Stepwise Sulfite Reduction on a Dinuclear Ruthenium Complex Leading to Hydrogen Sulfide.

Sulfite reduction by dissimilatory sulfite reductases is a key process in the global sulfur cycle. Sulfite reductases catalyze the 6e - reduction of SO 3 2- to H 2 S using eight protons (SO 3 2- + 8H + + 6e - → H 2 S + 3H 2 O). However, detailed research into the reductive conversion of sulfite on transition-metal-based complexes remains unexplored. As part of our ongoing research into reproducing the function of reductases using dinuclear ruthenium complex {(TpRu) 2 (μ-Cl)(μ-pz)} (Tp = HB(pyrazolyl) 3 ), we have targeted the function of sulfite reductase. The isolation of a key SO-bridged complex, followed by a sulfite-bridged complex, eventually resulted in a stepwise sulfite reduction. The reduction of a sulfite to a sulfur monoxide using 4H + and 4e - , which was followed by conversion of the sulfur monoxide to a disulfide with concomitant consumption of 2H + and 2e - , proceeded on the same platform. Finally, the production of H 2 S from the disulfide-bridged complex was achieved.