Electrophilic Impact of High-Oxidation State Main-Group Metal and Ligands on Alkane C-H Activation and Functionalization Reactions

High-oxidation state main-group metal complexes are potential alternatives to transition metals for electrophilic alkane C-H functionalization reactions. However, there is little known about how selection of the p-block, main-group metal and ligand impact alkane C-H activation and functionalization thermodynamics and reactivity. This work reports density functional theory calculations used to determine qualitative and quantitative features of C-H activation and metal-methyl functionalization energy landscapes for reaction between high-oxidation state d¹⁰s⁰ In^III, Tl^III, Sn^IV, and Pb^IV carboxylate complexes with methane. While the main-group metal influences the C-H activation barrier height in a periodic manner, the carboxylate ligand has a much larger quantitative impact on C-H activation with stabilized carboxylate anions inducing the lowest barriers. For metal-methyl reductive functionalization reactions, the main-group metal dramatically influences the barrier heights, which are correlated to reaction thermodynamics and bond heterolysis energies as a model for two-electron reduction energies. Overall, this work begins to outline which main-group metals and carboxylate ligands could be useful for alkane functionalization systems that utilize electrophilic C-H activation and metal-alkyl functionalization reactions.