The oxidation of ethylbenzene by dioxygen catalysed by supported iron porphyrins derived from iron(III) tetrakis(pentafluorophenyl)porphyrin

Chloromethylated poly(styrene) and chloropropylated silica gel have been re acted with alpha,omega -diamines to give diamine modified catalyst supports which have then been covalently attached to iron(III) tetrakis(pentafluoro phenyl)porphyrin (FeTF5PP). In this way the diamino groups provide a simple linker/spacer unit between the support and the catalyst. The diamino-silic a has been further modified using trimethylsilyl chloride and by acetylatio n or acid washing. The polarities of the modified inorganic and organic sup ports have been measured using Reichardt's dye. Spectroscopic studies revea l that with all the supported catalysts, except that on acid washed diamino -silica where the amines are protonated, the diamino groups reduce the iron (III) porphyrin to iron(II). The supported iron porphyrins have been used t o catalyse the oxidation of ethylbenzene by dioxygen. These reactions give the same three products, 1-phenylethyl hydroperoxide, 1-phenylethanol and a cetophenone, as the analogous homogeneous oxidation using FeTF5PP, suggesti ng that they proceed by the same mechanism, however, in general they are sl ower. The overall product yields are limited by the stability/activity of t he iron porphyrin and these in turn are very dependent on the length of the linker, the catalyst loading and the microenvironment provided by the supp ort. The role of the diamino groups in the oxidations is discussed.