OXO-CENTERED MIXED-LIGAND TRIRUTHENIUM COMPLEXES HAVING REDOX-ACTIVE N-METHYL-4,4'-BIPYRIDINIUM IONS (MBPY(- REVERSIBLE MULTISTEP ELECTROCHEMICAL PROPERTIES OF I2RUII(MU(3)-O)(MU-CH3CO2)(6)(MBPY(+))(2)(CO)](2+) AND [RUIII3(MU(3)-O)(MU-CH3CO2)(6)(MBPY(+))(2)(L)](3+) (L=H2O AND N-HETEROCYCLIC LIGANDS)()) )

A new series of oxo-centered acetate-bridged triruthenium comlexes hav ing two redox-active N-methyl-4,4'-bipyridinium ions (mbpy(+)) have be en prepared, and their reversible multistep and multielectron electroc hemical properties are reported: -Ru-III(mu(3)-O)mu-CH3CO2)(6)(mbpy(+) )(2)(CO)](2+) and [Ru-3(III)(mu(3)-O)mu-CH3CO2)(6)(mbpy(+))(2)- (L)](3 +) (L = H2O, pyrazine (pz), pyridine (py), imidazole (Him), and 4-(dim ethylamino)pyridine (dmap)). Among these series, the CO complex, II(mu (3)-O)mu-CH3CO2)(6)(mbpy(+))(2)(CO)](ClO4)(2) . 2DMF (1b . 2DMF) was s tructurally characterized by X-ray crystallography. 1b . 2DMF crystall izes in the monoclinic space group P2(1)/m (No. 11) with a = 8.740(6) Angstrom, b = 32.269(6) Angstrom, c = 10.276(4) Angstrom, beta = 103.3 7(5)degrees, V = 2820(2) Angstrom(3), Z = 2, d(calcd) = 1.636 g cm(-3) , and R = 0.071 (R(w) = 0.074) for 5277 independent reflections (\F-o\ > 3 sigma(\F-o\). The (CO)- Ru ... Ru distance (3.410(2) Angstrom) is appreciably longer than the other Ru ... Ru distance (3.276(2) Angstr om), indicating that the trinuclear core is in the valence-trapped (Ru 2RuII)-Ru-III(CO) oxidation state. The cyclic voltammogram of II(mu(3) -O)(mu-CH3CO2)(6)(mbpy(+))(2)(CO)](PF6)(2) (1a) shows a total of seven reversible one-electron redox steps at E(1/2) = +0.90, +0.26, -1.07, -1.17, -1.56, -1.97, and -2.32 V and one irreversible step at E(pc) = -2.99 V vs Fc/Fc(+) in a 0.1 M [(n-C4H9)(4)N]PF6-CH3CN solution (M = m ol dm(-3)). All of the waves are clearly assignable to the trirutheniu m ''Ru-3(mu(3)-O)'' core-based or mbpy(+) ligand-based processes. The splitting of each ligand-based redox processes (mbpy(+)/mbpy(.) and mb py(.)/mbpy(-)) into two one-electron steps indicates that electronic i nteractions between two terminal ligands occur through the trirutheniu m cluster core. Other mixed-ligand Ru-3(III) analogs also show multist ep redox behavior involving a total of eight or nine electrons. While the extent of interactions between ligands is much smaller than that f ound in the CO complex, it is systematically changed by the nature of L; with more basic L, interactions between two mbpy(+) ligands become larger.