SYNTHESIS, CRYSTAL-STRUCTURE AND REDOX PROPERTIES OF MU-OXO-BIS(MU-ACETATO)DIRUTHENIUM(III) COMPLEXES HAVING 2,2'-BIPYRIDINE AND IMIDAZOLE BASES AS TERMINAL LIGANDS

Three diruthenium(III) complexes, [{Ru(bipy)L}(2)(mu-O)(mu-O(2)CMe)(2) ][ClO4](2), have been prepared and characterized (L = imidazole, 1- or 4-methylimidazole; bipy = 2,2'-bipyridine). The crystal structure of the 1-methylimidazole complex [Ru2O(O(2)CMe)(2)(bipy)(2)(1-mim)(2)][Cl O4](2) . H2O . MeOH has been determined. The complex has a Ru-2(mu-O)( mu-O(2)CMe)(2)(2+) core with terminal unidentate 1-mim and bidentate c helating bipy ligands. The imidazole is trans to the oxide ligand. The Ru ... Ru distance and Ru-O-Ru angle are 3.285(2) Angstrom and 121.5( 3)degrees. The H-1 NMR spectra of the complexes are consistent with th is crystal structure. The complexes show an intense charge-transfer ba nd near 600 nm. They are redox active and display reversible one-elect ron oxidation and reduction processes. On addition of weak proton-dono r imidazole bases the complexes undergo a one-step two-electron reduct ion process (RuRuIII)-Ru-III-(RuRuII)-Ru-II along with the (RuRuIII)-R u-III-(RuRuIV)-Ru-III oxidation couple.