam CJ, Flood A, Robinson BH, Simpson J 41 Substituted-Pyridine Complexes of Molybdenum Carbonyl Wimmer FL, Jait A - Electrochemistry and Electronic Spectra
11:30 am to 12:30 pm Plenary Lecture 3 Prince Philip Theatre Chair: Dr Stephen Best 42 11:30 Structural and Functional Models for the Hydrogenase Professor Thomas Rauchfuss Enzyme Active Sites University of Illinois
12:30 pm to 2:00 am Lunch - own arrangements
2:00 pm to 4:00 pm Organometallic Chemistry (MP1) Prince Philip Theatre Chair: Dr Peter Junk 43 14:00 Metallaboratranes: Metal à Boron Dative Bonding Edwards AJ, Hill AF, Humphrey ER, Foreman MR, Neumann H, Owen GR, Tshabang N, White AJP, Williams DJ, Willis AC 44 14:30 Structure and Reactivity of Mono- and Bimetallic Andrews PC, Calleja SM, Chiral Amides Duggan PJ, D'Elia A, Maguire M 45 15:00 From Obscurity to Actuality: New Developments in the Ruhlandt-Senge K, Alexander J, Organometallic Chemistry of the Heavy Alkaline Earth Metals Englich U 46 15:30 Modified Calix[4]pyrroles Designed to Improve Cloke FG, Gardiner MG, Skelton Coordination Sphere Control of Lanthanide Metals: BW, Scherer W, Wang J, Synthesis of Sm(II) and Sm(III) Complexes White AH
Monday, 3 February 2003
2:00 pm to 4:00 pm Biological Inorganic Chemistry (MG1) Old Geology Lecture Theatre 1 Chair: Professor Andrew Brodie 47 14:00 Manganese Superoxide Dismutase In Reduced And Jameson G Oxidised Forms At Ultra-High Resolution (0.90 Å): Where Are The Hydrogens And What Are They Doing? 48 14:30 {2Fe3S} - Assemblies Related to the Sub-site of Razavet M, Cui Z, George SJ, All-iron Hydrogenase Liu X, Pickett CJ, Borg SJ, Best SP 49 15:00 Structural Models for Motifs Involved in Biological McKenzie C Metal-mediated H Atom Abstraction
50 15:30 Models for the Cub-his-tyr Centre in Proton-Pumping Colbran SB, Lee ST, Heme-Copper Oxidases Paddon-Row MN, Craig DC
4:00 pm to 4:30 pm Afternoon Tea Architecture Atrium
4:30 pm to 6:00 pm Organometallic Chemistry (MP2) Prince Philip Theatre Chair: Dr Mark Humphrey 51 16:30 Is There a Role for Palladium(IV) in Catalysis? Canty AJ 52 17:00 Ferrocenyl-Substituted Dithiolene Complexes: Near-IR Sanders RW, Absorbers at Record Wavelengths Mueller- Westerhoff UT 53 17:30 Unique Reactions of Heterocyclic Carbene Complexes: Cavell KJ Important Ramifications for their Application in Catalysis
4:30 pm to 6:00 pm Biological Inorganic Chemistry (MG2) Old Geology Lecture Theatre 1 Chair: Professor Peter Lay 54 16:30 An Electronic Structure Description of the cis-MoOS Unit in Kirk M, Rubie N, Peariso K, Models for Molybdenum Hydroxylase Active Sites Doonan CJ, Young CG, George GN 55 17:00 Molybdo-Enzyme Electrochemistry: From Redox Potentials Aguey-Zinsou KF, Bernhardt PV, to Biocatalysis McEwan AG 56 17:30 High Resolution EPR Spectroscopy: Advances, New Hanson GR Techniques and Applications to Metalloproteins and Materials Science.
Tuesday, 4 February 2003
9:00 am to 10:00 am Plenary Lecture 4 Prince Philip Theatre Chair: Professor Len Lindoy 57 9:00 From Simple Coordination Chemistry to Professor Edwin Constable Supramolecular Arrays University of Basel
10:00 am to 11:30 am Poster Session (PTU) and Morning Tea Architecture Atrium 58 Lanthanide Oxyacids as Corrosion Inhibitors Battle A, Behrsing T, Deacon GB, Forsyth CM, Forsyth M, Hambley TW, Leary S 59 Chemistry of Metalloalkynes. Reactions of Ruthenium Byrne LT, Griffith CS, Ethynediyl Complexes Koutsantonis GA, Skelton BW
60 Oxidation of Copper(I) Complexes in Gold Ore Lixiviants Black J, Spiccia L, McPhail DC Based on Thiosulfate 61 Nanomolar Dissociation Constants of the Bisintercalating Brodie CR, Aldrich-Wright JR, Complexes of Glazer E, Luedtke N, Tor Y 4+ [(dpq)2Ru(phen-n-SOS-n-phen)Ru(dpq)2] (where n = 3, 4 or 5 and SOS = -S-(CH2)2-O-(CH2)2-S-)
62 Alternative Leach Reagents for the Thiosulfate Gold Brown TA, Spiccia L, McPhail Leaching Process DC 63 Mechanism of Action of Platinum Complex Binding to DNA Bulluss GH, Waller MP, Hambley TW 64 Cobalt Complexes as Potential Radiation-Activated Chang JY, Brothers PJ, Denny Anticancer Prodrugs WA, Rickard CE, Ware DC 65 Suppression of Reactivity by Product-Solvation: Synthetic Cole ML, Davies AJ, Jones C, Ramifications of h6:h1-Binding in Bulky Junk PC Di(aryl)formamidinate Complexes of Potassium 66 Synthesis and Crystal Structure of Porous Network Mulyana Y, Lindoy LF, Kepert Constructed from Self-assembly of Zinc(II) and 4-Pyrazolyl CK, Turner P Pyridine (Hpzpy) 67 Mechanistic Investigations into the Unprecedented meso Curnow OJ, Fern GM, Hamilton to rac Isomerisation of Some Bis-Planar Chiral ML, Jenkins EM Ferrocenyldiphosphines 68 Pyrazolates Continue to Amaze - The New m-h2:h1 Binding Deacon GB, Forsyth CM, Gitlits Mode and Spectacular Trinuclear Homoleptic Complexes A, Harika R, Junk PC, Skelton Incorporating m-h5:h2 Coordination BW, White AH 69 Catalytic Gas Phase Oxidation of Methanol to Formaldehyde Waters T, O'Hair RAJ, Wedd AG, 70 Transition Metal Propargylidynes Dewhurst RD, Edwards AJ, Hill AF 71 The Extraction of Heavy Metals from Polluted Sediments Fang B, James JM, Barnes C, Using Chelating Agents Found in Commercial Softeners Lindoy LF 72 An Investigation of Ruthenium(II) Polypyridyl Complexes of Howard WA, Aldrich-Wright JR the Intercalating Ligand Dipyrido[6,7-d:2'3'-f](6,7,8,9-tetrahydro)phenazine 73 Fundamental Studies of Solar Energy Materials: Vibrational Howell SL, Gordon KC Spectroscopy and ab initio Studies of 1,10-phenanthroline and its Complexes. 74 Rhodium-based Coordination Chemistry of Edwards AJ, Hill AF, Poly(methimazolyl) Ligands Humphrey E 75 The Structure-Activity Relationship of Square-Planar Jaramillo D, Brodie CR, Collins Platinum(II) Metallointercalators JG, Fenton RR, Aldrich-Wright JR 76 Calix-[4]-pyrroles: New Ligands From Old Hosts Ji XK, Black DS, Colbran SB, Willett GD 77 Beyond Transition Metal Amidinates: Highlights of the Cole ML, Evans DJ, Junk PC, Coordinative Versatility of Formamidinates Toward Louis LM Diverse Group 1 Metal Assemblies
Tuesday, 4 February 2003
78 Supramolecular Binding of Fullerenes to Porphyrins Boyd PDW, Kennedy SMF
79 Synthesis and Structural Characterisation of Dinuclear Klingele MH, Brooker S Complexes of the Novel 1,2,4-Triazole-Based Ligands TsPMAT and PMAT 80 Exciting New Phosphanamide Chemistry Cole ML, Evans DJ, Deacon GB, Junk PC, Konstas K 81 Hazard and Risk Assessment of the Anti-valve Seat Harvey G, Willcocks D, Weder J Recession Agent Methylcyclopentadienyl Manganese Tricarbonyl (MMT) 82 Alkyne Exchange at Phosphenium Centres Brasch NE, Hamilton IG, Krenske EH, Wild SB 83 Processing of the Same Ligand Using Different Coordination Brooker S, Lan Y, Kennepohl D, Algorithms Controls the Molecular Architecture of the Moubaraki B, Murray K Resulting Complex: Grid Versus Side-by-side Complexes
84 NMR Studies of CpRe(CO)2(cycloalkane) Sigma-Bond Lawes D, Ball GE Complexes 85 Determination of Polyhydride Structure Using NMR Liu XY, Ball G E Spectroscopy 86 Formation of Osmium-Silicon and -Tin Metallacycles Lu G-L, Rickard CEF, Roper WR, Wright LJ 87 Manganese Mediated Reaction of Conjugated Mace WJ, Nicholson BK, Main L, a-heterodiene Complexes with Unsaturated Compounds. van de Pas D 88 Electrochemistry of Polyoxometalates in the Ionic Liquid Mariotti AWA, Bond AM, Wedd [bmim][PF6] AG 89 Gas-phase Studies on the Reactivity of Wee S, McFadyen WD, O'Hair (2,2':6',2"-terpyridine)platinum(II) and RA (diethylenetriamine)platinum(II) Azido Complexes 90 Intramolecular Electron and Energy Transfer in Moore EG, Bernhardt PV, Riley Bichromophoric Macrocycles MJ, Vauthey E 91 Synthesis and Characterisation of New Hybrid Moubaraki B, Batten SR, - Spin-Crossover M(dca)3 Network Complexes. A Rare Cashion JD, Murray KS Lonsdaleite Structural Motif 92 Coordination Polymers and Isomerism Cordes DB, Caradoc-Davies PL, Hanton LR, Lee K, Spicer MD 93 New Catenane Synthesis via a Schiff Base Condensation Fenton RR, Lindoy LF, Meehan GV, Perkins DF, Price JR 94 The Synthesis and Study of Metal Complexes of Ligands Sumby CJ, Steel PJ with Tripodal Tridentate Binding Domains 95 Enzyme-like Catalysis by a Doped Conducting Polymer. Chen J, Huang J, Swiegers GF, Proximity Effects Generated by Concentration Too CO, Wallace GG
96 The Incorporation of Cr3+, Fe3+, Cu2+ and Pb2+ within Tong AR, Kennedy BJ, Singh B, Synthetic Kaolinite 97 Carbon-Oxygen Bond Formation at Metal(IV) Centres: Canty AJ, Denney MC, Reactivity of Palladium(II) and Platinum(II) Complexes of van Koten G, Skelton BW, the "NCN-Pincer" Ligand Toward Iodomethane and White AH Dibenzoyl Peroxide 98 Carbon-Oxygen Bond Formation at Organopalladium Canty AJ, Denney MC, Skelton Centres: The Reaction of PdMe(p-Tol)(bpy) with BW, White AH Dibenzoyl Peroxide 99 DNA Binding Studies of the Tri-nuclear Platinum Anticancer Moniodis JJ, Thomas DS, Drug BBR3464: Pre-association with a 12-Mer DNA Duplex Berners-Price SJ, Hegmans A Farrell N 100 Metal-metal bonding in cubane clusters, Knottenbelt SZ, McGrady JE Cp4M4S4, M = Fe, Ru
Tuesday, 4 February 2003
11:30 am to 12:30 pm Plenary Lecture 5 co-sponsored by the Prince Philip Theatre Centre for Green Chemistry, Monash University Chair: Professor Roy Jackson 101 11:30 Designing Catalysts for Green Oxidation Technologies Professor Terrence Collins Carnegie Mellon University
12:30 pm to 2:00 pm Lunch - own arrangements
2:00 pm to 4:00 pm Supramolecular Chemistry (TP1) Prince Philip Theatre Chair: Professor Bruce Wild 102 14:00 Nanoporous Molecular Framework Materials Kepert CJ 103 14:30 Malleability of Metal-Dicyanamide Coordination Networks Batten SR, Falali, J, Harris AR, Jensen P, Kutasi AM, Moubaraki B, Murray KS, Price DJ, van der Werff PM 104 15:00 Using Flexible Multimodal Ligands to Influence Amoore JJ, Hanton LR, Spicer Coordination–Polymer Architectures MS 105 15:30 The Role of Hydrogen Bonding in Coordination Polymers Abrahams BF
2:00 pm to 4:00 pm Green and Environmental Chemistry (TG1) Old Geology Lecture Theatre 1 Chair: Associate Professor Lawrie Gahan 106 14:00 The Thiosulfate Gold Leaching Process: Importance of Spiccia L Copper Complexation and Reactivity 107 14:30 Extractants to Improve Material Balances in Metal Recovery Tasker PA, Henderson DK, Galbraith SG, Miller H, Parkin A, Plieger PG, Smith KJ, West LC 108 15:00 Metal Recovery using Supramolecular Materials Based on Davey JM, Ding J, Misoska V, Conducting Polymers Price WE, Ralph SF, Reece DA, Tsekouras G, Wallace GG 109 15.30 Polymers by Clean Technologies Berven BM, Byrne LT, Koutsantonis GA, Skelton BW, White AH
4:00 pm to 4:30 pm Afternoon Tea Architecture Atrium
4:30 pm to 6:00 pm Supramolecular Chemistry (TP2) Prince Philip Theatre Chair: Associate Professor Kevin Wainwright 110 16:30 New Bridging Heterocyclic Ligands for Use in Steel PJ Metallosupramolecular Chemistry 111 17:00 Building Network Structures with Molecular Hosts Ahmad R, Hardie MJ, Raston CL
112 17:30 The Design, Synthesis and Structure of Porphyrin Hosts Boyd PDW, Kennedy SMF, for Supramolecular Fullerene Binding Hosseini A, Sun D, Tham F, Reed CA
4:30 pm to 6:00 pm Green and Environmental Chemistry (TG2) Old Geology Lecture Lecture Theatre 1 Chair: Associate Professor Lawrie Gahan 113 15:30 Modeling the Corrosion Inhibition Film Provided by Forsyth CM, Wilson K, Behrsing Ce(salicylate)3.H2O on Mild Steel T, Konstas K, Deacon GB, Forsyth M, Brack N 114 16:30 Solving the Great Nitrate Riddle Grace MR 115 17:00 Environmental and Occupational Exposure to Codd R, Levina A, Gez S, Chromium(VI): Characterisation of Novel Lay PA Chromium(V) – Bioligand Complexes
Wednesday, 5 February 2003
9:00 am to 10:00 am Plenary Lecture 6 Prince Philip Theatre Chair: Professor Tony Wedd 116 9:00 Copper Homeostasis: A Structural Genomics Approach Professor Lucia Banci University of Florence
10:00 am to 11:30 am Poster Session (PWE) and Morning Tea Architecture Atrium 117 Studies of Group1 Metallated ß-Dinitrogen Ligands and Cole ML, Junk PC Their Synthetic Utility Toward Homo- and Heteroleptic Complexes of the Lanthanoids 118 Glutathionylcobalamin: A Biologically Important Vitamin Cregan AG, Xia L, Brasch NE B12 Derivative? 119 Characterization of Unstable Transition Metal Complexes Darwish T, Ball GE Using NMR Spectroscopy 120 Insights into the Anti-Inflammatory Mechanisms of Copper Dillon CT, Hambley TW, and Zinc Indomethacin: Why are they Less Ulcerogenic Kennedy BJ, Lay PA, Zhou Q, than the Parent Drug? Davies NM, Biffin JR, Regtop H 121 Let There Be Light - Photoinduced Schiff Base Deacon GB, Drago PR, Hambley Condensation Reactions TW, Ireland J, Mason DN 122 The Oxidation of Novel Organoplatinum(II) Anti-Cancer Drago PR, Deacon GB, Complexes Hambley TW 123 Synthesis and Coordination of a New Scorpionate Ligand – Duriska MB, Batten SR Potassium tris{3-(4-benzonitrile)-pyrazol-1-yl}hydroborate 124 Vapour Sorption and Release from Clay Nanotubules Green MER, Weeks CL, Antill SJ, Kepert CJ 125 High Resolution EXAFS and DFT of the Molybdenum Harris HH, George GN, Site of Human Sulfite Oxidase Rajagopalan KV 126 Aqueous Solution Identification of Molybdate-nucleotide Hill LMR, Young CG, George Polyanions GN, Duhme-Klair AK 127 Structural Correlation with Chemical Bonding and the Hocking RK, Hambley TW Properties of Transition Metal Complexes 128 Synthesis of Titanium Complexes of Diaminobutanediols Kam CLS, Bailey TD, for Use as 45Ti Radiopharmaceuticals Crumbie RL 129 The New Quasi-Laue Diffractometer at the Replacement Klooster W Research Reactor 130 Determination of Chromium Oxidation States in Levina A, Lay PA Coordination Compounds by X-ray Absorption Spectroscopy 131 Alkaloid Addiction: The Coordination Chemistry of Nicotine Lewis W, Steel PJ and Quinine 132 Complexation of Alkai Metal and Alkaline Earth Ions by Geue JP, Head NJ, Ward AD, Anthracene Based Fluorophores with One and Two Lincoln SF Appended Monoaza Coronand Receptors 133 Colourful and Exciting Chemistry: Electrochromism and Bernhardt PV, Macpherson BP Excited State Studies of Cyano-bridged Mixed Valence Complexes 134 Electrochemically Driven Reversible Solid State Metal Marken F, Cromie S, McKee V Exchange Processes in Polynuclear Copper Complexes 135 Electrochemically Driven Ion Exchange at Microdroplets Marken F, Hayman CM, Page with Liquid|Liquid|Solid Triple Interfaces PCB 136 Osmium-silsesquioxane as Catalyst for Dihydroxylation Pescarmona PP, Masters AF, Reactions van der Waal JC, Maschmeye T, Beattie JK 137 Preparation And Properties Of New Ruthenium Healy PC, Micallef LS, Williams Cyclopentadienyl Complexes ML 138 Switchable Cycloplatinated Ferrocenylamine Derivatives of Morgan JL, McAdam CJ, McGale Acridone, Naphthalimide and Anthraquinone E, Murray E, Robinson BH, Simpson J 139 Zinc Saccharate: A Chiral, Three Dimensional Polymer Abrahams BF, Moylan MD, Containing Two Types of Channel – the First Hydrophilic, Orchard SD, Robson R the Second Hydrophobic
Wednesday, 5 February 2003
140 Ag(I) and Pd(II) Complexes of an Ether-functionalised Nielsen DJ, Cavell KJ, Skelton Bis-(nucleophilic heterocyclic carbene) Ligand. BW, White AH 141 Interactions of Proximate Amino Acid Residues in Polyaza Plush SE, Lincoln SF, Macrocycles Wainwright KP 142 Exploration of the Reactivity of Pt(II) Toward “Activated” Canty AJ, Rodemann T, Skelton Aryl and Alkynyl Halides using Diorganoiodine(III) Reagents BW, White AH 143 Electron Transfer Reactions with Polyoxometalates Schatz M, Tregloan PA, Wedd AG 144 Alkyne Coupling Reactions Mediated by Ruthenium(0): Hill AF, Rae AD, Schultz M, Formation of Functionalised Macrocycles Willis AC 145 Linking Ferrocene to Polyaromatic Hydrocarbons via Connelly RBT, Gallagher JF, Alkene and Alkyne Spacers. Hudson RA, Jennings S, Manning AR, McAdam CJ, Robinson BH, Simpson J 146 Redox Interplay of Oxo–thio–tungsten Centres with Sproules S, Hill JP, White JM, Sulfur-donor Co-ligands George GN, Young CG 147 Photoluminescence Properties of Four-Coordinate Sweigers GF, Delfs CD, Kitto HJ, Gold(I)–Phosphine Complexes of the Types Stranger R, Wild SB, Willis AC, [Au(diphos)2]PF6 and [Au2(tetraphos)2](PF6)2 Wilson GJ 148 Multidimensional Lanthanoid Frameworks with Thiyakesan A, Kepert CJ 2,5-pyrazinedicarboxylic Acid 149 Transition Metal Cluster Compounds Containing Cookson D, Humphrey MG, Chalcogenide Ligands Lucas NT, Skelton BW, Tolhurst V-A, Turner P, White AH 150 Structural, Magnetic and Supramolecular Properties of van der Werff PM, Batten SR, Anionic Dicyanamide Coordination Polymers Jensen P, Moubaraki B, Murray KS 151 Solid State and Molecular Modelling Studies of the pH Warden AC, Warren M, Spiccia L Dependence Between Azamacrocycles and Phosphates 152 Microporous Coordination Polymers with Weeks CL, Kepert CJ 1,3,5-Benzenetricarboxylate: Effect of Ancillary Ligands and Solvent on Structure 153 Introducing the 4-Azapentalenyl Anion: a p-Bound Anwander R, Cloke FGN, Heterocyclic Anion with Potential Far Beyond Gardiner MG, Hitchcock PB, the Cyclopentadienyl Anion! Wise LE, Yates BF 154 Cationic Iridium and Rhodium Catalysts for the Synthesis Burling S, Field LD, Messerle BA, of N-Heterocycles Wren SL 155 Membrane Copper Pump Ctr1 and Downstream Proteins Xiao Z, Loughlin F, Wedd AG Atx1 and Ccc2 in Yeast: Copper Binding and Trafficking 156 Product Diversity in the Reactions of Alkynes with Young CG, Lim PJ, Akhlaghi H, Tp*W(dtc)(CO)2 Slizys D, White JM
11:30 am to 1:00 pm Stranks Award Presentations Prince Philip Theatre co-sponsored by Australian Journal of Chemistry Chair: Associate Professor Peter Tregloan 157 11:30 Complexes of Divalent and Trivalent Ruthenium Joanne Adams Incorporating Tethered Arenes 158 11:45 Stereochemical Effects on Intervalence Charge Transfer Deanna D'Alessandro in Polymetallic Supramolecular Assemblies 159 12:00 Guest-Dependent Spin Crossover in Nanoporous Gregory Halder Molecular Framework Materials 160 12:15 Fundamental Studies of Solar Energy Materials: Vibrational Sarah Howell Spectroscopy and ab initio Studies of 1,10-Phenanthroline and its Complexes. 161 12:30 The Synthesis and Study of Metal Complexes of Ligands Christopher Sumby with Tripodal Tridentate Binding Domains 162 12:45 Catalytic Gas Phase Oxidation of Methanol to Tom Waters Formaldehyde
Thursday, 6 February 2003
9:00 am to 10:00 am Plenary Lecture 7 Prince Philip Theatre Chair: Professor Trevor Hambley 163 9:00 Platinum Anticancer Agents. Structures and Targeted Professor Nicholas Farrell Biomolecules Virginia Commonwealth University
10:00 am to 11:30 am Poster Session (PTH) and Morning Tea Architecture Atrium 164 First Structurally Characterised Complexes of a Beckmann U, Brooker S, Triazolate-Containing Schiff-Base Macrocycle: Syntheses Depree CV, Ewing JD, and Properties Moubaraki B, Murray KS 165 Structural Diversity Exhibited by Lanthanide Carboxylates Behrsing T, Deacon GB, Forsyth CM, Forsyth M, Hilder M, Skelton BW, White AH 166 Synthesis of Humphreys AS, Berners-Price Bis(1,3-bis(di-2-pyridylphosphino)propane)Gold(I) SJ, Koutsantonis GA, Chloride: Potential Anti-Tumour Agent Skelton BW, White AH 167 Reversible Nitrogen Sorption into the Nanoporous Bevitt JJ, Halder GJ, Kepert KJ Molecular Framework [Co(4,4'-bipyridine)1.5(NO3)2] by Single Crystal X-ray Diffraction 168 XAFS Analysis of Transiently Stable Bondin MI, Foran G, Best SP Electrogenerated Products 169 Molecular Rectangles from Metallomacrocycles Caradoc-Davies PL, Hanton LR
170 Anomalous Thermal Expansion Behaviour in Coordination Chapman KW, Goodwin AL, Framework Materials Kepert CJ 171 Lanthanoid Complexes with 'Non-Coordinating' Deacon GB, Evans DJ, Forsyth Anions - From Discrete Ions to Molecular Complexes CM, Junk PC 172 Solvent Extraction of Metal Ions Using Supramolecular Gasperov V, Lindoy LF, Gloe K, Assemblies Wichmann K, Mahinay M, Tasker PA 173 Solid State Optophysical and Structural Properties of Deacon GB, Ghiggino K, Hilder Lanthanoid Carboxylates M, Junk PC, Kynast UH 174 New Linkers for Bis-porphyrins Designed to Host Hosseini A, Boyd PDW, Fullerenes Kennedy SMF
175 Cubane-related Building Blocks from the Decompostion of Hudson TA, Abrahams BF, Ene-diols Robson R 176 Robust Porosity and Ferrimagnetism in a Pillared-Layered Hughes S, Kepert CJ, Kurmoo Material M, Kumagai H, 177 Tractable Autocatalytic Substitution Processes Jackson WG, Goodyear K, McKeon JA, Freasier B, Wells K 178 Structural Characterization of the Tungsten Tricarbonyl Malarek MS, Logan BA, White + Cationic Complex, [Tp*W(CO)3(MeCN)] , an Intermediate JM, Young CG in a Host of Organometallic Chemistry 179 Possible Fluorescent Switches From 4-Substituted McAdam CJ, Manning AR, Naphthalimides Robinson BH, Simpson J 180 125Te MAS NMR and X-Ray Diffraction Studies of Beckmann J, Dakternieks D, Diorganotellurium Dichlorides, R2TeCl2 and Duthie A Smith NA Diorganotellurium Oxides, R2TeO (R = Ph, p-Me-C6H4, p-MeO-C6H4). 181 Reverse Bola-Amphiphiles Incorporating ‘Cage’ Complexes Harrowfield JM, Koutsantonis GA, Nealon GL, Skelton BW, White AH 182 Carbonyl-carboxylato-ruthenium Complexes Incorporating Pearson P, Kepert CM, Deacon Diimine Ligands GB, Spiccia L, Warden AC, Skelton, BW, White, AH 183 DNA Binding of Enantiomerically Pure Methylated Peberdy J, Rodger A, Hannon Bimetallo Triple Helicates MJ, Khalid S, Ruedegger V, Childs LJ, Meistermann I
184 Organometallic MnL(CO)3Br Complexes of Bidentate Skelton BW, Tolhurst VA, Pyridyl/chalcogenoether Ligands Williams AM, Wilson AJ, White AH
Thursday, 6 February 2003
185 Complexes Facilitating the Heck Reaction Involving Internal Skelton BW, Tolhurst VA Olefins: Pd(II) and Pt(II) Complexes Containing the Mixed Williams AM, Wilson AJ, White Donor Ligand 2-(RECH2)C5H3N AH, Yates BF 186 Highly Localised Charges Control Electrostriction. Redox Bajaj HC, Tregloan PA, van Reaction Volumes for Mononuclear and Bridged Eldik R Ru Complexes 187 Scorpionates: poly(methimazolyl) Borate Chemistry of Edwards AJ, Hill AF, Foreman Divalent Ruthenium MRS, Tshabang N, White AJP, Williams DJ, Willis AC 188 Isocyanide Substitution and Core Expansion at Usher AJ, Lucas NT, Dalton GT, Molybdenum – Iridium Mixed-Metal Clusters Humphrey MG, Willis AC 189 Metal Complex Catalysed C-S Bond Formation Messerle BA, Turner P, Vuong K 190 Investigation of Rotamers About the Pt-N7 Bonds in Bulky Waller MP, Bulluss GH, Hambley [Pt(d(GpG))(diamine)] Complexes TW 191 Alkali Metal Inclusion Capabilities as a Destabilising Effect Gardiner MG, Skelton BW, Wang in Macrocyclic Organolanthanide Complexes Leading to J, White AH Complete Metal Exchange 192 Inorganic Asymmetric Synthesis: Stereoselective Warr RJ, Wild SB Synthesis of Two-Bladed Propeller Octahedral Metal Complexes 193 Compounds of Nickel(II) with Cook DF, Curtis NF, Gladkikh 5,12-Dimethyl-7,14-diphenyl- OP, Rickard CEF, Waters JM, 1,4,8,11-tetraazacyclotetradecane Weatherburn DC 194 Targeting DNA with Macrocycle-Intercalator Complexes Whan RM, Ellis LT, Hambley TW
195 Synthesis, Structure and Magnetism of New Mixed-valent Wittick L, Batten SR, Berry KJ, Manganese Clusters Moubaraki B, Murray KS, Price DJ, Spiccia L 196 New Stannyl Complexes of Osmium Through Nucleophilic Lu GL, Rickard CEF, Roper WR, Displacement of the Iodo Groups on Iodostannyl Ligands Whittell GR, Wright JL
197 Structural Characterisation of a Novel Mo16 Hill LMR, Abrahams BF, Polyoxomolybdate Containing an Mo4O4 Cubane Young CG 198 Synthesis and Reactivity of Cationic Organotin species Beckmann J, Dakternieks D Featuring Sn-O-P Linkages Duthie A, Mitchell C 199 From Organometallic Rigid-Rods Towards Organometallic Hunter A, D, Zeller M, Lazich E, NanoStars: Electronically Bridged Nanostructured Materials Perrine C, Updegraff J, DiMuzio by Design S, McSparrin L, Takas N, Snyder F, Wilcox R, Walther L, Peace M
11:30 am to 12:30 pm Burrows Lecture Prince Philip Theatre Chair: Professor Richard Keene 200 11:30 Molecule Based Magnets; From Large Clusters to Professor Keith Murray Spin-crossover to Extended Networks Monash University
12:30 am to 1:00 pm Divisional Meeting Prince Philip Theatre Chair: Professor Richard Keene
1:00 pm to 2:00 am Lunch - own arrangements
Thursday, 6 February 2003
2:00 pm to 4:00 pm Recent Advances in Techniques Prince Philip Theatre and their Application (RP1) Chair: Associate Professor Charles Young 201 14:00 X-ray Absorption Spectroscopy in Inorganic Biochemistry George GN, Harris HH, Gailer J, Pickering IJ 202 15:00 X-Ray Microprobe Analysis of the Cellular Uptake and Dillon CT, Kennedy BJ, Lay PA, Metabolism of Carcinogenic and Genotoxic Chromium Lai B, Cai Z, Stampfl APJ, Ilinski Compounds P, Legnini DG, Maser J, Rodrigues W, Shea-McCarthy G, Cholewa M
203 15:30 High Resolution Powder Synchrotron Diffraction Studies Kennedy BJ of Layered Bismuth Oxides
2:00 pm to 4:00 pm Towards Inorganic Drugs (RG1) Old Geology Lecture Theatre 1 Chair: Associate Professor Trevor Appleton
204 14:00 Synthesis and DNA-Binding Properties of Platinum(II) Todd JA, Woodhouse SL, Complexes Containing 1,2- and Rendina LM 1,7-Dicarba-closo-dodecaborane(12) 205 14:30 Developing Pt(IV) Anticancer Drugs Resistant to Davies MS, Battle AR, Hambley Reduction via Ligand Chelation TW 206 15:00 Dinuclear Ruthenium Complexes as Sequence- and Collins JG, Foley FM, Keene FR, Structure-Selective Binding Agents for DNA Patterson BT, Richards D, 207 15:30 New Insight into the Stepwise Formation of Platinum-DNA Berners-Price SJ, Davies MS, Crosslinks from [1H,15N] NMR Spectroscopy Thomas DS, Hegmans A, Cox JW, Farrell N
4:00 pm to 4:30 pm Afternoon Tea Architecture Atrium
4:30 pm to 6:00 pm Recent Advances in Techniques Prince Philip Theatre and their Application (RP2) Chair: Associate Professor Sally Brooker 208 16:30 Structure and Exchange in Photo-Generated, Short-Lived Ball GE, Geftakis S, Lawes DJ, Alkane Complexes Darwish T 209 17:00 Mechanistic Insight Gained from Volume Profile Analysis van Eldik R 210 17:30 Using DFT to Design Metal Complexes which Optimize the Christian G, Driver J, Petrie S, Activation and Cleavage of Small Multiply-Bonded Molecules Stranger R
4:30 pm to 6:00 pm Ligand Design (RG2) Old Geology Lecture Theatre 1 Chair: Associate Professor David McFadyen 211 16:30 Fluorescence of the Intracellular Zinc(II) Probe Zinquin A Hendrickson KM, Geue JP, in Ternary Zinc(II) Complexes Wyness O, Lincoln SF, Ward AD 212 17:00 Chromium Schiff Base Complexes in Olefin Polymerization Jones DJ, Gibson VC, Green Catalysis: Synthesis of a Ligand and Metal Complex Library SM, Maddox PJ, for High Throughput Screening 213 17:30 New Catalysts and Tandem Reactions: Synthesising Burling S, Field LD, Messerle Products with C-X Bonds BA, Wren S, Vuong K
7:30 pm to 11:30 pm Conference Dinner San Remo Ballroom
1 Molecular Self-assembly through Coordination: From Square to Polyhedra to "Cavity-directed Synthesis" Makoto Fujita Department of Applied Chemistry, School of Engineering, The University of Tokyo Bunkyo-ku, Tokyo 113-8656, Japan
Molecular self-assembly has recently undergone on explosive development, making possible the synthesis of many fascinating and complex structures using only relatively simple procedures. Over the last decade, we have been showing that the simple combination of palladium's square planer geometry (a 90 degree coordination angle) with pyridine-based bridging ligands gives rise to the quantitative self-assembly of nano-sized, discrete organic frameworks. Representative examples include square molecules, linked-ring molecules, cages, tubes, and capsules that are self- assembled from simple and small components. In the present paper, we will focus on the metal- coordinated approach to polyhedra via "molecular paneling".1,2
We will also discuss the chemistry of molecular interior. Molecular capsules provide isolated microspace within the molecules where otherwise labile species are protected and can be considerably stabilized. The labile molecules are most effectively trapped in the capsules if they are prepared in situ from smaller components coming through small openings of the capsules. We show cyclic trimers of silanetriols (c-[RSi(OH)2]3), which is otherwise labile and quite apt to oligomerize, can be prepared quantitatively and observed as a stable form if the condensation of RSi(OH)3 is carried out within the cavity of self-assembled coordination cage (See Figure 1).3 Highly regio- and stereoselective photodimerization of olefins will be also discussed.4 Fig. 1. The cover page of Aust. J. Chem., Vol.55, No. 10.
[1] Fujita, M. Chem. Soc. Rev. 1998, 27, 417. [2] Takeda, N., Umemoto, K., Yamaguchi, K., Fujita, M. Nature 1999, 398, 794. [3] M. Yoshizawa, T. Kusukawa,, M. Fujita, and K. Yamaguchi, J. Am. Chem. Soc., 2000, 122, 6311. [4] M. Yoshizawa, Y. Takeyama, T. Kusukawa, and M. Fujita, Angew. Chem. Int. Ed., 2000, 41, 1347.
IC-03 February 2-6, 2003 Melbourne 2 BIFUNCTIONAL LIGANDS IN THE SYNTHESIS OF MONO- AND OLIGONUCLEAR TRANSITION METAL COMPLEXES
Ulrike Helmstedt, Thomas Höcher, Olaf Kühl, Peter Lönnecke, Felicite Majoumo, Rene Sommer, Anke Sterzik, Barbara Wenzel, and Evamarie Hey-Hawkins Universität Leipzig, Institut für Anorganische Chemie, Johannisallee 29, D-04103 Leipzig, Germany. [email protected]
Early/late bridged transition metal complexes are of interest as the metal centres may show cooperative synergetic reactivity. We are interested in the use of substituted (bifunctional) ligands H–X–bridge–Y–H (or R) (where X ¹ Y = O, S, PR’, NR’, bridge = alkyl, aryl) and phosphinoalkylcyclopentadienides.[1] While suitable amino- and thioalcohols are commercially available, synthetic routes to the corresponding phosphinoalcohols, -thioalcohols, -amines and phosphinoalkylcyclopentadienides had to be developed. So far, we have synthesised several chiral and achiral bifunctional ligands, such as HO-bridge-PPh2, HO-bridge-PHR, HS-bridge- PHR, HNR-bridge-PR2, and Li[(C5H4)CMe2PHR] (R = alkyl, aryl). With phosphinoamine ligands with a P-N bond, unusal homometallic complexes are obtained, such as the zwitterionic zinc complex [Zn(C3H7)(1-NPMes2-2-NPHMes2-C6H4)] (1) and the nickel(I) complex 2. First, the early transition metal M is introduced, and complexes such as [TpZr(OCH2PPh2)3], [Cp2Zr(SCH2CH2PHR)2] (R = aryl), [Cp°2Zr(O2CCH2SH)2] (Cp° = C5EtMe4), [Fe{(h- [1,2,3] C5H4)CMe2PHR}2] (R = Ph, Mes) etc. are obtained. Some of these complexes are suitable precursors for the introduction of a second metal, e.g. [TpZr(m-OCH2PPh2)3Mo(CO)3] (Tp = trispyrazolylborato), the trinuclear Zr-Au complex 3, the tetranuclear Zr-Ni complex 4 or [Fe{(h-C5H4)CMe2PHPh(Cp*TaCl4)}2]. Catalytic studies are presented.
(1) (2) (3) (4)
[1] T. Koch, E. Hey-Hawkins, Polyhedron 1999, 18, 2113. T. Koch, S. Blaurock, F. B. Somoza Jr., A. Voigt, R. Kirmse, E. Hey-Hawkins, Organometallics 2000, 19, 2556. T. Höcher, S. Blaurock, E. Hey-Hawkins, Eur. J. Inorg. Chem. 2002, 1174. R. Sommer, P. Lönnecke, P. K. Baker, E. Hey-Hawkins, Inorg. Chem. Comm. 2002, 5, 115. [2] T. Koch, S. Blaurock, E. Hey-Hawkins, Europ. J. Inorg. Chem. 2000, 2167. S. Chaudhury, S. Blaurock, E. Hey-Hawkins, ibid. 2001, 2587. [3] T. Koch, S. Blaurock, E. Hey-Hawkins, M. Galan-Fereres, D. Plat, M. Eisen, J. Organomet. Chem. 2000, 595, 126. O. Kühl, T. Koch, F. Somoza Jr., P. C. Junk, E. Hey-Hawkins, D. Plat, M. Eisen, J. Organomet. Chem. 2000, 604, 116. O. Kühl, S. Blaurock, J. Sieler, E. Hey- Hawkins, Polyhedron 2001, 20, 2171.
IC-03 February 2-6, 2003 Melbourne 3 Carbonate-Based Coordination Polymers
Brendan F. Abrahams, Adrian Hawley, Marissa Haywood, Richard Robson and Damian A. Slizys School of Chemistry, University of Melbourne, 3010, Victoria, Australia
Despite the fact that the carbonate ion has a long and well established history in chemistry we believe that there are rich unexplored areas relating to the use of this anion as a building block in the construction of novel network materials.
+ We have found that the guanidinium ion, C(NH2)3 , can act as a useful templating cation in the construction of novel metal carbonate anionic networks. Through appropriate choices of co-cations we are able to encourage the formation of new, highly symmetrical structures possessing the same topology as the sodalite net.
2- 2+ 2+ 2+ 2+ 2+ 2+ We report the cubic structures of [M(CO3)2 ]n (M = Mg , Fe , Co , Ni , Cu , Zn and Cd2+) which all possess a robust, aesthetically appealing network containing large voids. The structural influences imposed by the coordination geometries of the metals, the templating guanidinium cations and co-cations are examined.
IC-03 February 2-6, 2003 Melbourne 4 Complexes of Divalent and Trivalent Ruthenium Incorporating Tethered Arenes
Joanne R. Adams,a Martin A. Bennetta and L. J. Yellowleesb. a Research School of Chemistry, Australian National University, Canberra ACT 0200, Australia. b Department of Chemistry, Joseph Black Building, West Mains Road, Edinburgh EH9 3JJ, United Kingdom. [email protected]
The tethered arene complexes 1-8, containing either two or three linking groups in the strap, have been synthesised from the labile methyl o-toluate complex [h6-(1,2- MeC6H4CO2Me)RuCl2]2 via mononuclear P-donor adducts which do not usually need to be isolated [1]. The complexes 1, 3, 5, 6, 7 and 8 have been structurally characterised by X-ray crystallography. Complexes 2, 4 and 7 have been reported independently [2]-[4]. The p-cymene 6 complex [h -(1,4-MeC6H4CHMe2)RuCl2]2 can only be used as a precursor to the tethered complexes if the phosphorus atom carries bulky substituents such as cyclohexyl; these reactions are slower than those starting from the ester complex.
R' R R SiMe2 Ru Ru Cl R' R Cl P Ru P Cl R Cl Cl Ph 2 Cl P 2 Ph2 1 R = Me 6 R = Me, R’ = H 8 2 R = Ph 7 R = R’ = Me 3 R = i-Pr 4 R = Cy 5 R = t-Bu
As arene-ruthenium(III) species are postulated to be involved as intermediates in catalytic C-H 6 bond activation processes based on [RuMe2(h -C6Me6)(PR3)] [5], the redox behaviour of complexes 1-8 and some non-tethered counterparts has been compared. Both series show reversible or quasi-reversible electrochemical behaviour. The resulting Ru(III) species were 6 detected by spectroelectrochemistry, and, in the cases of 3, 7 and [RuCl2(h -C6Me6)(PPh3)] (9), by esr. Chemical oxidation of 7 and 9 with [N(C6H4-Br-4)3]SbCl6 gave rise to the isolable, first + - + - structurally characterised arene-ruthenium(III) complexes [7] [SbCl6] and [9] [SbCl6] [6]. The tethered Ru(III) complexes, generated either by electrochemical or chemical oxidation, were more stable than their non-tethered counterparts.
[1] M. A. Bennett, A. J. Edwards, J. R. Harper, T. Khimyak and A. C. Willis, J. Organomet. Chem., 2001, 629, 7. (Joanne R. Harper is now Joanne R. Adams). [2] P. D. Smith and A. H. Wright, J. Organomet. Chem., 1998, 559, 141. [3] K. Y. Ghebreyessus and J. H. Nelson, Organometallics, 2000, 19, 3387. [4] A. Fürstner, M. Liebel, C. W. Lehmann, M. Picquet, R. Kunz, C. Bruneau, D. Touchard and P. H. Dixneuf, Chem. Eur. J., 2000, 6, 1847. [5] A. Ceccanti, P. Diversi, G. Ingrosso, F. Laschi, A. Lucherini, S. Magagna and P. Zanello, J. Organomet. Chem., 1996, 526, 251. 6 [6] [RuCl3(h -C6Me6)] has been isolated but was not structurally characterised; U. Kölle, R. Görissen and A. Hörnig, Inorg. Chim. Acta, 1994, 218, 33.
IC-03 February 2-6, 2003 Melbourne 5 Reactivity Studies of 1-Benzoyl-3-(2,4,6-tri-tert-butylphenyl)thiourea and Related Ligands
Eric W. Ainscough,a Andrew M. Brodie,a Anthony K. Burrell,a I.K.G. Indira Chandrasenaa and Graham A. Bowmakerb a Institute of Fundamental Sciences – Chemistry, Massey University, Palmerston North, New Zealand b Chemistry Department, University of Auckland, Auckland [email protected]
Ligands such as 1-(benzoyl-3-(2,4,6-tri-tert-butylphenyl)thiourea (BztBPtuH) and 1-benzoyl- 3(2,6-diisopropylphenyl)thiourea (BziPPtuH) have been synthesised and their reactivities toward copper and mercury salts and halogens studied. With Cu(acetate)2, the ligands form possible t i square-planar compounds of the type [Cu(L2)] (L = Bz BPtu or Bz PPtu) where L exhibits an anionic, bidentate O, S binding mode. However in compounds of the type [Cu(BztBPtuH)Cl], t t [Cu(Bz BPtuH)4]PF6 and [Cu(Bz BPtuH)2Cl2] the neutral ligands bind through the sulfur donor atoms only.
t-Bu t-Bu i-Pr O S O S
N N N N H H t-Bu H H i-Pr
BztBPtuH BziPPtuH
t With HgCl2, pseudo-tetrahedral compounds of the type [Hg(Bz BPtu)2Cl2] are isolated from ethanol, whereas with Hg(acetate)2 in the same solvent, the formation of a transient yellow species is followed by rapid precipitation of HgS in quantitative yield. Upon desulfurization, acetic acid is also produced along with new organic derivatives of the type C6H5CON=C(OX)NHR (e.g. X = C2H5, R = 2,4,6-tri-tert-butylphenyl). This organic derivative t is also obtained by reaction of sodium acetate with [Hg(Bz BPtuH)2Cl2] or by the reaction of silver acetate with BztBPtuH, both reactions performed in ethanol. A possible mechanism for these reactions will be outlined. When CH2Cl2 is used as solvent different products are formed and these will be discussed.
t t The soft ligand Bz BPtuH reacts with I2 to give the adduct [(Bz BPtuH)I2] and a single crystal X-ray structure shows the molecule to have a long I–I bond length of 2.853 Å. The molecule displays a n(I–I) stretching frequency at 138 and 149 cm–1 in the IR. These data confirm the weakening but not the complete disruption of the I–I bond upon coordination to the S atom. The Br2 adduct is unstable with respect to oxidation of the ligand and the nature of this product will i be discussed. The Br2 adduct of Bz PPtuH is metastable but its single crystal X-ray structure will be discussed.
IC-03 February 2-6, 2003 Melbourne 6 195mPt Radiolabelling of Cisplatin: An Improved Synthetic Pathway Suzanne V. Smith, Nadine Di Bartolo, Rebecca Alderden, and Mark Alexander, Vu Nygen Tim Jackson, and Vahan Papazian Radiopharmaceuticals Division, ANSTO, PMB 1 Menai, New South Wales, Australia. [email protected] [email protected] Many patients, when diagnosed with head and neck cancer, will initially be treated with cisplatin. It is estimated that this treatment is effective in about 30% of cases [1]. However, all patients that are administered with cisplatin will suffer adverse side effects such as nausea, vomiting, nephrotoxicity, neurotoxicity, and myelotoxicity. It is theorised that this disparity exists because cisplatin is not a specific drug, and only localises at the tumour site in some cases. Therefore, there exists a need to assess individual patients and their metabolic ability to localise cisplatin. Radiolabelled cisplatin should enable non-invasive imaging of the cisplatin tumour uptake of individual patients. Of the platinum isotopes available, 195mPt exhibits properties that are most suitable for radiolabelling purposes.
Traditionally, the synthesis of 195mPt cisplatin has been a time-intensive procedure. The original synthetic pathway to 195mPt cisplatin could exceed 8 hours and is unreliable [2]. This is unsuitable for the restrictive time frame imposed by working with radioactivity. The current work at ANSTO has optimised this pathway to approximately two hours. This patented process is also applicable for other Pt(II) and Pt(IV) complexes. It is envisaged that this chemistry will allow the effectiveness of Pt-based chemotherapeutics to be assessed on a patient-by-patient basis through the use of gamma imaging.
[1] Muhyi Al-Sarraf, Thomas F. Pajak, Roger W. Byhardt, Jonathan J. Beitler, Merle M. Salter and Jay S. Cooper, Int. J. Radiation Oncology Biol. Phys., 1997, 37(4), 777-782..
[2] Christopher M. Riley and Larry A. Sternson, Anal. Profiles Drug Substances, 1985, 14, 77- 105.
[3] Suzanne V Smith, Methods of Synthesis and Use of Radiolabelled Platinum Chemotherapeutic Agents. WO 01/70755
IC-03 February 2-6, 2003 Melbourne 7 Lumen loading of halloysite nanotubes Sarah J. Antill, Malcolm E. R. Green and Cameron J. Kepert School of Chemistry, University of Sydney, 2006, New South Wales, Australia
The 1:1 phyllosilicate clay halloysite, a hydrated polymorph of kaolinite, often occurs in a tubular morphology. Internal diameters of the tubes are in the order of tens of nanometres, with aspect ratios frequently exceeding 1000. Halloysite nanotubes require less technology to produce than carbon nanotubes (CNTs), and thus present a cheaper and simpler alternative to CNTs in applications where the geometry of the tube is important, for example in confining the growth of encapsulated crystals [1] or as templates for nanowires [2]. The differences between external and internal surfaces of the clay tubes also offers scope for chemical control of the preferential internal (rather than external) loading of desired components. The hydroxyl sites on the internal surface open opportunities for the use of milder reaction conditions than those usually necessary for loading of CNTs.
Design of a protocol for filling halloysite tubes is the first step in the development of these potential applications. CNT filling techniques cannot be directly applied to halloysite tubes. The difference in size (the internal diameter of halloysite tubes are often larger than those of CNTs) discourages capillary filling. Wetting of the internal surfaces of the two types of tube requires different surface tension criteria for the wetting liquid and the usual CNT surface tension cutoff of <100-200mN/m cannot be directly applied. However, in the present study, partial and complete lumen loading of halloysite nanotubes has been achieved (figure 1) with a range of compounds using two modified methods analogous to those used for filling Figure 1 Halloysite tube after filling using iron CNTs. nitrate and cobalt nitrate as precursor salts.
[1]J. Sloan, A.I. Kirkland, J.L. Hutchison, and M.L.H. Green, Chem. Commun, 2002, 1319. [2]C.Pham-Huu, N.Keller, C.Estournès, G.Ehret, and M.J.Ledoux, Chem. Commun, 2002, 1882.
IC-03 February 2-6, 2003 Melbourne 8 Differences in Ligand Donor Preferences Between Palladium(II) and Platinum(II) in Reactions with S-Methylglutathione
Trevor G. Appleton, Huy N. Hoang, and Ashley Tronoff Centre for Metals in Biology, Chemistry Department, the University of Queensland, Brisbane, 4072, Qld. Australia
Palladium(II) and platinum(II) usually have very similar chemistry, apart from the well- known higher lability of palladium compounds compared with platinum analogues. Both are regarded as “soft” metal ions, with, usually, a preference for sulfur donor ligands over 2+ oxygen donors. However, in the reactions of [M(en)(H2O)2] (M = Pt, Pd; en = 1,2- diaminoethane) with S-methylglutathione (1), used as a model tripeptide, there are major differences between the two metal ions. O O + NH3CH(CH2)2CNHCHCNHCH2CO2H
CO - CH SMe 2 2 1 Reactions have been monitored by multinuclear NMR (1H, 13C, 195Pt, and 15N, using 15N- labelled ethylenediamine) and ES-MS. The major product in the reaction of 2+ [Pt(en)(H2O)2] with 1 in weakly acidic solution is a N,S-chelate complex, 2, while the 2+ major product in the reaction of [Pd(en)(H2O)2] with 1 under similar conditions is the N,O-chelate complex 3, with isomers due to slow inversion at sulfur, and slow rotation about the peptide bond involving the bound N-atom.
CO2
O (CH2)2CHNH3 + O H2 O O N N H NHCH CO H 2 H2 + 2 2 N Pd N (CH2)2CNHCHCNHCH2CO2H
N S. Pd . CH2SMe H2 Me N O O H2 2 3 The N,O-chelate 3 is clearly thermodynamically preferred over N,S-chelates for palladium, although some species containing sulfur-bound ligand are present in smaller proportions. The N,S-species 2 is kinetically preferred for platinum. The complex interplay between kinetic and thermodynamic effects which determine the subsequent reactions for both metal ions will be discussed.
IC-03 February 2-6, 2003 Melbourne 9
Direct Evidence for CN- Binding to the Nitrogenase Cofactor: New Redox States and New Chemistry Kylie Vincenta, Saad Ibrahimb, Shirley Fairhurstb, Carol Gormalb, Barry Smithb, Chris Pickettb and Stephen Besta a School of Chemistry, University of Melbourne 3010, Victoria, Australia. b Department of Biological Chemistry, The John Innes Centre, Research Park, Colney, Norwich, UK NR4 7UH. [email protected] The recent redetermination of the structure of the nitrogenase enzyme, leading to the discovery of an interstitial light atom in the centre of the iron molybdenum cofactor (FeMoco) [1], together with the re-evaluation of the oxidation states of the metal atoms that comprise FeMoco [2] have cast important new light on the chemistry at the heart of biological nitrogen fixation. Now a structurally robust cluster must be considered as the site of substrate binding and reduction. The effect of co-ordination of p-acid ligands on the redox chemistry of FeMoco is characterised by a shift of the reduction potentials to markedly less negative values [2]. These results suggest that the electronic structure of FeMoco is best described as a set of strongly interacting “core” iron atoms (possibly with electronic communication mediated by the interstitial atom) and the molybdenum centre weakly interacting with the core [2]. The addition of CN- to a solution of FeMoco:SPh in NMF results in a dramatic change in the electrochemistry with the replacement of the normal FeMoco response by two well-defined waves at mildly negative potentials (Figure 1). The chemistry associated with these redox processes has been delineated by a combination of electrochemistry, IR spectro-electrochemistry and EPR spectroscopy. The influence of CN- binding on the chemistry of the cluster is examined by consideration of cooperative binding of CO and CN-. Whereas binding of CO to FeMoco requires reduction beyond the semi-reduced level [3], in the presence of CN-, CO binding to FeMoco Figure 1. Voltammetry of FeMoco:SPh occurs at the oxidised level. in NMF with the addition of [NEt4][CN].
[1] Einsle, O.; Tezcan, F. A.; Andrade, S. L. A.; Schid, B.; Yoshida, M.; Howard, J. B.; Rees, D. C. Science 2002, 169, 1696. [2] Pickett, C. J.; Vincent, K. A.; Ibrahim, S., K.; Gormal, C. A.; Smith, B. E.; Best, S. P. Chem. Eur. J. 2003, 9, in the press. [3] Ibrahim, S. K.; Vincent, K.; Gormal, C. A.; Smith, B. E.; Best, S. P.; Pickett, C. J. J. Chem. Soc., Chem. Commun. 1999, 1019-1020.
IC-03 February 2-6, 2003 Melbourne 10 An Homologous Series of Metal Complexes: Co(III) Carbonato and Bicarbonato Complexes Containing Tripodal Pyridine Ligands Paul M. Jaffray, Charles R. Clark and Allan G. Blackman Department of Chemistry, University of Otago, P.O.Box 56, Dunedin, New Zealand. [email protected] Co(III) complexes containing the tetradentate tripodal pyridine ligands tpa, pmea, pmap and tepa - - (Figure 1) have been prepared. Carbonato chelate complexes [Co(N4)O2CO]X (X = ClO4 , PF6 )
of each ligand were prepared by oxidation of an aqueous Co(II) salt with PbO2 in the presence of
the free base ligand and NaHCO3, or treatment of Na3[Co(O2CO)3] with the ligand hydrobromide salt in aqueous solution. Despite the fact that all four complexes contain identical ligand donor atom sets and differ only in the number of six-membered chelate rings within each
complex, they display very different colours, ranging from yellow-orange [Co(tpa)O2CO]PF6 to
purple [Co(tepa)O2CO]ClO4. UV/vis studies in both the solid state and in aqueous solution show
a systematic shift in ?max to longer wavelengths and a concomitant decrease in e as the number of six-membered chelate rings is increased. Crystal structures of the four complexes were obtained, and these show that the average Co-N bond length increases by approximately 0.03 Å for each
six-membered ring introduced into the system. [Co(pmea)O2CO]ClO4 exhibits fluxional behaviour, as evidenced by VT 1H NMR spectroscopy, and this is ascribed to a process involving the single six-membered chelate ring. Curiously, no fluxionality is observed in the other complexes in the series.
The carbonato complexes are extraordinarily resistant to acid hydrolysis, showing minimal changes in their UV/vis spectra over periods of hours in 6 M HCl, and this allows easy isolation of the chelated bicarbonato species. Crystal structures of these rare complexes will be presented.
N N N N N N
N N
tpa pmea
N N N N N N
N
N pmap tepa
Figure 1: Structures of the tripodal pyridine ligands.
IC-03 February 2-6, 2003 Melbourne 11
Fe2(pdt)(CO)6, a Model of the CO Inhibited {2Fe2S} Subsite of the Hydrogenase H-Cluster? Stacey J. Borg,a, Mathieu Razavet,b Christopher J. Pickettb and Stephen P. Besta a School of Chemistry, University of Melbourne 3010, Victoria, Australia. b Department of Biological Chemistry, The John Innes Centre, Research Park, Colney, Norwich, UK NR4 7UH. [email protected]
The topological similarity of the classical Fe2(m-SR)2(CO)6 compounds first prepared by Reihlen [1] and the diiron subsite of the H-cluster of the all-iron hydrogenase enzyme has led to their consideration as zeroth-level models of the biological system. A key aspect of the chemistry of the hydrogenase H-cluster is the redox state dependence of the mode of CO coordination, with only terminally-bound CO evident for the reduced form of the enzyme but CO bridged forms obtained on oxidation.[2] Despite the considerable 1.5 progress made in the isolation and 1.0 characterisation of close structural O + S + S + O + 0.5 analogues of the {2Fe2S} H-cluster subsite, Fe4- Fe4- 0.0 O + + dithiolate-bridged diiron compounds with O + O + O bridging CO groups have proved to be a) Fe2(m -pdt)(CO)6, 1 - elusive.
O + + S + S + O Studies of the simple hexacarbonyl Fe 4- Fe4-
+ + Absorbance O + + O complex, Fe2(m-pdt)(CO)6 (pdt = O O - propanedithiolate) have shown that it b) [Fe2(m -pdt)(CO)6] , 1A undergoes two successive one electron - reduction steps to generate highly reactive, O + S + S + short lived intermediate species. Using a H Fe 4- Fe 4- variety of spectroscopic techniques (CV, + O O + O + O + IR, NMR, ESI-MS, UV-Vis.) , these O intermediate species have been shown to - c) [HFe2(m -pdt)(CO)5(m -CO)] , 1B undergo CO dissociation, CO 2100 2000 1900 1800 1700 rearrangement and protonation reactions, -1 Wavenumber / cm yielding species which contain bridging CO and hydrido moieties. Furthermore, these carbonyl compounds are shown to be effective electrocatalysts for the reduction of protons and undergo H/D exchange with D2O. Figure 1. IR spectra and proposed structures for a) Fe2(m-pdt)(CO) - - b) [Fe2(m-pdt)(CO)6] , 1A, and c) [HFe2(m-pdt)(CO)5( m-CO)] ,
[1] H. Reihlen,A. von Friedolsheim and W. Oswald, J. Leibigs. Ann. Chem., 1928, 465, 72. [2] Y. Nicolet, A.L. de Lacey, X. Vernède, V.M. Fernandez, E.C. Hatchikian and J. C. Fontecilla-Camps, J. Am. Chem. Soc., 2001, 123, 1596.
IC-03 February 2-6, 2003 Melbourne 12 Photoinduced Electron Transfer in Metal Ion Activated Fluorescent Molecular Receptors.
Adam J. Bradbury,a Rebecca Campbell,a Kevin P. Wainwrighta and Stephen F. Lincolnb a School of Chemistry Physics and Earth Sciences, Flinders University, GPO Box 2100 Adelaide 5001, South Australia, Australia. b Department of Chemistry,University of Adelaide, Adelaide, 5005, South Australia, Australia. [email protected]
Molecules containing a basket-like cavity, such as cyclodextrins and calixarenes, are capable of hosting small molecules within their cavities, and hence acting as molecular receptors. More recently a number of ligands derived from tetraazacyclododecane, cyclen, which assume an appropriate conformation upon complexation to a metal ion, have been synthesised.[1] To achieve sensor capabilities for these receptors, whereby the ingress of a small molecule is signalled, a potential fluorophore needs to be attached to their structure. As a first step towards this we have synthesised the molecule antac-12, shown below, which can subsequently be developed into a complete molecular receptor in the way shown. Upon metal ion complexation molecules of this type adopt a conformation in which there is a large hydrophobic cavity defined by the four aromatic moieties. Previously these have been shown to be effective at sequestering aromatic anions.[1]
O N N O HO H O H N N N N
N N N N H H
antac-12 OH HO O O
Figure 1. Antac-12 can be developed into a complete molecular receptor by the addition of aromatic pendant arms.
