Mononuclear Nonheme High-Spin Iron(III)-Acylperoxo Complexes in Olefin Epoxidation and Alkane Hydroxylation Reactions

Article abstract of DOI:10.1021/jacs.5b13500

Mononuclear nonheme high-spin iron(III)-acylperoxo complexes bearing an N-methylated cyclam ligand were synthesized, spectroscopically characterized, and investigated in olefin epoxidation and alkane hydroxylation reactions. In the epoxidation of olefins, epoxides were yielded as the major products with high stereo-, chemo-, and enantioselectivities; cis- and trans-stilbenes were oxidized to cis- and trans-stilbene oxides, respectively. In the epoxidation of cyclohexene, cyclohexene oxide was formed as the major product with a kinetic isotope effect (KIE) value of 1.0, indicating that nonheme iron(III)-acylperoxo complexes prefer C? - ?C epoxidation to allylic C-H bond activation. Olefin epoxidation by chiral iron(III)-acylperoxo complexes afforded epoxides with high enantioselectivity, suggesting that iron(III)-acylperoxo species, not high-valent iron-oxo species, are the epoxidizing agent. In alkane hydroxylation reactions, iron(III)-acylperoxo complexes hydroxylated C-H bonds as strong as those in cyclohexane at -40 °C, wherein (a) alcohols were yielded as the major products with high regio- and stereoselectivities, (b) activation of C-H bonds by the iron(III)-acylperoxo species was the rate-determining step with a large KIE value and good correlation between reaction rates and bond dissociation energies of alkanes, and (c) the oxygen atom in the alcohol product was from the iron(III)-acylperoxo species, not from molecular oxygen. In isotopically labeled water (H₂¹⁸O) experiments, incorporation of ¹⁸O from H₂¹⁸O into oxygenated products was not observed in the epoxidation and hydroxylation reactions. On the basis of mechanistic studies, we conclude that mononuclear nonheme high-spin iron(III)-acylperoxo complexes are strong oxidants capable of oxygenating hydrocarbons prior to their conversion into iron-oxo species via O-O bond cleavage.

Full text of DOI:10.1021/jacs.5b13500

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Article
Mononuclear Nonheme High-Spin Iron(III)-Acylperoxo Complexes
in Olefin Epoxidation and Alkane Hydroxylation Reactions
Bin Wang, Yong-Min Lee, Martin Clémancey, Mi Sook Seo,
Ritimukta Sarangi, Jean-Marc Latour, and Wonwoo Nam
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.5b13500 • Publication Date (Web): 27 Jan 2016
Downloaded from http://pubs.acs.org on January 29, 2016
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Mononuclearꢀ Nonhemeꢀ High‐Spinꢀ Iron(III)‐Acylperoxoꢀ
Complexesꢀ inꢀ Olefinꢀ Epoxidationꢀ andꢀ Alkaneꢀ Hydroxylationꢀ
Reactionsꢀ
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†
†
‡
†
,¶
,‡
Bin Wang, Yong-Min Lee, Martin Clémancey, Mi Sook Seo, Ritimukta Sarangi,* Jean-Marc Latour,* and
,†
Wonwoo Nam*
†
Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
‡
Univ. Grenoble Alpes, LCBM/PMB and CEA, IRTSV/CBM/PMB and CNRS, LCBM UMR 5249, PMB 38000 Grenoble, France
¶
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California
94025-7015, United States
ABSTRACT: Mononuclear nonheme high-spin iron(III)-acylperoxo complexes bearing an N-methylated cyclam ligand were synthesized,
spectroscopically characterized, and investigated in olefin epoxidation and alkane hydroxylation reactions. In the epoxidation of olefins,
epoxides were yielded as the major products with high stereo-, chemo-, and enantioselectivities; cis- and trans-stilbenes were oxidized to cis-
and trans-stilbene oxides, respectively. In the epoxidation of cyclohexene, cyclohexene oxide was formed as the major product with a kinetic
isotope effect (KIE) value of 1.0, indicating that nonheme iron(III)-acylperoxo complexes prefer C=C epoxidation to allylic C−H bond
activation. Olefin epoxidation by chiral iron(III)-acylperoxo complexes afforded epoxides with high enantioselectivity, suggesting that
iron(III)-acylperoxo species, not high-valent iron-oxo species, are the epoxidizing agent. In alkane hydroxylation reactions, iron(III)-
o
acylperoxo complexes hydroxylated C−H bonds as strong as those in cyclohexane at −40 C, wherein (a) alcohols were yielded as the major
products with high regio- and stereoselectivities, (b) activation of C−H bonds by the iron(III)-acylperoxo species was the rate-determining
step with a large KIE value and good correlation between reaction rates and bond dissociation energies of alkanes, and (c) the oxygen atom in
1
8
the alcohol product was from the iron(III)-acylperoxo species, not from molecular oxygen. In isotopically labeled water (H
2
O) experiments,
18
18
incorporation of O from H
2
O into oxygenated products was not observed in the epoxidation and hydroxylation reactions. On the basis of
mechanistic studies, we conclude that mononuclear nonheme high-spin iron(III)-acylperoxo complexes are strong oxidants capable of
oxygenating hydrocarbons prior to their conversion into iron-oxo species via O−O bond cleavage.
INTRODUCTION
have been well investigated recently in various oxidation reactions,
including the oxidation of olefins and the C−H bond activation
reactions, with synthetic iron(IV)-oxo complexes under
Metal-oxygen intermediates that are involved in the catalytic
oxidation of organic substrates by O -activating metalloenzymes
and their model compounds have been investigated intensively
over the several decades in heme systems and more recently in
mononuclear nonheme iron systems. In cytochromes P450
2
2b,3,5
stoichiometric conditions.
For example, factors affecting
reactivities and reaction mechanisms of the nonheme iron(IV)-oxo
complexes, such as the structural and electronic effects of
supporting and axial ligands, the spin states of iron(IV) ion, and the
binding of proton and redox-inactive metal ions, have been well
1-3
(
P450) and iron porphyrin models, high-valent iron(IV)-oxo
porphyrin π-cation radicals, referred to as compound I (Cpd I),
have been widely accepted as reactive intermediates in the catalytic
oxygenation reactions. Indeed, Cpd I has been captured,
3,5
addressed in the reactivity studies. Thus, the chemistry of the
nonheme iron-oxo intermediates has been advanced greatly since
the first two reports on the enzymatic and biomimetic studies
2
spectroscopically characterized, and investigated in reactivity
6
4
appeared in 2003.
studies in P450. In iron porphyrin models, the reactivity and
mechanistic studies of synthetic Cpd I complexes have shown that
Cpd I is a highly reactive and powerful oxidant in various oxidation
reactions, including olefin epoxidation and alkane hydroxylation.
In addition to the high-valent iron-oxo species, other iron-
oxygen intermediates, such as iron(III)-superoxo, -peroxo, and -
hydroperoxo species, have been considered as active oxidants in
2
1d,7
both heme and nonheme iron systems. For example, iron(III)-
hydroperoxo species have been invoked as “second-electrophilic
The high-valent iron(IV)-oxo intermediates have also been
identified and characterized spectroscopically and/or structurally
in mononuclear nonheme iron enzymes and synthetic nonheme
7
oxidants” in the catalytic oxidation of organic substrates by P450.
3
However, experimental/theoretical mechanistic studies revealed
iron complexes. The reactivities of the nonheme iron-oxo species
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Scheme 1. Mononuclear Nonheme High-Spin Iron(III)-
Acylperoxo Complex in Olefin Epoxidation and Alkane
Hydroxylation Reactions.
oxidants that effect the olefin epoxidation and alkane hydroxylation
reactions.
