Computational study of methane functionalization by a multiply bonded, Ni-bis(phosphine) complex

A computational chemistry study of nickel-catalyzed group transfer to methane is presented. Two mechanisms were evaluated: a one-step mechanism involving [1+2] insertion of E into the C–H bond of methane, and a two-step [2π + 2σ] mechanism involving addition of the C–H bond of methane across the Nidouble bond; length as m-dashE bond to a square planar NiII intermediate, followed by C–E reductive elimination. Analysis of the energetics for the different mechanistic steps implies a possible competition between the two mechanisms for carbene transfer. For nitrene transfer, the [1+2] pathway is predicted to be the preferred route. Finally, for phosphinidene transfer, the [2π + 2σ] mechanism is calculated to be the preferred mechanism. The two mechanisms studied – [1+2] and [2π + 2σ] – entail exothermic individual reactions, coupled with reasonable enthalpic barriers. Furthermore, regeneration of the catalyst active species by reaction with a group transfer reagent XE is highly exothermic. The calculations thus indicate that (P ∼ P)Nidouble bond; length as m-dashE (P ∼ P denotes a chelating bis-phosphine ligand) deserve consideration as plausible starting points in the search for improved hydrocarbon functionalization catalysts.