THEORETICAL-STUDIES OF INORGANIC AND ORGANOMETALLIC REACTION-MECHANISMS .6. METHANE ACTIVATION ON TRANSIENT CYCLOPENTADIENYLCARBONYLRHODIUM

The C-H oxidative-addition of methane to the transient RhCp(CO) complex was studied with ab initio RHF and MP2 techniques. Electron correlation dramatically alters the reaction energetics and shifts the intermediate later and the transition state earlier in the reaction coordinate. The MP2 calculations predict an intermediate stabilized by 14.8 kcal/mol, a transition state with an activation barrier of 4.1 kcal/mol relative to the intermediate, and a reaction product exothermic by 30.6 kcal/mol. Analyses of the molecular structure and the Laplacian of the total charge density reveal an agostic-like intermediate with metal-CH dative interaction in the early stage of the reaction. The transition state shows obvious C-H bond breaking and is significantly stabilized by newly forming Rh-C and Rh-H bonding interactions.