Alkylaminophosphazenes as Efficient and Tuneable Phase‐Transfer Agents for Polyoxometalate‐Catalysed Biphasic Oxidation with Hydrogen Peroxide

Abstract

Abstract Alkylaminophosphazenes (RPN) are efficient and tuneable phase‐transfer agents for environmentally benign biphasic oxidation with hydrogen peroxide catalysed by polyoxometalates (POMs). Substituent groups on the phosphazene ring can be varied to modify the phase‐transfer efficiency of RPN for use in water–organic two‐phase systems. Active phosphazene–polyoxometalate aggregates that self‐assemble in situ from RPN and Keggin POMs, such as PMo 12 O 40 3− and PW 12 O 40 3− , were found to be efficient and recyclable catalysts for the oxidation of benzothiophenes and the epoxidation of alkenes with hydrogen peroxide. Lipophilic phosphazene cations present in these aggregates render the POM soluble in organic media. Catalyst activity in the biphasic oxidation with H 2 O 2 varies with the RPN substituent alkylamino groups with respect to the solvent system used. The activity decreases in the series of POMs: PMo 12 O 40 3− >PW 12 O 40 3− ≫SiW 12 O 40 4− irrespective of the solvent system used.