Closing the loop in the synthesis of heteroscorpionate-based aluminium helicates: catalytic studies for cyclic carbonate synthesis.

Novel polynuclear helical aluminium complexes supported by bulky heteroscorpionate ligands have been developed and characterised. The use of bulkier ligands has allowed the isolation of unprecedented intermediates for the preparation of helical aluminium complexes. The catalytic activity of these aluminium complexes for cyclic carbonates formation has also been investigated under mild reaction conditions. The combination of complex 16 and Bu 4 NBr catalysed the synthesis of a broad range of monosubstituted cyclic carbonates from their corresponding epoxides and CO 2 at 25 °C and one bar of CO 2 pressure. This catalyst system also showed good catalytic activity for the preparation of disubstituted cyclic carbonates from internal epoxides and CO 2 .