Inter- and intramolecular phosphonium salt cocatalysis in cyclic carbonate synthesis catalysed by a bimetallic aluminium(salen) complex

Quaternary phosphonium salts can be used as cocatalysts for the conversion of epoxides and carbon dioxide into cyclic carbonates catalysed by bimetallic aluminium(salen) complexes at ambient temperature and one atmosphere pressure. The phosphonium groups could also be attached onto the salen ligands of the bimetallic aluminium(salen) complex to form one-component catalysts, and in this case the catalytic activity was heavily influenced by the solubility of the catalyst in the epoxide substrate. The results are consistent with a previously proposed catalytic cycle for cyclic carbonate synthesis catalysed by bimetallic aluminium(salen) complexes.