Structural features of transition metal complexes having ligands with different electronic properties and mechanistic aspect of carbon-hydrogen bond activation and functionalization by transition metal complexes.

摘要

Theoretical studies on the structural features of transition-metal complexes having ligands with different electronic properties and mechanism for stoichiometric and catalytic transition-metal reactions are reported in this thesis. Having a clear picture of the nature of transition-metal-ligand bonding is important in understanding structures, properties and reactivity of transition metal complexes. Knowledge of mechanistic aspect is very useful in designing better and effective catalysts.; The development of Dewar-Chatt-Duncanson model has a great impact on coordination/organometallic chemistry in terms of understanding the structure and bonding in metal complexes containing π-accepting ligands. The majority of π-acceptor ligands can be categorized into two types, double-face and single-face π-accepting ligands. Metal complexes containing both single-face and double-face π-accepting ligands show unique structural preferences. The structural consequence for these complexes will be discussed with the aid of density functional theory (DFT) calculations. Examples include η 1-alkenyl, η2-silane, η2-alkene and boryl octahedral complexes.; The X-ray diffraction shows that the relative orientations of three amido ligands in the titanium and zirconium amido complexes containing a hydrotris(pyrazolyl)borate (Tp) or hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) ligand TpM(NMe₂ )₃ and Tp*M(NMe₂)₃ (M = Ti, Zr) are quite different. Theoretical calculations at the B3PW91 level of the density functional theory on model complexes TPTi(NMe₂)₃ and TPZr(NMe₂)₃ were performed to rationalize the observed orientations and the rotational behavior of amido ligands in these metal complexes.; Bonding analysis has been performed for titanocene borane σ-complexes Cp2Ti(η2-HBcat)₂ and Cp₂Ti(PMe ₃)(η2-HBcat) to investigate the unusual metal η 2-HBcat bonding interactions with the aid of density functional theory calculations at the level of B3PW91. The significantly short BB contact in the former complex is explained with a three-center-two-electron bond involving the B-Ti-B triangle. In the Cp₂Ti(PMe₃)(η 2-HBcat) complex, a related bonding feature involving a metal d orbital and an sp3 hybridized fragment orbital derived from the HBcat ligand is found to be responsible for the metal boron interaction.; The H/D exchange processes between CH₄ and deuterated organic solvents—benzene-d₆ and diethyl ether- d₁₀ catalyzed by the ruthenium complex TpRu(PPh₃ )(CH₃CN)H (Tp = hydrotris(pyrazolyl)borate)—have been investigated by density functional theory calculations at the B3LYP level. Theoretical study on the reaction mechanism suggests that σ-complexes TpRu(PPh₃)(η2-H-R)H are active species in the exchange processes. During the exchange processes, the reversible transformations of TpRu(PPh₃)(η2-H-R)H to TPRu(PPh ₃)(η2-H₂)R are the crucial steps. (Abstract shortened by UMI.)