Synthesis, spectroscopic characterization, redox properties and catalytic activity of some ruthenium(II) complexes containing aromatic aldehyde and triphenylphosphine or triphenylarsine

A series of new mixed ligand penta-coordinated square pyramidal ruthenium(II) complexes containing benzaldehyde or its substituents and triphenylphosphine or triphenylarsine have been synthesized and characterized. In the electronic spectra, three well-defined peaks in the visible region were observed and assigned to d-d transitions in D-4h and low spin axially distortion from O-h symmetry. The spectrochemical parameters of the complexes were calculated and placed the ligands in the middle of the spectrochemical series. The redox properties and stability of the complexes toward oxidation were related to the electron-withdrawing or releasing ability of the substituent in the phenyl ring of the benzaldehyde. The electron-withdrawing substituents stabilized Ru2+ complexes, while electron-donating groups favored oxidation to Ru3+. The mechanism and kinetics of the catalytic oxidation of benzyl alcohol by the complex [RuCl2(Pph(3))(C6H5CHO)(2)] in the presence of N-methylmorpholine-N-oxide have also been studied. (C) 2003 Elsevier B.V. All rights reserved.