DFT study of the mechanism of alkane hydrogenolysis by transition metal hydrides 1. Interaction of silica-supported zirconium hydrides with methane

摘要

Model reactions of silica-supported zirconium hydrides (ident to Si - O-)_3ZrH and (ident to Si-O-)_2ZrH_2 with methane, resulting in cleavage of a C-H bond in the methane molecule and the formation of (ident to Si -O-)_3ZrCH_3 and (ident to Si -O-)_2Zr(H)CH_3 as products were studied using the DFT approach with the PBE density functional. The processes proceed as bimolecular reactions without preliminary formation of agostic complexes. According to calculations, zirconium dihydrides (ident to Si -O-)_2ZrH_2 are more reactive toward the methane C-H bonds than zirconium monohydrides (ident to Si - O -)_3ZrH. The calculated activation energies of the reactions with participation of zirconium dihydrides (ident Si - O-)_2ZrH_2 are in better agreement with the known experimental data for the Yermakov-Basset catalytic system.