PREPARATION, STRUCTURE, AND PROPERTIES OF THE BIS(MU-ACETATO)(MU-OXO)RUTHENIUM(III) DIMERS [RU2(MU-CH3COO)2(MU-O)(PY)6]2+ AND [RU2(MU-CH3COO)2(MU-O)(BPY)2(PY)2]2+

Two ruthenium(III) dimers with a core structure similar to the methemerythrin active center have been prepared: [Ru2(mu-CH3COO)2(mu-O)(py)6]2+ (1) and [Ru2(mu-CH3COO)2(mu-O)(bpy)2(py)2]2+ (2) (py = pyridine, bpy = 2,2'-bipyridine). [Ru2(CH3COO)2(O)(py)6](PF6)2 crystallizes in the monoclinic space group C2/c with a = 42.229 (6) angstrom, b = 10.726 (1) angstrom, c = 20.470 (3) angstrom, beta = 112.45 (1)-degrees, V = 8568 (2) angstrom 3, and Z = 8. The Ru-Ru distance is 3.251 (2) angstrom, and the direct metal-metal bond is absent. H-1 NMR spectra of 1 in organic solvents are consistent with the solid-state structure. Those of 2 indicate that chelating bpy occupies the positions trans to the two acetate bridges. The complexes exhibit strong visible absorption bands at 581 nm (epsilon = 10 000 M-1 cm-1) and 599 nm (epsilon = 19 200) in CH3CN for 1 and 2, respectively. Cyclic voltammograms of both complexes in CH3CN show one reversible oxidation process and one irreversible reduction process in the range from -1 to +1 V vs Ag/AgClO4. The substitution reaction of py-d5 for the coordinated py in 1 shows that the position trans to the oxide bridge is at least 10 times more labile than the cis positions. The first-order rate constants in the presence of excess py-d5 (0.125 mol dm-3) are 2.2 x 10(-4) and 5.5 x 10(-5) s-1 for 1 and 2, respectively, at 50-degrees-C in CD3CN.