Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc
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The Dependence of the Sio Bond Length on Structural Parameters in Coesite, the Silica Polymorphs, and the Clathrasils
American Mineralogist, Volume 75, pages 748-754, 1990 The dependence of the SiO bond length on structural parameters in coesite, the silica polymorphs, and the clathrasils M. B. BOISEN, JR. Department of Mathematics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, U.S.A. G. V. GIBBS, R. T. DOWNS Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, U.S.A. PHILIPPE D' ARCO Laboratoire de Geologie, Ecole Normale Superieure, 75230 Paris Cedex OS, France ABSTRACT Stepwise multiple regression analyses of the apparent R(SiO) bond lengths were com- pleted for coesite and for the silica polymorphs together with the clathrasils as a function of the variables};(O), P (pressure), f,(Si), B(O), and B(Si). The analysis of 94 bond-length data recorded for coesite at a variety of pressures and temperatures indicates that all five of these variables make a significant contribution to the regression sum of squares with an R2 value of 0.84. A similar analysis of 245 R(SiO) data recorded for silica polymorphs and clathrasils indicate that only three of the variables (B(O), };(O), and P) make a signif- icant contribution to the regression with an R2 value of 0.90. The distribution of B(O) shows a wide range of values from 0.25 to 10.0 A2 with nearly 80% of the observations clustered between 0.25 and 3.0 A2 and the remaining values spread uniformly between 4.5 and 10.0 A2. A regression analysis carried out for these two populations separately indicates, for the data set with B(O) values less than three, that };(O) B(O), P, and };(Si) are all significant with an R2 value of 0.62. -
Asymmetric Solvation of the Zinc Dimer Cation Revealed by Infrared Multiple Photon Dissociation Spectroscopy of + Zn2 (H2O)N (N = 1–20)
International Journal of Molecular Sciences Article Asymmetric Solvation of the Zinc Dimer Cation Revealed by Infrared Multiple Photon Dissociation Spectroscopy of + Zn2 (H2O)n (n = 1–20) Ethan M. Cunningham *,† , Thomas Taxer †, Jakob Heller, Milan Onˇcák , Christian van der Linde and Martin K. Beyer * Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria; [email protected] (T.T.); [email protected] (J.H.); [email protected] (M.O.); [email protected] (C.v.d.L.) * Correspondence: [email protected] (E.M.C.); [email protected] (M.K.B.) † These authors contributed equally to this work. Abstract: Investigating metal-ion solvation—in particular, the fundamental binding interactions— enhances the understanding of many processes, including hydrogen production via catalysis at metal + centers and metal corrosion. Infrared spectra of the hydrated zinc dimer (Zn2 (H2O)n; n = 1–20) were measured in the O–H stretching region, using infrared multiple photon dissociation (IRMPD) spectroscopy. These spectra were then compared with those calculated by using density functional theory. For all cluster sizes, calculated structures adopting asymmetric solvation to one Zn atom in the dimer were found to lie lower in energy than structures adopting symmetric solvation to both Zn atoms. Combining experiment and theory, the spectra show that water molecules preferentially + Citation: Cunningham, E.M.; Taxer, bind to one Zn atom, adopting water binding motifs similar to the Zn (H2O)n complexes studied T.; Heller, J.; Onˇcák,M.; van der + previously. A lower coordination number of 2 was observed for Zn2 (H2O)3, evident from the highly Linde, C.; Beyer, M.K. -
Carbonylation of Protected Or Non-Protected 2-Bromobenzaldehyde Catalyzed by Cobalt Carbonyl
772 Bull. Korean Chem. Soc. 1994, Vol. 15, No. 9 Sang Chui Shim et al. Carbonylation of Protected or Non-protected 2-Bromobenzaldehyde Catalyzed by Cobalt Carbonyl Sang Chui S버 m*, Dong Yub Lee, Heung Jin Choi, Chil Hoon Doh1, and Keun Tai Huh* ^Department of Industrial Chemistry, Kyungpook National University, Taegu 701-702, Korea ^Department of Materials Science and Engineering Kyungsung University, Pusan 608-736, Korea Korea Electrotechnology Research Institute, Changwon, Korea Received May 11, 1994 The cobalt catalyzed carbonylation of bromobenzene having protected aldehyde group gives the corresponding ester in good yields, but 2-bromobenzaldehyde gives 3-alkoxyphthalide in the noticeable yield instead of alkyl 2-formylben- zoates. Introduction Table 1. Carbonylation of 2-Bromobenzenes Having Protected Aldehyde Groups to 2-Substituted Alkyl Benzoates Catalyzed by The metal-catalyzed carbonyl가 ion of aryl halides has ver Cobalt CarbonyF satile utility in the preparative organic chemistry1. Of many Run Reactant catalysts2 used in the carbonylation of aryl halides cobalt Alcohol Product Yield (%y carbonyl species have been conducted under mild conditions, 1 1 CH3CH2OH 2b 88 room temperature and one atmospheric pressure of carbon 2 1 CH3CH2OH 2b 75 。 