Nitrite Reduction Cycle on a Dinuclear Ruthenium Complex Producing Ammonia

The fundamental biogeochemical cycle of nitrogen includes cytochrome <i>c</i> nitrite reductase, which catalyzes the reduction of nitrite ions to ammonium with eight protons and six electrons (NO₂^– + 8H⁺ + 6<i>e</i>^– → 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 <i>e</i>^–, subsequent reduction of the NO ligand to a nitrido and a H₂O ligand by consumption of 2H⁺ and 5<i>e</i>^–, and recovery of the parent nitrito ligand. Moreover, release of ammonia was detected