Molybdenum Catalyzed Ammonia Borane Dehydrogenation: Oxidation State Specific Mechanisms

Though numerous catalysts for the dehydro­gen­ation of ammonia borane (AB) are known, those that release >2 equiv of H2 are uncommon. Herein, we report the synthesis of Mo complexes supported by a para-ter­phenyl diphosphine ligand, 1, displaying metal–arene interactions. Both a Mo0 N2 complex, 5, and a MoII bis­(acetonitrile) complex, 4, exhibit high levels of AB de­hy­dro­genation, releasing over 2.0 equiv of H2. The reaction rate, extent of dehydrogenation, and reaction mechanism vary as a function of the precatalyst oxidation state. Several Mo hydrides (MoII­(H)2, [MoII(H)]+, and [MoIV(H)3]+) relevant to AB chemistry were characterized.