Theoretical Studies of Transition-metal Methyl Ions, Mch₃⁺(m = Sc, Cr, Mn, Zn, Y, Mo, Tc, Pd, Cd)

Selected transition-metal methyl cations have been studied by using ab initio generalized valence bond and configuration interaction methods. We present equilibrium geometries and bond dissociation energies and analyze the character of the wave function for the ground-state MCH₃⁺species. The present calculations are compared with previous studies of the corresponding MH⁺molecules. MCH₃⁺is similar to MH⁺from the standpoint of orbital hybridization, electron transfer, bond orbital overlap, and bond dissociation energy. Thus, we find bond energy differences Z)(M⁺-CH₃) - D(M⁺-H), ranging from -3.6 kcal/mol for M = Mo to +6.0 kcal/mol for M = Zn, whereas the total bond energy is calculated to range from 24 to 60 kcal/mol. Experimental estimates suggest that Z)(M⁺-CH₃) is, on the average, about 6 kcal/mol larger than Z)(M⁺-H).