Selective Sulfide Oxidation with Hydrogen Peroxide Catalyzed by a Silica‐Supported Polypyridyl‐Iron Complex

Inspired by biomimetic models of non-heme iron oxygenase, an iron(II)-complex ligated by a polypyridyl ligand (TPAN) has been covalently anchored onto silica beads to exploit its oxidation capabilities towards sulfide oxidation in the presence of hydrogen peroxide as an oxidant. The prepared catalyst [Fe-TPAN@SiO2] was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The silica-supported catalyst, measuring under 300 nm in size as observed via transmission electron microscopy (TEM), showed outstanding selectivity in the mono-oxygenation of sulfides, yielding the corresponding sulfoxides with high efficiency. The immobilized catalyst showed far better conversion as compared to the analogous homogeneous complex. The catalyst could be isolated and reused up to six cycles without losing the activity-selectivity profiles. A simultaneous involvement of an iron-oxygen intermediate and a Fenton-type process is proposed, with the former presumed to be the dominant oxidation pathway.