THE EFFECTS OF COVALENT LIGANDS ON THE OXIDATIVE ADDITION-REACTION BETWEEN 2ND-ROW TRANSITION-METAL ATOMS AND METHANE

Calculations including electron correlation of all valence electrons h ave been performed to study covalent ligand effects in the oxidative a ddition reaction of methane to second-row transition-metal complexes. Both reaction energies and barrier heights have been determined. As a comparison the reaction energies for the oxidative addition of the hyd rogen molecule have also been evaluated. The entire sequence of second -row transition metals from yttrium to palladium has been studied. Hyd rogen ligands have been added to systematically saturate all valencies of each metal, which means that results for 23 different reactions ea ch for the oxidative addition of methane and of molecular hydrogen hav e been obtained. The results are analyzed in terms of promotion energi es, loss of exchange energies, and steric and other electronic repulsi on effects. The lowest barrier for the methane reaction is found for R uH2 while the largest exothermicity occurs for ZrH2.