Mono/multinuclear cobaloxime and organocobaloxime-catalyzed conversion of CO2 and epoxides to cyclic organic carbonates: Synthesis and characterization

The synthesis and characterization of the mono- and multinuclear cobaloxime and organocobaloxime complexes bearing bidentate dimethyl glyoxime ligands are presented. All mono- and multinuclear cobaloxime and organocobaloxime complexes are used as catalysts for the cycloaddition of CO2 to various epoxides, especially epichlorohydrin, in the presence of 4-dimethylamino pyridine (DMAP) as a cocatalyst. In the catalytic applications, DMAP was a more active base with higher yield compared to other Lewis bases. Complexes (I) and (3), which have two dimethyl glyoxime per cobalt center (mononuclear complexes), are better catalytic systems than the corresponding multinuclear cobaloxime and organocobaloxime complexes (2-5) and (7-10) with two dimethyl glyoxime per cobalt center and one linked ligands per copper center. In addition, the organocobaloxime complex (6) showed the highest activity for the cycloaddition of CO2 with epichlorohydrin in the presence of 4-dimethylamino pyridine (DMAP) as cocatalyst. The used as catalysts mono- and multinuclear cobaloxime and organocobaloxime complexes were characterized by H-1 and C-13 NMR spectra, FT-IR spectra, UV-vis spectra, LC-MS spectra, molar conductivity measurements, melting point measurements and magnetic susceptibility measurements. (C) 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.