New dinuclear chromium complexes supported by thioether-triphenolate ligands as active catalysts for the cycloaddition of CO2 to epoxides
Irene Contento, David Hermann Lamparelli, Antonio Buonerba, Alfonso Grassi, Carmine Capacchione
Abstract
A new family of dinuclear chromium complexes bearing thioether-triphenolate ligands has been developed for the cycloaddition of CO2 with epoxides. The catalytic systems resulting from the combination of complexes 1–3 with tetrabutylammonium chloride (TBAC) show high activity and selectivity for the synthesis of cyclic carbonates with a broad range of substrates including terminal and internal epoxides. Notably, in the case of epichlorohydrin, a TOF up to 4650 h-1 (120 °C, 2 MPa) was recorded, showing one of the highest activity for chromium complexes. In the case of internal epoxides, the reaction proceeds with the retention of the substrate configuration highlighting that the mechanism proceeds through two consecutive SN2 reactions.