Synthesis, characterization, and detailed electrochemistry of binuclear ruthenium(III) complexes bridged by bisacetylacetonate.: Crystal and molecular structures of [{Ru(acac)2}2(tae)] (acac=2,4-pentanedionate ion, tae=1,1,2,2-tetraacetylethanate dianion)

Binuclear beta-diketonatoruthenium(III) complexes [{Ru(acac)(2)}(2)(tae)], [{Ru(phpa)(2)}(2)(tae)], and [(acac)(2)Ru(tae)Ru(phpa)(2)] and binuclear and mononuclear bipyridine complexes [{Ru(bpy)(2)}(2)(tae)](PF6)(2) and [Ru(bpy)(2)(Htae)]PF6 (acac = 2,4-pentanedionate ion, phpa = 2,2,6,6-tetramethyl-3,5-heptanedionate ion, tae = 1,1,2,2-tetraacetylethanate dianion, and bpy = 2,2'-bipyridine) were synthesized. The new complexes have been characterized by H-1 NMR, MS, and electronic spectral data. Crystal and molecular structures of [{Ru(acac)(2)}(2)(tae)] have been solved by single-crystal X-ray diffraction studies. Crystal data for the meso isomer of [{Ru(acac)(2)}(2)(tae)] have been confirmed by the dihedral angle result that two acetylacetone units of the bridging tae ligand are almost perpendicular to one another. A detailed investigation on the electrochemistry of the binuclear complexes has been carried out. The electrochemical behavior details of the binuclear complexes have been compared with those of the mononuclear complexes obtained from the half-structures of the corresponding binuclear complexes. Studies on the effects of solvents on the mixed-valence states of Ru-II-Ru-III and Ru-III-Ru-IV complexes have been carried out by various voltammetric and electrospectroscopic techniques. A correlation between the comproportionation constant (K-c) and the donor number of the solvent has been obtained. The K-c values for the binuclear complexes have been found to be low because of the fact that two acetylacetone units of the bridging tae ligand are not in the same plane, as revealed by the crystal structure of [{Ru(acaC)(2)}(2)(tae)].