Stable Fe(iii) phenoxyimines as selective and robust CO₂/epoxide coupling catalysts

Area of Science:

• Organometallic Chemistry
• Catalysis
• Green Chemistry

Background:

• Developing efficient catalysts for carbon dioxide utilization is crucial for sustainable chemical processes.
• Iron complexes offer a cost-effective and environmentally benign alternative to precious metal catalysts.

Purpose of the Study:

• To synthesize and characterize novel phenoxyimine Fe(III)Cl complexes.
• To evaluate their catalytic performance in the cycloaddition of CO2 to epoxides for cyclic carbonate synthesis.

Main Methods:

• Synthesis and X-ray crystallographic analysis of three Fe(III) complexes with varying ortho-substituents.
• Testing catalytic activity in CO2/epoxide coupling under various conditions (temperature, pressure, co-catalyst).

Main Results:

• All synthesized Fe(III) complexes exhibited high catalytic activity for cyclic carbonate formation.
• Catalyst performance correlated with the electron-withdrawing nature of the ortho-substituent, with the chloro-substituted complex showing the highest activity (TOF up to 900 h-1).
• The chloro-substituted catalyst demonstrated robustness, functioning under air, in the presence of water, and with high substrate loading.

Conclusions:

• Phenoxyimine Fe(III)Cl complexes are effective catalysts for CO2/epoxide coupling.
• The electronic properties of the ligand substituents significantly influence catalytic activity and Lewis acidity.
• These iron catalysts represent a promising advancement in sustainable cyclic carbonate synthesis.