DOCSLIB.ORG

Answers to Exercises References Abbreviations

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Answers to Exercises References Abbreviations ANSWERS TO EXERCISES REFERENCES ABBREVIATIONS INDEX ATOMIC WEIGHTS OF THE ELEMENTS PERIODIC TABLE OF THE ELEMENTS ANSWERS TO EXERCISES CHAPTER 1 + + 1.1. [FeCp2] , sandwich structure with parallel rings, [FeL4X2] , 17, 5, 3, 6; [RhCl(PPh3)3], square planar, [RhL3X], 16, 8, 1, 4; [Ta(CH2CMe3)3(CHCMe3)], tetrahedral, [TaX5], 10, 0, 5, 4; [ScCp*2(CH3)], bent sandwich with CH3 in the equatorial plane, [ScL4X3], 14, 0, 3, 7; [HfCp2Cl2], bent sandwich with both Cl ligands in the equatorial plane, [HfL4X4], 16, 0, 4, 8; – – [W(H)(CO)5] , octahedral, [WL5X] , 18, 6, 0, 6; 2 2+ 2+ [Os(NH3)5( -C6H6)] , octahedral, [OsL6] , 18, 6, 2, 6; [Ir(CO)(PPh3)2(Cl)], square planar, [IrL3X], 16, 8, 1, 4; [ReCp(O)3], pseudo-octahedral, [ReL2X7], 18, 0, 7, 6; 2– 2– [PtCl4] , square planar, [PtX4] , 16, 8, 2, 4; – – [PtCl3(C2H4)] , square planar, [PtLX3] , 16, 8, 2, 4; [CoCp2], sandwich structure with parallel rings, [CoL4X2], 19, 7, 2, 6; 6 [Fe( -C6Me6)2], sandwich structure with parallel rings, [FeL6], 20, 8, 0, 6; [AuCl(PPh3)], linear, [AuLX], 14, 10, 1, 2; 4 [Fe( -C8H8)(CO)3], trigonal bipyramid (piano stool), [FeL5], 18, 8, 0, 5; 1 2+ 2+ [Ru(NH3)5( -C5H5N)] , octahedral, [RuL6] , 18, 6, 2, 6; 2 + + [Re(CO)4( -phen)] , octahedral, [(ReL6] , 18, 6, 1, 6; + + [FeCp*(CO)(PPh3)(CH2)] , pseudo-octahedral (piano stool), [(FeL4X3] , 18, 6, 4, 6; 2+ 2+ [Ru(bpy)3] , pseudo-octahedral, [RuL6] , 18, 6, 2, 6. 2 1.2. In the form [FeCp*( -dtc)2], both dithiocarbamate ligands are chelated to iron, 2 1 [FeL4X3], 19, 5, 3, 7. In the form [FeCp*( -dtc)( -dtc)], one of the two dithio- carbamate ligands is chelated to iron whereas the other is monodentate, [FeL3X3], 17, 5, 3, 6. The two forms having respectively 19 and 17electrons are both to some extent destabilized, being both one electron away (in excess and shortage respectively) with respect to the robust 18-electron structure. The main reaction of 19-electron complexes in the absence of other substrate is to partially decoordinate giving a 17-electron complex, and this reaction is very fast. The main reaction of 17-electron complexes in the presence of a ligandL (in the absence of reducing agent) is also very fast, addition giving the 19-electron complex. Thus, the 536 OGANOMETALLIC CHEMISTRY AND CATALYSIS dissociation of 19-electron complexes and re-association of the 17-electron complex formed with the dissociated ligand make a rapid equilibrium between these two species that only ends up by the reaction of either form, if any. 1.3. It is known that O2 can coordinate to a transition metal in a side-on mode (as ethylene does), which is the case in this complex, or end-on (with an angle) as in hemoglobin and myoglobin. In the case of the side-on coordination, the ligand is an Lligand if the metal is electron poor, the length of the double O=O bond being relatively little changed by the coordination. If, on the other hand, the metal center has a high electron density, as inthis case, the O2ligand undergoes an oxidative addition leading to the lengthening of the O-O bond that can, at the limit, reach the length of a single O-O bond. The metal-O2 species should then be formally III described as an Ir metallocycle, the O2ligand now being a peroxo X2ligand in the Ir-O2 triangle structure. + 1.4. [CoCp2] : organometallic 18-electron, thus stable complex. – [CoCp2] : 20-electron organometallic sandwich complex (triplet state, having two unpaired electrons with the same spin) isoelectronic to nickelocene (a commercial compound). The