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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
Author(s) -
Smeureanu Gabriela,
Aggarwal Amit,
Soll Clifford E.,
Arijeloye Julius,
Malave Erik,
Drain Charles Michael
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901086
Subject(s) - cyclohexene , chemistry , catalysis , epoxide , photochemistry , solvent , porphyrin , turnover number , allylic rearrangement , yield (engineering) , cyclohexene oxide , oxygen , medicinal chemistry , organic chemistry , materials science , metallurgy
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 H 2 O 2 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.