The importance of the bite angle of metal(III) salen catalysts in the sequestration of CO2 with epoxides in mild conditions

Abstract

Located in the middle of the fever to solve the problem of CO2 emissions in the environment, CO2 sequestration by reaction with epoxides is one of the key tools, as it not only fixes CO2, but also makes it functional by leading to cyclic carbonates. Herein, the results are focused specifically on the formation of cyclic organic carbonates catalyzed by metal-salen complexes, previously achieved with yttrium and scandium, that are compared with those of analogous complexes containing metals from the first transition series, such as cobalt or chromium. Density functional theory (DFT) calculations allow to determine whether this switch of metals will be feasible and provide the basis for instigating future experimental efforts in this regard. The calculations analyzing the structure and electronics of the catalysts allow us to give not only a clear picture of whether these catalysts will be efficient, but also allow us to assess which metal center is the most convenient and/or whether the catalytic reaction will occur under mild conditions. Advanced buried volume calculations with the SambVca packages shed light on the different catalytic pockets of monometallic first row transition metals vs. group III salen complexes. Our predictive catalysis results show that the bite O-M-O angle plays an essential role in the catalysis.