A Novel Fe(III) Complex of Bispicen Ligand Covalently Attached to an Fe3O4 Nanomagnet: Catalytic Properties in C-H Oxidation and Benzoxazol Synthesis

Abstract

This study discusses the development of an effective and environmentally friendly C-H oxidation process for the creation of oxygenated compounds in the presence of tert-butyl hydroperoxide by a magnetically recoverable Fe₃O₄@SiO₂-FeL^Bpn nanocomposite. L^Bpn stands for a deprotonated, pyridine-based, four-dentate, bispicen ligand. The synthesised catalyst was characterised by Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), dynamic light scattering (DLS), thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM). Fe₃O₄@SiO₂-FeL^Bpn (40 mg) was introduced as a catalyst in the presence of TBHP (4 eq) for the oxidation of varied C–H bonds to the related carbonyl compounds in high yields. Fe₃O₄@SiO₂-FeL^Bpn (5 mg) was used for the synthesis of benzoxazole derivatives from 1 mmol of every substrate of aldehydes, ammonium acetate, and catechol. By this process, vast amounts of benzoxazoles were satisfyingly obtained in the presence of Fe₃O₄@SiO₂-FeL^Bpn in H₂O under moderated situations, and whole products were gained with excellent results. Fe₃O₄@SiO₂-FeL^Bpn was recovered from the reaction environment through a simple exterior magnet and reused for three times without any remarkable reactivity loss. Moreover, a hot filtration test confirmed the heterogeneous character of the catalyst.