EPOXIDATION OF OLEFINS CATALYZED BY FE(III) SCHIFF-BASE COMPLEXES AS CATALYST

The epoxidation of olefins using tri- and tetradentate ligand-containing Fe(III) complexes as catalyst and iodosylbenzene as oxidant have been studied. Cyclohexene gave cyclohexene oxide, cyclohexenol and cyclohexenone. At higher concentrations of catalyst, low yield but high selectivity of epoxide was observed. The yield of epoxide increases with increasing concentration of cyclohexene. The relative rates of epoxidation of cyclo-olefins exhibit the order norbornene > cyclooctene > cycloheptene > cyclohexene > cyclopentene. The addition of pyridine was found to increase the yield of epoxide. The addition of NaH2PO4 and NaHCO3 also increases the yield of the epoxide; the addition of cetyltrimethylammonium bromide completely inhibits the epoxidation, while addition of sodium lauryl sulphate slightly retards the yield of the epoxide. These studies point to a mechanism in which formation of oxoiron(V) and oxoiron(IV) cation radical takes place. © 1990.