The Catalytic Function of Nonheme Iron (III) Complex for Hydrocarbon Oxidation

Abstract

A detailed catalytic study of LFe(III)Cl (where L = 3-{2-[2-(3-hydroxy-1,3-diphenyl-allylideneamino)-ethylamino]-ethylimino}-1,3-diphenyl-propen-1-ol) for hydrocarbon oxidation was carried out, focusing on the role of solvent, atmospheric dioxygen, and oxidant on catalytic efficiency. The data showed that LFe(III)Cl catalyst was efficient in homogeneous hydrocarbon oxidations providing significant yields. Moreover, tert-BuOOH provided comparable oxidation yields with H(2)O(2), slightly favoring the formation of alcohols and ketones versus epoxides. Dioxygen intervened in the catalytic reaction, influencing the nature of oxidation products. The polarity of solvent strongly influenced the reaction rates and the nature of oxidation products. A mechanistic model is postulated assuming that LFe(III)Cl functions via the formation of iron-hydroperoxo-species, followed by a radical-based mechanistic path.

Figure 1

(a) Cis-cyclooctene oxidation is catalysed by LFe^IIICl at varied Substrate-Oxidant molar ratio in CH₃CN with H₂O₂. (b) Cyclohexene oxidation is catalysed by LFe^IIICl at varied Substrate-Oxidant molar ratio in CH₃CN with H₂O₂. (c) Styrene oxidation is catalysed by LFe^IIICl at varied Substrate-Oxidant molar ratio in CH₃CN with H₂O₂. (d) Cyclohexane oxidation is catalysed by LFe^IIICl at varied Substrate-Oxidant molar ratio in CH₃CN with H₂O₂. For all figures The given ratio is catalyst : oxidant : substrate.

Figure 2

Bar chart representation of oxidations catalyzed by LFe^IIICl with H₂O₂ in CH₃CN under atmospheric air and under Ar.

Figure 3

Time-dependent reaction profiles for cyclohexene oxidation catalysed by LFe^IIICl with H₂O₂ in CH₃CN and tert-amylalcohol.

Figure 4

Distribution of oxidation products catalyzed by LFe^IIICl, (a) in tert-amylalcohol with H₂O₂, (b) in CH₃CN with H₂O₂, and (c) in CH₃CN with tert-BuOOH. See Table 2 for further details.

Scheme 1

Schematic representation of ligand [3-{2-[2-(3-hydroxy-1,3-diphenyl-allylideneamino)-ethylamino]-ethylimino}-1,3-diphenyl-propen-1-ol] (L).

Scheme 2

Schematic representation of detected byproducts.