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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