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

High Resolution Image Download MS PowerPoint Slide The diverse redox transformations of nitrite (NO 2 – ) 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]–NO x complexes to illustrate nitrogen-oxide redox chemistry, including conversions between nitrite, NO, and nitrate. Reduction of [(Me 2 PzQu) 2 Ni II (nitrite)](ClO 4 ) 1-Qu by p -methylthiophenol ( Me ArSH) leads to a {NiNO} 10 species [(Me 2 PzQu)Ni(NO)(ClO 4 )] 3-Qu through the intermediacy of HNO 2 and Me ArSNO. 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 H 2 S and nitrite at the nickel(II) site also results in reductive nitrosylation to afford the {NiNO} 10 species. Although the detection of transient HNO 2 is challenging, this study uniquely employs a phosphine-mediated deoxygenation strategy to demonstrate intermediacy of HNO 2 during thiol reactions of [(Me 2 PzQu) 2 M II (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 [Ni II ]–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/H 2 S crosstalk and demonstrate a stepwise OAT-dependent route for NO/nitrite oxidation using a common coordination motif.