Mechanisms and Reactivity of Tl(III) Main-Group-Metal–Alkyl Functionalization in Water

Metal-mediated C–H activation reactions generate metal–alkyl intermediates that can be converted into carbon–oxygen bonds through functionalization reactions. While the mechanisms and reactivity of C–H activation reactions have been well studied for transition-metal complexes, much less is known about functionalization reactions, especially for main-group-metal–alkyl complexes. Here we report density functional theory calculations on the reaction thermodynamics and kinetic pathways for main-group, p-block-metal Tl^III–methyl functionalization reactions in water using a combination of continuum and explicit/continuum solvent models. Specifically, we examined the oxygen functionalization of (OAc)­Tl^III(CH₃)₂ and (OAc)₂Tl^III(CH₃) in water where in both cases functionalization gives methyl acetate and methanol. Our calculations suggest that (OAc)­Tl^III(CH₃)₂ is thermodynamically and kinetically stable against bond homolysis, heterolysis, protonolysis, and all reductive functionalization pathways. Functionalization is only possible after methyl anion group transfer to Tl^III(OAc)₃ to give (OAc)₂Tl^III(CH₃). Our calculations suggest that this monomethyl structure is functionalized by acetate dissociation to give a Tl monocation and then a one-step nucleophilic functionalization where water and acetate have competitive transition states.