Theoretical investigation of the insertion of nickel in the CH bond of CH4. Electronic structure calculations and dynamics

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Abstract
The insertion of a nickel atom in the CH bond of CH4 is calculated using density functional theory by determining the transition state and the dissociated state of HNiCH3. A barrier for nickel insertion of 40.7 kJ/mol is found and its origin is discussed. The insertion is exothermic by 34.0 kJ/mol. From the potential energy surface at the transition state and the dissociated state vibrational and rotational frequencies are obtained. Unimolecular and bimolecular transition state theory is used for the calculation of rate constants, sticking coefficients, and activation energies for the nickel insertion reaction as well as the nickel elimination reaction. Activation energies for nickel insertion in both CH4 and CD4 are small compared with other theoretical work. A moderate kinetic isotope effect for the insertion reaction is found when all hydrogens are substituted by deuterium, whereas no significant kinetic isotope effect is found for nickel elimination. Hydrogen tunneling corrections on rate coefficients are also evaluated, but their effect is negligible. Sticking coefficients are small, which is consistent with experimental sticking coefficients of CH4 on nickel surfaces.