In situ-generated mononuclear half-sandwich [(η6‐p‐cymene)RuCl(amide)] complexes as efficient catalysts in the selective oxidation of benzyl alcohol to benzaldehyde

Abstract

The application of in situ-generated mononuclear Ru(II)-organometallic complexes (1–7) i.e., [(η6-p-cymene)RuCl(L)], produced by the interaction of Ru dimer [(p-cymene)RuCl2]2 with some polyfunctional amide ligands(L) as highly efficient catalystsin the oxidation of various benzyl alcohols (B-OLs) by tert-butyl hydroperoxide (TBHP) oxidant to produce selectively the benzaldehydes (B-ALs) in high yields in CH3CN is described. The in situ-generated catalysts were found to be highly active than the [(p-cymene)RuCl2]2 precursor (dimer) in the oxidation of B-OL to B-AL. The influence of various reaction parameters such as type of catalyst, reaction temperature, oxidant and solvent during the B-OL oxidation was systematically monitored to optimize the catalytic conditions. In order to confirm the formation of predicted in situ-generated mononuclear Ru(II) complex catalysts during the oxidation of B-OL, one of the Ru(II) complex (1) was synthesized and characterized by Elemental analysis (EA), Infrared (IR), Proton-NMR and Mass spectral techniques and its mono nuclear structure is proposed. Further, it was observed that the activity of in-situ generated and pre-synthesized Ru(II) catalyst was almost same in the oxidation of B-OL to B-AL.