Reduction of Nitrite to NO on a Molybdenum–Thiolate Platform and Protonation of the Anionic Nitrosyl Complex

We report nitrite-to-NO reduction using Mo(P^S^S)₂ (<b>1</b>, where P^S^S = PhP(<i>o</i>-C₆H₄S^-)₂), and explore the protonation of the resulting anionic Mo(IV)-NO complex (<b>2</b>) as a potential for further transformations. In the absence of benzenethiol as an external reductant, both the molybdenum center and the phosphine donor in <b>1</b> serve as internal oxygen-atom acceptors, resulting in the formation of Mo(VI)-oxo (<b>3</b>), Mo(IV)-NO (<b>2</b>), and phosphoryl-ligated Mo(IV)-NO (<b>4</b>) complexes, all of which are structurally characterized. Notably, the anionic Mo(IV)-NO complex undergoes sulfur protonation, as demonstrated by the isolation of a rare S···H-N hydrogen-bonded intermediate [(NO)Mo(P^S^S)₂][HLut] (<b>5</b>), and the protonated complex (P^S^S)Mo(NO)(P^S^SH) (<b>6</b>).