stabilities of these two complexes are weakened by the double occupancy of the doubly degenerate antibonding orbital (two orbitals having the same energy are occupied by two electrons). The orbital energy level is not too high, however, in spite of its antibonding character, which allows the isolation and crystallization of these two reactive complexes. + [V(CO)7] : the addition of two disadvantages, a coordination number larger than 6 and the cationic nature of a binary metal carbonyl leads to the non-inexistence of this complex in spite of its 18-electron structure. [Cr(H2O)6]: non-existent as all the binary water complexes in which the metal has a low oxidation state such as (0). 2+ – [Ni(H2O)6] : relatively stable 20-electrons complex as [CoCp2] , vide supra, and in addition because of the ideal coordination number (6) and oxidation state (II). 2– [ReH9] : stable 18-electron complex in spite of its very high coordination number, because hydrides, the only ligands present in the coordination sphere, are very small. [Zr(CH2Ph)4]: in principle an 8-electron complex that is thermodynamically stable but kinetically very reactive with many substrates. The stability, in spite of the very low NVE, is due partly to the absence of H, and partly to the interactions between the phenyl rings and the metal decreasing the Zr-C-Ph angle below 109° (the value of the NVE=8, only is conventional and does not take this interactions into account). [Zr(CH2Ph)4(CO)2]: does not exist as almost all the mono- and bimetallic metal-car- bonyl structures in which the metals do not have non-bonding electrons (NNBE=0) (the M-CO bond needs backbonding from some filled metal dorbitals). There are only exceptions in lanthanide chemistry in which the metal-CO bond is very weak (R. Anderson’s work). ANSWERS TO EXERCISES 537 2– [Cr(CO)5] : stable 18-electron complex as all the binary mono- or polyelectronic metal-carbonyl 18-electron complexes in which the metal is at the 0, –1 or –2 oxida- tion state. [Cu(Cl)(PPh3)]: stable; Cu, Ag and Au commonly gives complexes having the MLX 14-electron structure; [Ir(CO)2(PPh3)(Cl)], [Pt(PPh3)3]: 16-electron complexes of noble metals of groups 9 and 10 respectively, very stable as usually the group 8-10 noble metal 16-electron complexes are if the oxidation state is also adequate. [ScCp*2(CH3)]: stable (but reactive) 14-electron complex (classic structure also with the lanthanides, these complexes being initiators of olefin polymerization) [NbCp2(CH3)3]: stable (but reactive) 18-electron organometallic complex. + [FeCp*(dtc)2] : stable 18-electron complex in spite of its odd coordination number (7), because the high oxidation state (IV) is ideal in a mixed inorganic- organometallic complex with dominant inorganic components. 1.5. The optimal stability of this type of complex corresponds to a NVE=18, the number of electrons provided by the ambivalent, versatile ligand Ph2C2 is 4 for two of them and 2 for the 3rd one. 1.6. The order of decreasing thermal stability of these metallocenes is dictated by the 18-electron rule (NEV): [FeCp2] (18e)>[MnCp2] (17e) and [CoCp2] (19e)>[CrCp2] (16e) and [NiCp2] (20e)>[VCp2] (15e)>[TiCp2] (14e). 1.7. The splitting of these 5dorbitals into 3degenerate bonding levels (of identical energy) t2g and 2degenerate antibonding eg levels is represented page40. Manganese has 5delectrons, one in each orbital (the semi-filling of these 5orbitals stabilizes this electronic structure). The total spinS is 5/2 (high-spin structure, 1/2 multiplicity 2S+1: sextuplet state). μtheor.=[5(5+2)] =5.916μB. With Cp*, the 5electron-releasing methyl substituents strengthen the ligand field, forcing the 1/2 electrons to pair in a low-spin state S=1/2 (doublet state: μtheor.