Intrinsic Reaction Coordinate Analysis of the Activation of CH4 by Molybdenum Atoms: A Density Functional Theory Study of the Crossing Seams of the Potential Energy Surfaces

Density functional theory (DFT) calculations were performed to investigate the quintet, triplet, and singlet potential energy surfaces associated with the C-H activation of methane by laser-ablated molybdenum (Mo) atoms recently observed experimentally by Andrews and co-workers. The present computational study aims to better understand the nature of the reaction mechanisms for C-H activation by Mo atoms. The processes for activation of methane by the excited Mo atoms appear to produce CH3—MoH, CH2═MoH2, and CH≡MoH3 complexes. The crossing seams between the potential energy surfaces and possible spin inversion processes for the direct conversion of methane to a high oxidation state transition metal complex that contains a carbon-metal double or triple bond are examined using the intrinsic reaction coordinate (IRC) approach. The minimum energy reaction pathway is found to involve spin inversion three times in different reaction steps. In total, three spin states (quintet, triplet, and singlet) are involved ...