Sixth Ligand Induced HNO/NO^– Release by a Five-Coordinated Cobalt(II) Nitrosyl Complex Having a {CoNO}⁸ Configuration

Nitroxyl (HNO) and nitroxide (NO^–) anion, the one-electron-reduced form of nitric oxide (NO), have been shown to have distinct advantages over NO from pharmacological and therapeutic points of view. However, the role of nitroxyl in chemical biology has not yet been studied as extensively as that of NO. Consequently, only a few examples of HNO donors such as Angeli’s salt, Piloty’s acid, or acyl- and acyloxynitroso derivatives are known. However, the intrinsic limitations of all of these hinder their widespread utility. Metal nitrosyl complexes, although few examples, could serve as an efficient HNO donor. Here, a cobalt nitrosyl complex of the {CoNO}⁸ (1) configuration has been reported. This complex in the presence of a sixth ligand [BF₄^–, DTC^– (diethyldithiocarbamate anion), or imidazole] releases/donates HNO/NO^–. This has been confirmed using well-known HNO/NO^– acceptors like [Fe­(TPP)­Cl] and [Fe­(DTC)₃]. The HNO release has been authenticated further by the detection and estimation of N₂O using gas chromatography–mass spectroscopy as well as its reaction with PPh₃.