ELECTROCATALYTIC OXIDATION BY BINUCLEAR RUTHENIUM COMPLEXES INCORPORATING THE ANIONIC TRIPOD LIGAND [(ETA(5)-C5H5)CO((CH3O)2P=O)3]-

The two-phase reaction of NaL(OMe) (L(OMe-) = [(eta5-C5Hs)Co{P(O)(OCH3)2}3]-) in 1% H2SO4 with RuO4 in CCl4 affords the edge-sharing octahedral dimer [(L(OMe))(HO)Ru(IV)(mu-0)2Ru(IV)(OH)(L(OMe))] which is diprotonated by aqueous CF3SO3H to the corresponding salt [(L(OMe))(H2O)Ru(IV)(mu-0)2RU(IV)(OH2)(L(OMe))] [CF3SO3]2. This dimer salt is oxidized by C6H510 in CH3CN to [(L(OMe)(O)Ru(V)(mu-0)2Ru(V)(O)(L(OMe))] and reduced by alcohols, aldehydes, or triphenylphosphine in CH3CN to [(L(OMe))(CH3CN)Ru(III)(mu-OH)2Ru(III)(NCCH3)(L)OMe))][CF3SO3]2. In buffered aqueous solution, the diprotonated Ru(IV)-Ru(IV) dimer reacts with formaldehyde to afford a triply bridged dimer, [(L)OMe))Ru(III))(mu-OH)2(mu-HCOO)Ru(III)(L(OMe))][CF3SO3]. The latter reaction appears to be autocatalytic via an inner-sphere mechanism. Thc Ru(III)-Ru(III) formate adduct is oxidized by AgCF3SO3 to the Ru(IV)-Ru(IV) analog [(L(OMe))Ru(IV)(mu-0)2(mu-HCOO)Ru(IV)(L(OMe))] [CF3SO3], which slowly reacts with aqueous formaldehyde to regenerate the Ru(III)-Ru(III) adduct and free formate. The dimeric system in aqueous solution functions as an electrocatalyst for the oxidation of formaldehyde at low anodic potentials (near 0.0 V versus SCE at pH 8.5). Both Ru(III)-Ru(III) dimers have been characterized by X-ray crystallography. Crystal data: [(L(OMe))(CH3CN)Ru(III)(mu-OH)2-Ru(III)(NCCH3)(L(OMe))][CF3SO3]2, RU2Co2C28H54O26N2P6S2F6, triclinic, P1BAR, with a = 8.626(3) angstrom, b = 12.275(2) angstrom, c = 13.457(3) angstrom, alpha = 71.32(2)-degrees, beta = 85.35(2)-degrees, gamma = 80.01(3)-degrees, V = 1328.9(6) angstrom3, Z = 2, R(F(o)) = 0.040; [(L(OMe))Ru(III)(mu-OH)2(mu-HCOO)Ru(III)(L(OMe))][CF3SO3].2H20, RU2Co2C24H53027P6SF3, monoclinic, P2(1)/n, with a = 14.356(2) angstrom, b = 23.839(6) angstrom, c = 15.284(3) angstrom, beta = 11 5.44(l)-degrees, V = 4723.5(18) angstrom3, Z = 4, R(F(o)) = 0.033.