New perspectives on the reactions of metal nitrosyls with thiolates as nucleophiles

The susceptibility of the nitrosonium ligand (NO+) of metal nitrosyls to nucleophilic attack has been reviewed. The reactions of nitroprusside with thiolate (RS-) nucleophiles (H2S, cysteine, glutathione, N-acetylcysteine and others) have been covered, albeit the main focus is on the reactivity of ruthenium nitrosyl ammines (trans-[Ru(NH3)4(L)NO+]n+) with cysteine and glutathione. Kinetic aspects and reaction products are discussed. Nitric oxide (NO) and nitroxyl (HNO) are the primary and main nitrogen-based products of the reactions with RS-. The final nitrogen based product N2O is identified and suggested as the direct product from the dimerization reaction of HNO. The accumulated data strongly suggest that the ratio of [NO]/[HNO] formed is dependent on the [RS-]/[RSH] ratio, which can be controlled by the experimental conditions. Some aspects of thiol-responsive nitric oxide-releasing materials are also discussed.