N2-to-NH3 Conversion by a triphos-Iron Catalyst and Enhanced Turnover under Photolysis

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-NH3 conversion. Herein, we describe the synthesis and characterization of new (P2Fe)-Fe-P'Ph(N-2)(H)(x) systems that are active for catalytic N-2-to-NH3 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.