ISOMERIC RUTHENIUM(III) COMPLEXES OF N-PHENYL-2-PYRIDINE CARBOXALDIMINE - SYNTHESIS, CHARACTERIZATION AND ELECTRON-TRANSFER PROPERTIES

Three geometric isomers of [RuCl(2)L(2)](ClO4) (L = N-phenyl-2-pyridin e carboxaldimine) have been isolated by stereoretentive oxidation of t he corresponding isomeric ruthenium(II) complexes using Cl-2(g) as an oxidant, followed by the addition of aqueous sodium perchlorate. These complexes are paramagnetic (low-spin d(5), S = 1/2) and display rhomb ic EPR spectra at 77 K. The electronic transition energies have been c omputed, using the observed g values, which agree well with the experi mentally observed transitions in the IR region of the optical spectra. In addition to the ligand held transitions, all the complexes also sh ow multiple charge-transfer transitions in the visible region. Each of the complexes display a reversible reductive response due to an Ru-II I/Ru-II couple in the range 0.3-0.5 V versus SCE at a platinum electro de. Chemical reductions of these trivalent complexes by hydrazine reve rt almost quantitatively to the parent bivalent ruthenium complexes. I n acetonitrile, RuCl(2)L(2)(+) complexes act as mild oxidants.