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. (C) 2009 Elsevier B.V. All rights reserved.