monoxide. More recently, using dicobalt octacarbonyl at room 3 1 CH3CH2OH 2b 38d temperature under one atmospheric pressure of carbon mo 4 1 CH3OH 2a 80 noxide many applications were reported on the carbonylation 5 1 CH3CH2CH2OH 2c 85 of benzal halides,3-5 and halo (halomethyl)benzenes6-8. 6 (CH3)2CHOH 21 However, studies2,9-11 on the carbonylation of aryl halides 1 2d 7 CH3CH2CH2CH2OH having other reactive functional groups are rare. -
Topological Analysis of the Metal-Metal Bond: a Tutorial Review Christine Lepetit, Pierre Fau, Katia Fajerwerg, Myrtil L
Topological analysis of the metal-metal bond: A tutorial review Christine Lepetit, Pierre Fau, Katia Fajerwerg, Myrtil L. Kahn, Bernard Silvi To cite this version: Christine Lepetit, Pierre Fau, Katia Fajerwerg, Myrtil L. Kahn, Bernard Silvi. Topological analysis of the metal-metal bond: A tutorial review. Coordination Chemistry Reviews, Elsevier, 2017, 345, pp.150-181. 10.1016/j.ccr.2017.04.009. hal-01540328 HAL Id: hal-01540328 https://hal.sorbonne-universite.fr/hal-01540328 Submitted on 16 Jun 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Topological analysis of the metal-metal bond: a tutorial review Christine Lepetita,b, Pierre Faua,b, Katia Fajerwerga,b, MyrtilL. Kahn a,b, Bernard Silvic,∗ aCNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, BP 44099, F-31077 Toulouse Cedex 4, France. bUniversité de Toulouse, UPS, INPT, F-31077 Toulouse Cedex 4, i France cSorbonne Universités, UPMC, Univ Paris 06, UMR 7616, Laboratoire de Chimie Théorique, case courrier 137, 4 place Jussieu, F-75005 Paris, France Abstract This contribution explains how the topological methods of analysis of the electron density and related functions such as the electron localization function (ELF) and the electron localizability indicator (ELI-D) enable the theoretical characterization of various metal-metal (M-M) bonds (multiple M-M bonds, dative M-M bonds). -
Unusual Ring Opening of Hexamethyl Dewar Benzene in Its Reaction with Triosmium Carbonyl Cluster
Organometallics 2003, 22, 2361-2363 2361 Unusual Ring Opening of Hexamethyl Dewar Benzene in Its Reaction with Triosmium Carbonyl Cluster Wen-Yann Yeh* and Yu-Chiao Liu Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan 804 Shie-Ming Peng and Gene-Hsiang Lee Department of Chemistry, National Taiwan University, Taipei, Taiwan 106 Received April 15, 2003 6 Summary: Os3(CO)10(NCMe)2 catalyzes the transforma- HMDB produces the HMB complex [(η -C6Me6)Fe- 11 tion of hexamethyl Dewar benzene (HMDB) to hexameth- (CO)2]2. In rare cases the HMDB moiety has lost its ylbenzene (HMB). This catalytic reaction is in competi- unity, such as in the reaction of RhCl3‚xH2O with 5 tion with ring opening of the HMDB ligand to give (µ- HMDB, causing a ring contraction to give [(η -C5Me5)- 3 12 H)2Os3(CO)9(µ-η -CH(C6Me5)) (1) and (µ-H)Os3(CO)9(µ3- RhCl2]2. However, the coordination chemistry of HMDB 2 t η -C C(C4Me4Et)) (2). with metal clusters has received little attention. We now The coordination chemistry of strained hydrocarbons report that Os3(CO)10(NCMe)2 not only catalyzes the has fascinated chemists striving to understand the conversion of HMDB to HMB but also causes unusual - - details of structure and reactivity.1 In particular, ben- C H and C C bond activations of the HMDB ligand to zene is rich with high-energy strained isomers, such as form unique cluster complexes. Dewar benzene, prismane, and benzvalene, which in- Treatment of Os3(CO)10(NCMe)2 with HMDB (4-fold) terconvert through complex and mysterious rearrange- at -
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. -
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. -
Introduction to Aromaticity
