Theoretical studies of the first- and second-row transition-metal methyls and their positive ions

TLDR

In general, the dissociation energies do not follow simple trends, as the individual D0 values are significantly affected by the relative spacings between the atomic states of the metal. The study determines metal–carbon bond dissociation energies and geometries for first- and second-row transition-metal methyl neutrals and positive ions. Theoretical calculations are performed to obtain D0 values and geometries for the methyl neutrals and positive ions of first- and second-row transition metals. Computed D0 values for positive ions largely agree with experiment, except for RuCH+3, RhCH+3, and PdCH+3, while hydride and methyl positive ions show similar energies across metals except Cu and Ag, and neutral methyls exhibit notably lower D0 values—differences up to 15 kcal/mol—providing a consistent dataset that facilitates critical assessment of experimental data and insight into bonding mechanisms.

Abstract

The metal–carbon bond dissociation energies (D0) and geometries for the first- and second-row transition-metal methyl neutrals and positive ions are determined. The computed D0 values for the positive ions compare favorably with experiment, except for RuCH+3, RhCH+3, and PdCH+3 where the experimental values are 10–15 kcal/mol larger. The computed D0 values for the hydride and methyl positive ions are similar for all metals in both transition rows except for Cu and Ag. However, for the neutral systems the D0 values for the methyls are smaller, especially on the right-hand side of both transition rows where the differences approach 15 kcal/mol. In general, the dissociation energies do not follow simple trends, as the individual D0 values are significantly affected by the relative spacings between the atomic states of the metal. The study of all of the methyl neutral and ions of both transition rows presented here provides a consistent set of data for the dissociation energies, thereby allowing a critical assessment of the experimental data for these molecular species, and an enhanced understanding of the different bonding mechanisms.