The reactivity of well defined diiron(III) peroxo complexes toward substrates: addition to electrophiles and hydrocarbon oxidation.
The reactivity of previously reported peroxo adducts [Fe(mu-O2)(mu-L)(O2CPhCy)2(1-Bu-Im)2] (1), and [Fe(mu-O2)(mu-L)(O2CPhCy)2(py)2] (2), where L is a dinucleating ligand based on the m-xylylenediamine bis(Kemp's triacid imide), toward a variety of substrates is described. These studies were performed to probe the electronic properties of 1 and 2 and evaluate their potential as selective hydrocarbon oxidants. Compound 1 is nucleophilic at -77 degrees C, reacting with phenols and carboxylic acids to liberate hydrogen peroxide, whereas the less electron-rich pyridine analogue 2 is unreactive toward both reagents. By contrast, neither reacts at -77 degrees C with electrophilic reagents such as olefins or triphenylphosphine, or with weak hydrogen atom donors such as dimethylbenzylamine. When solutions of 1 are warmed to room temperature in solvents such as THF, toluene, and cyclopentane, mixtures of alcohol and ketone products derived from the solvent are formed. A detailed investigation of cyclopentane oxidation strongly points to a radical autoxidation pathway. These results are discussed in the context of the selective hydroxylation chemistry that occurs at the carboxylate-bridged diiron centers in soluble methane monooxygenase.
Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139, USA.
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DD
LeCloux
A M
AM
Barrios
S J
SJ
Lippard
D002849:Chromatography, Gas; D005296:Ferrous Compounds / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D006838:Hydrocarbons / Q000378:metabolism*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D010100:Oxygen / Q000378:metabolism*; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman; D013696:Temperature
D005296:Ferrous Compounds; D006838:Hydrocarbons; D010100:Oxygen