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 -C 6 H 4 S – ) 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 ).