=[1(1+2)] =1.732μB). 1.8. The electronic density on manganese increases as the acceptor character of the ligands decreases: CO<CS<C2H4<THF<PPh3. Detection by infrared spectros- copy or cyclic voltammetry: the absorption frequency of the carbonyls and the oxi- dation potential of the complex decrease as the electronic density increases. It is the complex [MnCp(CO)2L], L=CO, that is the most difficult to oxidize in this series. 1.9. Bent sandwich complex, the two carbonyls being in the equatorial plane. The two rings are connected by a dimethylene bridge that hinders the free rotation. One of the Cp’s is pentahapto, whereas the other Cp has to be trihapto in order to obey the 18-electron rule. 538 OGANOMETALLIC CHEMISTRY AND CATALYSIS CHAPTER 2 2.1. CO O OC C CO CO Fe Fe Cr Cr OC C OC CO O OC CH2Ph CO CO OC S CO WW Rh Rh S Ph3P CO OC CO OC Ph P CO OC 3 CH2Ph [FeCp(CO)(μ-CO)]2: [FeL4X2], 18, 6, 6; [CrCp(CO)3]2: [CrL5X2], 18, 4, 7; [W(CO)4(μ2-SCH2Ph)]2: [WL5X2], 18, 4, 7; 5 5 {[Rh(CO)(PPh3)]2( , ,μ2-fulvalenyl)}: [RhL4X], 18, 8, 5. 2.2. 2, 3, 2. 2.3. [Re4H4(CO)12]: NEC=56 (localized count: counting, to simplify, H as bridging 1electron; 17 on each Re, i.e. 68 for 4 Re, minus 12 for the 6 Re-Re bonds of the Re4 tetrahedron); 2– {Fe6[C(CO)16]} : NEC=86. For the localized count, one can attribute 3 CO’s for each of the 4 equatorial Fe’s and 2 for the 2 apical Fe’s that are formally bridged by the Cligand that is doubly bonded to each of the two Fe’s. This gives 18 for each Fe, but the 2electrons of the negative charges make too many for a localized count with 18electrons per Fe. This count gives (618)+2=110 less the 24 of the 12 formal Fe-Fe bonds of the octahedron. [NiCp]6: NEC=90. For the localized count, one has 6 NiL2X5, i.e. 6 19=114 less the 24 of the 12 formal Ni-Ni bonds of the Ni6 octahedron.
Load more

Recommended publications
  • Covalent and Noncovalent Intermediates of an NAD Utilizing Enzyme, Human CD38
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Chemistry & Biology Article Covalent and Noncovalent Intermediates of an NAD Utilizing Enzyme, Human CD38 Qun Liu,1 Irina A. Kriksunov,1 Hong Jiang,2 Richard Graeff,4 Hening Lin,2 Hon Cheung Lee,4,5,* and Quan Hao1,3,5,* 1MacCHESS, Cornell High Energy Synchrotron Source 2Department of Chemistry and Chemical Biology 3School of Applied & Engineering Physics Cornell University, Ithaca, NY 14853, USA 4Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA 5Department of Physiology, University of Hong Kong, Hong Kong, China *Correspondence: [email protected] (H.C.L.), [email protected] (Q.H.) DOI 10.1016/j.chembiol.2008.08.007 SUMMARY These processes are known to have important cellular and physiological functions in DNA repair (Lombard et al., 2005; Enzymatic utilization of nicotinamide adenine dinu- Michan and Sinclair, 2007), transcriptional regulation (Blander cleotide (NAD) has increasingly been shown to have and Guarente, 2004), cellular differentiation and proliferation, fundamental roles in gene regulation, signal trans- aging (Hassa et al., 2006), and calcium signaling (Lee, 2001; duction, and protein modification. Many of the pro- Lee et al., 1999). cesses require the cleavage of the nicotinamide moi- Although NAD is a substrate for multiple enzymes, the initial ety from the substrate and the formation of a reactive steps of the cleavage and release of the nicotinamide moiety are conserved. The nature of the subsequent intermediates intermediate. Using X-ray crystallography, we show formed, on the other hand, has been a widely debatable issue.
