No abstract

Crystals of the title compound, Ph4As+ [MoO(SPh)4]-, belong to the triclinic space group Pī with cell dimensions a 12.623(8), b 14.295(7), c 14.301(9) Ǻ, α 94.43(4), β 111.43(5), γ 65.70(4)° and Z2. The structure has been refined with diffractometer data measured with Mo Kα radiation to give a conventional R factor of 0.056 for 3215 unique terms. The Mo, As, S and O atoms were refined with anisotropic temperature factors and the C atoms with isotropic factors. The square- pyrimidal [MoO(SPh)4]- anion has the Mo atom lying 0.82 Ǻ from the basal plane of the four S atoms with Mo-O 1.699(9) Ǻ, the mean Mo-S bond lengths 2.403(5) Ǻ and the mean S...S distance 3.20(3) Ǻ. The geometry about the As atom in the Ph4As+ cation is regular tetrahedral, the mean As-C bond length being 1.91(1) Ǻ.

1959that the exchangeable oxygen is an "in-plane" rather than an "axial" ligand.[98MoO(SePh)4]-and [98MoOC14(MeCN)]-enriched with 24.9 atom % "0, presumably due to their intrinsically broader line widths (Table VI) and insufficient enrichment. The observation34*35 of I7O superhyperfine coupling of about (8-16) X lo4 cm-~ in the m o~y~o e n z y m e s xanthine oxidase, xanthine dehydrogenase, and sulfite oxidase in 170H2 demonstrates the dination sphere. The magnitude of the coupling constants suggest Acknowledgment. Dr. J. R. Pilbrow and Dr. A. Edgar are thanked for their provision of computer simulation procedures and Q-band frequency measurements, respectively. A.G.W. thanks while G.R.H. acknowledges the award of a La Trobe University Postgraduate scholarshiD. K.S.M. acknowledges support from presence of an exchangeable oxygen in the molybdenum the Australian Research Grants Committee for financial support the iustralian Researih Grants Committee and a Monash University Special Research Grant. The assistance of Messrs. K. J. Berry and L. Mitchell with magnetic susceptibility measurements is gratefully acknowledged. (34) Gutteridge, S.; Malthouse, J. P. G.; Bray, R. C. J. Znorg. Biochem. (35) Cramer, S. P.; Johnson, J. L.; Rajagopalan, K. v.; Sorrell, T. M. 1979, 11, 355-360. Abstract: The rich electrochemistry of the mononuclear [MVO(XR),]-and triply bridged binuclear [MV202(XR)6z]"-anions (M = Mo, W; X = S, Se; R = Ph, p-tolyl, CH,Ph; Z = uninegative (n = 1) or neutral (n = 0) ligand) is explored in MeCN and DMF at platinum and mercury electrodes over the temperature range +25 to -60 OC. Interconversion of the mononuclear and binuclear forms occurs via reduction and oxidation processes involving the metal and ligand centers. Stepwise reduction of the binuclear MV2 to MlVqv2 and MIV2 species is observed, and the reduced forms undergo chemical reactions which lead to the appearance of 1 molecule of [MNO(XR)4]2-/molecule of [MV202(XR)6z]-reduced. In this way, the alkyl-substituted [MoO(SCH~P~)~]~-/-ions can be generated at 25 OC. Chemically reversible, one-electron reduction of [MVO(XR),]-is observed, while oxidation leads to the formation of [MV202(XR),Z] (Z = solvent) and RXXR via a process involving oxidative dissociation of ligand XR-. For [WVO(XR),]-, the following one-electron couples are observed: [WV'O(XR),] + e-= [WVO(XR),]-+ e-= [WN0(XR),I2-. In view of the direct observation of [Wv1O(XR),], an intramolecular redox step is apparently involvedin the overall oxidation process described above. Wider implications of the ligand redox processes are discussed.

No abstract

No abstract