Dehydrocoupling Reactions of Dimethylamine-Borane by Pt(II) Complexes: A New Mechanism Involving Deprotonation of Boronium Cations

Coordinatively unsaturated Pt(II) complex [Pt(ItBu′)(ItBu)]+ stabilized by N-heterocyclic carbene (NHC) ligands dehydrogenates N,N-dimethylamineborane through a mechanism that involves hydride abstraction, assisted by an amine, to yield a platinum-hydride complex [PtH(ItBu′)(ItBu)] with concomitant formation of the boronium cation [(NHMe2)2BH2]+. This latter species is very likely in equilibrium with the THF stabilized borenium cation [(NHMe2)(THF)BH2]+, bearing an acidic NH group that is able to protonate the platinum hydride [PtH(ItBu′)(ItBu)] releasing H2, the amino borane H2B-NMe2 and regenerating the catalytic [Pt]+ species.