Fe(III) complexes in cyclohexane oxidation: Comparison of catalytic activities under different energy stimuli

Abstract

In this study, the mononuclear Fe(III) complex [Fe(HL)(NO3)(H2O)2]NO3 (1) derived from Nʹ-acetylpyrazine-2-carbohydrazide (H2L) was synthesized and characterized by several physicochemical methods, e.g., elemental analysis, infrared (IR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single crystal X-ray diffraction analysis. The catalytic performances of 1 and the previously reported complexes [Fe(HL)Cl2] (2) and [Fe(HL)Cl(μ-OMe)]2 (3) towards the peroxidative oxidation of cyclohexane under three different energy stimuli (microwave irradiation, ultrasound, and conventional heating) were compared. 1-3 displayed homogeneous catalytic activity, leading to the formation of cyclohexanol and cyclohexanone as final products, with a high selectivity for the alcohol (up to 95%). Complex 1 exhibited the highest catalytic activity, with a total product yield of 38% (cyclohexanol + cyclohexanone) under optimized microwave-assisted conditions.