RESULTS AND DISCUSSION
Generation and Characterization of Iron(III)-Acylperoxo
II
Complexes. Treatment of [Fe (13-TMC)(CF
3
SO ) ] with 4 equiv
3
2
of peroxycarboxylic acids, such as phenylperoxyacetic acid (PPAA),
peroxybenzoic acid (PBA), m-chloroperoxybenzoic acid (m-
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CPBA), and peroxyacetic acid (PAA), in a solvent mixture of
o
3
CF CH
2
OH and acetone (v/v = 3:1) at −40 C resulted in the
formation of blue intermediates within 30 s – 2 min; the formation
time changes slightly depending on the peracids used. These
intermediates, denoted as 1 (from the reaction with PPAA), 2
(from the reaction with PBA), 3 (from the reaction with m-CPBA),
that the iron(III)-hydroperoxo species is a sluggish oxidant in heme
8
and 4 (from the reaction with PAA), show a maximum UV-vis
absorption band at 660 nm (Figure 1a for 1; Supporting
Information (SI), Figure S1 for 2 – 4). These metastable
systems. The multiple oxidants hypothesis has been debated
intensively in nonheme iron systems as well. One example is the
reactivity of activated bleomycin (i.e., a low-spin iron(III)-OOH
species), which is the last detectable intermediate in the reaction
cycle of bleomycin and has been proposed as a plausible oxidant
o
intermediates (t1/2 = ~20 min at −40 C) were characterized using
various spectroscopic techniques, such as electron paramagnetic
resonance (EPR) spectroscopy, coldspray ionization time-of-flight
mass spectrometer (CSI-TOF MS), Mössbauer, and X-ray
absorption spectroscopy (XAS). The X-band EPR spectra of 1 – 4,
3d,9
responsible for DNA cleavage.
In biomimetic studies, a
mononuclear nonheme high-spin iron(III)-hydroperoxo complex,
III
2+
[
(14-TMC)Fe (OOH)]
(14-TMC
= 1,4,8,11-tetramethyl-
recorded in a frozen CF
exhibit signals that are characteristic of S = 5/2 Fe (Figure 1b for
1; SI, Figure S2 for 2 – 4).
3
CH
2
OH/acetone (3:1) solution at 5 K,
1,4,8,11-tetraazacyclotetradecane), was recently shown to be a
III
competent oxidant in both electrophilic and nucleophilic oxidative
13,15
1
0
In addition, EPR signals
reactions; the spin state of iron(III)-hydroperoxo species is an
V
16
1
1
corresponding to nonheme Fe (O) species (e.g., g values at ~2)
were not detected in the solutions of 1 – 4. In the CSI-TOF MS of
1 – 4, we detected mass peaks corresponding to the iron(III)-
acylperoxo species only in a small quantity (~3% mass height, data
not shown), probably due to the instability of the intermediates
under the mass spectrometer conditions. In contrast to the
iron(III)-acylperoxo complexes, we reported recently strong mass
peaks (e.g., ~30% mass height) corresponding to iron(III)-
important factor that determines their oxidizing power.
n+
Other metal-oxidant adducts (M –OX, X = IAr, OC(O)R, and
halides) have been synthesized and characterized spectroscopically
12-14
and/or structurally in biomimetic studies.
These isolated
and/or in situ generated metal-oxidant adducts were then
examined in various oxidation reactions, such as in oxygen atom
transfer (OAT) and hydrogen atom transfer (HAT) reactions. In
most cases, metal-oxidant adducts showed moderate reactivities,
implying that the metal-oxidant adducts are competent oxidants
but are much less reactive than their corresponding high-valent
III
3+ 13
iodosylarene complexes, [(13-TMC)Fe -OIAr] .
Mössbauer spectrum of 1 recorded at 5 K in a weak magnetic
field of 600 G applied parallel to the gamma rays (SI, Figure S3) is
dominated by two quadrupole doublets with an isomer shift close
to zero, which suggests the presence of iron(IV) species. In
addition, a diffuse absorption is spread over a large velocity domain
12
metal-oxo complexes. However, it has been shown very recently
that mononuclear nonheme high-spin iron(III)-iodosylarene
III
adducts bearing an N-methylated cyclam ligand, [(13-TMC)Fe -
3+
OIAr]
(13-TMC
=
1,4,7,10-tetramethyl-1,4,7,10-
–
1
–1
(
from –6 mm s to +6 mm s ). Application of a magnetic field
tetraazacyclotridecane), are highly reactive in both OAT and HAT
reactions, even more reactive than the iron(IV)-oxo complex
from 1 to 7 T, applied parallel to the gamma rays, allowed us to
confirm that the doublets correspond to S = 1 species, whose
IV
2+ 13
bearing the same supporting ligand, [(13-TMC)Fe (O)] .
Among the metal-oxidant adducts, metal-acylperoxo complexes,
1
7
parameters match those of classical iron(IV)-oxo complexes. In
addition, the magnetic field turned the broad absorption into a
sextet. The series of all four spectra were simulated within the spin
Hamiltonian formalism and the sextet assigned to an S = 5/2
n+
M –OOC(O)R, have been frequently used in investigating the
nature of the O−O bond activation to form high-valent metal-oxo
14
species (e.g., heterolytic versus homolytic O−O bond cleavage).
species accounting for approximately 36% of the total iron (Figure
Although the mechanistic studies provided valuable information on
the elucidation of the O−O bond cleavage mechanisms, the
reactivity of the metal-acylperoxo species in oxidation reactions has
been less clearly understood and remains elusive. Herein, we report
for the first time that mononuclear nonheme high-spin iron(III)-
acylperoxo complexes bearing an N-methylated cyclam ligand are
highly reactive in olefin epoxidation and alkane hydroxylation
reactions (Scheme 1); epoxides and alcohols are formed as the
major products with high chemo-, stereo-, regio-, and
enantioselectivities. We also provide experimental evidence
supporting that the iron(III)-acylperoxo complexes are active
18
1
c; SI, Table S1 for complete parameters). Accordingly, 1 is
assigned as a high-spin iron(III) species, which degrades into two
iron(IV)-oxo products (vide infra).
II
Fe K-edge XAS was performed on solutions of [Fe (13-
TMC)(CF
XAS data for [(13-TMC)Fe (O)] are included for comparison,
which shows that 1 is clearly shifted to higher energy relative to
3
SO ) ] and 1, and the data are presented in Figure 2a.
3
2
IV
2+
19
II
[
Fe (13-TMC)(CF
3
SO
3 2
) ], which is consistent with the oxidation
of the starting Fe(II) complex. A comparison of the pre-edge region
IV
2+
of 1 with [(13-TMC)Fe (O)] shows a pre-edge feature that is
significantly more intense and lower in energy by ~0.4 eV,
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II
Figure 2. (a) The normalized Fe K-edge XAS data for [Fe (13-
IV
2+
TMC)(CF
3
SO ) ] (black), 1 (red), and [(13-TMC)Fe (O)] (cyan).
3
2
The inset shows the expanded pre-edge region. (b) Non-phase-shift
corrected Fourier Transform (FT) data (black line) and the
corresponding FEFF fit (red line) to the Fe K-edge FT data for 1. The
inset shows the EXAFS data (black line) and fit (red line).
indicate that 1 is a highly distorted Fe(III) species with an Fe‒O
distance of ~1.92 Å. It is likely that a weak Fe•••O=C coordination
also exists, distorting the site but is not observed from the EXAFS
analysis. Based on the spectroscopic characterization presented
above, we are able to propose the formation of mononuclear
nonheme high-spin iron(III)-acylperoxo complexes in the
II
Figure 1. (a) UV-vis spectral changes for the natural decay of 1, which
reactions of [Fe (13-TMC)(CF
3
SO ) ] with peroxycarboxylic
3
2
III
2+
was generated within 30 s with a maximum absorption band at λ = 660
acids, such as [(13-TMC)Fe (OOC(O)CH
TMC)Fe (OOC(O)Ph)]
TMC)Fe (OOC(O)C
TMC)Fe (OOC(O)CH )] (4).
2
Ph)] (1), [(13-
[(13-
II
III
2+
nm in the reaction of [Fe (13-TMC)(CF
3
SO
3 2
)
] (1.0 mM) and
(2),
(3),
o
III
2+
PPAA (4 equiv) in CF CH OH/acetone (3:1) at −40 C. The inset
3
2
H
3
Cl)]
and
[(13-
6
4
III
2+
shows the time course monitored at 660 nm for the natural decay of 1.
(b) X-band EPR spectrum of 1 (1.0 mM). (c) Mössbauer spectra of 1
recorded at 4.2 K in a magnetic field of 7 T applied parallel to the
gamma rays. The vertical grey bars are the experimental points and the
solid black line is the theoretical spectrum generated by spin
Hamiltonian simulations. Components are assigned to 1 (red) and
Epoxidation of Olefins by Iron(III)-Acylperoxo Complexes (1 − 4).