Derivatives of antac-12 will utilise the interplay between fluorescence and the non-radiative deactivation pathway, photoinduced electron transfer, as the signalling mechanism for molecular inclusion.
[1] C.B. Smith, A.K.W. Stephens, K.S. Wallwork, S.F. Lincoln, M.R. Taylor, and K.P. Wainwright, Inorg. Chem., 2002, 41, 1093.
IC-03 February 2-6, 2003 Melbourne 13 DI- AND POLY-NUCLEAR COBALT(II) PYRIDAZINE COMPLEXES AS POTENTIAL NANO-COMPONENTS Sally Brooker,*,a Duncan J. de Geest,a Robert J. Kelly,a Paul G. Plieger,a Boujemaa Moubarakib and Keith S. Murrayb aDepartment of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand, bDepartment of Chemistry, Monash University, Clayton, Australia. [email protected] The preparation of molecular materials which could have nano-technological applications is an area of intense interest. In order to produce molecules which can act as switches, detectors or memory devices the property of bistability is required. Classic examples of bistability are provided by spin crossover compounds in which the transition from low- to high-spin is accompanied by a measurable change in magnetism and often also in colour.
We are studying complexes of chelating ligands based on 3,6-diformylpyridazine, and related heterocycles. To date, very few pyridazine- or phthalazine-bridged dicobalt(II) complexes have been studied, and all of these have contained high-spin cobalt(II) ions throughout the temperature ranges studied. Here we present the first examples of macrocyclic pyridazine-bridged dicobalt(II) complexes (Figure) along with their unique electrochemical and magnetic properties.[1] Of particular note is an air stable dicobalt(II) complex of the Schiff-base macrocyclic ligand L which exhibits unique magnetic properties for a cobalt complex and represents a first step towards the development of a “usable” spin-transition polymer.
We thank the Marsden Fund (RSNZ) and FRST (NZ) for supporting this research.
[1] S. Brooker, R.J. Kelly, P.G. Plieger, Chem. Commun., 1998, 1079; S. Brooker, P.G. Plieger, B. Moubaraki and K.S. Murray, Angew. Chem. Int. Ed., 1999, 38, 408; S. Brooker, D.J. de Geest, R.J. Kelly, P.G. Plieger, B. Moubaraki, K.S. Murray and G.B. Jameson, Dalton, 2002, 2080; S. Brooker, Eur. J. Inorg. Chem., 2002, 2535.
IC-03 February 2-6, 2003 Melbourne 14 Stereochemical Effects on Intervalence Charge Transfer in Polymetallic Supramolecular Assemblies
Deanna M. D'Alessandro and F. Richard Keene School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Queensland 4811, Australia
Ruthenium(II) and osmium(II) polypyridyl complexes have been the subject of extensive recent multidisciplinary research efforts, motivated largely by the potential of "polymetallic supramolecular assemblies" derived from them in photo-activated molecular devices. Dinuclear ligand-bridged mixed-valent complexes have received considerable attention in this context, as the intervalence charge transfer (IT) absorption generated in such species provides a powerful and sensitive probe of inter-metal electron transfer processes. However, the influence of the inherent stereochemistry of these species on intramolecular electron transfer has not been addressed [1].
The present studies have revealed differences between the IT characteristics of the meso and racemic diastereoisomers of a range of ligand-bridged 5+ dinuclear systems such as [{Ru(bpy)2}2(m-dpo)] (a) {bpy = 2,2’-bipyridine; dpo = 3,4-di(2-pyridyl)-1,2,5- oxadiazole} (Figure 1) [2,3]. The access to subtle variations in redox asymmetry between the stereoisomers has permitted a new and intimate probe of reorganisational effects on intramolecular electron transfer due to solvent and anion association. (b) Previously, such contributions had been exclusively Figure 1. X-ray crystal structure of meso- 4+ studied by the variation of more global features such [{Ru(bpy)2}2(m-dpo)] (a), and the IT bands observed in the near-IR for the as the identity and coordination environments of the meso and racemic diastereoisomers of the participating metal centres. mixed-valent [5+] species (b).
The presentation will detail the first observation of stereochemical effects on the IT process in di- and tri-nuclear ligand-bridged complexes, utilising a combination of electrochemical, computational, theoretical and spectroelectrochemical studies of solvato- and thermo-chromism. The new insights they provide into the factors which influence the barriers to intramolecular electron transfer will also be discussed. ______[1] F.R. Keene, Coord. Chem. Rev., 1997, 166, 121-159; F.R. Keene, Chem. Soc. Rev., 1998, 27, 185-193. [2] D.M. D'Alessandro, L.S. Kelso and F.R. Keene, Inorg. Chem., 2001, 40, 6841-6844. [3] C. Richardson, P.J. Steel, D.M. D'Alessandro, P.C. Junk and F.R. Keene, J. Chem. Soc., Dalton Trans., 2002, 2775-2785.
IC-03 February 2-6, 2003 Melbourne 15 Cyclen-based Water Soluble Metal Ion Activated Molecular Receptors Akhmad Damsyik,a Kevin P. Wainwrighta and Stephen F. Lincoln b
aSchool of Chemistry, Physics and Earth Sciences, The Flinders University of South Australia, GPO Box 2100, Adelaide, South Australia 5001 bDepartment of Chemistry, University of Adelaide, Adelaide, South Australia 5005
[email protected] The studies of the inclusion chemistry of basket-like molecules such as cyclodextrins and calixarenes have prompted the investigation of many other types of molecules that show the capability of incorporating small molecules in their cavities. These include a number of ligands derived from cyclopolyaza macrocycles which assemble into an appropriate conformation upon metal ion complexation.[1] However, studies of this type have generally been limited to the use of organic solvents. Water soluble systems are needed to mimic natural systems that occur in physiological conditions. The reaction of cyclen derived ligands, that have four phenolic pendant arms, with chlorosulfonic acid has led to the formation of sulfonated derivatives with a sulfonate group attached to each aromatic ring. This provides a potential molecular receptor, resembling the water soluble sulfonated derivatives of calixarenes, which is available for metal ion complexation and molecular inclusion studies.
H3C O O CH3
OH N N OH
OH N N OH
H3C O O CH3
1. ClSO 3H
2. H 2O/NaOH
- SO - O3S 3
H3C O O CH3
OH N N OH .4Na + OH N N OH
H3C O O CH3
- - O3S SO3
Scheme 1 : Sulfonation reaction of cyclen with four phenolic pendant arms
[1] C. B. Smith, A. K. W. Stephens, K. S. Wallwork, S. F. Lincoln, M. R. Taylor, and K. P. Wainwright, Inorg. Chem., 2002, 47, 1093-1100.
IC-03 February 2-6, 2003 Melbourne 16 Tunable crystal host properties in (pyridyloxy)cyclotetraphosphazenes Eric W. Ainscough,a Andrew M. Brodiea and Andreas Derwahla a Chemistry - Institute of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand [email protected] The formation of inclusion adducts by the entrapment of small molecules into the lattices of a range of organic host compounds, to form supramolecular assemblies, is receiving considerable attention [1]. Such hosts show potential in many areas, e.g. as templates for polymerisation re- actions, for the separation of molecules, for non-linear optical activity, for drug purification and for trapping and storage of toxic materials. Aromatic dioxy substituted spirocyclotriphos- phazenes are known to form hexagonal tunnels within the lattice, making use of the rigid, pad- dle-wheel arrangement of the substituents and the intermolecular van-der-Waals interaction of the aromatic residues [2]. Although cyclotetraphosphazenes exhibit a flexible eight-membered ring and consequently cannot form those rigid paddle-wheels as seen in their trimer analogues, they can be used to engineer hosts with tubular tunnels provided an appropriate substituent, which is capable of forming two- and three-dimensional hydrogen-bond networks, is used. It ap- pears that the ability of the cyclophosphazene ring nitrogen atoms to contribute to this network can be fine-tuned by altering the substituents on the phosphorus ring atoms. Hence we describe how the introduction of the 4-methyl substituent into the pyridyloxy rings of octakis(2-pyridyl- oxy)cyclotetraphosphazene (1) causes a change in the crystal structure of the cyclotetraphos- phazene to a clathrate-type structure with tunnels extending through the lattice which are occu- pied by either dichloromethane, (compound 2) or water (compound 3) guest molecules generating 7.5 Å and 5.5 Å diameter tunnels.
R R
N R O R N N O P N O N P N O O N P N O N P O N N O R R N
R R
Compound 1, N4P4(OC5H4N)8 R = H . . Compound 2, N4P4(OC6H6N)8 2CH2Cl2 R = CH3 . R = CH . Compound 3, N4P4(OC6H6N)8 H2O 3 Figure 1: Packing diagram of 2 viewed down the a axis
[1] G. R. Desiraju, Nature, 2001, 412, 397.
[2] H. R. Allcock, N. J. Sunderland, Macromolecules, 2001, 34, 3069 and references therein.
IC-03 February 2-6, 2003 Melbourne 17 Novel Reactivity of High Valent Biomimetic Molybdenum Complexes
Christian J. Doonan and Charles G. Young
School of Chemistry, University of Melbourne, 3010, Victoria, Australia
The Xanthine Oxidase family of enzymes are ubiquitous in biology. They catalyse the oxidation of a variety of substrates via formal oxygen atom transfer. Crystallographic and spectroscopic data indicate that the active site of these enzymes contains a cis- [MoOS]2+ centre. However, the role of the catalytically crucial terminal sulfur in substrate turnover is not fully understood [1]. Recent developments in our laboratory suggest that sulfur may play a formal role in substrate activation.
Pr Pr Reaction of Tp MoO(OPEt3)X (Tp = hydrotris(3-isopropylpyrazol-1-yl)borate; X = substituted phenolate and naptholate derivatives) with propylene sulfide result in complexes containing a sulfur-carbon bond (Figure 1). We propose that the reaction pathway proceeds via a cis-[MoOS]2+ centre analogous to the enzyme.
O N O
Mo
N S
Pr Figure 1. Tp MoO(OSC10H6).
[1] R. Hille, chem.. rev. 1996, 96. 2757
IC-03 February 2-6, 2003 Melbourne 18 Near Naked Cationic Lanthanoid Complexes Glen B. Deacon, David J. Evans, Craig M. Forsyth and Peter C. Junk School of Chemistry, Monash University, 3800, Victoria, Australia
The catalytic properties of lanthanoid complexes are increasingly being investigated due to the Lewis acid nature they intrinsically provide [1, 2]. Near naked Ln3+ ions, i.e. metal ions homoleptically bounds by solvent molecules, are of interest as reaction sites as they should have 3+ strong Lewis acidity. Approaches to this target include LnLn where L is readily displaced e.g. - thf, MeCN, etc. To synthesise these homoleptic cations, weakly coordinating anions e.g. AlCl4 , - - ZrCl5(thf), BPh4 , NbCl6 , etc [3] have been utilised.
3+ To date several [LnCl2(thf)] systems have been isolated utilising different weakly coordinating anions observing an isostructural series from La to Yb - independent of the anion ([ZrCl5(thf)] or - [NbOCl4(thf)] ) Additionally, we report the
[Ln(MeCN)n][AlCl4]3 (n = 8 or 9) system, where the coordination number of the lanthanoid decreases from nine to eight as a result of the lanthanoid contraction. Both systems illustrate that the coordination sphere of the lanthanoid metal is
independent of the anion used. Figure 1. Molecular structure of the near naked
complex [Yb(MeCN)8][NbCl6]3.MeCN
[1] V. Lavini, A.D. Maia, I.S. Paulino, U. Schuchardt and W. de Oliveira, Inorg. Chem. Commun., 2001. 4. 582-584.
[2] S. Kobayashi, Synlett, 1994. 689.
[3] G.B. Deacon, B. Gortler, P.C. Junk, E. Lork, R. Mews, J. Petersen and B. Zemva, J. Chem. Soc.-Dalton Trans, 1998. 3887-3891
IC-03 February 2-6, 2003 Melbourne 19 Structural investigations into the unexplored hydroxamic acid chemistry of Pt(II). Timothy W. Failes, Matthew D. Hall, and Trevor W. Hambley School of Chemistry, The University of Sydney, 2006, NSW, Australia [email protected] A distinct lack of attention in the literature has been given to the study of platinum complexes of hydroxamic acids with only one example being recorded involving crystal structure analysis.1 Accordingly, we have examined simple hydroxamates as ligands for Pt(II), in particular focussing on the structural aspects of the (O,O) chelates. The crystal structures of benzo- and salicylhydroxamic acid complexes containing PPh3 and DMSO counter ligands were determined. These complexes illustrate the necessity of the ligand to adopt the doubly deprotonated hydroximate form, and also the need for soft donor trans ligands to stabilise binding to Pt(II).
Attempts at preparing similar diamine complexes led to the formation of novel dinuclear hydroximate complexes. These first examples of diamine-hydroximate complexes of platinum(II) display an unusual (C,N) coordination mode with the surprising deprotonation of the benzohydroximate phenyl ring. The cytotoxicities of the complexes were tested against a panel of cell lines based on the A2780 ovarian cancer cell line and revealed that both dinuclear complexes were less active than their corresponding dichloro parent complexes but with different resistance profiles.
All attempts to generate the corresponding complexes of alkyl hydroxamates have been unsuccessful and thus presumably the presence of an aromatic substituent is required for stability.
[1] P.L. Bellon, et al., J. Chem. Soc. Dalton Trans., 1980, 2060.
IC-03 February 2-6, 2003 Melbourne 20 Synthesis, Electrochemistry and Spectroscopy of Substituted bis(?5- indenyl)iron(II) Complexes Owen J. Curnow,a Glen M. Fern,a Elizabeth M. Jenkins,a Sami Klaib,b Heinrich Langb a Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand b Chemnitz University of Technology, Department of Chemistry, Straße der Nationen 62, D-09107 Chemnitz, Germany [email protected] The cyclopentadienyl anion is arguably the most widely studied ligand in organometallic chemistry. The success of the ligand stems from its ability to stabilize a range of metal oxidation states and the relative ease with which both steric and electronic properties can be altered by the introduction of organic substituents. For ferrocenes, the effects of substitution on the cyclopentadienyl ligand can be observed at the iron centre by cyclic-voltametry and UV/vis spectroscopy. Whereas ferrocenes have been well studied, little work has been carried out on related bis(? 5-indenyl)iron(II) systems. The fusion of a benzo group to the cyclopentadienyl ring allows for greater substitution and increases the number of potential isomers which can be formed.
We report here the synthesis, electrochemistry, and UV/vis spectroscopy of a series of bis(? 5-
indenyl)iron(II) complexes containing Me3Si-, Me-, and Ph2P- substituents (Figure 1). The oxidation potentials can be rationalized in terms of the position of substitution and the individual
substituents Hammet parameter s p. For multiply-substituted indenyl ligands, an additive effect is observed.
Me Me Me3Si PPh2 Fe Me Fe Fe Me SiMe3 PPh2 Me Me
Figure 1 : Examples of substituted bis(?5-indenyl)iron(II)
IC-03 February 2-6, 2003 Melbourne 21 The Preparation and Reaction of Some Crowded Ortho-manganated Aryl Ketones
Victor D Fester, Brian K Nicholson, Lyndsay Main Chemistry Department, University of Waikato, Hamilton, New Zealand [email protected]
Cyclometallation reactions involving manganese have been studied extensively at Waikato University [e.g. 1-3]. Cyclometallated species are of particular interest because the metallated carbon atom becomes a specific site for further reaction, often resulting in the formation of organic compounds that are otherwise difficult to synthesise. The use of manganese, in particular, has been found to activate substrates like aromatic ketones which do not readily react with the more widely-used, and much more expensive, palladium.
Some crowded ortho-manganated aryl ketones of the type 1, where R = Ac, CO2Bn, have been prepared. Their syntheses will be discussed in this poster, together with their reactions with the alkyne, PhCºCH, and the activated unsaturated compound, CH2=CHCO2Me, under various reaction conditions.
O
Mn(CO)4
OR
1
References
[1] L. Main, B.K. Nicholson, Adv. Metal Org. Chem. 1994, 3, 1.
[2] J.M. Cooney, C.V. Depree, L. Main, B.K. Nicholson, J Organomet. Chem. 1996, 515, 109.
[3] J.M. Cooney, L. Main, B.K. Nicholson, J Organomet. Chem. 1996, 516, 191.
IC-03 February 2-6, 2003 Melbourne 22 New Square-Planar Cationic Platinum(II) Compounds: A Cure for Cancer? Dianne M. Fisher,a Ronald R. Fentona and Janice R. Aldrich-Wrightb a School of Chemistry, The University of Sydney, 2006, New South Wales, Australia b Department of Chemistry, School of Food, Science and Horticulture, University of Western Sydney, Campbelltown Campus, Locked Bag 1797, Penrith South DC 2560, New South Wales, Australia. [email protected] A series of platinum(II) compounds have been designed to interact with DNA via a different binding mode than that of current anti-cancer compounds (e.g. cisplatin). Compounds like cisplatin tend to bind covalently to DNA, whereas, these new compounds intercalate between the base pairs of the DNA molecule.
Square-planar metallointercators are composed of two parts: an intercalating moiety; and a non- intercalating (or ancillary) group (Figure 1). These components are typically neutral, nitrogen- based ligands. The planar intercalating segment is comprised of at least three aromatic rings fused together, whereas, there are no structural requirements for the ancillary portion. The intercalating and ancillary parts bind to the metal atom through two nitrogen donor atoms of each ligand.
The effect of chirality and/or the presence of substituents on the ancillary ligands and substituents on the intercalating ligand have been investigated in designing these square-planar compounds. Subtle changes in the structure of the complex induce differing levels of biological activity. The biological activity of these complexes has been determined through in vitro testing on human cell lines. Results have shown most compounds to be biologically active, but to varying degrees.
Some compounds synthesised and characterised to date have displayed a higher level of activity and greater solubility than cisplatin. These features suggest that such compounds may be likely to demonstrate higher clinical effectiveness and lower toxicity compared to current platinum- based compounds in clinical use.
I Pt A
Figure 1. Model of a platinum(II) metallointercalator, where I = intercalating ligand and A = ancillary ligand.
IC-03 February 2-6, 2003 Melbourne 23 Complexes of Vanadium(III) with Acetate Nicola E. Brasch, Alison J. Edwards, Fiona H. Fry, and Nichola C. McCann Research School of Chemistry, The Australian National University, Canberra 0200, ACT, Australia
[email protected] Ascidians of the suborder Phlebobranchia are small marine animals that sequester vanadium(V) from seawater and reduce it to vanadium(III). These small creatures concentrate vanadium by up to 8 orders of magnitude, storing vanadium(III) in their blood cells at concentrations as high as 1 M.[1] How or why these creatures accumulate this metal ion is unknown. In addition, the chemistry of V(III) itself, especially in aqueous systems, is poorly defined compared with that of vanadium in the more stable oxidation states of +4 and +5. Our studies of V(III) complexes have commenced with the acetate ligand as it is used as a buffer in the isolation of compounds from ascidian blood cells,[2][3] in addition to being a simple model for amino acids. X-ray diffraction studies of V(III)-acetato complexes isolated from aqueous solution to date have shown that at least two cationic complexes are formed. The first compound (see Figure 1) is a tetranuclear species with a ratio of acetate:vanadium of 1:1, while the second salt isolated shows an acetate:vanadium ratio of 2:1, with a trinuclear core. A titration study by 1H NMR spectroscopy clearly demonstrates the presence of a 2:1 species is also present in solution, as well as the existence of a second species with a lower acetate:vanadium(III) ratio.
Figure 1. The cation of the 1:1 Acetate:Vanadium(III) complex as determined by X-ray crystallography.
[1] H. Sigel and A. Sigel (ed.) Metal Ions in Biological Systems, Marcel Dekker, Inc.: New York, 1995.
[2] C.J. Hawkins, M.F. Lavin, D.L. Parry, and I.L. Ross, Anal. Biochem, 1986, 159, 187. [3] C.L. Dorsett, C.J. Hawkins, C.J. Grice, M.F. Lavin, P.M. Merefield, D.L. Parry, and I.L. Ross, Biochemistry, 1987, 26, 8078.
IC-03 February 2-6, 2003 Melbourne 24 Radical Cleavage and Aggregation Processes in Cyclopentadienylchromium Chemistry Zhiqiang Weng, Weng Kee Leong, Jagadese J. Vittal and Lai Yoong Goh*
Department of Chemistry, National University of Singapore, Singapore 119260 [email protected]
The efficacy of the 17-electron CpCr(CO)3. species (1) in the scission of chalcogen- chalcogen and chalcogen-pnicogen bonds in both inorganic and organic substrates has been amply demonstrated.[1,2] Our recent findings show that it is equally effective in the cleavage of metal- nonmetal and inter-element bonds in C-, N-, P- and S-containing ligands of cyclopentadienylchromium complexes. Subsequent aggregation of the fragments with accompanying rearrangement and C – C or P – P coupling, then generates an unexpected variety of complexes, as shown in the chart below, for reactions involving dibenzothiazolyl disulphide [3] and Lawesson’s reagent.
N N S S S Cr Cr C C Cr (1) Cr C N S H S Cr S Cr O Cr S Cr CO + N Cr + S OC OC Cr Cr OC CO Cr S S S Cr Cr N S Cr N N Cr OC S N C Cr Cr C N S S S S Cr S
CH3 O
OC H OC OC H S Cr Cr Cr P Cr S + Cr Cr Cr S OC P CO + CO Cr OC P (1) H P P H H CO P Cr O O O O CH3 CH3 O CH3 H3C CH3
CO OC S OC CO OC Cr Cr (1) Cr Cr P P P OC CO OC CO (i) S S O O O CH3 H3C CH3 (i) = , S8 or Lawessons' reagent
[1] (a) L. Y. Goh, Coord. Chem. Rev. 1999, 185-186, 257. (b) L. Y. Goh, W. Chen, R. C. S. Wong, J. Chem. Soc., Chem. Commun. 1999, 1481. (c) L. Y. Goh, M. S. Tay, T. C. W. Mak, R.-J. Wang, Organometallics 1992, 11, 1711. [2] (a) L. Y. Goh, W. K. Leong, P. H. Leung, Z. Weng, I. Haiduc, J. Organomet. Chem. 2000, 607, 64. (b) L. Y. Goh, Z. Weng, W. K. Leong, I. Haiduc, K. M. Lo, R. C. S. Wong, J. Organomet. Chem. 2001, 631, 67. (c) L. Y. Goh, Z. Weng, W. K. Leong, P. H. Leung, Angew. Chem. Int. Ed. 2001, 40, 3236.
[3] L. Y. Goh, Z. Weng, W. K. Leong, J. J. Vittal, J. Am. Chem. Soc. 2002, 124, 8804.
IC-03 February 2-6, 2003 Melbourne 25 Guest-Dependent Spin Crossover in Nanoporous Molecular Framework Materials Gregory J. Halder,a Cameron J. Kepert,a Boujemaa Moubaraki,b Keith S. Murrayb and John D. Cashionc a School of Chemistry, University of Sydney, 2006, New South Wales, Australia b School of Chemistry, Monash University, 3800, Victoria, Australia c School of Physics and Materials Engineering, Monash University, 3800, Victoria, Australia [email protected] There is currently a major international push toward the design, synthesis and characterisation of molecular materials with applications in important areas such as information processing, memory devices, data storage and retrieval, and magnetic and optical switches. The spin- crossover centre offers a type of molecular switch that exists in two different electronic states that have marked differences in geometry, magnetism and colour. The incorporation of both nanoporosity and electronic switching into such materials is unique in allowing detailed in-situ studies of the steric and electronic influences of adsorbed guests on the spin-crossover centres.
Structural and magnetic characterisation of the robust nanoporous spin-crossover framework II Fe (azpy)2(NCS)2.½(guest) (azpy = 4,4?-azopyridine) (1) has recently been completed. The structural refinement revealed doubly interpenetrating iron(II)-azpy rhombic-grids(A). Modified single crystal X-ray diffraction measurements [1] of both the ethanol loaded and fully desolvated forms have enabled a thorough investigation into the structural consequences of desolvation.
Through related magnetic studies of 1 a guest-dependent ‘half’ spin-crossover has been observed [2]. A high-spin to low-spin transition between 150 K and 50 K was observed for one of the two crystallographically distinct iron(II) centres in the solvated framework, while no transition was observed after desolvation of the framework (B). [1] C.J. Kepert, M.J. Rosseinsky, Chem. Commun. 1999, 375. [2] G.J. Halder, C.J. Kepert, B. Moubaraki, K.S. Murray, J.D. Cashion, Science, 2002, 298, 1762.
IC-03 February 2-6, 2003 Melbourne 26 Does Platinum(IV) Survive in Tumour Cells? Matthew D. Hall,a Shahriar Amjadi,a Philip Beale,b Zhonghou Cai,c Carolyn T. Dillon,a Garry J. Foran,d Barry Lai,c Anton P.J. Stampfl,d Mei Zhang,b and Trevor W. Hambleya a Centre for Heavy Metals Research, School of Chemistry, The University of Sydney, N.S.W. 2006, Australia b Department of Medical Oncology, Sydney Cancer Centre, Royal Prince Alfred Hospital, Camperdown, N.S.W. 2050, Australia c Experimental Facilities Division, Argonne National Laboratory, Argonne, Il 60439, U.S.A. d Australian Synchrotron Research Program, c/- ANSTO, Private Mail Bag 1, Menai, N.S.W. 2234, Australia [email protected] The rates and mechanism of reduction of platinum(IV) complexes by endogenous biomolecules in vitro have been extensively investigated.[1] However, no reliable spectroscopic method for observing the reduction of platinum(IV) complexes in biological systems has been reported. Current techniques do not allow for facile in situ determination of the average or component oxidation states of a system. Here we describe the use of X-ray absorption near edge spectroscopy (XANES) to provide Figure 1. XANES spectra of platinum(II) (?????) and information about the relative platinum(IV) (??) complexes, showing the difference in proportions of platinum(II) and peak height between the two oxidation states. platinum(IV) complexes in biological systems. Using XANES, the intracellular reduction of platinum(IV) complexes in cancer cells has been observed directly, and the proportion of reduction after 2 h was found to correlate with their reduction potentials. The localisation of a number of platinum(IV) complexes has been investigated using micro-SRIXE imaging of ovarian cancer cells, revealing that cellular distribution of the complexes is similar to that of cisplatin. The cytotoxicity and lipophilicity of platinum(IV) complexes with a range of reduction potentials have been determined to elucidate
the importance of log Poct and Ep on their cytotoxicity.
Thanks to the Australian Synchrotron Research Program, Australian Research Council and the University of Sydney Cancer Research Fund for financial support.
[1] M.D. Hall and T.W. Hambley, Coordination Chemistry Reviews, 2002, 232, 49.
IC-03 February 2-6, 2003 Melbourne 27 Rare Earth Complexes From High Temperature Syntheses
Glen B. Deacon,a Peter C. Junk,a Rita Harika,a Stuart G. Leary,a Brian W. Skeltonb and Allan H. Whiteb a Monash University Chemistry Dept., Clayton, Vic, 3800, Australia, b School of Chemistry, University of Western Australia, Crawley, WA, 6009. [email protected]
The direct reaction of lanthanoid metals with relatively weak protic acids is a conceptually simple route to a wide range of reactive lanthanoid complexes such as (1). Activation of the lanthanoid metal by addition of mercury or other means is usually needed. Examples of such activated metal reactions include ytterbium or europium with cyclopentadiene in liquid 1-3 ammonia.1 metal atom reactions with primary acetylenes and pentamethylcyclopentadiene, 4 and the direct synthesis of Ln(NH2)3. When carried out in the absence of donor solvents these reactions can provide a route to homoleptic complexes, as demonstrated by the recent synthesis of lanthanoid (II, III or II/III) 5, 6 3,5-di-tert-butylpyrazolates. An alternative outcome from the absence of donor solvents is the production of heteroleptic lanthanoid complexes where one or more protonated ligands bind to the lanthanoid through an alternative donor site. This poster will present not only the results of direct metallation reactions and similar mercury activated reactions but also heteroleptic complexes from metallation reactions where greener alternatives for the lanthanoid metal activation were employed.
1. G. Wilkinson, F. G. A. Stone and E. W. Abel., "Comprehensive Organometallic Chemistry II," p. 11 130. Pergamon, Oxford, 1995. 2. H. Schumann, J. A. Meese -Marktsche and L. Esser., 1995, 95, 895. 3. M. N.Bochkarev, L. N. Zakharov and G. S. Kalinina., "Organoderivatives of the Rare Earth Elements,,". Kluwer Academic, Dordrecht,, 1995. 4. R. Anwander, Top. Curr. Chem., 1998, 179, 33. 5. G. B. Deacon, A. Gitlits, B. W. Skelton and A. H. White., Chem. Commun., 1999, 1213. 6. G. B. Deacon, A. Gitlits, P. W. Roesky, M. R. Burgstein, K. C. Lim, B. W. Skelton and A. H. White, Chemistry-A European Journal, 2001, 7, 127-138.
Figure 1- Crystal structure of Nd(cinnamate)3 (1)
IC-03 February 2-6, 2003 Melbourne 28 Synthesis and Structural Studies of Some Lanthanoid(III) 1,2- Benzenedisulfonates Glen B. Deacon,a Rita Harika,a Peter C. Junk,a Brian W. Skeltonb and Allan H. Whiteb
a Monash University Chemistry Dept., Clayton, Vic, 3800, Australia, b School of Chemistry, University of Western Australia, Crawley, WA, 6009. [email protected]
Ln2L3.xH2O (L = 1,2-benzenedisulfonate; Ln = Sc (1), x = 14; Ln = Y (2), x = 16; Ln = La (3), x = 7; Ln = Ce (4), x = 6; Ln = Pr (5), x = 10; Ln = Nd (6), x = 18; Ln = Sm, x = 18.25; Ln = Eu (8), x = 16; Ln = Gd (9), x = 16; Ln = Tb (10), x = 16; Ln = Ho (11), x = 16; Ln = Yb (12), x = 16; Ln = Lu (13), x = 16) were synthesized by treating a solution of
1,2-benzenedisulfonic acid with Ln2O3 and single crystals of 2, 7-13 were obtained from aqueous solution. X-ray crystallographic studies revealed isomorphous structures of the
type [LnL(H2O)6]2[L].4H2O for 2, 8-13, which contain eight-coordinate Ln with the disulfonate ligand chelating through one oxygen of each sulfonate group giving a seven- membered ring. At this stage the samarium complex is unique, viz
[SmL(H2O)6][SmL2(H2O)4].8.25H2O. A fortuitous synthesis led to isolation of
[Nd2L2L’(H2O)8] (14) (L = 1,2-benzenedisulfonate, L’ = perfluoroadipate), which has eight-coordinate (two adipate oxygens, three sulfonate oxygens, three water oxygens). An attempt to synthesise a La analogue deliberately by
reaction of La2L3 and L’H2
produced [H7O3][LaL2] (15), which was then prepared by the
treatment of La2O3 with an
excess of LH2.
The anion in [SmL(H2O)6][SmL2(H2O)4].8.25H2O
IC-03 February 2-6, 2003 Melbourne 29
Self-Assembly of Di- and Tetranuclear Copper(II) Complexes of Two Homologous Bis-Terdentate Diamide Ligands Julia Hausmann and Sally Brooker* Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand
1 The new diamide ligand N,N'-bis(2-pyridylmethyl)-2,3-pyrazinedicarboxamide (H2L ) as well 2 as the known ligand N,N'-bis[2-(2-pyridyl)ethyl]-2,3-pyrazinedicarboxamide (H2L ) [1, 2] (Fig. 1) have been synthesised. As it is commonly observed, the amide nitrogen atoms of these ligands are expected to lose their protons on complexation with copper(II) ions and to function as anionic donors. It has been found, however, that complexation reactions employing one equivalent of copper(II) ions do not lead to complexes of the deprotonated ligands. Despite the similarity of 1 these two ligands, H2L forms the dimeric complex II 1 2 [Cu (H2L )(MeCN)]2(BF4)4 while H2L affords the tetrameric Figure 1. II 2 2 complex [Cu 4(H2L )2(HL )2]4(BF4)6. In both complexes the
copper(II) ions are in a square-pyramidal N4O coordination sphere involving one carbonyl oxygen. Their structures will be presented.
On employment of two equivalents of copper(II) 1 ions, the ligand H2L retains one “excess” proton, centred by hydrogen-bonds between the two amide oxygen atoms, which is shown for the resulting II 1 complex [Cu 2(HL )(MeCN)4](BF4)3 in Fig. 2. In II 1 addition, the grid-type structure [Cu (HL )]4(BF4)4 of the mono-deprotonated ligand (HL1)-, obtained Figure 2. Molecular structure of the complex by the deliberate deprotonation of the dimeric II 1 3+ cation [Cu 2(HL )(MeCN)4] . The hydrogen II 1 complex [Cu (H2L )(MeCN)]2(BF4)4 with one atoms with the exception of H(1) have been omitted for clarity. equivalent of base, is presented.
[1] E. B. Fleischer, D. Jeter, R. Florian, Inorg. Chem. 1974, 13, 1042-1047. [2] E. B. Fleischer, M. B. Lawson, Inorg. Chem. 1972, 11, 2772-2775.
IC-03 February 2-6, 2003 Melbourne 30 Towards Soluble Heavy Alkaline Earth Metals: Calcium, Strontium, and Barium complexes of anthracene derivatives Julia Hitzbleck, and Karin Ruhlandt-Senge Department of Chemistry, Syracuse University, Syracuse, NY, 13244-4100, USA
[email protected] Magnesium anthracenide is known as a useful synthetic reagent as well as a precursor for a THF soluble from of magnesium hydride [1]. The homogeneous solution of the complex displays a highly activated form of magnesium metal and facilitates the formation of sterically hindered Grignard reagents [2]. The advantage of homogeneous reaction conditions is desired for clean synthetic pathways due to milder reaction conditions and increased reaction rate. We are interested in the preparation and characterization of the heavier alkaline earth metal analogs as soluble source of highly activated alkaline earth metals in various applications. However, the heavier analogs bearing the unsubstituted anthracene ligand are insoluble in THF and other organic solvents so that characterization is limited solid state NMR and IR, UV/VIS methods [3], and applications will be limited due to heterogeneous nature of the reaction mixture.
Solid-state 13C-NMR as well as 1H-NMR of the hydrolyzed 2,6- and 2,7-Di-tert-butylanthracene complexes of the heavier alkaline earth metals suggests a metal binding to the central ring similar to the magnesium derivatives.
Current research concentrates on the synthesis of substituted anthracene derivatives, which are expected to show increased solubility for the target metal complexes. Synthetic schemes involve substitution of commercially available anthracene and dihydroanthracene as well as ring formation via Friedel-Crafts alkylation.
[1] B. Bogdanovic, P. Bons, M. Schwickardi, and K. Seevogel, Chem. Ber., 1991, 124, 1041- 1050.
[2] S. Harvey, P.C. Junk, C.L. Raston, and G. Salem, J. Org. Chem., 1988, 53, 3134-3140. [3] H. Bönnemann, B. Bogdanovic, R. Brinkmann, N. Egeler, R. Benn, I. Topalovic and K. Seevogel, Main Group Metal Chemistry, 1990, 13, 341-362.
IC-03 February 2-6, 2003 Melbourne 31 Synthesis and Structure of a Series of Boron Porphyrins- highlighting the different structural motifs. Michael C. Hodgsona, Penelope J. Brothersa, Clifton E. F. Rickarda, Walter Siebetb and Andre Weissb. a Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand. b Anorganisch Chemisches Insttitut., Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
In previous work, we have established that the porphyrin ligand can accommodate two boron atoms. We have shown thus far there are three distinctive structural types (Fig. 1-3). The first two examples contain a B-O-B bridging fragment of either X-B-O-B-X (X=F, OH)[1] or the
more unusual B2O2 four-membered ring[2] coordinated within the porphyrin cavity. The third structural type of boron porphyrin complex also contains two boron atoms with a B-B single bond coordinated within the porphyrin cavity.[3]
Fig. 1 Fig. 2 Fig. 3
B2OF2(por) B2O2(BCl3)2(por) B2Bu2(por)
Current work is investigating other possible structural types and in particular (BX2)2(por) (X=hal) in which the boron atoms are not linked. The same methodology used for the synthesis of the boron porphyrin complexes has been applied to several other macrocycles including expanded porphyrin ligands, porphyrazines and dibenzotetraaza[14]annulene. The synthesis, structures and chemical properties of selected examples of these complexes will be discussed.
[1] W. J. Belcher, P. D. W. Boyd, P. J. Brothers, M. J. Liddell and C. E. F. Rickard, J. Am. Chem. Soc., 1994, 13, 8416. [2] W. J. Belcher, M. Breede, P. J. Brothers and C. E. F. Rickard, Angew. Chem., Int. Ed. Engl., 1998, 37, 1112. [3] A. Weiss, H. Pritzkow, P. J. Brothers and W. Siebert, Angew. Chem., Int. Ed. Engl., 2001 40, 4182.
IC-03 February 2-6, 2003 Melbourne 32 Electrochromic Linear and Nonlinear Optical Properties of Alkynylbis(diphosphine)ruthenium Complexes Mark G. Humphrey,a,* Clem E. Powell,a Marie P. Cifuentes,a Joseph P. Morrall,a Robert Stranger,a Marek Samoc,b Barry Luther-Davies,a and Graham A. Heathc a Department of Chemistry, Australian National University,Canberra, ACT0200, Australia b RSPhysSE, Australian National University,Canberra, ACT0200, Australia c RSC, Australian National University,Canberra, ACT0200, Australia [email protected] New materials with desirable nonlinear optical (NLO) properties are expected to provide an efficient means of controlling and processing light beams used in photonic technologies; to this end, the NLO properties of a vast panoply of organic, inorganic and organometallic compounds have been studied. While there has been considerable success in the past decade at preparing compounds with large intrinsic nonlinearities, attention has recently focussed on possibilities for reversibly modulating ("switching") nonlinearities. This is an area of NLO materials research in which inorganic molecular materials may be superior to organics. We have previously demonstrated that alkynylruthenium complexes can have significant quadratic and cubic optical nonlinearities [1]. We have now used alkynylruthenium complexes to demonstrate facile electrochromic switching of optical nonlinearity [2].
A combination of cyclic voltammetry, UV-vis-NIR spectroelectrochemistry, and time-dependent density functional theory has been used to identify and assign intense transitions of metal alkynyl complexes at technologically-important wavelengths in the oxidized state. These absorption bands have been utilized to demonstrate facile switching of cubic NLO properties at 12 500 cm-1 (corresponding to the wavelength of maximum transmission in biological materials such as tissue) using Z-scan measurements employing a modified optically transparent thin-layer electrochemical cell, the first electrochromic switching of molecular nonlinear refraction and absorption, and the first switching of optical nonlinearity using an electrochemical cell. + Ph P PPh Ph P PPh 2 2 -e- 2 2 Cl Ru Cl Ru - Ph2P PPh2 +e Ph2P PPh2
NIR transparent NIR band Cubic NLO "off" Cubic NLO "on" [1] A.M. McDonagh, M.G. Humphrey, M. Samoc, B. Luther-Davies, S. Houbrechts, T. Wada, H. Sasabe, and A. Persoons, J. Am. Chem. Soc., 1999,121, 1405-1406. [2] C.E. Powell, M.P. Cifuentes, J.P. Morrall, R. Stranger, M.G. Humphrey, M. Samoc, B. Luther-Davies, and G.A. Heath, J. Am. Chem. Soc., in press, paper no JA0277125.
IC-03 February 2-6, 2003 Melbourne 33 Stabilisation of Double a-Helix Conformers of Dinuclear Metal Helicates Containing Tetra(tertiary phosphines) Heather J. Kitto and S. Bruce Wild Research School of Chemistry, Australian National University, ACT 0200, Australia [email protected] The self-assembly of molecules into large supramolecular structures is an important feature in biology and is now readily achieved in inorganic coordination chemistry with appropriate helicating ligands and metal ions. Previous work in our laboratory has shown that (S,S)- tetraphos spontaneously self-assembles dinuclear metal helicates of the type (M)-[M2{(R,R)- 1 tetraphos}2](PF6)2 upon reaction with univalent silver and gold salts. The d or l twist of the central 10-membered ring containing the two metal ions, which has the chiral twist-boat-chair- boat conformation, generates the double a-helix or side-by-side parallel helix conformer of the helicate. 1H NMR spectroscopic investigations indicated rapid interconversion between the conformers in solution, although in the solid state the silver helicate crystallises with both conformers in the unit cell and the gold helicate with the more compact side-by-side conformer alone. A related double-stranded tricopper(I) helicate of a configurationally pure hexa(tertiary phosphine) has recently been synthesised and characterised by X-ray crystallography.2
Current work is focussed on the synthesis of (R,R)-tetraphos*, which molecular modelling indicates will react with univalent Group 11 salts to produce stereoselectively the double a-helix conformers of the dinuclear metal helicates.
Ph Ph
S S Ph 2 P P P PP h 2
(S , S)- t e t ra p h o s
Me Me Ph R R Ph
R R Ph 2 P P P PP h 2
( R,R ) -t e t ra p h o s *
[1] A.L. Airey, G.F. Swiegers, A.C. Willis, and S.B. Wild, Inorg. Chem. 1997, 36, 1588. [2] P.K. Bowyer, V.C. Cook, N. Gharib-Nasseri, P.A. Gugger, A.D. Rae, G.F. Sweigers, A.C. Willis, J. Zank and S.B. Wild, Proc. Natl. Acad. Sci. (USA) 2002, 99, 4877
IC-03 February 2-6, 2003 Melbourne 34
Copper(II) binding proteins in bacteria
Melissa Koay, Zhiguang Xiao and Anthony G. Wedd School of Chemistry, The University of Melbourne, 3010, Victoria, Australia [email protected]
Metallochaperone proteins have been studied in a number of organisms. Those which bind Cu(I) appear to do so through cysteine-sulfur residues. Recently, there has been increasing interest in the transport mechanisms of aerobic bacteria, some of which bind Cu(II).
The copper binding protein cutA1, from Escherichia coli, appears to be involved in metal tolerance of divalent Ni, Zn, Cu, Co and Cd. [1] CutA1 has been cloned, isolated and purified. 2+ -1 -1 Binding of one equivalent of Cu results in an absorption band at lmax 380nm (e~4000M cm ). Protein mapping and mass spectrometric techniques have been employed to probe the possible metal binding ligands Cys39, Trp52, Glu61 and His84.
CopC, from Pseudomonas syringae pathovar tomato, is another copper binding protein thought to be involved in cellular copper resistance.[2] CopC has also been cloned, isolated and purified. 2+ CopC binds a single equivalent of Cu which results in an absorption band at lmax 616nm (e=80M-1cm-1). Recently, an NMR solution structure of the apo-protein was reported (Figure 1).[3] The potential metal binding ligands, His1, Glu27, Asp89 and His91, are currently under investigation.
Figure 1: NMR solution structure of apo-CopC. [3] ______[1] Sheik-Tao Fong et al, Molecular Microbiology, 1995, 15, 1127-1137. [2] Jae-Soon Cha et al, Proc. Natl. Acad. Sci. USA, 1991, 88, 8915-8919. [3] Fabio Arnesano et al, Structure, 2002, 10, 1337-1347.
IC-03 February 2-6, 2003 Melbourne 35 New Coordination Polymers using Dicyanamide and Nitrogen-Donor Heterocyclic Ligands Anna Kutasi,a Stuart R. Batten,a Boujemaa Moubaraki a and Keith S. Murraya a School of Chemistry, Monash University, 3800, Victoria, Australia [email protected]
Studies of coordination polymers of the d-block ions incorporating the non-linear pseudohalide ligand dicyanamide (dca, N(CN)2-) have led to a wide range of topologies and magnetic properties. Structures incorporating tridentate dca have been shown to display long-range ordering, which may be due to the shorter magnetic exchange pathway. In contrast, when dca acts as a bidentate ligand, long range ordering is generally not observed.
This research seeks to modify the metal-dca networks by introducing coligands to encourage tridentate bridging in dca. Consequently, we looked towards more sterically hindered bridging ligands. A series of new coordination polymers derived from a selection of d-block ions incorporating dca and the bridging bidentate ligands phenazine (phz) and quinoxaline (qnx) have been isolated and structurally characterised.
In particular, new polymeric metal complexes of the II II form [M (dca)2(H2O)].phz (M = Fe, Co and Ni) have been synthesised, containing tridentate and bidentate dca II Figure 1. The 2D [M (dca)2(H2O)].phz, ligands (Figure1); long-range order is seen for the Fe showing the different octahedral metal centers. and Ni complex. (Phz not shown)
Another interesting complex developed using dca and II phenazine has the form [M (dca)2(H2O)2].2phz.2EtOH, (MII = Fe, Mn and Ni). Surprisingly the 1D chains of II M (dca)2(H2O)2, are linked together by intercalated phenazine through hydrogen bonding, show interesting magnetic properties.
The crystal structure and magnetic properties of II compounds in the series [M (dca)2(qnx)2] (M = Zn, Cd, Mn, Fe, Co, Ni, Cu) have been determined. The metal ions have octahedral coordination geometry, with four equatorial bidentate dca ligands, and two axial quinoxaline ligands, forming a 1D chain (Figure 2); Figure 2. Interdigitation of chains in [MII(dca) (qnx) ]. weak antiferromagnetic coupling is observed. 2 2
IC-03 February 2-6, 2003 Melbourne 36
New Super- and Supramolecular Receptor Systems. Cages, Chains, Squares and Dendrimers Incorporating Macrocycles As Structural Elements Jonathon Beves,1 Ying Dong,1 Jy Chartres,2 Leonard F. Lindoy,1 George V Meehan2 1 Centre for Heavy Metals Research, School of Chemistry, The University of Sydney, NSW 2006, Australia 2 School of Pharmacy and Molecular Sciences, James Cook University, Townsville Q 4811 Australia. E-mail: [email protected]
Largely employing protecting group chemistry, a range of new multi-component molecular systems incorporating macrocyclic rings as structural elements have been synthesised. Thus, starting from 1,4,8,11-tetraazacyclotetradecane (cyclam) we have established syntheses for the new cyclam derivatives 1 and 2 as well for a number of other species that include both (linked) homo- and hetero-macrocyclic rings. The tritopic receptor 3 provides an example of the latter type. Aspects of the comparative metal ion chemistry of these linked species will be presented.
H H H H H H N N N N N N N N H N N N N N N N H N N N N N N N N N H H H H 2 H H
1 NH S H H N HN O N N N N S N N O NH N N N N N O O H H O 3
New large molecular cages that show unusual binding properties towards both metal ions and small molecules have also been synthesised. One such product is a tris- bipyridyl derivative incorporating Ni(II). In this case, the central metal ion induces a helical twist that extends about 26Å around the entire length of the coordinated ligand. Such behaviour is unusual relative to other reported helical structures in which multiple metal ion coordination is required to induce a helical twist along the length of the system.
Other systems, some synthesised by self-assembly techniques, involve square, catenane and dendritic arrangements of their macrocyclic components. Overall, the resulting nanometre scale structures show potential for generating unusual electronic and other properties - including novel charge transfer, electron transfer, allosteric and/or catalytic behaviour.
IC-03 February 2-6, 2003 Melbourne 37 Cobalt Hub-Caps: Keeping the Wheel on the Axle Julia S. Lock,a Stephen F. Lincoln,a Bruce L. May,a Christopher Eastonb a Chemistry Department, The University of Adelaide, Adelaide, S. A., Australia, 5005. b Research School of Chemistry, Australian National University, A.C.T., Australia, 0200. [email protected] A series of Co(III)-blocked a- and b-cyclodextrin [2]-rotaxanes, one of which is shown in Figure 1, have been prepared. The bulk of the blocking group is already attached to the axle when it is threaded by the cyclodextrin, and the binding of Co(III) causes expansion of the terminal groups, increases their rigidity and makes them highly charged, so that they act as blocking groups. Each of the [2]-rotaxanes was prepared by the traditional threading method, while it was later found that the b-cyclodextrin [2]-rotaxanes could also be prepared by a slow slippage of the cyclodextrin over a Co(III)-blocked axle.
N N NH NH H2N 3+ C C C C NH2 Co Co3+ H2N OH2 H2O NH2 H2O H2O b-cyclodextrin
Figure 1: One of a series of cyclodextrin [2]-rotaxanes with Co(III) blocking groups prepared
The synthesis of other examples of Co(III)-blocked [2]-rotaxanes in DMSO has been reported, but low yields were obtained, as the hydrophobic driving force for formation of the [2]- pseudorotaxanes was absent.[1,2] A considerable advantage in the current preparation of [2]- rotaxanes is the high water solubility of the axles, such that all blocking group attachment reactions may be carried out in water.
[1] H. Ogino, J. Am. Chem. Soc. 1981, 103, 1303-1304.
[2] K. Yamanari, Y. Shimura, Bull. Chem. Soc. Jpn., 1983, 56, 2283-2289.
IC-03 February 2-6, 2003 Melbourne 38 Photoactivated Ligand Release From Cobalt (III) Anthrylmethyl Cyclam Derivatives Simon Boyd, Kenneth P. Ghiggino, W.David McFadyen School of Chemistry, University of Melbourne, 3010, Victoria, Australia [email protected] The photoinduced energy and electron transfer properties of chromophore – macrocyclic transition metal complexes are of considerable interest because of the potential use of these compounds as photomolecular devices for a range of applications including sensitive metal ion sensors [1] and molecular switches of fluorescence [2]. One potentially exciting application, to date unrealized, is the photoactivated release of a monodentate ligand into solution from the complexed transition metal 1. Such a process would require the system to be kinetically inert to ligand exchange in its ground state but would require the formation of a temporary labile species upon absorption of a photon. Towards this end we have isolated and structurally characterized a range of donor-acceptor systems containing anthracene as the chromophore, appended via a
methylene bridge, to the N4 quadridentate ligand cyclam encapsulating the octahedrally coordinated CoIII ion 2. Attached to the kinetically inert metal are two axially coordinated - - - monodentate ligands (X ). The systems investigated to date include the simple ligands Cl , NO2 and NCS- for preliminary investigations into a possible photomediated ligand release process. The ligand exchange kinetics of these systems upon photoexcitation were monitored by observations of spectral changes in the ligand field region of these complexes and compared with those of their corresponding model complexes 3 containing no chromophore. The model complex 3 was found to undergo very efficient photoactivated ligand release. The
hv +
CARRIER LIGAND + X X X = Cl- 1 N NH NH NH
(NO2) 2 Co (III) Co (III) CARRIER * 3 (NCS) LIGAND NH NH NH NH
X X
photochemistry of these molecular systems will be outlined.
[1] Fabrizzi, L., Licchelli, M., Pallavicini, P., Perotti, A., Taglietti, A., and Sacchi, D., Chem. Eur. J., 1996, 2, 75 [2] Amendola, V., Fabrizzi, L., Licchelli, M., Mangano, C., Pallavicini, P., Parodi, L., and Poggi, A., Coord. Chem. Rev.., 1999, 190, 649
IC-03 February 2-6, 2003 Melbourne 39 A New Single Molecule Magnet: [Mn16O16(OMe)6(OAc)16(MeOH)3(H2O)3]?6H2O David J. Price, Stuart R. Batten, Boujemaa Moubaraki and Keith S. Murray School of Chemistry, Monash University, Victoria 3800, Australia [email protected]
Since it was discovered in 1993, that [Mn12O12(OAc)16(H2O)4]?2HOAc?4H2O (‘Mn12-acetate’) behaves as a discrete nanosized magnetic particle (nanomagnet or single molecule magnet, SMM), research in the field of polynuclear manganese carboxylate clusters has become widespread.[1] Synthetic and physicochemical studies made by Christou and Hendrickson et al.,[1] Gatteschi and Sessoli et al.,[2] and Powell et al.[3] on high nuclearity manganese and iron oxo/carboxylato cluster complexes have led to significant advances being made in the understanding of SMMs. In addition, some iron and vanadium clusters have been shown to display the characteristics peculiar to the SMM family.[4] Here we present a new member of this family,[5] the title compound or ‘Mn16-acetate’ (Figure 1).
IV 8+ The structure of the cluster can be divided into two sub-units, a central [Mn 6O6(OMe)4] unit III 2- - connected to an outer Mn 10 perimeter by ten m3-O ions and two two m-OAc groups. Peripheral ligation consists of the remaining fourteen m-OAc-, two m-OMe- groups and three axial water and methanol molecules.
The clusters are linked by hydrogen bonds involving adjacent lattice water molecules to form linear chains of clusters that propagate along the crystallographic c-axis direction. Detailed AC susceptibility studies were made as a function of frequency (50-1500 Hz) in the temperature range 2-10 K, and are discussed here. Figure 1. Mn16-acetate.
[1] G. Aromi, S. M. J. Aubin, M. Bolcar, A., G. Christou, H. J. Eppley, K. Folting, D. N. Hendrickson, J. C. Huffman, R. Squire, C., H.-L. Tsai, S. Wang, and M. W. Wemple, Polyhedron, 1998, 17, 3005. [2] A. Caneschi, D. Gatteschi, C. Sangregorio, R. Sessoli, L. Sorace, A. Cornia, M. A. Novak, C. Paulsen, and W. Wernsdorfer, J. Magn. Magn. Mater., 1999, 200, 182.
[3] A. K. Powell, Struct. Bonding, 1997, 88, 1.
[4] G. Christou, D. Gatteschi, D. N. Hendrickson, and R. Sessoli, Materials Research Society Bulletin, 2000, 25, 66.
[5] D. J. Price, S. R. Batten, B. Moubaraki, K. S. Murray, Chem. Commun., 2002, 762-763.
IC-03 February 2-6, 2003 Melbourne 40 Charge-Transfer in Fluorescent Ferrocenium Dyads
C.John McAdam, Amar Flood, Brian H. Robinson and Jim Simpson Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand [email protected]
A number of dyads containing pendant -CºCFc or –C=CFc groups linked to aromatic or heteroaromatic fluorophores have been synthesized and their electronic structure investigated. For the majority of the neutral dyads there is no evidence for electronic communication and charge transfer between the ferrocenyl moiety and fluorophore. In contrast, the oxidised species display characteristic low-energy bands in their near-IR spectra attributed to fluorophore ® Fc+ CT transitions. We will explore the origin of these transitions, their solvent behaviour and the dependence on the linking group. Because the fluorescence is redox-dependent these dyads are molecular switches.
Figure 1 Changes in the UV/visible spectrum during oxidation of a dyad.
IC-03 February 2-6, 2003 Melbourne 41 Substituted-Pyridine Complexes of Molybdenum Carbonyl - Electrochemistry and Electronic Spectra Franz Wimmer and Aroseta Jait Department of Chemistry, Universiti Brunei Darussalam, Gadong BE1410, Brunei. [email protected]
Coordination of 2,2'-bipyridine (bpy, 1) has a dramatic effect on its electrochemistry, shifting the + one-electron reduction step (E1/2 -2.57 V vs FeCp2/FeCp2 ) to a more positive potential. At the same time, coordination gives rise to a metal-ligand charge transfer band in the visible region of the electronic spectrum, the energy of which frequently displays a marked dependence on the polarity of the solvent.
The question arises: for this change in properties is it necessary to chelate the bpy? We explored the effect of monodentate coordination by using the structurally-similar phenyl-pyridines (2-, 3-, 4-phpy, 2 - 4) and 4-phenylpyrimidine (5) (L)
N
N N N N N N 1 2 3 4 5 in place of bpy and prepared the complexes [Mo(CO)5(L)] and cis-[Mo(CO)4(L)2].
We report the electrochemistry and electronic spectra of these complexes and compare them with those of [Mo(CO)4(bpy)].
In summary, in contrast to [Mo(CO)4(bpy)] (E1/2 -1.98 V) the reduction potential of the monodentate ligands is little affected by coordination to Mo(0), similarly the electronic spectra display little solvent dependence.
IC-03 February 2-6, 2003 Melbourne 42 Structural and Functional Models for the Hydrogenase Enzyme Active Sites
Thomas B. Rauchfuss Department of Chemistry, University of Illinois at Urbana-Champaign [email protected]
Abstract: The hydrogenase enzymes catalyze the interconversion of protons and dihydrogen and feature Fe-S-CN-CO or Ni-Fe-S-CN-CO cores. Interest in these enzymes stems from the unusual structural features of their active sites, which display ligands that are novel in biology. Of course the hydrogenase reaction itself is of fundamental interest due to its simplicity and potential relevance to the design of catalysts for fuel cells. The presentation will survey the evolution of models starting from the simplest iron-cyano- hydrides to include bimetallic derivatives that catalyze proton reduction at an electrode. New iron cyanide and iron thiolate chemistry will be presented, including recent work on the isonitrile derivatives that bear a striking structural resemblance to the Fe-only active sites. Overall the area of hydrogenase modeling illustrates a new way by which organometallic chemistry contributes to problems in biology.
Leading references: “New Class of Diiron Dithiolates Related to the Fe-Only Hydrogenase Active Site: 2+ Synthesis and Characterization of [Fe2(SR)2(CNMe)7] ” Lawrence, J. D.; Rauchfuss, T. B.; Wilson, S. R., Inorg. Chem. 2002, 41, 6193-5. "Bimetallic Carbonyl Thiolates as Functional Models for the Fe-only Hydrogenases”, Gloaguen, F.; Lawrence, J. D.; Rauchfuss, T. B.; Bénard, M.; Rohmer, M.-M., Inorg. Chem. 2002, 41, 6573-82. "Iron Carbonyl Sulfides, Formaldehyde, and Amines Condense to give the Proposed Azadithiolate Cofactor of the Fe-only Hydrogenases", Li, H.; Rauchfuss, T. B., J. Am. Chem. Soc. 2002, 124,726-727.
IC-03 February 2-6, 2003 Melbourne 43 Metallaboratranes: Metal®Boron Dative Bonding Alison J. Edwards,a Anthony F. Hill,a,b Elizabeth R. Humphrey,a Mark R. St.-J. Foreman,b Horst Neumann,a Gareth R. Owen,b Never Tshabang,a Andrew J. P. White,b David J. Williamsb and Anthony C. Willisa a Research School of Chemistry, Australian National University, ACT 0200, Australia b Imperial College of Science, Technology and Medicine, London SW7 2AY, U.K. [email protected] The classical coordination chemistry of transition metals involves an ensemble of electron pair donors coordinated as ligands to a Lewis acidic metal centre. The possibility that metal centres could act as electron pair donors to electrophilic boron(III) centres has long been postulated although no examples of such complexes had been structurally characterised prior to our recent report of the complex [Ru{(mt)3B}(CO)(PPh3)] (Ru®B) (mt = methimazolyl) [1]. This complex, a ruthenaboratrane, involves a transannular dative bond from ruthenium(0) to boron(III), within a bicyclo [3.3.3] cage structure, by loose analogy with the more familiar boratranes
N(CH2CH2O)3B (N®B) This lecture will address attempts to broaden this class of compound, including the complexes
[M{(mt)3B}L2] [ML2 = Os(CO)(PPh3), RhCl(PPh3),
Ru(CO)(CNCMe3), Ru(CS)(PPh3), and Ru(CO)(PR3) for R = Me (shown above), Cy, OEt, OPh] and to elucidate the mechanism of metallaboratrane formation. The key reagent in the preparation of these
metallaboratranes is the salt Na[HB(mt)3]. In addition to metallaboratrane formation, reactions of this salt with organometallic compounds will be discussed
wherein the HB(mt)3 ligand remains intact, thereby providing a conceptual bridge between the more
familiar ligands HB(pz)3 (pz = pyrazolyl) and 1,4,7- trithiacyclononane. The discussion will cover synthetic routes to HB(mt)3 complexes ligated by thiocarbamoyl, hydride, arene, stannyl, nitrosyl, allyl, thiocarbamoyl, alkene, alkyne, isonitrile or alkylidyne ligands (shown for [W(ºC-CºCCMe3)(CO)2{HB(mt)3}] \).
