We prepared a new Ru-2(III, IV) complex containing a pyrophosphate as the dinucleating component, by the reaction between the mononuclear complex [Ru(Me(3)tacn)Cl-3] and Na4P2O7 center dot 10H(2)O in aqueous solution. Cyclic voltammetric measurement for the complex [{Ru(Me(3)tacn)}(2)(mu-O)(mu-P2O7)]PF6 (1) in aqueous solution revealed the formation of two species with higher oxidation states, such as [O=Ru(IV)Ru(IV)=O] and [O=Ru(IV)Ru(V)=O](+). Furthermore, this complex showed activity for water oxidation reaction with Ce(NH4)(2)(NO3)(6) as the chemical oxidant in acidic aqueous solution.