Reactivities of the nonheme iron(III)-acylperoxo complexes (1 −
) were investigated in olefin epoxidation reactions. Addition of
4
styrene to the solutions of 1 – 4 in a solvent mixture of CF CH OH
3
2
o
IV
and acetone (v/v = 3:1) at −60 C resulted in the disappearance of
the intermediates with a first-order decay profile (Figure 3a for the
reaction of 1; SI, Figure S4 for the reactions of 2 – 4). The first
order rate constants, determined by pseudo-first-order fitting of the
kinetic data for the decay of the iron(III)-acylperoxo species,
increased linearly with the increase of the styrene concentration
(Figure 3b for the reaction of 1; SI, Figure S5 for the reactions of 2
– 4), affording second-order rate constants for the reactions of 1 – 4
two Fe products (blue and cyan).
indicating the presence of a highly distorted Fe(III) site. To
confirm this, EXAFS data were measured on 1 and the best fits are
shown in Figure 2b. The data are consistent with a first shell with
0.5 Fe−O at 1.66 Å and 0.5 Fe−O at 1.92 Å. The second shell is fit
with 4 Fe−N components at 2.12 Å (see SI, Table S2 for complete
2
fits). The σ values for all first shell parameters are somewhat higher,
(
SI, Table S3). A kinetic isotope effect (KIE) value of 1.0(1) was
obtained in the oxidation of styrene and styrene-d by 1 – 4 (Figure
b for the reaction of 1; SI, Figure S5 for the reactions of 2 – 4),
indicating that the species is a ~1:1 mixture of 1 and the [(13-
IV
2+
8
TMC)Fe (O)] forms. This is also indicated by the presence of
3
the 0.5 short Fe−O component. The pre-edge and EXAFS data
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Scheme 2. Proposed Mechanisms from the Product Analysis of
Phenylperoxyacetic Acid (PPAA).
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in heme and nonheme iron(IV or V)-oxo complexes and nonheme
13b,20,21
iron(III)-iodosylarene adducts.
Product analysis of the reaction solution of the styrene
epoxidation by iron(III)-acylperoxo complexes revealed the
formation of styrene oxide as the major product along with a small
amount of 2-phenylacetaldehyde (SI, Table S3). Similarly, the
epoxidation of styrene derivatives by 1 afforded epoxide products
predominantly (SI, Table S5). We also analyzed products derived
from the decay of PPAA in the epoxidation of styrene by 1, since
PPAA has been frequently used as an oxidant probe in proposing
O−O bond cleavage mechanisms in metal-catalyzed oxidation
reactions by peroxyacids (e.g., O−O bond heterolysis versus
22
homolysis) (Scheme 2, pathways a and b). The product analysis
revealed that phenylacetic acid was the major product (83(5)%
yield based on the amount of PPAA used) with the formation of
small amounts of toluene (1.3(5)%), benzyl alcohol (3.3(4)%),
and benzaldehyde (5.4(5)%). The observation of the phenylacetic
acid formation as the major product clearly indicates that the
epoxidation reaction by 1 occurs via the pathways a or c in Scheme
Figure 3. (a) UV-vis spectral changes observed in the reaction of 1 (1.0
o
mM) and styrene (10 mM) in CF
3
CH OH/acetone (3:1) at −60 C.
2
2
(vide infra), not via the pathway b. In the latter case, products
The inset shows the time course monitored at 660 nm. (b) Plots of
pseudo-first-order rate constants (kobs) against the concentrations of
should derive from the initial decarboxylation of a carboalkoxy
radical, such as toluene, benzyl alcohol, and benzaldehyde (see
Scheme 2, pathway b). Finally, we found that iron(III) species was
formed as the decayed product of 1 in the styrene epoxidation
reaction (SI, Figure S7).
styrene-h
second-order rate constants (k
CF CH OH/acetone (3:1) at −60 C. (c) Plots of log k against the Eox
8
(black circles) and styrene-d
8
(red circles) to determine
2
) for the oxidation of styrenes by 1 in
o
3
2
2
+
values (left panel) and Hammett parameters, σ , (right panel) of
styrene derivatives for the reactions of 1 with styrene derivatives.
In the epoxidation of cis- and trans-stilbenes by 1, cis- and
trans-stilbene oxides were formed as the major products,
respectively, with the formation of trace amounts of isomerized
products (SI, Table S5, entries 5 and 6), demonstrating that the
epoxidation reaction by 1 is highly stereoselective (Schemes 3A
indicating that the oxidation of styrene by the iron(III)-acylperoxo
complexes occurs by an OAT mechanism. The olefin epoxidation
by 1 was also investigated with para-X-substituted styrenes (X =
–1
–1 –1
Me, H, Cl, and NO
Figure S6). When the second-order rate constants, log k
2
) and meta-chloro-styrene (SI, Table S4 and
, were
and 3B). Second-order rate constants of 7.2 × 10 and 1.7 M s
were also determined in the epoxidation of cis- and trans-stilbenes
by 1, respectively (SI, Table S4 and Figure S6). In addition, when 1
was reacted with equal amounts of cis- and trans-stilbenes, the
product ratio of cis- to trans-stilbene oxide was determined to be
0.32 (SI, Table S5, entry 7). The results of the kinetic studies and
the competitive reaction lead us to conclude that 1 reacts faster
with trans-stilbene than with cis-stilbene, probably, due to the
2
plotted against the oxidation potentials (Eox) of substrates, a good
linear correlation was observed with a slope of −1.1 (Figure 3c, left
13b,20
panel).
Hammett plot of log k
In addition, a ρ value of −0.79 was obtained from the
+
2
against σ (Figure 3c, right panel). These
p
results indicate that the iron(III)-acylperoxo species possess
electrophilic character in olefin epoxidation reactions, as observed
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Scheme 4. Asymmetric Epoxidation by Chiral Iron(III)-Acylperoxo
Complexes.
Scheme 3. Epoxidation of cis-Stilbene (A), trans-Stilbene (B), and
Cyclohexene (C) by an Iron(III)-Acylperoxo Complex.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
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0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
difference in the oxidation potentials of the substrates (SI, Table
1
3b
S4).
In the epoxidation of cyclohexene by 1, a second-order rate
–
1
–1 –1
constant of 7.3 × 10
M s was determined (SI, Table S6 and
Figures S8 and S9). Interestingly, cyclohexene oxide was formed as
the major product with small amounts of allylic oxidation products,
such as cyclohexenol and cyclohexenone (SI, Table S6). This result
indicates that C=C epoxidation is the predominant reaction
(Scheme 3C, pathway a), which is different from the result of the
racemic mixture would be formed (Scheme 4A, pathways b and c).
We therefore prepared a pair of optically active peroxycarboxylic
acids possessing a chiral center, (R)-2-phenylperoxypropionic acid
cyclohexene oxidation by nonheme metal(IV)-oxo complexes (e.g.,
5e,23,24
nonheme iron(IV)-oxo complex).
