Formation of [CH₄–Fe]^q (q = −1, 0, +1) Complexes and Oxidative Addition of Methane to Fe^q Atoms. A Qualitative Molecular Orbital Study

The formation of [CH₄-Fe]_q complexes and the oxidative addition of methane to iron metal centers Fe^q (q = +1, 0, −1) was studied by using the MINDO/SR-UHF method. The methane-Fe interaction was examined by optimizing several geometries with C_3v, C_2v, and C₈ symmetries. Diatomic energies, bond orders, and electronic configuration of metallic centers have been correlated with the interaction energy among the components of the system. The potential energy curves for the oxidative addition of the intermediate species were calculated for C₈ symmetry. Results show that the formation of intermediates and the oxidative addition are favored as the system between negatively charged, suggesting that an electronic transfer from the metal to the methane promotes the C–H bond activation. It was also found that an increase in the p character of the metal center favors the C–H bond-dissociation process.