Redox‐Neutral S‐nitrosation Mediated by a Dicopper Center

Abstract

An redox-neutral S -nitrosation of thiol has been achieved at 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 reaction proceeds through 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 the 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, which is isoelectronic to thiol. In this case, a rare [Cu II Cu II ( μ -NO)(OMe)] 2+ intermediate has been isolated and fully characterized, suggesting the S -nitrosation proceeds through the intermediary of analogous [Cu II Cu II ( μ -NO)(SR)] 2+ species. The redox- and proton-neutral S- nitrosation process reported here represents the first functional model of ceruloplasmin in mediating S -nitrosation of external thiols, adding further implications for biological copper sites in the interconversion of NO • /RSNO.