In the latter reactions,
cyclohexenol, derived from the C−H bond activation (Scheme 3C,
pathway d), was the major product. In addition, while large KIE
values (e.g., KIE of >30) were observed in the oxidation of
cyclohexene and cyclohexene-d10 by nonheme metal(IV)-oxo
25
and (S)-2-phenylperoxypropionic acid, and used them in the
synthesis of chiral iron(III)-acylperoxo complexes bearing the 13-
TMC ligand, such as mononuclear nonheme high-spin [(13-
III
R
2+
TMC)Fe (OOCO CHCH
3
Ph)]
Ph)]
(5)
(6)
and
complexes
[(13-
(see
2
3,24
complexes, a KIE value of 1.0 was determined in the oxidation
of cyclohexene and cyclohexene-d10 by iron(III)-acylperoxo
complexes, 1 – 4 (SI, Figure S9); the KIE value of 1.0 supports that
the oxidation of cyclohexene by the nonheme iron(III)-acylperoxo
complexes occurs via the C=C epoxidation pathway (Scheme 3C,
pathway a). Thus, based on the results of the product analysis and
KIE studies, we conclude that the oxidation of cyclohexene by
nonheme iron(III)-acylperoxo complexes occurs via the C=C
epoxidation pathway predominantly (Scheme 3C, pathway a),
which is different from the preference of the allylic C–H bond
activation of cyclohexene by nonheme metal-oxo complexes
III
S
2+
TMC)Fe (OOCO CHCH
3
Experimental Section for reaction procedures; also see SI, Figures
S2 and S10 for EPR and UV-vis spectra of 5 and 6). Interestingly,
when the chiral iron(III)-acylperoxo complexes were reacted with
chalcone, chalcone oxide was formed as a major product with a
good enantioselectivity (Scheme 4B) (see Experimental Section for
product analysis; see also SI, Figure S11 for HPLC spectra). When
the epoxidation of chalcone by the peroxyacid was carried out in
the absence of the iron catalyst, the formation of chalcone oxide
was negligible. This control reaction demonstrated that the
chalcone oxide was the epoxidation product of chalcone by the
chiral iron(III)-acylperoxo complexes, not by the peroxycarboxylic
acids remained in solutions. Moreover, the present results
demonstrate unambiguously that the intermediate responsible for
the epoxidation of olefins by the iron(III)-acylperoxo species
should contain a chiral center (i.e., 5 and 6) (Scheme 4A, pathway a)
and that the iron(IV or V)-oxo complexes formed via O−O bond
cleavage, which do not possess a chiral center, are not the active
oxidant for the olefin epoxidation (Scheme 4A, pathways b and c).
2
3,24
(Scheme 3C, pathway d).
We also performed the olefin epoxidation with chiral iron(III)-
acylperoxo complexes, with an assumption that if the iron(III)-
acylperoxo species is the epoxidizing intermediate, we would
observe the formation of epoxide with an enantiomeric excess (ee)
(Scheme 4A, pathway a). If an iron(IV or V)-oxo species is formed
via O−O bond cleavage of the iron-acylperoxo complex and the
resulting iron-oxo species is involved in the olefin epoxidation, only
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Further, when the catalytic olefin epoxidation was performed using
the optically active peroxycarboxylic acids in the presence of
II
2+
[Fe (13-TMC)] , epoxides were produced predominantly with
virtually the same ee values as obtained in the stoichiometric
reactions (SI, Figure S11). We therefore conclude that the catalytic
epoxidation of olefins by the nonheme iron complex and
peroxycarboxylic acids is mediated by the iron(III)-acylperoxo
species (Scheme 4A, pathway a), not by the iron-oxo species
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
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1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(Scheme 4A, pathways b and c).
As a conclusion, we have reported that the nonheme iron(III)-
acylperoxo complexes epoxidize olefins efficiently with
electrophilic character. Epoxides are formed as the major products
with high stereo-, chemo-, and enantioselectivities; (a) the
epoxidation of cis- and trans-stilbenes by the iron(III)-acylperoxo
complexes affords the corresponding cis- and trans-stilbene oxides,
respectively, (b) the nonheme iron(III)-acylperoxo complexes
prefer the C=C epoxidation to the C−H bond activation in the
oxidation of cyclohexene, and (c) the olefin epoxidation by chiral
iron(III)-acylperoxo complexes yields epoxide products with a
good enantioselectivity. The latter result strongly supports that the
nonheme iron(III)-acylperoxo complexes epoxidize olefins prior to
the conversion into the high-valent iron-oxo species (vide infra).
Alkane Hydroxylation by Iron(III)-Acylperoxo Complexes (1 − 4).
The iron(III)-acylperoxo complexes, 1 – 4, were investigated in the
o
C−H bond activation of alkanes at −40 C. Addition of cumene to
the solutions of 1 – 4 in a solvent mixture of CF
3
CH OH and
2
o
acetone (v/v = 3:1) at −40 C resulted in the disappearance of the
intermediates with a first-order decay profile (see Figure 4a for the
reaction of 1; SI, Figure S12 for the reactions of 2 – 4). The first
order rate constants, determined by first-order fitting of the kinetic
data for the decay of the iron(III)-acylperoxo species at 660 nm,
increased proportionally to the cumene concentration (Figure 4b;
SI, Figure S13), affording second-order rate constants for the
reactions of 1 – 4 (see Table S7). A second-order rate constant of
–1
–1 –1
6
.0 × 10 M s with a KIE value of 8.0(6) was obtained for the
oxidation of cumene by 1 (Figure 4b). In the same reaction using 2
− 4, similar second-order rate constants with the KIE value of ~8
were obtained (Figure S13). Second-order rate constants were also
obtained for oxidation of other substrates by 1 (SI, Table S8 and
Figure S14), showing a linear correlation between the reaction
rates and the C−H bond dissociation energies (BDE) of the
Figure 4. (a) UV-vis spectral changes observed in the reaction of 1
(1.0 mM) and cumene (25 mM) in CF CH OH/acetone (3:1) at
−40 C. Inset shows the time course monitored at 660 nm. (b) Plots
of pseudo-first-order rate constants, kobs, against concentrations of
cumene-h12 (black circles) and cumene-d12 (red circles) to determine
3
2
o
2
6
second-order rate constants (k
2
) in CF
3
CH OH/acetone (3:1) at
2
substrates (Figure 4c). The observations of the large KIE value
and the linear correlation between the reaction rates and the BDEs
of substrates lead us to conclude that the C−H bond activation of
substrates by the iron(III)–acylperoxo species is the rate-
determining step.
o
−
40 C. (c) Plot of log k
2
′ versus C−H BDEs of substrates. The k '
2
values are obtained by dividing second-order rate constants (k ) by
2
the number of equivalent target C−H bonds in the substrates.
Product analysis of the reaction solutions revealed the
formation of alcohols as the major product in the oxidation of
alkanes by 1 – 4 (SI, Tables S7 and S9). For example, the oxidation
of cumene by 1 under an inert atmosphere produced 2-
phenylpropan-2-ol (39(4)%), α-methylstyrene (13(3)%), and
acetophenone (3.0(6)%). Importantly, when the cumene oxidation
formation of Fe(III) species (Experimental Section and SI, Figure
S16).
The regio- and seteroselectivities in the alkane hydroxylation
reactions by iron(III)-acylperoxo complexes were investigated
using substrate probes, such as adamantane and cis-1,2-
dimethylcyclohexane (DMCH). In the hydroxylation of
adamantane by 1, a high preference for the tertiary C−H bonds
1
8
by 1 was carried out under O
2
atmosphere, the oxygen atom in the
16
2
-phenylpropan-2-ol product contained O derived from 1, not
O derived from O (Scheme 5A; SI, Figure S15). Analysis of the
o
–1 26
1
8
18
(BDE of 3 C−H = 96.2 kcal mol ) over the secondary C−H
2
o
–1 26
bonds (BDE of 2 C−H = 100.2 kcal mol ) was observed, giving a
normalized 3 /2 ratio of ~75 (Scheme 5B). This result indicates
that the alkane hydroxylation by 1 is highly regioselective, as
decayed product of 1 in the oxidation of cumene with electrospray
ionization mass spectrometer (ESI-MS) and EPR showed the
o
o
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18
Scheme 5.
O
2
Experiment and Regio- and Stereoselectivities in
Scheme 6. Proposed Mechanisms and Reactions for O-Labeled
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
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4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
18
Hydroxylation Reactions by an Iron(III)-Acylperoxo Complex.
Water (H O) Experiments.
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
observed in other catalytic oxidation reactions by metalloporphyrin
experiments were performed in the styrene epoxidation and
cumene hydroxylation by 1, to understand the nature of the
reactive species responsible for the oxygenation reactions by the
nonheme iron(III)-acylperoxo complexes (e.g., iron(III)-
2
7
and nonheme iron complexes. More importantly, hydroxylation
of DMCH by 1 produced cis-1,2-dimethylcyclohexanol as the
major product with a small amount of an isomerized alcohol
product, trans-1,2-dimethylcyclohexanol (Scheme 5C). The latter
result indicates that the hydroxylation reaction by 1 is highly
stereoselective, as reported in the catalytic hydroxylation reactions
18
acylperoxo versus high-valent iron-oxo species). In the O-labeled
18
18
water experiments, no O-incorporation from H O into the
2
epoxide and alcohol products was observed under any
circumstances (Scheme 6B; Experimental Section and SI, Figures
S15 and S17), demonstrating that the active oxidant(s) responsible
for the olefin epoxidation and alkane hydroxylation reactions by the
28
by iron porphyrin and nonheme iron complexes.
