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 SO32- to H2S using eight protons (SO32- + 8H(+) + 6e(-) -> H2S + 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)(mu-Cl)(mu-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 H2S from the disulfide-bridged complex was achieved.

Automated summary

Sulfite reduction is a crucial process in the global sulfur cycle, and it can be achieved using transition-metal complexes. In our study, we successfully simulated and achieved the stepwise reduction of sulfite from sulfite to sulfur monoxide, then to disulfide, and finally to hydrogen sulfide using a dinuclear ruthenium complex.