Functional model oxygenations by nonheme iron complexes - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 187

(mep : N , N ' -dimethyl- N,N' -bis(2-pyridylmethyl)-
ethane, 1,2-diamine) in the presence of

and acetic acid. 228

Formation of the

carboxylate-bridged diiron(III) as an active species was indicated.

4.1.2 Monooxygenation by Diiron Complexes with Molecular Oxygen
Very little has been reported on the monooxygenation with in the presence
or absence of reductants. Kitajima et al. reported the monooxygenation with by a

dinuclear iron complex in the presence of and Zn

powder 229 and with Hfacac and Zn powder 230
The latter exhibited
the greater activity than the former for the dioxygen hydroxylation of alkanes (n-
pentane, cyclohexane, adamantane) and arenes (benzene, toluene, chlorobenzene).
Wang et al. have synthesized dinuclear Fe(II) macrocyclic complexes with
two dinucleating ligands, [24]RBPyBc and [30]RBBPyBc, containing phenolate
pyridine, bipyridine, and amino phenolate groups. 231 The complexes react with
molecular oxygen and catalyze the monooxygenation of cyclohexane and
adamantane in the presence of a two-electron donor, Alcohols are the main
product rather than ketones (CyOH/CyO = 1.06 - 1.94). The proposed mechanism
involves the formation of a peroxo-bridged dinuclear Fe(III) complex that is
converted to a high-valent iron species bridged by an group as a direct

intermediate for the reaction with hydrocarbons.

4.2 Monooxygenation by Diiron Complexes
Dioxygen diiron complexes have been synthesized by mimicking the
probable intermediate structures in methane monooxygenase oxygenations.
Examples are summarized in the recent review. 232-235 One is the diamond
core type and the other is the peroxo type. Recently, an unusual
species has been suggested in the reaction of with carboxylate-
bridged diiron(II,II) paddlewheel complexes, but its role in the oxygenation has not
been clarified. 234, 236