Catalytic behaviour of a novel Fe(iii) Schiff base complex in the mild oxidation of cyclohexane

Abstract

The complex [Fe^III(HL)Cl₂(DMF)]Cl·DMF (1) was synthesized by reaction of Fe(III) chloride with a dimethylformamide solution of the Schiff base aminoalcohol HL (2-[(E)-{[2-(piperazin-1-yl)ethyl]imino}methyl]phenol) and characterized by single crystal X-ray diffraction analysis, thermogravimetry and spectroscopic methods. The catalytic investigations disclosed a marked activity of 1 towards oxidation of cyclohexane with hydrogen peroxide, under mild conditions, with yields based on cyclohexane up to 37% and TONs (turnover numbers) up to ca. 900. Kinetic experiments and selectivity parameters led to the conclusion that hydroxyl radicals are active (attacking C–H bonds) species in the studied catalytic reaction. Kinetic and UV/Vis spectrometry data revealed a complex nature of the processes occurring in the catalytic system, including the transformation of 1 into catalytically active species.