Thiocarboxylate and Acid Chloride Mediated Generation of Nitric Oxide from a Dinickel(II)-Bis(ONO) Complex Involving the Formation of Perthionitrite and O-Nitrosyl Carboxylate

A detailed study for the generation of nitric oxide (NO) upon reaction of a binuclear Ni(II)-bis(ONO) complex with carboxylic acids (RCOOH, R = Me, Ph), thiols (RSH, R = Ph, <i>p</i>-F-C₆H₄), benzeneselenol (PhSeH), thiocarboxylates (RC(O)S^-, R = Me, Ph), thiocarboxylic acids (RC(O)SH, R = Me, Ph), and acid chlorides (RC(O)Cl, R = Me, Ph) has been presented. The reactions of the binuclear Ni(II)-bis(ONO) complex with thiols/selenols give access to unusual dinickel(II)-nitrito-thiolato/selenolato complexes, while the reactions with RC(O)S^-, RC(O)SH, and RC(O)Cl offer new mechanistic insights into the generation of perthionitrite (SSNO^-) and <i>O</i>-nitrosyl carboxylates (RC(O)ONO), the well-known NO-carrying species in biology. Interestingly, while the reaction of the binuclear Ni(II)-bis(ONO) complex with RC(O)S^- involved nucleophilic attack of the latter to the coordinated NO₂^- to generate SSNO^-, the reaction with RC(O)Cl proceeds via the hitherto unknown nucleophilic attack of the coordinated NO₂^- to the carbonyl carbon of RC(O)Cl to generate RC(O)ONO, which, in turn, produces NO. The present comparative study thus demonstrates new reactions of metal-coordinated NO₂^- and detailed mechanistic investigations supported by molecular structure determinations and spectroscopic studies and establishes the hitherto unknown reaction of coordinated nitrite with RC(O)Cl to be a highly efficient method for the generation of NO in excellent yield.