SYNTHESIS, CHARACTERIZATION, AND EPR STUDIES OF STABLE RUTHENIUM(III) SCHIFF-BASE CHLORO AND CARBONYL-COMPLEXES

Stable ruthenium(III) carbonyl chelates of Schiff bases with axial ligands chloro, imidazole, and 2-methylimidazole are synthesized by interacting the methanolic solutions of their correspondng Ru(III) chloro complexes with carbon monoxide. The Schiff bases used are bis(salicylaldehyde) ethylenediimine (salen), bis(salicylaldehyde) o-phenylenediimine (saloph), bis(salicylaldehyde) diethylenetriimine (saldien), bis(picolinaldehyde) ethylenediimine (picen), bis(picolinaldehyde) o-phenylenediimine (picoph), and bis(picolinaldehyde) diethylenetriimine (picdien). These complexes are characterized by elemental analysis and IR, UV-visible, differential-pulse polarography, conductivity, magnetic susceptibility, and EPR techniques. The oxidation state of the metal ion in these complexes is confirmed to be +3 by electrochemical, magnetic susceptibility, and EPR measurements. The complexes belong to a low-spin Ru(III) 4d5 configuration. EPR studies indicate that the unpaired electron in the carbonyl complexes occupies the dxy orbital. The distortion from the octahedral symmetry and delocalization parameters vary with the axial ligands, as well as with temperature. MO coefficients of T2 orbitals in these complexes were estimated. A comparison of EPR results on chloro and carbonyl complexes is made. In the case of salen and saloph complexes, replacement of the axial ligand Cl− by CO changes the energy level ordering. Differential-pulse polarographic study of the carbonyls reveals that the redox potential of Ru(III)/Ru(II) couple becomes more negative with increasing basicity of the axial ligand. © 1990, American Chemical Society. All rights reserved.