Since 1960s, CO2 utilization had led to a great deal of attention which from environmental protection and carbon economy. CO2 utilization with epoxide is one of the efficient ways to produce high value-added material such as polycarbonates (PCs) and cyclic carbonates (CCs). Although lots of complexes have already developed successful catalytic systems to produce polycarbonate (PCs) from the copolymerization of CO2 and epoxide, catalytic system of cyclic carbonate (CCs) is not well developed yet and searching for the efficient catalysts is still remained as an important research area.
A series of new titanium complexes, TiLCl2(THF)(1) and TiL2(2), containing tridentate chiral [ONO] type Schiff-base ligand, L, easily prepared from the condensation reaction of 2,4-pentadione and (1R,2S)-(–)-1-aminoindanol were synthesized and characterized by various analytical methods including X-ray crystallography. Ligand L acted as a dianionic tridentate ligand and, owing a chiral center in the aminoindanol part, imparted chirality to its titanium complexes. The newly synthesized titanium complexes(1, 2) and previously reported analogues Ti complexes(3-5) were used as catalysts in the cycloaddition of CO2 to propylene oxide as the first representatives of titanium complexes with tridentate schiff-base ligand to have been used for this purpose. These complexes provided high selectivity toward cyclic propylene carbonate (>99%) and showed considerable activities with TOF values up to 131 h-1 in comparison with the previously reported catalyst systems.