An efficient iron catalyst for the synthesis of five- and six-membered organic carbonates under mild conditions

An iron(III) amine triphenolate complex, [FeTPhOA]₂, able to efficiently catalyze the cycloaddition of carbon dioxide to a range of terminal epoxides under mild conditions, is described. In addition, it has also been found that the complex is able to catalyze the conversion with more sterically congested oxiranes and oxetanes which are generally considered challenging substrates to activate. Variation of the co-catalyst, required for ring-opening of the substrates, has also been examined. The results show that terminal epoxide substrates are converted more efficiently with an iodide co-catalyst, whereas more bulky oxirane substrates give better product yields in the presence of a bromide co-catalyst. The combined results demonstrate the broad applicability of these iron(III) complexes in this type of carbon dioxide fixation chemistry.