Boryl-Mediated Reversible H₂ Activation at Cobalt: Catalytic Hydrogenation, Dehydrogenation, and Transfer Hydrogenation

We describe the synthesis of a cobalt­(I)–N₂ complex (<b>2</b>) supported by a meridional bis-phosphino-boryl (PBP) ligand. Complex <b>2</b> undergoes a clean reaction with 2 equiv of dihydrogen to afford a dihydrido­borato­cobalt dihydride (<b>3</b>). The ability of boron to switch between a boryl and a dihydrido­borate conformation makes possible the reversible conversion of <b>2</b> and <b>3</b>. Complex <b>3</b> reacts with HMe₂N–BH₃ to give a hydrido­borane cobalt tetra­hydrido­borate complex. We explore this boryl–cobalt system in the context of catalytic olefin hydrogenation as well as amine–borane dehydrogenation/transfer hydrogenation