**1. Introduction**

The functionalization of alkanes should provide convenient methods for building a range of valuable organic products [1–9]. However, due to their inertness, such processes are difficult and, e.g., the catalytic oxidation of alkanes remains one of the most challenging fields of chemistry.

The selective oxidation of cyclohexane to cyclohexanol and cyclohexanone has a significant relevance in terms of industrial and economical viewpoints, because these products are used as precursors of adipic acid which, among other applications, is used in the manufacturing of Nylon-6,6 [1–14]. In industry, that reaction is currently performed using a cobalt(II) naphthenate catalyst [15] at 160 ◦C and 15 bar with very low yields (4%), in order to achieve a good selectivity (80%) [1,2,9,14,15]. The search for more efficient catalytic systems through the development of novel metal-based catalysts and single-pot methodologies for the mild oxidation of alkanes is thus a challenging task [1–3,7,16–23], involving new catalysts with cheap and abundant metals, namely copper [24–27] and iron [28–33]. Microwave irradiation has also been shown to assist with the reaction in various cases [28–33].

In continuation of our work on the catalytic oxidation of alkanes and related species with metal-hydrazone catalysts [24–27,34–44], herein, we report the synthesis and characterization of the new mononuclear Fe(III) complex [Fe(HL)(NO3)(H2O)2]NO3 (**1**) obtained from *N*--acetylpyrazine-2-carbohydrazide (H2L), and a comparison of its catalytic activity with those of the related compounds [Fe(HL)Cl2] (**2**) and [Fe(HL)Cl(μ-OMe)]2 (**3**) [45]. The catalytic activity of these complexes in the oxidation of cyclohexane was evaluated by conventional heating and under microwave (MW) or ultrasound (US) irradiations. MW and US irradiations were applied to activate the proposed catalytic system, eventually enhancing the yield, selectivity, and/or rate in comparison with conventional heating [46,47], but their application in alkane functionalization is still rather underexplored [48–50].