[1] A.F. Hill, G. R. Owen, A. J. P. White and D. J. Williams, Angew. Chem., Int. Ed. Engl., 1999, 35, 2759.
IC-03 February 2-6, 2003 Melbourne 44 Structure and Reactivity of Mono- and Bimetallic Chiral Amides Philip C. Andrews, Simone Calleja, Peter J. Duggan, Angelo D’Elia, and Melissa Maguire School of Chemistry, Monash University, PO Box 23, Melbourne, Vic 3800, Australia
[email protected] Chiral metal amides have become extremely important in the formation of many biologically active compounds, including b-amino acids and b-lactams [1]. In approaching the rational use of such highly selective reagents we have been investigating the structural chemistry of a series of secondary group 1 amides derived from (S)-a-methylbenzylamine. We have previously established that varying the metal can cause important intramolecular changes in the amide moieties, eg 2-aza-allyl formation [2].
Of recent interest has been the synthesis and structural characterisation of the mono- and bi- metallic complexes which can be obtained on metallation of (S)-N-(a-methylbenzyl)allylamine, 1, with group 1 organyls, and the structural diversity which can arise[3]. Several homo- and hetero- bimetallic complexes and have now been structurally determined through single crystal X-ray diffraction and multinuclear NMR studies and will be presented.
N 1 H
nBuLi / tBuLi
N Li Li
We have also recently established that the simple sodium amide, formed on reaction of nBuNa with (S)-N-(a-methylbenzyl)allylamine in the presence of tmeda, undergoes a sigmatropic rearrangement to an enamide[4]. The implications of this transformation in conjugate addition reactions will be discussed.
[1] For example; S. G. Davies and G. D. Smyth, Perkins Trans. I, 1996, 2467. S. G.Davies and O. Ichihara, Tetrahedron: Asymmetry, 1996, 7, 1919.
[2] P. C. Andrews, P. J. Duggan, G. D. Fallon, T. D. McCarthy and A. C. Peatt, Dalton. Trans., 2000, 1937.
[3] P. C. Andrews, S. M. Calleja and M. Maguire, Dalton Trans., 2002, 3640.
[4] P. C. Andrews, S. M. Calleja, M. Maguire and P. J. Nichols, Eur. J. Inorg Chem., 2002, 1583
IC-03 February 2-6, 2003 Melbourne 45 From Obscurity to Actuality: New Developments in the Organometallic Chemistry of the Heavy Alkaline Earth Metals
Karin Ruhlandt-Senge, Jacob Alexander and Ulrich Englich Department of Chemistry Syracuse University Syracuse NY 13244-4100, USA
[email protected] While the chemistry of organomagnesium derivatives has received significant attention, the organometallic chemistry of the heavier alkaline earth metals is not well understood. In the early 1900's efforts to synthesize organometallic calcium, strontium and barium compounds resulted in the formation of unstable and/or sparsely soluble compounds with little or no opportunity to be utilized in synthetic applications. It was only recently, that the unique role of heavy alkaline earth organometallic compounds in synthetic applications, in polymer chemistry, the semiconductor and computer industry became evident, but difficulties developing reproducible synthetic routes towards the target compounds prevented further progress in this area [1].
Research in our group have been focussed on developing straightforward, economic synthetic routes towards the target compounds and characterize the target molecules by a variety of spectroscopic techniques and X-ray crystallography. Theoretical calculations shed light on the bonding characteristics in the target compounds.
This talk will highlight some recent developments in the area of organometallic calcium, strontium, and barium chemistry, including the development of facile and reliable synthetic routes to the target compounds, and first structural data. We will discuss the capacity of certain ligand systems to stabilizing the charge on the organometallic ligand fragment, and examine of the metal- carbon bond characteristics of the target compounds. The development of synthetic routes and the examination of structure -function relationships will provide the necessary information to improve the performance and utility of existing applications, while establishing a new branch of organometallic chemistry with significant growth potential.
______1) Alexander, J. S., Ruhlandt-Senge, K. Eur. J. Inorg. Chem. 2002, 761.
IC-03 February 2-6, 2003 Melbourne 46 Modified Calix[4]pyrroles Designed to Improve Coordination Sphere Control of Lanthanide Metals: Synthesis of Sm(II) and Sm(III) Complexes F. Geoff N. Cloke,a Michael G. Gardiner,b Brian W. Skelton,c Wolfgang Scherer,d Jun Wang,b Allan H. Whitec a The Chemistry Laboratory, The University of Sussex, Brighton BN1 9QJ United Kingdom b School of Chemistry, University of Tasmania, Private Bag 75, Hobart TAS 7001 Australia c Chemistry Department, University of Western Australia, Crawley WA 6009 Australia d Inst. Anorg. Chem., Tech. Uni. München, Lichtenbergstr. 4, 85747 Garching Germany [email protected] Calixpyrroles or porphyrinogens, 1, have recently found applications in various fields, including anion binding [1] and organometallic chemistry.[2,3] We have adapted these accessible macrocycles for the preparation of mononuclear complexes of lanthanide R R R R N metals using the known calixpyrrole 2,[4] and related furan system 3. This H research forms part of our broader research program of better utilising NH HN H heterocyclic aromatic anions as alternatives to more established multihapto- N 1 R R hydrocarbyl ligand systems, such as cyclopentadienyls and pentalendiyls. R R
The conformational restrictions of the macrocycles 2 and 3, when hosting R R R R N large radii metals within the cavity, are the dominant features that bring Me about the desired structural features in the complexes isolated to date. The N N Me typical structural motif that we have observed features h1: h5: h1: h5-binding N 2 R R of the metal. The significant difference R R R R between the two ligand systems is that the R O R trans-N,N'-dialkylated calixpyrroles are N N effective in blocking one face of the macrocycle from binding a second metal O 3 R R R R within the cavity. This is shown in the structure of the Sm(II) complex of 2 (on right). Sm(III) halide, alkyl and amide complexes have also been prepared and characterised by NMR and crystal structure determination. The structure of the bis(trimethylsilyl)amide complex is shown (below). The distortion of the amide ligand in this structure offers promise that the Sm(III) centre will have good reactivity in various synthetic transformations, which we are currently pursuing. Overall, we have shown that the dianionic modified calix[4]pyrroles provide a well-defined coordination environment for lanthanide metals, which is improved on the unmodified tetraanionic macrocycle.
[1] P.A. Gale, J.L. Sessler and V. Král, Chem. Commun., 1998, 1. [2] C. Floriani, Chem. Commun., 1996, 1257. [3] T. Dubé, S. Gambarotta and G.P.A. Yap, Organometallics, 2000, 19, 817. [4] Y. Furusho, H. Kawasaki, S. Nakanishi, T. Aida and T. Takata, Tetrahedron Lett., 1998, 39, 3537.
IC-03 February 2-6, 2003 Melbourne 47 Manganese Superoxide Dismutase In Reduced And Oxidised Forms At Ultra-High Resolution (0.90 Å): Where Are The Hydrogens And What Are They Doing? Geoffrey B. Jameson,a James W. Whittaker,b Ross A. Edwards,a Edward N. Bakerc and Bryan F. Andersona a Centre for Structural Biology, Institutes of Fundamental Sciences and Molecular BioSciences, Massey University, Palmerston North, New Zealand b Department of Biochemistry and Molecular Biology, Oregon Graduate Institute, 20000 NW Walker Road, Beaverton, OR 97006-8921, USA. c School of Biological Sciences, University of Auckland, Auckland, New Zealand [email protected]
-· The superoxide ion, O2 , is a toxic byproduct of aerobic lifestyles yet also a major component of mammalian defences against pathogens. All aerobes and many anaerobes contain superoxide -· dismutases that convert O2 to dioxygen and hydrogen peroxide (for removal by catalase and peroxidases):
3+ -· + + 2+ SOD-Mn + O2 + H à SOD(H )-Mn + O2 + 2+ -· + 3+ SOD(H )-Mn + O2 + H à SOD-Mn + H2O2 -· + Overall: 2 O2 + 2 H à O2 + H2O2 Superoxide dismutases are also important virulence factors of mammalian pathogens. The structures of wild-type (mostly oxidised) and reduced forms of the Y147F mutant of Mn-SOD from Q146A (H,L) Escherichia coli at 0.90 Å resolution provide unprecedented insight into the active site, in particular Y34A (F,A) into the location of hydrogen atoms in the vicinity of the metal centre. The solvent species coordinated to the MnII centre appears to be an hydroxide ion (not water). These results, combined with structural and functional studies on five active-site mutants (noted in parentheses in Figure)[1,2] and the superoxide Figure: The active site of iron and dismutases from archaeons Methanobacterium manganese superoxide dismutases. thermoautotrophicum and Pyrobaculum aerophilum, Structurally and functionally character- give insight into the redox tuning and metal ised mutations of the MnSOD from specificity exhibited by members of the closely Escherichia coli are noted in paren- homologous family of Fe and Mn SODs. theses.
[1] R.A. Edwards, M.M. Whittaker, J.W. Whittaker, E.N. Baker, and G.B. Jameson. Biochemistry, 2001, 40, 4622-4632. [2] R.A. Edwards, M.M. Whittaker, J.W. Whittaker, E.N. Baker, and G.B. Jameson. Biochemistry, 2001, 40, 15-27.
IC-03 February 2-6, 2003 Melbourne 48 {2Fe3S} - Assemblies Related to the Sub-site of All-iron Hydrogenase Mathieu Razavet, Zhen Cui, Simon J George, Xiaoming Liu and Christopher J Pickett Department of Biological Chemistry, John Innes Centre, Norwich, UK NR4 7UH Stacey J Borg and Stephen P Best School of Chemistry, University of Melbourne, 3010, Victoria, Australia
Site-differentiated {2Fe3S}- cores related to the sub-site of the H-cluster of all-iron hydrogenase 1 can be assembled using new dithiolate thioether ligands. Syntheses, structures and spectroscopy of di-iron complexes are described, including the first example of an {2Fe3S}- cyanide and the characterisation of a bridging carbonyl cyanide intermediate possessing key structural elements of the natural sub-site 2-6. Progress towards electrocatalysis of hydrogen evolution via artificial di-iron sub-sites will be described.
1. Y. Nicolet, B. J. Lemon, J. C. Fontecilla-Camps and J. W. Peters, Trends Biochem.Sci., 2000, 25, 138-143.
2. M. Razavet, S. C. Davies, D. L. Hughes and C. J. Pickett, Chem. Commun., 2001, 847-848.
3. M. Razavet, A. Le Cloirec, S. C. Davies, D. L. Hughes and C. J. Pickett, J. Chem. Soc.-Dalton Trans., 2001, 3551-3552.
4. M. Razavet, S. J. Borg, S. J. George, S. P. Best, S. A. Fairhurst and C. J. Pickett, Chem. Commun., 2002, 700-701.
5. S. J. George, Z. Cui, M. Razavet and C. J. Pickett, Chemistry: A European Journal, 2002, 8, 4037-4046.
6. M. Razavet, S. C. Davies, D. L. Hughes, J. E. Barclay, D. J. Evans, S. A. Fairhurst, X. Liu and C. J. Pickett J. Chem. Soc.-Dalton Trans., 2003, in the press.
IC-03 February 2-6, 2003 Melbourne 49 Structural models for motifs involved in biological metal-mediated H atom abstraction Christine J. McKenzie,a Frank Bartnik Larsen,a Martin Mortensen,a Lars Preuss Nielsen,a and Robert Scarrowb a Department of Chemistry, University of Southern Denmark, Odense Campus, 5230 Odense M, Denmark b Department of Chemistry, Haverford College, PA, USA. [email protected].
We have characterised reactive Fe and Mn species that may aid elucidation of putative biological H atom abstractions involving non-heme metal biosites and small metal-coordinated exogenous ligands.
- Mononuclear [M(III)-OH] M=Fe, Mn, species were generated using related N5 [1] and N4O ligands (depicted). These compounds model active Lipoxygenase (LOX) [M(III)-OH] M=Fe, Mn, motifs which abstract H atoms from lipid substrates. Mn(III) and Fe(III) hydroxides are rarely observed in simple coordination compounds due to their propensity to dimerise to give oxo-bridged compounds. The pentadentate ligand tunes O py py the iron spin state, and both high and low spin hydroxide N py N O Fe species were accessed. The high spin iron species is the N Fe N R OH R OH most accurate model for active Fe-LOX and a Fe-OH py py bond length of 1.89Å was determined by EXAFS. high-spin Fe(III) low-spin Fe(III)
Matched pairs of (hydr)oxo-bridged dinuclear complexes related by reductive addition or oxidative removal of H atoms have been prepared. As a partial model for water oxidation in photosynthesis we have reacted a hydroxo-bridged Mn complex 3+ H with tyrosine radical mimics and observed a metal-based one 2.098(6) O 1.913(6) electron oxidation accompanied by proton removal (=H atom LFeII 3.03(8) FeIIIL 2.952(1) abstraction). [2] An unprecedented unstable “diamond core” di- 2.042(7) O 1.875(6) µ-hydroxo bridged FeII-FeIII complex was structurally 2.12(10) H 1.905(12) characterised by X-ray crystallography (italics) and EXAFS
(bold). [3] It is related to a previously isolated, and H H O - H O II III more stable, µ-oxo-µ-hydroxo diiron(III) complex [4] Fe FeIII Fe FeIII O H O by the reductive addition of a H atom, however the H reaction depicted could not be observed directly.
[1] A. Hazell, C. J. McKenzie, L. P. Nielsen, S. Schindler and M. Weitzer, J. Chem. Soc., Dalton Trans, 2002, 310; L. Duelund, R. Hazell, C. J. McKenzie, L. P. Nielsen, H. Toftlund, J. Chem. Soc., Dalton Trans., 2001, 152. [2] K. B. Jensen, C. J. McKenzie and J. Z. Pedersen, Inorg. Chem, 2001, 40, 5066. [3] R. K. Egdal, A. Hazell, F. B. Larsen, C. J. McKenzie and R. C. Scarrow, J. Am. Chem. Soc. 2002, in press. [4] R. Hazell, K. B. Jensen, C. J. McKenzie and H. Toftlund J. Chem. Soc. Dalton Trans, 1994, 707.
IC-03 February 2-6, 2003 Melbourne 50
Models for the CuB–his-tyr centre of proton-pumping heme-copper oxidases Stephen B. Colbran, Sang Tae Lee, Michael N. Paddon-Row and Donald C. Craig School of Chemical Sciences, University of New South Wales, Sydney, NSW 2052, Australia [email protected] The heme-copper oxidase super-family comprises the terminal proteins in the respiratory electron transfer chains of aerobic organisms, from archae and bacteria to humans [1-3]. These membrane-spanning enzymes couple the reduction of oxygen to water to the one-way transport of protons — proton-pumping — across an inner bacterial or mitochondrial membrane, a process accounting for over half of the total energy of aerobic respiration. The proton pumping conserves the energy from oxygen reduction as a transmembrane proton gradient, which drives the subsequent synthesis of ATP.
The structures of heme-copper oxidases are now known to atomic resolution [1]. Reduction of oxygen is catalysed at the binuclear heme a3...CuB centre depicted in Fig. 1. The ligands bound to
CuB include a remarkable crosslinked histidine-tyrosine cofactor believed to be the donor of one of the four electrons required for cleavage of oxygen [2, 3]. The CuB–his-tyr centre and its surrounding amino acid residues, all of which are strictly conserved, are widely postulated to be the site of the proton pump ‘gate’ — the element that uses the free energy released by oxygen reduction to drive protons in one direction through the binuclear centre and across the membrane via proton-conducting channels within the enzyme. The mechanism remains poorly understood. Prominent amongst mechanistic proposals are so-called ‘histidine cycles’ wherein a histidine ligand cycles on and off CuB [2, 3].
This presentation will include: • Background results raising the possibility of a role for redox-linked binding of the his-tyr cofactor [3]. • Results from DFT calculations at a high level of theory performed to define the energetics of histidine substitution at the CuB centre and the role of the his-tyr crosslink. • A first widely applicable method for crosslinking imidazoles (histidines) to a Fig. 1. The heme a3…CuB–his-tyr centre of respiratory heme- copper oxidases (bovine enzyme numbering [1]). phenol that is appropriately substituted to prevent coupling reactions of the phenoxyl radical. • The first copper model-complexes to incorporate a crosslinked imidazole-phenol donor.
[1] S. Yoshikawa et al. Science, 1998, 280, 1723. [2] M. Wikström, Biochim. Biophys. Acta, 2000, 1458, 188 & Biochemistry, 2000, 39, 3515. [3] Z. He, S. B. Colbran, D. C. Craig, Chem. Eur. J. 2003, in press.
IC-03 February 2-6, 2003 Melbourne 51 Is There a Role for Palladium(IV) in Catalysis? Allan J. Canty School of Chemistry, University of Tasmania, 7001, Tasmania, Australia [email protected] Oxidation state +IV for palladium is often proposed for intermediates in organic synthesis and catalysis, and this field has been reviewed recently [1]. The most contentious proposals for Pd(IV) catalysis involve presence of phosphine ligands and/or aryl halide oxidation addition to Pd(II) centres. Most of the early development of organopalladium(IV) chemistry was concerned with oxidative addition reactions of alkyl halides or halogens to palladium(II) substrates and establishing the basic principles for this oxidation state [1]. Some of this material will be reviewed, followed by recent work aimed at developing model systems that are more directly related to proposed catalytic processes.
The preliminary development of a Pd(IV) phosphine chemistry will be described [2], together with an exploration of the formation of M(IV) complexes by addition of Ar+ to palladium(II) and platinum(II) using hypervalent iodine(III) reagents containing aryl-iodine bonds, IArPh(O3SCF3) IV [3]. Iodine(III) reagents promise new routes to Pt (alkyl)2R species [R = Ar or other groups with C(sp2)]. Studies of model systems for carbon-oxygen bond formation [4] will be described, in attempts to model the acetoxylation of arenes by acetic acid in the presence of Pd(II) and oxidising agents [5]. The synthesis of “pincer” systems, PtIV(N~C~N), will be described IV including Pt (N~C~N)(benzoate)3 and reactivity differences toward C-O bond formation in IV Pt(IV) complexes, e.g. Pt (N~C~N)Me(O2CPh)2 undergoes Me-O2CPh reductive elimination IV but Pt (N~C~N)Tol(O2CPh)2 does not undergo Tol-O2CPh reductive elimination. Proposals for the involvement of Pd(IV) in catalysis that look fairly secure will also be reviewed, e.g. using halogens and silicon-silicon bonds in oxidation of Pd(II) to Pd(IV) [6,7].
[1] A.J. Canty, Chapter II.4 in Handbook of Organopalladium Chemistry for Organic Synnthesis, Ed. E-I. Negishi, 2002, 189.
[2] A. Bayler, A.J. Canty, P.G. Edwards, B.W. Skelton, and A.H. White, J. Chem. Soc., Dalton Trans. 2000, 3325.
[3] A. Bayler, A.J. Canty, J.H. Ryan, B.W. Skelton, and A.H. White, Inorg. Chem. Commun., 2000, 3, 575.
[4] A.J. Canty, M.C. Done, B.W. Skelton, and A.H. White, Inorg. Chem. Commun. 2001, 4, 678-650.
[5] T. Yoneyama and R.H. Crabtree, J. Mol. Catal. A, 1996, 108, 35.
[6] M. Suginome and Y. Ito, J. Chem. Soc., Dalton Trans. 1998, 1925.
[7] R. van Belzen, H. Hoffmann, and C.J. Elsevier, Angew. Chem., Int. Ed. Engl. 1997, 36, 1743.
IC-03 February 2-6, 2003 Melbourne 52 Ferrocenyl-Substituted Dithiolene Complexes:
Near-IR Absorbers at Record Wavelengths.
R. W. Sanders and U. T. Mueller-Westerhoff Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060 [email protected]
Using the electron-donating properties of ferrocene, we can shift the near-IR absorption of the square planar d8 dithiolenes to very low transition energies.
1.0
0.8
0.6
0.4
0.2 Relative Absorbance
0.0
400 600 800 1000 1200 1400 1600 Wavelength (nm)
Fe S S Fe Fe S M S S Fe Ni S Fe S S
Fe 1
Solid line: tetraferrocenyl nickel dithiolene; dashed line: diferrocenyl nickel dithiolene
The spectral shifts upon addition of electron donating or withdrawing substituents at the distant Cp rings let us establish that the long-wavelength peak is the p?p* transition. A second peak around 750 nm and of comparable intensity is assumed to be a Fe ? p* transition. When full conjugation and coplanarity between ligand and dithiolene are achieved, extreme shifts into the 1700 nm region are observed.
IC-03 February 2-6, 2003 Melbourne 53 Unique Reactions of Heterocyclic Carbene Complexes: Important Ramifications for their Application in Catalysis Kingsley J. Cavell, Chemistry Department, Cardiff University, Cardiff, Wales, UK, CF10 3TB, [email protected] In studies on the reaction behaviour of transition metal complexes of N-heterocyclic carbenes (NHC’s) we have found that imidazolium salts/N-heterocyclic carbenes have a rich and somewhat unexpected chemistry. (Hydrocarbon)M-carbene complexes (M= group 10 metal) undergo an often facile reductive elimination reaction to generate imidazolium salts and zero valent metal.[1] On the other hand, imidazolium salts (and thiazolium) salts readily oxidatively add to M(0) complexes to form hydrido-M-carbene complexes.[2,3, 4]
Inasmuch as (hydrocarbon)M-ligand species are postulated as intermediates in essentially all hydrocarbon conversion reactions, to successfully exploit complexes of NHC’s as catalysts, it is important to gain a comprehensive understanding of the chemistry of these species, and by so doing overcome the potential limitations of the catalyst systems. For example, we have shown that controlling the reductive elimination reaction is a crucial factor in developing effective catalyst systems for chain growth reactions.[5]
The objective of our studies is to understand, and hence influence the reactions of the imidazolium salt/carbene couple. These studies have broad implications for the use of metal- carbene complexes in catalysis in general, and also for the use of imidazolium based ionic liquids as solvents. In this presentation our recent studies on the reactions of M(II) and M(0) carbene complexes will be described. Investigations into several processes in which metal- carbene complexes have been applied as catalysts will be discussed. Some thoughts on methods for preventing/limiting catalyst degradation will be outlined. These studies will be supported by experimental and theoretical data.
[1] McGuinness, DS, Cavell, K.J, Organometallics, 2000, 19, 4918; McGuinness, DS, Saendig, N, Yates, BF, Cavell, K.J, J.Am.Chem.Soc., 2001,123, 4029 [2] McGuinness, DS, Cavell, KJ, Yates, BF, Skelton, BW, White, AH, J.Am.Chem.Soc, 2001, 123, 8317 [3] Gründemann, S, Albrecht, M, Kovacevic, A, Faller, JW, Crabtree, RH, JCS Dalton Trans. [4] Duin, MA Nicolas D. Clement, Kingsley J. Cavell, and Cornelis J. Elsevier, Chem Comm, in press [5] McGuinness DS, Mueller W, Wasserscheid P, Cavell,KJ, Skelton, BW, White, AH, Englert, U, Organometallics, 2002, 21, 175
IC-03 February 2-6, 2003 Melbourne 54 An Electronic Structure Description of the cis-MoOS Unit in Models for Molybdenum Hydroxylase Active Sites Martin L. Kirk,a Nick Rubie,a Katrina Peariso,a Christian J. Doonanb, Charles G. Youngb, c and Graham N. George a The Department of Chemistry, The University of New Mexico, MSC03 2060 , 1 University of New Mexico, Albuquerque, New Mexico, 87131-0001, USA b School of Chemistry, University of Melbourne, 3010, Victoria, Australia c Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, P.O. Box 4349, MS 69 Stanford, CA 94309, USA [email protected] The xanthine oxidase (XO) family of mononuclear molybdenum enzymes catalyzes the oxidative hydroxylation of purines and simple aldehydes. Unlike other hydroxylases, members of the XO enzyme family utilize water as the source of oxygen incorporated into substrate. Furthermore, these enzymes produce rather than consume reducing equivalents. When fully oxidized (XOox), and as the ‘very rapid’ intermediate (XOvr), the active site possesses a catalytically essential terminal sulfido ligand oriented cis to a terminal oxo ligand. Therefore, understanding the synergystic roles of the oxo and sulfido ligands in both the oxidative and reductive 4 half reactions is of prime importance in 3.5 S1s dxy developing deeper mechanistic insight into 3 XO mediated enzymatic catalysis. 2.5 Currently debated mechanisms suggest a 2 S d role for the terminal sulfido as either a 1s xz,yz 1.5 proton or hydride acceptor following S1s dx2-y2 hydroxide attack on the purine nucleus. 1 However, these mechanisms do not Normalized Absorption 0.5 0 specifically consider the influence of the 2464 2466 2468 2470 2472 2474 2476 ground state wave function on the reactivity. Energy (eV) We have used small molecule analogues of Figure 1. Sulfur K-edge XAS data for the small molecule XOox and XOvr in order to understand the analogue complex TpPrMoVIOS(OPh) (TpPr = hydrotris(3,5- unique underlying electronic structure of the diisopropylpyrazol-1-yl)borate). The data clearly indicate 1+,2+ [MoOS] moiety and provide deeper that Mo-Ssulfido covalency is greatest in the Mo dxy orbital. insight into the mechanism of the Mo hydroxylases. This has been accomplished by employing a combined spectroscopic approach utilizing magnetic circular dichroism, electronic absorption, resonance Raman, and X-ray absorption spectroscopies. Furthermore, these spectroscopic studies have been used to effectively calibrate the results of detailed bonding calculations, providing deep insight into the nature of the catalytically competent XOox site. Here we will present our current understanding of the bonding in the cis-MoOS unit, as well as how the oxo and sulfido donors function to facilitate an orbitally controlled reaction mechanism.
IC-03 February 2-6, 2003 Melbourne 55 Molybdo-Enzyme Electrochemistry: from Redox Potentials to Biocatalysis Kondo-Francois Aguey-Zinsou,a Paul V. Bernhardta and Alastair G. McEwanb a Department of Chemistry, University of Queensland, Brisbane, 4072 b Department of Microbiology and Parasitology, University of Queensland, Brisbane, 4072 [email protected] Mononuclear molybdenum enzymes are found in all forms of life. In all known cases the Mo ion at the active site is bound by either one or two bidentate pterin-dithiolene ligands. The mononuclear Mo-enzymes fall into three distinct groups comprising the xanthine oxidase, sulfite oxidase and DMSO reductase families (below). The ligand ‘X’ in the DMSO reductase family is provided by a serine, cysteine or selenocysteine residue.
O O O S X O O O S S Cys NH O S S HN Mo S NH Mo HN Mo S NH2 HN S NH N S NH O N S N NH OH2 N NH H2N NH O O H2N O H2N NH O NH
Xanthine Oxidase Family Sulfite Oxidase Family DMSO Reductase Family Mo-enzymes perform a diverse range of oxygen transfer reactions on small organic or inorganic substrates. Despite the intense interest in the catalytic properties of Mo-enzymes, direct electrochemical responses from the active sites of these enzymes remained elusive for many years. Recently we have been successful in obtaining voltammetric responses from a number of Mo-enzymes under both non-turnover and catalytic conditions [1,2]. Here we shall present some of our work in this area, where we have applied protein film voltammetry to provide insight into electron and atom transfer reactions at the Mo active site. Experiments in the absence and presence of substrate have demonstrated that electroactivity is retained upon immobilization of the enzyme on a working electrode surface.
[1] K.-F. Aguey-Zinsou, P.V. Bernhardt, A.G. McEwan and J.P. Ridge, J. Biol. Inorg. Chem. 2002, 7, 879.
[2] K.-F. Aguey-Zinsou, P.V. Bernhardt, U. Kappler and A.G. McEwan, J. Am. Chem. Soc., 2003, in press.
IC-03 February 2-6, 2003 Melbourne 56 High Resolution EPR Spectroscopy: Advances, New Techniques and Applications to Metalloproteins and Materials Science Graeme R. Hansona a Centre for Magnetic Resonance, The University of Queensland, St. Lucia, 4072 Queensland, Australia [email protected]
During the last decade, there have been a significant number of new advances in EPR spectroscopy allowing both the electronic and geometric structure of metal centres in metalloproteins, transition metal ion complexes and materials science to be determined. From an experimental perspective, high resolution techniques such as: pulsed electron nuclear double (triple) resonance (END(T)OR), electron spin envelope modulation spectroscopy, two- dimensional techniques such as hyperfine sub level correlation spectroscopy (HYSCORE) in conjunction with orientation selective measurements allows the electronic and geometric (distance and orientation of nuclei from the metal ion) structure of metal centres to be determined. For more complex multi-atom clusters, nutation experiments allow the determination of the ground state spin state and pulsed electron electron double resonance (ELDOR) provides a simple means of determining the distance between metal centres, up to 80 Å and their relative orientation. Whilst multifrequency EPR has generally been limited to microwave frequencies in the range 1-35 GHz (L-, S-, C-, X-, K-, and Q-bands) high field/frequency (95-600 GHz) CW and pulsed EPR has enabled the examination of spin systems which were previously described as 'EPR silent'. For example Ni(II), Mn(III) and V(III) complexes where the zero field splitting is greater than the Q-band microwave quantum have been characterised. In conjunction with the latsest software (XSophe-Sophe-Xepr[1,2]) for the analysis of continuous wave and pulsed EPR and END(T)OR spectra, EPR spectroscopy is finally catching up with NMR as an indespensible tool for characterisng metal centres in metalloproteins, transition metal ion complexes and materials. I will desrcibe these advances and show their application in metalloprotein research and materials science.
[1] G.R. Hanson, K.E. Gates, C.J. Noble, A. Mitchell, S. Benson, M. Griffin, K. Burrage, K., "XSophe - Sophe - XeprView A Computer Simulation Software Suite for the Analysis of Continuous Wave EPR spectra", in EPR of Free Radicals in Solids: Trends in Methods and Applications, Shiotani, M.; Lund, A. (Eds.), Kluwer Press. In Press, 2002.
[2] M. Heichel, P. Höfer, A. Kamlowski, M. Griffin, A. Muys, C. Noble, D. Wang, G.R. Hanson, C. Eldershaw, K.E. Gates, K. Burrage, “XSophe-Sophe-XeprView Bruker's Professional CW-EPR Simulation Suite”, Bruker Report, 2000, 148, 6-9.
IC-03 February 2-6, 2003 Melbourne 57 From Simple Coordination Chemistry to Supramolecular Arrays
EC Constable, Department of Chemistry, University of Basel, 4056 Basel, Switzerland
Carbon is a boring element with only three coordination geometries and four coordination numbers. Metal ions exhibit coordination numbers from 1 to 12 and probably show every conceivable geometry for a given coordination number. The use of metal centres as building elements for supramolecular systems offers a greater diversity than single carbon centres and allows the option of working with both labile and non-labile systems, giving access to both kinetic and thermodynamic products.
IC-03 February 2-6, 2003 Melbourne 58 Lanthanide Oxyacids as Corrosion Inhibitors A. Battlea, T. Behrsing,b G. B. Deacon,b C. M. Forsyth,b M. Forsyth,c T. W Hambley a and S. Leary b a School of Chemistry, University of Sydney, NSW., 2006 b School of Chemistry and Centre for Green Chemistry and = School of Physics and Materials Engineering Monash University, Vic., 3800, Australia [email protected] The current technology for the protection of metals for coating applications and recirculated water systems relies heavily upon the use of chromates and nitrites. These inhibitors are now recognised to be harmful to human health and the environment and their use is being phased out and alternatives sought. The novel application of lanthanide oxyacids (which includes the phosphate and carboxylate ligands) has resulted in the development of several excellent inhibition systems for mild steel and aluminium. X-ray crystallographic studies of several interesting structures obtained in the current study are presented and discussed, including two rare examples containing tetravalent Ce. Corrosion inhibition data for selected inhibition systems is also presented.
Figure 1. Figure 2. Structure of the novel hexameric The intriguing 3-d network structure of - Ce6(µ3-O)4(µ3-OH)3(dpp)12, featuring {Ce(oda)3Na4(NO3)2}(oda = O(CH2CO2 )2) 4+ + three independent Ce atoms and an in which Na2(NO3) layers are connected to an oxo-hydroxo core of tridentate oxo Ce4+ cations through carboxylate bridging 2- and hydroxy O atoms, to which are via discrete Ce(oda)3 ions, resulting in a attached bidentate dpp (diphenyl spectacular 3-D network structure. phosphate) ligands.
IC-03 February 2-6, 2003 Melbourne 59
Chemistry Of Metalloalkynes. Reactions Of [{Ru(CO)2(h-C5H5)}2(m-CºC)].
Lindsay T. Byrne, Christopher S. Griffith, George A. Koutsantonis*, Brian W. Skelton and Allan H. White. Department of Chemistry, University of Western Australia, Crawley, Perth , Western Australia, 6009, Australia.
We have been pursuing the chemistry of dimetalloalkynes in an effort to understand their relationship to alkynes and how the metal substituents influence their reactivity. We have used alkyne metathesis routes to prepare dimetalloalkynes and have investigated their reactivity to other metal containing reagents. In this work we will provide details of the extension of the metathesis methodology to butadiynyl complexes.
R
C O C O CO CO M CC M M CC CC M
C C O C O C O O R The dimetalloalkynes will react with reagents containing early transition metals, particularly those of group 4. The synthesis and characterisation of the Ti(0) and Zr(0) “alkyne” adducts will be discussed. The reaction of these adducts, pictured below, with acids has given rise to a remarkable product whose mechanism of formation is still being investigated.
C O M M' C CO C O C M'
C
O
IC-03 February 2-6, 2003 Melbourne 60 Oxidation of copper(I) complexes in gold ore lixiviants based on thiosulfate Jay Blacka, Leone Spicciaa and D.C. McPhailb a School of Chemistry and Centre for Green Chemistry, Monash University, 3800, VIC, Aus. b Department of Geology, Australian National University, 0200, A.C.T., Australia [email protected] Renewed interest in the use of thiosulfate for leaching gold from low grade gold ores [1], as a benign alternative to cyanide, has shown a need for a better fundamental understanding of the chemistry of this process. In the process, a copper(II) tetrammine complex catalyses the oxidation of gold to gold(I) which then forms a complex with thiosulfate. The copper(II) complex, however, also catalyses the oxidation of thiosulfate increasing reagent consumption and making the process uneconomical. Understanding the complexes formed in the Cu(II)-Cu(I) catalytic cycle is important for optimising conditions for gold leaching. Following our recent
spectrophotometric study of speciation in the Cu(I)-S2O3-NH3-Cl system [2], this study has focussed on the oxidation of solutions of copper(I), the objective being to better understand reaction mechanisms and optimal conditions for regenerating the copper(II) tetrammine catalyst.
Our initial results show that the copper(I) complexes are resistant to oxidation by O2(aq) when
thiosulfate complexes with Cu(I). The oxidation of a copper(I) solution with a Cu(I)/NH3 ~ 100 (Fig. 1a) shows the formation of a reactive intermediate which absorbs at 275nm, and which
decays as the reaction progresses. Oxidation at a lower Cu(I)/NH3 ratio of 10 (Fig. 1b) shows the formation of a reactive intermediate at 215nm, which has yet to have been identified and is more resistant to oxidation. Further experiments at higher [Cu] are being conducted so that changes in the visible spectrum can be used to identify the Cu(II) complexes that form upon oxidation.
a) b)
Figure 1: Effect of ammonia on the oxidation of Cu(I) solutions containing chloride and thiosulfate. a) [NH3] = 23.3 mmolal; b) [NH3] = 2.3 mmolal.
[1] M.G. Aylmore and D.M. Muir, Min. Eng., 2001, 14, 135-174.
[2] J. Black, L. Spiccia and D.C. McPhail, Geochim. Cosmochim. Acta, 2002, 66(S1), A81.
IC-03 February 2-6, 2003 Melbourne 61 Nanomolar dissocation constants of the bisintercalating complexes of 4+ [(dpq)2Ru(phen-n-SOS-n-phen)Ru(dpq)2] (where n = 3, 4 or 5 and
SOS = -S-(CH2)2-O-(CH2)2-S-).
Craig Brodiea, Janice Aldrich-Wrighta, Edith Glazerb, Nathan Luedtkeb and Yitzhak Torb. aCollege of Science Technology and Environment, School of Science, Food and Horticulture, University of Western Sydney, Penrith South, NSW,1797, Australia. bDepartment of Chemistry & Biochemistry 0358, University of California, San Diego, La Jolla, CA 92093-0358, U.S.A. [email protected]
Interest in ruthenium(II) complexes over the past five decades has resulted in the synthesis of many mononuclear complexes used to probe DNA recognition. Their biological usefulness is however, limited by their relatively small size. Furthermore, their low cytotoxicity and modest DNA binding affinity limits the effectiveness of these compounds as chemotherapeutic agents. Bismetallointercalators are expected to overcome the limitations of mononuclear complexes because they to have the following advantages: they can span six to eight DNA bases increasing the possibility of sequence specificity, higher DNA binding affinity and much slower DNA- dissociation rates. It is expected that the increase in DNA binding affinity will afford an appreciable increase in the effectiveness of these complexes as potential chemotherapeutic agents. N N We report the interaction of [(dpq)2Ru(phen- N 4+ n-SOS-n-phen)Ru(dpq)2] (where n = 3, 4, 5, N N N N N Ru N N phen = 1,10-phenanthroline; dpq = N N N dipyrido[6,7-d:2',3'-f]quinoxaline and SOS = N 2-mercaptoethyl ether) (Figure 1) with DNA. dpq S Work so far indicates that the binding affinity
R that this complex exhibits will be up to 100 4 R5 O R3 times greater than the mononuclear S equivalent. Also the problem of low affinity N N N N at high ionic strengths previously shown for Ru N N N N mononuclear intercalators has been N N N N Ru N N overcome. As a result, biological activity N N N should be substantial and the complex will be N suited to in vivo conditions. We report the N 2+ N [Ru(dpq)2(3-Br-phen)] ; R3= Br, R4 & R5 = H synthesis and characterisation of each of the 2+ [Ru(dpq)2(4-Cl-phen)] ; R4= Cl, R3 & R5 = H 2+ 4+ dimeric complexes. Furthermore we have [Ru(dpq)2(5-Cl-phen)] ; R5 = Cl, R3 & R4= H [(dpq)2Ru(5-phen-SOS-phen-5)Ru(dpq)2] determined binding constants for the racemic Figure 1 The intercalator, dpq, the mononuclear complex, [Ru (dpq) (phen-X)]2+ (where X = Br or Cl) and the bis- form of each complex using fluorescence 2 intercalating complex [(dpq)2Ru(phen-5-SOS-5- 4+ spectroscopy and carried out DNA melting phen)Ru(dpq)2] (where SOS =2-mercaptoethyl ether). studies.
IC-03 February 2-6, 2003 Melbourne 62 Alternative leach reagents for the thiosulfate gold leaching process Tiffany Brown,a Leone Spiccia,a and D.C. McPhail b a School of Chemistry and Centre for Green Chemistry, Monash University, 3800, Victoria, Australia b CRC LEME and Department of Geology, Australian National University, Canberra, 0200, ACT, Australia [email protected] Thiosulfate leaching is a green alternative to the cyanide leaching process. Thiosulfate replaces cyanide, acting as a complexing agent for gold(I) formed following oxidation of native gold by a 2+ copper-ammonia catalyst. [Cu(NH3)4] greatly increases the rate of gold leaching. Unfortunately copper (also present in many gold ores) also catalyses the undesirable decomposition of thiosulfate to tetrathionates. The resulting costs associated with the replacement of thiosulfate reduce the economic viability of the thiosulfate leaching process.
Our research seeks alternative reagents to replace ammonia, the objective being to find a ligand which fills all the roles of ammonia, but also hinders the ability of the Cu(II) complex to catalyse the decomposition of thiosulfate. Early stages of this work have involved determining the rate of thiosulfate oxidation in the presence of alternative ligands, and estimating the potential of the solution as an estimate of gold leaching ability. This work is being followed by more detailed measurements of gold leaching ability.
In order to determine the rate of thiosulfate decomposition, changes in the UV-visible spectra of solutions of thiosulfate and copper(II)-ligand mixtures have been measured as a function of time. (figure 1a). Other studies[1] have identified that the reactions being followed result in the conversion of thiosulfate into tetrathionate. As the reaction proceeds, the d-d transition of the Cu(II) complex observed at ca. 600nm decreases in intensity, indicating the conversion of Cu(II) to Cu(I). The change in spectrum can be used as a measure of the rate of thiosulfate oxidation. (figure 1) A regular change in spectrum occurs immediately on mixing of the solution, observed as a new peak or shoulder at 300-350nm, indicating formation of a reactive intermediate, probably a copper-thiosulfate complex, which disappears as the oxidation reaction proceeds.
A number of ligands including pyridyls, polyamines, amino acids, picolinates and other functional groups have been investigated and their ability to effect the rate of thiosulfate decomposition, compared with that of ammonia. These studies have raised interesting questions about the mechanism of copper(II)-catalysed thiosulfate decomposition, Figure 1 Change in UV-visible spectrum following mixing and about how the structure and properties of 2+ of [Cu(NH3)4] and thiosulfate solution. 2+ the copper(II) complex affects the rate of Initial conditions: [Cu] = 0.01M, [NH3]= 0.3M, [S O 2-] = 0.1M, pH11, 30°C, Ionic strength = 2M. thiosulfate decomposition. 2 3
[1] J.J. Byerley, S.A. Fouda, and G.L. Rempel, J.C.S. Dalton, 1975, 1329
IC-03 February 2-6, 2003 Melbourne 63 Mechanism of Action of Platinum Complex Binding to DNA Genevieve H. Bulluss, Mark P. Waller and Trevor W. Hambley Centre for Heavy Metals Research School of Chemistry, University of Sydney, 2006, New South Wales, Australia [email protected]
Cisplatin (cis-[PtCl2(NH3)2]) is one of the most potent antitumour drugs currently in clinical use [1]. The precise mechanism of action of cisplatin is unknown, although much research has been done on the aquation and preassociation of the multistage process of binding to DNA [2].
In this work we have used theoretical and experimental techniques to uncover more information about these processes. The QM/MM hybrid method of ONIOM was adapted to investigate the sequence selectivity of cisplatin. The key step in this selectivity is believed to be the monofunctional adduct formation, proposed to be partially controlled by long-range electrostatic interactions. The correlation between experimentally determined rate constants and the electrostatic potential was investigated, specifically with respect to the preference for guanine over adenine in the monofunctional adduct formation. Electrostatic potential on the N7 500 0.6 0.20 Experimentally determined rates 400 0.5
0.4 300 0.3 (a.u.) 200 0.2
100 0.1 Experimental Rates Electrostatic potential N7 0 0 3'G(GG) 3'G (AG) 3'A (GA)
-0.20 Octamers
Figure 1. The electrostatic potential of the guanine Figure 2. Monofunctional rate formation and maximum molecule as a gradient (a.u.). negative electrostatic potential of the N7(G).
In the experimental study we have compared specifically the adducts formed by cisplatin and the diaquated form by reacting them each in stoichiometric amounts with three self-complementary 52-base-pair oligonucleotide duplexes. The oligonucleotides were designed to have only three d(GpG), d(ApG) or d(GpA) sites per strand separated from each other by non-target bases to allow only intrastrand binding to these sites. By varying the reaction conditions we were able to compare the binding preferences of cisplatin and its diaquated form for d(ApG), d(GpA) and d(GpG). HPLC and GF-AAS results were used to determine the adduct profile.
[1] B. Lippert, Ed., Cisplatin. Chemistry and Biochemistry of a Leading Anticancer Drug, 1999, Verlag Helvetica Chimica Acta: Zurich.
[2] T. W. Hambley, J. Chem. Soc., Dalton Trans., 2001, (19), 2711.
IC-03 February 2-6, 2003 Melbourne 64 Cobalt Complexes as Potential Radiation-Activated Anticancer Prodrugs John Y. Chang,a Penelope J. Brothers,a William A. Denny,b Clifton E. Rickard,a and David C. Ware a a Department of Chemistry, The University of Auckland, PO Box 92019, Auckland, New Zealand b Auckland Cancer Society Research Centre, The University of Auckland, PO Box 92019, Auckland, New Zealand. [email protected]
Prodrugs that respond exclusively to ionising radiation have the advantage of selective activation in the radiation field, therefore minimising damage to surrounding healthy cells. Also there is the potential of improving the effectiveness of radiotherapy when applied in conjunction. We have proposed a prodrug that is activated by a radiation-induced one-electron reduction mechanism. Cobalt complexes are candidates for such radiation- activated prodrugs. The prodrug is comprised of a metal complex in which a cytotoxic ligand based on a duocarmycin anticancer antibiotic is coordinated. A suitable ancillary ligand is chosen to complete the metal coordination sphere. Utilisation of a 12-membered cyclen macrocycle as the ancillary ligand allows stabilisation of the prodrug complex as well as limiting the number of possible isomers. In addition, the influence of the ring size on the reduction potential at the metal centre can be exploited for the optimisation of the radiolytic release. Cyclen analogues containing additional groups attached to the opposite nitrogens can vary other properties such as solubility and cell permeability.
Initial synthetic approach using 8-hydroxyquinoline as the model cytotoxin has been successful for the preparation of a series of model prodrugs, and a cobalt(III) complex containing coordinated cytotoxin has recently been prepared. Synthesis, characterisation, and electrochemical studies of the new complexes will be presented.
IC-03 February 2-6, 2003 Melbourne 65 Suppression of Reactivity by Product-Solvation: Synthetic Ramifications of 6 1 ? :? -Binding in Bulky Di(aryl)formamidinate Complexes of Potassium.
Marcus L. Cole,a Aaron J. Davies,a Cameron Jonesb and Peter C. Junka*
a School of Chemistry, Monash University, Victoria 3800, Australia. b Department of Chemistry, Cardiff University, P.O. Box 912, Cardiff, CF10 3TB, UK. [email protected] We recently reported the incomplete metallation of di(mesityl)formamidine using both potassium hydride and bis(trimethylsilyl)amide [1]. This suppressed reactivity is borne out of mesityl group steric inhibition and the provision of alkyl electron density to the aromatic core. These generate a highly stable ‘pseudo-metallocene’ ?6:?1-bound formamidinate-formamidine potassium moiety that exhibits extensive supramolecular hydrogen bonding in the solid state.
(1)
This work has been extended to other bulky di(aryl)formamidinates (e.g. di(2,6- diethylphenyl)formamidine; 1). These studies suggest the suppression of reactivity has finite boundaries [2]. Moreover, the attenuated reactivity of species like 1 has permitted the preparation of heterobimetallic formamidinate species with potential utility as superbases (2). These developments and the established ubiquity of the ‘metal-based’ bis(?6:?1-formamidinate) potassium anion will be presented.
(2)
[1]. J. Baldamus, C. Berghof, M.L. Cole, D.J. Evans, E. Hey-Hawkins and P.C. Junk, J. Chem. Soc., Dalton Trans., 2002, 2802. [2]. M.L. Cole and P.C. Junk, J. Organomet. Chem., 2002, in press.
IC-03 February 2-6, 2003 Melbourne 66
Synthesis and Crystal Structure of Porous Network Constructed from Self - assembly of Zinc(II) and 4-Pyrazolyl pyridine (Hpzpy) Yanyan Mulyana,a Leonard F. Lindoy,a Cameron C. Keperta and Peter Turnera a Centre for Heavy Metals Research, School of Chemistry, University of Sydney, 2006, NSW, Australia [email protected]
The construction of hybrid networks has developed rapidly over the years. Such molecular manipulation of ligands as building blocks and metal centres as connectors often results in porous networks capable of binding specific guest molecules. Here we report the synthesis and crystal structure of the new porous infinite network constructed from the self-assembly of zinc(II) and 4-pyrazolyl pyridine (Hpzpy).
In 1968, Bauer and co workers had synthesied a series of 4-pyrazolyl pyridinium salts [1], but their reaction was complicated. In the present work, Hpzpy has been made more conveniently by reacting 2-(4-pyridine) malonaldehyde, N N N N derived from 4-picoline, with hydrazine at room N temperature. Hpzpy is a 4,4’-bipy-like ligand 4,4'-bipyridine 4-pyrazolyl pyridine that has three donor atoms and hence three Figure 1. Directional arrangements for 4,4’-bipy directional arrangements could be possible. and pzpy
The first infinite framework of Hpzpy has been successfully made from its reaction with zinc(II) chloride. Colourless prismatic crystals grew in several days after mixing a stoichiometric amount of Hpzpy with zinc(II) chloride in aqueous ethanol at room temperature. The resulting complex [Zn(pzpy)(Cl)].2EtOH has been structurally determined by single crystal X-ray study. The complex forms a 2-dimensional infinite framework defining approximately square regions that each contains ethanol solvent molecules. The framework stacks to form solvent-containing channels sized approximately 14 Å.
Coordination of zinc(II) chloride leads to deprotonation of the Figure 2. 3D view of the pyrazol unit so as to form dinuclear tetrahedral complex units framework incorporating two pyrazol entities, two pyridine groups and two chlorides in each unit. Ethanol molecules are stabilized in the channels via hydrogen bonding with chloride anions.
Figure 3. Figure 4. Plane view of the Details of the dinuclear unit of the framework framework
[1] V.J. Bauer, H.P. Dalalian, W.J. Fanshawe, S.R Safir, E.C Tocus, C.R Boshart, J. Med. Chem, 1968, 11(5), 981-4
IC-03 February 2-6, 2003 Melbourne 67 Mechanistic Investigations into the Unprecedented meso to rac Isomerisation of some Bis-Planar Chiral Ferrocenyldiphosphines Owen J. Curnow,a Glen M. Fern,a Michelle L. Hamiltona and Elizabeth M. Jenkinsb a Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. [email protected] Ferrocenylphosphines continue to be extensively used in homogeneous catalysis; chiral derivatives are of particular interest for their asymmetric catalysis. The introduction of a chiral substituent or the generation of planar chirality is usually used to create the chirality. Despite the large number of planar-chiral ferrocenylphosphines that have been reported and used in asymmetric catalysis, no racemisation has been observed in these systems. Indeed, cyclopentadienyl complexes of iron are not known to undergo ring flip processes which would racemise the planar chiral centre. We recently communicated, however, the remarkable meso to rac isomerisation process, Figure 1, of the bis-planar chiral ferrocenyldiphosphine bis(1- (diphenylphosphino)-h5-indenyl)iron(II) complex which involves one ring flipping onto its other face [1].
Ph2P Ph P 2 THF Fe Fe PPh RT, overnight 2 PPh2 meso rac
There are a number of possible mechanisms for 60 this isomerisation and in this paper we will 50 report on mechanistic studies that have been done to rule out some of these. In particular, we 40 have carried out indenyl and phenyl labelling 30 experiments, solvent and salt effect Meso (%) 20 experiments, and volume of activation 10 experiments. We propose a likely mechanism 0 and discuss reasons for the preference for the 0 5 10 15 rac isomer over the meso isomer. Time (hours)
Figure 1. Percentage of the meso isomer as followed by 31P-NMR spectroscopy at various temperatures: 23 (top), 30, 40 and 50 °C (bottom).
[1] O. J. Curnow and G. M. Fern, Organometallics, 2002, 21, 2827.
IC-03 February 2-6, 2003 Melbourne 68
PYRAZOLATES CONTINUE TO AMAZE – THE NEW m-h2 : h1 BINDING MODE AND SPECTACULAR TRINUCLEAR HOMOLEPTIC COMPLEXES INCORPORATING m-h5 : h2 COORDINATION
G. B. Deacona, C. M. Forsytha, Alex Gitlitsa, R. Harikaa, P. C. Junka, B. W. Skeltonb and A. H. Whiteb
a School of Chemistry, Monash University, Victoria 3800, Australia bChemistry Department, University of Western Australia, Crawley, WA 6009, Australia
Despite the recent transformations of pyrazolate coordination chemistry by the discovery of a range of new binding modes[1-4] and by extension of h2-bonding from f-block elements[5] to early[6] and mid[7] d-block transition elements and main group metals,[8] surprising discoveries are still possible. This contribution describes synthesis and the unique structural features of trivalent homoleptic rare earth 3,5- diphenylpyrazolates. Direct reactions of a range of rare earth metals with 3,5-diphenylpyrazole (Ph2pzH) effected preparation of complexes with an empirical composition Ln(Ph 2pz)3 (Eq. 1). D Ln + n Ph pzH Ln(Ph pz) + n/ 2 H (Eq. 1) 2 Hg 2 n 2 Ln = Sc, La, Nd, Ho, Er
Displaying two structural discontinuities, this series is full of exciting architectural motifs. The most notable being the new m-h2 : h1 pyrazolate coordination [9] and the novel m-h5 : h2 binding observed for the first time in a trivalent rare earth complex and previously reported only for EuII [3a] and Ba[3b].
[1] J. R. Perera, M. J. Heeg, H. B. Schlegel, C. H. Winter, J. Am. Chem. Soc. 1999, 121, 4536; [2] G. B. Deacon, E. E. Delbridge, B. W. Skelton, A. H. White, Angew. Chem. Int. Ed. 1998, 37, 2251; [3] a) G. B. Deacon, A. Gitlits, P. W. Roesky, M. R. Bürgstein, K. C. Lim, B. W. Skelton, A. H. White, Chem. Eur. J. 2001, 7, 127; b) A. Steiner, G. T. Lawson, B. Walfort, D. Leusser, D. Stalke, J. Chem. Soc. Dalton Trans. 2001, 219.; [4] a) G. B. Deacon, E. E. Delbridge, C. M. Forsyth, B. W. Skelton, A. H. White, J. Chem. Soc. Dalton Trans. 2000, 745; b) C. Yélamos, M. J. Heeg, C. H. Winter, Inorg. Chem. 1998, 37, 3892; c) L. R. Falvello, J. Forniés, A. Martin, R. Navarro, V. Sicilia, P. Villarroya, Chem. Commun. 1998, 2429; d) J. Röder, F. Meyer, E. Kaifer, Angew. Chem. Int. Ed. 2002, 41, 2304; [5] a) C. W. Eigenbrot, Jr., K. N. Raymond, Inorg. Chem. 1981, 20, 1553; b) C. W. Eigenbrot, Jr., K. N. Raymond, Inorg. Chem. 1982, 21, 2653. [6] a) L. A. Guzei, A.G. Baboul, G. P. A. Yap, A. L. Reinhold, H. B. Schlegel, C. H. Winter, J. Am. Chem. Soc. 1997, 119, 3387; b) L. A. Guzei, G. P. Yap, C. H. Winter, Inorg. Chem. 1997, 36, 1738; c) C. Yélamos, M. J. Heeg, C. H. Winter, Inorg. Chem. 1999, 38, 1871; d) C. Yélamos, M. J. Heeg and C. H. Winter, Organometallics 1999, 18, 1168; e) N. C. Mösch Zanetti, R. Krätzner, C. Lehmann, T. R. Schneider, I. Usón, Eur. J. Inorg. Chem. 2000, 13; [7] K. R. Gust, J. E. Knox, M. J. Heeg, H.B. Schlegel, C. H. Winter, Angew. Chem. Int. Ed. 2002, 41, 1591. [8] a) D. Pfeiffer, M. J. Heeg, C. H. Winter, Angew. Chem. Int. Ed. 1998, 37, 2517; b) G. B.Deacon, E. E. Delbridge, C. M. Forsyth, P.C. Junk, B. W. Skelton, A. H. White, Aust. J. Chem. 1999, 52, 733; c) D. Pfeiffer, H. J. Heeg, C. H. Winter, Inorg. Chem. 2000, 19, 2377; [9] G. B. Deacon, C. M. Forsyth, A. Gitlits, R. Harika, P. C. Junk, B. W. Skelton, A. H. White, Angew. Chem., Int. Ed. Engl. 2002, 41, 3249.
IC-03 February 2-6, 2003 Melbourne 69 Catalytic Gas Phase Oxidation of Methanol to Formaldehyde
Tom Waters, Richard A. J. O’Hair, Anthony G. Wedd
School of Chemistry, University of Melbourne, 3010, Victoria, Australia
2- Electrospray Ionisation allows quaternary ammonium salts of the dimolybdate anion [Mo2O7] 2- to be transferred to the gas phase. The major ions observed are the dianion [Mo2O7] , protonated - + 2- - dimolybdate [Mo2O6(OH)] , and the ion pair {Bu4N [Mo2O7] } . A quadrupole ion trap mass spectrometer allows each of these ions to be trapped and their gas phase chemistry towards - neutral reagents to be explored. The protonated dimolybdate anion [Mo2O6(OH)] catalyses the gas phase oxidation of methanol to formaldehyde (Fig. 1):
CH3OH + CH3NO2 ® H2CO + H2O + CH3NO
The elementary steps of this catalysis have been investigated by variation of substrate alcohol (structure and isotope labelling) and by kinetic measurements. The role of the binuclear dimolybdate centre has been examined by variation of the metal (e.g Cr, Mo, W) and nuclearity (e.g mononuclear, binuclear) of the catalytic species.
The three reactions of this gas phase catalysis are equivalent to the three essential steps proposed to occur in the industrial oxidation of gaseous methanol to formaldehyde over molybdenum(VI)- trioxide solid state catalysts. A detailed molecular understanding of the mechanisms of this important industrial process seems elusive. Similarities between the present gas phase catalysis and the industrial process suggest the present study may shed light on important reactions and intermediates involved in the industrial process.
Figure 1: Gas phase catalytic cycle for the oxidation of methanol to formaldehyde
IC-03 February 2-6, 2003 Melbourne 70 Transition Metal Propargylidynes Rian Dewhurst, Alison J. Edwards and Anthony F. Hill Research School of Chemistry, Australian National University, ACT 0200, Australia [email protected] Group six metal propargylidynes, or alkynyl carbynes, have a rich organometallic chemistry involving conjugated CºC and MºC triple bonds. Stone and co-workers previously showed that metal alkynyl carbyne complexes with tripodal pyrazolyl borate ligands readily add low-valent metal fragments, making them ideal precursors to bi- and trinuclear metal complexes with different metals [1]. Regiocontrol of the metal fragment addition to either the carbyne or acetylenic linkage can be effected by altering the steric bulk of the co-ligands.
In this work, a range of new alkynyl carbyne complexes have been synthesised and isolated, and in some cases structurally characterised. All were isolated in a manner that has avoided the need for cumbersome low-temperature chromatography, notably [W(ºC-CºC-
SiMe3)(O2CCF3)(CO)2(bipy)] and [W(ºC-CºC-C-Me3)(O2CCF3)(CO)2(bipy)], which formed in excellent (>90%) yields.
The labile pyridine complex [W(ºC-
CºC-CMe3)(O2CCF3)(CO)2(py)2] has also been isolated and structurally characterised (shown above). This complex has allowed the synthesis of derivatives with a variety of ligand systems, such as the hydrotris(3,5- dimethylpyrazolyl)borate analogue, t [W(ºC-CºC- Bu)(CO)2(HB(dmpz)-
3)], where the loosely bound pyridine ligands and the anionic trifluoroacetate ligand are lost. However, reaction with (usually) bidentate pro-ligand potassium dihydrobis(3,5-dimethylpyrazolyl)borate gave only the hydrolysis product, [W(ºC-CºC-
CMe3)(O2CCF3)(CO)2(Hdmpz)2], where two 3,5-dimethylpyrazolyl groups have replaced the pyridine ligands.
[1] I.J. Hart, A.F. Hill, and F.G.A. Stone, J. Chem. Soc. Dalton Trans., 1989, 11, 2261-7.
