Formation and Redox Reactivity of Osmium(II) Thionitrosyl Complexes

Reaction between [Os^VI(tpm)(Cl)₂(N)](PF₆) (tpm = tris(1-pyrazolyl)methane) (1) or Os^VI(Tp)(Cl)₂(N) (Tp = hydrotris(1-pyrazolyl)borate anion) (2) and CS₂ + N₃^- in acetone gives the corresponding thionitrosyl complexes, ^-SCN, and N₂. There is an extensive reactivity chemistry of the thionitrosyl group in [Os^II(tpm)(Cl)₂(NS)](PF₆) (3b). Reaction between 3b and PPh₃ occurs with S-atom transfer to give [Os^IV(tpm)(Cl)₂(NPPh₃)]⁺ and SPPh₃. 3b undergoes chemical or electrochemical reduction to give the corresponding Os^II ammine complex and H₂S. O-atom transfer from ONMe₃ to 3b occurs to give Os^III(tpm)(Cl)₂(NSO). Competitive NO⁺/NS⁺ exchange and S^2- transfer occur in the reaction between [Os^II(tpm)(Cl)₂(NS)](BF₄) (3c) and NO⁺ to give a mixture of [Os^VI(tpm)(Cl)₂(N)]⁺ and [Os^II(tpm)(Cl)₂(NO)]⁺.