    [Show full text]
  • Recommending Hartree-Fock Theory with London- Dispersion and Basis
    Recommending Hartree-Fock Theory with London- Dispersion and Basis-Set-Superposition Corrections for the Optimization or Quantum Refinement of Protein Structures Lars Goerigk,a* Charles A. Collyer,b Jeffrey R. Reimersc,d* a School of Chemistry, The University of Melbourne, Parkville, Victoria 3010, Australia b School of Molecular Bioscience, The University of Sydney, Sydney, New South Wales 2006, Australia c School of Physics and Advanced Materials, The University of Technology, Sydney, NSW 2007, Australia d Centre for Quantum and Molecular Structure, College of Sciences, Shanghai University, Shanghai 200444, China 1 ABSTRACT We demonstrate the importance of properly accounting for London-dispersion and basis-set superposition-error (BSSE) in quantum-chemical optimizations of protein structures, factors that are often still neglected in contemporary applications. We optimize a portion of an ensemble of conformationally flexible lysozyme structures obtained from highly accurate X-ray crystallography data that serves as a reliable benchmark. We not only analyze root-mean-square deviations from the experimental Cartesian coordinates, but, for the first time, also demonstrate how London-dispersion and BSSE influence crystallographic R factors. Our conclusions parallel recent recommendations for the optimization of small gas-phase peptide structures made by some of the present authors: Hartree-Fock theory extended with Grimme’s recent dispersion and BSSE corrections (HF-D3-gCP) is superior to popular density-functional-theory (DFT) approaches. Not only are statistical errors on average lower with HF-D3-gCP, but also its convergence behavior is much better. In particular, we show that the BP86/6-31G* approach should not be relied upon as a black-box method, despite its widespread use, as its success is based on an unpredictable cancellation of errors.
    [Show full text]
  • Preparation of a Germole-Containing Π-Conjugated Polymer by the Te–Li
    Zheng et al. NPG Asia Materials (2020) 12:41 https://doi.org/10.1038/s41427-020-0224-9 NPG Asia Materials ARTICLE Open Access Preparation of a germole-containing π-conjugated polymer by the Te–Li exchange reaction of a tellurophene-containing polymer Feng Zheng1,Sia-ErTan1, Yuki Yanamoto1, Naoki Shida 1, Hiroki Nishiyama1, Shinsuke Inagi1 and Ikuyoshi Tomita 1 Abstract The synthesis and optoelectronic functions of a germole-containing π-conjugated polymer prepared by the reaction of a lithiated polymer precursor are described. A regioregular organometallic polymer having 1,4-dilithio-1,3-butadiene and 9,9-dioctylfluorene-2,7-diyl units was generated by the reaction of a tellurophene-containing polymer having a number-average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of 5900 and 1.9, respectively, with n-butyllithium (2.4 equiv) at −78 to −60 °C for 3 h. The prepared lithiated polymer was reacted with dimethylgermanium dichloride (1.5 equiv) at −60 °C to ambient temperature for 12 h in tetrahydrofuran to produce a π-conjugated polymer possessing 1,1-dimethylgermole-2,5-diyl units in 76% yield (Mn = 4400 and Mw/Mn = 1.7). The absorption maximum and onset of the obtained polymer were observed at 465 and 535 nm, respectively, in the UV-vis spectrum, from which the optical band gap of the polymer was estimated to be 2.31 eV. In the photoluminescence spectrum, the obtained polymer exhibits green fluorescence with an emission maximum of 547 nm and a quantum yield of 0.04. The chemical interaction of the dimethylgermole-containing π-conjugated polymer with fluoride was also examined in terms of the changes observed in the UV-vis absorption spectra.
