Comparison of the kinetic parameters measured in both
DMF/H2O (3 : 1) and DMF/D2O (3 : 1) revealed the presence
of solvent isotope effect (SIE) (Table 1 and see ESIw, Fig. S3).
The measured values of SIE for the ACCH, ALAH and
AIBH oxidation rates are 3.9, 2.5 and 1.3, respectively,
suggesting changes in hydrogen bonding between the reactants
and the transition state. On the basis of the magnitude of the
observed solvent kinetic isotope effects (SIE values of o4)
ET–PT mechanism can be proposed for the iron salen
catalyzed amino acid oxidation reactions.
Scheme 1 Proposed mechanism for the iron-catalysed oxidation of
ACCH.
To get a direct evidence for the fact that high-valent oxoiron
species are capable for the amino acid oxidation, we have chosen
the [FeII(N4Py)(ClO4)2] (2) complex as possible catalyst, because
its oxoiron(IV) intermediate was isolated and fully characterised
ethylene, or the corresponding carbonyl compounds and thus
serves as one of the first functional model for 1-aminocyclo-
propane-1-carboxylic acid oxidase.
The authors express their thanks for the financial support of
the CNRS (Centre National de la Resherche Scientifique), the
Hungarian Scientific Research Fund (OTKA PD75360,
by various methods (UV-Vis, Mossbauer, ES-MS, EXAFS and
¨
X-ray).5 By comparing the acetone production rates employing 2
as catalyst, the conversion of AIBH to acetone was found to be
2–3-fold faster than that obtained with 1 (Table 1). The measured
SIE values for both catalysts above are identical within
experimental error, with values B1.4, suggesting a similar
rate-determining step (see ESIw, Fig. S4). Fig. 4 shows the time
course for the decay of [FeIVQO(N4Py)]2+ (691 nm, 70%)
formed by the addition of ca. 10 equivalents of H2O2 to the
AIBH-containing reaction mixture.5
´
OTKA K67871 and OTKA K75783), COST and TET.
Notes and references
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Salen-containing system, its possible participation in the
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Fig. 4 (a) Visible spectral change for the decay of FeIVQO species
derived from the reaction of 2 and hydrogen peroxide in the presence
of AIBH in DMF/water at 25 1C. [AIBH] = 1.0 ꢁ 10ꢀ2 M,
[complex] = 1.0 ꢁ 10ꢀ3 M, [H2O2] = 1.0 ꢁ10ꢀ2 M. (b) Time
dependent conversion of FeIVQO species under the conditions
described above, monitored at 691 nm.
c
This journal is The Royal Society of Chemistry 2010
Chem. Commun., 2010, 46, 7391–7393 7393