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

Abstract

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 °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 CoCl2.6H2O 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 1H and 13C 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.