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 (1, where P^S^S = PhP(o-C₆H₄S^-)₂), and explore the protonation of the resulting anionic Mo(IV)-NO complex (2) as a potential for further transformations. In the absence of benzenethiol as an external reductant, both the molybdenum center and the phosphine donor in 1 serve as internal oxygen-atom acceptors, resulting in the formation of Mo(VI)-oxo (3), Mo(IV)-NO (2), and phosphoryl-ligated Mo(IV)-NO (4) 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] (5), and the protonated complex (P^S^S)Mo(NO)(P^S^SH) (6).