In summary, we have shown that the nonheme iron(III)-
acylperoxo complexes are highly reactive species that can
hydroxylate alkane C−H bonds as strong as those in cyclohexane at
iron(III)-acylperoxo complex does not exchange its oxygen atom
o
18
−40 C; alcohols are yielded as the major products with high regio-
with H
2
O. Thus, as we have proposed in the olefin epoxidation by
and stereoselectivities and the source of the oxygen atom in the
alcohol product is the iron(III)-acylperoxo species, not molecular
oxygen. We have also shown that the alkane hydroxylation by the
iron(III)–acylperoxo species occurs via the rate-determining C−H
bond activation step, with a large KIE value and a good correlation
between the reaction rates and the BDEs of alkanes.
chiral iron(III)-acylperoxo complexes (vide supra), the present
result supports that the iron(III)-acylperoxo species, not the iron-
oxo species formed via the O−O bond cleavage, is the active
oxidant that effects the oxygenation reactions (Scheme 6A, k
1
>>
Finally, it is of interest to note that nonheme high-spin
iron(III)-iodosylarenes bearing the same supporting ligand, [(13-
30,31
k
O−O).
III
3+
TMC)Fe -OIAr] , exchange their atom with labeled water
Isotopically Labeled Water Experiments. Since it is extremely
difficult to identify the nature of intermediates involved in the
catalytic oxygenation of organic substrates by enzymes and metal
1
8
immediately upon addition of H O and oxygenate organic
2
18
18
substrates with full O-incorporation from H O into products
2
13
18
(Scheme 6C). Thus, by comparing the dramatically different
results of the O-labeled water experiments obtained in the
catalysts, isotopically labeled water (H O) experiments have been
2
18
frequently used as indirect evidence for the intermediacy of high-
valent metal-oxo species in the catalytic oxygenation reactions (e.g.,
high-valent metal-oxo species versus metal-OOR adducts
oxygenation reactions by the iron(III)-acylperoxo and iron(III)-
iodosylarene complexes (Schemes 6B and 6C), we propose that the
active oxidants are iron(III)-acylperoxo and iron(III)-iodosylarene
complexes, not their high-valent iron-oxo counterparts.
1
8
18
depending on the O-incorporation from H O into oxygenated
2
29
18
products) (see Scheme 6). Therefore, O-labeled water
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5
5
6
CONCLUSIONS
7B) and the iron(V)-oxo species, not the low-spin iron(III)-
acylperoxo complex, is the active oxidant for stereoselective alkane
The nature of reactive intermediates in catalytic oxygenation
reactions by metalloenzymes and metal complexes has been the
subject of much debate over the several decades. One way to
identify such highly reactive intermediates is to synthesize
biomimetic compounds of the intermediates and then use them
directly in reactivity studies. Since one of the often-discussed metal-
oxygen intermediates in oxygenation reactions is metal-acylperoxo
species, we synthesized mononuclear nonheme high-spin iron(III)-
acylperoxo complexes bearing an N-methylated cyclam ligand and
characterized them spectroscopically. We then investigated their
reactivities in oxygenation reactions, such as olefin epoxidation and
alkane hydroxylation. The nonheme high-spin iron(III)-acylperoxo
complexes showed high reactivities in the olefin epoxidation and
alkane hydroxylation reactions, with high stereo-, chemo-, and
enantioselectivities in olefin epoxidation and with high regio- and
stereoselectivities in alkane hydroxylation. Moreover, we found
that the reactivities of the iron(III)-acylperoxo complexes are very
different from those of synthetic nonheme iron(IV)-oxo complexes
in both olefin epoxidation and alkane hydroxylation reactions, such
as the oxidation of cyclohexene in olefin epoxidation (Scheme 3C)
1
6a
hydroxylation reactions. Then, a question arises - what causes the
different reactivities and mechanisms shown by the high- and low-
spin iron(III)-acylperoxo complexes in Scheme 7? We hypothesize
that the spin states of iron(III)-acylperoxo complexes (e.g., high-
and low-spin iron(III)-acylperoxo complexes) and/or the
structures of iron(III)-acylperoxo complexes (e.g., the availability
of cis-sites for the binding of acylperoxo ligand) are key factors that
control reactivities of the nonheme iron(III)-acylperoxo complexes.
Thus, future studies will be focused on elucidating the intriguing
reactivity differences between high- and low-spin Fe(III)-
acylperoxo complexes. This type of reactivity difference has been
demonstrated recently in the reactions of high- and low-spin
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
10,11
iron(III)-hydroperoxo complexes.
EXPERIMENTAL SECTION
II
Materials. [Fe (13-TMC)(CF
3
18
SO ) ] was prepared according to
3
2
19
18
18
the literature procedure.
H
2
O (97 % O-enriched) and
O
2
18
(98% O-enriched) were purchased from ICON Services Inc.
(Summit, NJ, USA). m-Chloroperoxybenzoic acid (m-CPBA, 77%)
and peracetic acid (PAA, 32% wt) were purchased from Aldrich
Chemical Co. Other peroxycarboxylic acids, such as
phenylperoxyacetic acid (PPAA), peroxybenzoic acid (PBA), (R)-
2-phenylperoxypropionic acid, and (S)-2-phenylperoxypropionic
18
and the O experiment in alkane hydroxylation (Scheme 5A). In
2
addition, based on the results of mechanistic studies, such as the
olefin epoxidation by chiral iron(III)-acylperoxo complexes
18
(
Scheme 4) and the O-labeled water experiments in both olefin
25,32
epoxidation and alkane hydroxylation reactions (Scheme 6), it
became clear that the iron(III)-acylperoxo complexes are strong
oxidants capable of oxygenating hydrocarbons prior to their
conversion into high-valent iron-oxo species via O−O bond
cleavage. In addition, experimental evidence supporting
equilibrium between an iron(III)-acylperoxo complex and its
corresponding iron(V)-oxo complex and a carboxylic acid (Scheme
7A) was not observed in the present study. Thus, these results are
different from the recently reported important study by Mu ̈n ck,
Que, Company, Costas, and their co-workers, in which a low-spin
iron(III)-acylperoxo complex, Fe (OOAc), and a high-valent
iron(V)-oxo complex, Fe (O)(OAc), are in equilibrium (Scheme
acid, were prepared as described in the literature.
All the
peroxyacids except peroxyacetic acid were purified by washing with
phosphate buffer (pH 7.2) and recrystallized from hexane/ether to
remove free carboxylic acid. The purity of the peroxycarboxylic
acids was determined by iodometric titration. Peroxycarboxylic
acid, once isolated, is stable over long periods of time when stored
o
at 0 C in a plastic container. All other chemicals were obtained
from Aldrich Chemical Co. and used without further purification
unless otherwise indicated. Solvents were dried according to the
3
3
reported procedures and distilled under Ar prior to use. All
reactions were performed under an Ar atmosphere or standard
Schlenk techniques unless otherwise noted.
III
V
Instrumentation. UV-vis spectra were recorded on a Hewlett
Packard Agilent 8453 UV-visible spectrophotometer equipped
with a circulating water bath or an UNISOKU cryostat system
(USP-203, Japan). Electrospray ionization mass spectra (ESI-MS)
Scheme 7. Reactivity Differences between High- and Low-Spin
Iron(III)-Acylperoxo Complexes.
TM
were collected on a Thermo Finnigan (San Jose, CA, USA) LCQ
Advantage MAX quadrupole ion trap instrument, by infusing
samples directly into the source at 20 μL/min using a syringe pump.