IC-03 February 2-6, 2003 Melbourne 71 The Extraction of Heavy Metals from Polluted Sediments Using Chelating Agents Found in Commercial Softeners
Bin Fang,a Julia M. James,a Craig Barnesb and Leonard F Lindoya a School of Chemistry, University of Sydney, 2006, NSW, Australia b School of Geosciences, University of Sydney, 2006, NSW, Australia
The fate and transport of heavy metals in aquatic systems are of great concern because metal ions entrapped or stabilised in the sediments are vulnerable to re-release [1] through various interaction pathways such as extraction by complexing anionic ligands. Chelating agents are used for industrial and domestic purposes [2] because of their softening or masking properties. Many aminopolycarboxylic acids form strong and water-soluble complexes with most alkaline earth and heavy metal ions. Some of these chelating agents enter the wastewater and, if they are not eliminated in wastewater treatment plants, enter rivers. There are already significant levels of these chelating agents in European rivers [3]. As they are such strong metal complexing agents, there is potential for them to remobilise heavy metals trapped in contaminated sediments, releasing them back into the water column. Results will be reported for experiments that investigated the mobilisation of heavy metals from wet sieved contaminated sediments using individual ligands as well as mixtures. The ligands used were ethylenediaminetraacetic acid, nitrilotriacetic acid and diethylenetriaminepentaacetic acid, while experimental conditions were either anoxic or oxic. Conclusions will be drawn as to the ability of the above ligands to mobilise heavy metals from sediments and the conditions under which they will do so. ______[1] S.L. Lo, L.J. Huang, and C.F. Lin, Toxicol. Environ. Chem., 1994, 45(1+2), p. 69- 86 [2] B. Nortemann, Appl. Microbiol. Biotechnol., 1999, 51(6), p. 751-759 [3] F.G. Kari and W. Giger, Water Res., 1996, 30(1), p.122-34
IC-03 February 2-6, 2003 Melbourne 72 An Investigation of Ruthenium(II) Polypyridyl Complexes of the Intercalating Ligand Dipyrido[6,7-d:2'3'-f](6,7,8,9-tetrahydro)phenazine Warren Howard and Janice Aldrich-Wright aCollege of Science Technology and Environment, School of Science, Food and Horticulture, University of Western Sydney, Penrith South, NSW,1797, Australia [email protected]
2+ A series of ruthenium(II) polypyridyl complexes of the type [Ru(L-L)2dpqC] where L-L =
1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (Me2phen), 3,4,7,8-tetramethyl-
1,10,-phenanthroline (Me4phen), 2,2'-dipyridyl (bipy) or 4,4'-dimethyl-2,2'-dipyridyl (Me2bipy) were synthesised. The intercalating ligand of these complexes was dipyrido[3,2-d:2',3'-f](6,7,8,9- tetrahydro)phenazine (dpqC). The influence of methyl position, on the relative binding affinity on the aforementioned complexes, was assessed by in vitro transcription assays using the SP6 promoter, DNA equilibrium binding studies and DNA melting experiments. Equilibrium binding studies were performed to assess the binding affinity of these metal complexes to calf thymus DNA. These binding analyses utilised fluorescence and UV-Visible spectroscopy to ascertain the binding constant Kb and where possible the number of base pairs /binding sites. Thermal melting experiments were conducted to measure the extent to which these complexes stabilise the DNA duplex.
2+ This study also reports that [Ru(Me2bipy)2dpqC] displays enantiomeric cooperativity where the racemic form binds to DNA in a synergistic manner. Analysis of the fluorescence titrations revealed a convex curvature to the plots of r/Lf versus r (where r = Lb/[DNA]) that is commonly caused by aggregation of cooperatively binding molecules. The individual enantiomer, either D- or L- 2+ [Ru(Me2bipy)2dpqC] , shows a loss of cooperativity and a decrease in DNA affinity.
A relationship between ancillary ligand structure and DNA affinity has been established for these ruthenium(II) complexes containing phen, bipy and their methylated derivatives (Fig.1). This investigation also indicates that a trend Figure 1 The influence of methylated positions on DNA exists between DNA affinity and biological affinity activity.
IC-03 February 2-6, 2003 Melbourne 73 Fundamental studies of solar energy materials: vibrational spectroscopy and ab initio studies of 1,10-phenanthroline and its complexes. Sarah Howell,a Keith Gordona a Chemistry Department, University of Otago, Dunedin, New Zealand
[email protected] Polypyridyl complexes, such as those containing 1,10-phenanthroline (phen) (Fig 1), are widely used in areas such as solar cell devices.[1] An important feature of these complexes is the metal- to-ligand charge transfer (MLCT) that occurs upon excitation.[2] Structural changes that occur to the complex have implications to the excited state lifetime. Techniques which study these transient species and allow its species to be determined may allow the time-efficient screening of materials for use in devices such as solar cells. 2- D D D D N N D D N Ru N N N N N N N D D phen d8-phen 2- [Ru(CN)4(phen)]
Figure 1. Molecular structure of 1,10 phenanthroline (phen), the deuterated analogue (d8-phen) and the ruthenium 2- complex [Ru(CN)4(phen)] .
Ab initio calculations were used to calculate the structure of phen. From this the corresponding vibrational spectra were calculated. These were then compared to measured spectra. If the calculated and measured spectra match it can be assumed that the calculated structure is a good
representation of the real structure. The perdeuterated analogue, d8-phen was also examined to aid spectral interpretation. This procedure was repeated for the radical anion of the ligands. This is a good model for the MLCT excited state. Spectra of polypyridyl radicals can be difficult to 2- collect so time-resolved resonance Raman spectroscopy of [Ru(CN)4(phen)] was employed to provide a spectral signature of the radical anion. A good spectral match between calculated and experimental data would indicate that the calculated structure was similar to the real structure of phen.-. The structural change upon reduction can be established which has implications for the amount of structural change that occurs upon a metal-to-ligand charge transfer.
[1] For example: B. O’Regan, M. Grätzel, Nature, 1991, 353 737. [2] K. Kalyanasundaram, Modern Molecular Photochemistry, Benjamin/Cummings Publishing Company, Inc., California, 1992.
IC-03 February 2-6, 2003 Melbourne 74 Rhodium-based Coordination Chemistry of Poly(methimazolyl) Ligands Alison J. Edwards, Anthony F. Hill and Elizabeth Humphrey Research School of Chemistry, Australian National University, Canberra, ACT 0200. [email protected] The two ligand systems employed in this work are the dihydrobis(pyrazolyl)- and dihydrobis(methimazolyl) borates (Figure 1, (a) and (b), respectively).
H (a) H B(pz) H (b) H2B(mt)2 2 2 B B N N H N N N H N S N S N
Figure 1. The ligands H2B(pz)2 and H2B(mt)2 The coordination chemistry of these ligands towards rhodium(I) has been investigated for which purpose the complex [Rh2(m-Cl)2(COD)2] (COD = 1,5-cyclooctadiene) was found to be the most successful for preparing the complexes and their derivatives.
[Rh(COD){H2B(mt)2}] (shown left) was prepared and the crystal structure (shown left) was determined, revealing a B—H....Rh agostic interaction. The COD ligand can be replaced with neutral ligands (L) under mild conditions providing complexes of the type
[Rh(L)2{H2B(mt)2}] (L = CO, CNC6H3Me2-2,6)), which will be discussed. Attempts to similarly prepare the
corresponding CNCMe3 derivative resulted instead in
displacement of the H2B(mt)2 ligand to produce the + cationic complex [Rh(CNCMe3)4] .
Figure 2. [Rh(COD){H2B(mt)2}]
Adding K[H2B(pz)2] to a solution of [Rh(CNXyl)3Cl]
(formed in situ from [Rh2(m-Cl)2(COD)2] and
CNC6H3Me2-2,6) resulted in the new complex
[Rh(CNC6H3Me2-2,6)2{H2B(pz)2}].
New ligands have been prepared akin to the H2B(mt)2 ligand system by replacing the apical boron atom with arsenic or phosphorous which also have the potential to coordinate to a metal centre, for example the PhAs(mt)2 (mt = methimazolyl) ligand shown: Their synthesis and coordination chemistry will be discussed.
Figure 2. Ph-As(mt)2
IC-03 February 2-6, 2003 Melbourne 75 The Structure-Activity Relationship of Square-Planar Platinum(II) Metallointercalators David Jaramilloa, Craig Brodiea, J. Grant Collinsb Ronald R. Fentonc and Janice Aldrich- Wrighta a College of Science Technology and Environment, School of Science, Food and Horticulture, University of Western Sydney, Penrith South, NSW,1797, Australia. b Department of Chemistry, University College, (UNSW), Australian Defence Force Academy, Canberra 2600 c School of Chemistry, The University of Sydney, 2006, New South Wales, Australia
Square-metal complexes of the form [Pt(en)(L)]Cl2 (where L = 4-methyl-1,10-phenanthroline (4- MEPHE), 5-methyl-1,10-phenanthroline (5-MEPHEN), 4,7-dimethyl-1,10-phenanthroline (4,7- DMP), 5,6-dimethyl-1,10-phenanthroline (5,6-DMP) or 3,4,7,8-tetramethyl-1,10-phenantroline (3,4,7,8-TMP) and en = ethylenediamine) have been synthesized and a relationship between structure and biological activity correlated. The binding affinity, cytotoxicity and specific mode of binding determined through Circular Dichroism (CD) studies, IC50 experiments against L1210 cell lines, and DNA-NMR titrations, respectively, indicated that complexes that incorporated a methylated derivative of the 1,10-phenanthroline (phen) ligand exhibited a significant enhancement in biological activity over the parent compound [Pt(en)(phen)]Cl2. Within each methylated compound, it was also observed that substitution of the methyl group(s) at a specific position(s) on the aromatic ring influenced the overall binding mode and related biological activity.
Metal complexes appeared to show a particular site and groove preference when binding to DNA.
Intermolecular NOE cross-peaks Figure: Model of [Pt(en)(5,6-DMP)]Cl2 intercalated from the minor between each metal complex and groove of d(GTCGAC)2. For simplicity, only the T2 and C3 base pairs have been shown, since they constitute the actual binding site the oligonucleotide d(GTCGAC)2, at the T2-C3 site, demonstrated that each complex intercalates to the hexanucleotide from the minor groove.
Through the binding studies obtained a direct relationship was observed where increasing biological activity was related to increasing DNA binding strength and the residence time of the metal complex in the DNA.
IC-03 February 2-6, 2003 Melbourne 76
Calix-[4]-pyrroles: New Ligands From Old Hosts
XueKui (Erica) Ji*, David St. C. Black, Stephen B. Colbran, Gary. D. Willett School of Chemical Sciences UNSW SYDNEY 2052 [email protected]
The syntheses of a series of new calix-[4]-pyrrole derivatives, including the pyridine-substituted a-, aaab- and aabb-isomers of I–III, will be described. The isomers of I act as receptors for neutral organic guests and also bind metal ions. Selected X-ray crystal structures of the host-guest and metal-ligand complexes will be presented. All of the pyridyl-calix[4]pyrroles bind inorganic anions such as F-, Cl-, Br- and I- very strongly. Alkali and alkaline earth metal-cation binding selectivities have been determined in the gas phase for the ligand aaaa-I. Anion binding selectivities have been ascertained for ligand IV both in the gas phase by electrospray ionisation mass spectrometry (ESI-MS) and in solution by NMR titrations. Moreover, the mixed calix[4]pyrrole V has been efficiently isolated in 50% yield from the reaction of pyrrole with a combination of cyclopentanone and indanone. The facile preparative route to I–V suggests there is considerable scope for the new anion-and metal-binding calix[4]pyrroles.
2-PY N N
O N N O
O O I = 2-PY substituents H II = 3-PY substituents N III = 4-PY substituents NH NH CH3 H CH3 N
CH3 CH3
a,a,a,a-(2-PY)4-calix[4]pyrrole [a,a,a,a-I]
N N H H NH HN NH HN H H N N
IV V
IC-03 February 2-6, 2003 Melbourne 77 Beyond Transition Metal Amidinates: Highlights of the Coordinative Versatility of Formamidinates Toward Diverse Group 1 Metal Assemblies Marcus L. Cole,a David J. Evans,a Peter C. Junka* and Lance M. Louisb
a School of Chemistry, Monash University, Victoria 3800, Australia b Department of Chemistry, James Cook University, Townsville, Queensland 4811, Australia. [email protected]
The use of group 1 amidinate species, [M(R1NC(R2)NR1)], to prepare close-contact bimetallic ‘lantern-type’ transition metal complexes has been comprehensively studied. Recently, attention has swayed from traditional d-block systems to the utility of amidinates as ligands in main group metal based catalysis. Given the flexible geometric and steric constraints described by the less encumbered back-bone of formamidinates (R2 = H), it is perhaps surprising that these advances have been made in their absence. 2 1 The unusual µ2:? :? -binding mode of di(para-tolyl)formamidinate (FTolP) in
[{Li(FTolP)(Et2O)}2], which has no transition metal equivalent, and the highly ionic nature of group 1 amides suggests the chemistry of Group 1 formamidinates may possess structural diversity beyond d-block systems. To assess this we have embarked upon a detailed crystallographic study of Group 1 formamidinate complexes. This communication presents some outcomes of this initiative and includes the discovery of several hitherto unknown amidinate binding modes. These include ?6:?1-binding in bulky di(aryl)formamidinate complexes of potassium (1) [1], which affects suppressed formamidine deprotonation, and the 2 2 2 novel µ3:? :? :? binding of sodium di(ortho-fluorophenyl)formamidinate, which has been used to trap sodium fluoride (2) [2].
(1)
(2)
[1] J. Baldamus, C. Berghof, M.L. Cole, D.J. Evans, E. Hey-Hawkins and P.C. Junk, J. Chem. Soc., Dalton Trans., 2002, 2802. [2] M.L. Cole, D.J. Evans, P.C. Junk and M.K. Smith, Chem. Eur. J., 2002, in press
IC-03 February 2-6, 2003 Melbourne 78 Supramolecular Binding of Fullerenes to Porphyrins Peter D. W. Boyd and Steven M. F. Kennedy Chemistry Department, The University of Auckland, Private Bag 92019, Auckland, New Zealand [email protected]
Most covalently linked C60 moieties, in electron acceptor – donor dyads, suffer from reduced electron accepting ability in photoinduced electron transfer (PET) systems compared to pristine
C60. [1] A solution to this problem is to incorporate pristine C60 into PET systems supramolecularly, as opposed to covalently. It is fortunate that the ubiquitous electron donor chromophore – the porphyrin – is capable of molecular recognition of fullerenes. [2] Solutions containing one to one mixtures of fullerene and single porphyrin molecules spontaneously assemble into supramolecular stacks of alternating fullerene and porphyrin units, as illustrated in Figure 1a. [3] We have used parameters derived from studying the single crystal X-ray structures of these stacks to design, by computational force field methods, bis-porphyrin molecules optimised to bind the fullerene C60.
(a) (b)
Figure 1
The C60 and C70 fullerene binding properties of bis-porphyrin molecules, assembled from covalently linking two equivalents of the monoporphyrin 4-[10,15,20-tris(4-methylphenyl)- 21H,23H-porphin-5-yl]benzoic acid or 4-[10,15,20-tris(4-methylphenyl)-21H,23H-porphin-5- yl]phenol by such linkers as 1,2-diaminobenzene, as shown in Figure 1b, will be reported. The characterisation of the supramolecular complexes will be discussed and the bis-porphyrin- fullerene binding properties presented in terms of the binding constant, K.
[1] F. Diederich, and M. Gomez-Lopez, Chemical Society Reviews, 1999, 28, 263
[2] Y. Sun, T. Drovetskaya, R.D. Bolskar, R. Bau, P.D.W. Boyd, and C. A. Reed, J. Org. Chem., 1997,62, 3642. [3] P.D.W. Boyd, M.C. Hodgson, C.E.F. Rickard, A.G. Oliver, L. Chaker, P.J. Brothers, R.D. Bolskar, F.S. Tham, and C.A. Reed, J. Am. Chem. Soc., 1999,121, 10487.
IC-03 February 2-6, 2003 Melbourne 79
Synthesis and Structural Characterisation of Dinuclear Complexes of the Novel 1,2,4-Triazole-Based Ligands TsPMAT and PMAT Marco H. Klingele and Sally Brooker* Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand [email protected]
The 1,2,4-triazole moiety as part of ligand systems for first row transition metals has gained considerable attention in recent years. This is mainly because of the fact that its ligand strength is in the right region to give spin crossover compounds with iron(II) salts. Such compounds have potential applications in nano-technology. The 1,2,4-triazole unit is also of magnetochemical interest because it is able to act as a bridge between metal centres and mediate exchange coupling.
The novel bis-terdentate 1,2,4-triazole-based ligands
TsPMAT (1) and PMAT (2) have been synthesised (Fig. 1). Fig. 1. Schematic drawing of the While ligand 1 carries tosyl groups on N-2 and N-5, these novel ligands 1 and 2. have been replaced by hydrogen atoms in ligand 2. When reacted with an excess of hydrated metal(II) perchlorates or tetrafluoroborates, both ligands form dinuclear 2:2 complexes that show very similar overall architectures. There is, however, one striking difference between the two representative complexes 3 and 4. While in the cobalt-TsPMAT complex 3 the two II 4+ Fig. 2. Molecular structure of [Co 2(TsPMAT)2] (3). pyridyl arms of one ligand molecule coordinate to the two metal centres from the same side (Fig. 2), in the nickel-PMAT complex 4 they bind from opposite sides, one from above and the other one from underneath (Fig. 3).
Complex 3 is a very rare example of a coordination compound with secondary sulfonamide donors whereas primary sulfonamides are commonly found to act as donor atoms for metal ions. In fact, it is only the third structurally characterised example of this kind. The most remarkable feature of complex 3 is its stability and ease of Fig. 3. Molecular structure formation in spite of the secondary sulfonamides of ligand 1 being II 4+ of [Ni 2(PMAT)2] (4). only weak donors and not incorporated into a rigid macrocyclic framework.
IC-03 February 2-6, 2003 Melbourne 80 Exciting New Phosphanamide Chemistry
Marcus L. Cole, David J. Evans, Glen B. Deacon, Peter C. Junk, and Kristina Konstas School of Chemistry, Monash University, Clayton, Victoria 3800, Australia [email protected] Phosphanamides are interesting and unique ligands that possess relatively hard Lewis base (nitrogen) and a soft Lewis base (phosphorus) donors. Phosphanamines have the general formula R2PN(H)R', which can be deprotonated resulting in an anionic phosphanamide (Figure 1). R P N R' R Figure 1: Phosphanamide Treatment of phosphanamine ligands with lanthanoid metals and diarylmercury reagents in a redox transmetallation/ ligand exchange reaction should produce a lanthanoid complex (Equation 1).
Ln + 3LH + 3/2 HgR2 LnL3 + 3 RH + 3/2Hg Eq.1
Reacting Ln metal, Hg(C6F5)2 and LH (or LH2) in toluene under nitrogen yielded some interesting and unexpected mercury containing species as the only isolable products. The reaction between Nd, Hg(C6F5)2 and bis(diphenylphosphino)amine (Ph2PNHPPh2) yielded the first neutral subvalent triangular trimercury complex Hg3[µ2-(Ph2PNPPh2)4].3C7H8 as established by X-ray crystallography (Scheme 1 and Figure 2).
Hg(C6F5)2 + 2Ph2PNHPPh2 Hg(Ph2PNPPh2)2 + 2C6F5H
9Hg(Ph2PNPPh2)2 + 2Nd 3Hg3(Ph2PNPPh2)4 + 2Nd(Ph2PNPPh2) Scheme 2. Analogous reactions omitting the Ln metal afforded some highly unusual dinuclear mercuric complexes with chelating phosphanamide ligands, which were identified by X-ray crystallography.
Figure 2: Solid state structure
of Hg3[µ2-(Ph2PNPPh2)4].3C7H8
IC-03 February 2-6, 2003 Melbourne 81
Hazard and Risk Assessment of the Anti-valve Seat Recession Agent Methylcyclopentadienyl Manganese Tricarbonyl (MMT)
Graham Harvey, Debbie Willcocks, Jane Weder
National Industrial Chemicals Notification & Assessment Scheme, GPO Box 58, Sydney NSW 2001, Australia, www.nicnas.gov.au
The National Industrial Chemicals Notification and Assessment Scheme (NICNAS) is the Federal regulator of industrial chemicals in Australia. As well as assessing new industrial chemicals, NICNAS assesses the occupational health and safety, environmental and public health risks associated with existing chemicals under the Priority Existing Chemicals (PEC) programme.
Under the PEC programme, a number of anti-valve seat recession additives are being assessed including the manganese-based chemical methylcyclopentadienyl manganese tricarbonyl (MMT). Anti-valve seat recession agents are used as lead replacements in automotive fuels and act as valve lubricants preventing premature erosion of valve seats in internal combustion engines.
Presently in Australia, MMT is available either pre-blended in unleaded petrol at the oil refinery (lead replacement petrol) or purchased in aftermarket additives for addition to unleaded petrol by the vehicle owner. The assessed occupational, environmental and public health hazards and risks associated with the use of MMT are due both to the toxicity profile of MMT and but also to that of inorganic manganese species produced from MMT combustion. The main findings from the draft assessments will be discussed.
IC-03 February 2-6, 2003 Melbourne 82 Alkyne Exchange at Phosphenium Centres Nicola E. Brasch,a Ian G. Hamilton,a Elizabeth H. Krenskea and S. Bruce Wilda a Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia [email protected] Phosphirenium salts have recently been found [1,2] to engage in alkyne-exchange equilibria, which are unprecedented in main-group chemistry:
Et Ph Ph Et CDCl Ph 3 Ph 60 °C P P Me Me Ph Ph Ph Ph OTf OTf
Ab initio studies [3] of such reactions have identified a low-energy, single-step pathway involving rearside attack by the alkyne on the phosphirenium phosphorus, much like an SN2 process.
We have conducted a 1H NMR kinetic investigation of the reaction illustrated above and found, contrastingly, that the rate is independent of the concentration of alkyne. Moreover, the presence of free alkyne is not required for exchange to take place between two differently-substituted phosphirenium salts.
These results may be interpreted in terms of a mechanism that entails the slow initial release of an alkyne unit from the phosphorus atom to give a phosphenium ion, which rapidly combines with a second alkyne molecule.
[1] D.C.R. Hockless, M.A. McDonald, M. Pabel, and S.B. Wild, J. Chem. Soc., Chem. Commun., 1995, 257–258.
[2] D.C.R. Hockless, M.A. McDonald, M. Pabel, and S.B. Wild, J. Organomet. Chem., 1997, 529, 189–196.
[3] T.I. Sølling, M.A. McDonald, S.B. Wild, and L. Radom, J. Am. Chem. Soc., 1998, 120, 7063–7068.
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Processing of the same ligand using different coordination algorithms controls the molecular architecture of the resulting complex: grid versus side-by-side complexes Sally Brookera,*, Yanhua Lana, Dietmar K. Kennepohla,b, Boujemaa Moubarakic and Keith S. Murrayc aDepartment of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand bCentre for Science, Athabasca University, Athabasca, Alberta, Canada T9S 3A3 cSchool of Chemistry, Monash University, PO Box 23, Clayton, Australia
[email protected] The synthesis and characterisation of a pyridazine-containing two-armed grid ligand L1 (Figure 1) and the resulting transition metal (Mn, Fe, Co, Ni, Cu, Zn) complexes are reported. Single crystal X-ray structure determinations revealed that the copper(I) I complex had self assembled as a [2x2] grid, [Cu 4(L1)4](PF6)4 2 (Figure 2), whereas II II the [Zn 2(L1)2(H2O)2(CH3CN)2](ClO4)4(CH3CN)2 1, [Ni 2(L1)2(CH3CN)4](BF4)4 5 II and [Co 2(L1)2(H2O)2(CH3CN)2](ClO4)4 6 (Figure 3) complexes adopted a “side-by- side” architecture and iron(II) formed a monometallic cation binding three L1 ligands, II III III [Fe (L1)3][Fe Cl3OCl3Fe ](H2O) 7.
II In addition, a diamagnetic complex [Fe (L1)3](BF4)2.2H2O 8 was prepared, as well as I I derivatives of 2, [Cu 2(L1)2(NCS)2](H2O) 3 and [Cu 2(L1)(NCS)2] 4. The manganese II complex, [Mn 2(L1)2Cl4].3H2O 9, was not structurally characterised but is proposed to adopt a “side-by-side” architecture. The variable temperature magnetic susceptibilities were studied for the binuclear side-by-side complexes 5, 6, 9 and the diiron(III) anion of complex 7. Electrochemical investigations were undertaken for complexes 1, 2, 5 – 8. The structures and properties of this family of grid and side-by-side complexes will be presented and discussed.
IC-03 February 2-6, 2003 Melbourne 84
NMR Studies of CpRe(CO)2(cycloalkane) Sigma-Bond Complexes Douglas Lawes and Graham E. Ball School of Chemical Sciences, University of New South Wales, 2052, NSW, Australia [email protected] Sigma-bond alkane complexes, containing an essentially intact alkane molecule acting as a ligand, are thought to be an important intermediate in the oxidative addition of an alkane to a metal through the breaking of a C-H bond. Usually very short-lived, these species until recently have been characterised mainly with time resolved infrared or ultraviolet spectroscopy.
In 1997, Sun et. al [1] reported that the CpRe(CO)2(heptane) (Cp=cyclopentadienyl) was the longest lived alkane sigma-bond complex yet observed at room temperature, using time resolved infrared spectroscopy. Subsequent work in our group [2] was successful in observing the similar
CpRe(CO)2(cyclopentane) complex at 193K, using NMR spectroscopy. This poster describes our efforts to characterise an extended range of cycloalkane sigma-bond complexes CpRe(CO)2(cycloalkane) (cycloalkane=(CH2)n, n= 3 to 8) also using NMR. In addition, some unusual binding properties of cyclohexane are investigated, using carbon-13 and deuterium labelling experiments. Additionally, the technical nuances of acquiring spectra of short-lived species at low temperature, and the methods used to suppress solvent peaks, are discussed.
hv Re Re H CO C C Low Temperature, C cycloalkane solvent (CH2)n O C O O C CH
CH2 O O [1] X. Sun, D. C. Grills, S. M. Nikiforov, M. Poliakoff and M. W. George, J. Am. Chem. Soc., 1997, 119, 7521-7525.
[2] S. Geftakis and G. E. Ball, J. Am. Chem. Soc., 1998, 120, 9953-9954.
IC-03 February 2-6, 2003 Melbourne 85 Determination of Polyhydride Structure Using NMR Spectroscopy Xiaoyu Liu and Graham Ball School of Chemical Sciences, University of New South Wales, 2052, NSW, Australia
[email protected] The structure of polyhydrides have been traditionally determined by X-ray diffraction[1] and neutron diffraction until now. In X-ray diffraction, because of the low electron density of hydrogen atom, normally the hydrides can be difficult to locate and M-H distances may be underestimated by about 0.1 Angstrom. The instrumentation for neutron diffraction is quite expensive and quite often not available. This limits its usefulness. Until now, only a few metal hydride complexes have been accurately analysed by neutron diffraction[2]. In our project, we are using NMR techniques at low temperature to try to accurately determine polyhydride structure. The rhenium-ruthenium bimetallic pentahydride(1) used in the project was synthesized according to the literature procedure[1]. Some 1H NMR and 31P NMR experiments have been performed and the three bridging hydrides were found to undergo fluxional process. Chemical exchange rate for the complex have also been examined and the exchange rate predicted at -4 -1 173K is 7.2 x 10 s which mean at this H temperature the chemical exchange of the PPh3 complex is negligible. H H PPh3 Re Ru We are now trying to use 2D NMR techniques H CO PPh3 to get more information about its structure. PPh3 Some preliminary data have been obtained H from NOESY experiment. The relative (1) distances between hydrides were obtained Fig 1: bimetallic pentahydride, three bridging hydrides and two terminal hydrides from NOESY spectra at 173K. From the distances, we have now built up an arrangement of the hydrides relative to each other. Attempts are being made to locate the protons on the aromatic rings on PPh3 ligand and eventually the solution structure of the bimetallic complex will be built up with the aid of computer modelling.
[1] Z. He, S. Nefedov, and R. Mathieu, Organometallics, 1993, 12, 3837-3845
[2] M. Drabnis, S. Mason, and R. Ernst, Eur. J. Inorg. Chem., 1998, 851-854
IC-03 February 2-6, 2003 Melbourne 86 Formation of Osmium-Silicon and -Tin Metallacycles Guo-Liang Lu, Clifton E. F. Rickard, Warren R. Roper, L. James Wright Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand [email protected]
[1] When the five-coordinate stannyl-osmium complex, Os(SnMe3)Cl(CO)(PPh3)2 (1) , was heated in the presence of triphenylphosphine, two metallaspirocyclic complexes (2, 3) were formed. The structures of 2 and 3 were confirmed by spectroscopic as well as by X-ray crystallographic study.
Ph2P Ph2P PPh3 CO Ph3P Ph3P Os Os PPh3 / tolune Cl Os OC SnMe + OC SnMeCl reflux, 1h 2 SnMe3 Ph2P Ph2P PPh3
1 2 (17%) 3 (52%)
However, the silicon analogue, Os(SiMe3)Cl(CO)(PPh3)2 (4), did not undergo such a reaction but instead the Os-Si bond was cleaved to give the known ortho-metallated complex (5) [2].
PPh3 Ph2P CO PPh OC Cl Os 3 Os 160ºC, 1h Ph3P Cl SiMe3 PPh3 PPh3 4 5 (40%)
More interestingly, the related metallaspirocyclic complex (7), which had been previously [3] synthesized using OsHCl(CO)(PPh3)3 and Hg(SiMe3)2 , was obtained by heating the methyl- osmium complex, Os(SiMe3)(Me)(CO)(PPh3)2 (6), with triphenylphosphine.
Ph2P PPh3 CO Ph3P Os PPh3 / tolune Me Os OC SiMe reflux, 1h 2 SiMe3 Ph2P PPh3
6 7 (52%)
Further studies concerning the possible reaction mechanisms and other reactions of 3 and 6 will be described.
[1] P. D. Craig, K. R. Flower, W. R. Roper and L. J. Wright, Inorg. Chim. Acta, 1995, 240, 385. [2] M. A. Bennett, A. M. Clark, M. Contel, C. E. F. Rickard, W. R. Roper, and L. J. Wright, J. Organomet. Chem., 2000, 601, 299. [3] G. R. Clark, C. E. F. Rickard, W. R. Roper, D. M. Salter and L. J. Wright, Pure & Appl. Chem., 1990, 62, 1039.
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Manganese mediated reaction of conjugated a-heterodiene complexes with unsaturated compounds. Wade J. Mace, Brian K. Nicholson, Lyndsay Main, Daniel Van De Pas.
Department of Chemistry, University of Waikato, Hamilton, New Zealand [email protected] An investigation into the reaction of N-tolyl-3-phenylazabutadiene with
PhCH2Mn(CO)5 showed the azabutadiene to be a highly reactive substrate. The main product was the complex 1.
This probably proceeds via a cyclomanganated intermediate, which undergoes facile CO-insertion and cyclisation.
Reactions of the azabutadiene with benzylmanganesecarbonyl in the presence of unsaturated molecules such as PhCCH, PhNCO or CS2 gave a variety of novel heterocyclic products.
The cyclomanganated chalcone 2 reacts with alkyl halides to form substituted furanone and isofuranone compounds. The reaction appears to progress through a furanyl intermediate 3 analogous to the azabutadiene product above.
[1] W. Tully, L. Main, and B. K. Nicholson, J. Organometallic Chem., 1995, 503, 75.
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Electrochemistry of polyoxometalates in the ionic liquid [bmim][PF6]
Andrew W.A. Mariotti,a Alan M. Bondb and Anthony G. Wedda a School of Chemistry, The University of Melbourne, 3010, Victoria, Australia b School of Chemistry, Monash University, Clayton, 3800, Victoria Australia [email protected]
The room temperature ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate
[bmim][PF6] (Figure 1a) has been examined as an electrochemical solvent. Its intrinsic conductivity eliminates the need for supporting electrolyte.
No established reference electrode or reference potential calibration scale existed prior to this work. With an appropriate three electrode arrangement, the one electron reversible cobalticinium/cobaltocene redox couple can be used as a stable reference scale.[1] Furthermore, it was established that ferrocene in solution or the solid state can also be used as an alternative reference.
Having established a reference scale, the electrochemistry of the highly redox active 2- 4- 4- polyoxometalate anions [M6O19] , [SiM12O40] and [S2M18O62] (M = Mo, W) have been studied in [bmim][PF6]. Both solution and solid-state voltammetry were employed. The salts are not readily soluble, but either sonication or heat allowed dissolution and the salts remained in solution. Good electrochemical responses have been seen at room temperature despite the viscous nature of the liquid (Figure 1b). The wide cathodic limit allows the observation of more redox processes than in the usual organic solvents.
(a) (b)
6.00E-06
4.00E-06
2.00E-06 N N + - 0.00E+00 PF6 -2.00E-06 (Fc)
-4.00E-06
-6.00E-06 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 E (V) vs Fc+/Fc
Figure 1. (a) Structure of [bmim][PF6]. (b) Cyclic voltammogram of a-[TBA]4[SiMo12O40] (5 mM) in [bmim][PF6] at a Au working electrode, n = 100 mV s-1. Redox couple (Fc) is Ferrocene in the solid-state.
[1] Victoria M. Hultgren, Andrew W.A. Mariotti, Alan M. Bond and Anthony G. Wedd, Anal. Chem., 2002, 74, 3451-3156.
IC-03 February 2-6, 2003 Melbourne 89 Gas-Phase Studies on the Reactivity of (2,2’:6’,2’’-terpyridine)platinum(II) and (diethylenetriamine)platinum(II) Azido Complexes Sheena Wee, W. David McFadyen and Richard A. J. O’Hair School of Chemistry, University of Melbourne, 3010, Victoria, Australia [email protected] We have been examining the fundamental gas-phase ion chemistry of Pt(II) complexes ligated to 3 + tridentate ligands, such as tpy, dien and Me5dien. Recently, we showed that [Pt(L )N3] systems 3 3 + (where L = tpy, dien and Me5dien) fragment in the gas phase via loss of N2 to form [Pt(L )N] [1]. The ion [Pt(tpy)N]+ readily undergoes ion-molecule reactions in the presence of the neutral + reagents MeOH, MeCN and Me2CO, to yield adducts of composition [Pt(tpy)N+L] (where L =
MeOH, MeCN and Me2CO). In the case of the analogous dien complex, however, reaction did not occur with the above mentioned neutral reagents. We have recently also observed that unlike its tpy counterpart [2], the dien complex readily undergoes CID with the loss of NH3 and H2. To better understand the gas phase chemistry of these systems and the structural nature of the [PtL3N]+ complexes, we were motivated to more extensively examine the gas phase chemistry of + + [Pt(dien)N3] and [Pt(Me5dien)N3] . To assist in the elucidation of mechanistic details, we have 15 15 + prepared the labelled analogues of this complex -- [Pt( N,N’, N’’-dien)N3] {where 15N,N’,15N’’-dien = N,N-Bis[2-(15N-amino)ethyl]amine} and [Pt(N,N,N’,N’’,N’’-deuterated + 2 2 dien)N3] {where N,N,N’,N’’,N’’-deuterated dien = N,N-Bis[2-( H2-amino)ethyl]- H1-amine}. + In the study of the fragmentation of the labelled [Pt(dien)N] , it was found that the N of the NH3 lost from [Pt(dien)N]+ is the residual nitrogen of the azido ligand, not from the amino group of the dien ligand. The H’s of both the amino group and the carbon backbone of the dien ligand are + found to be acidic since the H’s of NH3 lost from [Pt(dien)N] originate from both the amino group and the carbon backbone of the dien ligand.
+ In addition, we have carried out a single crystal x-ray diffraction study of the [Pt(tpy)N3] and + [Pt(dien)N3] cations to furnish structural information for potential use in our ongoing study of the azido and related systems. The results of these investigations will be described.
[1] Styles, M. L., O’Hair, R. A. J., McFadyen, W. D., Tannous, L., Holmes, R. J. and Gable, R. W., J. Chem. Soc. Dalton Trans., 2000, 93-99;
[2] Wee S, Grannas M J, McFadyen W D, O’Hair R A J; Australian Journal of Chemistry, 2001, 54, 245.
IC-03 February 2-6, 2003 Melbourne 90 Intramolecular Electron and Energy Transfer in Bichromophoric Macrocycles Evan G. Moore,a Paul V. Bernhardt,a Mark J. Riley,a and Eric Vautheyb a Department of Chemistry, School of Molecular and Microbial Science, University of Queensland, St. Lucia, 4072, Queensland, Australia b Departement de Chimie Physique, Sciences II, University of Geneva, 30 Quai Ernest- Ansermet, CH- 1211 Geneva 4, Switzerland. [email protected] Photoinduced Electron Transfer (PET) and Electronic Energy Transfer (EET) has been demonstrated in a series of bichromophoric compounds (Fig. 1) which utilise a macrocycle as the bridge between various donor and acceptor fragments appended covalently via the exocyclic amino groups.
H H NH HN NH HN N N N N NH HN NH HN H H Fe L1 L2
H NH HN N N NH HN H
N L3
Figure 1 – Photoactive Ligands
In their free base forms, emission from the photoactive anthracene chromophore is reductively quenched by photoinduced oxidation of the proximate macrocyclic amine lone pairs. [1] Steady state measurements have shown the ligands are only weakly fluorescent in this form with excited state lifetimes on the nanosecond timescale determined by time resolved studies. The transient grating technique [2] has also been used to observe the anthracene radical anion generated upon excitation in these systems.
Complexation of Zn(II) within the macrocycle results in the deactivation of this PET pathway as the lone pair electron donors are no longer accessible. However, by the use of suitable donor acceptor combinations, intramolecular electronic energy transfer (L1 and L2) or photoinduced electron transfer (L3) between the pendant groups can be observed.
[1] Bernhardt, P.V.; Moore, E.G.; Riley, M.J., Inorg. Chem., 2001, 40, 5799.
1996 [2] Högemann, C.; Pauchard, M.; Vauthey, E., Rev. Sci. Instrum., , 67, 3449.
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- Synthesis and Characterisation of new Hybrid Spin-Crossover M(dca)3 Network Complexes. A Rare Lonsdaleite Structural Motif. Boujemaa Moubaraki,a Stuart Batten,a John Cashion,b and Keith Murray ,a a School of Chemistry, Monash University, PO Box 23, 3800, Victoria, Australia b SPME, Monash University, PO Box 27, 3800, Victoria, Australia. [email protected] Studies on the topology and magnetism of transition metal(II) dicyanamide complexes [1] and - their M(dca)3 anionic coordination polymers [2] have yielded a fascinating array of structures as well as interesting magnetic phenomena. II One such example is the newly synthesised compounds [Fe(H2N4L)3][M(dca)3]2Cl (M = Fe, Mn) in which we have used the bi-samidine ligand, H2N4L known to stabilize both Fe(II) and n+ Fe(III) and to undergo a spin crossover LS-HS transition in [Fe(H2N4L)3] (anion)n with a critical temperature dependent upon the anion used. H-bonding effects play a part in these monomers. 2+ We have used the complex [Fe(H2N4L)3] as a counter-cation and as templating agent for the building of a new anionic dca network. From a methanolic solution [Fe(H2N4L)3]Cl2 mixed with a methanolic solution of MCl2 and sodium dicyanamide orange/red crystals of [Fe(H2N4L)3][M(dca)3]2Cl were obtained. The determination of the X-ray structure of the complexes shows that they crystallize in a very rare Lonsdaleite network structure [3]. Magnetic studies on the complexes reveal a gradual spin-crossover transition of the Fe(III) d5 centres at around 300K. Mössbauer spectroscopy was used to characterise the oxidation state of the Fe(III) cation in both complexes . The simultaneous occurrance of spin-crossover in the cation and spin coupling in the anion was of particular Figure 1 [Fe(H2N4L)3][M(dca)3]2Cl interest from the perspective of cooperativity.
N N
NH HN
H2N4L
Anionic network structure
[1] S. R. Batten, P. Jensen, B. Moubaraki, and K. S. Murray, Chem. Commun. 2000, 2331.
[2] P. M. van der werff , S. R. Batten, P. Jensen, B. Moubaraki, K. S. Murray, Inorg. Chem., 2001, 40, 1718
[3] S. R. Batten, R. Robson, Angew. Chem. Int. Ed., 1998, 37, 1460
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Coordination Polymers and Isomerism David B. Cordes, a Paula L. Caradoc-Davies,a Lyall R. Hanton,a Kitty Leea and Mark D. Spicerb a Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand b Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow, Scotland G1 1XL [email protected] The two ligands 1,4-bis(2- pyridylmethylsulfanylmethyl)benzene (L1) and N S S N
2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L2) L1 (Figure 1) were treated with Cd(NO3)2·4H2O in 1:1 and 2:1 metal-to-ligand ratios respectively. The crystal N N S structures of the coordination polymers formed from S N N L2 these reactions, {[Cd(L1)(NO3)2]·CH2Cl2}? (1a), Figure 1. Diagram showing {[Cd(L1)(NO3)2]·4/3CH3CN}? (1b) and structure of ligands L1 and L2. {[Cd2(L2)(NO3)4]·2CH3CN}? (2), were determined.
Complexes 1a and 1b were shown to be conformational N S S N supramolecular isomers, due to L1 taking a gauche gauche conformation in 1a, and anti in 1b (Figure 2.). The S N structure of 1b displayed topological isomerism with two N S isomeric polymer chains in the same crystal forming a anti single supramolecular array. The structure of 2 showed Figure 2. Diagram showing the – two different conformations of the repeating Cd2(L2) units linked together by NO3 ligand L1. anions bridging between Cd(II) centres in a manner not previously seen in Cd(II) systems (Figure 3).
– Figure 3. Views of polymer 2: (left) One chain showing the NO3 bridging mode; (right) Close up view of the
Cd2(NO3)2 polymeric link.
IC-03 February 2-6, 2003 Melbourne 93 New Catenane Synthesis via a Schiff Base Condensation Ronald R. Fenton,a Leonard F. Lindoy,a George V. Meehan,b David F. Perkinsa and Jason R. Pricea a Centre for Heavy Metals Research, School of Chemistry, the University of Sydney, NSW 2006, Australia b School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Q 4811, Australia [email protected] Molecular modelling studies suggested that the dialdehydes 1 and 2 might be useful precursors for catenane synthesis. On binding two such molecules around a tetrahedral metal ion, such as copper(I), models indicate that each pair of aldehyde groups (belonging to a single ligand) is constrained to be orientated towards opposite sides of the metal ion. Electrospray mass spectra confirms the formation of this 2 : 1 complex. It was reasoned that if two molar equivalents of a diamine of suitable length are reacted with a bis-ligand species of this type, then the resulting tertra-imine so formed, as well as its reduced (tetra-amine) derivative, will likely be catenanes.
H N NH N N 2 4 2 N N O O t-Bu O O t-Bu n O O O NH NH 1 2 2 2 O O 5 n = 2 6 n = 3 t-Bu t-Bu t-Bu t-Bu t-Bu t-Bu O O O
O O N O HN O N O N N N NH N N N Cu R Cu R R Cu R N N N N N O N N NH O O N O HN O
O O O
t-Bu t-Bu t-Bu t-Bu t-Bu t-Bu
3 7 R = C6H12 10 R = CH2(CH2OCH2)2CH2 8 R = CH2(CH2OCH2)2CH2 11 R = CH2(CH2OCH2)3CH2 9 R = CH2(CH2OCH2)3CH2
Reaction of complex 3 with diamines 4 – 6 was monitored by ES-MS; in each experiment the reaction mixture showed major peaks at the corresponding m/z values corresponding to the Schiff base catenanes 7 – 9. In situ reduction has been confirmed to occur for the less stericaly strained species 8 and 9 which led to the expected m/z values for the amine-containing catenanes 10 and 11.
IC-03 February 2-6, 2003 Melbourne 94 The Synthesis and Study of Metal Complexes of Ligands with Tripodal Tridentate Binding Domains Christopher J. Sumby and Peter J. Steel Department of Chemistry, University of Canterbury, Christchurch, New Zealand [email protected] The programmed self-assembly of metallosupramolecular aggregates constructed from multitopic bridging ligands and transition metal centres is in a continual process of development. The armoury of the chemist has been constantly expanding with the synthesis of new multitopic bridging ligands with varied topologies. We have focussed recently on the synthesis of bridging heterocyclic ligands that posses tripodal tridentate binding domains. These ligands are constructed about isomeric diazines, to which are appended di-2-pyridylamine or di-2- pyridylmethane constructs. Two example of this class of ligand are 4,6-bis(di-2- pyridylamino)pyrimidine (1) and 3,6-bis(di-2-pyridylmethyl)pyridazine (2) (Figure 1).
H H N N N N N N N N N N N N N N
(1) (2) Figure 1. Two examples of bridging ligands with tripodal tridentate coordination. These, and related ligands, have been reacted with a range of metal salts to investigate their coordination complexes. With a range of metal precursors we have observed several common structures in the complexes of these ligands, including side-by-side [2+2] metal-ligand dimers and dinuclear helicates [1]. Comparisons between ligands bearing nitrogen and carbon linker atoms showed that the nitrogen linker is more planar thereby preventing those ligands from facially coordinating to metal atoms [2]. [1] C. J. Sumby and P. J. Steel, Inorg. Chem. Comm. 2002, in press. [2] C. J. Sumby and P. J. Steel, unpublished results, 2002.
IC-03 February 2-6, 2003 Melbourne 95 Enzyme-like Catalysis by a Doped Conducting Polymer. Proximity Effects Generated by Concentration.
Jun Chen,a Junhua Huang,b Gerhard F. Swiegers,b Chee O. Too,a Gordon G. Wallacea a Intelligent Polymer Research Centre, University of Wollongong, Wollongong, NSW 2522, Australia. b CSIRO Molecular Science, Bag 10, Clayton, VIC 3169, Australia.
[email protected] Efforts to develop biomimetic catalysts, also known as Artificial Enzymes [1], have largely focused on the synthesis of binuclear molecules in which metal-based catalytic groups are held in close and carefully selected proximities to each other [2]. This arrangement provides a catalytic pocket tailored to stabilize the transition state of bimolecular processes, as seen in many reactions involving H2, O2, and N2. However, the synthesis of such catalysts is typically non- trivial. This has severely limited their practical utility.
In this work we describe a new approach in which monomeric catalytic groups are concentrated within a porous, solid carrier such that the proximity effects necessary to afford highly efficient molecular catalysis are statistically inevitable. Coating of a platinum electrode with conducting polypyrrole doped with ferrocene sulfonate as counter-ion induces a 0.20 – 0.4 V anodic shift in the most positive potential for hydrogen gas evolution in 1 M H2SO4 and a seven-fold amplification in hydrogen production when poised for 12 h at –0.44 V (vs. Ag/AgCl). The amplification per unit electrochemical area is 3.5-fold. Similar improvements are observed over the full voltage range to –3.00 V in two-electrode water electrolysis experiments at 20 oC and 80 oC. Comparative and fundamental studies indicate that the ferrocene sulfonate dopant is transformed from a catalytically inactive species into an immensely active catalyst only because it is present in high local concentrations within the polymer. This is entirely analogous with enzymes, where collections of individually inactive functional groups become powerful catalysts purely through the influence of proximity.
These findings have significant implications, particularly for electrocatalytic devices, such as Proton Exchange Membrane fuel cells and air batteries.
[1] The term “artificial enzyme” is used as defined in: R. Breslow, Acc. Chem. Res. 1995, 28, 146. [2] J. P. Collman, P. S. Wagenknecht, J. E. Hutchison, Angew. Chem. Int. Ed. Engl. 1994, 33, 1537 and references therein.
IC-03 February 2-6, 2003 Melbourne 96 The Incorporation Of Cr3+, Fe3+, Cu2+ and Pb2+, Within Synthetic Kaolinite
Andrew R. Tong,a Brendan J. Kennedy,a and Balwant Singhb a Centre for Heavy Metal Research, School of Chemistry, The University of Sydney, Sydney NSW 2006, Australia. b School of Land, Water and Crop Sciences, The University of Sydney, Sydney NSW 2006, Australia.
Anthropogenic redistribution of metals and clays has created specific environments which enable mineral dissolution, deposition and growth to occur. The ensuing minerals would otherwise be rare in the natural world. For instance in landfill and waste depositories there exists a combination of clay and waste material not found in natural environments. The most common clay mineral within the Australian regolith is kaolinite (Al2Si2(OH)4O5) [1]. Hence, the structural transformations and chemical interaction between kaolinite and metal pollutants needs to be investigated in order to provide better management of waste materials.
Kaolinite is composed of alternating layers of tetahedra
(SiO4) and octahedra (AlO6) linked by hydrogen bonds (Figure 1). Within these layers, the octahedral layer has been shown to contain natural iron and chromium substitutions for the Al3+ cations, whilst no substitutions have been found within the tetrahedral layer. This paper investigates the influence of the heavy metals, Cr3+, Fe3+, Cu2+ and Pb2+, on the formation and structure of synthetic kaolinite. Hence, a secondary aim of this work is to develop an understanding of doping limits and synthetic procedures for synthetic kaolinites. Figure 1. Kaolinite Structure
Samples of the general type Al2-xMxSi2O4(OH)5 were prepared from aluminosilicate gels containing the appropriate amounts of the desired metal, and aged at 250 ºC and 40 bars for 10 days. Initially the samples predominately consisted of kaolinite with varying amounts of poorly crystalline boehmite. These additional mineral phases were removed by multiple extractions with hot 0.5M NaOH. The remaining materials were characterised using an array of experimental methods including infrared spectroscopy and powder X-ray diffraction. These measurements confirmed the single phase nature of the treated samples.
[1] G. Taylor and R.A. Eggleton, Regolith Geology and Geomorpholgy, 2001, Wiley and Sons.
IC-03 February 2-6, 2003 Melbourne 97 Carbon-Oxygen Bond Formation at Metal(IV) Centres: Reactivity of Palladium(II) and Platinum(II) Complexes of the “NCN-Pincer” Ligand Toward Iodomethane and Dibenzoyl Peroxide Allan J. Canty,a Melanie C. Denney,a Gerard van Koten,b Brian W. Skeltonc and Allan H. Whitec a School of Chemistry, University of Tasmania, 7001, Tasmania, Australia. b Debye Insitute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, 3584CH Utrecht, The Netherlands. c Chemistry, University of Western Australia, Crawley, 6009, WA, Australia. [email protected] The tridentate “pincer” ligand [2,6-(dimethylaminomethyl)phenyl-N,C,N]- (NCN) was used to generate stable organoplatinum(IV) complexes which model possible intermediates in metal- catalysed C-O bond forming processes (Fig. 1). Complexes of the form Pt(X)(NCN) (X =
O2CPh, 4-Tol) and Pd(O2CPh)(NCN) were reacted with dibenzoyl peroxide, (PhCO2)2, and iodomethane as oxidants. Reactions involving platinum led to the formation of stable platinum(IV) complexes, while no palladium(IV) complexes were observed.
O O O O O O N N N Pt O Pt O Pt O N N N O O CH3 O O O
I II III Figure 1. Stable platinum(IV) complexes incorporating the “NCN-pincer” ligand, characterised by X-ray
crystallography: Pt(O2CPh)3(NCN) (I), Pt(O2CPh)2Me(NCN) (II) and Pt(O2CPh)2(4-Tol)(NCN) (III).
The reaction of Pt(O2CPh)(NCN) with (PhCO2)2 formed Pt(O2CPh)3(NCN) (I) (Fig. 1), while no reaction was observed with the palladium analogue. Iodomethane reacted with complexes
M(O2CPh)(NCN) (M = Pt, Pd) to form MI(NCN) and PhCO2Me in addition to reforming
M(O2CPh)(NCN). A stable platinum(IV) intermediate, cis-Pt(O2CPh)2Me(NCN) (II) (Fig. 1), was detected and shown to undergo reductive elimination via carbon-oxygen bond formation.
The complex Pt(4-Tol)(NCN) reacted with (PhCO2)2 to form cis-Pt(O2CPh)2(4-Tol)(NCN) (III) (Fig. 1). Unlike the PtIVMe analogue, II, complex III did not undergo facile reductive elimination. The analogous palladium chemistry was not feasible due to the instability of Pd(4- Tol)(NCN).
IC-03 February 2-6, 2003 Melbourne 98 Carbon-Oxygen Bond Formation at Organopalladium Centres: The Reaction of PdMe(p-Tol)(bpy) with Dibenzoyl Peroxide Allan J. Canty,a Melanie C. Denney,a Brian W. Skeltonb and Allan H. Whiteb a School of Chemistry, University of Tasmania, 7001, Tasmania, Australia b Chemistry, University of Western Australia, Crawley, 6009, WA, Australia. [email protected]
The reaction of PdMe(p-Tol)(bpy) (bpy = 2,2’-bipyridine) with dibenzoyl peroxide, (PhCO2)2, is
a complex process and is closely related to the reaction of PdMe2(bpy) with (PhCO2)2 [1]. The initial oxidation of Pd(II) (eq. (1)) is followed by methyl group exchange between an undetected
Pd(IV) intermediate, assumed to be Pd(O2CPh)2Me(p-Tol)(bpy), and PdMe(p-Tol)(bpy) to give
Pd(O2CPh)(p-Tol)(bpy) and the detected Pd(IV) complex, Pd(O2CPh)Me2(p-Tol)(bpy) (eq. (2)). The observed Pd(IV) species decomposes by reductive elimination of ethane and p-xylene to
form Pd(O2CPh)(p-Tol)(bpy) and Pd(O2CPh)Me(bpy) (eq. (3)). The latter two complexes then
react with (PhCO2)2 forming (p-Tol)-O2CPh and Me-O2CPh respectively, and Pd(O2CPh)2(bpy) in both cases (eqs. (4) and (5)).
o II -70 C IV Pd Me(p-Tol)(bpy) + (PhCO 2)2 "Pd (O2CPh)2Me(p-Tol)(bpy)" (1) o IV -70 C IV "Pd (O2CPh)2Me(p-Tol)(bpy)" + PdMe( p-Tol)(bpy) Pd (O2CPh)Me2(p-Tol)(bpy) (2) II + Pd (O2CPh)(p-Tol)(bpy) o IV -30 C II Pd (O2CPh)Me2(p-Tol)(bpy) 0.4 Pd (O2CPh)(p-Tol)(bpy) + 0.4 Me-Me (3) II + 0.6 Pd (O2CPh)Me(bpy) + 0.6 (p-Tol)-Me o II -10 C II 0.6 Pd (O2CPh)Me(bpy) + 0.6 (PhCO2)2 0.6 Pd (O2CPh)2(bpy) + 0.6 Me-O2CPh (4) o II 20 C II 1.4 Pd (O2CPh)(p-Tol)(bpy) + 1.4 (PhCO2)2 1.4 Pd (O2CPh)2(bpy) + 1.4 (p-Tol)-O2CPh (5)
Overall: II II 2 Pd Me(p-Tol)(bpy) + 3 (PhCO2)2 2 Pd (O2CPh)2(bpy) + 0.6 Me-O2CPh +
0.4 Me-Me + 1.4 (p-Tol)-O2CPh + 0.6 (p-Tol)-Me A series of model reactions was devised to confirm the detailed reaction sequence. Combined
equations (1) and (2) were modelled by mixing a 2:1 ratio of PdMe(p-Tol)(bpy) and (PhCO2)2 at
–70 °C. To model equation (3), Pd(O2CPh)Me2(p-Tol)(bpy) was generated in situ by an alternative route and its decomposition observed. For equations (4) and (5), independently
prepared Pd(O2CPh)(p-Tol)(bpy) and Pd(O2CPh)Me(bpy) were each reacted with (PhCO2)2.
[1] A.J. Canty, M.C. Done, B.W. Skelton, and A.H. White, Inorg. Chem. Commun., 2001, 4, 678.
IC-03 February 2-6, 2003 Melbourne 99 DNA Binding Studies of the Tri-nuclear Platinum Anticancer Drug BBR3464: Pre-association with a 12-Mer DNA Duplex Joseph J. Moniodis,a Donald S. Thomas,a Susan J. Berners-Price,a Alexander Hegmansb and Nicholas Farrell a School of Biomedical and Chemical Science, University of Western Australia, 6009, WA, Australia. b Department of Chemistry, Virginia Commonwealth University, 1001 Main Street, Richmond, Virginia, 23284-2006, USA. [email protected] BBR3464 (or 1,0,1/t,t,t n=6,6) is the first genuinely "non-classical" platinum derivative to enter clinical trials and has shown responses to colon and pancreatic cancers in doses that are 10-fold less than for cisplatin. BBR3464 and related di- and tri-nuclear platinum drugs, form Pt-DNA adducts that are characterised by long-range intra- and inter-strand crosslinks, structurally distinct from those formed by cisplatin [1].
n+ H3 N Y H3 N NH 2 Pt Y NH 3 Pt H2 N NH 3 Pt H2 N NH 3 H3 N NH 2
Figure 1 – 1,0,1/t,t,t (BBR3464, Y= Cl, n=4); 0,0,0,t,t,t (Y = NH3, n=6)
Transition metal cations may "pre-associate" to DNA by electrostatic and hydrogen-bonding interactions prior to possible covalent bond formation. In the case of BBR3464 evidence for preassociation of the central linker in the minor groove has been observed in [1H,15N] NMR experiments following the formation of 1,4- and 1,6-GG interstrand crosslinks by reaction of 15N-BBR3464 with the self-complementary sequences 5'-d(ATATGTACATAT)-3' (1,4-GG) and 5'-d(TATGTATACATA)-3' (1,6-GG) [2].
To study the pre-association step in detail, we have used the non labile NH3 substituted derivative of 1,0,1/t,t,t (denoted 0,0,0/t,t,t) in reactions with the 1,4-GG sequence. We have compared 1H and two-dimensional NOESY NMR spectra at various drug:DNA ratios to characterise the binding interaction. The NMR studies have been complemented by molecular modeling studies. Semi-empirical and density functional calculations have been performed on 0,0,0/t,t,t and the results used in molecular dynamics simulations on the DNA sequence with and without the drug present. The results of these studies will be presented. [1] N. Farrell, Y. Qu. U. Bierbach, M. Valsecchi and E. Menta in Cisplatin: Chemistry and Biochemistry of a Leading Anticancer Drug, B. Lippert (Ed.) 1999, pp479-496. [2] S.J. Berners-Price, M.S. Davies, A. Hegmans, D.S. Thomas, N.Farrell. manuscript in preparation.
IC-03 February 2-6, 2003 Melbourne 100
Metal-metal bonding in cubane clusters, Cp4M4S4, M = Fe, Ru Sushilla Z. Knottenbelt and John E. McGrady University of York, Department of Chemistry, Heslington, York, YO10 5DD, U.K. [email protected] Iron-sulfur clusters are essential electron transfer agents in many biological systems. Numerous model cubane clusters, Cp4M4S4, have been synthesised with a wide range of core structures varying from perfectly tetrahedral to highly distorted. In this contribution, the nature of metal- metal bonding in the iron and ruthenium analogues, Cp4Fe4S4 and Cp?4Ru4S4, is considered. The neutral Cp4Fe4S4 and Cp?4Ru4S4 clusters have two short metal-metal distances on opposite edges of the tetrahedron (see figure 1). In the Ru species, two-electron oxidation generates a third Ru-
Ru bond, giving a C2 symmetric structure. Variable temperature NMR has shown that the Ru-Ru bonds in the cluster are fluxional, both in the reduced and oxidised forms. [1] In contrast, two- electron oxidation of the Fe species generates structures of three different symmetries, depending on counterion, a D2d, D2 and two C2 symmetric structures. [2], [3] The aim of this work is to investigate the nature of the structural flexibility within this single oxidation state using Density Functional Theory.
2+ D2d
2+
C2 - 2e-
2+
D2
2+ Figure 1: Structural flexibility of Cp4Fe4S4 .
[1] E. J. Houser, T. B. Rauchfuss, S. R.Wilson, Inorg. Chem., 1993, 32, 4069. [2] Trinh Toan, B. K. Teo, J. Ferguson, T. J. Meyer, L. F. Dahl, J. Am. Chem. Soc. 1977, 99, 408. [3] D. Bellamy, A. Christofides, N. G. Connelly, G. R. Lewis, G. A. Orpen, P. J. Thornton, J. Chem. Soc., Dalton Trans., 2000, 4038.
