Thiol and H2S-Mediated NO Generation from Nitrate at Copper(II)

Reduction of nitrate is an essential, yet challengingchemicaltask required to manage this relatively inert oxoanion in the environmentand biology. We show that thiols, ubiquitous reductants in biology,convert nitrate to nitric oxide at a Cu-(II) center under mild conditions.The beta-diketiminato complex [Cl2NNF6]-Cu-(kappa(2)-O2NO) engages in O-atom transfer with variousthiols (RSH) to form the corresponding copper-(II) nitrite [Cu-II]-(kappa(2)-O2N) and sulfenic acid (RSOH).The copper-(II) nitrite further reacts with RSH to give S-nitrosothiols RSNO and [Cu-II](2)(mu-OH)(2) en route to NO formation via [Cu-II]-SR intermediates. The gasotransmitter H2S also reducesnitrate at copper-(II) to generate NO, providing a lens into NO3 (-)/H2S crosstalk. The interactionof thiols with nitrate at copper-(II) releases a cascade of N- andS-based signaling molecules in biology.