Nitrite Reduction Cycle on a Dinuclear Ruthenium Complex Producing Ammonia

The fundamental biogeochemical cycle of nitrogen includes cytochrome c nitrite reductase, which catalyzes the reduction of nitrite ions to ammonium with eight protons and six electrons (NO2– + 8H+ + 6e– → NH4+ + 2H2O). This reaction has motivated researchers to explore the reduction of nitrite. Although a number of electrochemical reductions of NO2– have been reported, the synthetic nitrite reduction reaction remains limited. To the best of our knowledge, formation of ammonia has not been reported. We report a three-step nitrite reduction cycle on a dinuclear ruthenium platform {(TpRu)2(μ-pz)} (Tp = HB(pyrazol-1-yl)3), producing ammonia. The cycle comprises conversion of a nitrito ligand to a NO ligand using 2H+ and e–, subsequent reduction of the NO ligand to a nitrido and a H2O ligand by consumption of 2H+ and 5e–, and recovery of the parent nitrito ligand. Moreover, release of ammonia was detected.