IC-03 February 2-6, 2003 Melbourne 101 Designing Catalysts for Green Oxidation Technologies
Terry Collins Thomas Lord Professor of Chemistry and Director of the Institute for Green Oxidation Chemistry, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213-2683
Because we do not live in a sustainable civilization, sustainability has become the most important single idea for universities for the next century. Chemists are principal custodians of the technological challenges of sustainability and inorganic chemists have especially important roles to play. As quickly as possible, we must learn how to develop the research and educational programs that will be essential for steering our communal thinking and our technology base toward sustainable directions. In chemical research, three areas stand out as being vital—the invention of more efficient technologies for converting solar to electrical or chemical energy, the replacement of polluting chemical technologies with economical non-polluting substitutes, and the development of renewable feed-stocks for the chemical industry. Concerning the second area, oxidation chemistry presents major challenges to green and inorganic chemists because its reliance upon toxic metal ions and chlorine results in substantial environmental burdens of persistent and/or bioaccumulative substances.
At the Institute for Green Oxidation Chemistry at Carnegie Mellon University, we develop green catalytic oxidation systems to contribute to moving the elemental balance of oxidation technology away from chlorine and toxic metal ions toward the natural oxidant, hydrogen – peroxide, and Nature’s most important catalytic metal H H for oxidations, iron. Hydrogen peroxide is a key reagent O in numerous enzymatic oxidations. With an annual O O production of more than 1.3 million tonnes, hydrogen N III N Fe peroxide is also an important commodity chemical for N N industrial oxidations. However, in contrast with O biochemical processes, catalysis has been largely absent O from peroxide technologies, especially larger peroxide technologies such as are found in the pulp and paper, Figure. A Prototype TAML® Activator laundering, and water treatment and decontamination areas. Over the last two decades, my group, and recently Institute, have been developing oxidatively robust tetraamido-macrocyclic ligands (TAML) via an iterative design process in which oxidation-sensitive ligand moieties are identified and replaced. We have demonstrated that subtle changes in the structure and composition of these chelating systems can greatly enhance the robustness of their complexes towards oxidative and hydrolytic degradation in the presence of peroxide leading to the development of TAML® oxidant activators. Iron-TAML® activators are proving to be as effective as peroxidase enzymes in their rates of reactivity. Their selectivity for peroxidase over catalase behavior is high. Their design is informed by mechanistic understanding of their mode of action. I will briefly sketch the design history, nature, properties, and mechanistic behavior of TAML® catalysts and the research aspects of their reduction to practice for selected technologies such as effluent treatment in the pulp and paper and textile industries, disinfection and homeland defense, the destruction of priority pollutants, and the desulfurization of gasoline and diesel.
IC-03 February 2-6, 2003 Melbourne 102 Nanoporous Molecular Framework Materials Cameron J. Kepert School of Chemistry, University of Sydney, 2006, NSW, Australia [email protected] Molecular frameworks are a new class of nanoporous material, members of which have been shown to display reversible, selective guest-exchange and to retain structural integrity during desorption/sorption. A range of materials will be presented, with discussion focusing on three specific points of interest: 1) the detailed investigation of the sorption chemistry of molecular frameworks using in-situ single crystal X-ray diffraction; 2) the incorporation of moieties of specific magnetic and electronic interest into molecular frameworks to produce materials with electronic function; and 3) the negative thermal expansion behaviour of selected frameworks.
Single crystal X-ray diffraction has been used to follow the sorption of a range of guests into the II [1] 1-D nanopores of Co (bpy)1.5(NO3)2 (bpy = 4,4?-bipyridine). Measurement of the temperature- dependent unit cell evolution, and collection of full data sets at fixed temperatures, have provided a highly detailed picture of the sorption chemistry of this material. Notably, the framework lattice displays a range of structural flexibilities in response to the up-take of guests.
The incorporation of spin crossover centres into molecular framework lattices has recently provided the first nanoporous materials to undergo electronic switching. Here we present the guest-exchange and magnetic properties of a coordination framework containing interpenetrating II rhombic grids of Fe (azpy)2(NCS)2 (azpy = 4,4?-azopyridine; see Fig. 1). The material retains monocrystallinity following guest desorption and undergoes a spin crossover transition that is sensitive to the steric and electronic influence of sorbed guest species.[2]
II Fig 1: The solvated and desolvated structures and guest-dependent spin crossover of Fe (azpy)2(NCS)2.½(guest) The investigation of the temperature-dependent unit cell parameters of molecular frameworks has unearthed negative thermal expansion (NTE; ie, contraction with heating) in a broad family of framework materials. These materials are structurally distinct from all existing NTE systems, opening a new window into this exotic phenomenon. Further, their unprecedented expansion properties and growth as single crystals points to their possible use in a range of applications.
[1] (a) E.J. Cussen, J.B. Claridge, M.J. Rosseinsky, C.J. Kepert, J. Am. Chem. Soc, 2002, 124, 9574-9581; (b) A.J. Fletcher, E.J. Cussen, T.J. Prior, M.J. Rosseinsky, C.J. Kepert, K.M. Thomas, J. Am. Chem. Soc., 2001, 123, 10001-10011.
[2] G.J. Halder, C.J. Kepert, B. Moubaraki, K.S. Murray, J.D. Cashion, Science, 2002, 298, 1762-1765.
IC-03 February 2-6, 2003 Melbourne 103 Malleability of Metal-Dicyanamide Coordination Networks
Stuart R. Batten, Jasmine Filali, Alexander R. Harris, Paul Jensen, Anna M. Kutasi, Boujemaa Moubaraki, Keith S. Murray, David J. Price and Patricia M. van der Werff School of Chemistry, Monash University 3800, Victoria, Australia [email protected]
- The long-range magnetic ordering observed in the a-M(dca)2, dca = dicyanamide, N(CN)2 coordination polymers [1] has generated great interest in the coordination networks of this ligand. As part of our interest in this area we have been using a number of different approaches to modify the topology of the M-dca networks, and trying to discern relationships between the structures and the magnetic properties [2].
One such approach has been the introduction of coligands to generate compounds of general formula M(dca)2(L)x. These coligands include terminal ligands, such as solvent molecules, and a large range of coligands capable of bridging between metal ions, including tricyanomethanide, pyrazine and derivatives, 4,4’-bipyridine, dabco, hexamethylenetetramine, 1,2-bis(4- pyridyl)ethene, nicotinic acid and (iso)nicotinamide.
We have also been able to modify M-dca networks through cation templation of anionic - 2- M(dca)3 and M(dca)4 coordination polymers. This method has proved very successful, with network topology sensitive to even subtle changes to the nature of the countercation. Generation of 1D, 2D and 3D networks has thus been possible. Cations used + + include Ph4As , Ph3RP (R = Me, Et, Pr, Ph, 2+ + Me2NPh), (chelate)3M and (Cp*)2Fe , and Figure 1. Cation templation in the structure of (MePh P)M(dca) . we have even found an instance of templation 3 3 of a neutral M-dca network by inclusion of a salt.
The results of this ongoing study have demonstrated the significant malleability of M-dca networks or network substructures. The dca ligand can display a variety of binding modes, and reactions producing polymorphs or other varieties of closely related structures are common. This contribution will present selected example of the numerous structures mentioned above to illustrate a number aspects of the fascinating structural chemistry of the dca ligand.
[1] S.R. Batten, P. Jensen, B. Moubaraki, K.S. Murray, and R. Robson, Chem. Commun., 1998, 439.
[2] S.R. Batten and K.S. Murray, Aust. J. Chem., 2001, 54, 605; Dalton Trans., in preparation; Coord. Chem. Rev., in preparation.
IC-03 February 2-6, 2003 Melbourne 104 Using Flexible Multimodal Ligands to Influence Coordination–Polymer Jarrod J. M. Amoore,a Lyall R. Hanton,a and Mark D. Spicerb a Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand b Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow, UK, G1 1XL. [email protected] The use of organic–ligand connectors and metal–ion nodes provides a powerful strategy for generating polymeric coordination networks. Thus, a wide variety of infinite assemblies can be constructed through careful ligand design and the use of metal ions, such as Ag(I) or Cu(I), which have plastic coordination spheres. Ag(I) is particularly susceptible to the influence of weaker supramolecular forces due to its accommodating coordination sphere and relatively weak Ag(I)–ligand interactions. As part of our design strategy we have prepared a new flexible multimodal ligand, bis(2– pyrazylmethyl)sulfide L, that differs from the more conventional ligand connectors in that it offers chemically distinct binding sites, both chelating and monodentate. In addition, L is flexible, unlike other recently developed rigid multimodal ligands. In contrast to these rigid multimodal ligands, it is more conformationally malleable and it is almost always able to use all of its donor atoms in coordination network formation. The ligand is able to adopt a variety of syn and anti conformations as well as different coordination modes (shown below).
Ag Ag Ag Ag Ag
N N N N N N N N
N N N N N N N N S S S S Ag Ag Ag Ag Ag Ag Ag Ag
We will present our results on the diverse coordination polymer architectures formed by L with – various Ag(I) salts. These architectures range from ladders (1), some linked by NO3 anions (2), a ribbon linked by N···H–C synthons, and a porous three-dimensional structure (3). We have found the type of architecture formed is sensitive to the ligand conformation and to the counterion.
1 2 3
IC-03 February 2-6, 2003 Melbourne 105 The Role of Hydrogen Bonding in Coordination Polymers
Brendan F. Abrahams School of Chemistry, University of Melbourne, 3010, Victoria, Australia
The synthesis and characterization of coordination polymers generated by linking metal centres with bridging ligands is an area of chemistry experiencing rapid growth. A major reason for interest in this area lies in the potential for tailoring such materials in order to impart useful physical properties.
Although there are many examples in the literature where rational design has led to the successful generation of targeted coordination polymers, we, and we suspect others in this general area, have often failed to obtain a desired structure despite the employment of seemingly sound chemical and geometric principles. In many cases weak secondary bonding interactions that may not have been anticipated, have led to unexpected results.
In our work over recent years it has become apparent that weak interactions such as hydrogen bonding can have a major influence on metal coordination geometries and the connectivity of coordination polymers. In this presentation the structural impact of hydrogen bonding involving bridging ligands in a number of new structures is examined. The potential for using such interactions to divert a reaction from its normal course in order to obtain a desired product is discussed.
IC-03 February 2-6, 2003 Melbourne 106 The Thiosulfate Gold Leaching Process: Importance of Copper Complexation and Reactivity
Leone Spiccia School of Chemistry and Centre for Green Chemistry, Monash University, 3800, Victoria, Australia, [email protected] Increasing concern about the hazards associated with the use of cyanide, highlighted by major recent accidents in Rumania and Papua New Guinea, is driving research into more benign gold leaching agents. Of the many alternatives that have been examined, leach solutions containing ammonia, thiosulfate and copper(II) have shown greatest promise.[1] In this electrocatalytic process, native gold is oxidised to gold(I) by a Cu(II) tetraammine catalyst, complexed to thiosulfate and separated from the lixiviant mixture using, for example, ion-exchange chromatography. Reaction of the Cu(I) complexes that form as part of the gold oxidation cycle with oxygen regenerates the catalyst. Ongoing studies have highlighted the need to examine the fundamental chemistry of this process. The chemistry controlling thiosulfate reactivity is attracting attention because the oxidation of thiosulfate occurs in parallel with gold leaching, dramatically increasing reagent consumption and impacting adversely on the economic viability of this leaching process.
One objective of our research is to understand the copper chemistry associated with the thiosulfate leaching process. Towards this end, we have been studying Cu(I) speciation in ammonia-thiosulfate- chloride solutions, and the reactivity of complexes present in these solutions with oxygen, in order to probe the regeneration of the Cu(II) catalyst. At the same time, we have been developing reagents, primarily Cu(II) complexes, which show improved gold leaching properties and a reduced rate of thiosulfate oxidation. These studies have led us to a general study of the mechanism of oxidation of thiosulfate by Cu(II) polyamine complexes. For 2+ example, we have found that [Cu(tren)OH2] (tren = tris(2-aminoethylamine)) reacts rapidly with thiosulfate forming [Cu(tren)S2O3] (see structure), a complex which exhibits an intense absorption in the UV region. The complex is unstable and, in the 2+ presence of excess [Cu(tren)OH2] , slowly decomposes (see change in spectrum) forming a Cu(I) complex and tetrathionate. Our recent advances in these areas will be described.
[1] M. G Aylmore and D. M. Muir, Miner Eng., 2001, 14, 135; E. Molleman and D. Dreisinger, Hydrometallurgy, 2002, 66,1.
IC-03 February 2-6, 2003 Melbourne 107 Extractants to Improve Materials Balances in Metal Recovery Peter A. Tasker, David K. Henderson, Stuart G. Galbraith, Hamish Miller, Andrew Parkin, Paul G. Plieger, Kate J. Smith and Lee C. West School of Chemistry, University of Edinburgh, Edinburgh, EH9 3JJ, U.K. [email protected] The hydrometallurgical recovery of copper based on solvent extraction now accounts [1] for more than 25% of world production. The commercial success is based on the excellent materials balance obtained when processing oxidic ores, using “pH-swing” extractants of the phenolic oxime type [2] in conjunction with a conventional electro- winning from sulfate solution. Commercial “pH-swing” extractants do not give good materials balances [3] when the leaching step does not consume acid equivalent to the metal transferred to the aqueous phase, as is the case in many new oxidative leaching processes to treat sulfidic ores. To solve this problem we have considered a different mechanism, replacing an ion exchange process with one transporting metal salts across the circuit. The prototype reagents are based on ditopic ligands with well separated compartments that bind metal cation and its attendant anion. Proof-of-concept in transporting metal sulfates has used “salen- type” ligands. Stripping the metal sulfate and recycling the extractant can be accomplished [3] by exploiting a key novel design feature of the extractants - the metal sulfate is bound in a zwitterionic form of the ligand where transfer of the phenolic protons to the pendant amines generates the charged compartments that accommodate the metal cation and sulfate dianion.
[1] G.A. Kordosky, Proceeding of International Solvent Extraction Conference, Cape Town, S.A., March 2002, p. 853
[2] J. Szymanowski, “Hydroxyoximes and Copper Hydrometallurgy”, CRC press, 1993.
[3] D.M. Gunn et al., Proceeding of International Solvent Extraction Conference, Cape Town, S.A., March 2002, p. 280, S.G. Galbraith, P.G. Plieger and P.A. Tasker, Chem. Commun., 2002, 2662, and refs therein.
IC-03 February 2-6, 2003 Melbourne 108 Metal Recovery using Supramolecular Materials Based on Conducting Polymers J. Michael Davey, Jie Ding, Violeta Misoska, William E. Price, Stephen F. Ralph, David A. Reece, George Tsekouras and Gordon G. Wallace Intelligent Polymer Research Institute, University of Wollongong, NSW, 2522, Australia [email protected] Advanced materials based on conducting polymers hold great promise for applications including metal ion separation and recovery as a result of their unique blend of properties. Conducting polymers combine the strength of conventional polymers with the conductivity of metals, and may be processed into a variety of forms. This paper will discuss different approaches to metal ion recovery using membranes, colloids and composite materials composed of conducting polymers. Figure 1 illustrates how conducting polymer membranes can function as electrochemically controlled, semi-permeable barriers towards metal ions. By doping conducting polymers with calixarenes and other chelating agents we have been able in some instances to dramatically increase the flux and selectivity of metal ion transport across such membranes. Figure 2 illustrates the extraordinary ability of conducting polymer composite materials to selectively recover gold. Recent results show that these materials can also recover platinum and silver from solution.
6 100 5 80 4 Conc 3 60 (ppm) A B C 2 40 1
Percentge Recovery 20 0 0 100 200 300 400 0 Au Fe Time (minutes) 30 min 1200 min Iron Gold
Figure 1. Transport of gold and iron across a PBT/S- Figure 2. Selective recovery of gold PHE membrane from a solution containing Au3+ and from a solution containing 1 ppm Fe3+. Regions A and C: No electrochemical stimulus; Au3+, 1000 ppm Fe3+ and 0.1 M HCl Region B: Electrochemical stimulus applied. by PPy/pTS/RVC.
IC-03 February 2-6, 2003 Melbourne 109 Polymers by Clean Technologies
Bradley M. Berven, Lindsay T. Byrne, George A. Koutsantonis, Brian W. Skelton, and Allan H. White Chemistry, School of Biomedical and Chemical Sciences, University of Western Australia, 6009, Perth, Western Australia. [email protected]
Plastics have revolutionised society from the first Bakelite® to bullet-proof Kevlar®. It would be near-impossible to imagine a world without synthetic polymers. However, the expensive drying procedures and huge volumes of toxic organic waste regularly incorporated with obtaining the commercial polymer in a dry useable form have encouraged the industry to invent new cleaner methods for plastic production. One alternative is the use of supercritical fluids (SCFs) as benign reaction solvents. In particular supercritical carbon dioxide (scCO2) has received recent attention as an environmentally sound alternative for many processes[1-4].
This research focuses on the synthesis of polyketone (PK), a new versatile plastic with high chemical and temperature resistance and biodegradability, using a Pd, Pt or Ni based catalyst in supercritical carbon dioxide (scCO2). Commercially PK is produced by the copolymerisation of carbon monoxide (CO) and ethylene using a palladium-phosphine catalyst in methanol or dichloromethane, a process which uses huge volumes of environmentally harmful organic solvents. The advantage of using scCO2 as the reaction medium is that the polymerisation vessel can simply be depressurized, the gaseous CO2 is recycled and the PK is left dry and ready to use.
The active PK catalyst needs to be soluble in scCO2, and it is well known that the presence of long perfluoroalkyl chains is known to promote scCO2 solubility[5-7]. Promising results have shown that new Pd, Pt and Ni complexes containing a novel bis(phosphine) ligand, (p-F13C6- C6H4)2P(CH2)3P(C6H4-p-C6F13)2, or dfppp (Figure 1), will catalyse the copolymerisation of CO and ethylene in scCO2 to give PK. Dfppp contains 4 long perfluoroalkyl chains or 'fluoro- ponytails' and complexes of the type [(dfppp)PdCl2] have shown excellent scCO2 solubility.
Rf Rf PP Rf = C6F 13 Rf Rf
Figure 1. The novel fluoro-ponytailed bis(phosphine) dfppp
[1] J.L. Kendall, D.A. Canelas, J.L. Young, and J.M. DeSimone, Chem. Rev., 1999, 99, 543. [2] A.I. Cooper, J. Mater. Chem., 2000, 10, 207. [3] S.L. Wells, and J.M. DeSimone, Angew. Chem. Int. Ed., 2001, 40, 518. [4] A.I. Cooper, Adv. Mater., 2001, 13, 1111. [5] S. Kainz, W. Leitner, and A. Pfaltz, J. Am. Chem. Soc. 1999, 121, 6421. [6] D. Koch, and W. Leitner, J. Am. Chem. Soc. 1998, 120, 13398. [7] S. Kainz, D. Koch, W. Baumann, and W. Leitner, Angew. Chem. Int. Ed. Engl. 1997, 36, 1628.
IC-03 February 2-6, 2003 Melbourne 110 New Bridging Heterocyclic Ligands for Use in Metallosupramolecular Chemistry Peter J. Steel Department of Chemistry, University of Canterbury, Christchurch, New Zealand. [email protected] We have long been engaged in the synthesis of new N-heterocyclic compounds for use as chelating and/or bridging ligands in coordination and organometallic chemistry. This talk will focus on recent results involving the self-assembly of coordination polymers with novel structural features.
For example, some chiral and directional 1-D coordination polymers derived from camphor- based ligands, such as (1), will be described.
Other 1-, 2- and 3-D structures obtained from conformationally flexible ligands, such as (2), (3) and (4), will be described. Such ligands provide access to new metallosupramolecular species with interesting topologies. Examples will include molecular ladders, lattices, helicates and tubes.
N N N N N N N N N N N N
N N N (1) N (2) N (3)
N N O O
N O O N
O O N N
(4)
IC-03 February 2-6, 2003 Melbourne 111 Building Network Structures with Molecular Hosts Ruksanna Ahmad,a Michaele J. Hardie,a Colin L. Rastonb a Department of Chemistry, University of Leeds, Leeds, LS2 9JT, UK. b Department of Chemistry, University of Western Australia, Crawley,WA 6009, Australia. [email protected]
The creation of infinite network structures using host molecules can involve incorporating known host molecules into hydrogen bonded network structures or coordination polymers, or using host-guest interactions to build up the infinite structural motif. This may have several interesting consequences, including altering the host-guest characteristics of the host molecule without the need for extensive covalent synthesis, and creating crystalline materials that show multiple inclusion behaviour such as lattice inclusion and site specific host-guest interactions.
We are interested in the rigid bowl-shaped molecule cyclotriveratrylene (CTV). CTV is a molecular host with particular affinity for large guest species such as fullerenes and carboranes. Its abilities as a host molecule, combined with a 3-fold arrangement of dimethoxy moieties that can be utilised as hydrogen bond acceptors or as a chelating ligand, allow the formation of crystalline assemblies of considerable comp lexity. For example the complex
[Sr(H2O)8][(CH3CN)Ç(CTV)]4(H2O)4[Co(C2B9H11)2]2 features a 3D hydrogen bonded network, 2+ formed between CTV, H2O and [Sr(H2O)6] , as well as complexation of guest CH3CN in the molecular cavity of the CTV.[1] The topology of this network is a hitherto unknown 12,3 connected net, Figure 1. Other 2+ metals form isostructural complexes.[2] The complex
[Na(CTV)(H2O)(CB11H6Cl6)](CF3CH2OH) shows a chiral coordinate chain with the - + [CB11H6Cl6] anion coordinating to the Na and contained as an intracavity guest (Figure 2). The synthesis and x-ray crystal structures of these and related systems will be presented.
Figure 1. Schematic of the 3,12-conencted network of Figure 2. Chiral coordinate chain of [Sr(H2O)8][(CH3CN)(CTV)]4(H2O)4[Co(C2B9H11)2]2 [Na(CTV)(H2O)(CB11H6Cl6)](CF3CH2OH) [1] M. J. Hardie, C. L. Raston, A. Salinas, Chem. Commun. 2001, 1850.
[2] R. Ahmad, M. J. Hardie, CrystEngComm 2002, 4, 227.
IC-03 February 2-6, 2003 Melbourne 112
"The Design, Synthesis and Structure of Porphyrin Hosts for Supramolecular Fullerene Binding."
Peter D.W. Boyd,a Steven M. F. Kennedy,a Ali Hosseinia , Dayong Sunb, Fook Thamb and Christopher A. Reedb a Department of Chemistry, The University of Auckland, Auckland, New Zealand b Department of Chemistry, University of California Riverside, Riverside, California, USA. [email protected]
The attractive interaction between the curved pi surface of a fullerene and the planar pi surface of a porphyrin or metalloporphyrin has been recognised in a large number of x-ray crystal structures of naturally assembling cocrystallates of fullerenes C60 and C70 with tethered and untethered porphyrins and metalloporphyrins. [1,2] In all structures there are close intermolecular contacts (ca. 280pm) between the inner 16-atom porphyrin core and fullerene carbon atoms(short in comparison to contacts in structures such as graphite (335pm), porphyrin- porphyrin (>320pm), to the separations of C60 from arene rings (300-350pm) and ball to ball separations (>320pm)). In this paper we report new results from our synthetic and structural studies of porphyrin hosts designed to bind fullerene guests using this supramolecular interaction. We shall present the structural and binding properties of a range of acyclic bis-porphyrin hosts, linked by metal coordination or covalent attachment and examples of assemblies of 1 and 2 dimensional tetra pyridyl-porphyrin coordination polymers with C60 and C70. [3,4]
[1] T. Drovetskaya, P.D.W. Boyd and C.A. Reed, J. Org. Chem., 1997, 62, 3642-3649. [2] M.M. Olmstead, D.A. Costa, K. Maitra, B.C. Noll, S.L. Phillips, P.M. Van Calcar and A.L. Balch. , J. Amer. Chem. Soc.,1999, 121, 7090; P.D.W. Boyd, M. Hodgson, L. Chaker, C.E.F. Rickard, A. Oliver , P.J. Brothers, R. Bolskar and C.A. Reed, J. Amer. Chem. Soc.,1999, 121, 10487. [3] D. Sun, F. S. Tham, C. A. Reed, L. Chaker and P. D. W. Boyd, J. Amer. Chem. Soc., 2002, 124, 6604. [4] D. Sun, F. S. Tham, C. A. Reed, P. D. W. Boyd, Proc. Nat. Acad. Science, 2002, 99, 5088.
IC-03 February 2-6, 2003 Melbourne 113
Modeling the Corrosion Inhibition Film Provided by Ce(salicylate)3.H2O on Mild Steel
C. M. Forsyth,a K. Wilson,b T. Behrsing,a K. Konstas,a G. B. Deacon,a M. Forsythb and N. Brack c a School of Chemistry, b School of Physics and Materials Engineering, Centre for Green Chemistry, Monash University, Vic., 3800, Australia and c Latrobe University, Bundoora, 3083, Vic. [email protected]
Ce(salicylate)3.H2O is an excellent corrosion inhibitor for steel, yet the mechanism of inhibition us unknown. Surface characterisation techniques such as scanning electron microscopy (SEM), ATR FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS) together with the synthesis and X–ray structural structural characteristion of novel bimetallic Ce and Fe complexes containing the salicylate ligand, mimic the protective deposits and allows postulation of the
chemical nature of the formed barrier layers in Ce(salicylate)3.H2O treated samples.
- Figure 1. The common 2-D structural motif ({Fe(sal)2bipy} ) observed in several novel bimetallic Ce3+/Fe3+/salicylate crystallisation products, obtained using the neutral chelating donor bipy (2,2’-bipyridyl).
IC-03 February 2-6, 2003 Melbourne 114 Solving the Great Nitrate Riddle Michael R. Grace School of Chemistry & CRC for Freshwater Ecology, Monash University, Clayton, 3800, Victoria, Australia [email protected] The presentation will examine the origins, biogeochemical cycling and fate of nitrate in Melbourne's waterways and will review our current state of knowledge. The research is driven by the imperative to decrease the nitrate load entering Port Phillip Bay so that the Bay does not turn into a long-term, algal-dominated “Green Swamp” (a dire but realistic forecast from the CSIRO study of the ecological health of the Bay in mid 1990's [1]). The prediction is that the whole character of the Bay will change dramatically from a benthic algae, fringing macrophyte system to a phytoplankton-dominated system if the nitrogen loads entering the bay increase by as little as 2-3 times current levels. This presentation will discuss possible reasons for why nitrate concentrations are so high in Melbourne’s waterways, even in the relatively pristine, forested streams in Melbourne's east, the biogeochemical pathways for nitrate conversion to N2 and how this transformation can be optimized.
[1] G. Harris, G. Batley, D. Fox, D. Hall, P. Jernakoff, R. Molloy, A. Murray, B. Newell, J. Parslow, G. Skyring and S. Walker (1996), Port Phillip Bay Environmental Study Final Report, CSIRO, Canberra, Australia.
IC-03 February 2-6, 2003 Melbourne 115 Environmental and Occupational Exposure to Chromium(VI): Characterisation of Novel Chromium(V)–Bioligand Complexes Rachel Codd,a Aviva Levina,a Swetlana Geza and Peter A. Laya a Centre for Heavy Metals Research, School of Chemistry, University of Sydney, NSW 2006, Australia [email protected] Since Cr(VI) compounds are documented human carcinogens, the wide use of these compounds in industry presents a serious occupational health risk. Through inhalation and dermal contact with Cr(VI) compounds, workers in Cr(VI)-dependent industries may suffer from perforation of the nasal septum, dermal irritation and cancer of the respiratory tract. More recent attention has been directed toward the impact that Cr(VI) contamination in the environment may have upon local populations. In the absence of reducing agents, Cr(VI) does not affect the integrity of DNA, which is in contrast to select Cr(V) species which are able to cleave DNA and are genotoxic. Therefore, Cr(V) species are strongly implicated as playing a critical role in the Cr(VI)-induced carcinogenic cascade [1]. Given the potential serious health issues posed by the presence of Cr(VI) in the work place and the environment, it is important that the chemistry of Cr(V) is considered in the context of ligand systems that exist in both these settings.
Electron paramagnetic resonance (EPR) spectroscopy has been used to characterise complexes formed between Cr(V) (d1) and ligands, such as OH OH sialic acid (I) and derivatives, that model the HO OH NH O sialoglycoprotein-rich environment of the HO O O HO human respiratory tract. A series of stable I
OH 3- Cr(V)–sialic acid complexes (e.g. II) are formed O NHAc - H O with coordination modes that are able to be O H O O OH Cr H OH distinguished using EPR spectral simulation HO H O O H OH H O- techniques [2]; these results have led to an II AcHN O important modification to the ‘uptake-reduction’ HO - model of Cr(VI)-induced carcinogenicity [3]. In O O O addition, we will present our results that show Cr N N O O that hydroxamic acids, which are potential metal III chelates produced by bacteria, form stable complexes with Cr(V) (III), which has Figure 1. Structure of sialic acid (I) and oxoCr(V)–sialic acid (II) and oxoCr(V)–hydroxamic acid (III) important implications with respect to Cr(VI) complexes. contamination in the environment [4].
[1] R. Codd, C.T. Dillon, A. Levina, and P.A. Lay, Coord. Chem. Rev., 2001, 216-217, 533.
[2] R. Codd, and P.A. Lay, J. Am. Chem. Soc., 2001, 123, 11799.
[3] P.H. Connett, and K.E. Wetterhahn, Struct. Bond. (Berlin), 1983, 54, 93.
[4] S. Gez, R. Luxenhofer, A. Levina, R. Codd, and P.A. Lay, Manuscript in preparation.
IC-03 February 2-6, 2003 Melbourne 116 Copper homeostasis: A Structural Genomics Approach Lucia Banci CERM and Department of Chemistry, University of Florence, Sesto Fiorentino, Italy [email protected] Copper homeostasis in living organisms, and metal homeostasis in general, is the result of a very complex ensemble and interaction of a number of cellular processes. Several aspects need to be tightly controlled. First, the concentration of free copper ions should be negligible, as the copper ions are highly toxic due to their redox properties, e.g. by catalysing the formation of radicals which can damage the cell and therefore in the cell they are sequestered from solution, being bound to proteins. On the other hand, newly produced copper-binding proteins need to uptake copper ions to achieve their active form. As the free copper concentration in the cell is very low, a system permitting rapid and efficient metal transfer, and preventing non specific reactions involving copper must be available. Thus, the second function of some of the proteins involved in copper homeostasis is that of “chaperoning” the copper ion to copper-dependent proteins through very selective protein-protein interactions. The unravelling of this delicate interplay has started only recently, taking great advantage of the increasing availability of genome sequences. Genome sequencing is providing a wealth of data, and most notably the primary sequences of all the proteins produced by a given organism. However, the understanding of their functional role is still at the beginning. Three-dimensional structural information can be exploited to unravel at atomic level the mechanisms by which a protein carries out its function, and can often be very useful to predict at least gross functional features even in the absence of biochemical data. Extensive genome browsing for proteins potentially involved in the mechanisms of copper uptake and release, transport and resistance (in some pathogens) has been performed and several proteins have been located, which have been grouped on the basis of their sequence identity. An exhaustive structural characterization on some proteins of each group has been performed which provided fundamental information on their properties. An overview of the understanding of molecular function and cellular processes as obtained from these studies will be also discussed.
IC-03 February 2-6, 2003 Melbourne 117 Studies of Group1 Metallated ß-Dinitrogen Ligands and Their Synthetic Utility Toward Homo- and Heteroleptic Complexes of the Lanthanoids.
Marcus L. Cole and Peter C. Junk*
School of Chemistry, Monash University, Victoria 3800, Australia. [email protected] Organometallic complexes of the lanthanoid elements have attracted great interest due to their potential application in hydrogenation, polymerisation, hydroboration and oligomerisation catalytic processes. More recently bulky organoamido- and alkoxo-lanthanoid complexes have been studied for their uses in similar roles. These compounds are considered alternatives to the ubiquitous cyclopentadienyl (= Cp-) lanthanoid complexes and have scope for considerable chemistry using Cp- compounds as comparisons. Studies of the Group 1 metallation of bulky di(aryl)formamidines and N-silylated picolines within our laboratory have provided several sodium and potassium species suitable for the metathetical preparation of low coordination number (ca. ? 6) lanthanoid species [1]. This communication presents the synthesis and structural characterisation of the first 2-(trimethylsilyl)amido-6-methylpyridine and di(aryl)formamidinate complexes of the lanthanoids (eg. 1 and 2) as well as conversion of stable lanthanoid +2 (Sm and Yb) complexes to +3 species via a putative radical pathway. The novel coordination modes of several Group 1 precursor materials will also be discussed [2].
(1) (2)
[1] Jens Baldamus, Marcus L. Cole, Ulrike Helmstedt, Eva-Marie Hey-Hawkins, Cameron Jones, Peter C. Junk, Franziska Lange and Neil A. Smithies, J. Organomet. Chem., 2002, in press. [2] Marcus L. Cole and Peter C. Junk, J. Chem. Soc., Dalton Trans., 2002, manuscript submitted.
IC-03 February 2-6, 2003 Melbourne 118
Glutathionylcobalamin: A biologically important vitamin B12 derivative? Andrew G. Cregan, Ling Xia and Nicola E. Brasch Research School of Chemistry, Australian National University, ACT, 0200, Australia [email protected]
Vitamin B12 derivatives are known to be cofactors in approximately 15 enzyme reactions. Two of these reactions, involving methionine synthase and methylmalonyl-CoA mutase, occur in humans and utilise the vitamin B12 derivatives methylcobalamin (MeCbl) and 5’-deoxyadenosylcobalamin (AdoCbl), respectively. In the former reaction, MeCbl is an intermediate in the methylation of homocysteine (Hcy) by methyl-tetrahydrofolate and this reaction has received much attention in the medical literature in recent years. It has been shown that patients with high levels of Hcy have a greatly increased risk of suffering a stroke or a heart attack,[1] and there is increasing evidence that high levels of Hcy are prevalent in sufferers of Alzheimer’s disease and other neurological disorders.[2] The other vitamin B12 derivative which occurs in significant amounts in biological + systems is aquacobalamin (H2OCbl ). COOH H O N Jacobsen et al recently suggested that glutathionyl- H2N N COOH O H cobalamin (GluSCbl, Fig. 1) is a biologically S H2NOC CONH2 important vitamin B12 derivative, after isolating it from CH3 H2NOC CH a variety of mammalian cell types.[3] The high (up to 3 H3C CONH 10 mM) intracellular concentrations of glutathione N N 2 H3C could rapidly convert HOCbl+ to GluSCbl. The Co+ 2 H N N thermodynamics and kinetics of the formation of CH3 + CH3 H C GluSCbl from H2OCbl and glutathione have been H2NOC 3 CH3 investigated in detail for the first time. GluSCbl was CONH2 HN O found to form rapidly, and a mechanism has been N CH3 H3C H proposed for this reaction. The formation constant for HO N CH3 GluSCbl is several orders of magnitude larger than O O P O O – previously believed, and as such glutathione is the only O OH ligand known to approach the remarkable binding Figure 1. The structure of glutathionyl- cobalamin (GluSCbl). + affinity of cyanide to H2OCbl .
[1] (a) G. J. Hankey, J. W. Eikelboom, CNS Drugs, 2001, 15, 437. (b) E. P. Quinlivan, J. McPartlin, H. McNulty, M. Ward, J. J. Strain, D. G. Weir, J. M. Scott, Lancet, 2002, 359, 227. [2] (a) A. McCaddon, G. Davies, P. Hudson, S. Tandy, H. Cattell, Int. J. Ger. Psych., 1998, 12, 235. (b) S. M. Baig, G. A. Qureshi, M. Minami, Biog. Amines, 1998, 14, 1.
[3] E. Pezacka, R. Green, D. W. Jacobsen, Biochem. Biophys. Res. Commun., 1990, 169, 443.
IC-03 February 2-6, 2003 Melbourne 119 Characterization of Unstable Transition Metal Complexes Using NMR Spectroscopy Tamim Darwish, Graham E. Ball School of Chemical Sciences, University of New South Wales, 2052, NSW, Australia. [email protected] This study aims to generate and characterize short-lived transition metal complexes, in particular those of tungsten, using NMR spectroscopy. Our efforts to observe unstable metal complexes of weakly coordinated ligands, such as alkanes, dihydrogen and chloroalkanes, will be discussed. These intermediate species are photolytically generated in situ inside the NMR magnet at low temperatures down to 123 K. The same setup has previously been used by our group to study the
CpRe(CO)2(cyclopentane) complex [1].
Ultraviolet irradiation of W(CO)5(L) or W(CO)4(L)(L') (where L is a photolabile amine ligand and L' is a spin-half phosphine ligand) in alkane solution at low temperature will photoeject the amine ligand producing a 16 electron solvated intermediate where a solvent molecule occupies the vacant coordination site. Our work to date suggests that precursor tungsten carbonyl complexes incorporating a tertiary amine ligand give the highest solubility in alkanes at low temperatures.
Computational studies have predicated that the dihydrogen complex W(CO)5(H2) is more stable than the dihydride form W(CO)5H2 by 14 Kcal/mol [2]. However, a previous study has shown that the dihydride is the final product at low temperature photolysis [3]. In this study we have used our NMR photolysis setup and introduced H2 gas (or HD gas for coupling information) to probe for possible dihydrogen intermediates.
[1] S. Geftakis, G.E. Ball, J. Am. Chem. Soc., 1998, 120, 9953-9954.
[2] J. Tomas, A. Lledos, Y. Jean, Organometallics, 1998, 17, 4932-4939.
[3] D.M. Heinekey, J.K. Steven, M. Schultz, J. Am. Chem. Soc., 2001, 123, 12728-12729.
IC-03 February 2-6, 2003 Melbourne 120 Insights into the Anti-Inflammatory Mechanisms of Copper and Zinc Indomethacin: Why are they Less Ulcerogenic than the Parent Drug? Carolyn T. Dillon,a,b Trevor W. Hambley,b Brendan J. Kennedy,b Peter A. Lay,b Qingdi Zhou,b Neal M. Davies,c J. Ray Biffin,d and Hubert L. Regtop.d a Australian Key Centre for Microscopy and Microanalysis, Electron Microscope Unit, University of Sydney, NSW, 2006, Australia. b Centre for Heavy Metals Research, School of Chemistry, University of Sydney, NSW, 2006, Australia. c Faculty of Pharmacy, University of Sydney, NSW, 2006, Australia d Biochemical Veterinary Research, Pty Ltd, Braemar, NSW, 2575, Australia. [email protected] Gastrointestinal (GI) toxicity is one of the major problems associated with anti-inflammatory drugs [1]. One of the main methods devised for combating this problem is the use of selective COX-2 inhibitors which, theoretically, target the enzyme associated with the inflammation cascade. At the same time the COX-1 enzyme, necessary for maintaining normal physiological function by its control of the renal parenchyma, gastric mucosa, platelets, and most other mammalian tissues, is spared. Recently, the promise of this class of drugs has been dampened, however, by findings that they exacerbate pre-existing ulcers and also cause renal damage, elevated blood pressure and platelet aggregation. In this work, the complexation of the powerful anti-inflammatory drug (IndoH) by metal ions, as a means of reducing GI toxicity, has been studied [1].
The in vitro superoxide dismutase (SOD) activity, in vivo anti-inflammatory activity and gastrointestinal ulcerogenic properties of IndoH, [Cu2(Indo)4(DMF)2] and [Zn2(Indo)4(DMA)2] are presented. All three compounds exhibited anti-inflammatory activity in male Sprague- Dawley rats, yet the severity of the gastro-intestinal toxicity, as determined by macroscopic ulcerations and the concentration of caecal haemoglobin, varied for the compounds.
[Cu2(Indo)4(DMF)2] exhibited the most promising results of the Indo-complexes assayed, in that it exhibited SOD activity and the lowest gastrointestinal damage whilst also exhibiting anti- inflammatory activity that was comparable to that for IndoH. Most importantly, it was evident from low-temperature EPR analyses that the formulation used for [Cu2(Indo)4(DMF)2] administration was crucial to the integrity of the complex [2]. This is discussed with reference to the GI toxicity of the drug and the wider implications of its efficacy.
[1] J.E. Weder, C.T. Dillon, T.W. Hambley, B.J. Kennedy, P.A. Lay, J.R. Biffin, H.L. Regtop, N.M. Davies, Coord. Chem. Rev., 2002, 232, 95-126. [2] C.T. Dillon, T.W. Hambley, B.J. Kennedy, P.A. Lay, Q. Zhou, N.M. Davies, J.R. Biffin, and H.L. Regtop, Chem. Res. Toxicol. 2002, in press.
IC-03 February 2-6, 2003 Melbourne 121 Let There Be Light – Photoinduced Schiff Base Condensation Reactions Glen B. Deacon,a Penny R. Drago,a Trevor W. Hambley,b Joanne Ireland,a and Dayna N. Masona a School of Chemistry, Monash University, Clayton, Victoria 3800, Australia b Centre for Heavy Metals Research, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia [email protected] This poster examines photoactivated Schiff base condensation reactions. Reaction of a platinum
organoamide, [Pt{((p-YC6F4)NCH2)2}(py)2] (Y = H, F, Br or I), with acetone and ethane-1,2-
diamine (en) in the presence of light yields [Pt{((p-YC6F4)NCH2)2}{((CH3)2C=NCH2)2}] (Y = H, F, Br or I) (see Eq 1).
Y Y F F F F
F F F F N N hn N N Pt + en Pt N N acetone N N F F F F F F F F Y Y = H, F, Br, or I Y Eq 1. As outlined in Scheme 1, the reaction may proceed via coordination of acetone (a) or ethane-1,2- diamine (b), or by the formation of the ligand prior to coordination to the metal (c). The possible mechanisms have been investigated synthetically and spectroscopically, and the findings are summarised here.
en a) hn LPtpy2 + (CH3)2C=O LPt((CH3)2C=O)2 LPtSB + H2O
hn (CH3)2C=O b) LPtpy2 + en LPten LPtSB + H2O
c) LPtpy2 ,hn en + (CH3)2C=O SB LPtSB + 2py L = ((p-YC F )NCH ) , SB = ((CH ) C=NCH ) 6 4 2 2 3 2 2 2 Scheme 1.
Additionally, variation of the diamine or the ketone resulted in some interesting new platinum(II) Schiff base complexes, and the syntheses and characterisation (including crystallographic determination) of a number of these compounds are presented.
IC-03 February 2-6, 2003 Melbourne 122 The Oxidation of Novel Organoplatinum(II) Anti-Cancer Complexes Penny R. Drago,a Glen B. Deacona and Trevor W. Hambleyb a School of Chemistry, Monash University, Clayton, Victoria 3800, Australia b Centre for Heavy Metals Research, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia [email protected] Recent work has shown that organoplatinum(II) complexes with polyfluorophenyl ligands exhibit cell growth inhibitory activity [1]. A new development has been the synthesis of platinum(IV) analogues with these unique groups.
The reaction of [PtR2L2] (R = polyfluorophenyl group; L2 = cis-cyclohexylamine (cha) (1) or cyclohexane-1,2-diamine (chxn) (cis- or trans(±)-) (2) and excess hydrogen peroxide in acetone yields the platinum(IV) analogues, cis,trans,cis-[PtR2(OH)2L2] (3,4). These complexes were characterised using various spectroscopic techniques.
[PtR2L2] + H2O2 (excess) cis,trans,cis-[PtR2(OH)2L2] + H2O The difficulty in oxidising the cyclohexylamine-platinum complexes in comparison with that of the cyclohexane-1,2-diamine complexes was investigated using basic electrochemistry techniques.
These platinum complexes will be tested for anti-cancer activity.
NH2 R NH2 R
Pt Pt
R R NH2 NH2
(1) (2)
NH OH R OH 2 NH2 R
Pt Pt
NH R R 2 OH NH2 OH
(3) (4)
where R = polyfluorophenyl group
[1] Carleen Cullinane, Glen B. Deacon, Penny R. Drago, Trevor W. Hambley, Keith T. Nelson, and Lorraine K. Webster, J. Inorg. Biochem., 2002, 89, 293.
IC-03 February 2-6, 2003 Melbourne 123 Synthesis and Coordination of a new scorpionate ligand – potassium tris-[{3- (4-benzonitrile)-pyrazol-1-yl} hydroborate] Martin B. Duriska,a and Stuart R. Battena* a School of Chemistry, Monash University, 3800, Victoria, Australia
[email protected] [email protected]
We are currently attempting to synthesise coordination polymers and supramolecules which will contain reactive sites after assembly. To this end we have synthesised a number of tris(pyrazolyl)borate derivatives with pyridyl and benzonitrile reactive sites on the periphery of the ligand, by adapting previously reported syntheses of analogous compounds [1].
In particular, a tris(pyrazolyl)hydroborate derivative, with the substitution of a 4-benzonitrile group on the C3 of the pyrazole ring, has been synthesised and the resulting nickel (II) complex formed. Crystal structures of the potassium salt of the ligand and the nickel (II) bis ligand complex have been determined. It has been found that the ligand can coordinate via all six donor nitrogens or only through the three pyrazole nitrogens.
Figure 1. (Left) 4-benzonitrile derivative of tris(pyrazolyl)borate. (Right) Single sheet of the potassium salt of the same ligand.
[1] A.J. Amoroso, A.M. Cargill Thompson, J.C. Jeffery, P.L. Jones, J.A. McCleverty, M.D. Ward, J. Chem. Soc., Chem. Commun., 1994, 2751.
IC-03 February 2-6, 2003 Melbourne 124 Vapour Sorption and Release from Clay Nanotubules Malcolm E. R. Green, Colin L. Weeks, Sarah J. Antill and Cameron J. Kepert School of Chemistry, University of Sydney, 2006, NSW, Australia [email protected] The stability and high level of porosity in materials such as zeolites and activated carbon has led to their use in a wide range of applications where their ability to absorb (and desorb) small molecules is important, such as catalysis and molecular separation. Another class of materials that can exhibit porosity are clays and pillared clays, in which exchangeable cations (usually Na+ and Ca2+) within the aluminosilicate layers are replaced with large polyoxocations of metals such as Al, Si, or Ti. The product formed is a zeolitic structure where hydroxyl-oxide pillars hold the clay layers apart, generating larger interlayer channels, which collapse on heating.
Halloysite is a hydrated polymorph of the clay mineral kaolinite (Al2(OH)4Si2O5). Kaolinite consists of flat alternating silicate and aluminate sheets. In halloysite these sheets are typically rolled up to form tubules, which show remarkable stability upon loss of water up to 400 oC. The length and diameter of the tubules vary, depending on the source of the halloysite; in this work we used tubes of length 30-500 nm, outer diameter ~30 nm and inner diameter ~25 nm. A sample of halloysite was treated with the cationic surfactant hexadecyltrimethylammonium (HDTMA) to modify the surface from hydrophilic to hydrophobic, and to alter the accessible lumen volume.
The sorption properties of the natural and modified halloysite samples were investigated by measuring the adsorption and desorption of water, ethanol and n-octane vapour using an Intelligent Gravimetric Analyser. Similar amounts of uptake for all three sorptives on natural halloysite were observed, while the modified halloysite exhibited significantly altered sorptive properties, with the different sorptives revealing varied effects.
IC-03 February 2-6, 2003 Melbourne 125 High Resolution EXAFS and DFT of the Molybdenum Site of Human Sulfite Oxidase. Hugh H. Harris,a Graham N. George and K. V. Rajagopalan.b a Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University. b Department of Biochemstry,Duke University Medical Centre.
[email protected] The mononuclear molybdenum enzymes catalyse a range of reactions most of which are two- electron redox processes involving the transfer of oxygen between molybdenum and substrate. Amongst these mammalian sulfite oxidase (SO) catalyses the oxidation of sulfite to sulfate, the final step in the catabolism of sulfur containing amino acids. Binding of sulfite occurs at the molybdenum site, and results in the formal reduction of Mo(VI) to Mo(IV). In the oxidised wild- type form of the enzyme molybdenum is coordinated by two oxo ligands, the ene- 0.8 Mo-OMo-S 0.7 1,2-dithiolate of one pterin and a protein O based cysteine thiolate.[1] Despite 0.6 S S Mo 0.5 several experimental (including a S O O photoreduced crystal structure [2]) and 0.4 theoretical studies, the role and 0.3 importance of the sulfur ligands beyond 0.2 intramolecular electron transfer, is still 0.1 not precisely clear. 0 1 2 3 4 5 We report new high-resolution EXAFS RD Å)+( results on human liver SO, and input Figure 1. Molybdenum K-edge fourier transform EXAFS of these into a theoretical treatment of the Human Liver Sulfite oxidase. Insert: Active site structure of the oxidised enzyme. structure of the active site in different oxidation states and the mechanism to convert between them. DFT complements the XAS data well, providing the angular geometric information that is lacking from EXAFS, and even without much consideration for the effect of the protein environment on the active site, several salient points about the roles of the ligands during the process are noted. In particular the torsion angle
Ccys–Scys–Mo–Oaxial is calculated to be much larger in the reduced form than in the oxidised form. Not only has this angle been implicated in modulating the redox potential of the Mo center [3] but based on the observed hydrogen bonding in our calculations may be important in controlling substrate binding and the egress of protons during the regeneration stage of the enzymatic cycle.
[1] George, G. N.; Garrett, R. M.; Prince, R. C.; Rajagopalan, K. V. J. Amer. Chem. Soc., 1996, 118, 8588-8592. [2] Kisker, C.; Schindelin, H.; Pacheco, A.; Wehbi, W. A.; Garrett, R. M.; Rajagopalan, K. V.; Enemark, J. H.; Rees, D. C. Cell 1997, 91, 973-983. [3] McNaughton, R. L.; Tipton, A. A.; Rubie, N. D.; Conry, R. R.; Kirk, M. L. Inorg. Chem., 2000, 39, 5697- 5706.
IC-03 February 2-6, 2003 Melbourne 126
Aqueous solution identification of molybdate-nucleotide polyanions
Lyndal M. R. HillA, Charles G. YoungA, Graham N. GeorgeB and Anne-Kathrin Duhme - KlairC
A School of Chemistry, University of Melbourne, Victoria 3010, Australia. B Stanford Synchrotron Radiation Laboratory, SLAC, P.O. Box 4349, MS 69, Stanford, CA 94309, USA. C Department of Chemistry, University of York, Heslington, York YO 10 5DD, UK. [email protected]
Polyoxomolybdates are typically formed through condensation reactions of molybdate in the presence of acid. By including phosphates in the reaction mixture, pentamolybdodiphosphate anions have been observed to form under appropriate conditions of pH and reagent stoichiometries. The ring arrangement of the molybdate units has been reported for the complex in which the nucleotide 5’-AMP is the phosphate donor (Figure 1 below).[1]
Figure 1. Structure of the polyanion in Na2[Mo5O15(HAMP)2].6H2O
The aqueous solution identification of the pentamolybdodiphosphates formed through reaction of molybdate and the nucleotides 5’-AMP, 3’-AMP and 5’-GMP has been achieved using 1H and 31P NMR. The solid and solution state Mo K-edge XANES and EXAFS indicate retention of the cyclic structure for the Mo/5’-AMP system upon dissolution.[2]
[1] M. Inoue, T. Yamase, Bull. Chem. Soc. Jpn., 1996, 69,2863-2868. [2] L.M.R. Hill, G.N. George, A.-K. Duhme-Klair, C.G. Young, J. Inorg. Biochem., 2002, 88, 274-283.
IC-03 February 2-6, 2003 Melbourne 127 Structural Correlation with Chemical Bonding and the Properties of Transition Metal Complexes .Rosalie K. Hocking and Trevor W. Hambley Centre for Heavy Metals Research School of Chemistry, University of Sydney, 2006, NSW, Australia [email protected]
Traditionally, studies that experimentally examine electronic structure and bonding focus on spectroscopic techniques such as IR, NQR, XAS and NMR spectroscopy. Crystallography has advantages over spectroscopy in that the assignment of a bond-length between two atoms is unambiguous; but the resolution of individual crystal structures is too low to allow for trends in bonding to be extracted. Analysis of large databases can reveal trends not visible from individual observations and to date over 100,000 crystal structures containing transition metals have been reported to the Cambridge Structural Database.[1]
In this work we have utilised this large database of crystal structures to develop new experimental measures of chemical bonding. The success of these new techniques has been diverse, ranging from measuring metal-ligand covalency (Figure 1) and the spatial aspects of s- and p-bonding to understanding mechanistic effects by quantifying the ground-state contribution to ligand exchange. To our knowledge the structural measures of chemical bonding derived in this way have not been observed using any other experimental technique.
1.281.24 % Covalent M 1.308 Pt(IV) carboxylic acid (H) 50 1.298 Pt(II) sq pl. 1.331.30 Ni(II) sq pl. Bond-Order 1.288 Cr(III) Mn(III) 40 - Co(III) Fe(III) Carboxylate Bond 1.381.35 1.278 Cu(II) 4c. Fe(II) ls 30
Bond-Length (Å) Cu(II) 5c. Zn(II) 4c. Ni(II) Gd(III) 9c. 1.41 20 1.268 Cu(II) short 1.43 (…M) Mn(II) hs A 1.258 Zn(II) 5c. 10 Co(II) Fe(II) hs Cu(II) long 1.48 ionic limit Zn(II) 1.48 C-O 0 1.248 1.85 1.95 2.05 2.15 2.25 2.35 Metal-Carboxylate Bond-Length (Å)
Figure 1. A Structural Measure of Metal-Ligand Covalency. The bond length of the bound arm carboxylate group vs. metal-O bond-length (Å), for mono-dentate bound carboxylate groups of transition metals and gadolinium. The data represented in this figure is derived from 6,054 separate observations of carboxylate-metal bonds. Complexes are six-coordinate unless otherwise stated, abbreviations: hs high spin, ls low spin and sq pl. square planar.
[1] F. H. Allen and W. D. S. Motherwell, Acta Crystallogr, 2002, B58, 407-422.
IC-03 February 2-6, 2003 Melbourne 128 Synthesis of Titanium Complexes of Diaminobutanediols for Use as 45Ti Radiopharmaceuticals Cindy L.S. Kam, Trevor D. Bailey and Robyn L. Crumbie School of Science, Food and Horticulture, University of Western Sydney, Locked Bag 1797 Penrith South DC 1797 NSW Australia [email protected] The use of titanium–45 as an isotope in Positron Emission Tomography (PET) is a relatively new area of study. PET is used in diagnosis, primarily in cardiology, neurology and oncology. A wide range of positron-emitting isotopes and compounds containing them are used in PET. For example, radiopharmaceuticals such as 18F-deoxyglucose are used to visualise target organs. Titanium-45 has been suggested as an isotope for PET because of its suitable energy and half- life. [1] It is not currently in use because its development in radiopharmaceuticals is limited by chemical disadvantages.
Titanium(IV) complexes are prone to hydrolysis, thus rendering them difficult to study and currently limiting their use as radiopharmaceuticals. In many cases, water causes the complex to break down too quickly for analysis to be easily performed. A number of different types of protecting ligands have previously been used in an attempt to slow or prevent hydrolysis.
This work reports the synthesis of a range of 1,4-diamino-2,3-butanediol ligands (dabdols) and their titanium(IV) complexes. These ligands have the structural framework shown in Figure 1. H H N N R R
HO OH Figure 1. Dabdol ligand.
The ligands fall into two categories: ligands with non-coordinating substituent arms (R in Figure 1 above) and those with coordinating arms. This synthetic procedure produces the meso-isomer. 1,4-Diamino-2,3-butanediols are potentially tetradentate, and have also been found capable of binding two metal ions, including monomeric complexes, by using each terminal amino group. This type of coordination may cause the vicinal hydroxyl functional group to deprotonate to form two 5-membered chelate rings. [2] They are also capable of bonding using three of the donor atoms, either NON or NOO. Details of the synthesis and properties of titanium(IV) complexes will be presented.
[1] J.C. Merrill, R.M. Lambrecht and A.P. Wolf, Int. J. App Radiation and Isotopes, 1978, 29, 115. [2] H. Kozlowski, B. Radomska, T. Kiss, A. Temeriusz, J. Stepinski, J. Coord Chem, 1993, 30, 215 – 219
IC-03 February 2-6, 2003 Melbourne 129 The new quasi-Laue Diffractometer at the Replacement Research Reactor. Wim T. Klooster Bragg Institute, ANSTO, PMB 1, Menai, NSW 2234, Australia.
The new single-crystal diffractometer for the Replacement Research Reactor will be a quasi- Laue diffractometer, similar to VIVALDI at ILL, France. It will be competitive with the best instruments currently available. Data collection times for a normal structure determination will be less than a day, a considerable improvement on current data collection times, typically a few weeks at HIFAR. Also, the crystal size needed for an experiment can as small as about 0.1 mm3, opening up new research areas where it has proved difficult to grow crystals sufficiently big (several mm3) which are currently needed. An area of research opening up will be multiple temperature and/or pressure measurements. This new instrument will be a useful tool to obtain structural information in a timely fashion, where x-rays do not provide enough detail. The instrument will be on the end of a thermal supermirror guide, and we are exploring the possibility of enhancing the flux further by using a converging guide section immediately before the instrument itself. More detailed information on the instrument will be presented.
IC-03 February 2-6, 2003 Melbourne 130 Determination of Chromium Oxidation States in Coordination Compounds by X-ray Absorption Spectroscopy
Aviva Levina and Peter A. Lay Centre for Heavy Metals Research, School of Chemistry, University of Sydney, Sydney 2006 NSW, Australia
[email protected] Analysis of the pre-edge and edge (XANES) features of X-ray absorption spectra provides a direct means for measuring the oxidation states of Cr in coordination compounds. In complexes with similar ligand environments, increase in the oxidation state of Cr leads to a shift of the edge position to higher energies and to an increase in the intensity of pre-edge absorbance due to a symmetry-forbidden 1s®3d transition (Figure 1) [1-3]. Precise values of metal-ligand bond lengths (which are also indicative of the metal oxidation state), as well as evidence for the integrity and purity of the used samples, are provided by multiple-scattering analyses of the XAFS regions of X-ray absorption spectra. We applied this approach to solve two long- standing controversies in Cr coordination chemistry, regarding the oxidation states of the metal n- ion in the complexes with redox-active ligands. Specroelectrochemical studies of the [Cr(cat)3] (n = 1-3, cat = catecholato(2-)) redox series led to the assignment of the oxidized forms of this complex as Cr(IV) and Cr(V) species (for n = 2 and 1, respectively), in contrast with the dominant opinion that the oxidation of Cr-catecholato complexes is exclusively ligand-based. Studies of a series of Cr nitroso complexes, which are often regarded as Cr(I)-NO+ species based on their magnetic properties, showed that the effective oxidation states in these complexes are close to Cr(III).
Figure 1. Typical XANES spectra of Cr complexes in 1.00 various oxidation states (frozen aqueous solutions, 10 Cr(VI) 2- K, [Cr] = 10 mM). Cr(VI) = [CrO4] ; Cr(V) = - Cr(IV) 0.75 [CrO(ehba)2] ; Cr(IV) = [CrO(ehbaH)]; Cr(III) = Cr(VI) + Cr(III) [Cr(ehbaH)2(OH2)2] (ehba = 2-ethyl-2-
Cr(V) hydroxybutanoato(2-)). 0.50 Cr(V) 0.10 Cr(IV)
0.25 0.05 Normalized Absorbance Cr(IV) 0.00 Cr(III) Cr(III) 5985 5990 5995 0.00
5980 6000 6020 Energy, eV
______[1] Codd, R.; Dillon, C. T.; Levina, A.; Lay, P. A. Coord. Chem. Rev. 2001, 216-217, 533- 577. [2] Levina, A.; Lay, P. A.; Foran, G. J. J. Chem. Soc., Chem. Commun. 1999, 2339-2340. [3] Pattison, D. I.; Levina, A.; Davies, M. J.; Lay, P. A. Inorg. Chem. 2001, 40, 214-217.
