Quantum mechanical study of the reaction of CO2 and ethylene oxide catalyzed by metal–salen complexes: effect of the metal center and the axial ligand

Abstract

Quantum mechanical study of the reaction of CO 2 and ethylene oxide catalyzed by metal-salen complexes: effect of the metal center and the axial ligand Abstract Density functional theory calculations were used to evaluate the thermochemistry of plausible elementary steps for the reaction of CO 2 with ethylene oxide catalyzed by metal-salen complexes consisting of Co, Cr, Mn, Fe, Al and Zn. The effect of the axial ligands on the energies of reaction was studied using chlorine and 4-dimethylaminopyridine (DMAP). This analysis was performed using UOPBE/LANL2DZ to screen the plausible reaction intermediates. The most favorable intermediates were then studied with B3LYP/6-311 g**/LANL2DZ in gas phase and in dichloromethane to evaluate the method and solvent effect on their reaction energies and geometries. Our results demonstrated that when chlorine is the axial ligand, the formation of CO 2 -epoxide-salen complexes was an endothermic reaction for all metal-salen complexes considered. However, the energies of reaction decreased for these complexes with DMAP as axial ligand. While differences were found in the reaction energies with the two methods, both methods yield similar minimum energy structures on the intermediates that were analyzed. The most energetically favorable intermediates for the coupling of CO 2 and ethylene oxide obtained when the solvent was taken into account were the complexes with Al as metal center and DMAP as axial ligand. However, the inclusion of dichloromethane as a solvent did not have a significant effect in the reaction energies compared to the vacuum system. Our results indicated that the axial ligand impacts the electronic properties of the catalyst, such as the HOMO and LUMO surfaces, Electronic supplementary material The online version of this article (

A DFT Exploration of Efficient Catalysts Based on Metal‐Salen Monomers for the Cycloaddition Reaction of CO2 to Propylene Oxide

“…The mechanism for such experiments was further elucidated in our previous theoretical calculations . Moreover, Zn II ‐Salen and Cr III ‐Salen exhibit high activities and high yields in cycloaddition reactions, and their activities can be affected by different complexes . The mechanisms of the cycloaddition reactions of CO 2 to epoxides catalysed by Zn II ‐Salen and Cr III ‐Salen have also been studied, confirming the low energy barriers in the reactions .…”

“…[23] Moreover, Zn II -Salen and Cr III -Salen exhibit high activities and high yields in cycloaddition reactions, and their activities can be affected by different complexes. [24][25][26][27][28] The mechanisms of the cycloaddition reactions of CO 2 to epoxides catalysed by Zn II -Salen and Cr III -Salen have also been studied, confirming the low energy barriers in the reactions. [29,30] Apart from the M-Salen mentioned above, there are few reports about other M-Salens or M-CMPs to convert CO 2 and epoxides to cyclic carbonates.…”

Insights into the Mechanism of Carbon Dioxide and Propylene Oxide Ring-Opening Copolymerization Using a Co(III)/K(I) Heterodinuclear Catalyst

“…The Co­(III)­K­(I) catalyst is a rare example of a dinuclear complex active using propylene oxide/carbon dioxide and operating without any cocatalyst. Regardless of the catalyst structure, there are very few other investigations into the PO/CO 2 ROCOP mechanism, the majority of studies apply DFT calculations to investigate specific steps such as epoxide binding, CO 2 insertion, − chain dissociation, or backbiting reactions, independent of the complete cycle. One rationale for these “simplified” investigations is that the presence of the cocatalyst complicates the active site speciation.…”