Efficient coupling of CO2 and epoxides with bis(phenoxyiminato) cobalt(III)/Lewis base catalysts

A series of unbridged bis(phenoxyiminato) cobalt(III)complexes were synthesized and studied as catalysts for the coupling of CO2 and epoxide. Dimethylamino pyridine (DMAP) and tetrabutyl ammonium bromide (Bu4NBr), were used as co-catalysts in the reaction. Both Co(III)/DMAP and Co(III)/Bu4NBr systems showed high catalytic activity and selectivity in the coupling of n-hexyl oxide and CO2, resulting in n-hexyl carbonate. Several mono- and di-substituted terminal epoxides were also tested. The reaction mechanism of the Co(III)/DMAP system was investigated in detail using ESI-MS revealing that in addition to the main product, cyclic carbonate, traces of oligomers are formed.

Graphical abstractA series of unbridged bis(phenoxyiminato) cobalt(III)complexes were synthesized and studied as catalysts for the coupling of CO2 and epoxide. Dimethylamino pyridine (DMAP) and tetrabutyl ammonium bromide (Bu4NBr), were used as co-catalysts in the reaction. Both Co(III)/DMAP and Co(III)/Bu4NBr systems showed high catalytic activity and selectivity in the coupling of n-hexyl oxide and CO2, resulting in n-hexyl carbonate. Several mono- and di-substituted terminal epoxides were also tested. The reaction mechanism of the Co(III)/DMAP system was investigated in detail using ESI-MS revealing that in addition to the main product, cyclic carbonate, traces of oligomers are formed.Figure optionsDownload full-size imageDownload as PowerPoint slide