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 [Cu I Cu I (RSNO) 2 ] 2+ or dicopper (I,I) mono‐ S ‐nitrosothiol complex [Cu I Cu I (RSNO)] 2+ , which readily release RSNO in 88–94 % yield. The S ‐nitrosation proceeds by a mixed‐valence [Cu II Cu III (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 [Cu II Cu III (μ‐O)(μ‐NO)] 2+ complex is also competent for O ‐nitrosation of MeOH. A rare [Cu II Cu II (μ‐NO)(OMe)] 2+ intermediate was isolated and fully characterized, suggesting the S ‐nitrosation may proceed through the intermediary of analogous [Cu II Cu II (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.