New magnetic supported hydrazone Schiff base dioxomolybdenum (VI) complex: An efficient nanocatalyst for epoxidation of cyclooctene and norbornene

Abstract

A new dioxomolybdenum (VI) complex with tridentate hydrazone Schiff base ligand (H 2 L) derived from 2‐hydroxy‐5‐nitrobenzaldehyde and benzhydrazide was synthesized and designated as [MoO 2 L (DMF)]·2H 2 O. The Fe 3 O 4 @SiO 2 ‐CPS‐L‐MoO 2 (EtOH) nanocatalyst was successfully prepared by grafting H 2 L ligand on modified Fe 3 O 4 nanoparticles followed by reacting with MoO 2 (acac) 2 . The complex and nanocatalyst were characterized by various techniques such as elemental analysis, mass, FT‐IR, UV–Vis, 1 H NMR, 13 C{ 1 H}‐NMR, TGA, XRD, XPS, TEM, SEM and VSM. The catalytic activity of [MoO 2 L (DMF)]2H 2 O and Fe 3 O 4 @SiO 2 ‐CPS‐L‐MoO 2 (EtOH) were evaluated for the oxidation of various alkenes (cyclooctene, norbornene, cyclohexene, styrene and α‐methyl styrene) in the presence of tert ‐butylhydroperoxide as oxidant. The results revealed that the catalysts were especially efficient for oxidation of cyclooctene and norbornene with 100% selectivity towards corresponding epoxide product. Fe 3 O 4 @SiO 2 ‐CPS‐L‐MoO 2 (EtOH) showed higher catalytic activity, shorter reaction time and higher turnover number (TON) compared with homogeneous complex [MoO 2 L (DMF)]·2H 2 O. Moreover, simple magnetic recovery from the reaction mixture and reuse for several times with no significant loss in activity were other advantages of the nanocatalyst.