Introduction to Aromaticity Historical Timeline:1 Spotlight on Benzene:2 th • Early 19 century chemists derive benzene formula (C6H6) and molecular mass (78). • Carbon to hydrogen ratio of 1:1 suggests high reactivity and instability. • However, benzene is fairly inert and fails to undergo reactions that characterize normal alkenes. - Benzene remains inert at room temperature. - Benzene is more resistant to catalytic hydrogenation than other alkenes. Possible (but wrong) benzene structures:3 Dewar benzene Prismane Fulvene 2,4- Hexadiyne - Rearranges to benzene at - Rearranges to - Undergoes catalytic - Undergoes catalytic room temperature. Faraday’s benzene. hydrogenation easily. hydrogenation easily - Lots of ring strain. - Lots of ring strain. - Lots of ring strain. 1 Timeline is computer-generated, compiled with information from pg. 594 of Bruice, Organic Chemistry, 4th Edition, Ch. 15.2, and from Chemistry 14C Thinkbook by Dr. Steven Hardinger, Version 4, p. 26 2 Chemistry 14C Thinkbook, p. 26 3 Images of Dewar benzene, prismane, fulvene, and 2,4-Hexadiyne taken from Chemistry 14C Thinkbook, p. 26. Kekulé’s solution: - “snake bites its own tail” (4) Problems with Kekulé’s solution: • If Kekulé’s structure were to have two chloride substituents replacing two hydrogen atoms, there should be a pair of 1,2-dichlorobenzene isomers: one isomer with single bonds separating the Cl atoms, and another with double bonds separating the Cl atoms. • These isomers were never isolated or detected. • Rapid equilibrium proposed, where isomers interconvert so quickly that they cannot be isolated or detected. • Regardless, Kekulé’s structure has C=C’s and normal alkene reactions are still expected. - But the unusual stability of benzene still unexplained. -
© Copyright 2013 Jennifer L. Steele
© Copyright 2013 Jennifer L. Steele DIVALENT TRANSITION METAL CENTERS: THE SYNTHESIS OF NEW CHEMICAL VAPOR DEPOSITION PRECURSORS AND STUDIES OF ETHYLENE POLYMERIZATION AND OLIGOMERIZATION CATALYSTS BY JENNIFER L. STEELE DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry in the Graduate College of the University of Illinois at Urbana-Champaign, 2013 Urbana, Illinois Doctoral Committee: Professor Gregory S. Girolami, Chair Assistant Professor Alison R. Fout Professor John A. Katzenellenbogen Professor Thomas B. Rauchfuss Abstract Volatile transition metal complexes that contain boron hydride ligands are desirable for their potential as precursors for metal diboride films for microelectronics applications. Recently our group has discovered a new class of potential precursors in the metal complexes of the chelating borohydride, N,N-dimethylaminodiboranate (DMADB). To date, attempts to synthesize homoleptic complexes of the late transition metals have afforded intractable mixtures, likely the result of overreduction of the metal center. This work has focused on the synthesis and characterization of heteroleptic complexes of the late transition metals that contain both DMADB and 1,2,3,4,5,-pentamethylcyclopentadienyl ligands. The reaction of metal complexes of the form [Cp*MX]n, where Cp* is 1,2,3,4,5,- pentamethylcyclopentadienyl, M = Cr, Fe, Co, or Ru, and X = Cl or I with sodium dimethylaminodiboranate (NaDMADB) in diethyl ether affords the divalent complexes [Cp*M(DMADB)]. Additionally, the analogous vanadium compound [Cp*V(DMADB)] can be synthesized from the reduction of [Cp*VCl2]3 with NaDMADB in diethyl ether. All of these compounds are volatile under static vacuum at room temperature, but are also thermally sensitive; the iron and ruthenium derivatives decompose at room temperature over a day. -
The Nafure of Silicon-Oxygen Bonds
AmericanMineralogist, Volume 65, pages 321-323, 1980 The nafure of silicon-oxygenbonds LtNus PeurrNc Linus Pauling Institute of Scienceand Medicine 2700 Sand Hill Road, Menlo Park, California 94025 Abstract Donnay and Donnay (1978)have statedthat an electron-densitydetermination carried out on low-quartz by R. F. Stewart(personal communication), which assignscharges -0.5 to the oxygen atoms and +1.0 to the silicon atoms, showsthe silicon-oxygenbond to be only 25 percentionic, and hencethat "the 50/50 descriptionofthe past fifty years,which was based on the electronegativity difference between Si and O, is incorrect." This conclusion, however, ignoresthe evidencethat each silicon-oxygenbond has about 55 percentdouble-bond char- acter,the covalenceof silicon being 6.2,with transferof 2.2 valenc,eelectrons from oxygen to silicon. Stewart'svalue of charge*1.0 on silicon then leads to 52 percentionic characterof the bonds, in