    [Show full text]
  • Process for Producing Fused-Ring Aromatic Compound, and Conjugated Polymer
    (19) TZZ ¥__T (11) EP 2 774 931 A1 (12) EUROPEAN PATENT APPLICATION published in accordance with Art. 153(4) EPC (43) Date of publication: (51) Int Cl.: 10.09.2014 Bulletin 2014/37 C07F 19/00 (2006.01) C07F 7/08 (2006.01) C07F 7/22 (2006.01) C07F 7/30 (2006.01) (2006.01) (2014.01) (21) Application number: 12844675.4 C08G 61/12 H01L 31/04 (22) Date of filing: 02.11.2012 (86) International application number: PCT/JP2012/078517 (87) International publication number: WO 2013/065836 (10.05.2013 Gazette 2013/19) (84) Designated Contracting States: • KAWAI, Jyunya AL AT BE BG CH CY CZ DE DK EE ES FI FR GB Yokohama-shi GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO Kanagawa 227-8502 (JP) PL PT RO RS SE SI SK SM TR •SATO,Wataru Yokohama-shi (30) Priority: 02.11.2011 JP 2011241498 Kanagawa 227-8502 (JP) 29.11.2011 JP 2011260973 • SATAKE, Kenichi Yokohama-shi (71) Applicant: Mitsubishi Chemical Corporation Kanagawa 227-8502 (JP) Chiyoda-ku • FURUYA, Mitsunori Tokyo 100-8251 (JP) Yokohama-shi Kanagawa 227-8502 (JP) (72) Inventors: • FUJITA, Rieko (74) Representative: HOFFMANN EITLE Yokohama-shi Patent- und Rechtsanwälte Kanagawa 227-8502 (JP) Arabellastrasse 4 81925 München (DE) (54) PROCESS FOR PRODUCING FUSED-RING AROMATIC COMPOUND, AND CONJUGATED POLYMER (57) The invention addresses a problem of purifying having n active groups (wherein n is an integer of 1 or a monomer to be a precursor according to a simpler and more and 4 or less), which comprises bringing a compo- milder method so as to obtain a polymer having a higher sition containing the condensed polycyclic aromatic com- molecular weight.
    [Show full text]
  • Controlling Ligand Substitution Reactions of Organometallic Complexes: Tuning Cancer Cell Cytotoxicity
    Controlling ligand substitution reactions of organometallic complexes: Tuning cancer cell cytotoxicity Fuyi Wang*, Abraha Habtemariam*, Erwin P. L. van der Geer*, Rafael Ferna´ ndez*, Michael Melchart*, Robert J. Deeth†, Rhona Aird‡, Sylvie Guichard‡, Francesca P. A. Fabbiani*, Patricia Lozano-Casal*, Iain D. H. Oswald*, Duncan I. Jodrell‡, Simon Parsons*, and Peter J. Sadler*§ *School of Chemistry, University of Edinburgh, West Mains Road, EH9 3JJ Edinburgh, United Kingdom; †Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom; and ‡CRUK Pharmacology and Drug Development Team, University of Edinburgh Cancer Research Centre, Cancer Research UK Oncology Unit, Crewe Road South, EH4 2XR Edinburgh, United Kingdom Edited by Jack Halpern, University of Chicago, Chicago, IL, and approved October 27, 2005 (received for review July 11, 2005) Organometallic compounds offer broad scope for the design of the factors that control the aqueous chemistry of organometallic therapeutic agents, but this avenue has yet to be widely explored. complexes may therefore also allow the design of effective A key concept in the design of anticancer complexes is optimization anticancer agents. of chemical reactivity to allow facile attack on the target site (e.g., Our studies are focused on monofunctional ruthenium(II) arene DNA) yet avoid attack on other sites associated with unwanted anticancer complexes of the type [(␩6-arene)Ru(ethylenediamin- side effects. Here, we consider how this result can be achieved for e)(X)]nϩ, where X is a leaving group (e.g., Cl). In these pseudooc- monofunctional ‘‘piano-stool’’ ruthenium(II) arene complexes of tahedral ‘‘piano-stool’’ RuII complexes, a ␲-bonded arene (the the type [(␩6-arene)Ru(ethylenediamine)(X)]n؉.
