Synthesis, Characterization, and Electrochemistry ofcis-Oxothio- andcis-Bis(thio)tungsten(VI) Complexes of Hydrotris(3,5-dimethylpyrazol-1-yl)borate Academic Article uri icon


  • The complexes TpWO2X react with sulfiding agents such as B2S3 or P4S10 to give the oxothio- and bis(thio)tungsten(VI) complexes TpWOSX (X = Cl(-)) and TpWS2X [X = Cl(-), S2PPh2(-); Tp = hydrotris(3,5-dimethylpyrazol-1-yl)borate]. The reaction of TpWS2Cl with (i) PPh3 in pyridine and (ii) dimethyl sulfoxide affords TpWOSCl in good overall yield. The chloro complexes undergo metathesis with alkali metal salts to yield species of the type TpWOSX and TpWS2X [X = OPh(-), SPh(-), SePh(-), (-)-mentholate]. The diamagnetic complexes exhibit NMR spectra indicative of C(1) (TpWOSX) or C(s) (TpWS2X) symmetry and IR spectra consistent with terminal oxo and thio ligation (nu(W=O), 940-925 cm(-1); nu(W=S) or nu(WS2), 495-475 cm(-1)). Crystals of (R,S)-TpWOS[(-)-mentholate] are monoclinic, space group P2(1), with a = 11.983(2) A, b = 18.100(3) A, c = 13.859(3) A, beta = 91.60(2) degrees, V = 3004.6(8) A(3), and Z = 4. Crystals of TpWS2(OPh)-CH2Cl2 are orthorhombic, space group Pbca, with a = 16.961(4) A, b = 33.098(7) A, c = 9.555(2) A, V = 5364(2) A(3), and Z = 8. The mononuclear, distorted-octahedral tungsten centers are coordinated by a tridentate Tp ligand, an alkoxy or aryloxy ligand, and two terminal chalcogenide ligands. The average W=O and W=S distances are 1.726(7) and 2.125(2) A, respectively, and the O=W=S and S=W=S angles 102.9(3) and 102.9(1) degrees, respectively. The tungsten and sulfur X-ray absorption spectra of TpWOSCl and TpWS2Cl are consistent with the presence of terminal pi-bonded thio ligands in both complexes. The thio complexes generally undergo a reversible one-electron reduction at potentials significantly more positive than their oxo analogues. The chemical, spectroscopic, and electrochemical properties of the complexes are heavily influenced by the presence of W=S pi frontier orbitals.

publication date

  • August 2001