Catalytic electro-oxidation of water is linked with the oxidation of toluene. The catalyst, Ru(acac)(3) acts as a reversible mediator. Controlled potential electrolysis of water with Ru(acac)(3) at 1.35-1.5V in the presence of toluene, yields bitolyl and benzyltoluene in small amounts. Toluene coupling takes place at least 1V below the overpotential for its direct electro-oxidation and is best explained as caused by electrogenerated radicals.