The rates of substitution of pi-acidic ligands for the aqua ligand in the ruthenium-substituted heteropolytungstate anion (H2O)(RuPW11O395-)-P-II were measured and compared with those of more familiar complexes of Ru(II). The weakly pi-acidic character of the heteropolytungstate anionic ligand produced a decrease in the lability of the aqua ligand. The kinetics of homogeneous electron transfer reactions involving the (H2O)(RuPW11O395-)-P-II anion were complicated by its high charge and tendency to precipitate with cationic oxidants. However, the specific rate of its reduction of O-2 to H2O2 was in good agreement with the value calculated from the Marcus relation. The (RuOH2)-O-III center in (H2O)(RuPW11O394-)-P-III is reversibly oxidizable in two steps to Ru-IV = O and Ru-V = O. The Ru-V = O complex oxidizes benzyl alcohol, methanol and 2-propanol, but the reaction rates are too small to make the complex attractive as an oxidation catalyst.