‘Ab initio’ calculations on methane interacting with the fourteen-electron Ni(PH3)2 fragment

Abstract

Ab initio restricted Hartree–Fock and configuration interaction calculations have been carried out on the system Ni(PH₃)₂+ CH₄ in order to study the energetics and the mechanism of the oxidative-addition reaction of CH₄ and to model the activation of the C–H bond by zerovalent, co-ordinatively unsaturated transition-metal complexes. Energy-gradient optimizations and transition-state localizations have been performed on reactants and products in various constrained geometries. The results indicate that the oxidative addition of methane to Ni(PH₃)₂ is endothermic by 7.0 kcal mol^–1 and the planar trans product is the most stable, being lower in energy than the cis isomer by 3.4 kcal mol^–1.