Molybdenum Catalyzed Ammonia Borane Dehydrogenation: Oxidation State Specific Mechanisms

[Image: see text] Though numerous catalysts for the dehydrogenation of ammonia borane (AB) are known, those that release >2 equiv of H(2) are uncommon. Herein, we report the synthesis of Mo complexes supported by a para-terphenyl diphosphine ligand, 1, displaying metal–arene interactions. Both a Mo(0) N(2) complex, 5, and a Mo(II) bis(acetonitrile) complex, 4, exhibit high levels of AB dehydrogenation, releasing over 2.0 equiv of H(2). The reaction rate, extent of dehydrogenation, and reaction mechanism vary as a function of the precatalyst oxidation state. Several Mo hydrides (Mo(II)(H)(2), [Mo(II)(H)](+), and [Mo(IV)(H)(3)](+)) relevant to AB chemistry were characterized.