High activity and switchable selectivity in the synthesis of cyclic and polymeric cyclohexene carbonates with iron amino triphenolate catalysts

Abstract

Iron(III) amino triphenolate complexes were studied as catalysts for the reaction of carbon dioxide (CO₂) with cyclohexene oxide, which can lead to the formation of cyclic carbonate and/or polycarbonate products. Both types of compound are relevant, but for their practical application it is crucial to be able to control the selectivity of the reaction. By working under solvent-free, green conditions with CO₂ in the supercritical state and by tailoring the nature and the relative amount of the co-catalyst (Bu₄NX or PPNX, where X is a halide) used in combination with the iron(III) complex, we have been able to enhance the catalytic efficiency and achieve a selective and high-yield synthesis of either the cyclic or the polymeric product. The studied reaction is relevant in the context of green chemistry as it provides an atom-efficient route for the conversion of CO₂, which is an inexpensive, widely available, renewable and non-toxic feedstock, into valuable products.