excellentagreement with the value 5l percent given by the electronegativity scale. Donnay and Donnay (1978)have recently referred each of the four surrounding oxygen atoms,this ob- to an "absolute" electron-densitydetermination car- servationleads to the conclusionthat the amount of ried out on low-quartz by R. F. Stewart, and have ionic character in the silicon-oxygsa 5ingle bond is statedthat "[t showsthe Si-O bond to be 75 percent 25 percent. It is, however,not justified to make this covalent and only 25 percent ionic; the 50/50 de- assumption. scription of the past fifty years,which was basedon In the first edition of my book (1939)I pointed out the electronegativitydifference between Si and O, is that the observedSi-O bond length in silicates,given incorrect." as 1.604, is about 0.20A less than the sum of the I formulated the electronegativityscale in 1932, single-bond radii of the two atoms (p. -
Density Functional Theory Investigation of Decamethyldizincocene
J. Phys. Chem. A 2005, 109, 7757-7763 7757 Density Functional Theory Investigation of Decamethyldizincocene James W. Kress 7630 Salem Woods DriVe, NorthVille, Michigan 48167 ReceiVed: March 2, 2005; In Final Form: June 17, 2005 A density functional investigation into the structure and vibrational properties of the recently synthesized, novel, Zn(I)-containing species decamethyldizincocene has been performed. Our analysis is in agreement with the general structural properties of the experimental results. We have corroborated the experimental geometry as a true minimum on the global molecular energy surface, confirmed the experimental hypothesis that the Zn atoms are in a Zn(I) state, and provided a detailed analysis of the experimentally undefined Zn-dominant IR and Raman spectral bands of this unusual Zn(I) species. I. Background and Motivation Boatz and Gordon7 was used to determine the intrinsic force constant for the Zn-Zn bond. + The predominant oxidation state for Zn is 2, unlike Hg A method to elucidate the contribution of the Zn atoms and + + 1 which can be 1or 2. Recently, Resa et al. announced their their associated internal coordinates to the IR and Raman spectra 5 synthesis of decamethyldizincocene, Zn2(η -C5Me5)2, an orga- of decamethyldizincocene is provided via the method of the nometallic compound they hypothesized as Zn(I) formally total energy distribution matrix.8 In the framework of the - 2+ derived from the dimetallic [Zn Zn] unit. Their X-ray studies harmonic approximation, vibrational frequencies and normal 5 show that it contains two eclipsed Zn(η -C5Me5) fragments with coordinate displacements are determined by diagonalization of - ( ( aZn Zn distance ( standard deviation) of 2.305( 3) Å, the mass-weighted Cartesian force constant matrix. -
Chapter 2 Polymerisation of MMA Using Novel Chromium(II)
A Thesis Submitted for the Degree of PhD at the University of Warwick Permanent WRAP URL: http://wrap.warwick.ac.uk/133954 Copyright and reuse: This thesis is made available online and is protected by original copyright. Please scroll down to view the document itself. Please refer to the repository record for this item for information to help you to cite it. Our policy information is available from the repository home page. For more information, please contact the WRAP Team at: [email protected] warwick.ac.uk/lib-publications Novel chromium compounds and their use in the polymerisation of methyl methacrylate Mark Andrew Stump A Thesis submitted for the Degree of Doctor of Philosophy Department of Chemistry University of Warwick Coventry CV4 7AL 18th January 1998 A: Table of Contents A Table of Contents 1• B Table of Tables Vlll• • • C Table of Figures xiv D Declaration xix E Acknowledgements XX F Summary xxi G Abbreviations xxii 1. Introduction 2 1.1. An Introduction to Polymers 12 3 1.2. Types of Polymerisation 5 1.2.1. Anionic Polymerisation 5 1.2.2. Co-ordination Polymerisation 7 1.2.3. Radical Polymerisation 9 1.3. Controlled Polymerisation 10 1.3.1. Stereochemistry of vinyl polymerisation 10 1.3.2. Other Aspects of Controlled Polymerisation 12 1.4. Living Polymerisation 13 1.5. An Introduction To Chromium Chemistry 22 1.6. Methods of Analysis for Polymers 34 1.6.1. Size Exclusion Chromatography (SEC) 34 1.6.2. Thermal Gravimetric Analysis (TGA) 35 1.7. References 44 2. Polymerisation of MMA using novel chromium(II) and (III) compounds in conjunction with alkyl halides 49 2.1.