Bridging iron hydrides are proposed to form at the active site of MoFe-nitrogenase during catalytic dinitrogen reduction to ammonia and may be key in the binding and activation of N_2 via reductive elimination of H_2. This possibility inspires the investigation of well-defined molecular iron hydrides as precursors for catalytic N_2-to-NH_3 conversion. Herein, we describe the synthesis and characterization of new P_2^(P′Ph)Fe(N_2)(H)_x systems that are active for catalytic N_2-to-NH_3 conversion. Most interestingly, we show that the yields of ammonia can be significantly increased if the catalysis is performed in the presence of mercury lamp irradiation. Evidence is provided to suggest that photo-elimination of H_2 is one means by which the enhanced activity may arise.
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