Highly Active Chromium Complexes Supported by Constrained Schiff-Base Ligands for Cycloaddition of Carbon Dioxide to
Jiraya Kiriratnikom1, Nattiya Laiwattanapaisarn1, Kunnigar Vongnam1
1Department of Materials Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Wang Chan, Rayong 21210, Thailand.
Abstract:
Novel constrained Schiff-base ligands (inden) were developed based on the well-known salen ligands. Chromium complexes supported by the constrained inden ligands were successfully synthesized and used as catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO2). The catalyst having tert-butyl (Bu) groups as substituents in combination with tetrabutylammonium bromide (TBAB) as a cocatalyst exhibited very high catalytic activity with a turnover frequency of up to 14800 h-1 for the conversion of CO2 and propylene oxide into propylene carbonate exclusively at 100 °C and 300 psi of CO2 under solvent-free conditions. The catalyst was found to be highly active for various epoxide substrates to produce terminal cyclic carbonates in 100% selectivity.
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