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Unprecedented Carbonato Intermediates in Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium(Salen)
José A Castro-Osma1, Michael North2, Willem K Offermans3
1Green Chemistry Centre of Excellence, Department of Chemistry, The University of York, York, YO10 5DD, UK.
Abstract:
The mechanism by which [Al(salen)]2 O complexes catalyse the synthesis of cyclic carbonates from epoxides and carbon dioxide in the absence of a halide cocatalyst has been investigated. Density functional theory (DFT) studies, mass spectrometry and (1) H NMR, (13) C NMR and infrared spectroscopies provide evidence for the formation of an unprecedented carbonato bridged bimetallic aluminium complex which is shown to be a key intermediate for the halide-free synthesis of cyclic carbonates from epoxides and carbon dioxide. Deuterated and enantiomerically-pure epoxides were used to study the reaction pathway. Based on the experimental and theoretical results, a catalytic cycle is proposed.
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