Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [114]-123).

Computational methods were employed to investigate catalytic processes. First, DFT calculations predicted the important geometry metrics of a copper–nitrene complex. MCSCF calculations supported the open-shell singlet state as the ground state of a monomeric copper nitrene, which was consistent with the diamagnetic character deduced from experimental observations. The calculations predicted an elusive terminal copper nitrene intermediate. Second, DFT methods were carried out to investigate the mechanism of C–F bond activation by a low-coordinate cobalt(I) complex. The computational models suggested that oxidative addition, which is very rare for 3d metals, was preferred. A π–adduct of PhF was predicted to be a plausible intermediate via calculations. Third, DFT calculations were performed to study ancillary ligand effects on C(sp3)–N bond forming reductive elimination from alkylpalladium(II) amido complexes with different phosphine supporting ligands. The dimerization study of alkylpalladium(II) amido complexes indicated an unique arrangement of dative and covalent Pd-N bonds within the core four-membered ring of bimetallic complexes. In conclusion, computational methods enrich the arsenal of methods available to study catalytic processes in conjunction with experiments.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch,2005. / This study comprises the preparation and full characterisation of new carbene complexes of group 10 metals (Ni, Pd or Pt), the group 9 metal, rhodium, as well as group 6 metals (Cr and/or W). N-heterocyclic carbene (NHC) complexes of nickel and palladium were prepared via oxidative addition of the corresponding carbene precursors imidazolium-, imidazolinium-, pyridinium- and quinolinium chloride salts, to M(PPh3)4 (M = Ni or Pd). Three types of carbene complexes, namely the standard five-membered two-N carbene complexes, new six-membered NHC complexes and novel six-membered rNHC complexes received attention. In the rNHC complexes the heteroatom (N) is removed from the carbene carbon. These new square planar carbene complexes of the general formula trans-[(PPh3)2MCl(L)]X (M = Ni or Pd; X = BF4 or PF6) L = 1,3-dimethyl-2,3-dihydro-1Himidazol- 2-ylidene, 1,3-dimethyl-2,3,4,5-tetrahydro-1H-imidazol-2-ylidene, 1-methyl-1,2-dihydropyridin- 2-ylidene, 1-methyl-1,2-dihydro-quinolin-2-ylidene, 1,4-dimethyl-1,2-dihydro-quinolin-2- ylidene, 2-methoxy-1-methyl-1,4-dihydro-quinolin-4-ylidene, 1-methyl-1,4-dihydro-pyridin-4- ylidene) have been isolated and characterised. The preparation of the corresponding carbene complexes of platinum was complicated by the formation of [PtCl(PPh3)3]BF4 and the desired carbene complexes could not be isolated in pure form. The investigation of rNHC complexes was extended to include the synthesis of (CO)5M{CSC(CNCMe2CH2O)CHCH} (M = Cr and W). The molecular and crystal structures of thirteen of the new carbene complexes including the structures of both cis- (only formed below –20°C) and trans-chloro(1-methyl-1,2-dihydro-quinolin- 2-ylidene)bis(triphenylphosphine)palladium(II) tetrafluoroborate were determined. The metalcarbene bond distances in both the palladium and nickel carbene families do not differ significantly. The carbene ligands can be arranged in a series of increasing trans-influence, using the metalchloride bond distance as a guideline, as follows: 1,3-dimethyl-2,3-dihydro-1H-imidazol-2-ylidene and 1,3-dimethyl-2,3,4,5-tetrahydro-1H-imidazol-2-ylidene < 1-methyl-1,2-dihydro-pyridin-2- ylidene < 2-methoxy-1-methyl-1,4-dihydro-quinolin-4-ylidene, 1-methyl-1,4-dihydro-pyridin-4- ylidene. The crystal and molecular structures of two platinum compounds, cis-chloro(2-methoxy-1- methyl-1,4-dihydro-quinolin-4-ylidene)bis(triphenylphosphine)platinum(II) tetrafluoroborate and the byproduct [PtCl(PPh3)3]BF4 were also determined. Trans-chloro(2-methoxy-1-methyl-1,4-dihydro-quinolin-4-ylidene)bis(triphenylphosphine) palladium(II) tetrafluoroborate was found to be a very active catalyst, compared to simpler palladium carbene and phosphine complexes, in the Mizoroki-Heck and Suzuki-Miyaura coupling reactions. Quantum mechanical calculations indicated that the rNHC ligand in this complex is bound stronger to the palladium than a