Dioxo-molybdenum(VI) unsymmetrical Schiff base complex supported on CoFe2O4@SiO2 nanoparticles as a new magnetically recoverable nanocatalyst for selective epoxidation of alkenes

In the present work, a dioxo-molybdenum unsymmetrical Schiff base complex, [MoO2(salenac-OH)], in which salenac-OH = [9-(2',4'-dihydroxyphenyl)-5,8-diaza-4-methylnona-2,4,8-trienato](-2), has been prepared and covalently immobilized on the silica-coated CoFe2O4 magnetic nanoparticles (CoFe2O4@SiO2 MNPs) surface as support. Different methods including scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, vibrating sample magnetometry (VSM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), inductively coupled plasma (ICP), thermal gravimetric analysis (TGA), and elemental analysis have been used to characterize the prepared CoFe2O4@SiO2@[MoO2(salenac-OH)] nanocatalyst. The catalytic activity of this novel heterogeneous catalyst has been investigated in the selective epoxidation of alkenes using tert-butyl hydroperoxide (TBHP, 70% aqueous solution) as the oxidizing agent, and the corresponding products were achieved in good to excellent yields in 1,2-dichloroethane at 50 degrees C. Using an external magnet, this magnetic nanocatalyst can be simply separated from the reaction mixture and reused for five cycles without a remarkable decrease in catalytic activity. In addition, no significant changes were found in the recovered catalyst's FT-IR spectrum compared with the fresh one.

Automated summary

In this study, a novel catalyst was prepared by immobilizing a dioxo-molybdenum unsymmetrical Schiff base complex on the silica-coated magnetic nanoparticles. The catalyst showed good catalytic activity and reusability in the selective epoxidation of alkenes.