IC-03 February 2-6, 2003 Melbourne 131 Alkaloid Addiction: The Coordination Chemistry of Nicotine and Quinine William Lewisa and Peter J. Steela a Department of Chemistry, University of Canterbury, Christchurch, New Zealand [email protected]
Alkaloids are one of the four main sources of pure chiral materials from nature. They have however found little use as the basis for ligands for coordination chemistry. This poster examines some preliminary investigations into the chemistry of alkaloids which incorporate a heterocycle, namely nicotine (1) and quinine (2) (Figure 1). The metallosupramolecular and coordination chemistry of the relatively simple ligand nicotine with a number of different metals is investigated. Some of the coordination chemistry of quinine is also discussed.
H
H H HO N N H O N
N
(1) (2)
Figure 1 : Nicotine (1) and Quinine (2)
IC-03 February 2-6, 2003 Melbourne 132
Complexation of Alkali Metal and Alkaline Earth Ions by Anthracene Based Fluorophores with One and Two Appended Monoaza Coronand Receptors
Jason P. Geue, Nicholas J. Head, A. David Ward and Stephen F. Lincoln Department of Chemistry, The University of Adelaide, Adelaide, SA 5005, Australia. [email protected]
The complexation of alkali metal ions by 13-[2-(10-ethyl-9-anthryl)ethyl]-1,4,7,10-tetraoxa-13- azacyclopentadecane, 1, and 13-(2-{10-[2-(1,4,7,10-tetraoxa-13-azacyclopentadecanyl)ethyl]-9- anthryl}ethyl)-1,4,7,10-tetraoxa-13-azacyclopentadecane, 2, to form fluorescent complexes in acetonitrile is reported (Figure 1, [1]). The fluorescence quantum yields f = 0.25 and 0.03 for 1 -3 + and 2, respectively. At 298.2 K and I = 0.05 mol dm (NEt4ClO4) the [M1] complex are 5 4 characterised by complexation constants K1 = (1.28 ± 0.01) ´ 10 (f1 = 0.71), (9.27 ± 0.04) ´ 10 4 3 (f1 = 0.64), (1.73 ± 0.02) ´ 10 (f1 = 0.60), (3.08 ± 0.05) ´ 10 (f1 = 0.53) and (2.17 ± 0.04) ´ 3 3 -1 + + + 10 (f1 = 0.34) dm mol , respectively, as M changes from Li to Cs . Fluorophore 2 forms weakly fluorescent [M2]+ and possibly the “sandwich” complex, [M2']+, which are jointly 5 5 4 characterised by K1= (7.1 ± 0.03) ´ 10 , (5.2 ± 0.3) ´ 10 , (1.00 ± 0.03) ´ 10 and (1.8 ± 0.2) ´ 4 3 -1 + + + + 2+ 4 10 dm mol for Li , Na , K and Rb and [M22] characterised by K2 = (6.41 ± 0.01) ´ 10 (f2 4 3 2 3 = 0.73), (4.84 ± 0.01) ´ 10 (f2 = 0.53), (1.59 ± 0.06) ´ 10 (f2 = 0.39) and (6.8 ±. 0.1) ´ 10 dm -1 + mol (f2 = 0.15). (Cs induced insufficient fluorescence in 2 for quantitative study.) The alkaline 7 3 -1 earths form more stable complexes with 1 and 2 characterised by K1 and K2 ³ 10 dm mol . The factors governing metal ion modulation of photoinduced electron transfer (PET), fluorescence and complex stability are discussed. m+ 2m+ m+ O O O O O O O O O O O O O O m + O O O O O M M O O O O N N N M N O ' K1 N K1 K2 N m+ + M '' + M m+ + M m+ M K1
m+ N O - M O O - Mm+ - Mm+ O m+ [M2']m+ N N m+ N 2m+ 1 [M1] [M2] M [M 22] O O O O O O O O O O O O K1 = K1'(1 + K 1'') 2 Figure 1. Equilibrium schemes for flurophores 1 and 2 and for Mm+ modulation of photoinduced electron transfer PET.
[1] J. P. Geue, N. J. Head, A. D. Ward and S. F. Lincoln, J. Chem. Soc., Dalton Trans., accepted for publication.
IC-03 February 2-6, 2003 Melbourne 133 Colourful and Exciting Chemistry: electrochromism and excited state studies of cyano-bridged mixed valence complexes. Paul V. Bernhardt and Brendan P. Macpherson Department of Chemistry, University of Queensland, Brisbane 4072, Australia. [email protected] Research in cyano-bridged complexes has been driven in recent years by interest in molecular magnetism, molecular electronics and electrochromism. Many cyano- bridged mixed valence complexes exhibit relatively intense metal-to-metal charge transfer (MMCT) transitions between donor and acceptor moieties. Electrochromism can be achieved through oxidation of the donor or reduction of the acceptor.
We have developed a series of electrochromic compounds comprising macrocyclic III II - cobalt complexes bridged to cyano metal centres ([LCo (µ-NC)M (CN)5] , L - pentadentate macrocyclic ligand; M=Fe, Ru) with MMCT transitions (M(II) ? Co(III)) in the visible and near ultraviolet region of the spectrum. [1] The energy of the MMCT band (and hence the colour of the complex) can be tuned (by up to ca. 7500 cm-1) by making changes to the macrocyclic ligand and cyano metal centre.
14 III II Figure: Oxidation of Na[L Co NCFe (CN)5] with K2S2O8. Spectrum taken every 2 mins.
Electrochemical reactions upon the metal centres (M(II) ? M(III) or Co(III) ? Co(II)) lead to the loss of the MMCT transition, and subsequent spectroscopic changes are observed. The reversible electrochromic reactions make these complexes candidates for use in an electrochromic device, and research to this end is current being pursued.
[1] P. V. Bernhardt, and M. Martinez, Inorg. Chem., 1999, 38, 424-425. P. V. Bernhardt, B. P. Macpherson, and M. Martinez, Inorg. Chem., 2000, 39, 5203-5208. P. V. Bernhardt, B. P. Macpherson, and M. Martinez, J. Chem. Soc. Dalton Trans., 2002, 1435-1441.
IC-03 February 2-6, 2003 Melbourne 134 Electrochemically Driven Reversible Solid State Metal Exchange Processes in Polynuclear Copper Complexes Frank Marken, Sarah Cromie, Vickie McKee Department of Chemistry, Loughborough University, Loughborough, LE11 3TU, UK [email protected] The electrochemical characteristics of polynuclear di-copper and tetra-copper complexes of an expanded ‘Robson-type’ macrocyclic ligand are explored by solid state voltammetry in aqueous media. When adhered to a graphite electrode surface in form of a microcrystalline powders and immersed in aqueous buffer solution, these water insoluble polynuclear copper complexes show well-defined voltammetric reduction and re-oxidation responses.
The di-copper metal complexes [Cu2(H3L)(OH)][BF4]2 and the tetra-copper complexes
[Cu4(L)(OH)][NO3]3 with the O4N4-octadentate macrocyclic ligand L (see Structure) are shown to exhibit inter-related and proton concentration sensitive solid state voltammetric characteristics. At sufficiently negative potential, copper is extracted from the complexes to form a solid copper deposit and the neutral form of the insoluble free ligand. Upon re-oxidation of the copper deposit, Cu2+ undergoes facile re-insertion into the ligand sphere to re-form solid di- and tetra-copper complexes at the electrode surface. The reduction process occurs in two stages with two Cu2+ cations being extracted in each step. The ability of the macrocyclic ligand to efficiently release and accumulate copper is demonstrated.
Figure 1. Structure and schematic diagram showing the electrochemically driven copper extraction and re-insertion process.
[1] F. Marken, S. Cromie, and V. McKee, J. Solid State Electrochem., 2003, in print.
IC-03 February 2-6, 2003 Melbourne 135 Electrochemically Driven Ion Exchange at Microdroplets with Liquid|Liquid|Solid Triple Interfaces Frank Marken, Colin M. Hayman, Philip C.B. Page Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK. [email protected] Electro-insertion of ions is a well-known phenomenon, which allows the transfer of anions or cations across phase boundaries to be driven and monitored electrochemically. It is shown here that even extremely hydrophilic anions, such as phosphate and arsenate, can undergo electro- insertion at organic redox liquid | water | electrode triple interfaces [1]. These anions can be forced electrochemically to transfer into droplet deposits [2] to give new ionic liquid phases.
The transfer process of phosphate anions from aqueous buffer solutions into organic microdroplets of the redox liquid N,N,N’,N’-tetraoctylphenylene- diamine [3] is pH and concentration sensitive. It is shown that phosphate is transferred in the form of - PO4HK in the presence of phosphate buffer. Two distinct potential regions are identified and attributed to (I) interfacial redox processes at the liquid | liquid interface associated with deprotonation and (II) bulk redox processes associated with anion transfer from the aqueous to the organic phase. The comparison of Figure 1. Schematic of potential dependent ion phosphate and arsenate electro-insertion processes exchange processes in a droplet of redox liquid. suggests that arsenate is less hydrophilic and transferred into the organic phase preferentially.
[1] F. Marken, R.D. Webster, S.D. Bull, S.G. Davies, J. Electroanal. Chem., 1997, 437, 209.
[2] F. Marken, C.M. Hayman, P.C.B. Page, Electroanalysis, 2002, 14, 172.
[3] F. Marken, C.M. Hayman, P.C.B. Page, Electrochem. Commun., 2002, 4, 462.
IC-03 February 2-6, 2003 Melbourne 136 Osmium-silsesquioxane as catalyst for dihydroxylation reactions.
Paolo P. Pescarmona,a,b A.F. Masters,a J.C. van der Waal,b T. Maschmeyer,b J.K.Beattie.a a School of Chemistry, F11, The University of Sydney, NSW 2006 Australia. b Laboratory of Applied Organic Chemistry and Catalysis, DelftChemTech, TU Delft, Julianalaan 136, 2628 BL Delft, The Netherlands. Fax: +(31)152784289 e-mail: [email protected]
Osmium tetroxide (OsO4) is considered (one of) the best catalysts for the cis-dihydroxylation of double bonds.1 catalyst HO O H
The disadvantage of using this compound for R H 2 O R homogeneous catalysis lies in its high volatility and toxicity. Therefore, many attempts have been carried out to immobilise osmium tetroxide on different supports. Recently, an efficient and robust heterogeneous catalyst was obtained by binding an Os centre to a tetrasubstituted S iO 2 O O Si O 2 O sO 4 olefin covalently linked to a O s 2 silica support. The O O tetrasubstituted diolate ester which is obtained at one side of the Os centre is stable and provides the connection to the silica support. The remaining Os co-ordination site is available for the catalytic reaction.
Here, we present the synthesis of a silsesquioxane3-based homogeneous analogue of this silica-supported osmium complex. O R O O O Cyclopentylsilsesquioxane Si O Si N O Os a7b3 was functionalised R O O Si Si R O O with an O O aminopropylsiloxane. The O O R Si O Si compound obtained was O O R Si Si reacted with a O R R tetrasubstituted olefin and finally with the osmium tetroxide in presence of an excess of cyclohexene. The Os-silsesquioxane was characterised and tested for activity in dihydroxylation reactions. The complex is both a model compound for the silica-supported catalyst and an active homogenous catalyst itself. The dihydroxylation of cyclopentene and cyclohexene were used as test reactions: after 3 hours reaction a TONcyclopentene of 130 and a TONcyclohexene of 414 could be observed. In both cases, the catalyst is more active than the heterogeneous analogue.
1 M. Schroeder, Chem. Rev., 80 (1980) 187. 2 A. Severeyns, D.E. De Vos, L. Fiermans, F. Verpoort, P.J. Grobet, P.A. Jacobs, Angew. Chem. Int. Ed., 40 (2001) 3586. P. P. Pescarmona, T. Maschmeyer, Aust. J. Chem., 54 (2001) 583.
IC-03 February 2-6, 2003 Melbourne 137 Preparation And Properties Of New Ruthenium Cyclopentadienyl Complexes Peter C. Healy, Leanne S. Micallef, Michael L. Williams School of Science, Griffith University, Kessels Road, Nathan 4111, Brisbane, Australia. [email protected] The introduction of functional groups to the cyclopentadienyl ligand of metallocenes is known to significantly affect the physical and chemical properties of these compounds. We will be reporting the synthesis of a range of cyclopentadienyl ruthenium complexes containing electron- withdrawing groups.
Acid catalysed hydrolysis of the previously known penta-methoxy complex, 5 5 [Ru(h -C5H5){h -C5(CO2Me)5}], gives the highly water soluble penta-carboxylic acid complex 5 5 in good yield. Similarly, acid catalysed reactions of [Ru(h -C5H5){h -C5(CO2H)5}] with simple 5 5 alcohols (R-OH) have yielded a range of new esters, [Ru(h -C5H5){h -C5(CO2R)5}], where R =
-CH2CH3, -(CH2)2CH3, -CH(CH3)2, -(CH2)7CH3, in good yields. Each of these new esters are 5 5 liquids. The penta-amide complex, [Ru(h -C5H5){h -C5(CONH(CH2)2CH3)5}] (1), was prepared 5 5 by refluxing [Ru(h -C5H5){h -C5(CO2Me)5}] in n-propylamine. The penta-amide, while soluble in organic solvents, is partially soluble in water, from which crystals were grown to produce the structure shown.
A range of new penta-substituted complexes including amides, amines, alcohols and esters will also be reported.
(1)
IC-03 February 2-6, 2003 Melbourne 138 Switchable Cycloplatinated Ferrocenylamine Derivatives of Acridone, Naphthalimide and Anthraquinone Joy Morgan, C. John McAdam, Elise McGale, Eva Murray, Brian Robinson and Jim Simpson Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand [email protected]
Acridone, naphthalimide and anthraquinone derivatives of the cycloplatinated ferrocenylamine {1, Pt[(h5- 5 CpFe(s,h -C5H3CH2NMe2)](dmso)X} [1] have been prepared and the X-ray structure for the anthraquinone derivative has been determined.
NMe2 Pt X s - donor
Fe dmso
p - acceptor
X = Cl 1a, C CH 1b, C CPh 1c
Spectroelectrochemistry has been used to probe the ground and excited states of these molecules. Irrespective of whether the fluorophore is bound to the ethynylPt(II) link via a nodal nitrogen (acridone) or to the aromatic ring (naphthalimide and anthraquinone) fluorophore emission is quenched in the ground state and partially restored in the oxidised species. Low energy donor- acceptor CT bands of the oxidised compounds are characteristic.
[1] C.E.L. Headford, R. Mason, P.R. Ranatunge-Bandarage, B.H. Robinson and J. Simpson, J Chem. Soc., Chem. Commun., 1990, 601; P.R.R Ranatunge-Bandarage, B.H. Robinson and J. Simpson, Organometallics. 1994, 13, 500.
IC-03 February 2-6, 2003 Melbourne 139 Zinc Saccharate: A Chiral, Three Dimensional Polymer Containing Two Types of Channel – the first Hydrophilic, the second Hydrophobic. Brendan Abrahams, Michael Moylan, Simon Orchard and Richard Robson School of Chemistry, University of Melbourne, Victoria, 3010. [email protected]
Reaction of monopotassium saccharate [KO2C(CHOH)4CO2H] with zinc acetate produces a three- dimensional coordination polymer of composition ZnC6H8O8.2H2O consisting of zigzagging pillars of zinc linked by saccharate ligands. Channels with square cross-section are formed with metals occupying the corners and ligands generating the edges.
There are two types of channels in the structure, and they provide remarkably different chemical environments. The channels alternate like the black and white squares on a chessboard. The hydroxy groups attached to the two central carbons of the ligands surrounding the first channel are directed into that channel. The neighbouring channel is lined with the carbons and hydrogens from the ligand. This arrangement renders the first channel hydrophilic and the second hydrophobic in character.
Solvent water occupies both channels, but the water in the hydrophobic channel is easily removed and can be replaced without disrupting the host. The poster will describe the structure of zinc saccharate and it will discuss the successful introduction of several small non-polar guests such as
I2, azobenzene, cyclooctatetraene and CI4 into the hydrophobic channel.
IC-03 February 2-6, 2003 Melbourne 140
Ag(I) and Pd(II) complexes of an ether-functionalised bis-(nucleophilic heterocyclic carbene) ligand.
David J. Nielsen,† Kingsley J. Cavell,‡* Brian W. Skelton§ and Allan H. White§ † School of Chemistry, University of Tasmania, GPO Box 252-75, Hobart, Tasmania, 7001, Australia. Current address: School of Chemistry, University of Melbourne, Parkville, 3010, Victoria, Australia. ‡* Corresponding Author. Department of Chemistry, Cardiff University, PO Box 912, Cardiff, CF10 3TB, UK. Email: [email protected]. Fax: +44 29 20875899. § Department of Chemistry, University of Western Australia, Nedlands, Western Australia, 6907, Australia. [email protected], [email protected] The functionalised bis-imidazolium salt bis[2-(3-methylimidazolium-1-yl)ethyl] ether di-iodide (1) has been synthesised as precursor to the corresponding bis-NHC ligand. 1 reacts readily with
Ag2O in 1:10 MeOH:DCM yielding a Ag(I)-NHC complex that may be isolated as the tetrafluoroborate (2) and triflate (3) salts following anion substitution in MeCN. A single crystal X-ray crystallographic determination performed on the triflate salt 3 showed that the compound
exists as an equal mixture of two dinuclear [Ag2L2].2(OTf) complexes that differ by the relative
orientations of the two C-Ag-C vectors. Treatment of 2 with PdCl2(MeCN) in DMSO gives the
monomeric cationic Pd(II) complex [PdClL(MeCN)]BF4 (4). The structure of complex 4 has been confirmed by X-ray crystallography and the NHC groups adopt a mutually cis orientation. The oxygen atom of the ether functionality remains well removed from the metal coordination
.OTf .OTf
¬ 3 ®
.BF4
4
sphere in both 3 and 4.
IC-03 February 2-6, 2003 Melbourne 141
INTERACTIONS OF PROXIMATE AMINO ACID RESIDUES IN POLYAZA MACROCYCLIC SYSTEMS
Sally E. Plush,a Stephan F. Lincolna and Kevin P. Wainwrightb aAdelaide University, South Australia, 5005, Australia bFlinders University, South Australia, 5001, Australia
The development of polyaza macrocycles with pendant arms as enzyme mimics is of great interest both chemically and biologically. We aim to develop a series of water soluble polyaza macrocyclic ligands bearing donor pendant arms derived from amino acids.
The ligands are prepared by substituting [9]aneN3 and [12]aneN4 macrocycles with N- bromoacetyl-L-phenylalanine methylester monomer units.[1] Hydrolysis of the methyl ester groups with hydroxide yields the water soluble acid derivatives, [9]aneN3-Lphe-OH and
[12]aneN4-Lphe-OH.
R O O NH NH O R O O N R O H N N O R N N NH N N R = OMe O N O H OH R N O O HN NH R O
O O R
[9]aneN3-Lphe-R [12]aneN4-Lphe-R Potentiometric titrations on these ligands show a strong coordination with the metal ions of Cu2+, Zn2+ and Cd2+, exhibiting preferential binding towards Cu2+. Analysis of the stereochemical nature of the ligands by NMR spectroscopy revealed that inversion around the nitrogen centre of the macrocyclic ring occurs to produce two diastereomers. On binding of both Zn2+ and Cd2+ the rate of inversion was slowed such that the individual protons on the arms could be distinguished. Thus incorporation of chiral amino acids as pendant arms induces homochirality in both the substituted [9]aneN3 and [12]aneN4 systems. This is important for chiral recognition studies such as those involving molecular recognition of host guest complexes. Metal complexes of the water soluble ligands are being studied as potential MRI agents and enzyme mimics.
[1] Watson, A.A., A.C. Willis, and D.P. Fairlie, Organization of Amino Acids Using a Metallotirazacyclonoane template. Inorg. Chem., 1997. 36: p. 752-753.
IC-03 February 2-6, 2003 Melbourne 142 Exploration of the Reactivity of Pt(II) Toward “Activated” Aryl and Alkynyl Halides using Diorganoiodine(III) Reagents Allan J. Canty,a Thomas Rodemann,a Brian W. Skeltonb and Allan H. Whiteb a School of Chemistry, University of Tasmania, 7001, Tasmania, Australia b Chemistry, University of Western Australia, Crawley, 6009, Western Australia, Australia. [email protected]
II The reaction of diphenyliodonium triflate with Pt Me2(bipy) resulted in an aryl group transfer to IV the Pt(II) centre to yield Pt Me2Ph(O3SCF3)(bipy) (1) [1]. This reaction is most likely initiated by a nucleophilic attack by the metal at the iodine(III) centre followed by an extrusion of an iodoarene, although iodine(III) reagents also undergo free radical reactions [2]. No regioselectivity of the aryl transfer was observed when (p-C6H4I)PhI(O3SCF3) was used as an example of an asymmetric diaryliodonium triflate and the corresponding Pt(IV) complexes 1 and 2 were obtained as a 1:1 mixture. The use of Ph(Me3SiCºC)I(O3SCF3) resulted in the formation of two isomers 4 and 5 at 20°C in a ratio of 2:1 respectively. However, this reaction seems to proceed via a different mechanistic pathway. The observation of an intermediate of type 3 at low temperature indicates that the initial nucleophilic attack takes place at the electron deficient b-carbon followed by the loss of iodobenzene [3]. I
acetone Me N Me N PtMe2(bpy) + (p-C6H4I)PhI(O 3SCF3) Pt + Pt -60°C Me N Me N
F3CSO3 F3CSO3 1 2
C SiMe3
acetone Me N PtMe2(bpy) + Ph(Me3SiC C)I(O3SCF3) Pt -60°C Me N
SiMe3 F3CSO3 3 Me NaI, Me3Si +20°C N Me N Pt + Pt Me N Me N I I 4 5
[1] A. Bayler, A.J. Canty, J.H. Ryan, B.W. Skelton, and A.H. White, Inorg. Chem. Commun., 2000, 3, 575.
[2] V.V. Grushin, Acc. Chem. Res., 1992, 25, 529.
[3] M.D. Bachi, N. Bar-Ner, C.M. Crittell, P.J. Stang, and B.L. Williamson, J. Org. Chem., 1991, 56, 3912.
IC-03 February 2-6, 2003 Melbourne 143 Electron transfer reactions with polyoxometalates Markus Schatz, Peter A. Tregloan and Anthony G. Wedd School of Chemistry, University of Melbourne, 3010, Victoria, Australia [email protected] Polyoxometalates are an important group of metal-oxygen clusters formed by early transition metals such as Mo, W and V. They exhibit varied structures, rich redox chemistry, photochemistry and an ability to catalyse a wide range of industrially and biologically significant reactions.[1]
4- The availability of salts of the polyoxo anions [S2M18O62] (M = Mo, W) in different oxidation levels (0, 1, 2, 3 and 4 electron-reduced) provides a resource to study the mechanism of a number of reactions involving electron transfer. Direct study of the redox reactions of well- characterised polyoxo anions is rare, and the mechanism of the outer sphere electron transfer reaction below has proved to be surprisingly complex.[2] 5- 4- 4- 5- [S2W18O62] + [S2Mo18O62] ® [S2W18O62] + [S2Mo18O62] In this report the “simpler” reagents ferrocene and decamethylferrocene have been used for the reduction of the polyoxo anions. From low temperature stopped-flow studies we have shown that 4- the reaction of equimolar amounts of [S2Mo18O62] and decamethylferrocene lead to an initial 2 e- reduction of polyoxo species. Subsequently a comproportionation reaction between 4- 6- - [S2Mo18O62] and [S2Mo18O62] occurs which leads to the 1 e reduced final product 5- [S2Mo18O62] .
4- Stopped-flow studies of the reaction of [S2Mo18O62] with ferrocene showed several reaction steps. The last step to form the green product takes several minutes at room temperature.
High pressure electrochemistry can be used to determine activation and reaction volumes of redox reactions. These reflect changes in the structure of solute species and of solute-solvent interactions.[3] Experiments using high pressure cyclic voltammetry on the polyoxo anion 4- [S2W18O62] have been carried out. The pressure dependence of all six redox processes can be resolved in a single experiment. The results of this work will be presented and discussed.
[1] Pope, M. T.; Müller, A. Angew. Chem. 1991, 103, 56-70 [2] Richardt, P. J. S.; Gable, R. W.; Bond, A. M.; Wedd, A. G. Inorg. Chem. 2001, 40, 703- 709 [3] Swaddle, T.W.; Tregloan, P.A. Coord. Chem. Rev. 1999, 187, 255-289
IC-03 February 2-6, 2003 Melbourne 144 Alkyne Coupling Reactions Mediated by Ruthenium(0): Formation of Functionalised Macrocycles Anthony F. Hill, A. David Rae, Madeleine Schultz and Anthony C. Willis Research School of Chemistry, Australian National University, 0200, ACT, Australia
[email protected] The coupling of alkynes mediated by transition metal complexes has been studied extensively, particularly for cobalt, zirconium and iron. Alkyne coupling reactions typically proceed via the formation of metallocyclopentadienes (Scheme 1). These may then react further in the absence of substrates to form metal- coordinated cyclobutadienes (path A), or insert small molecules, leading to substituted cyclic dienes (path B).
Less well studied is the coupling of alkynes mediated by ruthenium. We are currently investigating alkyne binding and coupling Scheme 1. Typical pathways for alkyne coupling mediated by transition metals. using Roper's Ru(CO)(L)(PPh3)3 complexes
(L = CO, 2,6-Me2C6H3NC) as precursors. These complexes are known to lose one PPh3 ligand readily in solution to generate a reactive, coordinatively unsaturated 16 electron fragment.[1]
The binding of alkynes to the "Ru(CO)(L)(PPh3)2" fragment is dependent on the electronic nature of the substituents on the alkyne; thus far, adducts have been observed only for alkynes bearing phenyl rings. Density functional calculations are being used to study alkyne binding, and the implications of these results will be discussed.
It has been reported that with the tricarbonyl precursor, Ru(CO)3(PPh3)2, carbon dioxide pressure is required for alkyne coupling to occur. A cationic Ru(II) species formed via reductive disproportionation of CO2 was postulated as an intermediate.[2] In our system, heating the isolated alkyne adducts Ru(CO)2(PPh3)2(RCCR) under nitrogen with free alkynes leads to coupling; the products of a series of such reactions will be described.
Coupling of a diyne results in a bicyclic system. Thus, the thioether-containing diyne 4,7,10-trithiatrideca-2,11-diyne reacts with Ru(CO) (PPh ) at room temperature to form 2 3 3 Figure 1. Molecular structure of 1. 4 Ru(CO)(PPh3){h ,k(S)-CO(MeC=CSCH2CH2)2S} (1) (Figure 1). The facile nature of this reaction suggests that coordination of a sulfur donor atom promotes coupling. The potential synthesis and utility of substituted [9]aneS3 ligands will be addressed.
[1] B. E. Cavit, K. R. Grundy, and W. R. Roper, J.C.S. Chem. Comm.., 1972, 60-61.
[2] S. Yamazaki and Z. Taira, J. Organomet. Chem., 1999, 578, 61-67.
IC-03 February 2-6, 2003 Melbourne 145 Linking ferrocene to polyaromatic hydrocarbons via alkene and alkyne spacers. R.B.T. Connelly,a John F. Gallagher,b Richard A. Hudsonc, S. Jenningsc Anthony R. Manningc, C. John McAdama, Brian H. Robinsona and Jim Simpsona. a Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand. b School of Chemical Sciences, Dublin City University, Dublin 9, Ireland c Department of Chemistry, University College Dublin, Belfield D4, Dublin, Ireland. [email protected] Efficient energy transfer between redox- or photo-active centres is an important goal for materials incorporating organometallic species because of their potential technological applications. To this end we report the synthesis and crystallographic characterisation of a series of molecules in which the redox centre ferrocene is linked to polyaromatic fluorophores via alkene and/or alkyne bridges as shown below.
Fc PAH Fc PAH
5 5 PAH = Fc = (h -C5H5)Fe(h -C5H4)
B3LYP calculations on the majority of these systems predict global minima in which the polycyclic aromatic group is approximately coplanar with the substituted ferrocenyl ring. However the solid state structures reveal that that the polyaromatic systems are generally orthogonal to this ring. These differences may result from the presence of columnar interactions in the solid state. These involve the hydrocarbon moieties, via offset p-stacking which involves parallel displacement of the aromatic rings. This mode of stacking is pervasive throughout the series but can be subtly altered and/or attenuated by the nature of the aromatic system.
The structure of the 2:1 complex of Fc-CH=CH-C14H9 with TCNQ, a potential molecular metal, is stabilised by both columnar and hydrogen bonding interactions in the solid state.
IC-03 February 2-6, 2003 Melbourne 146 Redox Interplay of Oxo–thio–tungsten Centres with Sulfur–donor Co–ligands
Stephen Sproules,a Jason P. Hill,a Jonathon M. White,a Graham N. Georgeb and Charles G. Younga a School of Chemistry, University of Melbourne, 3010, Victoria, Australia b Stanford Synchroton Radiation Laboratory, SLAC, Stanford University, Stanford, CA 94309 [email protected]
Metal-sulfur compounds have important technological applications and are employed as catalysts for many industrial processes.[1,2] Moreover, metal–sulfur centres play vital roles in biological electron transport and enzyme catalysed reactions.[2,3] Redox interplay of the metals and sulfur can result in counter–intuitive reactions and the chemical modification of sulfur– containing ligands and reagents.
S C
O S N W
N N N
+ Figure 1. Structure of [Tp*WO(S2py)]
This paper outlines the synthesis and characterisation of Tp*WOS(pyS) and Tp*WOS(S2PR2) (R = Ph, OEt) and the effects of one electron oxidation and reduction processes on both complexes. Oxidation and reduction leads to W(V) species, through direct or induced internal redox reactions. Chemical oxidation of Tp*WOS(pyS) permits the isolation of [Tp*WO(pyS2)](BF4) (Figure 1). The complexes are characterised by spectroscopy, including XAS and crystallographic techniques.
[1] A. Muller, B. Krebs, Sulfur, Its Significance for Chemistry, for the Geo-, Bio-, and Cosmosphere and Technology, Elsevier: Amsterdam, 1984. [2] E. I. Stiefel, K. Matsumoto, Transition Metal Sulfur Chemistry, Symposium Series 653, American Chemical Society: Washington, DC, 1996. [3] E. I. Stiefel, Chem. Soc., Dalton Trans. 1997, 3915.
IC-03 February 2-6, 2003 Melbourne 147 Photoluminescence Properties of Four-Coordinate Gold(I)–Phosphine Complexes of the Types [Au(diphos)2]PF6 and [Au2(tetraphos)2](PF6)2
Christopher D. Delfs,a Heather J. Kitto,b Robert Stranger,a Gerhard F. Swiegers,c S. Bruce Wild,b Anthony C. Willis,b and Gerard J. Wilsona a Department of Chemistry, The Faculties, Australian National University, Canberra, ACT 0200, Australia. b Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia. c CSIRO Molecular Science, Bag 10, Clayton, VIC 3169, Australia.
[email protected] Numerous reports describe the photoluminescence of two- and three-coordinate gold(I)– phosphine complexes, but emission in their analogous four-coordinate complexes is almost unknown. This work examines the luminescence of tetrahedral gold(I) complexes of the
types [Au(diphos)2]PF6 (diphos = 1,2-bis(diphenylphosphino)ethane, 1) and
[Au2(tetraphos)2](PF6)2 (tetraphos = (R*,R*)-(±)/(R*,S*)-1,1,4,7,10,10-hexaphenyl- 1,4,7,10-tetraphosphadecane, (R*,R*)-(±)/(R*,S*)-2). While non-emitting in solution,
these complexes luminesce with an intense yellow color (lmax 580–620 nm) at 293 K in the solid state or when immobilized as molecular dispersions within solid matrices. The excited state lifetimes of the emissions (t 4.1–9.4 ms) are markedly dependent on the inter- and intra-molecular phenyl–phenyl pairing interactions present. At 77 K in an ethanol
glass, two transitions are observed, a minor emission at lmax 415–450 nm and a major
emission at lmax 520-595 nm; for [Au(1)2]PF6, lifetimes of t 251.0±20.5 ms was determined for the former transition and t 14.9±4.6 ms for the latter. Density functional theory (DFT) calculations and comparative studies indicate that the former of these emissions involves triplet LMCT p*(Ph)? Au(d)-P(p) transitions associated with individual P-phenyl groups. The latter emissions, which are the only ones observed at 293 K, are assigned to LMCT p*(Ph-Ph)?Au(d)-P(p) transitions associated with excited P-phenyl dimers. Other tetrahedral gold(I)–phosphine complexes containing paired P-Ph substituents display similar emissions. The corresponding phosphine ligands, whether free, protonated, or bound to Ag(I), do not exhibit comparable emissions. Far from being rare, luminescence in four-coordinate Au(I)–phosphine complexes appears to be general when stacked P-phenyl groups are present.
IC-03 February 2-6, 2003 Melbourne 148
Multidimensional Lanthanoids frameworks with 2,5-pyrazinedicarboxylic acid Appadurai Thiyakesan, Cameron J. Kepert School of Chemistry, The University of Sydney, NSW 2006, Australia [email protected] The design of metal-organic frameworks with specific topologies has attracted much attention in recent years, yet it has proven challenging to synthesise an ideal compound which is robust and porous[1]. Here we report several new framework structures constructed from lanthanoids and bis-bidentate 2,5-pyrazinedicarboxylic acid (pzdc). By varying synthetic techniques we were able to construct one-, two- and three-dimensional frameworks.
Figure 1. Porous three-dimensional coordination network (left) and single hexagonal pore (right)
of {[Sm(pzdc)1.5(H2O)2].4H2O}n Hydrothermal syntheses have yielded both one- and three-dimensional structures, while slow diffusion gave a two-dimensional layered material. In the two- and three-dimensional frameworks the hexagonal layers define pores with dimensions of 9 ? 9 Å and 8 ? 11 Å respectively. The guest-exchange properties of these porous frameworks have been investigated through thermogravimetric and X-ray diffraction studies.
[1] C.J. Kepert, T.J. Prior, M.J. Rosseinsky, J. Am. Chem. Soc. 2000, 122, 5158-5168.
IC-03 February 2-6, 2003 Melbourne 149 Transition Metal Cluster Compounds Containing Chalcogenide Ligands David Cookson,a Mark G. Humphrey,b Nigel T. Lucas,b Brian W. Skelton,c Vicki-Anne Tolhurst,d Peter Turnere and Allan H. Whitec a ChemMatCARS, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA. b Department of Chemistry, Australian National University, Carberra 0200, ACT Australia. c Department of Chemistry, University of Western Australia, Crawley, 6009, WA, Australia. d School of Chemistry, University of Tasmania, Private Bag 75, Hobart 7001, TAS, Australia. e School of Chemistry, The University of Sydney, Sydney 2006, NSW, Australia. [email protected] Interest in the chemistry of metal chalcogenide clusters has increased due to the realisation of their possible applications in material sciences. As the optical and electronic properties of materials prepared from these clusters vary depending on the size and structure of these clusters, it is of interest to prepare new compounds of as yet unknown stoichiometry and structure. The number of metal chalcogenide cluster compounds prepared using conventional solution phase methods are small compared to the number of species observed in the gas phase using mass spectrometric methods.[1]
Here we report the preparation of a number of transition metal chalcogenide cluster compounds. The structures of several compounds have been elucidated using single crystal X-ray diffraction. Where possible, multinuclear NMR spectroscopy has been used to help correlate trends seen in solution spectra with bonding trends seen in the solid state. We have also investigated the optical properties of some organometallic manganese chalcogenide cluster compounds, the results of which will be reported.
Molecular projection of [Ru3(m-Cl)3(m3-Cl)(m3-S)(PPh3)6]
[1] I.G. Dance, and K. Fisher, Prog. Inorg. Chem., 1994, 41, 637; and references therein.
IC-03 February 2-6, 2003 Melbourne 150 Structural, Magnetic and Supramolecular Properties of Anionic Dicyanamide Coordination Polymers Patricia M. van der Werff,a Stuart R. Batten,a Paul Jensen,a Boujemaa Moubaraki,a Keith S. Murraya a School of Chemistry, Monash University, 3800, Victoria, Australia patricia.vanderwerff@ sci.monash.edu
- The polydentate ligand dicyanamide (dca, N(CN)2 ) is being widely used to produce coordination - polymers with novel structural and magnetic properties. In this research anionic species M(dca)3 2- and M(dca)4 have been synthesised using cation and solvent templation methods. Several structures were obtained, displaying octahedral geometry about individual d-block ions (Mn, Fe, Co, Ni) and ligand coordination through the nitrile nitrogens. Complexes of the type - (Ph4E)[M(dca)3], (E = P, As,) [1] [2] show extended anionic M(dca)3 2D (4,4) sheets, separated + by layers of Ph4E cations. The species (Ph4As)2[M2(dca)6H2O]·H2O·xMeOH (M = Ni, Co) [1] are ladder-like 1D polymers, cross-linked by hydrogen bonding into sheets and separated by layers of cations. The complexes (MePh3P)[M(dca)3] (M = Ni, Co, Fe, Mn) consist of 3D anionic - M(dca)3 networks of metal atoms, the cations occurring in pairs within the cavities. The nickel(II) complex (Ph4As)[Ni(dca)3] (see below), displayed long-range magnetic order (Tc = 20.1K) [1], while the other complexes showed weak antiferromagnetic coupling [1, 2]. Factors affecting the network topology include subtle cation-cation and cation-anion interactions, charge and size complementarity between cations and the repeat unit of the anionic network, and solvent inclusion. While the role of the cations in these complexes has been as a templating agent for crystal growth, the prospect of introducing cations with other properties (eg Non-Linear Optical (NLO) activity or conductivity), opens the way to producing dual function materials.
Recent use of an NLO cation, yielded
[(Me2NPh)Ph3P][Mn(dca)3].(CH3)2CO, a 2D (6,3) anionic net of doubly bridged metal atoms. Use of a paramagnetic cation has yielded the complexes [(C5Me5)2Fe][M(dca)3] M= Mn, Co, Ni, Cd. Preliminary investigations indicate long range order in the complex [(C5Me5)2Fe)][Ni(dca)3] (TC = 18K). . Figure 1. [(Me2NPh)Ph3P][ Mn(dca)3] (CH3)2CO
[1] P. M. van der Werff, S. R. Batten, P. Jensen, B. Moubaraki, K. S. Murray, E. H. -K Tan, Polyhedron, 2001, 20, 1129-1138.
[2] P. M. van der Werff, S. R. Batten, P. Jensen, B. Moubaraki, K. S. Murray Inorg. Chem., 2001, 40, 1718-1722.
IC-03 February 2-6, 2003 Melbourne 151 Solid State and Molecular Modelling Studies of the pH Dependance Between Azamacrocycles and Phosphates
Andrew C. Warden, Mark Warren, Leone Spicciaa School of Chemistry, PO Box 23, Monash University, Victoria 3800, Australia [email protected] The supramolecular chemistry of anions plays a vast and many-faceted role in both inorganic and biological systems[1]. Pyrophosphates and phosphates in particular have been studied as guests in a wide variety of host-guest complexes owing to their biological and environmental significance. Recent work by Bazzicalupi et al[2] has shown that the macrocycle 1,4,7,10,13,16- hexaazacyclooctadecane ([18]aneN6) binds, among others, inorganic and organic phosphates in solution through thermodynamics experiments utilizing NMR titration techniques, however very few corroborating examples of phosphates bound to polyammonium macrocycles in the solid state can be found in the literature. We have been examining the host-guest interactions between [18]aneN6 and phosphoric acid over a broad pH range using X-ray crystallography. The macrocycle binds both - 2- H2PO4 and HPO4 anions in the solid state. Whilst it has been found in previous work that these systems exist in 1:1 host-guest complexes in solution, each macrocycle binds at least two crystallographically unique phosphate anions in the solid state. We have determined the structures of four complexes formed at pH’s 1, 3, 6 and 8. This has allowed an assessement of the nature of H-bonding interactions that occur in these systems and how this varies with the degree of protonation of the host and guest molecules. The structural information is being used as a starting point for molecular dynamics simulation and energy Figure 1. Complex formed at pH 8 showing binding of minimization in molecular modelling studies. phosphates to the macrocycle (top) and the packing structure showing water channels (bottom).
[1] A. Bianchi, K. Bownman-James, and E. Garcia-Espana, Eds., Supramolecular Chemistry of Anions 1997,Wiley-VCH, New York. [2] C. Bazzicalupi, A. Bencini, A. Bianchi, M. Cheechi, B. Escuder, V. Fusi, E. Garcia- España, C. Giorgi, S. V. Luis, G. Maccagni, V. Marcelino, P. Paoletti and B. Valtancoli, J. Am. Chem. Soc., 1999, 121, 6807-6815.
IC-03 February 2-6, 2003 Melbourne 152 Microporous Coordination Polymers with 1,3,5-Benzenetricarboxylate: Effect of Ancillary Ligands and Solvent on Structure Colin L. Weeks, Cameron J. Kepert School of Chemistry, The University of Sydney, 2006, New South Wales, Australia [email protected] Coordination polymers consist of metal centres linked together by exo-multidentate organic ligands. The topology is determined by the structure of the bridging ligand(s), the number of metal centres each ligand connects, the number of bridging ligands around each metal, and the arrangement of the bridging ligands around the metal. Incorporation of ancillary (non-bridging) ligands into the coordination sphere of the metal can be used to control the topology of the coordination polymer. For example, in the coordination polymers Ni3(btc)2(py)6(alc)n.xalc.yH2O (btc = 1,3,5-benzenetricarboxylate, py = pyridine, alc = monodentate alcohol (n = 6) or bidentate diol (n = 3)) [1] the py and alcohol ligands occupy the equatorial sites of the octahedral Ni(II) coordination sphere, leaving the two axial sites for binding by the carboxylate groups of btc, hydrogen bonding between the alcohol protons and the non-coordinated oxygen of the carboxylate groups causes the planes of the btc ligands to be orthogonal, leading to the formation of homochiral (10,3)-a networks. The large voids in these networks lead to interpenetration, with the degree of interpenetration, either two-fold or four-fold, depending upon the identity of the alcohol ligands. We have used the tetradentate ligands bis(3-aminopropyl)-1,2-ethanediamine (3,2,3-tet) and bis(3-hydroxypropyl)-1,2-ethanediamine (bhpen) as ancillary ligands in the formation of coordination polymers with Ni(II) and btc. The coordination polymers were synthesised by slow diffusion of the reactants in methanol or ethanol and characterised by single-crystal X-ray diffraction and thermogravimetric analysis. In all the compounds the 3,2,3-tet or bhpen occupied the four equatorial coordination sites of the Ni(II) and the btc carboxylate groups were coordinated in the axial positions. The structure of the coordination polymers formed was dependent on the ancillary ligand and solvent used. A 2D layer was produced by 3,2,3-tet in methanol, it was a (6,3) net with honeycomb structure and was chiral due to helical channels running perpendicular to the layers (Figure 1). The use of ethanol instead of methanol with 3,2,3-tet lead to the formation of 1D chains, with only two of the three btc carboxylate groups involved in Ni coordination. When bhpen was used as the ancillary ligand 2D layers formed in both methanol and ethanol, these were (6,3) nets of the brick wall type.
Figure 1. Space filling representation of Ni3(btc)2(3,2,3-tet)3 formed in methanol (solvent omitted for clarity)
IC-03 February 2-6, 2003 Melbourne 153 Introducing the 4-Azapentalenyl Anion: a p-Bound Heterocyclic Anion with Potential Far Beyond the Cyclopentadienyl Anion!
Reiner Anwander,a F. Geoff N. Cloke,b Michael G. Gardiner,c Peter B. Hitchcock,b Lauren E. Wisec and Brian F. Yatesc. a Inst. Anorg. Chem., Tech. Uni. München, Litchenbergstr 4, 85747 Garching, Germany. b The Chemistry Laboratory, The University of Sussex, Brighton BN1 9QJ United Kingdom c School of Chemistry, University of Tasmnania, Private Bag 75, Hobart TAS 7001, Australia. [email protected] The pentalendiyl anion, 1, has provided a suitable multihaptic 2- - N ligand class over recent years which has been applied to the 1 2 study of novel transition metal complexes [1]. Via the -
incorporation of bulky substituents, in particular silylated N H N groups such as tri-i-propylsilyl, the anion has been successfully 3 H 4 used in the synthesis of f-element complexes, in particular thorium and uranium chemistry [2]. By exchanging one of the central carbons for nitrogen the system now bears a monoanionic charge, the pentadiendiyl system bears a dianionic charge. The heterocyclic monoanion thus occupies only one of the anionic coordination sites of the metal centre, thus providing the possibility to access “new look” metallocenes in bis(4- azapentalenyl) complexes. The 4-azapentalenyl system 2 is accessible via the deprotonation of the neutral parent heterocycle, 3H-pyrrolozine, 3 [3]. Investigations of this system to date are limited to the synthesis of Group one metal complexes, with characterisation limited to 1H NMR, and in 1998 the synthesis of a thallium complex was reported [4].
Here we report on the synthesis and structure determination of a M M number of potassium complexes of the benzoannelated 4- azapentalenyl derivative 4. The TMEDA adduct (shown above) N N is isostructural to the cyclopentadienyl analogue, while other 5 6 examples illustrate that a much larger range of binding modes is N possible. h8- (5), h5- (6) and cis-m -h5:h5- (7) binding modes 2 M M 7 have been shown to be feasible by DFT calculations. Attempts to prepare d- and f-block metal complexes will also be described.
[1] K. Jonas, P. Kolb, G. Kolbach, B. Gabor, R. Mynott, K. Angermund, O. Heinemann and C. Krüger, Angew. Chem., 1997, 109, 1793. [2] F.G.N. Cloke and P.B. Hitchcock, J. Am. Chem. Soc., 1997, 119, 7899. [3] W.H. Okamura and T.J. Katz, Tetrahedron, 1967, 23, 2941. [4] D.A. Kissounko, N.S. Kissounko, D.P. Krut’ko, G.P. Brusova, D.A. Lemenovskii and N. M. Boag, J. Organomet. Chem., 1998, 556, 145.
IC-03 February 2-6, 2003 Melbourne 154
Cationic Iridium and Rhodium Catalysts for the Synthesis of N-Heterocycles S. Burling,b L. D. Field,b B. A. Messerle,a S. Wrena a School of Chemical Sciences, The University of New South Wales, Sydney, 2052,NSW Australia. b School of Chemistry, University of Sydney, Sydney, 2006, NSW, Australia. [email protected] The synthesis of N-heterocycles, such as pyrrolines and pyrrolidines is an important synthetic goal due to their prevalence in biologically significant compounds. Organometallic catalysts can be used to achieve the synthesis of these heterocycles in a highly selective manner. Cationic + complexes of iridium(I) and rhodium(I) of the form [(NN)M(CO)2] (NN = bis- imidazolylmethane or bis-pyrazolylmethane) have H N N been found to be effective as catalysts for the 2 [M] H C 3 C synthesis of a number of pyrrolines via H C C hydroamination of alkynylamines (e.g. Scheme 1) [1]. Scheme 1 The catalytic efficiency of a new series of rhodium(I) and iridium(I) complexes for the synthesis of a pyrroline via hydroamination was tested. The catalysts investigated included isolated metal complexes, as well as metal complexes formed in situ from rhodium(I) and iridium(I) precursors with a series of alternate sp2-N-donor ligands, including diazabutadienes and imidazolyl-imines. The importance of co-ligands and counterions were also investigated. A direct comparison was made between the catalytic efficiency of isolated complexes and those generated in situ. Novel isolated iridium(I) and rhodium(I) catalysts with imidazolyl- imine ligands (e.g. 1) were synthesised. The complex {[Rh(p- +BPh4 tolylimino(1-methyl-2-imidazolylmethane))(CO)2][BPh4]} (1) was N CO found to be an effective catalyst for the hydroamination of 4-pentyn-1- Rh N CO amine to give 2-methylpyrroline. N 1
[1] a) S. Burling, L.D. Field, B.A. Messerle, Organometallics, 2000, 19, 87; b) S. Burling, Ph.D Thesis, 2001, The University of Sydney
IC-03 February 2-6, 2003 Melbourne 155 Membrane Copper Pump Ctr1 and Downstream Proteins Atx1 and Ccc2 in Yeast: Copper Binding and Trafficking
Zhiguang Xiao, Fionna Loughlin and Anthony G. Wedd School of Chemistry, University of Melbourne, 3010, Victoria, Australia [email protected] Copper is an essential but highly toxic element for all living cells. Thus copper uptake and trafficking must be regulated strictly [1]. In yeast, copper uptake is mediated by the plasma membrane copper pump Ctr1 (see Cox17 Cyt ox Figure) and delivered inside the cells to various copper-requiring mitochondrian Ctr Ccs compartments via different carrier SOD proteins (chaperones). Cu
Atxl is one of the cytosolic copper Ccc2 Atx1 chaperones and is required for Fet3 delivery of copper from Ctr1 to cell golgi apparatus Ccc2, a P-type ATPase pump membrane cy toso l incorporated in the membrane of the golgi apparatus. Both the C-terminus of Ctr1, Ctr1c, and the N-terminus of Ccc2 are located in the cytosol and are believed to interact with Atx1 directly.
We have expressed and purified Ctr1c, Atx1 and Ccc2n, the first N-terminal domain of Ccc2. Copper binding and exchanging [2] studies indicated: (1) both Ctr1c and Ccc2n can bind up to 4 Cu(I) ions whereas Atx1 can bind up to 2 Cu(I) ions; (2) Cu(I) exchanges rapidly between these proteins. The nature of the copper binding was studied by site-directed mutagenesis and by physical techniques such as EXAFS, CD, NMR, UV-Visible and analytical ultracentrifugation. Detailed results will be presented.
[1] S. Puig and D.J.Thiele. Current Opinion in Chemical Biology 2002, 6, 171-180.
[2] Z. Xiao and A.G.Wedd. J. Chem. Soc., Chem. Commun. 2002, 588-589.
IC-03 February 2-6, 2003 Melbourne 156
Product Diversity in the Reactions of Alkynes with Tp*W(dtc)(CO)2 Charles G. Young, Patrick J. Lim, Hassan Akhlaghi, Damian Slizys, Jonathan M. White
a School of Chemistry, University of Melbourne, 3010, Victoria, Australia
[email protected] The reactions of phenylacetylene, 2-butyne-1,4-diol and dimethylacetylene dicarboxylate – (DMAC) with Tp*W(dtc)(CO)2 (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate, dtc = S2CNEt2 ) in chlorinated solvents produce markedly different products. These are Tp*W(h1-dtc)(h2– 2 PhCºCPh)(CO) (1), Tp*WCl(h –HOCH2ºCCH2OH)(CO) (2) and the novel heterometallacycle, 2 Tp*W{S(dmac)CO}(h –SCNEt2) (3). All three products have been spectroscopically and structurally characterized. The structure of (3) shown below revealed dismemberment of the dtc ligand, forming a thiocarboxamide and new cyclic ligand from the coupling of sulfur (from dtc), alkyne (dmac) and carbonyl moieties. The carbonyl group is side on bonded to the W center. The syntheses, spectroscopic and structural properties of the complexes and their mechanism of formation will be addressed.
S N N
W N
C O S C
IC-03 February 2-6, 2003 Melbourne 157 Complexes of Divalent and Trivalent Ruthenium Incorporating Tethered Arenes
Joanne R. Adams,a Martin A. Bennetta and L. J. Yellowleesb. a Research School of Chemistry, Australian National University, Canberra ACT 0200, Australia. b Department of Chemistry, Joseph Black Building, West Mains Road, Edinburgh EH9 3JJ, United Kingdom. [email protected]
The tethered arene complexes 1-8, containing either two or three linking groups in the strap, have been synthesised from the labile methyl o-toluate complex [h6-(1,2- MeC6H4CO2Me)RuCl2]2 via mononuclear P-donor adducts which do not usually need to be isolated [1]. The complexes 1, 3, 5, 6, 7 and 8 have been structurally characterised by X-ray crystallography. Complexes 2, 4 and 7 have been reported independently [2]-[4]. The p-cymene 6 complex [h -(1,4-MeC6H4CHMe2)RuCl2]2 can only be used as a precursor to the tethered complexes if the phosphorus atom carries bulky substituents such as cyclohexyl; these reactions are slower than those starting from the ester complex.
R' R R SiMe2 Ru Ru Cl R' R Cl P Ru P Cl R Cl Cl Ph 2 Cl P 2 Ph2 1 R = Me 6 R = Me, R’ = H 8 2 R = Ph 7 R = R’ = Me 3 R = i-Pr 4 R = Cy 5 R = t-Bu
As arene-ruthenium(III) species are postulated to be involved as intermediates in catalytic C-H 6 bond activation processes based on [RuMe2(h -C6Me6)(PR3)] [5], the redox behaviour of complexes 1-8 and some non-tethered counterparts has been compared. Both series show reversible or quasi-reversible electrochemical behaviour. The resulting Ru(III) species were 6 detected by spectroelectrochemistry, and, in the cases of 3, 7 and [RuCl2(h -C6Me6)(PPh3)] (9), by esr. Chemical oxidation of 7 and 9 with [N(C6H4-Br-4)3]SbCl6 gave rise to the isolable, first + - + - structurally characterised arene-ruthenium(III) complexes [7] [SbCl6] and [9] [SbCl6] [6]. The tethered Ru(III) complexes, generated either by electrochemical or chemical oxidation, were more stable than their non-tethered counterparts.
[1] M. A. Bennett, A. J. Edwards, J. R. Harper, T. Khimyak and A. C. Willis, J. Organomet. Chem., 2001, 629, 7. (Joanne R. Harper is now Joanne R. Adams). [2] P. D. Smith and A. H. Wright, J. Organomet. Chem., 1998, 559, 141. [3] K. Y. Ghebreyessus and J. H. Nelson, Organometallics, 2000, 19, 3387. [4] A. Fürstner, M. Liebel, C. W. Lehmann, M. Picquet, R. Kunz, C. Bruneau, D. Touchard and P. H. Dixneuf, Chem. Eur. J., 2000, 6, 1847. [5] A. Ceccanti, P. Diversi, G. Ingrosso, F. Laschi, A. Lucherini, S. Magagna and P. Zanello, J. Organomet. Chem., 1996, 526, 251. 6 [6] [RuCl3(h -C6Me6)] has been isolated but was not structurally characterised; U. Kölle, R. Görissen and A. Hörnig, Inorg. Chim. Acta, 1994, 218, 33.
IC-03 February 2-6, 2003 Melbourne 158 Stereochemical Effects on Intervalence Charge Transfer in Polymetallic Supramolecular Assemblies
Deanna M. D'Alessandro and F. Richard Keene School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Queensland 4811, Australia
Ruthenium(II) and osmium(II) polypyridyl complexes have been the subject of extensive recent multidisciplinary research efforts, motivated largely by the potential of "polymetallic supramolecular assemblies" derived from them in photo-activated molecular devices. Dinuclear ligand-bridged mixed-valent complexes have received considerable attention in this context, as the intervalence charge transfer (IT) absorption generated in such species provides a powerful and sensitive probe of inter-metal electron transfer processes. However, the influence of the inherent stereochemistry of these species on intramolecular electron transfer has not been addressed [1].
The present studies have revealed differences between the IT characteristics of the meso and racemic diastereoisomers of a range of ligand-bridged 5+ dinuclear systems such as [{Ru(bpy)2}2(m-dpo)] (a) {bpy = 2,2’-bipyridine; dpo = 3,4-di(2-pyridyl)-1,2,5- oxadiazole} (Figure 1) [2,3]. The access to subtle variations in redox asymmetry between the stereoisomers has permitted a new and intimate probe of reorganisational effects on intramolecular electron transfer due to solvent and anion association. (b) Previously, such contributions had been exclusively Figure 1. X-ray crystal structure of meso- 4+ studied by the variation of more global features such [{Ru(bpy)2}2(m-dpo)] (a), and the IT bands observed in the near-IR for the as the identity and coordination environments of the meso and racemic diastereoisomers of the participating metal centres. mixed-valent [5+] species (b).
The presentation will detail the first observation of stereochemical effects on the IT process in di- and tri-nuclear ligand-bridged complexes, utilising a combination of electrochemical, computational, theoretical and spectroelectrochemical studies of solvato- and thermo-chromism. The new insights they provide into the factors which influence the barriers to intramolecular electron transfer will also be discussed. ______[1] F.R. Keene, Coord. Chem. Rev., 1997, 166, 121-159; F.R. Keene, Chem. Soc. Rev., 1998, 27, 185-193. [2] D.M. D'Alessandro, L.S. Kelso and F.R. Keene, Inorg. Chem., 2001, 40, 6841-6844. [3] C. Richardson, P.J. Steel, D.M. D'Alessandro, P.C. Junk and F.R. Keene, J. Chem. Soc., Dalton Trans., 2002, 2775-2785.
IC-03 February 2-6, 2003 Melbourne 159 Guest-Dependent Spin Crossover in Nanoporous Molecular Framework Materials Gregory J. Halder,a Cameron J. Kepert,a Boujemaa Moubaraki,b Keith S. Murrayb and John D. Cashionc a School of Chemistry, University of Sydney, 2006, New South Wales, Australia b School of Chemistry, Monash University, 3800, Victoria, Australia c School of Physics and Materials Engineering, Monash University, 3800, Victoria, Australia [email protected] There is currently a major international push toward the design, synthesis and characterisation of molecular materials with applications in important areas such as information processing, memory devices, data storage and retrieval, and magnetic and optical switches. The spin- crossover centre offers a type of molecular switch that exists in two different electronic states that have marked differences in geometry, magnetism and colour. The incorporation of both nanoporosity and electronic switching into such materials is unique in allowing detailed in-situ studies of the steric and electronic influences of adsorbed guests on the spin-crossover centres.
Structural and magnetic characterisation of the robust nanoporous spin-crossover framework II Fe (azpy)2(NCS)2.½(guest) (azpy = 4,4?-azopyridine) (1) has recently been completed. The structural refinement revealed doubly interpenetrating iron(II)-azpy rhombic-grids(A). Modified single crystal X-ray diffraction measurements [1] of both the ethanol loaded and fully desolvated forms have enabled a thorough investigation into the structural consequences of desolvation.
Through related magnetic studies of 1 a guest-dependent ‘half’ spin-crossover has been observed [2]. A high-spin to low-spin transition between 150 K and 50 K was observed for one of the two crystallographically distinct iron(II) centres in the solvated framework, while no transition was observed after desolvation of the framework (B). [1] C.J. Kepert, M.J. Rosseinsky, Chem. Commun. 1999, 375. [2] G.J. Halder, C.J. Kepert, B. Moubaraki, K.S. Murray, J.D. Cashion, Science, 2002, 298, 1762.
IC-03 February 2-6, 2003 Melbourne 160 Fundamental studies of solar energy materials: vibrational spectroscopy and ab initio studies of 1,10-phenanthroline and its complexes. Sarah Howell,a Keith Gordona a Chemistry Department, University of Otago, Dunedin, New Zealand
[email protected] Polypyridyl complexes, such as those containing 1,10-phenanthroline (phen) (Fig 1), are widely used in areas such as solar cell devices.[1] An important feature of these complexes is the metal- to-ligand charge transfer (MLCT) that occurs upon excitation.[2] Structural changes that occur to the complex have implications to the excited state lifetime. Techniques which study these transient species and allow its species to be determined may allow the time-efficient screening of materials for use in devices such as solar cells. 2- D D D D N N D D N Ru N N N N N N N D D phen d8-phen 2- [Ru(CN)4(phen)]
Figure 1. Molecular structure of 1,10 phenanthroline (phen), the deuterated analogue (d8-phen) and the ruthenium 2- complex [Ru(CN)4(phen)] .
Ab initio calculations were used to calculate the structure of phen. From this the corresponding vibrational spectra were calculated. These were then compared to measured spectra. If the calculated and measured spectra match it can be assumed that the calculated structure is a good
representation of the real structure. The perdeuterated analogue, d8-phen was also examined to aid spectral interpretation. This procedure was repeated for the radical anion of the ligands. This is a good model for the MLCT excited state. Spectra of polypyridyl radicals can be difficult to 2- collect so time-resolved resonance Raman spectroscopy of [Ru(CN)4(phen)] was employed to provide a spectral signature of the radical anion. A good spectral match between calculated and experimental data would indicate that the calculated structure was similar to the real structure of phen.-. The structural change upon reduction can be established which has implications for the amount of structural change that occurs upon a metal-to-ligand charge transfer.
