• Oxido ligands;
  • Mixed-valent compounds;
  • Redox chemistry;
  • Ruthenium;
  • Tridentate ligands


Trihalogenoruthenium(III) complexes bearing an ethylbis(2-pyridylmethyl)amine (ebpma) ligand, fac-[RuIIIX3(ebpma)] (X = Cl, Br), were reduced by zinc in acetone that contained halogeno acid to afford a reddish-orange solution. Two kinds of dinuclear complexes were synthesized from the solution. After removing the remaining zinc and adding counterions such as PF6 and BF4 with water, the solution was allowed to stand under air until the color of the solution changed. New oxido-bridged dinuclear complexes of mixed-valence RuIII–RuIV [{RuIII,IVX2(ebpma)}2(μ-O)]Y (X = Cl, Y = PF6, [1]PF6; Y = BF4, [1]BF4; X = Br, Y = PF6, [2]PF6; Y = BF4, [2]BF4), which showed a similar framework to the reported water oxidation catalysts, were obtained as deep-colored solids. In the reaction without addition of extra water, a different mixed-valence dinuclear complex of RuII–RuIII [{RuII,III(ebpma)}2(μ-Cl)3]2+, for which the metal centers were triply bridged by three chlorides, was formed. The synthetic procedures are useful for the development of multinuclear frameworks that function as molecular catalysts for redox reactions such as water oxidation.