ELECTRON-DISTRIBUTION WITHIN BIS(QUINONE)RUTHENIUM COMPLEXES - STRUCTURAL CHARACTERIZATION ON DELOCALIZED (BIPYRIDINE)BIS(QUINONE)RUTHENIUM AND ON THE LOCALIZED TRANS-BIS(3-CHLOROPYRIDINE)BIS(3,5-DI-TERT-BUTYL-1,2-SEMIQUINONE)RUTHENIUM(III) CATION

Structural information obtained on complexes containing semiquinone and catecholate ligands has provided insights on charge distribution. Ligand CO lengths found for trans-Ru(4-t-Bupy)2(DBQ)2 averaged 1.321(5) Å, midway between values of 1.34 and 1.29 Å expected for localized catecholate and semiquinone ligands. This value may arise from crystallographic disorder of a localized RuIII(SQ)(Cat) species or it may result from charge delocalization over both quinone ligands. Crystallographic characterization of Ru(bpy)(Q)2, where Q is the unsubstituted o-quinone ligand, has shown that the complex molecule crystallizes without imposed symmetry on the molecule, in a crystal structure that places both quinone ligands in different solid-state environments. The four independent CO lengths average 1.321(5) Å, without significant variation, strongly suggesting charge delocalization over both quinone ligands. Characterization on the trans-Ru(3-Clpy)2(DBQ)2+ cation, formed by one-electron oxidation of a neutral species that would be expected to show ligand charge delocalization, has shown ligand CO lengths of 1.293(4) Å, exactly the value expected for semiquinone ligands. Oxidation of the neutral complex appears to occur at a ligand delocalized electronic level to give a ligand localized bis(semiquinone) product, RuIII(SQ)2+. © 1990.