Mechanistic Insights into Cycloaddition of CO₂ with Epoxide Catalyzed by a Bimetallic (Salen)Fe(II)Cl₂ Complex with/without a Cocatalyst

Abstract

The cycloaddition of carbon dioxide (CO2) with propylene oxide (PO), with bimetallic (salen)Fe(II)Cl2 complex as the catalyst, was studied by using BP86/TZVP method. The calculated results revealed that the catalytic process exhibited a bimetallic cooperative mechanism, and a synergetic effect was observed between one Fe center and the axial ligand of chloride anion in the PO ring‐opening. The axial ligand of chloride anion acted as a cocatalyst. Moreover, a cocatalyst, i. e., NBu4Cl, has been introduced to the catalytic process. The catalytic process proceeded according to a monometallic mechanism, and chloride anion from NBu4Cl acted as a nucleophile in the PO ring‐opening. In addition, the energetic span model was applied to evaluate the catalytic efficiency of both catalytic systems. This current study provided novel insights into the molecular behavior of transition metal catalysts for the cycloaddition of CO2 with epoxides.

Unraveling the role of internal–external metal substitution in Zn3[Co(CN6)]2 for the styrene oxide–CO2 cycloaddition reaction

“…TBAB has a positive charge distributed in the hydrogen atoms closest to the central nitrogen and not in the latter. 76…”

Recent Advancements in Metal‐catalysts Design for CO2/Epoxide Reactions

“…The dinuclear iron(III) complex 26 supported by a cyclic sale-type ligand have been also studied through DFT calculations evidencing in this case a different behavior with or without the presence of a cocatalyst (TBAC) (Figure 7). [50] As a matter of fact, in the absence of the external nucleophile a bimetallic, concerted mechanism is operative with the chlorine atom of the second metal center involved in the ring-opening of the epoxide activated on the first metal center, conversely, in the presence of the cocatalyst only one metal center is active in the catalytic cycle. The catalytic cycle in the presence of external nucleophile is energetically favored respect to the bimetallic mechanism and therefore is the only one active in the presence of the cocatalyst.…”

“…The dinuclear iron(III) complex 26 supported by a cyclic sale‐type ligand have been also studied through DFT calculations evidencing in this case a different behavior with or without the presence of a cocatalyst (TBAC) (Figure 7). [50] …”