Silica-bound imidazole as a heterogeneous axial ligand for Mn(salophen)Cl: Efficient, recoverable and recyclable catalyst for epoxidation of alkenes and hydroxylation of alkanes with sodium periodate

Choloropropylated silica-gel reacts with imidazole to give imidazole modified silica, which can bound to manganese(III) salophen complex via ligand-to-metal coordination bond. Silica-bound imidazole (SiIm), is not only a heterogeneous axial base but also is a support for immobilization of Mn(III) salophen. The catalyst, Mn(salophen)Cl-SiIm, has been characterized by FT-IR, UV–vis spectroscopic techniques, SEM, thermal and elemental analysis. Mn(salophen)Cl-SiIm catalyze alkene epoxidation with sodium periodate as oxidant at room temperature. The effect of reaction parameters such as solvent and oxidant in the epoxidation of cis-cyclooctene were investigated. This catalytic system shows a good activity in the epoxidation of linear alkenes, which is higher than the homogeneous analogs, Mn(salophen). Alkylaromatics and cycloalkanes were oxidized efficiently to their corresponding alcohols and ketones in the presence of this catalyst. The obtained results showed that this catalyst is a robust and stable heterogeneous catalyst and can be recovered quantitatively by simple filtration and reused without loss of its acivity.

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