    [Show full text]
  • Preparation and Characterization of Iridium Hydride and Dihydrogen Complexes Relevant to Biomass Deoxygenation
    Preparation and Characterization of Iridium Hydride and Dihydrogen Complexes Relevant to Biomass Deoxygenation Jonathan M. Goldberg A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2017 Reading Committee: D. Michael Heinekey, Chair Karen I. Goldberg, Chair Brandi M. Cossairt Program Authorized to Offer Degree: Department of Chemistry © Copyright 2017 Jonathan M. Goldberg University of Washington Abstract Preparation and Characterization of Iridium Hydride and Dihydrogen Complexes Relevant to Biomass Deoxygenation Jonathan M. Goldberg Chairs of the Supervisory Committee: Professor D. Michael Heinekey Professor Karen I. Goldberg Department of Chemistry This thesis describes the fundamental organometallic reactivity of iridium pincer complexes and their applications to glycerol deoxygenation catalysis. These investigations provide support for each step of a previously proposed glycerol deoxygenation mechanism. Chapter 1 outlines the motivations for this work, specifically the goal of using biomass as a chemical feedstock over more common petroleum-based sources. A discussion of the importance of transforming glycerol to higher value products, such as 1,3-propanediol, is discussed. Chapter 2 describes investigations into the importance of pincer ligand steric factors on the coordination chemistry of the iridium metal center. Full characterization of a five-coordinate iridium-hydride complex is presented; this species was previously proposed to be a catalyst resting state for glycerol deoxygenation. Chapter 3 investigates hydrogen addition to R4(POCOP)Ir(CO) R4 3 t i R4 R4 3 [ POCOP = κ -C6H3-2,6-(OPR2)2 for R = Bu, Pr] and (PCP)Ir(CO) [ (PCP) = κ -C6H3-2,6- t i (CH2PR2)2 for R = Bu, Pr] to give cis- and/or trans-dihydride complexes.
    [Show full text]
  • A Germaaluminocene†
    Chemical Science View Article Online EDGE ARTICLE View Journal | View Issue A germaaluminocene† Cite this: Chem. Sci., 2020, 11, 2982 Lena Albers, * Patrik Tholen, Marc Schmidtmann and Thomas Muller¨ * All publication charges for this article The reactions of dipotassium germacyclopentadienediide with two Group 13 dichlorides, Cp*BCl and have been paid for by the Royal Society 2 * ff of Chemistry Cp AlCl2, yield two structurally di erent products. In the case of boron a borole complex of germanium(II) is obtained. The aluminium halide gives an unprecedented neutral Received 21st January 2020 Accepted 7th February 2020 germaaluminocene. Both compounds were fully characterised by multinuclear NMR spectroscopy supported by DFT computations. The molecular structure of the germaaluminocene was DOI: 10.1039/d0sc00401d determined by XRD. rsc.li/chemical-science Introduction conversion and aer work-up complex 2c was isolated as a brown oil in 35% yield (Scheme 2). NMR spectroscopy evi- The aim of utilizing readily available and environmentally denced the presence of the expected borole ring with a h1- benign main group element compounds for activation of bound cyclopentadienyl substituent. Interestingly, the NMR Creative Commons Attribution-NonCommercial 3.0 Unported Licence. unreactive materials and strong bonds instead of transition data indicated frozen rotation around the B-Ca single bond, metal-based complexes became increasingly popular during the giving rise to ten 13C NMR signals for the cyclopentadienyl last decade.1 We attempted to follow this lead by establishing substituent (Table S3, ESI†). In addition, all four carbon atoms polarised heteroalkenes I as they mimic the electronic situation of the borole ring are magnetically non-equivalent.
