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with TBHP and respectively, in acetonitrile/DMSO.
352
Formation of a perferryl intermediate from the Fe(III)-peroxo
species were thought unlikely, since the PMA
-
ligand framework is incapable of
stabilizing the high-valent iron center and oxidation of both cyclohexene and
norbornene yielded only the allylic oxidation products and the exo-epoxide,
respectively. The homolytic cleavage of the O-O bond in to
form was thought to take part in the catalytic process by forming
cyclohexyl and
t
-butoxy radicals. deVries
et al.
used a ligand 2,6-bis[methoxybis(2-
pyridyl)methyl]pyridine (L) and observed by ESM the transient formation of a
from Kim
et al.
proposed the structure
and later for an intermediate
detected in the solution of and It was shown by
Raman spectroscopy that the O-O bond is significantly weakened as indicated by the
lowest 790 Roelfes
et al.
synthesized pentadentate ligand N4Py with
which the purple low-spin
was generated by the reaction
and Fe(II) complexes.
432
with
Mialane
et al.
also confirmed the formation of
with L
=
N,N,N'
-tris(2-pyridylmethyl)-
N'
-methyl-ethane-1,2-
diamine) by ESI-MS.
433
Formation of high-spin blue species from low-spin
complexes was reported by Jensen
et al..
49
They found that purple
complex (bztpen:
N
-benzyl-
N,N',N'
-tris(2-pyridylmethyl)-ethane-1,2-
diamine) can be reversibly deprotonated to give transient blue species showing
spectroscopic
)-peroxide complexes,
or others. Similarly, Simaan
et al.
reported the formation of a complex from a purple low-spin complex
upon adding a base (L:
N
-methyl-
N,N,N
-tris(2-pyridylmethy])-
properties
consistent
with
iron(
III
,2-diamine).
50
The complex was characterized by the UV/Vis change from
534 to 740 nm, by the ESR change from
g =
7.5 and 5.9 to 9.3 and 4.3, and by ESI-
MS at
m/z =
435. Ho
et al.
gave a resonance Raman evidence for the
interconversion between and 632 and 790 for
and 495 and 817 cm
-1
for The former
has activity for the hydroxylation of cyclohexane, but the latter looses it, supporting
the hypothesis that protonation of the peroxo species activates it for participation in
the oxygen activation mechanisms by iron enzymes. Similar results for
identification of two peroxo complexesas shown in Fig. 16 were reported by Simaan
et al..
51,52
ethane-
1
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