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.