standard imidazole-derived NHC ligand. Further calculations suggested that the remote heteroatom carbene (rNHC) complexes of nickel(II) are significantly more stable when compared to the normal carbene (NHC) complexes. Energy decomposition analysis suggested that the rNHC ligands are strong s-donors and weak -acceptors. Unsymmetrical imidazolium-derived bis(carbene) complexes, [Rh(NHC)2COD]Br, bromomono( carbene) complexes, Rh(Br)COD(NHC), and chloro-mono(carbene) complexes, Rh(Cl)COD(NHC) where NHC = 1-R-3-methyl-2,3-dihydro-1H-imidazol-2-ylidene (R = ethyl, propyl or butyl), were formed in each reaction of the corresponding free carbene ligand with [Rh(Cl)COD]2. [Rh(Br)COD(NHC)] formed as a result of substitution of a chloride ligand by a Br-- anion. The carbonyl complexes, cis-[Rh(CO)2X(NHC)] (X = Br or Cl; NHC = 1-ethyl-3-methyl- 2,3-dihydro-1H-imidazol-2-ylidene) were isolated after the substitution of the COD ligand in Rh(X)COD(NHC) (X = Br or Cl) with CO. Isomerisation of these cis-carbonyl complexes to the trans isomers was observed. Cis-[(h4-1,5-cyclooctadiene)bis(1-butyl-3-methyl-2,3-dihydro-1H-imidazol-2-ylidene)rhodium(I)] bromide, bromo(h4-1,5-cyclooctadiene)(1-methyl-3-propyl-2,3-dihydro-1H-imidazol-2-ylidene) rhodium(I) and cis-[(h4-1,5-cyclooctadiene)bis(1-butyl-3-methyl-2,3-dihydro-1H-imidazol-2- ylidene)rhodium(I)]bromide were also characterised by single crystal X-ray diffraction. The synthesis and structural characterisation of a series of acyclic and heterometallacyclic Fischertype carbene complexes in which a soft donor atom (P) attached to the carbene side chain is either uncoordinated, (CO)5M=C(NMe2)CH2PPh2 (M = Cr or W), bonded to the original central metals (Cr or W) in four-membered chelates, (CO)4M=C(NMe2)CH2PPh2, or coordinated to a second M(CO)5 unit (only isolated for chromium) (CO)5Cr=C(NMe2)CH2P(Ph2)Cr(CO)5, were carried out. These compounds were produced by the reaction of the anionic Fischer-type aminocarbene complexes, [(CO)5Cr=C(NMe2)CH2]Li (M = Cr or W), with ClPPh2. The formation of the four-membered chelates, via cyclisation, occurs much faster for Cr than for W. The aminocarbene-phosphine chelates represent the first examples of structurally characterised, four-membered C,P-chelate carbene complexes.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

This Thesis describes the synthesis and characterisation of a series ofbisphenolate supported samarium borohydride, amide and zwitterionic rare earth complexes and their ability to effect the ring opening polymerisation (ROP) of cyclic esters and methylmethacrylate (MMA). Chapter 1 introduces ROP from both an industrial and an academic perspective and describes in detail the research in this area, with emphasis on rare earth initiators. The lanthanide elements and the bisphenolate ligand are also introduced. Chapter 2 describes the synthesis and characterisation ofbisphenolate supported samarium borohydride and silylamide complexes. Chapter 3 describes the ability of a selection of samarium borohydride and amide complexes to effect the ROP of the cyclic esters s-caprolactone (f-CL) and rac- lactide (rac-LA). Emphasis is placed on the effect that the nature of the bisphenolate pendant arm and the initiating moiety has on the polymerisation process. Chapter 4 describes the synthesis and characterisation of rare earth zwitterionic complexes and the ability ofa range of these complexes to effect the ROP of s-Cl. and rac-lactide. Mechanistic aspects ofthe ROP process will be discussed, as will the ability of these complexes to yield amide functionalised poly(rac-LA). Chapter 5 describes the ability ofbisphenolate samarium borohydride complexes to initiate the polymerisation of MMA. The experimental work conducted as part of this study is further supported computationally by calculations at the DFT level, both aspects will be described. Aspects concerning the synthesis and characterisation of the related borohydride derivative [Sm(N2siMe3NNPY)(BH4)2Li]oo will also be emphasised. Chapter 6 contains full experimental and characterising data for all 0 f the new compounds reported in this Thesis. Appendices A- T contain tables of selected crystallographic data for all new crystallographically characterised complexes described in this Thesis (partially on CD).