    [Show full text]
  • Parallels to Frustrated Lewis/Radical Pair Chemistry
    klh00 | ACSJCA | JCA11.2.5208/W Library-x64 | manuscript.3f (R5.0.i3:5004 | 2.1) 2020/02/05 13:43:00 | PROD-WS-121 | rq_481292 | 7/01/2020 12:12:45 | 10 | JCA-DEFAULT pubs.acs.org/IC Article 1 Redox-Controlled Reactivity at Boron: Parallels to Frustrated Lewis/ 2 Radical Pair Chemistry ⊥ ⊥ 3 Anthony Wong, Jiaxiang Chu, Guang Wu, Joshua Telser, Roman Dobrovetsky, and Gabriel Menard́ * Cite This: https://dx.doi.org/10.1021/acs.inorgchem.0c01464 Read Online ACCESS Metrics & More Article Recommendations *sı Supporting Information 4 ABSTRACT: We report the synthesis of new Lewis-acidic boranes μ 5 tethered to redox-active vanadium centers, (Ph2N)3V( -N)B(C6F5)2 μ 6 (1a)and(N(CH2CH2N(C6F5))3)V( -N)B(C6F5)2 (1b). Redox IV/V 7 control of the V couple resulted in switchable borane versus 8 “hidden” boron radical reactivity, mimicking frustrated Lewis versus 9 frustrated radical pair (FLP/FRP) chemistry, respectively. Whereas V 10 heterolytic FLP-type addition reactions were observed with the V 11 complex (1b) in the presence of a bulky phosphine, homolytic peroxide, IV 12 or Sn−hydride, bond cleavage reactions were observed with the V * μ 13 complex, [CoCp2 ][(N(CH2CH2N(C6F5))3)V( -N)B(C6F5)2](3b), 14 indicative of boron radical anion character. The extent of radical 15 character was probed by spectroscopic and computational means. IV/V 16 Together, these results demonstrate that control of the V oxidation 17 states allows these compounds to access reactivity observed in both FLP 18 and FRP chemistry.
    [Show full text]
  • UNIVERSITY of CALIFORNIA, SAN DIEGO Photoinduced Mixed
    UNIVERSITY OF CALIFORNIA, SAN DIEGO Photoinduced mixed-valency and delocalization dynamics in strongly coupled multinuclear ruthenium complexes A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Chemistry by Jane Susan Henderson Committee in charge: Professor Clifford Kubiak, Chair Professor Andrew Kummel Professor Melvin Okamura Professor Stanley Opella Professor Michael Tauber 2015 Copyright © Jane Henderson, 2015 All rights reserved. The Dissertation of Jane Susan Henderson is approved, and it is acceptable in quality and form for publication on microfilm and electronically: –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Chair University of California, San Diego 2015 iii Dedication For my parents. iv Epigraph Go to bed smarter than when you woke up. –Charlie Munger v TABLE OF CONTENTS Signature Page ....................................................................................................................... iii Dedication .............................................................................................................................. iv Epigraph ................................................................................................................................
    [Show full text]
  • Graphene Supported Rhodium Nanoparticles for Enhanced Electrocatalytic Hydrogen Evolution Reaction Ameerunisha Begum1*, Moumita Bose2 & Golam Moula2
    www.nature.com/scientificreports OPEN Graphene Supported Rhodium Nanoparticles for Enhanced Electrocatalytic Hydrogen Evolution Reaction Ameerunisha Begum1*, Moumita Bose2 & Golam Moula2 Current research on catalysts for proton exchange membrane fuel cells (PEMFC) is based on obtaining higher catalytic activity than platinum particle catalysts on porous carbon. In search of a more sustainable catalyst other than platinum for the catalytic conversion of water to hydrogen gas, a series of nanoparticles of transition metals viz., Rh, Co, Fe, Pt and their composites with functionalized graphene such as RhNPs@f-graphene, CoNPs@f-graphene, PtNPs@f-graphene were synthesized and characterized by SEM and TEM techniques. The SEM analysis indicates that the texture of RhNPs@f- graphene resemble the dispersion of water droplets on lotus leaf. TEM analysis indicates that RhNPs of <10 nm diameter are dispersed on the surface of f-graphene. The air-stable NPs and nanocomposites were used as electrocatalyts for conversion of acidic water to hydrogen gas. The composite RhNPs@f- graphene catalyses hydrogen gas evolution from water containing p-toluene sulphonic acid (p-TsOH) at an onset reduction potential, Ep, −0.117 V which is less than that of PtNPs@f-graphene (Ep, −0.380 V) under identical experimental conditions whereas the onset potential of CoNPs@f-graphene was at Ep, −0.97 V and the FeNPs@f-graphene displayed onset potential at Ep, −1.58 V. The pure rhodium nanoparticles, RhNPs also electrocatalyse at Ep, −0.186 V compared with that of PtNPs at Ep, −0.36 V and that of CoNPs at Ep, −0.98 V.
