Ru II -and Ru III -substituted α-Keggin-type phosphotungstates with a dimethyl sulfoxide (DMSO) ligand, [PW 11 O 39 Ru II DMSO] 5-(1) and [PW 11 O 39 Ru III DMSO] 4-(2), were synthesized. Compound 1 was prepared by reaction of [PW 11 O 39 ] 7with [Ru II (DMSO) 4 ]Cl 2 in water at 125°C under hydrothermal conditions and was isolated as a cesium salt. Compound 2 was prepared by reaction of 1 with bromine in water at 60°C and was isolated as a cesium salt. The compounds were characterized by cyclic voltammetry, elemental analysis, UV/Vis, IR, * Prof. Dr. M. Sadakane

Ruthenium(III)-substituted α-Keggin-type silicotungstates with pyridine-based ligands, [SiW(11)O(39)Ru(III)(Py)](5-), (Py: pyridine (1), 4-pyridine-carboxylic acid (2), 4,4'-bipyridine (3), 4-pyridine-acetamide (4), and 4-pyridine-methanol (5)) were prepared by reacting [SiW(11)O(39)Ru(III)(H(2)O)](5-) with the pyridine derivatives in water at 80 °C and then isolated as their hydrated cesium salts. These compounds were characterized using cyclic voltammetry (CV), UV/Vis, IR, and (1)H NMR spectroscopy, elemental analysis, titration, and X-ray absorption near-edge structure (XANES) analysis (Ru K-edge and L(3)-edge). Single-crystal X-ray analysis of compounds 2, 3, and 4 revealed that Ru(III) was incorporated in the α-Keggin framework and was coordinated by pyridine derivatives through a Ru-N bond. In the solid state, compounds 2 and 3 formed a dimer through π-π interaction of the pyridine moieties, whereas they existed as monomers in solution. CV indicated that the incorporated Ru(III)-Py was reversibly oxidized into the Ru(IV)-Py derivative and reduced into the Ru(II)-Py derivative.

The tetrabutylammonium (TBA) salt of a mono-ruthenium(III)-substituted α-Keggin-type silicotungstate with a 4,4'-bipyridine (bipy) ligand, TBA5[α-SiW11O39Ru(III)(bipy)] (1), which is soluble in various organic solvents, was prepared by a cation exchange reaction of Cs5[α-SiW11O39Ru(III)(bipy)] with tetrabutylammonium bromide. Compound 1 was characterised using IR, (1)H-NMR, elemental analysis, single crystal X-ray analysis, X-ray absorption near-edge structure (XANES) analysis (Ru L3-edge), electron spin resonance (ESR), cyclic voltammetry (CV) and UV-Vis. Single crystal X-ray analysis of 1 revealed that the Ru(III) unit was incorporated into the α-Keggin-type silicotungstate framework and coordinated by a bipy molecule through a Ru-N bond. CV indicated that the incorporated Ru(III)-bipy was reversibly oxidised to the Ru(IV)-bipy derivative and reduced to the Ru(II)-bipy derivative in organic solvents. The redox potential of Ru(IV/III)-bipy was found to be affected by organic solvents. Moreover, the Ru(V)-bipy derivative was observed in acetonitrile.