Metal–ligand cooperative κ1-N-pyrazolate Cp*RhIII-catalysts for dehydrogenation of dimethylamine-borane at room temperature

Abstract

3,5-Dimethylpyrazole (Pz*H) in well-defined Cp*Rh^III (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) complexes, or as an additive to [Cp*RhCl₂]₂ enhances catalytic activity in the dehydrogenation of dimethylamine-borane (DMAB) at room-temperature. Mechanistic studies indicate that the Lewis acidic Rh^III-centre and dangling N-atom of the Pz* fragment operate cooperatively in accepting a hydride and proton from DMAB, respectively, leading directly to dimethylamino-borane and a Rh^III–H complex. The rate limiting step involves protonation of the Rh^III–H by the proximal NH fragment of the Pz*H moiety.