High-valent iron dimers

High-valent iron also occurs in -nitrido bridged dimers with linear [Fe °-N=Fe" ]" and [Fe =N=Fe ] " cores [209, 210] (and references therein). Such compounds have been prepared first by thermolysis [247] or photolysis [248] of iron(III)-porphyrin complexes with an azide ligand, (N3). Mixed-valent iron-nitrido porphyrin dimers exhibit valence delocalization as can be inferred from the... 

The non-heme enzyme methane monooxygenase (MMO) from methanotropic bacteria catalyzes the hydroxylation of methane to methanol. Methane is most difficult to hydroxylate and cytochrome P-450 cannot perform this reaction. MMO consists of three components. Component A is a dimer with subunits of dinuclear iron with monooxygenase activity. Components B and C are electron donor and transfer sites. Like cytochrome P-450, a high valent iron-oxo complex is proposed for component A in MMO. This species abstracts a H atom from CH4 to generate a CHs" radical. 

Since metMb is not easily (if at all) further oxidized to a higher valent iron, its reaction with OH- does not appear to affect the iron, but apparently involves the amino acid moieties on the surface of the protein. Their involvement is supported by the formation of dimeric metMb at high doses. 

In MeCN at —40°C, low-spin iron(III)iron(IV) compounds [Fe2(/i-0)2(TPA)2] + (39b) and (40b) quantitatively oxidize 2,4-di-tert-butylphenol to the corresponding phenoxyl radical, which dimerizes to form the 2,2 -biphenol product. Hydroxylation or desaturation of hydrocarbons can also be achieved by these high-valent species, which act as one-electron oxidants. A KIE of 20 was obtained for the second-order reaction between (39b) and ethylbenzene. Activation of the benzylic C—bond is a major component of the rate-determining step in both hydroxylation and desaturation, as demonstrated by product analysis. A mechanistic model was proposed... 

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