Sonochemical syntheses of nano-sized dioxomolybdenum complexes: An efficient, selective and reusable heterogeneous nanocatalyst for oxidation of alkenes

•Dioxomolybdenum nanoparticles have been prepared under ultrasonic irradiation.•The prepared nanocatalysts catalyzed the oxidation of olefins with TBHP.•Heterogeneous and reusable nanocatalysts are utilized.

Two Schiff base ligands derived from 2-hydroxy-4-methoxyacetophenone and 2,2′-dimethylpropylenediamine (H2L1) or 1,2-cyclohexanediamine (H2L2) have been synthesized and characterized by physico-chemical and spectroscopic methods. Then dioxomolybdenum complexes have been prepared by reaction of Schiff base ligands and MoO2(acac)2 under ultrasonic irradiation to give nanoparticles of MoL1 and MoL2. FT-IR, UV–vis, 1H NMR and 13C NMR spectroscopy, elemental analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were used to characterize and investigate the nanocatalysts. A practical catalytic method for efficient and highly selective oxidation of wide range of olefins with anhydrous tert-butyl hydroperoxide over the prepared molybdenum nanocatalysts was investigated. Under mild reaction conditions, oxidation of cyclooctene led to the formation of corresponding epoxide with a yield of more than 90%. The catalysts were reused five consecutive times without detectable catalyst leaching or significant loss of activity.

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