Dilacunary decatungstates functionalized by organometallic ruthenium(II), [{Ru(C6H6)(H2O)}{Ru(C6H6)}(γ-XW10O36)]4- (X = Si, Ge)

The benzene-Ru(II)-supported dilacunary decatungstosilicate [{Ru(C6H6)(H2O)}{Ru(C6H6)}(gamma-SiW10O36)](4-) and the isostructural decatungstogermanate [{Ru(C6H6)(H2O)}{Ru(C6H6)}(gamma-GeW10O36)](4-) have been synthesized and characterized by multinuclear solution NMR, IR, elemental analysis, and electrochemistry. Single-crystal X-ray analysis was carried out on K-4[{Ru(C6H6)(H2O)}{Ru(C6H6)}(gamma-SiW10O36)]center dot 9H(2)O (K-1), which crystallizes in the orthorhombic system, space group Pmn2(1), with a = 13.6702(3) angstrom, b = 16.2419(4) angstrom, c = 12.1397(2) angstrom, and Z = 2, and on K-4[{Ru(C6H6)(H2O)}{Ru(C6H6)}(gamma-GeW10O36)]center dot 7H(2)O (K-2), which also crystallizes in the orthorhombic system, space group Pmn2(1), with a = 13.6684(12) angstrom, b = 16.297(2) angstrom, c = 12.1607(13) angstrom, and Z = 2. Polyanions 1 and 2 consist of a Ru(C6H6)(H2O) group and a Ru(C6H6) group linked to a dilacunary (gamma-XW10O36) Keggin fragment resulting in an assembly with idealized Cs symmetry. The Ru(C6H6)(H2O) group is bound at the lacunary polyanion site via two Ru-O(W) bonds, whereas the Ru(C6H6) group is bound on the side via three Ru-O(W) bonds. Polyanions 1 and 2 were synthesized in aqueous acidic medium at pH 2.5 by the reaction of [Ru(C6H6)Cl-2](2) with [gamma-SiW10O36](8)(-) and [gamma-GeW10O36](8-), respectively. The formal potentials are roughly the same for the first W waves of 1 and 2. However, important differences appear for the second W waves. These observations indicate different acid-base properties for the reduced forms of 1 and 2. Three oxidation processes were detected: the oxidation of the Ru center is followed first by irreversible electrocatalytic processes of the Ru-benzene moiety and then of the electrolyte. Comparison of this behavior with that of the precursor reagent, [Ru((CH6)-H-6)Cl-2](2), was useful to understand the main oxidation processes. A ligand substitution reaction was observed upon addition of dimethyl sulfoxide (dmso) to 1, 2, or [Ru(C6H6)Cl-2](2). This reaction facilitates substantially the oxidation of the Ru center. The dmso was oxidized with large electrocatalytic currents more efficiently in the presence of 1 and 2 than with [Ru(C6H6)Cl-2](2).