Selective oxidation of sulfide catalysed by Cu complex of a triazamacrocyclic ligand with carbamoyl pendant arms

Copper(II) complex with a new ligand 1,4,7-tris(carbamoylethyl)-1,4,7-triazacyclononane (L) has been synthesized and characterized by elemental analysis, FT-IR, ES-MS, UV–Vis and cyclic voltammetry. Determined by X-ray analysis, the crystal structure shows the metal center is six-coordinated. The compound can catalyze the oxygenation of ethyl phenyl sulfide (EPS) utilizing H2O2 under ambient conditions. EPS was converted to the corresponding sulfoxide and sulfone step by step which was confirmed by 1H NMR spectra. The existence of sulfoxide and sulfone was identified by GC–MS. The gradually disappearance of EPS’s ultraviolet absorption at 290 nm was significantly correlated with the rates of sulfide consumption. The initial reaction rate during the first 3 h is consistent with the first-order law in substrate concentration. The averaged pseudo-first-order rate constant is calculated to be (2.25 ± 0.42) × 10−3 min−1 at 25 °C and (4.44 ± 0.17) × 10−3 min−1 at 30 °C. The oxidation product is almost sulfoxide by choosing the molar concentrations of Cu complex (2% of substrate) and H2O2 (seven times as much as substrate).

Graphical abstractCopper(II) complex with a new ligand 1,4,7-tris(carbamoylethyl)-1,4,7-triazacyclononane (L) crystallizes in the space group P21/c. This six-coordinated complex can catalyze the oxygenation of ethyl phenyl sulfide (EPS) utilizing H2O2 under ambient conditions. Dislike the reaction product (almost sulfone) using Mn–Me3TACN catalyst as once reported, the oxidation product is almost sulfoxide by choosing appropriate concentration of Cu complex and hydroperoxide.Figure optionsDownload full-size imageDownload as PowerPoint slide