Redox Interplay of Oxo−Thio−Tungsten Centers with Sulfur-Donor Co-Ligands

The oxo−thio−W(VI) complexes Tp*WOS(S₂PR₂-S) and Tp*WOS(pyS-S) (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate, R = OEt, Ph; pyS = pyridine-2-thiolate) have been prepared and characterized by microanalytical, spectroscopic, and structural techniques. Crystals of the 1,2-dichloroethane hemisolvate of Tp*WOS(S₂PPh₂-S) belong to the triclinic space group P1̄ with a = 10.732(6) Å, b = 16.91(1) Å, c = 10.021(4) Å, α = 104.40(4)°, β = 107.52(3)°, γ = 96.09(5)°, V = 1647(1) ų for Z = 2. The complex exhibits a distorted octahedral structure featuring a facial tridentate Tp* ligand and mutually cis terminal oxo (W−O(1) = 1.712(7) Å), terminal thio (W−S(1) = 2.162(3) Å), and monodentate dithiophosphinate ligands. X-ray absorption and extended X-ray absorption fine structure results support a related oxo−thio formulation for Tp*WOS(pyS-S). The complexes are reduced to the corresponding oxo−thio−W(V) anions, [Tp*WOS(S₂PR₂-S)]^- and [Tp*WOS(pyS-S)]^-, which exhibit highly anisotropic EPR spectra. They are oxidized to form the EPR-active (dithio)oxo−W(V) cations, [Tp*WO(S₃PR₂-S,S‘)]⁺ and [Tp*WO(pyS₂-N,S)]⁺ (pyS₂ = pyridine-2-dithio). Green [Tp*WO(pyS₂-N,S)]BF₄, formed in the reaction of Tp*WOS(pyS) and NOBF₄, has been isolated and spectroscopically and structurally characterized. Crystals of [Tp*WO(pyS₂-N,S)]BF₄ belong to the monoclinic space group Cc with a = 16.007(5) Å, b = 14.091(4) Å, c = 13.608(4) Å, β = 124.525(4)°, V = 2528.8(13) ų for Z = 4. The cation exhibits a distorted octahedral structure featuring facial tridentate Tp*, terminal oxo (W−O(1) = 1.632(12) Å), and bidentate pyridine-2-dithio-N,S (W−S(1) = 2.317(7) Å, S(1)−S(2) = 2.037(9) Å) ligands. The structures and redox behavior of the complexes are compared and contrasted with those of the related molybdenum complexes, Tp*Mo^VIOS(S₂PR₂-S) and Tp*Mo^IVO(pyS₂-N,S) (Hill, J. P.; Laughlin, L. J.; Gable, R. W.; Young, C. G. Inorg. Chem. 1996, 35, 3447).