Highly active and selective Zn(II)-NN′O Schiff base catalysts for the cycloaddition of CO2 to epoxides

Abstract Mononuclear Zn(II) complexes with tridentate NN′O-donor base Schiff ligand N -(2-pyridyl)methyl-2-hydroxy-3,5-di- tert -butylbenzaldimine ( 1H ) combined with a co-catalyst are active for the cycloaddition of CO 2 and epoxides. They provide cyclic carbonates selectively even with the more hindered substrates such as cyclohexene oxide and methyl epoxyoleate. The best conditions were achieved running the reaction in expanded neat substrate in CO 2 as reaction media. The activity obtained for the cycloaddition of CO 2 to styrene oxide reached an initial TOF of 3733 h −1 . The solid state structures of [Zn( 1 ) 2 ] and [Zn( 1 )(OAc) 2 ] n were determined by X-ray diffraction methods. Relative stability of the species in solution was analysed by DFT calculations.