The spray voltage was set at 4.7 kV and the capillary temperature at
o
80
C. Electron paramagnetic resonance (EPR) spectra were
recorded at 5 K using X-band Bruker EMX-plus spectrometer
equipped with a dual mode cavity (ER 4116DM). The low
temperatures were achieved and controlled with Oxford
Instruments ESR900 liquid He quartz cryostat with Oxford
Instruments ITC503 temperature and gas flow controller. The
experimental parameters for EPR measurements were as follows:
microwave frequency = 9.646 GHz, microwave power = 1.0 mW,
4
modulation amplitude = 10 G, gain = 1 × 10 , modulation
frequency = 100 kHz, time constant = 40.96 ms and conversion
time = 85.00 ms. Mössbauer spectra were recorded at 5 K on a low-
field Mössbauer spectrometer equipped with a Janis CCR 5 K
cryostat or at 4.2 K on a strong-field Mössbauer spectrometer
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6
equipped with an Oxford Instruments Spectromag 4000 cryostat
was improved based on preliminary EXAFS fit parameters to
generate more accurate theoretical EXAFS signals. Data fitting was
containing an 8 T split-pair superconducting magnet. Both
spectrometers were operated in a constant acceleration mode in
transmission geometry. The isomer shifts were referenced against
that of a metallic iron foil at room temperature. Analysis of the data
was performed with the program WMOSS (WMOSS4 Mössbauer
Spectral Analysis Software, www.wmosss.org, 2009-2015). Product
analysis was performed with an Agilent Technologies 6890N gas
chromatograph (GC) (HP-5 column, 30 m × 0.32 mm × 0.25 μm
film thickness) with a flame ionization detector and Thermo
Finnigan (Austin, Texas, USA) FOCUS DSQ (dual stage
quadrupole) mass spectrometer interfaced with Finnigan FOCUS
gas chromatograph (GC-MS). Free carboxylic acid was quantified
by GC equipped with Agilent J&W HP-FFAP column (25 m length
3
6
performed in EXAFSPAK. The structural parameters varied
during the fitting process were the bond distance (R) and the bond
2
variance σ , which is related to the Debye-Waller factor resulting
from thermal motion, and static disorder of the absorbing and
scattering atoms. The non-structural parameter ΔE
0
0
(E = the
energy at which k is 0) was also allowed to vary but was restricted to
a common value for every component in a given fit. Coordination
numbers were systematically varied in the course of the fit but were
fixed within a given fit. The coordination number for the short
Fe−O distance and the longer Fe−O distances were set to 0.5. Fits
accommodating a 40/60 or 60/40 mixture of 1 and [(13-
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
IV
2+
TMC)Fe (O)] gave poorer fits. However, the accuracy of
EXAFS data is not high enough to differentiate between a 50/50,
40/60 and 60/40 mixture of the two forms.
×
0.32 mm i.d.; 0.50 μm film thickness). Chromatographic analysis
of enantiomers was performed on High Performance Liquid
Chromatography (HPLC, DIOMEX Pump Series P580) equipped
with a variable wavelength UV-200 detector and Diacel OD-H
column (4.6 mm × 25 cm).
Generation and Characterization of 1 − 6. The blue intermediates,
III
2+
[
(13-TMC)Fe (OOC(O)CH
2
Ph)]
(1),
[(13-
[(13-
[(13-
[(13-
[(13-
III
2+
TMC)Fe (OOC(O)Ph)]
TMC)Fe (OOC(O)C
TMC)Fe (OOC(O)CH
TMC)Fe (OOCOCHCH
TMC)Fe (OOCOCHCH
[Fe (13-TMC)(CF
(2),
(3),
(4),
(5),
III
2+
X-ray Absorption Spectroscopy. The Fe K-edge X-ray absorption
6
H Cl)]
4
II
III
2+
spectra of [Fe (13-TMC)(CF
3
SO
3 2
) ], 1, and [(13-
3
)]
3
IV
2+
III
R
2+
TMC)Fe (O)] were measured at the Stanford Synchrotron
Radiation Lightsource (SSRL) on the unfocussed 20-pole 2 T
wiggler side-station beam line 7-3 under standard ring conditions
of 3 GeV and ~500 mA. A Si(220) double crystal monochromator
was used for energy selection. A Rh-coated harmonic rejection
mirror was used on beam line 7-3 to reject components of higher
harmonics. All complexes were measured as solutions, which were
transferred into 2 mm delrin XAS cells with 70 ꢀm Kapton tape
windows under synthesis conditions and were immediately frozen
Ph)]
and
III
S
2+
3
Ph)] (6), were generated by reacting
SO ) ] (1.0 mM) with 4 equiv of PPAA, PBA,
II
3
3
2
m-CPBA, PAA, (R)-2-phenylperoxypropionic acid, and (S)-2-
phenylperoxypropionic acid, respectively, in CF CH OH/acetone
3
2
(3:1) at –40 °C. The full formation of 1 – 6 was confirmed by
monitoring UV-vis spectral changes at 660 nm.
Kinetic Measurements. All reactions were run in a 1.0 cm UV
quartz cuvette and followed by monitoring UV-vis spectral changes
after preparation and stored under liquid N . During data collection,
2
of the reaction solutions in CF
3
CH OH/acetone (3:1). Rate
2
samples were maintained at a constant temperature of ~10 − 15 K
constants were determined under pseudo-first-order reaction
conditions (e.g., [substrate]/[1] > 10) by fitting the absorbance
changes at 660 nm for the disappearances of 1 − 4. In olefin
epoxidation, the reactions of 1 − 4 with stilbenes, styrene
using an Oxford Instruments CF 1208 liquid helium cryostat. Data
-
1
were measured to k = 14 Å (fluorescence mode) using a Canberra
Ge 30-element array detector. Internal energy calibration was
accomplished by simultaneous measurement of the absorption of
an Fe-foil placed between two ionization chambers situated after
the sample. The first inflection point of the foil spectrum was fixed
at 7111.2 eV. The samples were monitored for photoreduction and
a small shift in the rising edge energy position was observed over
successive scans, indicating x-ray dose related photoreduction of
the Fe center. To alleviate this problem, a single scan was obtained
from each fresh sample position. For the measurement of [(13-
o
derivatives, and cyclohexene were investigated at –60 C. The KIE
values for the oxidation reactions of styrene and cyclohexene by 1 −
4
were obtained by using the k
2
values of styrene-h
8
/styrene-d and
8
cyclohexene-h10/cyclohexene-d10, respectively. The C−H bond
activation reactions by 1 were performed at –40 °C with substrates,
–1
such as triphenylmethane (81.0 kcal mol ), cumene (84.8 kcal
–1
–1
–
mol ), ethylbenzene (87.0 kcal mol ), cyclooctane (95.7 kcal mol
)
1
–1 26
, and cyclohexane (99.5 kcal mol ). The KIE values for the
IV
2+
TMC)Fe (O)] , the monochromator was further detuned by
0%. EXAFS data presented here are 12-scan average for 1. XANES
reaction of 1 − 4 with cumene were determined by comparing k
2
5
values obtained in the C−H and C−D bond activation reactions of
cumene-h12 and cumene-d12, respectively. The kinetic experiments
were run at least in triplicate, and the data reported represent the
average of these reactions.
II
data presented for [Fe (13-TMC)(CF
3
SO ) ], 1, and [(13-
3
2
IV
2+
TMC)Fe (O)] were 7-scan, 12-scan and 8-scan average,
respectively. Data were processed by fitting a second-order
polynomial to the pre-edge region and subtracting this from the
entire spectrum as background. A four-region spline of orders 2, 3,
3 and 3 was used to model the smoothly decaying post-edge region.
The data were normalized by subtracting the cubic spline and
assigning the edge jump to 1.0 at 7150 eV using the Pyspline
Product Analysis. Products formed in the reactions of 1 with
styrene derivatives, cyclohexene, triphenylmethane, cumene,
ethylbenzene, cyclooctane, cyclohexane, adamantane, and cis-1,2-
dimethylcyclohexane were identified by GC and GC-MS by
comparison of the mass peaks and retention time of the products
with respect to authentic samples, and the product yields were
determined by comparing the responsive peak areas of sample
products against standard curves prepared with known authentic
compounds using internal standard decane or dodecane. For cis-
and trans-stilbenes, product yields were determined by HPLC
34
program. Data were then renormalized in Kaleidagraph for
comparison and quantification purposes.
Theoretical EXAFS signals χ(k) were calculated by using FEFF
35
(
Macintosh version 7.0). Starting structural models were
obtained from DFT optimized structures 1. The input structure
9
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Journal of the American Chemical Society
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equipped with SunFire C18 5μm column (4.6 mm × 25 cm). The
iron products obtained in the reaction of 1 with substrates were
analyzed with X-band EPR and ESI-MS spectroscopies.
cumene, and the percentage of O in 2-phenylpropan-2-ol was
1
8
determined as described above for the O experiment.