Ku, Ka Wai. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

by Chan Chun-Chung, Jerry. / The "59" in Co in title is superscript. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 157-170). / DESCRIPTIVE NOTE --- p.iii / Chapter CHAPTER ONE: --- A BRIEF SURVEY OF TRANSITION METAL NMR STUDIES --- p.1 / Chapter 1.0 --- Introduction --- p.1 / Chapter 1.1 --- Solution NMR Of Transition Metals --- p.2 / Chapter 1.1.1 --- Parametrization Model of Chemical Shifts --- p.4 / Chapter 1.2 --- Theoretical Calculation of the Chemical Shielding Constants of Transition Metals --- p.6 / Chapter 1.3 --- Solid State NMR of Transition Metals --- p.7 / Chapter 1.4 --- Scope of the Thesis --- p.9 / Chapter CHAPTER TWO: --- THEORY AND BACKGROUND --- p.10 / Chapter 2.0 --- Introduction --- p.10 / Chapter 2.1 --- The Origin of Chemical Shielding --- p.10 / Chapter 2.1.1 --- The Ramsey Shielding Tensor Equation with Gauge Origin Chosen at the Nucleus --- p.13 / Chapter 2.1.2 --- The Ramsey Shielding Tensor Equation with Arbitrary Gauge Origin --- p.20 / Chapter 2.1.3 --- The Physical Picture Associated with the Ramsey Shielding Equation --- p.21 / Chapter 2.2 --- Ab Initio Shielding Calculation --- p.24 / Chapter 2.2.1 --- Coupled Hartree-Fock Method --- p.25 / Chapter 2.2.2 --- Gauge Dependence Problem --- p.27 / Chapter 2.2.3 --- Post Hartree-Fock Methods --- p.29 / Chapter 2.3 --- Density Functional Theory --- p.30 / Chapter 2.3.1 --- The Hohenberg-Kohn Theorems --- p.30 / Chapter 2.3.2 --- The Kohn-Sham Approach --- p.35 / Chapter 2.3.3 --- Approximation to the Exchange- Correlation Energy --- p.37 / Chapter CHAPTER THREE: --- INTERPRETATION OF 59Co NMR SHIELDING USING THE HARD AND SOFT ACID-BASE CONCEPT -- INSIGHT INTO THE RELATIVE MAGNITUDE OF THE NEPHELAUXETIC AND THE SPETROCHEMICAL EFFECT --- p.39 / Chapter 3.0 --- Introduction --- p.39 / Chapter 3.1 --- Theory --- p.42 / Chapter 3.2 --- Evaluation of the Model --- p.45 / Chapter 3.3 --- Application to the Studies of trans-[Co(en)2X2](3+2n) + in Different Solvents and the Determination of the Spectrochemical Trend --- p.54 / Chapter 3.4 --- "Simultaneous Determination of the Nuclear Quadrupole Coupling Constant, Chemical Shift Anisotropy and Rotational Correlation Time in trans-Na[Co(acac)2(NO2)2]， trans- [Co(acac)2(NH3)2 ]I, trans-[Co(acac)2(CH3NH2)2]I and trans-[Co(acac)2(NH3)(NO2)]" --- p.59 / Chapter 3.5 --- Summary --- p.64 / Chapter CHAPTER FOUR: --- DENSITY FUNCTIONAL STUDY OF THE ELECTRONIC STRUCTURES OF [Co(NH3)5X](3+n)+ USING DIFFERENT POPULATION AND BONDING ANALYSIS METHODS --- p.66 / Chapter 4.0 --- Introduction --- p.66 / Chapter 4.1 --- Computational Details --- p.69 / Chapter 4.2 --- Bond Covalency Analysis of [Co(NH3)5X](3+n)+ --- p.71 / Chapter 4.2.1 --- Mayer Bond Order Analysis --- p.71 / Chapter 4.2.2 --- Natural Population Analysis --- p.73 / Chapter 4.2.3 --- Natural Bond Orbital Analysis --- p.76 / Chapter 4.2.4 --- Mulliken Population Analysis --- p.82 / Chapter 4.3 --- Summary --- p.86 / Chapter CHAPTER FIVE: --- DENSITY FUNCTIONAL STUDY OF 59Co CHEMICAL SHIELDING CONSTANTS --- p.87 / Chapter 5.0 --- Introduction --- p.87 / Chapter 5.1 --- SOS-DFPT-IGLO Calculations of 59Co NMR Shielding Parameters of Hexacoordinated Diamagnetic Co(III) Complexes --- p.90 / Chapter 5.1.1 --- Computational Details --- p.91 / Chapter 5.1.2 --- Basis Sets and XC Functional for 59Co Shielding Calculations --- p.92 / Chapter 5.1.2.1 --- 59Co NMR Shielding Calculation of [Co(CN)6]3- --- p.92 / Chapter 5.1.2.2 --- Nearest Neighbour Effect --- p.94 / Chapter 5.1.3 --- Comparison of the Calculated and Experimental 59Co Chemical Shift Anisotropy and Asymmetry Factor --- p.95 / Chapter 5.1.4 --- Comparison of the Calculated and Experimental 59Co Isotropic Chemical Shifts --- p.97 / Chapter 5.1.4.1 --- Reproducing the Experimental Trend by SOS-DFPT-IGLO? --- p.99 / Chapter 5.1.4.2 --- Local and Non-local Paramagnetic Shielding Contributions --- p.103 / Chapter 5.1.5 --- General Comments of the Calculated Results --- p.104 / Chapter 5.2 --- A Comparative Study of the Calculation of 59Co NMR Shielding Constants of Hexacoordinated Diamagnetic Co(III) Complexes Using SOS-DFPT-IGLO and Hybrid DFT-GIAO Methods --- p.105 / Chapter 5.2.1 --- Computational Details --- p.106 / Chapter 5.2.2 --- Comparison of DFT-IGLO-Becke/Perdew and DFT-GIAO-Becke/Perdew --- p.106 / Chapter 5.2.3 --- DFT-GIAO-B3LYP --- p.108 / Chapter 5.2.4 --- Summary --- p.111 / Chapter CHAPTER SIX: --- STUDY OF THE SHIELDING CONSTANTS OF DIAMAGNETIC HEXACOORDINATED Co(III) COMPLEXES BY POLYCRYSTALLINE 59Co NMR AND DENSITY FUNCTIONAL THEORY --- p.112 / Chapter 6.0 --- Introduction --- p.112 / Chapter 6.1 --- Solid State NMR Technique for Quadrupolar Nuclei --- p.112 / Chapter 6.2 --- Static Powder Lineshape Analysis --- p.114 / Chapter 6.2.1 --- Excitation of Quadrupolar Nuclei --- p.114 / Chapter 6.2.1.1 --- Selective and Partially Selective Excitation --- p.116 / Chapter 6.2.2 --- Spin Echo Pulse Sequence --- p.117 / Chapter 6.2.3 --- Lineshape Simulation --- p.120 / Chapter 6.3 --- Solid State 59Co NMR Study of Hexacoordinated Co(III) Complexes --- p.124 / Chapter 6.3.1 --- Experimental --- p.124 / Chapter 6.3.2 --- Simulation Details --- p.125 / Chapter 6.3.2.1 --- [Co(NH3)4CO3]NO3 --- p.127 / Chapter 6.3.2.2 --- [Co(en)2CO3]Cl and [Co(en)2NO3](NO3)2 --- p.130 / Chapter 6.3.2.3 --- cis-[Co(en)2(N02)2]NO3 and cis-[Co(en)2(N3)2]NO3 --- p.133 / Chapter 6.3.2.4 --- K3[Co(CN)6] --- p.133 / Chapter 6.3.2.5 --- "Co(acac)3， K3[Co(NO2)6] and [Co(en)3]X3 (X = C1, Br, I)" --- p.137 / Chapter 6.4 --- Dependence of 59Co Shielding Calculation on Basis Sets and Exchange Correlation Functional --- p.143 / Chapter 6.4.1 --- CSA and η calculations of [Co(NH3)4C03] Br --- p.144 / Chapter 6.4.2 --- CSA and η Calculations of [Co(NH3)6]C13 --- p.147 / Chapter 6.4.3 --- Shielding Calculations of Larger Co(III) Complexes at B3PW91/6311+G* Level --- p.149 / Chapter 6.5 --- Summary --- p.153 / Chapter CHAPTER SEVEN: --- CONCLUSION AND FUTURE WORK --- p.154 / BIBLIOGRAPHY --- p.157 / APPENDIX A MATHEMATICAL DETAILS FOR THE DERIVATION OF THE RAMSEY SHIELDING EQUATION --- p.171 / APPENDIX B ANALYSIS OF THE SIGN OF PARAMAGNETIC AND DIAMAGNETIC SHIELDING --- p.178 / APPENDIX C GENERALIZATION OF EQUATION [3.4] TO INCLUDE THE EFFECT OF π-BONDING --- p.181 / APPENDIX D GEOMETRY OPTIMIZATION OF CoH AND CoO --- p.183 / APPENDIX E A NON-LINEAR ITERATIVE LEAST SQUARE FITTING PROCEDURE FOR THE ANALYSIS OF SOLID STATE NMR STATIC SPECTRUM OF QUADRUPOLAR NUCLEUS --- p.187