*Article* **Fe(III) Complexes in Cyclohexane Oxidation: Comparison of Catalytic Activities under Di**ff**erent Energy Stimuli**

### **Tannistha Roy Barman 1, Manas Sutradhar 1,\*, Elisabete C. B. A. Alegria 1,2,\*, Maria de Fátima C. Guedes da Silva 1 and Armando J. L. Pombeiro 1,\***


Received: 25 September 2020; Accepted: 9 October 2020; Published: 13 October 2020

**Abstract:** In this study, the mononuclear Fe(III) complex [Fe(HL)(NO3)(H2O)2]NO3 (**1**) derived from *N*--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.

**Keywords:** Fe(III) complex; *N*,*O* donor; X-ray analysis; alkane oxidation; microwave irradiation
