Synthesis and characterization of molybdenum complexes with bidentate Schiff base ligands within nanoreactors of MCM-41 as epoxidation catalysts

The mesoporous molecular sieve MCM-41 was covalently grafted with 3-aminopropyl trimethoxysilane to give aminopropyl modified MCM-41 (AmpMCM-41). Reaction of this material with furfural, pyrrolcarbaldehyde, 2-acetylpyrrol, 2-aminoacetophenone, salicylaldehyde and acetylacetone afforded the corresponding supported Schiff base ligands. Subsequent reaction with bis(acetylacetonato)dioxomolybdenum(VI) leads to various molybdenum complexes supported on MCM-41 through propyl chain spacer. Characterization of these materials was carried out with FT-IR, atomic absorption spectroscopy, powder X-ray diffraction (XRD) and BET nitrogen adsorption–desorption methods. The XRD and BET analyses revealed that textural properties of support were preserved during the grafting experiments. The resultant materials successfully catalyzed the epoxidation of cyclooctene, cyclohexene, 1-hexene and 1-octene with tert-butyl hydroperoxide (TBHP) to the corresponding epoxides with 98–100% selectivities.

Graphical abstractIncorporation of bidentate Schiff base ligands via reaction of aminopropyl modified MCM-41 with different aldehydes and ketones and subsequent treatment with MoO2(acac)2 affords anew class of heterogeneous molybdenum catalysts for epoxidation of olefins with high activity and selectivity. Figure optionsDownload full-size imageDownload as PowerPoint slide