Water Oxidation Catalyzed by a Ruthenium Complex with an Ru–C Bond

We prepared a new Ru(III) complex with a covalent bond between the central Ru and C of the ligand, [RuCl(dpp)(bpy)]Cl ([ 1 ]Cl, dpp=2,6‐dipyridylphenyl, bpy=2,2’‐bipyridine), through the reaction of [( η 6 ‐C 6 H 6 )RuCl(bpy)]Cl with one equivalent of 1,3‐di(pyrid‐2‐yl)benzene. X‐ray analysis of a single crystal of [ 1 ](PF 6 ), which was prepared via the anion exchange of [ 1 ]Cl, revealed the short Ru–C bond length of [ 1 ] + . [ 1 ]Cl was easily hydrolyzed in a neutral water solution to the hydroxo complex, [Ru(OH)(dpp)(bpy)] + ([ 2 ] + ). Cyclic voltammetry of [ 1 ] + showed that the Ru(II)/Ru(III) potential of [ 1 ] + was more negative than that of the 2,2’:6’,2”‐terpyridine (trpy) analogue, [RuCl(bpy)(trpy)](ClO 4 ), by –770 mV under the same conditions. Moreover, the Ru(V)=O species, which is a key intermediate of water oxidation, was produced by electrochemical oxidation of [ 2 ] + at an extremely negative potential (+0.80 V vs. saturated calomel electrode). [ 2 ] + catalyzed water oxidation at pH 2.5 with [Ru(bpy) 3 ] 3+ as the oxidant. 2,6‐dipyridylphenyl as a strong σ‐electron donor ligand negatively shifted the oxidation potential of water.