19547-01-4Relevant articles and documents
Highly reactive porphyrin-iron-oxo derivatives produced by photolyses ofmetastable porphyrin-iron(IV) diperchlorates
Pan, Zhengzheng,Wang, Qin,Sheng, Xin,Horner, John H.,Newcomb, Martin
experimental part, p. 2621 - 2628 (2009/09/07)
Photolyses of metastable porphyrin-iron(IV) diperchlorates in laser flash photolysis reactions gave highly reactive transients. The systems studied were 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetramesitylporphyrin (TMP), and 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP). The new species, which decayed within milliseconds in acetonitrile solutions, were shown to react with organic substrates by oxo-transfer reactions involving insertions into carbon-carbon double bonds of alkenes and styrenes or benzylic carbon-hydrogen bonds of arenes. The order of reactivity was OEP > TPP > TMP. Second-order rate constants for reactions with several substrates at 22 °C were determined; representative values of rate constants for the TPP derivative were k = 8.6 × 105 M-1 s-1 for styrene, k = 2.5 × 106 M-1 s-1 for cyclohexene, and k = 7.7 × 104M-1 s-1 for ethylbenzene. These porphyrin-iron-oxo transients reacted 4-5 orders of magnitude faster than the corresponding iron(IV)-oxo porphyrin radical cations with rate constants similar to those of porphyrin-manganese(V)-oxo derivatives. Rate constants for oxidations of benzylic C-H positions of arenes correlated with the C-H bond dissociation energies, and Hammett correlations for reactionswith substituted styrenes had p+ values ranging from-0.5 to- 0.7, reflecting electrophilic character of the oxidants and their high reactivity. On the basis of their unique UV-visible spectra, high reactivities, and oxo-transfer properties, the new transients are tentatively identified as porphyrin-iron(V)-oxo perchlorates, electronic isomers (or valence tautomers) of well-known iron(IV)-oxo porphyrin radical cations.
Modeling nonheme diiron enzymes: Hydrocarbon hydroxylation and desaturation by a high-valent Fe2O2 diamond core
Kim,Dong,Que L.
, p. 3635 - 3636 (2007/10/03)
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