[1] For example: B. O’Regan, M. Grätzel, Nature, 1991, 353 737. [2] K. Kalyanasundaram, Modern Molecular Photochemistry, Benjamin/Cummings Publishing Company, Inc., California, 1992.
IC-03 February 2-6, 2003 Melbourne 161 The Synthesis and Study of Metal Complexes of Ligands with Tripodal Tridentate Binding Domains Christopher J. Sumby and Peter J. Steel Department of Chemistry, University of Canterbury, Christchurch, New Zealand [email protected] The programmed self-assembly of metallosupramolecular aggregates constructed from multitopic bridging ligands and transition metal centres is in a continual process of development. The armoury of the chemist has been constantly expanding with the synthesis of new multitopic bridging ligands with varied topologies. We have focussed recently on the synthesis of bridging heterocyclic ligands that posses tripodal tridentate binding domains. These ligands are constructed about isomeric diazines, to which are appended di-2-pyridylamine or di-2- pyridylmethane constructs. Two example of this class of ligand are 4,6-bis(di-2- pyridylamino)pyrimidine (1) and 3,6-bis(di-2-pyridylmethyl)pyridazine (2) (Figure 1).
H H N N N N N N N N N N N N N N
(1) (2) Figure 1. Two examples of bridging ligands with tripodal tridentate coordination. These, and related ligands, have been reacted with a range of metal salts to investigate their coordination complexes. With a range of metal precursors we have observed several common structures in the complexes of these ligands, including side-by-side [2+2] metal-ligand dimers and dinuclear helicates [1]. Comparisons between ligands bearing nitrogen and carbon linker atoms showed that the nitrogen linker is more planar thereby preventing those ligands from facially coordinating to metal atoms [2]. [1] C. J. Sumby and P. J. Steel, Inorg. Chem. Comm. 2002, in press. [2] C. J. Sumby and P. J. Steel, unpublished results, 2002.
IC-03 February 2-6, 2003 Melbourne 162 Catalytic Gas Phase Oxidation of Methanol to Formaldehyde
Tom Waters, Richard A. J. O’Hair, Anthony G. Wedd
School of Chemistry, University of Melbourne, 3010, Victoria, Australia
2- Electrospray Ionisation allows quaternary ammonium salts of the dimolybdate anion [Mo2O7] 2- to be transferred to the gas phase. The major ions observed are the dianion [Mo2O7] , protonated - + 2- - dimolybdate [Mo2O6(OH)] , and the ion pair {Bu4N [Mo2O7] } . A quadrupole ion trap mass spectrometer allows each of these ions to be trapped and their gas phase chemistry towards - neutral reagents to be explored. The protonated dimolybdate anion [Mo2O6(OH)] catalyses the gas phase oxidation of methanol to formaldehyde (Fig. 1):
CH3OH + CH3NO2 ® H2CO + H2O + CH3NO
The elementary steps of this catalysis have been investigated by variation of substrate alcohol (structure and isotope labelling) and by kinetic measurements. The role of the binuclear dimolybdate centre has been examined by variation of the metal (e.g Cr, Mo, W) and nuclearity (e.g mononuclear, binuclear) of the catalytic species.
The three reactions of this gas phase catalysis are equivalent to the three essential steps proposed to occur in the industrial oxidation of gaseous methanol to formaldehyde over molybdenum(VI)- trioxide solid state catalysts. A detailed molecular understanding of the mechanisms of this important industrial process seems elusive. Similarities between the present gas phase catalysis and the industrial process suggest the present study may shed light on important reactions and intermediates involved in the industrial process.
Figure 1: Gas phase catalytic cycle for the oxidation of methanol to formaldehyde
IC-03 February 2-6, 2003 Melbourne 163 Platinum Anticancer Agents. Structures and Targeted Biomolecules N. Farrell, Department of Chemistry, Virginia Commonwealth University [email protected]
In this lecture I will present work from our laboratory on the chemistry and biology of novel platinum anti-cancer agents differing in structure and modes of DNA-binding from the clinically used cisplatin (cis-[PtCl2(NH3)2], cis-DDP). The seminar will explore how structurally novel compounds may, by formation of different types of Pt-DNA adducts, lead to different cellular signalling or “downstream” effects such as gene expression and protein recognition and whether such events may be dictated to lead to a genuinely unique pattern of anticancer activity. BBR3464, the first platinum-based drug outside the cisplatin family to reach clinical trials, has originated from this approach. Two sets of compounds - (i) polynuclear compounds comprising two or more platinum coordination units linked in a linear fashion and (ii) mononuclear trans-platinum compounds containing planar heterocyclic amines will be discussed. The seminar will also summarize current developing work on how platinum (and other metal)-based agents can be designed toward specific biomolecules, adapting the chemistry and biology of coordination compounds to biotechnology and the new paradigm of targeted approaches in drug discovery.
IC-03 February 2-6, 2003 Melbourne 164 First Structurally Characterised Complexes of a Triazolate-Containing Schiff-Base Macrocycle: Syntheses and Properties Udo Beckmann,a Sally Brooker,*a Craig V. Depree,a Janna D. Ewing,a Boujemaa Moubarakib and Keith S. Murrayb a Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand b School of Chemistry, Monash University, PO Box 23, Clayton, Victoria 3800, Australia [email protected] The Schiff-base macrocycle obtained from the [2+2] condensation of 3,6-diformylpyridazine [1] N and 1,3-diaminopropane has facilitated the isola- N N tion of a wide range of transition metal com- N N plexes with intriguing properties, in particular redox and magnetic properties [2]. Given the N N N N considerable current interest in utilising substituted N 1,2,4-triazoles as ligands for transition metal ions
[3], for example in efforts to develop new mag- Figure 1. The new macrocyclic ligand L2-. netic materials [4], we decided to incorporate this moiety into Schiff-base macrocycles. We obtained the novel Schiff-base macrocycle L2- (Fig. 1) as its di-lead(II) complex by [2+2] condensation of 3,5-diacetyl-1H-1,2,4-triazole and 1,4-diaminobutane in presence of a base using lead(II) ions as templates.
Transmetallation of the macrocyclic lead complex in acetonitrile with
CoCl2 · 6 H2O leads to the orange, six-coordinate complex di-cation II 2+ [Co 2 (L) (OH2)3 (NCCH3)] (Fig. 2). Subsequent reaction with NaOCN or
NEt4Cl yielded red-purple five- II coordinate [Co 2 (L) (NCO)2] or red II five-coordinate [Co 2 (L) (Cl)2], re-
II 2+ spectively. All the macrocycles con- Figure 2. The complex cation [Co 2 (L) (OH2)3 (NCCH3)] . tain two high-spin cobalt(II) centers which are weakly antiferromagnetically coupled. All cobalt complexes have been characterised by X-ray diffraction and are the first structurally characterised complexes of a triazolate- containing Schiff-base macrocycle so far.
[1] S. Brooker, R. J. Kelly, J. Chem. Soc., Dalton Trans., 1996, 10, 2117.
[2] S. Brooker, P. G. Plieger, B. Moubaraki, K. S. Murray, Angew. Chem. Int. Ed. Engl., 1999, 38, 408.
[3] J. G. Haasnoot, Coord. Chem. Rev., 2000, 200-202, 131.
[4] O. Kahn, Chem. Br., 1999, 2, 24.
IC-03 February 2-6, 2003 Melbourne 165 Structural Diversity Exhibited by Lanthanide Carboxylates T. Behrsing,a G. B. Deacon,a C. M. Forsyth,a and M. Forsyth,b M. Hilder,a B. W. Skelton c and A. H. White c a School of Chemistry and b School of Physics and Materials Engineering, Centre for Green Chemistry, Monash University, Vic., 3800, Australia and c Chemistry, University of Western Australia, Crawley, 6009 [email protected] Lanthanide carboxylates usually show limited structural diversity (e.g. complexes with the methoxy benzoate ligand). By contrast, the salicylate ligand shows a greater variety of coordination modes. Polymeric and dimeric structures are published in the literature for a few ‘heavy’ (Tb-Lu) lanthanide salicylates [1-3]. Recent work has revealed a third previously unreported monomeric structure (for Gd – Yb), which highlights the structural diversity exhibited by this ligand with the lanthanide elements. In addition, two novel examples of a mixed salicylate/acetate ligand system are given. X-ray structural determinations are presented for each geometric type and interesting features highlighted.
Figure 1. The unit cell of the novel monomeric [Gd(salH)3(H2O)4].2H2O, in which three salicylate ligands chelate the lanthanide ion.
[1] Ma Jianfang, Jin Zhongsheng and Ni Jiazuan, Chinese J. Inorg. Chem, 1993, 9, 160. [2] Ma Jianfang, Jin Zhongsheng and Ni Jiazuan, Acta Crystallogr. Sect. C., 1994, C50, 1010. [3] J. P. Costes, F. Dahan, J. M. Clemente-Juan and M. Verelst, Angew. Chem. Int Ed. 2002, 41, 323.
IC-03 February 2-6, 2003 Melbourne 166
Synthesis of Bis(1,3-bis(di-2-pyridylphosphino)propane)Gold(I) Chloride: Potential Anti-Tumour Agent Anthony S. Humphreys,a Susan J. Berners-Price,a George A. Koutsantonis,a Brian W. Skeltona and Allan H. Whitea a Chemistry, School of Biomedical and Chemical Sciences, University of Western Australia, Perth, WA, 6009, Australia [email protected] The 1:2 adducts of Au(I) with 1,2-bis(di-n-pyridylphosphino)ethane (dnpype) for n=2, 3 and 4 are hydrophilic analogs of the lipophilic cationic Au(I) antitumour compound [Au(dppe)2]+ (1). Clinical development of 1 was abandoned due to severe hepatotoxicity in dogs attributed to the high lipophilicity. For the pyridylphosphine analogs the position of the N atom in the pyridyl ring finely modulates the lipophilic-hydrophilic balance and these differences in lipophilicity influence the cellular uptake, tumour selectivity and host toxicity [1]. Although the mode of action is unknown an antimitochondrial mechanism is likely and it may be possible to utilise known differences in mitochondrial membrane potential to selectively target tumour cells with compounds with optimal lipophilic-hydrophilic character. To further explore this possibility a wider range of analogous compounds with differing lipophilicities are needed.
This work involves the synthesis of 3-carbon bridge analogs of the dnpype ligands. The synthesis of the precursor Cl2P(CH2)3PCl2 [2] has been optimised by the use of bis(trichloromethyl) carbonate as the chlorinating agent and the ligand 1,3-bis(di-2- pyridylphosphino)propane (d2pypp) and its hydrochloride salt have been synthesised and characterised by multinuclear NMR spectroscopy. The phosphine is extremely sensitive to oxidation and difficult to purify whereas the hydrochloride salt recrystallises readily and is stable in oxygenated solvents for over 2 months. The d2pypp ligand has six possible (N and P) protonation sites and potentiometric titration revealed four mol equivalents of chloride per mol of ligand. The 1:2 and 2:1 Au(I) d2pypp adducts have been synthesised, their solution properties characterised by multinuclear NMR spectroscopy and solid state structures determined by x-ray crystallography. [Au(d2pypp)2]Cl has a monomeric structure in both solution and the solid state whereas the analagous 1:2 Au(1): dnpype adduct exists as a dimer in the solid state and an equilibrium mixture in solution [3].
[1] M. J. McKeage, S. J. Berners-Price, P. Galettis, R. J. Bowen, W. Brouwer, L. Ding, L. Zhuang and B. C. Baguley, Cancer Chemother. Pharmacol., 2000, 46, 343. [2] E. Lindner, M. Schmid, J. Wald, J. A. Queisser, M. Geprägs, P. Wegner and C. Nachtigal, J. Organomet. Chem., 2000, 602, 173.
[3] S. J. Berners-Price, R. J. Bowen, T. W. Hambley and P. C. Healy, J. Chem. Soc. Dalton Trans., 1999, 8, 1337.
IC-03 February 2-6, 2003 Melbourne 167 Reversible Nitrogen Sorption into the Nanoporous Molecular Framework [Co(4,4?-bipyridine)1.5(NO3)2] by Single Crystal X-ray Diffraction Joseph J. Bevitt, Gregory J. Halder and Cameron J. Kepert School of Chemistry, University of Sydney, 2006, New South Wales, Australia [email protected] Zeolites exhibit extraordinary chemistry through their selectivity and finely tuned acid-base properties. Unfortunately, many catalytic and separative processes cannot be achieved within a purely inorganic framework. To overcome this, post-synthetic tethering of organic components to a zeolitic backbone has been used to impart organic functionality to the framework. Recently another class of materials, the nanoporous metal-organic frameworks (MOFs), have been designed that incorporate this organic functionality directly into the framework. If these materials can be shown to exhibit true nanoporosity, they will pave the way for an infinite class of highly specialised ‘sieves’ capable of separating or catalysing reactions based on organic complementarity.
Single crystal temperature dependent X-ray diffraction experiments have demonstrated that
[Co(4,4?-bipyridine)1.5(NO3)2][1] (A) is the first definitive example of a truly nanoporous MOF. That is, A has been shown to undergo reversible guest exchange of simple solvent vapours without loss of crystallinity or pore collapse.
By first heating, then cooling a crystal of A?(EtOH) under a nitrogen cryostream (Figure 1), the vacant framework A is achieved and gaseous nitrogen is sorbed into the MOF. Unit cell analyses, with full structural data for a range of temperatures and temperature ramp rates reveal for the first time, the presence and percentage occupancy of gaseous nitrogen within a porous material, confirming the analogy with zeolites suggested by sorption and powder diffraction measurements[1].
Single crystal heated in an open-ended capillary
Desorbed crystal exposed to sorptive vapour Desorbed crystal exposed to nitrogen gas
Figure 1: The experimental cycle used to analyse the reversible vapour and gas sorption of A.
[1] C. J. Kepert and M. J. Rosseinsky, Chem. Commun., 1999, 375-376
IC-03 February 2-6, 2003 Melbourne 168 XAFS Analysis of Transiently Stable Electrogenerated Products Mark I. Bondin,a Garry Foran,b and Stephen P. Besta a School of Chemistry, University of Melbourne, 3010, Victoria, Australia b Australian Nuclear Science and Technology Organisation (ANSTO), PMB 1 Menai, 234, NSW, Australia. [email protected] XAFS potentially provides an important path to the acquisition of structural information from transiently stable electrogenerated species and on this basis provides and ideal adjunct to spectroelectrochemical (SEC) investigations. The application of this approach is described with reference to the chemistry of Fe2S2(CO)6, 1, a well-documented compound that is known to undergo redox initiated dimerisation reactions. The electrochemistry of 1 is marked by 2- 2- intermolecular structural change with the formation of a dianionic dimer, [Fe4S4(CO)12] (D ), following an overall one electron reduction, where it has been proposed that further reduction results in a second irreversible step leading to formation of 12-. Both the structures of 1 and D2- are known, however the structural and spectroscopic properties of 12- are poorly defined.
Solutions suitable for XAFS analysis were obtained 8 using a purpose-built continuous flow 6
4 electrosynthesis cell, which allowed on-line
2 spectroscopic monitoring (UV-Vis) of the solution )) k ( c
3 0 k flowing trough the XAFS cell [1]. Once the sample XAFS ( -2 was in the required redox state, the XAFS cell was -4 rapidly frozen (80 K) prior to XAFS data collection. -6 2- -8 The Fe-K edge XAFS of solid samples of 1 and D
0 2 4 6 8 10 12 14 -1 provide a basis for the differentiation between the Photoelectron momentum k (Å ) Figure 1 XAFS of solid samples of 1 monomer and the dimer structural forms (Fig. 1). 2- (red) and D (blue). The solution XAFS for 1 and electrochemically generated D2- are consistent with their adoption of monomeric and dimeric structures, respectively, in accordance with structural and spectroscopic results. The XAFS of the low temperature reduction product of D2- shows oscillations which closely match those obtained for the dimeric structure. Furthermore, the modelling of the XAFS of D2- within a multiple scattering formalism gives structural details of a similar quality to those obtained for 1 and D2-. The earlier report of the XAFS of 12- generated by superhydride reduction at room temperature [2] is considered in light of this analysis.
These experiments provide a useful entry point for XAFS studies of redox-initiated structural change of {2Fe2S} compounds, in particular the dithiolate-bridged diiron model complexes of the hydrogenase H-cluster, {2Fe2S}H.
[1] M.I. Bondin, G. Foran and S.P. Best, Aust. J. Chem. 2002, 54, 705-9.
[2] T.D. Weatherill, T.B. Rauchfuss, R.A. Scott, Inorg. Chem. 1986, 25, 1466-72.
IC-03 February 2-6, 2003 Melbourne 169 Molecular Rectangles from Metallomacrocycles Paula L. Caradoc-Davies and Lyall R. Hanton Chemistry Department, University of Otago, PO Box 56, Dunedin, New Zealand [email protected]
Current interest in discrete polyhedra and polygons, such as the formation of tetrahedral cages, squares and rectangles, has stemmed from their many potential applications including molecular recognition and separation. In particular, molecular rectangles, as lower symmetry hosts, are expected to show enhanced binding and selectivity over symmetric molecular squares for certain types of hosts.1 However, the synthesis of molecular rectangles using metal precursors complexed to two different ligands simultaneously is not a trivial task. Metallomacrocycles offer an intermediate option in that they can provide rectangular shapes without the need for the combination of mixed ligands.
We initially designed ligand 1 to act as a metallomacrocycle edge, with additional functionality incorporated for the formation of extended supramolecular arrays (Fig 1.). When 1 was complexed with Ag(I) and Cu(II) salts rectangular metallomacrocycles resulted. Unfortunately there were no cavities available for guest incorporation. A new extended ligand, 2, was designed to allow formation of larger metallomacrocycles with cavities capable of guest incorporation (Fig. 1). Ligand 2 was complexed with CuI to successfully give a rectangular metallomacrocycle (Fig. 2). The metallomacrocycle formed a three-dimensional honeycomb array with channels containing CH3CN molecules.
Figure 1. Ligands 1 and 2 designed O S S O for metallomacrocycle formation S S
N N N N
1 2
Figure 2. Rectangular metallomacrocyclic complex, [Cu2I2(2)]2?2CH3CN, showing the cavity which contains two CH3CN solvent molecules
[1] T. Rajendran, B. Manimaran, F.–Y. Lee, G.–H. Lee, S.–M. Peng, C. M. Wang and K.–L. Lu, Inorg. Chem., 2000, 39, 2016; K. D. Benkstein, J. T. Hupp and C. L. Stern, Angew. Chem. Int. Ed., 2000, 39, 2891.
IC-03 February 2-6, 2003 Melbourne 170 Anomalous Thermal Expansion Behaviour in Coordination Framework Materials Karena W. Chapman,a Andrew L. Goodwin a and Cameron J. Keperta a School of Chemistry, University of Sydney, 2006, NSW, Australia [email protected] The current interest in coordination framework materials derives from the wide range of possible functionalities that can be achieved and the exciting potential to tailor these properties towards specific applications through systematic variation of metal ion, ligand and included guest species. Reported functionalities have included those of a photochemical, mechanical, optical, electronic and magnetic nature, allowing applications in selective sorption, catalysis, sensing, switching and data storage.
We have synthesised and characterised a broad class of coordination frameworks displaying anomalous thermal expansion behaviour, including both negative thermal expansion (NTE) and zero thermal expansion (ZTE). These have diverse potential applications ranging from optical componentry, computer componentry and low-thermal shock materials where the positive thermal expansion exhibited by the vast majority of materials could be a hindrance.
Using a variety of diffraction techniques it has been established that this class of materials show the most pronounced NTE reported to date, with coefficient of thermal expansions up to –21 x 10-6 K-1, more than twice that of the previous record held by zirconium tungstate.
Figure 1. The reduction in unit cell volume upon heating.
IC-03 February 2-6, 2003 Melbourne 171 Lanthanoid Complexes with 'Non-Coordinating' Anions – From Discrete Ions to Molecular Complexes Glen B. Deacon, David J. Evans, Craig M. Forsyth and Peter C. Junk School of Chemistry, Monash University, 3800, Victoria, Australia
[email protected] Sterically demanding anions having a diffuse negative charge and being devoid of - electronegative donor atoms (e.g. BPh4 ) are not expected to participate in strong associations with the highly electropositive lanthanoid metal cations, and are typically considered as 'non- coordinating'. Indeed, discrete lanthanocene(III) cations are well established through this strategy, and only rarely has residual cation-anion bonding been observed.[1] We have investigated replacement of typical (excluding cyclopentadienyl) anionic ligands for lanthanoid - - - complexes (e.g. NR2 , OR , R) with these so-called 'non-coordinating' anions and show that the extremes of ion dissociation/association are possible.
N Me3Si
O O N 2+ O Yb Me3Si Yb O B O O O
N
[1] Evans, W. J.; Seibel, C. A; Ziller, J. W. J. Am. Chem. Soc. 1998, 120, 6475 – 6752; Schaverien, C. J. Organometallics 1992, 11, 3476 - 3478
IC-03 February 2-6, 2003 Melbourne 172 Solvent Extraction of Metal Ions Using Supramolecular Assemblies V. Gasperov,a L. F. Lindoy,a K. Gloe,b K. Wichmann,b M. Mahinay,c P. A. Tasker,d a Centre for Heavy Metals Research, School of Chemistry, University of Sydney, 2006, Sydney, Australia b Institute of Inorganic Chemistry, TU Dresden, D-01062 Dresden, Germany c James Cook University, Townsville, Australia, 4811 d Department of Chemistry, University of Edinburgh, Edinburgh, UK, EH9 3JJ [email protected]
The present study is concerned with (i) an investigation of host-guest formation between species which are themselves potential metal-ion ligands and (ii) the implications of such supramolecular assembly for metal ion binding. Selected molecular assemblies consisting of mixed-donor, amine-containing macrocyclic hosts and lipophilic organic acids were used in solvent extraction experiments aimed at documenting the effect of such “assemblies” on metal ion binding. It is hypothesised that the tendency for a host-guest assembly of this type to form in equilibrium with its corresponding metal complex may represent one process leading to synergistic extraction.[1]
R R
- COO COO-
RN 2 RCOOH + 2+ RN X R N X M (w) X H H M + + X NR X N R 2 H (w) X NR
- COO COO-
R R
Figure 1: General scheme for metal extraction using amine-containing macrocycles and lipophilic carboxylic acids.
NMR titrations studies, x-ray structure determination and molecular modelling calculations have all been used to probe further the nature of the interaction between the individual hosts and guests. The assembly concept has the potential to systematise previously reported metal-ion extraction behaviour as well as provide a basis for the design of improved metal-uptake systems in the future.
[1] K. R. Adam, I. M. Atkinson, S. Farquhar, A. H. Leong, L. F. Lindoy, M. S. Mahinay, P. A. Tasker, D. Thorp, Pure Appl. Chem. 1998, 70, 2345.
IC-03 February 2-6, 2003 Melbourne 173 Solid State Optophysical and Structural Properties of Lanthanoid Carboxylates Glen B. Deacon,a Ken Ghigginob, Matthias Hilder,a Peter C. Junka and Ulrich H. Kynastc a School of Chemistry, Monash University, Clayton, 3800, Victoria, Australia b School of Chemistry, University of Melbourne, 3010, Victoria, Australia c Department of Chemistry, Fachhochschule Münster, 48565 Steinfurt, Germany
Due to their unique optoelectronic properties lanthanoids are popular luminescent active centres utilised in all kinds of different phosphors. Therefore they are widely used in various luminescent applications such as lightning systems, cathode ray tubes, fluoro-immuno assays, sensors, decoration purposes as well as electrochemical devices (LED’s). In general they can be used in every area where energy rich Uv light is converted into visible light of lower energy. For quantum mechanical reasons lanthanoids can not be excited directly by light. However, by attaching strongly absorbing organic ligands to the lanthanoid it can be excited indirectly from the high energy triplet state of the ligand [1]. The commonly accepted electronic pathway is given in the picture below. Benzoic acid derivatives are strong UV absorbers and their deprotonated benzoate anion forms very stable complexes with the highly oxyphilic lanthanoid cations. These promising class of ligands therefore fulfil all chemical as well as electronic requirements for highly efficient luminescent materials. Europium and terbium ions provide suitable energy levels for luminescence in the visible region of the electromagnetic spectrum. The data obtained by performing a systematic study on a great variety of differently substituted lanthanoid benzoate complexes in the solid state under defined measuring conditions provide fundamental as well as comparable data which make qualitative and statements possible. These studies are independent neither on solvent or matrix effects nor on instrumentation or measuring parameters. The poster presents the photophysical properties (reflexion, excitation, emission) of some chosen complexes together with their chemical composition based on results obtained by volumetric, spectroscopic and X-Ray diffraction determinations as well as synthetical aspects.
1 inter system crossing S1 energy transfer 3 excitation T Ln*
luminescence
1 S0 Ln E Figure 1 Electronic Pathway
[1] M. Guardigli and I. Manet, Handbook on the Physics and Chemistry of Rare Earths (Editors: K.A. Gschneider and L. Eyring), 1996, 23, p.69 - 119.
IC-03 February 2-6, 2003 Melbourne 174 New Linkers for Bis-porphyrins Designed to Host Fullerenes Ali Hosseini, Peter D. W. Boyd, Steven M. F. Kennedy Department of Chemistry, University of Auckland, 3010, , New Zealand [email protected]
Supramolecular attraction of fullerenes such as C60 and C70 to porphyrins is of particular use in the formation of donor (porphyrin)-acceptor (fullerene) assemblies. Such host-guest complexes can exhibit photoinduced charge separation (porphyrin to C60), which is a requirement for photovoltaic devices and in photosynthesis.[1]
A range of new covalently linked acyclic bis-porphyrins designed for supramolecular binding of fullerenes will be presented. The linker has been chosen so that the arrangement of the porphyrins in the porphyrin-fullerene host-guest complex is similar to the observed arrangement in the crystal structures of cocrystallates of single porphyrin and fullerene molecules.[2]
The synthesis and characterisation of bis-porphyrins with two types of linkers will be presented. Firstly, calix[4]arene linkers which have the porphyrins appended at trans-26,27 OH position on the lower rim as shown in figure 1a. Secondly, isophthalic acid (figure 1b) and pyridin-2,6- dicarboxylic acid (figure 1c) linked porphyrins.
O R O R N N
N
N N HO O O O R O R R HO R (a) (b) (c)
R = porphyrin
Figure 1
The supramolecular binding constant (K) measurements of C60 and C70 guests for the bis- porphyrin hosts, as determined by fluorescence spectroscopy, will be discussed.
[1] R. N. Lyubovskaya, D. V. Konarev, I. S. Neretin, Y. L.Slovohotov, E. I. Yudanova, N. V. Drichko, Y, M. Shul’ga, B. P. TL. L. Gumanov, and A. S. Batsanov, J. A. K. Howard, Chem. Eur. J., 2001, 7, No 12, 2605-2616. [2] P. D. W. Boyd, M. C. Hudgson, C. E. F. Rickard, A. G. Oliver, L Chacker, P. J. Brothers, R. D. Bolskar, F. S. Tham, and C. A. Reed, J. Am. Chem. Soc., 1999, 121, 10487
IC-03 February 2-6, 2003 Melbourne 175 Cubane-related building blocks from the decomposition of ene-diols
Tim Hudson, Brendan F. Abrahams, and Richard Robson School of Chemistry, University of Melbourne, 3010, Victoria, Australia
While dihydroxyfumaric acid and pyridoin have been studied extensively in organic chemistry, their use as bridging ligands to construct coordination polymers have to date been limited. This can be attributed mainly to their tendency decompose in the presence of metal ions under basic conditions. Our attempts to utilise these ligands as building blocks for coordination polymers has led to new polynuclear complexes and networks resulting from this decomposition.
We have found that dihydroxyfumaric acid in the presence of Zn(OAc)2 in aqueous solution 4- decomposes through a benzylic acid type rearrangement to yield tricarboxy methoxide (C4O7 ) as a coordinated anion in a tetrahedral polynuclear complex of formula Zn8(C4O7)4(H2O)12.
Lying at the centre of this complex is a Zn4O4 cubane-related core. Similar structures have been obtained with Co(II) and Mg(II).
Under different conditions, a coordination polymer with the (10,3)a topology is formed which contains both tricarboxy methoxide anion and its decarboxylation derivative, hydroxymalonate 3 (C3HO5 ). This network also has cubane-related units as building blocks.
OH O OH HO OH
OH O OH Dihydroxyfumaric acid Pyridoin
IC-03 February 2-6, 2003 Melbourne 176
ROBUST POROSITY & FERRIMAGNETISM IN A PILLARED-LAYERED MATERIAL
Suzanne Hughes1, Cameron Kepert1, Mohamedally Kurmoo2, Hitoshi Kumagai2 1School of Chemistry, The University of Sydney, NSW 2006 Australia. 2Institut de Physique et Chimie des Materiaux de Strasbourg, Strasbourg Cedex France
The synthesis, characterization and reversible guest-exchange chemistry of a new porous magnetic material that orders ferrimagnetically at 60.5 K is described. The material,
Co5(OH)8(chdc)·4H2O (chdc = trans-1,4-cyclohexanedicarboxylate) consists of Co(II)-hydroxide (oct) (tet) layers of composition Co 3Co 2(OH)8 that are linked together by bis(unidentate) chdc pillars. Non-coordinated water molecules occupy 1-D channels situated between the chdc pillars. The
material remains monocrystalline during thermal dehydration from Co5(OH)8(chdc)·4H2O to
Co5(OH)8(chdc). The single crystal structure of the fully dehydrated material has no void volume due to a tilting and rotation of the pillars and 9% decrease of the interlayer spacing with water removal. Exposure to air causes rapid rehydration of this material, as determined by single crystal X-ray diffraction, powder X-ray diffraction, thermogravimetry and vibrational spectroscopy. Both the hydrated and dehydrated forms order magnetically below 60.5 K. Variation of the pillar and of the guest-exchange chemistry, including the exchange of magnetic
guests such as O2, offers the possibility of tailoring the magnetic properties of this material.
M. Kurmoo, H. Kumagai, S. Hughes, C. J. Kepert, J. Am. Chem. Soc. 2002, submitted.
-H2O
+H2O
IC-03 February 2-6, 2003 Melbourne 177 Tractable Autocatalytic Substitution Processes
W. Greg Jackson,a* Kate Goodyear,a Josephine A. McKeon,a Ben Freasiera and Kerrina Wellsa a School of Chemistry, University College (UNSW), ADFA, Canberra ACT [email protected]
The kinetics of substitution of octahedral cobalt(III) complexes have been studied for many years yet it remains curious that new mechanistic facets continue to turn up that are quite unexpected.
This poster deals with two such reactions. One is a substitution reaction between trans- + 2- [Co(en)2Cl2] and SO3 which is unusually fast and which leads to essentially complete direct anion substitution in aqueous solution, which is unprecedented. The reaction is autocatalytic, and an inner sphere redox mechanism is proposed. The second reaction is 2+ the base catalysed substitution of the [Co(Npy4)Cl] complex shown below. The reaction is clean and the kinetics are reproducible, first order in hydroxide ion but not first order in complex - again the reaction is a classical autocatalytic process. Less than one CH proton is exchanged at the –CH2- centres a to the pyridyl residues, and so this cannot be the source of the catalysis (as has been shown for the asym- [Co(dmpmetacn)C]2+ complex, for example). Again, a redox mechanism is proposed. Co(II) scavengers such as edta do not inhibit the base catalysis.
H N N Me N N N Cl
Co Co N N N N N Cl
2+ [Co(Npy 4 )Cl] asym -[Co(dmpmetacn)Cl]
IC-03 February 2-6, 2003 Melbourne 178 Structural Characterization of the Tungsten Tricarbonyl Cationic + Complex, [Tp*W(CO)3(MeCN)] , an Intermediate in a Host of Organometallic Chemistry
Michael S. Malarek, Brett A. Logan, Jonathan M. White and Charles G. Young School of Chemistry, University of Melbourne, Victoria 3010. [email protected]
The organometallic chemistry of the trispyrazolylborate complexes continues to attract world– wide attention.[1] Templeton and co-workers have made use of a 16-electron cationic complex as an intermediate in a variety of reactions.[2-4] This intermediate was thought to be + [Tp*W(CO)3] (Tp* = hydrotris(3,5–dimethylpyrazolyl)borate). Templeton also postulated that the cationic complex might bind a solvent molecule in accordance with 18-electron guidelines. In each case Templeton and co-workers were unable to isolate the intermediate, instead using it as a versatile in situ reagent. We have been successful in the isolation and full characterization, including X-ray crystal structure of this complex.
In this paper we describe the preparation and characterization of this complex (structure shown below). Prepared in acetonitrile the complex binds acetonitrile. Also, the cationic complex was - - synthesised as the BF4 and the triflate salt.
O C C C O N C W C O N N N
+ Figure 1. Structure of [Tp*W(CO)3(MeCN)]
[1] S. Trofimenko, Scorpionates, Imperial College Press, 1999. [2] S.G. Feng, C.C. Phillipp, A.S. Gamble, P.S. White, J.L. Templeton, Organometallics. 1991, 10, 3504. [3] C.C. Phillipp, P.S. White, J.L. Templeton, Inorg. Chem. 1992, 31, 3825. [4] S.G. Feng, P.S. White, J.L. Templeton, Organometallics, 1994, 13, 1214.
IC-03 February 2-6, 2003 Melbourne 179 Possible Fluorescent Switches From 4-Substituted Naphthalimides C. John McAdam,a Anthony R. Manning,b Brian H. Robinson,a and Jim Simpsona a Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand. b Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland. [email protected] Naphthalimides offer themselves to a diverse range of substitution chemistry through both the imide nitrogen and single or multiple substitution on the naphthalene ring. In particular amino substitution at the 4-position often leads to highly fluorescent compounds, a property that has resulted in extensive use in many areas of biological and physical study.
We have previously reported a series of compounds with ferrocenyl groups attached to the imide N [1]. We now present the synthesis and physical properties of a series of organometallic 4- substituted naphthalimides. UV-vis spectra show a strong CT transition ca. 500 nm.
O O
hu X X
+ - Fc O Fc O
[1] C.J. McAdam, B.H. Robinson and J. Simpson, Organometallics, 2000, 19, 3644.
IC-03 February 2-6, 2003 Melbourne 180 125Te MAS NMR and X-Ray Diffraction Studies of Diorganotellurium Dichlorides, R2TeCl2 and Diorganotellurium Oxides, R TeO (R = Ph, p-Me-C H , p-MeO-C H ). 2 6 4 6 4 Jens Beckmann, Dainis Dakternieks, Andrew Duthie, Naomi A. Smith Centre for Chiral and Molecular Technologies, Deakin University, Geelong 3217 Australia [email protected]
One of the most marked features of diorganotellurium dichlorides, R2TeCl2 and
diorganotellurium oxides, R2TeO is the presence of secondary Te···X interactions (X = Cl, O) in the solid state. In this work we present the first example of a polymeric
diorganotellurium oxide, namely [(p-MeO-C6H4)2TeO]n.
125Te MAS NMR spectroscopy - including the results of Herzfeld and Berger tensor analyses - was utilised to probe structural differences related to secondary interactions
in R2TeCl2 and R2TeO (R = Ph, p-Me-C6H4, p-MeO-C6H4). For instance, the
polymeric [(p-MeO-C6H4)2TeO]n which contains no secondary interactions can be
differentiated from the dimeric Ph2TeO, that displays secondary Te···O interactions, using this technique.
IC-03 February 2-6, 2003 Melbourne 181 Reverse Bola-Amphiphiles Incorporating ‘Cage’ Complexes
Jack M. Harrowfield, George A. Koutsantonis, Gareth L. Nealon, Brian W. Skelton, Allan H. White Chemistry, School of Biomedical and Chemical Sciences, University of Western Australia, Perth, Western Australia, 6009. [email protected]
As potential head groups for surfactant molecules, complex cations and anions offer the chance to introduce entities, often chiral, of unusually high charge, of variable spectroscopic and magnetic properties, and with structures that may facilitate specific forms of association of counterions with those head groups. The kinetic inertness and ease of functionality of cage amine complexes [1,2] render them particularly appealing for use as head groups and it has been shown that surfactants derived from Co(III) cage complexes do have unusual physical and biological properties [3].
In seeking to expand this field of chemistry, we have investigated the syntheses of amphiphiles and what might be termed « reverse » bola-amphiphiles [4] based on cage amine complexes of various metals. This is being achieved by the use of reductive alkylation of the amine groups with a long chain aldehyde, giving products with the general structure shown below (Figure 1).
N H HN
N H N H HN HN ( ) x ( ) x
N H HN
x = 1-12 Figure 1. Reverse bola-amphiphilic ligands under study.
Initial results have indicated that complexes of these ligands show some interesting aggregation behaviour in the solid state, and work is ongoing to establish their association in solution.
[1] P. S. Donnelly and J. M. Harrowfield, J. Chem. Soc., Dalton Trans, 2002, 906. [2] S. Burnet, M-H. Choi, P.S. Donnelly, J.M. Harrowfield, I. Ivanova, S-H. Jeong, Y. Kim, M. Mocerino, B.W. Skelton, A.H. White, C.C. Williams and Z-L. Zeng, Eur, J. Inorg.Chem., 2001, 1869. [3] C. A. Behm, P. F. L. Boreham, I. I. Creaser, B. Korybut-Daszkiewicz, D. J. Maddalena, A. M. Sargeson and G. M. Snowdon, Aust. J. Chem. 1995, 48, 1009. [4] J-H. Fuhrhop and D. Fritsch, Acc. Chem. Res. 1986, 19, 130.
IC-03 February 2-6, 2003 Melbourne 182
Carbonyl-carboxylato-ruthenium Complexes Incorporating Diimine Ligands Pauline Pearson,a Christopher M. Kepert,a Glen B. Deacon,a Leone Spiccia,a Andrew C. Warden,a Brian W. Skelton,b Allan H. White.b a School of Chemistry, Monash University, 3800, Victoria, Australia b Crystallography Centre, University of Western Australia, Nedlands, 6907, WA, Australia [email protected]
Carbonyl-carboxylato complexes of ruthenium (Figure 1) have shown great promise as catalysts for organic transformations [1], however their application has been limited due to the high cost of
existing syntheses based on Ru3(CO)12. We report two new synthetic routes to the dinuclear Ru(I) complexes, R + I + [Ru 2(CO)4(RCO2)(N-N)2] (N-N = 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) derivatives (Figure O O O N 1(a))) using the cheaper starting material, RuCl3.H2O. C N I I Direct addition of the desired diimine ligand to a Ru Ru N C N [Ru(CO)2Cl2]n/MeCO2Na solution yielded both Ru(I) O I + OC CO (a) and Ru(II) complexes, [Ru 2(CO)4(MeCO2)(N-N)2] (N- RCO N = 4,4'-Me2bpy, 4,4'-(CO2H)2bpy and 5,6-Me2phen), 2 II N CO and [Ru (CO)2(MeCO2)2(N-N)] (N-N = 4,4'-Me2bpy RuII and 5,5'-Me2bpy). X-ray crystallography confirmed that the Ru(II) complexes had a cis-carbonyl-trans-acetate N CO RCO arrangement of the ligands (Figure 1(b)). Use of 2 (b) PhCO2Na gave unexpected ortho- cyclometallated Figure 1. I + II (a) [Ru 2(CO)4(RCO2)(N-N)2] complexes, [Ru (O2CC6H4)(CO)2(N-N)], N-N = bpy II (b) [Ru (CO)2(RCO2)2(N-N)], and phen (Figure 2). N-N = a diimine ligand such as (bpy) or (phen). Due to the problems encountered with the 'direct
addition' method, another approach was taken whereby O(4) ligand exchange between a diimine ligand (N-N) and I pyridine on [Ru (CO)2(RCO2)(py)]2, converted this neutral complex into cationic complexes, N(2) O(3) I + [Ru 2(CO)4(RCO2)(N-N)2] . This method although it Ru involved more steps, had broader application (R = Me N(1)
and N-N = 4,4'-Me2bpy, 5,5'-Me2bpy, 5,6-Me2phen; R = O(1) O(2) Ph and N-N = bpy, phen, 5,6-Me2phen) and was not Figure 2. [Ru(O CC H )(CO) (phen)] complicated by the formation of Ru(II) complexes. 2 6 4 2
[1] Frediani, P., Bianchi, M., Salvini, A., Carluccio, L.C., Rosi, L., J. Organomet. Chem., 1997, 547, 35.
IC-03 February 2-6, 2003 Melbourne 183 DNA Binding of Enantiomerically Pure Methylated Bimetallo Triple Helicates
Jemma C. Peberdy,a Alison Rodger,a Michael J. Hannon,a Syma Khalid,a Veronika Ruedegger,b Laura J. Childsa and Isabelle Meistermannc a Department of Chemistry, University of Warwick, Gibbett Hill Road, Coventry, CV4 7AL U.K. b Institute of Analytical Chemistry, University of Vienna, Wahringer Strasse 38, A-1090, Vienna Austria. c The Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands [email protected]
A range of bimetallo-supramolecular helicates has been prepared using a simplistic route for assembly from inexpensive starting reagents.[1] They have been designed with respect to common DNA binding motifs that are too large to fit into the minor groove of DNA, but are the ideal size for major groove binding.
The helicates are chiral compounds, which can be separated into the two enantiomers using cellulose column chromatography.[2] The cellulose column not only serves as a method for separating the enantiomers but also as a method for purification. Sodium chloride and a series of other solvents have been used to elute the enantiomers and their presence is confirmed using circular dichroism (CD) and UV/VIS spectroscopies.
The parent iron triple helicate is a major groove binder and the different enantiomers have different binding modes to DNA and different effects on the DNA structure. The DNA-binding modes of the methylated derivatives will now be studied, so that binding specificity can be investigated and introduced into the backbone of the ligand structure.
N N N N Me Me Figure 1. Ligand [CH2~H5Me]
[1] M. Hannon, C.L. Painting, A. Jackson, J. Hamblin, W. Errington. Chem. Commun. 1997, 1807. [2] M.J. Hannon, I. Meistermann, C.J. Isaac, C. Bloome, J.R. Aldrich-Wright, A. Rodger. Chem. Commun. 2001, 12, 1078-1079.
IC-03 February 2-6, 2003 Melbourne 184
Organometallic MnL(CO)3Br complexes of bidentate pyridyl/chalcogenoether ligands Brian W. Skelton,a Vicki-Anne Tolhurst,b Alan M. Williams b Adele J. Wilsonb and Allan H. Whitea a Chemistry Department, University of Western Australia, Crawley 6009, WA, Australia. b School of Chemistry, University of Tasmania, Private Bag 75, Hobart 7001, TAS, Australia. [email protected]
Over the past few years our research group has undertaken a study into the coordination chemistry of mixed pyridyl/chalcogenoether ligands. We have seen variations in the solid-state structure dependant on the electronic properties of such ligands [1] and recently have been able to establish trends in both the structures and electronic properties of pyridyl/chalcogenoether ligands on varying the chalcogen donor atom from sulfur to selenium [2]. We have also seen that complexes containing mixed pyridyl/thioether ligands facilitate catalytic processes [3].
Herein we report the preparation of the manganese complexes MnL(CO)3Br and discuss the variation in bonding characteristics bought about by differing bulkiness and electronic properties of the bidentate pyridyl/selenoether ligands, 1-3. On substitution of the electron donating –SiMe3 moieties on the a-carbon, the donor strength of the selenium donor atom is varied, altering the electronic properties of the metal complexes. These properties have been investigated using multinuclear NMR spectroscopy. The generic structure of these complexes has been authenticated by the solid state structure of [Mn(2-(PhSCH2)C5H4N)(CO)3Br].
1 2 R1 1 R =R =H 1 2 N 2 2 R =H, R =SiMe3 R 1 2 SeMe 3 R =R =SiMe3
[1] R.J. Ball, A.R.J. Genge, A.L. Radford, B.W. Skelton, V.–A. Tolhurst, and A.H. White, J. Chem. Soc., Dalton Trans., 2001, 2807. [2] B.W. Skelton, V.–A. Tolhurst, A.M .Williams, A.J. Wilson, A.H White, and B.F. Yates, unpublished results. [3] V.–A. Tolhurst, and A.M. Williams, unpublished results.
IC-03 February 2-6, 2003 Melbourne 185 Complexes facilitating the Heck reaction involving internal olefins: Pd(II) and Pt(II) complexes containing the mixed donor ligand 2-(RECH2)C5H3N Brian W. Skelton,a Vicki-Anne Tolhurst,b Alan M. Williams,b Adele J. Wilson,b Allan H. White,a and Brian F. Yatesb a Chemistry Department, University of Western Australia, Crawley 6009, WA, Australia b School of Chemistry, University of Tasmania, Private Bag 75, Hobart 7001, TAS, Australia. [email protected] The Heck reaction, involving the coupling of an olefin with an aryl halide, is one of the most versatile organic transformations currently known. Much research into the Heck reaction of terminal olefins and aryl halides is driven by the quest to find efficient catalysts which facilitate the reaction using cheap reagents, such as aryl chloride compounds, as to make the process attractive to industry. Interestingly, while this can be achieved with good to excellent turnover numbers under quite mild conditions, these conventional catalysts have not been successfully used to facilitate the reaction between internal olefins and aryl halides to prepare 1,1,2- trisubstituted alkenes (eg Scheme 1) [1].
Br MeOC CO Et cat, base + 2 Ph -base.HBr
COMe Scheme 1 Heck reaction involving internal alkenes CO2Et Here we report a group of palladium(II) halide complexes containing hemilable N/S mixed donor ligands (eg 1) which we have found to facilitate the reaction outlined in Scheme 1 in good yield with high stereoselectivity. These complexes represent the first well-defined complexes which catalyse the Heck reaction of internal olefins, to the best of our knowledge. Previously reported Me systems that undertake this reaction have used Jeffrey’s conditions [2], which S Cl involves the in situ formation of the catalyst. The presence of the mixed donor Pd ligand results in increased reactivity when comparing performance of these N Cl Pd(II) catalysts with the that of analogous Pd(II) catalysts containing the 1 homoleptic bidentate ligands 2,2’-dipyridyl (BIPY) or 2,5-dithiahexane.
To help understand the electronic and bonding features of our catalysts, we have undertaken solution and solid state studies, namely multinuclear NMR spectroscopy and single crystal X-ray diffraction, of a number of Pd(II) and Pt(II) complexes containing either thio- or selenoether ligands. The bonding and electronic features observed will also be discussed.
[1] S. Bräse, and A. de Meijere in Metal-Catalysed Cross-Coupling Reactions, F. Diederich, and P. J. Stang, Eds, Wiley, New York, 1998, pg 102.
[2] A.F. Littke, and G.C. Fu, J. Am. Chem. Soc., 2001, 123, 6989; C. Gürtler, and S. L. Buchwald, Chem. Eur. J., 1999, 5, 3107.
IC-03 February 2-6, 2003 Melbourne 186 Highly Localised Charges Control Electrostriction. Redox Reaction Volumes for Mononuclear and Bridged Ru Complexes Hari C. Bajaj,a,c Peter A. Tregloan,b and Rudi van Eldika a Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat, India b School of Chemistry, University of Melbourne, 3010, Victoria, Australia c Instutute for Inorganic Chemistry, University of Erlangen-Nurnberg, Egerland Str 1, 91058 Erlangen, Germany . [email protected] .
High pressure electrochemistry makes it possible to determine the molar volume changes associated with redox processes.[1, 2] These changes may be intrinsic, corresponding to molecular changes in the reactants, or electrostricitve, corresponding to the adjustment of surrounding solvent to the changes in charge occurring during the redox process. The surfaces of complex molecules like proteins include a range of ionisable functional groups and the distinctions between local and overall molecular charges are important in describing their chemistry.
To extend our efforts probing the effects of nearby charges on solvent around the redox centres, (III)/(II) [3] we have carried out high pressure studies on (i) the Ru [edta]H2O system, where the system can be protonated/detprotonated at the aqua or pendant carboxylate sites and (ii) the (III)/(II) (III)/(II) (III)/(II) dinuclear [edta]Ru CNFe(CN)5 and (NH3)5Ru CNFe (CN)5 systems, where the pressure effects on the Ru and Fe redox systems can be independently measured. Intrinsic and electrostrictive contributions can be resolved and it is apparent that the effects on surrounding solvent is limited only to regions within the immediate solvation environment..
[1] Swaddle, T.W.; Tregloan, P.A. Coord. Chem. Rev. 1999, 187, 255. [2] Sachanidis, J. I.; Shalders, R. D.; Tregloan, P. A. Inorg. Chem. 1996, 35, 2497. [3] Yeomans, B. D.; Kelso, L. S.; Tregloan, P. A.; Keene, F. R. Eur. J. Inorg. Chem. 2001, 239.
IC-03 February 2-6, 2003 Melbourne 187 Scorpionates: Poly(methimazolyl)borate Chemistry of Divalent Ruthenium Alison J. Edwards,a Anthony F. Hill,a,b Mark R. St.-J. Foreman,b Never Tshabang,a Andrew J. P. White,b David J. Williamsb and Anthony C. Willisa a Research School of Chemistry, Australian National University, ACT 0200, Australia b Imperial College of Science, Technology and Medicine, London SW7 2AY, U.K. [email protected] The poly(pyrazolyl)borate class of ligands developed by Trofimenko present a set of three nitrogen donors for facial coordination to a metal centre.[1] Soft tridentate sulphur containing macrocycles such as 1,4,7-trithiacyclononane, ([9]aneS3) also coordinate facially to a metal centre, however the thioether macrocycles do not carry and overall charge, therefore they are not able to completely offer a controlled and graded alteration of the chemistry of the metal complexes [2]. Recently, Reglinski reported the synthesis of poly(methimizolyl)borate ligands
[3], (Figure 1) which might be considered as hybrids of the HB(pz)3 and [9]aneS3 ligands.
(a) Hmt (b) H2 B(mt)2 (c) HB(mt) H - N HN N B N H N S N N S S S N B - N H N N S S N
Figure 1. The ligands Hmt, H2B(mt)2, HB(mt)3
This poster explores the analogy between these three ligands within the chemistry of divalent ruthenium in addition to the synthesis of range of ruthenaboratrane complexes such as
[Ru{B(mt)3}(CO)L](Ru®B) (L= PPh3, PMe2Ph,
P(OMe)3, PCy3,) and a variety of substitution reactions. Reactions of the bidentate variant
H2B(mt)2 with Ru(II) precusors provide complexes with agostic B-H-M interactions, e.g,
[RuCl(CO)(PPh3){H2B(mt)2}] (see left). Preliminary results suggest the following tentative conclusions: (i) The HnB(mt)4-n ligands show a greater propensity for agostic B-H-M interactions than do the related HnB(pz)4-n ligands. (ii) The HnB(mt)4-n ligands, whilst hydrolytically stable, are more prone to hydrolysis during coordination sequences than are the
HnB(pz)4-n ligands. [1] Review: Trofimenko, S. “Scorpionates: The Coordination Chemistry of Polypyrazolylborate Ligands” Imperial College Press: London 1999; [2] Review: Blake, A. J.; Schroder, M. Adv. Inorg. Chem. 1990, 35, 1.
IC-03 February 2-6, 2003 Melbourne 188 Isocyanide Substitution and Core Expansion at Molybdenum – Iridium Mixed-Metal Clusters Alistair J. Usher,a Nigel T. Lucas,a Gulliver T. Dalton,a Mark G. Humphreya and Anthony C. Willisb a Department of Chemistry, Australian National University, 0200, ACT, Australia b Research School of Chemistry, Australian National University, 0200, ACT, Australia [email protected] Metal carbonyl clusters exhibit interesting chemical, electronic, magnetic and optical properties.[1] Mixed-metal clusters incorporating disparate metals maximize metal-metal bond polarity (and thereby substrate activation) and raise the prospect of reagent metalloselectivity. We recently reported a study of cyclopentadienyl ligand- and phosphine ligand- varied tetrahedral group 6 – iridium clusters.[2] We have now investigated isocyanide substitution chemistry and reaction with carbonylmetallate anions, the latter affording a high yielding synthesis of core-expanded, medium-nuclearity, trigonal bipyramidal mixed-metal clusters.
The highly ligand substituted but sterically unencumbered tetranuclear cluster Mo2Ir2(m- t CO)2(CN Bu)2(CO)6(h-C5H5)2 displays an unprecedented carbonyl ligand disposition about its tetrahedral core. Sterically more encumbered clusters compensate by core bond lengthening and unsymmetrical carbonyl ligand dispositions.
Core expansion of the tetrahedral clusters
MIr3(CO)10(L)(h-C5H5-nMen) (n = 0, 4, 5; M = Mo, W; L = CO, tBuNC; not all cases) yields trigonal-bipyramidal clusters
M2Ir3(m3-H)(m-CO)2(CO)9(h-C5H5-nMen)(h-
C5H5-mMem) (n = 0, 4, 5; m = 4, 5; M = Mo, W; not all cases) and is strongly dependent on cyclopentadienyl ring variation and the presence of a spectator ligand. We have observed vertex replacement in this system, examples of tungsten vertex replacement Figure 1. X-ray crystal structure of Mo2Ir3(m3-H)(m- with both molybdenum fragments and CO)2(CO)9(h-C5H5)(h-C5Me5). another tungsten fragment being observed, a first for vertex replacement studies.
[1] M.P. Cifuentes, M.G. Humphrey, J.E. McGrady, P.J. Smith, R. Stranger, K.S. Murray and B. Moubaraki, J. Am. Chem. Soc., 1997, 119, 2647. [2] N.T. Lucas, J.P. Blitz, S. Petrie, R. Stranger, M.G. Humphrey, G.A. Heath and V. Otieno- Alego, J. Am. Chem. Soc., 2002, 124, 5139.
IC-03 February 2-6, 2003 Melbourne 189 Metal Complex Catalysed C-S Bond Formation Barbara Messerle,a Peter Turner,band Khuong Vuonga a School of Chemical Sciences, University of New South Wales, 2052, NSW, Australia b School of Chemistry, University of Sydney, 2006, NSW, Australia [email protected]
Cationic complexes of rhodium(I) and iridium(I) with bidentate + - BPh4 N nitrogen donor ligands, [M(N-N)(CO)2]BPh4 (M= Rh, Ir; N-N = bis- 1-methylimidazol-2-ylmethane or bis-1-pyrazolylmethane), e.g. 1, N CO Ir have been shown to be highly effective as catalysts for the CO N hydroamination of alkynes [1] and the addition of OH to alkynes [2]. N We have recently developed the Rh and Ir complexes with the new 1 potentially hemilabile P,N ligands, 1-(2-diphenylphosphinoethyl)pyrazole, 1-(2- diphenylphosphinoethyl)-3,5-dimethylpyrazole e.g. 2, 3, 4 . These complexes have been characterized by NMR and the solid state structures of 2 and 3 were determined by single crystal X-ray crystallographic analysis.
+ - + - Ph2 BPh4 PPh2 BPh4 PPh2 CO P CO
M M M
Cl CO N N N N N N
2, M = Ir, 2a; Rh, 2b 3, M = Ir, 3a; Rh, 3b 4, M = Ir, 4a; Rh, 4b
While many thiolate complexes of transition metals are known, the use of thiols as substrates in metal-catalysed formation of C-S bond has been little explored [3]. We have shown that
complexes [M(N-N)(CO)2]BPh4 are effective as catalysts for the addition of thiophenol to a variety of alkynes (Scheme 1). The reaction has excellent regioselectivity with the formation of only the ani-Markovnikov products. Complexes with bidentate P,N-donor ligands were shown to catalyse the same reaction affording a different regioselectivity in comparison to the complexes containing bidentate N,N-donor ligands.
R H H H R H [M] R H + PhS H + + H SPh R SPh PhS H R = P h, M e3S i, H OCH 2, n-propyl E Z Markovnikov anti-M arkovnikov
Schem e 1
= [1] S. Burling, L.D. Field, B.A. Messerle, Organometallics, 2000, 19, 87-90. [2] S. Elgafi, L.D. Field, B.A. Messerle, J. Organomet. Chem., 2000, 607, 97-104. [3] A. Ogawa, T. Ikeda, K. Kimura, and T. Hirao, J. Am. Soc., 1999, 121, 5108-5114.
IC-03 February 2-6, 2003 Melbourne 190 Investigation of Rotamers About the Pt-N7 Bonds in Bulky [Pt(d(GpG))(diamine)] Complexes Mark P. Waller, Genevieve H. Bulluss and Trevor W. Hambley Centre for Heavy Metals Research School of Chemistry, University of Sydney, 2006, New South Wales, Australia [email protected] Cisplatin binds to DNA primarily as a GpG bifunctional adduct and this is believed to be responsible for its pharmacotherapeutic action. A range of complexes of the form [Pt(d(GpG))(diamine)] have been investigated as models for these adducts with a view to rational drug design. Marzilli and co-workers examined the rotation about the Pt-Guanine bond and found there to be four rotamers [1]. Here, we have used a combination of modelling and HPLC to gain an increased understanding of the behaviour of these adducts.
Compounds such as 2-chloro-aminomethylpyridineplatinum(II) were designed to be asymmetric to probe the steric ramifications of interactions with DNA. Compounds such as 5,5’-dimethyl- 2,2’-bipyridineplatinum(II) were designed to have a bulky nature such that there are steric interactions which slow down the rotation allowing these to be resolved via HPLC. 2D contour maps of the strain energy versus torsion angle revealed the thermodynamically stable conformers. The graphical representation of the data allows identification of the high and low energy pathways between conformations. The HPLC and GF-AAS profiles of the dinucleotides indicate that up to four rotamers are present.
[1] L. G. Marzilli, S. O. Ano, F. P. Intini and G. Natile, J. Am. Chem. Soc., 1999, 121, 9133.
IC-03 February 2-6, 2003 Melbourne 191 Alkali Metal Inclusion Capabilities as a Destabilising Effect in Macrocyclic Organolanthanide Complexes Leading to Complete Metal Exchange Michael G. Gardiner,a Brian W. Skelton,b Jun Wang,a Allan H. Whiteb a School of Chemistry, University of Tasmania, Private Bag 75, Hobart TAS 7001 Australia b Chemistry Department, University of Western Australia, Crawley WA 6009 Australia [email protected] We have been studying lanthanide complexes of modified calix[4]pyrroles, 1 (unmodified macrocycle), with the view to realising their utility as alternatives to the ubiquitous bis(pentamethylcyclopentadienyl) ligand set. Until now we have been studying systems based on the trans-N,N'-dimethylated and furan substituted macrocyclic systems 2 and 3.[1,2]
R R R R R R R R R R N N R O R H Me NH HN N N N N H Me N 1 N 2 O 3 R R R R R R R R R R R R Analogous lanthanide(II) and (III) complexes featuring 2 and 3 have many obvious similarities, however an important structural difference is the ability of the less sterically demanding furan containing macrocycle to host alkali metals within the macrocyclic cavity, for example, the Sm(II) complex of 3 retains some residual KI from the synthetic method used (on right). Whilst alkali metal inclusion capabilities has inspired some interesting possibilities in synthetic applications for future study, this structural feature appears to offer a mechanism to destabilise lanthanide complexes in some cases. The samarium(III) bis(trimethylsilyl)amide complex featuring 3
is rapidly deprotonated by NaN(SiMe3)2 affording the g- alkylamide complex (on left) in which the toluene solvated sodium cation is accommodated within the cavity of the macrocycle. In the presence of additional base, complete metal exchange is observed, leading to the formation of the disodium
macrocyclic complex and [Sm{N(SiMe3)2}3]. We are currently investigating the mechanism by which metal exchange takes place and further investigating reactivity comparisons between analogous complexes featuring macrocycles 2 and 3.
[1] Y. Furusho, H. Kawasaki, S. Nakanishi, T. Aida and T. Takata, Tetrahedron Lett., 1998, 39, 3537. [2] R. Crescenzi, E. Solari, C. Floriani, A. Chiesi-Villa and C. Rizzoli, Inorg. Chem., 1996, 35, 2413.
