Synthesis, spectra, redox property and catalytic activity of ruthenium(III) Schiff base complexes

Abstract

A series of ruthenium(llI) complexes of the type [RuX₂(EPh₃)₂(L)] (where E= P or As, X= CI or Br; L = bidentate Schiff bases) have been synthesized and characterized on the basis of analytical (elemental analysis, magnetic susceptibility) and spectral methods (FT-IR, UY-vis, EPR). EPR spectra of the powdered samples exhibit three lines with different <i>'g' </i>values indicating a rhombic distortion in these complexes. Cyclic voltammogram of the complexes displays one reversible oxidation (Ru^IV/Ru^III) and two reversible reduction peaks (Ru^III/Ru^II, Ru^II/Ru^I) with <i>∆E</i>_{<span style="mso-bidi-font-style:italic">P</span>}<i> </i>mV suggesting one electron transfer process. These complexes effectively catalyze the oxidation of primary alcohols to their corresponding aldehydes up to 91.5% in the presence of N-methylmorpholine-N-oxide (NMO) as co-oxidant. The formation of high-valent Ruⁿ⁺²=O species as catalytic intermediate is proposed for the catalytic processes.