Cyclic carbonate synthesis from CO2 and epoxides catalyzed by lanthanide derivatives comprising arylhydrazones of β-diketones

Two known lanthanide complexes, [KLa(HL1)2{(CH3)2NCHO}2(H2O)3] (1) and [Sm(H2O)9](E-H2L2)3·2H2O (2), (KH2L1 = potassium 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonate, KH2L2 = potassium (E,Z)-5-chloro-3-(2-(1,3-dioxo-1-phenylbutan-2-ylidene)hydrazinyl)-2-hydroxybenzenesulfonate), have been prepared and tested as catalysts in the cycloaddition of CO2 with epoxides in the presence and absence of co-catalysts (tetrabutylammonium chloride (TBACl), tetrabutylammonium bromide (TBABr) and tetrabutylammonium iodide (TBAI)). Complex 1 was found to be the most efficient catalyst in the presence of TBABr, with conversions up to 97 %, at 40 °C, of the epoxides to the corresponding cyclic carbonates. The catalytic activity of 1 is dependent on the nature of the substrate, ranging from 23 to 97 %.