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

Abstract

Model reactions of silica-supported zirconium hydrides (≡Si—O—)3ZrH and (≡Si—O—)2ZrH2 with methane, resulting in cleavage of a C—H bond in the methane molecule and the formation of (≡Si—O—)3ZrCH3 and (≡Si—O—)2Zr(H)CH3 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 (≡Si—O—)2ZrH2 are more reactive toward the methane C—H bonds than zirconium monohydrides (≡Si—O—)3ZrH. The calculated activation energies of the reactions with participation of zirconium dihydrides (≡Si—O—)2ZrH2 are in better agreement with the known experimental data for the Yermakov—Basset catalytic system.