DFT Study On Catalytic Organic Reduction Of Re (Ⅴ) / Mo (Ⅵ) - Oxo In High - Valent

The calculation method of quantum chemistry has been widely used in various fields of chemical research, and it is a powerful tool for quantification of organic reaction mechanism. In this paper, we use Gaussian 09 program and density functional theory to study the inner mechanism of hydrosilylation/hydroboration of carbonyl compounds catalyzed by the high-valent mono-oxido-rhenium(V) complex and oxo-molybdenum(VI) complex. The main contents are as follows:The first chapter mainly introduces the primitive steps of the transition-metal complexes catalysis to organic reactions and the mechanism of transition-metal complexes catalysis of hydrosilylation and hydroboration.The second chapter simply introduces the calculation methods of density functional theory.The third chapter mainly introduces the research of the mechanism of high-valent mono-oxido-rhenium(V) complex catalyzing the hydrosilylation of benzaldehyde. Using B3LYP density functional theory to calculate the free energy of all important states and compare different pathways’potential energy surface. The final result can be concluded that the favorable catalytic cycles for rhenium complex Re(O)Cl3(PPh3)2 catalyzing the hydrosilylation of carbonyl compounds is the ionic mechanistic pathway. The rhenium hydride Re(O)(H)Cl2(PPh3)2 catalyzing the hydrosilylation of carbonyl compounds proceeds via the two competing pathways:the carbonyl pre-coordination pathway and the ionic mechanistic pathway.The fourth chapter mainly introduces the research of the mechanism of high-valent oxo-molybdenum complex MoO2Cl2 catalyzing B-H bond activation. Using M06 density functional theory to calculate the free energy of all important states and compare different pathways’potential energy surface. The final result can be concluded that the MoO2Cl2 catalyzing the hydroboration of dipenylketone proceeds via the two competing pathways:the [2+2] addition pathway and the ionic mechanistic pathway. The MoO2Cl2 catalyzing the hydroboration of organic substrates like benzamide, benzonitrile and N-(diphenylmethylene)benzenamine proceeds via the ionic mechanistic pathway.These studies show the reliability of quantum computational methods in mechanism studies of transition-metal complexes mediated organic reactions. It also can make up for the deficiencies of experimental study.