title: Dimerization of mono-ruthenium substituted alpha-Keggin-type tungstosilicate [alpha-SiW11O39RuIII(H2O)]5- to micro-oxo-bridged dimer in aqueous solution: synthesis, structure, and redox studies.
abstract: We report the dimerization of a mono-ruthenium(III) substituted alpha-Keggin-type tungstosilicate [alpha-SiW(11)O(39)Ru(III)(H2O)](5-) to a micro-oxo-bridged dimer [{alpha-SiW(11)O(39)Ru(m)}2O](n-) (m = III, n = 12; m = IV/III, n = 11; m = IV, n = 10). Single crystal X-ray structure analysis of Rb(10)[{alpha-SiW(11)O(39)Ru(IV)}2O].9.5H2O (triclinic, P1, with a = 12.7650(6) A, b = 18.9399(10) A, c = 20.2290(10) A, alpha = 72.876(3) degrees, beta = 88.447(3) degrees, gamma = 80.926(3) degrees, V = 4614.5(4) A(3), Z = 2) reveals that two mono-ruthenium substituted tungstosilicate alpha-Keggin units are connected through micro-oxo-bridging Ru-O-Ru bonds. Solution (183)W-NMR of [{SiW(11)O(39)Ru(IV)}2O](10-) resulted in six peaks (-63, -92, -110, -128, -132, and -143 ppm, intensities 2 : 2 : 1 : 2 : 2 : 2) confirming that the micro-oxo bridged dimer structure is maintained in aqueous solution. The dimerization mechanism is presumably initiated by deprotonation of the aqua-ruthenium complex [alpha-SiW(11)O(39)Ru(III)(H2O)](5-) leading to a hydroxy-ruthenium complex [alpha-SiW(11)O(39)Ru(III)(OH)](6-). Dimerization of two hydroxy-ruthenium complexes produces the micro-oxo bridged dimer [{alpha-SiW(11)O(39)Ru(III)}2O](12-) and a water molecule. The Ru(III) containing dimer is oxidized by molecular oxygen to produce a mixed valence species [{alpha-SiW(11)O(39)Ru(IV-III)}2O](11-), and further oxidation results in the Ru(IV) containing [{alpha-SiW(11)O(39)Ru(IV)}2O](10-).
authors.affiliation: Catalysis Research Center, Hokkaido University, N-21, W-10, 001-0021 Sapporo, Japan. sadakane@cat.hokudai.jp
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sadakane
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tsukuma
authors.forename: Michael H
authors.initials: MH
authors.lastname: Dickman
authors.forename: Bassem S
authors.initials: BS
authors.lastname: Bassil
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kortz
authors.forename: Mickaël
authors.initials: M
authors.lastname: Capron
authors.forename: Wataru
authors.initials: W
authors.lastname: Ueda
mesh_terms: D018360:Crystallography, X-Ray; D019281:Dimerization; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D017975:Ruthenium Compounds / Q000737:chemistry*; D017640:Silicates / Q000138:chemical synthesis / Q000737:chemistry*; D012996:Solutions; D017973:Tungsten Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D017975:Ruthenium Compounds; D017640:Silicates; D012996:Solutions; D017973:Tungsten Compounds; D014867:Water