Iron(III) Versatile Catalysts for Cycloaddition of CO2 to Epoxides and Epoxidation of Alkenes

Fe(III) complexes with tridentate pyridine-imine-phenolato ligands differing in the chain length between the imine and pyridine groups (2-methylpyridine L1 and 2-ethylpyridine L2) have been synthesized. New complex [Fe(L2)(2)] ClO4 (2) was characterized by X-ray diffraction and spectroscopic techniques. [Fe(L1)(2)] ClO4 (1) and 2 form active catalysts for the cycloaddition of CO2 to epoxides and for the epoxidation of alkenes. Catalytic systems with the more flexible skeleton (2) in combination with tetrabutylammonium bromide (TBAB) were more active than 1/TBAB in the cycloaddition of CO2 to epoxides. TOFs up to 900 h(-1) for the selective synthesis of styrene carbonate and 3640 h(-1) for the synthesis of glycidol carbonate were obtained using 2/TBAB at low catalyst loadings (0.025 mol %). Additionally, 2 was also active in the epoxidation of styrene derivatives such as trans-stilbene (conversion 88%) and trans-bmethylstyrene (conversion 100%) using tert-butylhydroperoxide as oxidant at 60 degrees C in acetonitrile. Epoxidation of styrene and cyclohexene proceed at low conversions.