Perthionitrite-Induced Persulfidation in Binuclear Cobalt(II) Complexes§

Persulfidation of sulfhydryl functional group (-SH) in protein and nonprotein thiols is a physiologically important process and generally involves the reduction of a partially oxidized sulfur by a fully reduced sulfur. In the present work, two dicobalt(II)-nitrito complexes, [Co2(PhBIMP)(μ-NO2)(DMF)]2+ (2) and [Co2(PhBIMP)(μ-NO2)2]1+ (3), have been demonstrated to react with RC(O)SH (R = Me, Ph) to generate the persulfidated complexes, [Co2(PhBIMP)(μ-SSC(O)R)]2+ (R = Me, 5a; Ph, 5b) in high yields (65-72%) along with nitric oxide (71-80%). Characterization of all the products and intermediates by structural and spectroscopic methods, and comparison of the results with those obtained from control experiments, established the generation of [Co2(PhBIMP)(μ-SC(O)R)(MeCN)]2+ (R = Me, 4a; Ph, 4b) and perthionitrite (SSNO-) in the reactions of 2/3 with RC(O)SH, followed by persulfidation of the coordinated thiocarboxylate (RC(O)S-) in 4a and 4b by the in situ generated SSNO- to produce the persulfidated complexes, 5a and 5b, respectively. The present work thus demonstrates, for the first time, that SSNO-, a physiologically relevant S/N-crosstalk species, can effectively mediate the persulfidation of sulfhydryl functional groups and may implicate a similar, but hitherto unknown, role of SSNO- in biological persulfidation processes.