Reductive and Oxidative Transformations of Nitrite at Nickel(II): Insights into the Generation, Electronic Structure, and Reactivity of {NiNO}10

Abstract The diverse redox transformations of nitrite (NO2–) link key signaling molecules like nitric oxide (NO) and enable precise regulation of NO flux in physiology. This report employs structurally and spectroscopically characterized mononuclear [Ni]–NOx complexes to illustrate nitrogen-oxide redox chemistry, including conversions between nitrite, NO, and nitrate. Reduction of [(Me2PzQu)2NiII(nitrite)](ClO4) 1-Qu by p-methylthiophenol (MeArSH) leads to a {NiNO}10 species [(Me2PzQu)Ni(NO)(ClO4)] 3-Qu through the intermediacy of HNO2 and MeArSNO. Interestingly, subtle modifications in the ligand properties distinctly influence the thiol–nitrite reactivity and the stability of the resulting {NiNO}10 species. Importantly, the crosstalk between H2S and nitrite at the nickel(II) site also results in reductive nitrosylation to afford the {NiNO}10 species. Although the detection of transient HNO2 is challenging, this study uniquely employs a phosphine-mediated deoxygenation strategy to demonstrate intermediacy of HNO2 during thiol reactions of [(Me2PzQu)2MII(nitrite)]+ (M = Ni/Zn). In addition, NO and NO– ligand transfer reactivity of the {NiNO}10 core in 3-Qu have been evaluated. Using iodosylbenzene (PhIO) as a sacrificial O-atom donor, both 1-Qu and 3-Qu complexes have been shown to yield [NiII]–nitrate 2-Qu, thereby outlining a stepwise O-atom transfer (OAT) pathway for nitrosyl → nitrite → nitrate transformations. Taken together, these findings reveal reductive nitrosylation via nitrite–thiol/H2S crosstalk and demonstrate a stepwise OAT-dependent route for NO/nitrite oxidation using a common coordination motif.