Mechanistic Study of the Reaction of Ethylene Oxide and CO2 Catalyzed by Salen Complexes

Few chemical processes have proven successful in using CO2 as a feedstock in chemical reactions. While CO2 is abundant and nontoxic, its stability imposes a challenge in finding routes for its effective use. Some transition metal salen complexes can catalyze the coupling reaction of CO2 with epoxides to produce either cyclic carbonates or polycarbonates via two competing reactions. We have used density functional theory calculations to understand how these reactions proceed and to unravel the role of the catalyst on these systems.  We have studied the adsorption of CO2 and ethylene oxide onto Co and Cr salen complexes using the unrestricted OPBE functional along with the effective core potential LANL2DZ for the basis set. Geometrical optimizations were carried out beginning with a variety of different conformations and frequency calculations were used to verify that structures lie in an energy minimum.