DFT Study On The Hydrosilylation Of Carbonyl Compounds By High-valence Mo(VI)/Mn(V) Complexes

Recently, with the rapid development of computer technology, quantum computational methods has become an effective and main means to reveal the mechanism of chemical reactions. In the present study, we have re-investigated the high-valent molybdenum(VI)-dioxo complex MoO2CO2 and manganese complex catalyze hydrosilylation of unsaturated organic substrates applying DFT methods. The inner mechanism of hydrosilylation of carbonyl compounds catalyzed by the above system was proposed. The contents of the paper are as follows:1. In-depthly studies Mechanism of high-valent molybdenum(VI)-dioxo complex catalyzed hydrosilylation of diphenylketone. Using B3LYP-D functional to perform all molecular geometries of complexes and compare the energy of different pathways,we propose an ionic outer-sphere mechanistic pathway to be the most favorable pathway. The ionic outer-sphere mechanistic pathway includes three steps: (1) silane of PhMe2SiH is initially coordinated to the Mo(VI) center to give ?1-silane adduct; (2)the carbonyl substrate back-side attacking the silicon center of ?-silane molybdenum adduct to heterolytically cleavage Si-H bonds; (3) the silylcarbenium ion abstracting the hydride on molybdenum hydride to yield silyl ether.2. In-detailedly studies the high-valent manganese complex catalyzed reduction of benzaldehyde to benzyl alcohol with hydrosilanes using Density Functional Theory(DFT) calculations with the B3LYP-D function. On the basis of the computed free energy profiles for all possible these pathways, we found that the carbonyl pre-coordination pathway to be the most favorable pathway.These studies show that the quantum computational methods in mechanistic studies of high-valent transition-metal complexes catalyzed hydrosilylation. Not only can obtain important intermediates and transition state structures and potential energy spectrum of the reaction but also can provide information that is difficult to gain from experimental means.