Synthesis, structure and catalytic activity of bis(phenoxyiminato)iron(III) complexes in coupling reaction of CO2 and epoxides

Abstract

Here we described the synthesis and characterization of a series of new bis(phenoxyiminato)Fe(III)-chloro complexes using a variety of techniques, including: elemental analysis, IR-, MS(EI), UV–Vis-spectroscopy, and X-ray diffraction. A solid-state structure of bis(N-salicylidene-3-phenylpropylamine)iron(III)chloride reveals a distorted square-pyramid coordination with crystallographic C2-symmetry wherein chloride occupies the axial position. Isolated complexes were also evaluated as catalysts for a coupling reaction of CO2 and various epoxides, including propylene, 1-hexene, cyclohexene and styrene oxides to form corresponding cyclic carbonates. Accordingly, the ligand structure and the solvent used influenced the catalytic activity and marked enhancement in the activity was observed using DMF as a solvent. Under optimized reaction conditions (145°C and 10bar of CO2) bis(N-salicylidene-2-phenylethylamine)iron(III)chloride gave cyclopropylene carbonate with considerable high TON value (1029) within 3h.