The First Bis(μ-acetato)(μ-oxido)diruthenium(III) Complexes Containing Sulfur Donor Ligands

Novel diruthenium(III) complexes of general formula [Ru-2(III)(mu-O)(mu-CH3CO2)(2)(bpy)(2)L-2](PF6)(2) (L: tetrahydrothiophene, (3); 4,5-dihydro-3(2H)-thiophenone, (4); thiazole, (5); 4-methylthiazole, (6); bpy: 2,2'-bipyridine), which contain sulfur or nitrogen donor ligands at the trans-to-oxido sites, have been synthesized. The Ru-S bond distance in 4 is determined by X-ray crystallography to be 2.447 angstrom, and the Ru-N(trans-to-oxido) length in 5 (2.157 A) is similar to that of the complex having pyridine as the L ligand, 1. The spectroscopic properties and redox behavior of the complexes bearing sulfur donor ligands have been investigated and compared with those containing nitrogen donor ligands. The potentials of the redox couples of Ru-2(II,III)/Ru-2(III,III) and Ru-2(III,III)/Ru-2(III,IV) for 3 and 4 shift to positive regions compared with those of complexes with nitrogen donor ligands, 1, 5 and 6. The density functional theory (DFT) calculations reveal that the contribution of the trans ligand to the visible absorption is larger in 3 and 4 than in 1, 2 (L: CH3CN), 5 and 6.