Redox-Neutral S-nitrosation Mediated by a Dicopper Center.

A redox-neutral S-nitrosation of thiol has been achieved at a dicopper(I,I) center. Treatment of dicopper (I,I) complex with excess NO. and thiol generates a dicopper (I,I) di-S-nitrosothiol complex [CuI CuI (RSNO)2 ]2+ or dicopper (I,I) mono-S-nitrosothiol complex [CuI CuI (RSNO)]2+ , which readily release RSNO in 88-94 % yield. The S-nitrosation proceeds by a mixed-valence [CuII CuIII (μ-O)(μ-NO)]2+ species, which deprotonates RS-H at the basic μ-O site and nitrosates RS- at the μ-NO site. The [CuII CuIII (μ-O)(μ-NO)]2+ complex is also competent for O-nitrosation of MeOH. A rare [CuII CuII (μ-NO)(OMe)]2+ intermediate was isolated and fully characterized, suggesting the S-nitrosation may proceed through the intermediary of analogous [CuII CuII (μ-NO)(SR)]2+ species. This redox- and proton-neutral S-nitrosation process is the first functional model of ceruloplasmin in mediating S-nitrosation of external thiols, with implications for biological copper sites in the interconversion of NO. /RSNO.