Metal complexes bearing ONO ligands as highly active catalysts in carbon dioxide and epoxide coupling reactions

摘要

The use of carbon dioxide as feedstock in copolymerization reaction with epoxides has been ideally proposed as an alternative route to produce chemicals without the use of phosgene. One of the most appealing strategies is to use metal complexes as catalysts to form cyclic organic carbonates. These organic compounds are very interesting in industry due to their enormous scope of applications. In this paper, the use of catalytic systems based on sustainable, non-toxic and cheap metal complexes (Mn, Fe, Co) containing Schiff-base tridentate ONO ligands in the synthesis of propylene carbonate (PC) from carbon dioxide and propylene oxide (PO), are discussed. All complexes were tested successfully, affording cyclic carbonate in high productivities (3800 mol PC/mol cat) using a co-catalyst. Synthetized iron and manganese complexes have shown significantly higher activities compared with the activity showed by the new cobalt complexes. The catalytic conditions using the manganese (II) complex 2 were optimized and a TOF of 1600 h-1 was reached.