2
For the analysis of the O−O bond cleavage product(s) of PPAA,
ASSOCIATEDꢀCONTENTꢀ ꢀ
1
(1.0 mM) was freshly prepared in a solvent mixture of
CF CH OH/acetone (3:1) at –60 °C under an Ar atmosphere,
followed by adding styrene (20 mM) to the reaction solution. The
reaction mixture was stirred for 10 min at −60 °C, and then PPh (4
Supporting Information. Tables S1 – S9 and Figures S1 – S17. This
material is available free of charge via the Internet at
http://pubs.acs.org.
3
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
3
mM) was added to quench the reaction. Nitrobenzene was added
as an internal standard, and the resulting solution was analyzed
directly by GC (Agilent J&W HP-FFAP column) and GC-MS.
Product yields were determined by comparing the responsive peak
areas of sample products against standard curves prepared with
known authentic compounds.
AUTHORꢀINFORMATIONꢀ
CorrespondingꢀAuthorsꢀ
wwnam@ewha.ac.kr
ritis@slac.stanford.edu
jean-marc.latour@cea.fr
Stoichiometric and Catalytic Asymmetric Epoxidation Reactions.
AuthorꢀContributionsꢀ
2
Chalcone (2.0 × 10 mM) was added to a solution containing the
All authors have contributed to the writing of the manuscript and
approved its final version.
chiral iron(III)-acylperoxo complexes, 5 or 6, which was freshly
prepared by adding 4 equiv of (R)-2-phenylperoxypropionic acid
(
8.0 mM) or (S)-2-phenylperoxypropionic acid (8.0 mM) to a
Notesꢀ ꢀ
II
solution of [Fe (13-TMC)(CF
3
SO
3
2
) ]
(2.0 mM) in
The authors declare no competing financial interest.
CF CH OH/acetone (3:1) at –60 °C. The resulting solution was
3
2
stirred for 15 min, and then saturated sodium thiosulfate solution
was added to quench the reaction. The organic layer was separated
and purified through flash column chromatography on silica gel,
and the epoxide product was identified by comparison to the
HPLC retention time of racemic epoxide. The enantiomeric excess
values were determined by HPLC equipped with Diacel OD-H
column and the absolute configuration of the products was
determined by comparison with literature reports.
ACKNOWLEDGMENTꢀ ꢀ
The authors acknowledge the NRF of Korea through CRI (NRF-
012R1A3A2048842 to W.N.) and GRL (NRF-2010-00353 to W.N.).
2
The SSRL SMB Resource is supported primarily by the NIH National
Institute of General Medical Sciences (NIGMS) through a Biomedical
Technology Research Resource P41 grant (P41GM103393) and
contract funds, and by the DOE Office of Biological and
Environmental Research. J.M.L. acknowledges the support, in part, of
Labex ARCANE (ANR-11-LABX-0003-01).
For
catalytic
epoxidation
acid (40
reactions,
mM) or
(R)-2-
(S)-2-
phenylperoxypropionic
phenylperoxypropionic acid (40 mM) was added to a solution
REFERENCESꢀ
(1)
II
containing [Fe (13-TMC)(CF
3
SO
3
)
2
] (2.0 mM) and chalcone
(a) Nam, W. Acc. Chem. Res. 2007, 40, 465, and review articles
2
(
2.0 × 10 mM) in CF
3
CH
2
OH/acetone (3:1) at –60 °C. The
in the special issue. (b) Holm, R. H.; Solomon, E. I. Chem. Rev. 2014, 114,
3367, and review articles in the special issue. (c) Que, L., Jr.; Tolman, W. B.
Nature 2008, 455, 333. (d) Ray, K.; Pfaff, F. F.; Wang, B.; Nam, W. J. Am.
Chem. Soc. 2014, 136, 13942. (e) Chen, Z.; Yin, G. Chem. Soc. Rev. 2015,
4, 1083. (f) Nam, W. Acc. Chem. Res. 2015, 48, 2415.
2) (a) Ortiz de Montellano, P. R. Cytochrome P450: Structure,
Mechanism, and Biochemistry, 3rd ed.; Springer: Berlin, 2005. (b) Nam, W.
Acc. Chem. Res. 2007, 40, 522. (c) Shaik, S.; Hirao, H.; Kumar, D. Acc.
Chem. Res. 2007, 40, 532. (d) Ortiz de Montellano, P. R. Chem. Rev. 2010,
110, 932. (e) Costas, M. Coord. Chem. Rev. 2011, 255, 2912. (f) Krest, C.
M.; Onderko, E. L.; Yosca, T. H.; Calixto, J. C.; Karp, R. F.; Livada, J.; Rittle,
J.; Green, M. T. J. Biol. Chem. 2013, 288, 17074.
resulting solution was stirred for 15 min and then analyzed as
described above. There were no oxygenated products when control
experiments were carried out in the absence of the iron(II)
complex under the identical reaction conditions.
4
(
18
18
18
Isotopically Labeled
O
2
and H
2
O Experiments. For
O
2
experiment, both the catalyst and substrates were degassed by four
freeze-vacuum-thaw cycles prior to the reaction being performed
1
8
under an
O
2
atmosphere. Cumene (50 mM) was added to a
CH OH/acetone
atmosphere. The resulting solution was
freshly prepared solution of 1 (1.0 mM) in CF
(3:1) at –40 °C under O
stirred for 10 min at −40 C and then directly analyzed by GC-MS.
The percentage of O in 2-phenylpropan-2-ol was determined by
comparison of the relative abundances at m/z = 123 for 2-
3
2
18
2
(
3)
(a) Abu-Omar, M. M.; Loaiza, A.; Hontzeas, N. Chem. Rev.
005, 105, 2227. (b) Krebs, C.; Fujimori, D. G.; Walsh, C. T.; Bollinger, J.
o
2
18
M., Jr. Acc. Chem. Res. 2007, 40, 484. (c) Hohenberger, J.; Ray, K.; Meyer,
K. Nat. Commun. 2012, 3, 720. (d) Solomon, E. I.; Light, K. M.; Liu, L. V.;
Srnec, M.; Wong, S. D. Acc. Chem. Res. 2013, 46, 2725. (e) Nam, W.; Lee,
Y.-M.; Fukuzumi, S. Acc. Chem. Res. 2014, 47, 1146. (f) Cook, S. A.;
Borovik, A. S. Acc. Chem. Res. 2015, 48, 2407.
Rittle, J.; Green, M. T. Science, 2010, 330, 933.
(a) Gunay, A.; Theopold, K. H. Chem. Rev. 2010, 110, 1060.
(b) Borovik, A. S. Chem. Soc. Rev. 2011, 40, 1870. (c) De Visser, S. P.;
Rohde, J.-U.; Lee, Y.-M.; Cho, J.; Nam, W. Coord. Chem. Rev. 2013, 257,
381. (d) Fukuzumi, S. Coord. Chem. Rev. 2013, 257, 1564. (e) Cho, K.-B.;
Hajime, H.; Shaik, S.; Nam, W. Chem. Soc. Rev. 2016, DOI:
18
phenylpropan-2-ol− O and at m/z = 121 for 2-phenylpropan-2-
16
ol− O.
For H
styrene (50 mM) were added to a freshly prepared solution of 1
1.0 mM) in CF CH OH/acetone (3:1) under an Ar atmosphere.
The resulting solution was stirred for 10 min at −60 C and then
18
18
18
2
O experiments, H O (20 ꢀL, 97% O-enriched) and
2
(
(
4)
5)
(
3
2
o
18
directly analyzed by GC-MS. The percentage of O in styrene
oxide was determined by comparison of the relative abundances at
18
1
0.1039/c5cs00566c. (f) Puri, M.; Que, L., Jr. Acc. Chem. Res. 2015, 48,
m/z = 121 for styrene oxide− O and at m/z = 119 for styrene
16
18
2443.
oxide− O. Similarly, the H O experiment was performed with
2
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1
1
1
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1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(6)
(a) Price, J. C.; Barr, E. W.; Tirupati, B.; Bollinger, J. M., Jr.;
12273. (d) Ghosh, M.; Singh, K. K.; Panda, C.; Weitz, A.; Hendrich, M. P.;
Collins, T. J.; Dhar, B. B.; Gupta, S. S. J. Am. Chem. Soc. 2014, 136, 9524.
