Unprecedented Carbonato Intermediates in Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium(Salen) Complexes

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.