Hydrocarbon oxidation by homogeneous and heterogeneous non-heme iron (III) catalysts with H2O2

Homogeneous (LFeIII) and heterogeneous (LFeIII·SiO2) [L = 3-{2-[2-(3-hydroxy-1,3-diphenyl-allylideneamino)-ethylamino]-ethylimino}-1,3-diphenyl-propen-1-ol] catalysts have been synthesized and evaluated catalytically. In CH3CN, both the homogeneous and heterogeneous catalysts were efficient in alkene oxidations. Cyclohexane oxidation provides total yield of 12.1% and 7.3% with an alcohol/ketone (A/K) ratio of 1.75 and 1.60 by the LFeIII and the LFeIII·SiO2 catalysts respectively. UV–vis kinetic data suggest formation of LFeIII–OOH species. EPR data show that in the presence of CH3CN, low-spin FeIII (S = 1/2) centers are formed, which are responsible for the catalytic activity. The heterogeneous LFe·SiO2 catalyst, tested up to 5 re-uses, shows a total yield loss ∼4% per use, providing the same distribution of oxidation products.