Ketone synthesized cobaloxime/organocobaloxime catalysts for cyclic carbonate synthesis from CO2 and epoxides: Characterization and electrochemistry

Herein we report the synthesis and characterization of a new series of synthesized mono-and trinuclear cobaloxime/organocobaloximes from ketone that act as catalysts for cyclic carbonate synthesis from CO2 and epoxides under appropriate conditions (2 h, 100 degrees C and 1.6 MPa pressure). These reactions were carried out with and without co-catalyst, namely, 4-dimethylaminopyridine (DMAP), pyridine (py), triethyl amine (NEt3) or triphenyl phosphine (PPh3). In the catalytic experiments, the 4-dimethylaminopyridine (DMAP) was used as co-catalyst, since the DMAP was a more active base with higher yield compared to other Lewis bases. In addition, various factors influencing the cycloaddition reaction, such as co-catalyst, temperature, CO2 pressure and reaction time, were investigated. A dioxime ligand (LH2) (1) was obtained in two steps from 4-methylpropiophenone as ketone. Reaction of CoCl2.6H(2)O with the dioxime ligand (LH2) (1) and 4-tertbutyl pyridine afforded six-coordinate mononuclear cobaloxime or organocobaloxime (2-3) complexes. The mononuclear cobaloxime or organocobaloxime (2-3) complexes were used as precursors for building trinuclear cobaloximes or organocobaloxime (4-11) complexes. All compounds were fully characterized by H-1 and C-13 NMR spectra, FT-IR spectra, UV-Vis spectra, molar conductivity measurements, melting point measurements, magnetic susceptibility measurements, and LC-MS spectroscopic studies as well as by cyclic voltammetry. (C) 2014 Elsevier B. V. All rights reserved.