    [Show full text]
  • Cyclic Voltammetry of Mono- and Diiron(II)Cyclopentadienyl Complexes of Thianthrene and Related Heterocycles R
    Subscriber access provided by University of Texas Libraries Cyclic voltammetry of mono- and diiron(II)Cyclopentadienyl complexes of thianthrene and related heterocycles R. Quin Bligh, Roger Moulton, Allen J. Bard, Adam Piorko, and Ronald G. Sutherland Inorg. Chem., 1989, 28 (13), 2652-2659 • DOI: 10.1021/ic00312a030 Downloaded from http://pubs.acs.org on January 30, 2009 More About This Article The permalink http://dx.doi.org/10.1021/ic00312a030 provides access to: • Links to articles and content related to this article • Copyright permission to reproduce figures and/or text from this article Inorganic Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 2652 Inorg. Chem. 1989, 28, 2652-2659 nate-bond formation, not only for the metal-dioxygen bond but constant reported by Baker et al." For CoSALTMEN, the ox- also for the coordinate bonds between the metal ion and the ligand ygenation constant found here for diglyme solution at 0.5 "C is donor atoms. The increase in the electropositive nature of the very small, ca. -3.5, while the value reportedI2 for DMAC solution metal ion on oxygenation results in strengthening of its coordinate at 5 OC is similar, ca. -3.4. These low values, which seem to be bonds, thus contributing considerably to the exothermicity of the lower than those of any other cobalt Schiff base complexes re- reaction. All entropies of oxygenation are seen to be negative, ported, may indicate steric effects resulting from the distortion a general characteristic for all oxygenation processes. The observed from planarity of the ligand by the four methyl substituents on decrease of entropy is considered derived from two sources: (1) the ethylene bridge.
    [Show full text]
  • Unexpected Barbier-Grignard Allylation of Aldehydes With
    9102 J. Am. Chem. Soc. 1998, 120, 9102-9103 Unexpected Barbier-Grignard Allylation of Grignard allylation of aldehydes (1) with magnesium and allyl Aldehydes with Magnesium in Water halides (2) proceeds smoothly in water (eq 1). Chao-Jun Li* and Wen-Chun Zhang Department of Chemistry, Tulane UniVersity New Orleans, Louisiana 70118 ReceiVed March 26, 1998 To start our investigation, we reacted allyl bromide with benzaldehyde and magnesium turnings in 0.1 N aqueous HCl for An important step in the history of modern chemistry was the 3 h at room temperature. TLC analysis of the ether extract clearly introduction of magnesium for carbon-carbon bond formations1 2 showed a spot that corresponds to the desired allylation product. by Barbier and Grignard about a century ago, through the addition Subsequently, 1H NMR measurement of the crude reaction of an organometallic reagent to a carbonyl group. The study of mixture showed about 28% of the allylation product (3), together magnesium-based reactions since then has sparked the develop- with 66% of the pinacol coupling product (4),11 and 6% benzyl ment of new reagents based on electronically more negative and alcohol. This promising result prompted us to examine factors more positive metals as well as semi-metallic elements for various that influence the reaction. We then examined in greater detail synthetic purposes to tailor reactivities and selectivities (chemo, 3 the effect of the solvent system on the magnesium reaction by regio, and stereo). For carbonyl additions based on organomag- using various combinations of water and THF as the reaction nesium reagents, it is generally accepted that strict anhydrous 4 solvent together with a small amount of iodine to initiate the reaction conditions are required for a smooth reaction.
    [Show full text]