IC-03 February 2-6, 2003 Melbourne 192 Inorganic Asymmetric Synthesis: Stereoselective Synthesis of Two-Bladed Propeller Octahedral Metal Complexes Rebecca J. Warra and S. Bruce Wilda a Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia [email protected] Modern organic synthesis is at the level of an art form, with most types of organic compounds now being available as single diastereomers or enantiomers following highly stereoselective and frequently catalytic reactions; inorganic synthesis by comparison has changed little in 100 years - most metal complexes are still prepared as mixtures of stereoisomers that require tedious separations and resolutions by traditional methods. We have embarked on a program aimed at demonstrating that chiral metal complexes can be prepared by asymmetric synthesis - inorganic asymmetric synthesis. One approach through which chiral information can be transmitted to a metal centre is with the use of an enantiomerically pure chiral auxiliary that can be subsequently removed to leave the metal complex, chiral at the metal alone. For this method to be successful, the product must have sufficient chemical stability to withstand the conditions of the synthesis and configurational stability to observe the single enantiomer produced. For these reasons, we
have chosen two-bladed propeller complexes of the types (±)-[M(PAPHY)2]X2 and (±)-
[M(PAPY)2], which are available for a wide range of metals and for which the nickel(II) and zinc(II) complexes have been resolved [1]. Our progress on this project concerning the
asymmetric synthesis of the zinc(II) complexes with the C2 ligand 1 will be described.
O O H H N R R N N N N O O N N N
O O 1
[1] J. F. Geldard and F. Lions, Inorg. Chem. 1963, 2, 270-282.
IC-03 February 2-6, 2003 Melbourne 193 Compounds of Nickel(II) with 5,12-Dimethyl-7,14-diphenyl-1,4,8,11- tetraazacyclotetradecane, L
Donald F. Cook,a Neil F. Curtis,a Olga P. Gladkikh,a Clifton E. F. Rickardb, Joyce M. Watersc and David C. Weatherburna a School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box. 600, Wellington, New Zealand. b Department of Chemistry, University of Auckland, Auckland, New Zealand. c Institute of Fundamental Sciences - Chemistry, Albany Campus, Massey University, Auckland, New Zealand. [email protected] Compounds of three isomers of the macrocyclic amine 5,12-dimethyl-7,14-diphenyl-1,4,8,11- tetraazacyclotetradecane (L) have been prepared; meso-meso, mmL, rac-meso, rmL and rac-rac, rrL. All three isomers form nickel(II) compounds in both planar (square-planar and trans octahedral) and folded (cis-octahedral) coordination, but the relative stabilities of these depend on the nitrogen configuration, the macrocyle conformation and axial/equatorial orientation of the substituents present. Structures of compounds of [Ni(mmL)]2+ with configurations II, III and V, of [Ni(rmL)]2+ with configuration III and V and of [Ni(rrL)]2+ with configurations I and V are described.
2+ 2+ 2+ Me Ph Me Ph Me Ph
HN NH HN NH HN NH Ni Ni Ni HN NH HN NH HN NH
Ph Me Ph Me Ph Me
2+ 2+ 2+ [Ni(mmL] [Ni(rmL] [Ni(rrL)]
IC-03 February 2-6, 2003 Melbourne 194 Targeting DNA with Macrocycle-Intercalator Complexes Renee M Whan, Leanne Ellis and Trevor W Hambley Centre for Heavy Metals Research, School of Chemistry, University of Sydney, N.S.W. 2006, Australia [email protected] The localisation of macrocyclic metal complexes on DNA is of interest for a number of reasons: if the metal ion is a radionuclide, increased DNA damage will result, if it is a metal that facilitates phosphate hydrolysis, then DNA cleavage may result and if the metal binds to DNA bases, then sequence selective binding can occur. Intercalators bind rapidly and reversibly to DNA and have been shown to increase the rate and extent of DNA binding of a variety of groups including metal complexes. Kimura and colleagues have described a series of cyclen type macrocyclic complexes linked to intercalators and have shown that these interact in a sequence selective manner with DNA.1 We have been investigating the combination of cyclam (1,4,8,11- tetraazacyclotetradecane) based macrocycles with 1- and 2-substituted anthraquinones. The copper complexes of these adducts were prepared and the crystal structure of the complex of 1C2mac (Cu-1C2mac) was determined as the hexafluorophosphate salt (Figure 1). The equilibrium binding constants and reaction with plasmid DNA allowed comparison between the cyclam/anthraquinone adducts, their copper complexes and the intercalators alone. Addition of the macrocycle increased the extent and effect of DNA intercalation and addition of copper increased the effect still further. None of the adducts inhibited cleavage at dGpG or dGpC sites by restriction enzymes. The adducts with the longer side chains caused substantially more unwinding of the DNA. Figure 1: Crystal structure of Cu-1C2mac
A new approach towards the synthesis of macrocycle-intercalator complexes has been employed due to the inherent disadvantages associated with nitrogen functionalised macrocycles. The new method involves the synthesis of methylene functionalised macrocycles with an amine pendant group, for the subsequent nucleophilic substitution to the anthraquinone.
A new, convenient procedure for producing macrocycles has been developed. An appropriately substituted malonic ester is condensed with a linear tetraamine to produce the cyclic diamide. To isolate the macrocycle, copper(II) is coordinated and the complex is purified by cation-exchange chromatography with good yield. Treatment of the copper(II) complex with a zinc-mercury amalgam afforded the desired product.
[1] E. Kimura, T. Ikeda and M. Shionoya, Pure Appl. Chem., 1997, 69, 2187.
IC-03 February 2-6, 2003 Melbourne 195 Synthesis, Structure and Magnetism of new Mixed-valent Manganese Clusters Lisa Wittick,a Stuart R. Batten,a Kevin J. Berry,b Boujemaa Moubaraki,a Keith S. Murray,a David J. Price,a Leone Spicciaa a School of Chemistry, Monash University, Clayton, 3800, Victoria, Australia b Westernport Secondary College, Hastings, 3915, Victoria, Australia [email protected]
Since the determination of the structure of Mn12–acetate in the early 80's and the subsequent discovery of its single molecule magnet (SMM) characteristics, interest in the area of large metal clusters, particularly Mn cluster chemistry, has continued to grow. A key reason for this is because of their quantum behaviour. To date, several SMMs have been identified including
Fe8[1], V4[2], and Mn4 [3] clusters. The Mn clusters often possess large values of ground state spin and negative anisotropy (i.e. D negative) – important requirements for SMM behaviour. As part of a nanochemistry and nanomaterials project, our group is interested in the synthesis of new Mn clusters and the investigation of their structural and magnetic properties. The current focus is on the incorporation of bridging ligands other than O-donor ligands, the latter having been much studied by Christou and co-workers [2, 3].
A new Mn trimer has been formed with benzamidine (bza - PhCNH(=NH)-). (Figure 1) The cluster is mixed valent III II (2Mn , Mn ) and possesses an oxo-centered Mn3O unit with 6 bza groups providing peripheral ligation and three pyridine groups in a terminal position. The cluster displays antiferromagnetic coupling similar to the benzoate Figure 1. [Mn O(bza) (pyr) ] analogue. 3 6 3
A new Mn tetramer has been formed with triethanolamine
(N(EtOH)3 = LH3) (Figure 2) of formula
[Mn4(LH2)2(LH)2(H2O)2(OAc)2]. The cluster is mixed valent (2MnII, 2MnIII) and magnetic studies have shown it to be ferromagnetically coupled, with a significant D value and low-lying states (S=6, 7, 8) within 50cm-1 of the Figure 2. [Mn4(LH2)2(LH)2(H2O)2(OAc)2] ground state S=9. The best fit J values will be discussed. Preliminary investigations point to the possibility of SMM behavior and further magnetic studies are underway to fully characterise the magnetic properties of this cluster.
[1] C. Sangregorio, T. Ohm, C. Paulsen, R. Sessoli and D. Gatteschi, Phys. Rev. Lett., 1997, 78, 4645
[2] S. L. Castro, Z. Sun, C. M. Grant, J. C. Bollinger, D. N. Hendrickson and G. Christou, J. Am. Chem. Soc., 1998, 120, 2365 [3] S. M. J. Aubin, M. W. Wemple, D. M. Adams, H.-L. Tsai, G. Christou and D. N. Hendrickson, J. Am. Chem. Soc., 1996, 118, 7746
IC-03 February 2-6, 2003 Melbourne 196 New Stannyl Complexes of Osmium Through Nucleophilic Displacement of the Iodo Groups on Iodostannyl Ligands Guo-Liang Lu, Clifton E. F. Rickard, Warren R. Roper, George R. Whittell, and L. James Wright Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand [email protected]
2 The series of iodo, methyl stannyl complexes, Os(SnInMe3-n)(h -S2CNMe2)(CO)(PPh3)2, (n = 0- 3) has been prepared through SnI4 I2 selective redistribution reactions LnOs SnMe3 LnOs SnMeI2 LnOs SnI3 involving treatment of the LnOs SnMe2I trimethylstannyl complex, LnOs SnMeI2 2 Os(SnMe3)(h - 2 Scheme 1 [LnOs = (h -S2CNMe2)(CO)(PPh3)2] S2CNMe2)(CO)(PPh3)2, with SnI4 and methyl group cleavage reactions with I2 (see Scheme 1). These complexes are ideal substrates for the synthesis of interesting, new stannyl complexes through displacement of the iodo groups by H- 2 LnOs SnI3 LnOs SnH3 nucleophiles. For example, Os(SnH3)(h - 2 - S2CNMe2)(CO)(PPh3)2, Os(Sn{OH}3)(h - OH N(CH2CH2OH)3
S2CNMe2)(CO)(PPh3)2 and L Os Sn(OH) L Os Sn({OCH CH } N) 2 n 3 n 2 2 3 Os(Sn{OCH2CH2}3N)(h - 2 Scheme 2 [LnOs = (h -S2CNMe2)(CO)(PPh3)2] S2CNMe2)(CO)(PPh3)2 can all be prepared from the corresponding tri-iodostannyl complex (see Scheme 2).
2 - Treatment of Os(SnIMe2)(h -S2CNMe2)(CO)(PPh3)2 with the anions [SnR3] (R = Me, Ph) produces the distannyl complexes, - [SnR3] Me 2 Os(SnMe2SnR3)(h -S2CNMe2)(CO)(PPh3)2. LnOs SnMe2I LnOs Sn Me (R = Me, Ph) SnR One of the a-tin methyl groups in each of these 3 SnMe2Cl2 complexes undergoes selective exchange with - Me [SnPh3] Me chloride on treatment with SnCl2Me2, and this LnOs Sn SnPh3 LnOs Sn Cl provides a rational synthetic route to the SnPh3 SnR3 2 tristannyl complex, Scheme 3 [LnOs = (h -S2CNMe2)(CO)(PPh3)2] 2 Os(SnMe{SnMe3}{SnPh3})(h -
S2CNMe2)(CO)(PPh3)2 (see Scheme 3). Spectroscopic data and information on the reactivity of these new compounds will be presented, as well as X-ray crystallographic determinations of the structures of selected compounds.
IC-03 February 2-6, 2003 Melbourne 197
Structural Characterisation of a Novel Mo16 Polyoxomolybdate Containing a
Mo4O4 Cubane
Lyndal M. R. Hill, Brendan F. Abrahams and Charles G. Young School of Chemistry, University of Melbourne, 3010, Victoria, Australia [email protected]
A new Mo16 oxometalate framework has been crystallised through deterioration of a well Pr Pr characterised mononuclear Mo(VI) complex. Tp MoO2(2,3-dimethoxyphenolate) (Tp = hydro- tris(3-isopropylpyrazolyl)borate) may be crystallised as amber plates by aerobic diffusion of methanol into a CH2Cl2 solution. However, it appears that if crystallisation is slow relative to degradation of the complex crystal growth results in the formation of a polymolybdate (see Figure 1).
Figure 1. The Mo/donor atom core of the Mo16 molecule. The donor ligands comprise oxo, pyrazolato and methoxy/hydroxy groups. The 12 flanking pyrazole rings, H-atoms and lattice solvent have been omitted in this view.
The Mo16 complex can be viewed as an outer string of Mo and O, incorporating three of the five
Mo2O2 diamond moieties, and encapsulating a central Mo4O4 cubane. These structural units and a complete representation of the molecule will be presented, along with a discussion of related polyoxomolybdates.
IC-03 February 2-6, 2003 Melbourne 198 Synthesis and Reactivity of Cationic Organotin species featuring Sn-O-P linkages
Jens Beckmann, Dainis Dakternieks, Andrew Duthie, Cassandra Mitchell Centre for Chiral and Molecular Technologies, Deakin University, Geelong 3217 Australia [email protected]
The synthesis of a new class of cationic organotin (IV) species, such as cyclo-
[R2Sn(OPPh2O)2SnR2](O3SCF3)2, [R2Sn(H2O)2(OPPh3)2](O3SCF3)2 and,
[R3SnOPPh2SnR3](O3SCF3) (R = alkyl, aryl), including Sn-O-P linkages will be presented.[1] These compounds are highly soluble in organic solvents and involved various equilibria with organotin species. Compounds have been characterised by solution and solid-state NMR spectroscopy, ESI MS spectrometry, IR spectroscopy, thermogravimetry and X-ray crystallography. The following figure shows the crystal structure of cyclo-[t-Bu2Sn(OPPh2O)2Snt-Bu2](O3SCF3)2 which contains a highly- puckered eight-membered ring.
[1] V. K. Jain, Coord. Chem. Rev., 1994, 135/136, 809.
IC-03 February 2-6, 2003 Melbourne 199 From Organometallic Rigid-Rods Towards Organometallic NanoStars: Electronically Bridged Nanostructured Materials by Design Allen D. Hunter,a Matthias Zeller, Evelyn Lazich, Cynthia Perrine, Jim Updegraff, Steven DiMuzio, Les McSparrin, Nathan Takas, Floyd Snyder, Robert Wilcox, Lisa Walther, and Monique Peace a Department of Chemistry, Youngstown State University, 1 University Plaza, Youngstown, Ohio, USA 44555-3663. [email protected] There is substantial interest in new materials exhibiting three dimensional structures that are patterned on the nanoscale. This is especially true where these structures, and hence the material’s properties, are amenable to systematic variation. While such “rational” design approaches often appear both elegant and strait forward on paper, they are much more difficult to execute in practice. Indeed, skilful experimental design, careful attention to experimental details, persistence (often over many person years), and some measure of luck are all typically required for the success of even the most rational of such approaches in the real world. In this paper, work in our research group on two such rational design projects is described. In particular, we are interested in organometallic nanomaterials in which the adjacent metal centres are connected by organic ligands that can act as electronic bridges.
Our most complete work in centred on organometallic nanomaterials in which the metal centres are bridged by arylene ligands. We were only successful in this work after we optimised synthetic strategies and experimental details using model compounds and low molecular weight oligomers. First, we prepared a series of model compounds in which 2-4 metal centres were 6 attached to arenes via s- and/or p-bonds (e.g., 1,4-C6H4(Mn(CO)5)2 and (h -1,3,5-
C6H3(CpFe(CO)2)3)Cr(CO)3). These model compounds were also used to establish the dependence of the intermetallic conjugation upon the geometries and electron richnesses of the bridging arenes and the metal centres. Thus, the 1,4-C6F4 ligand was shown to be amongst the best electronic bridges that have been reported. Next, a series of oligomers having up to 6 or more metal centres (e.g., Ni(PR3)2, PdR3)2, and Pt(PR3)2) joined by fluoroarylenes (e.g., 1,3- and
1,4-C6F4 and 4,4’-(C6F4)2) were prepared. We were able to have full control of the positions of the specific bridging and terminal ligands, the metal centres, and the ancillary ligands in the rigid-rod oligomer backbones. Finally, a series of polymers and copolymers were prepared.
More recently, we have begun work on the synthesis of novel linear and star shaped organometallic nanomaterials having bifunctional isonitriles bridging between adjacent Molybdenum phosphine centres. Our recent progress in this area will be reported.
ADH would like to acknowledge the support of YSU, the National Science Foundation (especially 0111511 and 0128154), and the Petroleum Research Fund (37228) for their support of this work.
IC-03 February 2-6, 2003 Melbourne 200 Molecule Based Magnets; From Large Clusters to Spin-Crossover To Extended Networks
Keith S. Murray School of Chemistry, Monash University, Clayton, Victoria 3800, Australia [email protected]
Modern magnetochemistry is focussing on areas such as paramagnetic metalloenzymes and metalloproteins and their model compounds, molecule-based magnetic materials and nanomagnetic materials. The latter two areas form the basis of this Burrows award lecture. Australian and New Zealand magnetochemists have made major contributions, over many years, to our understanding of ligand-field effects in mononuclear, paramagnetic compounds and magnetic exchange effects in small to medium sized cluster complexes. An exciting growth area in cluster species is the large clusters, mainly of manganese and iron which display unusual quantum effects, the so-called single molecule magnets; SMM’s. These nano-sized molecular materials may have long term applications in data storage. A new Mn16-acetate SMM will be described [1].
A second, key area, which bridges the gap between chemistry, physics and materials science, is that dealing with coordination polymers of d-block ions which display extended network structures of dimensionality 2D or 3D, some having interpenetrated networks [2]. We have studied such compounds which contain the bridging ligands - - - - dicyanamide (N(CN)2 ; dca ) or tricyanomethanide (C(CN)3 ; tcm ) and some recent examples displaying long-range magnetic order will be described [3].
The third sub-topic, one again pioneered in Australia in the 1960’s and 1970’s, and of much current interest because of possible device applications such as molecular switches and memory devices, deals with spin-crossover iron(II) complexes of the polynuclear type. Compared to mononuclear compounds, clusters or polymers of spin-crossover centres, can, in the solid state, yield enhanced cooperativity (memory) properties, multiple crossovers and host-guest (microporosity) interactions. Some examples of the latter microporous type, studied in collaboration with Kepert and his group [4], and, from our laboratory, of a new supramolecular H-bonded dimer type, will be decribed.
Acknowledgements. This work has been supported by Large (Discovery) ARC grants. The author extends his sincere thanks to all members of his present and past groups and to his many collaborators in magnetochemistry.
[1] D. J. Price, S. R. Batten, B. Moubaraki and K. S. Murray, Chem. Comm. 2002, 762. [2] S. R. Batten and K. S. Murray, Austral. J. Chem. 2001, 54, 605. [3] A. M. Kutasi, S. R. Batten, B. Moubaraki and K. S. Murray, J. Chem. Soc. Dalton Trans. 2002, 819. [4] G. J. Halder, C. J. Kepert, B. Moubaraki, K. S. Murray and J. D. Cashion, Science, 2002, in press.
IC-03 February 2-6, 2003 Melbourne 201 X-ray Absorption Spectroscopy in Inorganic Biochemistry Graham N. George,a Hugh H. Harris, a Jürgen Gailer, b and Ingrid J. Pickering a a Stanford Synchrotron Radiation Laboratory, SLAC MS 69, Menlo Park, California 94025, USA. b GSF National Research Center for Environment and Health, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany. [email protected] In recent years, the growing availability of high-intensity synchrotron radiation sources has resulted in a marked increase in the applications of X-ray absorption spectroscopy (XAS) in the chemical sciences. Facilities now exist in many synchrotron radiation laboratories for “turn-key” style operation of XAS experiments. This, together with improvements in data acquisition and analysis software allows novices to the technique to productively conduct experiments and analyse data in a field that was once the domain of specialists. The facilities available at the authors’ laboratory will be reviewed, and the utility of the technique illustrated with examples of applications to Inorganic Biochemistry. Studies of purified metalloproteins and of intact tissues will be discussed, and techniques to be reviewed include both bulk XAS and XAS imaging.
IC-03 February 2-6, 2003 Melbourne 202 X-Ray Microprobe Analysis of the Cellular Uptake and Metabolism of Carcinogenic and Genotoxic Chromium Compounds. Carolyn T. Dillon,a,b Brendan J. Kennedy,b Peter A. Lay,b Barry Lai,c Zhonghou Cai,c Anton P.J. Stampfl,c,d Peter Ilinski,c Daniel G. Legnini,c Jorg Maser,c William Rodrigues,c Grace Shea-McCarthye and Marian Cholewaf a Australian Key Centre for Microscopy and Microanalysis, Electron Microscope Unit, University of Sydney, NSW, 2006, Australia. b School of Chemistry, University of Sydney, NSW, 2006, Australia c Experimental Facilities Division, Argonne National Laboratory, Argonne, IL, 60439, USA d The Bragg Institute, ANSTO, NSW, 2234, Australia. e Brookhaven National Laboratory, Upton, New York. f Institute of Nuclear Physics, 31-342 Krakow, ul. Radzikowskiego 152, Poland. [email protected] Micro-SRIXE (synchrotron induced X-ray emission) and micro-XAS (X-ray absorption spectroscopy) analyses can probe the uptake of exogenous metals by cells. The high flux and the sub-micron resolution of the hard X-ray microprobe allows for highly detailed spatial and structural mapping of cellular elements. The ability of the technique to provide direct imaging of elements offers advantages over the imaging of radioactive- or fluorescent-labelled species as it avoids time-consuming and sometimes hazardous synthetic preparations of the compounds. Similarly, the method avoids artefacts that may arise from altered cell metabolism of the fluorescent labelled compound/drug.
Chromium is a controversial element, in that it exhibits extremely varying biological properties that are highly dictated by its oxidation state. For example, it is well established that Cr(VI) is an occupationally encountered carcinogen, causing cancers of the respiratory tract in workers chronically exposed to high doses of Cr(VI) fumes and dusts. In contrast, Cr(III) compounds are promoted as dietary supplements. Here we present uptake studies performed using micro- SRIXE analyses of whole V79 Chinese hamster lung cells following their exposure to carcinogenic Cr(VI), genotoxic Cr(V), and “relatively safe” Cr(III) complexes [1]. The intracellular Cr distribution, provided by micro-SRIXE mapping of thin-sectioned cells with a 0.3 mm X-ray beam, is also presented. Furthermore, micro-XAS analyses, invaluable for the determination of the ultimate intracellular Cr oxidation state, are presented and these are discussed with reference to the cellular metabolism of Cr(V) and Cr(VI) complexes [2]. Use of the Advanced Photon Source was supported by the U.S. Dept. of Energy, Office of Science, Basic Energy Sciences, under Contract No. W-31-109-Eng-38. Authors also acknowledge ASRP and ARC. ______[1] C.T. Dillon, P.A. Lay, B.J. Kennedy, A.P.J. Stampfl, Z. Cai, P. Ilinski, W. Rodrigues, D.G. Legnini, B. Lai, and J. Maser. J. Biol. Inorg. Chem., 2002, 7, 640-645. [2] C.T. Dillon, P.A. Lay, M. Cholewa, G.J.F. Legge, A.M. Bonin, T.J. Collins, K.L. Kostka, G. Shea-McCarthy, Chem. Res. Toxicol., 1997, 10, 533-535.
IC-03 February 2-6, 2003 Melbourne 203 High Resolution Powder Synchrotron Diffraction Studies of Layered Bismuth Oxides.
Brendan J. Kennedy School of Chemistry, The University of Sydney
Layered Bismuth oxides of the type (Bi2O2)An-1BnO3n+1 where A = Bi, Ca, Sr, Ba or Pb and B = Ti, V, Nb, Ta are an important class of ferroelectric oxides that have been known since the pioneering work of Aurivillius over 50 years ago. Despite early reports of the ferroelectric behaviour in these types of oxides it is only recently that these have been targeted for use in thin-film nonvolatile memory applications. A major barrier to their utilisation is the relatively high temperatures needed to prepare the thin films. Remarkably little is known about the high temperature structures of these types of oxides. In this lecture I will describe the use of high resolution synchrotron diffraction studies of two systems ABi2M2O9 A = Sr, Ba, Pb and M = Nb, Ta and ABi4Ti4O15 A = Ca, Sr, Ba and Pb. In both cases we have sought to establish the nature and extent of the cation disorder and to identify the nature of the high temperature structural phase transitions. Two unique properties of synchrotron radiation have been essential for these studies, namely the wavelength tunabilty has enabled anomalous dispersion methods to be used, and the combination of intensity and resolution that enables data to be rapidly collected.
IC-03 February 2-6, 2003 Melbourne 204 Synthesis and DNA-Binding Properties of Platinum(II) Complexes Containing 1,2- and 1,7-Dicarba-closo-dodecaborane(12)
Jean A. Todd, Susan L. Woodhouse and Louis M. Rendina Department of Chemistry, The University of Adelaide, 5005 SA, Australia.
[email protected] Boron Neutron Capture Therapy (BNCT) is a bimodal cancer treatment that is currently undergoing Phase I clinical trials in several countries, including the US, Sweden, Japan and Finland [1]. The key aspect of the therapy is the interaction of slow (thermal) neutrons with 10B- containing drugs that are localised within malignant cells. The resulting nuclear reactions ultimately lead to cell destruction due to the production of high linear energy transfer (LET) particles that are accompanied by approximately 2.4 MeV of kinetic energy. The effectiveness of the neutron capture reaction is dramatically enhanced if the 10B-containing compounds are placed in close proximity to chromosomal DNA, and the search for new DNA-binding agents for BNCT remains a major research objective.
The ability of DNA to act as Cl a template for the organised H3N Pt Cl binding of cisplatin, metallo- NH2 intercalators and other types H + of metal complexes allows N C one to examine whether S Pt N BH N platinum compounds that are NH3 tethered to polyhedral 1 H2N Pt Cl 2 boranes such as the dicarba- Cl closo-dodecaboranes(12) (carboranes) can target the macromolecule for potential use in BNCT. A number of key results have been obtained in our laboratory regarding the preparation and DNA-binding properties of both mono- and di-nuclear platinum(II) complexes that are tethered to a 1,2- and 1,7-dicarba-closo-dodecaborane(12) moiety, respectively [2, 3]. For example, we have demonstrated that complexes 1 and 2 exhibit avid DNA-binding characteristics in vitro. This is the first time that metal complexes containing boron-containing ligands have been shown to target DNA. The key results of this work will be presented.
[1] A. H. Soloway, W. Tjarks, B. A. Barnum, F. -G. Rong, R. F. Barth, I. M. Codogni, and J. G. Wilson, Chem. Rev., 1998, 98, 1515.
[2] J. A. Todd and L. M. Rendina, Inorg. Chem., 2002, 41, 3331.
[3] S. L. Woodhouse and L. M. Rendina, Chem. Commun., 2001, 2464.
IC-03 February 2-6, 2003 Melbourne 205 Developing Pt(IV) Anticancer Drugs Resistant to Reduction via Ligand Chelation Murray S. Davies,a Andrew R. Battlea and Trevor W. Hambleyb a School of Pharmacy and Molecular Sciences, James Cook University, Townsville, QLD 4811, Australia b School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia mailto:[email protected] The development of Platinum(IV) complexes as antitumour agents stems from their kinetic inertness relative to their platinum(II) counterparts. Drug toxicities (particularly to the kidneys) and the amount of the drug lost or deactivated are lowered because Pt(IV) compounds undergo fewer reactions with substrates other than the target DNA within the biological milieu. A further benefit is that Pt(IV) compounds potentially offer oral rather than intravenous administration.
One aim of this work is the development of Pt(IV) complexes that are resistant to reduction in vivo, by stabilising the octahedral geometry of Pt(IV) through selection of appropriate multidentate chelate ligands. The approach has been the coordination of “flexidentate” ligands that bind to Pt(II) in a bidentate manner, but bind to Pt(IV) in a tri- or tetradentate fashion. A subset of these ligands, specifically “octahedral enforcer ligands”; IV + Figure 1. ORTEP plots of [Pt Cl3([9]aneN3)] and have been shown to promote facile aerial II + [Pt Cl2([9]aneN3H)] oxidation of Pt(II) to Pt(IV). This term describes tridentate ligands that coordinate exclusively in a facial orientation, (e.g. 1,4,7- triazacyclononane (shown bound to Pt(II) and Pt(IV) in Figure 1)) [1,2].
This paper outlines the preparation, structural characterisation and electrochemical behaviour of some of these Pt(II) and Pt(IV) complexes. The oxidation mechanism is examined and initial binding studies are described.
[1] M. S. Davies and T. W. Hambley, Inorg. Chem. 1998, 37, 5408-5409.
[2] M. S. Davies, R. R. Fenton, F. Huq, E. C. H. Ling and T. W. Hambley, Aust. J. Chem., 2000, 53, 451-456.
IC-03 February 2-6, 2003 Melbourne 206 Dinuclear Ruthenium Complexes as Sequence- and Structure-Selective Binding Agents for DNA
J. Grant Collins,a Fiona M. Foley, b F. Richard Keene,b Bradley T. Patterson,b and Dean Richardsb a School of Chemistry, University College, Australian Defence Force Academy, University of New South Wales, Canberra, A.C.T. 2600 b School of Pharmacy & Molecular Sciences, James Cook University, Townsville, Queensland 4811
[email protected] There has been considerable interest in the interactions of inert transition metal complexes with nucleic acids: to investigate the principles involved in DNA and RNA recognition and the tertiary structure of nucleic acids; to act as artificial nucleases and luminescent probes for DNA; and to examine electron transfer mediated by DNA. These studies have primarily centred on a range of mononuclear complexes of ruthenium(II) and rhodium(III) because they are positively charged, inert, water soluble and contain spectroscopically-active metal centres. Further, tris(bidentate) octahedral complexes possess chirality (D or L), and discrimination between these forms has been observed, with the D-enantiomer generally having a greater affinity for B-type DNA.
However, the use of mononuclear metal complexes as probes for DNA recognition is limited by their relatively small size as they can only span four DNA bases, whereas recognition of at least 8-10 bases is required if the metal complex is to have the selectivity of a DNA binding protein for a particular gene. By contrast, dinuclear complexes will not only have an increased size but also a greater variety of shapes, greater DNA binding affinity and considerably slower DNA-dissociation rates, which are extremely advantageous in NMR studies of the DNA binding by the metal complexes.
IC-03 February 2-6, 2003 Melbourne 207 New insight into the stepwise formation of platinum-DNA crosslinks from [1H,15N] NMR spectroscopy Susan J. Berners-Price,a Murray S. Davies,a Donald S. Thomas,a Alexander Hegmans,b John W. Coxb and Nicholas Farrellb a Chemistry, School of Biomedical & Chemical Sciences, University of Western Australia, 6009, Western Australia. b Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia, USA [email protected] [1H,15N] HSQC NMR has proved to be a powerful technique for following DNA platination reactions by platinum anticancer drugs. Initial studies focussed on cisplatin (and related mononuclear analogs) where 15N-labelled derivatives are readily synthesised. More recently, we have applied the technique to compare and contrast the DNA binding of the Phase II trinuclear Pt 4+ complex [(trans-PtCl(NH3)2)2{m-trans-Pt(NH3)2(NH2(CH2)6NH2)2}] , (1,0,1/t,t,t (n=6) or 15 BBR3464) with a prototypical dinuclear compound [{trans-PtCl( NH3)2}2(m- 15 15 2+ NH2(CH2)6 NH2)] (1,1/t,t n=6). The two compounds have the same profile of preclinical antitumour activity but BBR3464 is active at 10-fold lower concentration than either 1,1/t,t or 15 15 cisplatin. For these di- and tri-nuclear compounds labelling of both NH2 and NH3 groups is possible allowing DNA platination reactions to be followed independently in the two regions of 1 15 15 the [H, N] NMR spectra. For BB3464 N-labelling of the central PtN4 linker provides additional information on H-bonding interactions of this group with the DNA.
This talk will focus on the new information obtained from some of our recent [1H,15N] NMR studies, in particular (i) a comparison of the kinetics and mechanism of formation of 1,4-GG and 1,6-GG interstrand cross-links by 15N-BBR3464 and (ii) a competitive study of the preferential formation by 1,1/t,t of a 1,4-interstrand crosslink rather than a 1,2-intrastrand crosslink on binding to a GG 14-mer duplex [1]. In the first case, comparison with our earlier [1H, 15N] NMR study of the formation of the 1,4-GG crosslink by the 1,1/t,t compound [2] reveal that the central
PtN4 linker does not influence the overall rate of formation of long-range interstrand cross-links. However, it does influence the nature and extent of the pre-covalent binding association with the DNA. The latter may dictate not only which cross-links are preferred, but also determine the conformations of the bifunctional adducts. In the second example, our studies also provide insight into the basis for more rapid binding of di- and tri-nuclear Pt complexes to single stranded DNA and RNA. Reaction of 1,1/t,t with 5´-d(ATACATG(7)G(8)TACATA)-3´ and the duplex formed with its complementary strand 5´-d(TATG(25)TACCATG(18)TAT)-3´ showed that there is a retardation of the rate of chloride aquation in the presence of the duplex [3].
[1] S. J. Berners-Price, M. S. Davies, J. W. Cox, D. S. Thomas, and N. Farrell, Chem. - Eur. J. 2003, in press. [2] J. W. Cox, S. J. Berners-Price, M. S. Davies, Y. Qu and N. Farrell, J. Am. Chem. Soc., 2001, 123, 1316. [3] M. S. Davies, S. J. Berners-Price, J. W. Cox, N. Farrell, Chem. Commun, 2003, in press.
IC-03 February 2-6, 2003 Melbourne 208 Structure and Exchange in Photo-Generated, Short-Lived Alkane Complexes Graham E. Ball, Spili Geftakis, Douglas J. Lawes and Tamim Darwish NMR Facility and School of Chemical Sciences, University of New South Wales, Sydney 2052, Australia [email protected] We have been studying the binding of alkanes to transition metal centres using NMR. Alkane complexes are of interest both from a fundamental standpoint and because they are intermediates in the so-called C-H activation reaction which is a possible route to the functionalization of these rather unreactive molecules. Owing to the very poor nature of alkanes as ligands, such alkane complexes are extremely unstable and have only fleeting existences even at low temperatures. Consequently, the observation of alkane complexes has until relatively recently only been by “fast” methods such as U.V. and I.R. spectroscopy.
Our initial experiment was the in situ photolysis within the NMR spectrometer at 183 K of a sample of CpRe(CO)3 in cyclopentane that led to the generation of the first alkane complex seen 1 using NMR, CpRe(CO)2(cyclopentane). :
More recently we have characterized complexes with a wide range of alkanes formed in the spectrometer down to temperatures as low as 123 K.
This presentation will focus on NMR techniques used to characterise these alkane complexes, the exchange processes that they undergo and recent results in the area. The NMR experiments include homo- and heteronuclear experiments on isotopically labelled (2H, 13C) alkane complexes and 2D EXSY type experiments The experimental demands of acquiring 2D spectra of short-lived, low concentration products in perprotio solvents with multiple proton resonances at low temperatures under photolysis will be discussed. Investigations of exchange processes occurring in the alkanes attached to the CpRe(CO)2 fragment have shown that intramolecular mechanisms involving a change of the coordinated hydrogen and also carbon occur significantly faster than processes involving dissociation of the alkane. Results of looking at photo-generated fragments such as Cp*Re(CO)(PMe3) which are known to break the C-H bonds present in alkanes will also be discussed, as will our attempts at observing alkane complexes of other metals.
[1] S. Geftakis and G.E. Ball, J. Am. Chem. Soc. 1998, 120, 9953.
IC-03 February 2-6, 2003 Melbourne 209 Mechanistic Insight gained from Volume Profile Analysis
Rudi van Eldik
Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstr. 1, 91058 Erlangen, Germany [email protected]
Insight into the mechanisms of chemical reactions in solution, in many cases depends to a large extent on rate and activation parameters that can be determined for individual reactions steps. In this respect, kineticists have many chemical but only two physical variables, viz. temperature and pressure, at their disposal. The temperature dependence of the reaction allows the estimation of the activation enthalpy and activation entropy, where the latter parameter is often used to support the intimate nature of a suggested reaction mechanism. Activation entropies are in general subjected to large error limits as a result of the inherently required extrapolation to 1/T = 0. Over the past two to three decades, inorganic kineticists have studied the effect of pressure on many chemical reactions in solution, from which information on volume changes associated with the formation of the transition state can be obtained. From such data it is in some cases possible to construct volume profiles that can provide important mechanistic information not obtainable from other kinetic parameters.[1] Some of the earliest work in this area was performed by Don Stranks and co-workers in the early seventies, and has stimulated much work in this area.[2]
We have applied volume profile analysis to a wide range of chemical processes that include thermal, photo-induced and radiation-induced reactions, dealing with ligand substitution, electron transfer, activation of small molecules and oxidative addition/reductive elimination processes.[1,3,4] A selection of typical examples from our most recent published [5] and unpublished studies will be used to demonstrate the type of mechanistic information that can be obtained from volume profile analysis. These studies include the application of conventional, stopped-flow, flash-photolysis and pulse-radiolysis kinetic techniques, as well as sprectroscopic and electrochemical measurements as a function of pressure.
[1] R. van Eldik, C. Dücker-Benfer, and F. Thaler, Adv. Inorg. Chem., 2000, 49, 1. [2] D.R. Stranks, Pure Appl. Chem., 1974, 38, 303. [3] P.C. Ford and L.E. Laverman, in High Pressure Chemistry, R. van Eldik and F.-G. Klärner (Eds.), 2002, Chapter 6. [4] R. van Eldik and D. Meyerstein, Acc. Chem. Res., 2000, 33, 207. [5] R. van Eldik and coworkers: J. Am. Chem. Soc., 2001, 123, 285; J. Am. Chem. Soc., 2001, 123, 9780; Inorg. Chem., 2002, 41, 4; Inorg. Chem., 2002, 41, 1579; Inorg. Chem., 2002, 41, 2565; Inorg. Chem., 2002, 41, 2808; Inorg. Chem., 2002, 41, 3802; Inorg. Chem., 2002, 41, 5417.
IC-03 February 2-6, 2003 Melbourne 210 Using DFT to Design Metal Complexes which Optimize the Activation and Cleavage of Small Multiply-Bonded Molecules Gemma Christian,a Jenni Driver,a Simon Petriea and Robert Strangera a Department of Chemistry, Australian National University, 0200, ACT, Australia [email protected] Dinuclear metal systems based on sterically-hindered, three-coordinate transition metal
complexes of the type (RnX)3M where the RnX are ancillary ligands and R is a bulky organic substituent, hold great promise synthetically for the activation and cleavage of small, multiply-
bonded molecules, L1ºL2.[1,2]
X'Rn XRn RnX X'Rn L1 L2 M M L1 L2 M' M'(X'Rn)3 RnX R X X'Rn n R X XRn n three-coordinate small-molecule bridged metal complex dinuclear metal complex
X'Rn RnX X'Rn
M L1 + L2 M'
RnX X'Rn RnX
We have employed density functional methods to design three-coordinate transition metal
complexes that are specific for the activation of N2 and other key small molecules such as NO and CO. Through judicious tuning of M, M', X and X', it is possible to identify those metal/ligand combinations which achieve optimum activation of each small molecule of interest. In particular, the extent of small molecule activation is very sensitive to the dn configuration of
the metal. For example, whereas the reaction of Mo(NH2)3 with NO is predicted to be 3 3 unfavourable for cleavage of NO due to the instability of the dinuclear d d complex (H2N)3Mo-
NO-Mo(NH2)3, the reaction of Mo(NH2)3 and V(NH2)3 with NO results in the formation of a 3 2 stable d d dimer intermediate, (H2N)3Mo-NO-V(NH2)3, with a low activation barrier to NO cleavage.
[1] C.E. Laplaza, A.L. Odom, W.M. Davis, and C.C. Cummins, J. Am. Chem. Soc., 1995, 117, 4999. [2] C.E. Laplaza, M.J. Johnson, J.C. Peters, A.L. Odom, E. Kim, C.C. Cummins, G.N. George, and I.J. Pickering, J. Am. Chem. Soc., 1996, 118, 8623.
IC-03 February 2-6, 2003 Melbourne 211 Fluorescence of the Intracellular Zinc(II) Probe Zinquin A in Ternary Zinc(II) Complexes
Kym M. Hendrickson, Jason P. Geue, Oska Wyness, Stephen F. Lincoln and A. David Ward Department of Chemistry, The University of Adelaide, Adelaide, SA 5000, Australia. stephen [email protected]
Zinc(II) is widespread in biology and there is much interest in its detection in vivo. Accordingly, 2+ we developed the Zn specific fluorophore [2-methyl-8-(4-toluenesulfon-amido)-6-quinolyl- 1 oxy]acetic acid, Zinquin A, LH2, and its ethyl ester, Zinquin E, both of which fluoresce strongly when coordinated by Zn2+ and have been widely used in intracellular studies [1] (Figure 1). Most intracellular Zn2= is bound by proteins and other ligands with little if any existing in the fully hydrated state. As all reported studies of intracellular Zn2+ using Zinquin A and E show fluorescence consistent with their coordination by Zn2+, it is probable that fluorescent ternary Zn2+ complexes are formed where 1L2- is one of the ligands. Therefore, it is of interest to establish the extent to which 1L2- coordinates Zn2+ in ternary complexes and its fluorescence is modified by the presence of other ligands. Thus, we have studied the formation of ternary Zn2+ complexes of 1L2- and several well-characterized multidentate ligands by potentiometric, uv- visible absorbance and fluorescence methods. The fluorescence quantum yields vary significantly as the 1L2- coordination environment changes in the ternary complex. Thus, a significant proportion of the fluorescence of 1L2- observed in intracellular studies probably arises from 1L2- in ternary complexes formed by Zn2+ with proteins and other ligands. This proportion will vary with the ability of 1L2- to compete for coordination sites and raises the possibility that different Zn2+ probes may detect different ensembles of Zn2+ complexes in intracellular studies [2].
HO2CCH2O O2CCH2O 0
N CH3 N CH3 H NH N N Zn NH SO2 SO 2 HN NH
1 LH2 CH3 358 nm CH3 484 nm
1 Figure 1. [2-methyl-8-(4-toluenesulfonamido)-6-quinolyloxy]acetic acid, Zinquin A, LH2 and one of its ternary Zn2+ complexes.
[1] K. M. Hendrickson et al, J. Chem. Soc., Dalton Trans., 1997, 3879. [2] K. M. Hendrickson, J. P. Geue, O. Wyness, S. F. Lincoln and A. D. Ward, J. Am. Chem. Soc., accepted for publication.
IC-03 February 2-6, 2003 Melbourne 212 Chromium Schiff base complexes in olefin polymerization catalysis: synthesis of a ligand and metal complex library for high throughput screening David Jonesa, Vernon C. Gibsona, Simon M. Greenb, Peter J. Maddoxb a Department of Chemistry, Imperial College, South Kensington, London, United Kingdom b Chemicals Stream, BP, Chertsey Road, Sunbury on Thames, Middlesex, United Kingdom [email protected] High Throughput Screening (HTS) is rapidly becoming established as an important tool for the discovery of ‘step-out’ classes of olefin polymerization catalysts. In recent years we have been interested in the development of highly active chromium catalysts bearing readily available Schiff base ligands. Following our discovery that salicylaldimines bearing bulky -ortho- phenoxy substitutents and small imine substituents give very active catalysts for ethylene polymerisation (Scheme 1) we have used HTS to facilitate the further discovery of exceptionally active catalsysts based on tridentate salicylaldimiine ligands with bulky triptycenyl groups.1 In this presentation we shall outline the initial discovery, synthesis of the required salicylaldehydes (Figure 1), ligand library development and HTS results which have led to the discovery of highly active chromium catalysts supported by bi- and tri-dentate Schiff base ligands (Figure 2). Ligand variation, complex formation and polymerisation results will also be discussed.
2 N R 2 OH R N R1 MAO CrCl2(thf)n tolylCrCl2(thf) 3 PE -toluene O
R1 R1 = Anthracenyl, R2 = iPr
Scheme 1. Ligand screening process for initial catalyst discovery and HTS program.
O O O O OH OH OH CF3 OH
Figure 1. Salicylaldehyde backbones synthesised for ligand library generation.
R N N N CrCl (thf) 2 n CrCl2(thf)n O O
Bulky I Bulky II
Figure 2. Bidentate and tridentate Schiff’s base complexes of chromium as precatalysts for ethylene polymerisation.
1 D.J. Jones, V.C. Gibson, S.M. Green and P.J. Maddox Chem. Comm., 2002, 10, 1038-1039.
IC-03 February 2-6, 2003 Melbourne 213
New Catalysts and Tandem Reactions: Synthesising Products with C-X bonds S. Burling,b L. D. Field,b B. A. Messerle,a S. Wren,a and K. Vuong a a School of Chemical Sciences, The University of New South Wales, Sydney, 2052,NSW Australia. b School of Chemistry, University of Sydney, Sydney, 2006, NSW, Australia. [email protected]
The transition metal catalysed addition of heteroatoms to unsaturated C-C bonds is an important route to the formation of new carbon-heteroatom bonds. Catalysed hydroamination, hydrophosphination and hydrothiolation reactions lead to the formation of C-N, C-P and C-S bonds, respectively, in a highly atom efficient approach. Cationic complexes of iridium(I) and + rhodium(I) of the form [M(NN) (CO)2] (1, NN = bis-imidazolylmethane or bis- pyrazolylmethane) are effective as catalysts for the synthesis of a number of pyrrolines via the hydroamination of alkynylamines (eg. Scheme 1a) [1]. The iridium complexes also promote tandem reactions, where the hydroamination reaction is followed by a hydrosilation reaction, leading to the synthesis of pyrrolidines (Scheme 1a and 1b).
SiEt3 H C H2N N [Ir] 3 N [Ir] H3C C C* o HSiEt3 H thf-d8, 60 C o H C C thf-d8, 60 C (a) (b) Scheme 1 The search for new catalysts for the formation of C-X bonds has involved developing approaches to the synthesis of a series of complexes containing mixed bidentate ligands, with a variety of donor atoms including sp2-nitrogen, phosphine and carbene donors eg. Ph X Ph Ph 2, 3. As catalysts for the hydrothiolation reaction, metal complexes P P Ph with ligands containing mixed phosphine and nitrogen donors yield 2 N N 3 N different products to those resulting from the use of complexes (1) N containing bidentate N-donor ligands (NN).
[1] a) S. Burling, L.D. Field, B.A. Messerle, Organometallics, 2000, 19, 87; b) S. Burling, Ph.D Thesis, 2001, The University of Sydney
IC-03 February 2-6, 2003 Melbourne IC-03 Delegate List
Name Institution Email address Abstract No(s)
Abrahams, Brendan Dr University of Melbourne [email protected] 03, 105 Adams, Joanne Ms Australian National University [email protected] 04, 157 Ainscough, Eric A/Professor Massey University [email protected] 05 Akhlaghi, Hassan Mr University of Melbourne [email protected] Alderden, Rebecca Ms University of Sydney [email protected] Aldrich-Wright, Janice Dr University of Western Sydney [email protected] Alexander, Mark Mr University of Sydney [email protected] 06 Andrews, Phil Dr Monash University [email protected] 44 Antill, Sarah Dr University of Sydney [email protected] 07 Appleton, Trevor A/Professor University of Queensland [email protected] 08 Bailey, Trevor Dr University of Western Sydney [email protected] Ball, Graham Dr University of New South Wales [email protected] 208 Banci, Lucia Professor University of Florence [email protected] 116 Batten, Stuart Dr Monash University [email protected] 103 Beckmann, Udo Dr University of Otago [email protected] 164 Behrsing, Thomas Mr Monash University [email protected] 58, 113 Berners-Price, Sue Professor University of Western Australia [email protected] 166, 207 Bernhardt, Paul Dr University of Queensland [email protected] 55 Berven, Bradley Mr University of Western Australia [email protected] Best, Stephen Dr University of Melbourne [email protected] 09 Beves, Jonathon Mr University of Sydney [email protected] Bevitt, Joseph Mr University of Sydney [email protected] 167 Black, Jay Mr Monash University [email protected] 60 Blackman, Allan Dr University of Otago [email protected] 10 Bond, Alan Professor Monash University [email protected] Bondin, Mark Mr University of Melbourne [email protected] 168 Borg, Stacey Mr University of Melbourne [email protected] 11 Boyd, Peter A/Professor University of Auckland [email protected] 112 Boyd, Simon Mr University of Melbourne [email protected] Bradbury, Adam Mr Flinders University [email protected] 12 Brodie, Andrew Professor Massey University [email protected] Brodie, Craig Mr University of Western Sydney [email protected] 61 Brooker, Sally A/Professor University of Otago [email protected] 13 Brown, Tiffany Ms Monash University [email protected] 62 Bulluss, Genevieve Ms University of Sydney [email protected] 63 Canty, Allan Professor University of Tasmania [email protected] 51 Caradoc-Davies, Paula Dr University of Otago [email protected] 169 Cavell, Kingsley Professor Cardiff University [email protected] 53 Chang, John Mr University of Auckland [email protected] 64 Chapman, Karena Ms University of Sydney [email protected] 170 Codd, Rachel Dr University of Sydney [email protected] 115 Colbran, Stephen Dr University of New South Wales [email protected] 50 Cole, Marcus Dr Monash University [email protected] 65, 117 Collins, Grant Dr Australian Defence Force [email protected] Academy Collins, Terrence J. Professor Carnegie Mellon University [email protected] 101 Constable, Edwin C. Professor University of Basel [email protected] 57 Cordes, David Mr University of Otago [email protected] 92 Cregan, Andrew Mr Australian National University [email protected] 118 Curnow, Owen Dr University of Canterbury [email protected] 67 D'Alessandro, Deanna Ms James Cook University [email protected] 14, 158 Damsyik, Akhmad Mr Flinders University [email protected] 15 Darwish, Tamim Mr University of New South Wales [email protected] 119 Davies, Murray Dr James Cook University [email protected] 205 Deacon, Glen Professor Monash University [email protected] 68 Denney, Melanie Mrs University of Tasmania [email protected] 97, 98 Derwahl, Andreas Dr Massey University [email protected] 16 Dewhurst, Rian Mr Australian National University [email protected] 70 Dillon, Carolyn Dr University of Sydney [email protected] 120, 202 Dinev, Zoran Mr University of Melbourne [email protected] Doonan, Christian Mr University of Melbourne [email protected] 17 Drago, Penny Mrs Monash University [email protected] 121, 122 Duriska, Martin Mr Monash University [email protected] 123 Evans, David Mr Monash University [email protected] 18, 171 Failes, Timothy Dr University of Sydney [email protected] 19 Fang, Bin Mr University of Sydney [email protected] 71 Farrell, Nicholas Professor Virginia Commonwealth [email protected] 163 University Fern, Glen Mr University of Canterbury [email protected] 20 Fester, Victor Mr University of Waikato [email protected] 21 Fisher, Dianne Mrs University of Sydney [email protected] 22 Fry, Fiona Dr Australian National University [email protected] 23 Fujita, Makoto Professor University of Tokyo [email protected] 01 Gahan, Lawrence A/Professor University of Queensland [email protected] Gardiner, Michael Dr University of Tasmania [email protected] 46 Gasperov, Vesna Ms University of Sydney [email protected] 172 George, Graham Dr Stanford University [email protected] 201 Goh, Lai Yoong Dr National University of [email protected] 24 Singapore Grace, Mike Dr Monash University [email protected] 114 Green, Malcolm Mr University of Sydney [email protected] 124 Halder, Gregory Mr University of Sydney [email protected] 25, 159 Hall, Matt Mr University of Sydney [email protected] 26 Hambley, Trevor Professor University of Sydney [email protected] Hanson, Graeme A/Professor University of Queensland [email protected] 56 Hanton, Lyall Dr University of Otago [email protected] 104 Hardie, Michaele Dr University of Leeds [email protected] 111 Harika, Rita Ms Monash University [email protected] 27, 28 Harris, Hugh Dr Stanford Synchrotron Radiation [email protected] 125 Laboratory Hausmann, Julia Ms University of Otago [email protected] 29 Helmstedt, Ulrike Ms University of Leipzig [email protected] Hey-Hawkins, Evamarie Professor Universität Leipzig [email protected] 02 Hilder, Matthias Mr Monash University [email protected] 165, 173 Hill, Anthony Professor Australian National University [email protected] 43 Hill, Lyndal Ms University of Melbourne [email protected] 126, 197 Hitzbleck, Julia Ms Syracuse University [email protected] 30 Hocking, Rosalie Ms University of Sydney [email protected] 127 Hodgson, Michael Dr University of Auckland [email protected] 31 Hoshikawa, Kazuyuki Mr University of Sydney Hosseini, Ali Mr University of Auckland [email protected] 174 Howard, Warren Mr University of Western Sydney [email protected] 72 Howell, Sarah Ms University of Otago [email protected] 73, 160 Hudson, Tim Mr University of Melbourne [email protected] 175 Hughes, Suzanne Mrs University of Sydney [email protected] 176 Humphrey, Elizabeth Dr Australian National University [email protected] 74 Humphrey, Mark Dr Australian National University [email protected] 32 Hunter, Allen Professor Youngstown State University [email protected] 199 Huth, Stefan Mr Monash University [email protected] Jackson, Greg Professor University of New South Wales [email protected] 177 Jameson, Geoffrey Professor Massey University [email protected] 47 Jaramillo, David Mr University of Western Sydney [email protected] 75 Ji, Xue Kui Ms University of New South Wales [email protected] 76 Jones, David Dr Imperial College London [email protected] 212 Junk, Peter Dr Monash University [email protected] 77 Kam, Cindy Ms University of Western Sydney [email protected] 128 Keene, Richard Professor James Cook University [email protected] 206 Kennedy, Brendan Dr University of Sydney [email protected] 203 Kennedy, Steven Dr University of Auckland [email protected] 78 Kepert, Cameron Dr University of Sydney [email protected] 102 Kirk, Martin Professor University of New Mexico [email protected] 54 Kitto, Heather Ms Australian National University [email protected] 33 Klingele, Marco Mr University of Otago [email protected] 79 Klooster, Wim Dr Australian Nuclear Science & [email protected] 129 Technology Organisation Knottenbelt, Sushilla Ms University of York [email protected] 100 Koay, Melissa Ms University of Melbourne [email protected] 34 Konstas, Kristina Ms Monash University [email protected] 80 Koutsantonis, George Dr University of Western Australia [email protected] 59, 109 Kreher, Ute Mrs Monash University [email protected] Krenske, Elizabeth Ms Australian National University [email protected] 82 Kutasi, Anna Ms Monash University [email protected] 35 Lan, Yanhua Ms University of Otago [email protected] 83 Larkins, Frank Professor University of Melbourne [email protected] Lawes, Douglas Mr University of New South Wales [email protected] 84 Lay, Peter Professor University of Sydney [email protected] Leary, Stuart Mr Monash University [email protected] Levina, Aviva Dr University of Sydney [email protected] 130 Lewis, William Mr University of Canterbury [email protected] 131 Lincoln, Stephen Professor University of Adelaide [email protected] 132, 211 Lindoy, Leonard Professor University of Sydney [email protected] 36 Liu, Xiaoyu Ms University of New South Wales [email protected] 85 Lock, Julia Ms University of Adelaide [email protected] 37 Lu, Leon Guo-Liang Dr University of Auckland [email protected] 86 Mace, Wade Mr University of Waikato [email protected] 87 Macpherson, Brendan Mr University of Queensland [email protected] 133 Malarek, Michael Mr University of Melbourne [email protected] 172, 178 Mariotti, Andrew Mr University of Melbourne [email protected] 88 Marken, Frank Dr Loughborough University [email protected] 134, 135 Masters, Tony A/Professor University of Sydney [email protected] 136 McAdam, John Mr University of Otago [email protected] 179 McFadyen, David A/Professor University of Melbourne [email protected] 38, 89 McKenzie, Christine Dr University of Southern Denmark [email protected] 49 Messerle, Barbara Dr University of New South Wales [email protected] 213 Micallef, Leanne Ms Griffith University [email protected] 137 Mitchell, Cassandra Ms Deakin University [email protected] 198 Moniodis, Joe Mr University of Western Australia [email protected] 99 Moore, Evan Mr University of Queensland [email protected] 90 Morgan, Joy Ms University of Otago [email protected] 138 Moubaraki, Boujemaa Dr Monash University [email protected] 91 Moylan, Michael Mr University of Melbourne [email protected] 139 Mueller-Westerhoff, Ulrich Dr University of Connecticut [email protected] 52 Mulyana, Yanyan Mr University of Sydney [email protected] 66 Murray, Keith Professor Monash University [email protected] 200 Nealon, Gareth Mr University of Western Australia [email protected] 181 Nielsen, David Mr University of Tasmania [email protected] 140 Osvath, Peter Dr Commonwealth Scientific & [email protected] Industrial Research Organisation Pearson, Pauline Ms Monash University [email protected] 182 Peberdy, Jemma Ms University of Warwick [email protected] 183 Pickett, Chris Dr John Innes Centre [email protected] 48 Plush, Sally Ms University of Adelaide [email protected] 141 Price, David Mr Monash University [email protected] 39 Price, Jason Mr University of Sydney [email protected] 93 Ralph, Stephen Dr University of Wollongong [email protected] 108 Rauchfuss, Thomas B. Professor University of Illinois [email protected] 42 Rendina, Louis Dr University of Adelaide [email protected] 204 Robinson, Brian Professor University of Otago [email protected] 40 Robson, Richard Dr University of Melbourne [email protected] Rodemann, Thomas Dr University of Tasmania [email protected] 142 Ruhlandt-Senge, Karin Professor Syracuse University [email protected] 45 Schatz, Markus Dr University of Melbourne [email protected] 143 Schultz, Madeleine Dr Australian National University [email protected] 144 Simpson, Jim Professor University of Otago [email protected] 145 Skelton, Brian Dr University of Western Australia [email protected] Smith, Naomi Ms Deakin University [email protected] 180 Spiccia, Leone Dr Monash University [email protected] 106 Sproules, Stephen Mr University of Melbourne [email protected] 146 Steel, Peter Professor University of Canterbury [email protected] 110 Stranger, Robert Dr Australian National University [email protected] 210 Sumby, Christopher Mr University of Canterbury [email protected] 94, 161 Swiegers, Gerhard Dr Commonwealth Scientific & [email protected] 95, 147 Industrial Research Organisation Tasker, Peter Dr University of Edinburgh [email protected] 107 Thiyakesan, Appadurai Mr University of Sydney [email protected] 148 Tolhurst, Vicki-Anne Dr University of Tasmania [email protected] 149, 184, 185 Tong, Andrew Mr University of Sydney [email protected] 96 Tregloan, Peter A/Professor University of Melbourne [email protected] 186 Tshabang, Never Mr Australian National University [email protected] 187 Usher, Alistair Mr Australian National University [email protected] 188 van der Werff, Patricia Ms Monash University [email protected] 150 van Eldik, Rudi Dr Universitat Erlangen [email protected] 209 Vuong, Khuong Mr University of New South Wales [email protected] 189 Wainwright, Kevin A/Professor Flinders University [email protected] Wang, Jun Dr Tasmania University [email protected] 191 Warden, Andrew Mr Monash University [email protected] 151 Warr, Rebecca Ms Australian National University [email protected] 192 Waters, Tom Mr University of Melbourne [email protected] 69, 162 Weatherburn, David Dr Victoria University of Wellington [email protected] 193 Wedd, Tony Professor University of Melbourne [email protected] Weder, Jane Dr National Industrial Notification [email protected] & Assessment Scheme Weeks, Colin Dr University of Sydney [email protected] 152 Wells, Kerrina Ms University of New South Wales [email protected] West, Bruce Professor Monash University [email protected] Whan, Renee Ms University of Sydney [email protected] 194 Wild, Stanley Bruce Professor Australian National University [email protected] Wimmer, Franz Dr Universiti Brunei Darussalam [email protected] 41 Wise, Lauren Ms University of Tasmania [email protected] 153 Wittick, Lisa Ms Monash University [email protected] 195 Wren, Sarah Ms University of New South Wales [email protected] 154 Wright, L. James A/Professor University of Auckland [email protected] 196 Xiao, Zhiguang Dr University of Melbourne [email protected] 155 Young, Charles A/Professor University of Melbourne [email protected] 156