Enhanced Catalytic Activity and Unexpected Products from the Oxidation of Cyclohexene by Organic Nanoparticles of 5,10,15,20-Tetrakis-(2,3,4,5,6-pentafluorophenyl)porphyrinatoiron(III) in Water by Using O-2

The catalytic oxidation of alkenes by most iron porphyrins using a variety of oxygen sources, but generally not dioxygen, yields the epoxide with minor quantities of other products. The turnover numbers for these catalysts are modest, ranging from a few hundred to a few thousand depending on the porphyrin structure, axial ligands, and other reaction conditions. Halogenation of substituents increases the activity of the metalloporphyrin catalyst and/or makes it more robust to oxidative degradation. Oxidation of cyclohexene by 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphyrinato iron(III), ([Fe-III(tppf(20))]) and H2O2 is typical of the latter: the epoxide is 99% of the product and turnover numbers are about 350.([1-4]) Herein, we report that dynamic organic nanoparticles (ONPs) of [Fe-III(tppf(20))] with a diameter of 10 nm, formed by host-guest solvent methods, catalytically oxidize cyclohexene with O-2 to yield only 2-cyclohexene-1-one and 2-cyclohexene-1-ol with approximately 10-fold greater turnover numbers compared to the non-aggregated metalloporphyrin in acetonitrile/methanol. These ONPs facilitate a greener reaction because the reaction solvent is 89% water and O-2 is the oxidant in place of synthetic oxygen sources. This reactivity is unexpected because the metalloporphyrins are in close proximity and oxidative degradation of the catalyst should be enhanced, thus causing a significant decrease in catalytic turnovers. The allylic products suggest a different oxidative mechanism compared to that of the solvated metalloporphyrins. These results illustrate the unique properties of some ONPs relative to the component molecules or those attached to supports.