title: Structural characterization and unusual reactivity of oxosulfido-Mo(V) compounds: implications for the structure and electronic description of the very rapid form of xanthine oxidase.
abstract: The first structural characterization of a mononuclear, EPR-active, oxosulfido-Mo(V) compound related to the very rapid form of xanthine oxidase (VR-XnO) is reported. The compound, [CoCp2][Tp(iPr)Mo(V)OS(2-OC6H4CO2Et)] [Cp = cyclopentadienyl; Tp(iPr) = hydrotris(3-isopropylpyrazol-1-yl)borate], exhibits a distorted octahedral geometry with Mo═O and Mo=/--S distances of 1.761(5) and 2.215(2) Å, respectively, and an O═Mo=/--S angle of 107.33(14)°. Significantly, the Mo(V)=/--S distance is much shorter than the value of 2.36 Å reported for oxosulfido-Mo(V) compounds (Singh, R.; et al. Inorg. Chem. 1989, 28, 8) but close to the range established for VR-XnO by protein crystallography. The methyl and phenyl esters were also prepared but the latter is highly reactive and undergoes an intramolecular, radical-based cyclization/elimination reaction to form [CoCp2][Tp(iPr)Mo(IV)O{2-OC6H4C(O)S-κO,κS}]. This study provides the first definitive measurement of the Mo(V)=/--S bond distance in an unambiguously characterized oxosulfido-Mo(V) compound and supports the presence of a short (ca. 2.22 Å) Mo=/--S bond in VR-XnO. It also demonstrates that the Mo(V)=/--S moiety participates in radical-based reactions that are facilitated by the facile redox interplay of Mo and S and by substrates susceptible to radical eliminations.
authors: School of Chemistry, University of Melbourne, Melbourne, Victoria 3010, Australia.
authors: Victor W L
authors: VW
authors: Ng
authors: Jonathan M
authors: JM
authors: White
authors: Charles G
authors: CG
authors: Young
mesh_terms: D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D008958:Models, Molecular; D008982:Molybdenum / Q000737:chemistry*; D010084:Oxidation-Reduction; D017601:Oxygen Compounds / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D014969:Xanthine Oxidase / Q000737:chemistry*
chemical_list: D017601:Oxygen Compounds; D013440:Sulfides; D008982:Molybdenum; D014969:Xanthine Oxidase