(e) Van Heuvelen, K. M.; Fiedler, A. T.; Shan, X.; De Hont, R. F.; Meier, K.
K.; Bominaar, E. L.; Münck, E.; Que, L., Jr. Proc. Natl. Acad. Sci. USA 2012,
109, 11933. (f) Lyakin, O. Y.; Bryliakov, K. P.; Britovsek, G. J. P.; Talsi, E. P.
J. Am. Chem. Soc. 2009, 131, 10798. (g) de Oliveira, F. T.; Chanda, A.;
Banerjee, D.; Shan, X.; Mondal, S.; Que, L., Jr.; Bominaar, E. L.; Münck, E.;
Collins, T. J. Science 2007, 315, 835.
(17) McDonald, A. R.; Que, L., Jr. Coord. Chem. Rev. 2013, 257,
414.
(18) Gütlich, P.; Bill, E.; Trautwein, A. X. Mössbauer Spectroscopy
and Transition Metal Chemistry: Fundamentals and Applications, Chapter
4, pp 73 – 135, Springer-Verlag: Berlin Heidelberg, 2011.
Krebs, C. Biochemistry 2003, 42, 7497. (b) Rohde, J.-U.; In, J.-H.; Lim, M.
H.; Brennessel, W. W.; Bukowski, M. R.; Stubna, A.; Mu
Que, L., Jr. Science 2003, 299, 1037.
̈n ck, E.; Nam, W.;
(
7)
(a) Newcomb, M.; Hollenberg, P. F.; Coon, M. J. Arch.
Biochem. Biophys. 2003, 409, 72. (b) Newcomb, M.; Toy, P. H. Acc.
Chem. Res. 2000, 33, 449. (c) Vaz, A. D. N.; McGinnity, D. F.; Coon, M. J.
Proc. Natl. Acad. Sci. USA 1998, 95, 3555. (d) Volz, T. J.; Rock, D. A.;
Jones, J. P. J. Am. Chem. Soc. 2002, 124, 9724. (e) Cryle, M. J.; De Voss, J. J.
Angew. Chem. Int. Ed. 2006, 45, 8221.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
8)
(a) Shaik, S.; Hirao, H.; Kumar, D. Nat. Prod. Rep. 2007, 24,
5
2
33. (b) Song, W. J.; Ryu, Y. O.; Song, R.; Nam, W. J. Biol. Inorg. Chem.
005, 10, 294. (c) Nam, W.; Ryu, Y. O.; Song, W. J. J. Biol. Inorg. Chem.
2004, 9, 654. (d) Shaik, S.; de Visser, S. P.; Kumar, D. J. Biol. Inorg. Chem.
2004, 9, 661.
(19) Hong, S.; So, H.; Yoon, H.; Cho, K.-B.; Lee, Y.-M.; Fukuzumi,
S.; Nam, W. Dalton trans. 2013, 42, 7842.
(20) (a) Ostovic, D.; Bruice, T. C. Acc. Chem. Res. 1992, 25, 314. (b)
Traylor, T. G.; Xu, F. J. Am. Chem. Soc. 1988, 110, 1953.
(
9)
Curr. Opin. Chem. Biol. 2009, 13, 99.
10) Cho, J.; Jeon, S.; Wilson, S. A.; Liu, L. V.; Kang, E. A.; Braymer,
Solomon, E. I.; Wong, S. D.; Liu, L. V.; Decker, A.; Chow, M. S.
(
(21) (a) Annaraj, J.; Kim, S.; Seo, M. S.; Lee, Y.-M.; Kim, Y.; Kim, S.-
J.; Choi, Y. S.; Jang, H. G.; Nam, W. Inorg. Chim. Acta 2009, 362, 1031. (b)
Singh, K. K.; Tiwari, M. K.; Dhar, B. B.; Vanka, K.; Gupta, S. S. Inorg.
Chem. 2015, 54, 6112.
(22) (a) Groves, J. T.; Watanabe, Y. Inorg. Chem. 1986, 25, 4808.
(b) Higuchi, T.; Shimada, K.; Maruyama, N.; Hirobe, M. J. Am. Chem. Soc.
1993, 115, 7551. (c) Suzuki, N.; Higuchi, T.; Nagano, T. J. Am. Chem. Soc.
2002, 124, 9622. (d) Miyazaki, Y.; Satake, A.; Kobuke, Y. J. Mol. Catal. A:
Chem. 2008, 283, 129. (e) Song, Y. J.; Hyun, M. Y.; Lee, J. H.; Lee, H. G.;
Kim, J. H.; Jang, S. P.; Noh, J. Y.; Kim, Y.; Kim, S.-J.; Lee, S. J.; Kim, C.
Chem. Eur. J. 2012, 18, 6094. (f) Hyun, M. Y.; Jo, Y. D.; Lee, J. H.; Lee, H.
G.; Park, H. M.; Hwang, I. H.; Kim, K. B.; Lee, S. J.; Kim, C. Chem. Eur. J.
2013, 19, 1810.
(23) (a) Dhuri, S. N.; Cho, K.-B.; Lee, Y.-M.; Shin, S. Y.; Kim, J. H.;
Mandal, D.; Shaik, S.; Nam, W. J. Am. Chem. Soc. 2015, 137, 8623. (b)
Kwon, Y. H.; Mai, B. K.; Lee, Y.-M.; Dhuri, S. N.; Mandal, D.; Cho, K.-B.,
Kim, Y.; Shaik, S.; Nam, W. J. Phys. Chem. Lett. 2015, 6, 1472.
(24) Oloo, W. N.; Feng, Y.; Lyer, S.; Parmelee, S.; Xue, G.; Que, L.,
Jr. New J. Chem. 2013, 37, 3411.
J. J.; Lim, M. H.; Hedman, B.; Hodgson, K. O.; Valentine, J. S.; Solomon, E.
I.; Nam, W. Nature 2011, 478, 502.
(11) (a) Park, M. J.; Lee, J.; Suh, Y.; Kim, J.; Nam, W. J. Am. Chem.
Soc. 2006, 128, 2630. (b) Liu, L. V.; Hong, S.; Cho, J.; Nam, W.; Solomon,
E. I. J. Am. Chem. Soc. 2013, 135, 3286. (c) Kim, Y. M.; Cho, K.-B.; Cho,
J.; Wang, B.; Li, C.; Shaik, S.; Nam, W. J. Am. Chem. Soc. 2013, 135, 8838.
(
12) (a) Draksharapu, A.; Angelone, D.; Quesne, M. G.; Padamati, S.
K.; Gόmez, L.; Hage, R.; Costas, M.; Browne, W. R.; de Visser, S. P. Angew.
Chem. Int. Ed. 2015, 54, 4357. (b) Wang, C.; Kurahashi, T.; Fujii, H.
Angew. Chem. Int. Ed. 2012, 51, 7809. (c) Cong, Z.; Yanagisawa, S.;
Kurahashi, T.; Ogura, T.; Nakashima, S.; Fujii, H. J. Am. Chem. Soc. 2012,
34, 20617. (d) Lennartson, A.; McKenzie, C. J. Angew. Chem. Int. Ed.
012, 51, 6767. (e) Guo, M.; Dong, H.; Li, J.; Cheng, B.; Huang, Y.-q.;
1
2
Feng, Y.-q.; Lei, A. Nat. Commun. 2012, 3, 1190.
13) (a) Hong, S.; Wang, B.; Seo, M. S.; Lee, Y.-M.; Kim, M. J.; Kim,
(
H. R.; Ogura, T.; Carcia-Serres, R.; Clémancey, M.; Latour, J.-M.; Nam, W.
Angew. Chem. Int. Ed. 2014, 53, 6388. (b) Wang, B.; Lee, Y.-M.; Seo, M.
S.; Nam, W. Angew. Chem. Int. Ed. 2015, 54, 11740.
(
14) (a) Makhlynets, O. V.; Oloo, W. N.; Moroz, Y. S.; Belaya, I. G.;
(25) (a) Collins, J. F.; McKervey, M. A. J. Org. Chem. 1969, 34, 4172.
(b) Silbert, L. S.; Siegel, E.; Swern, D. J. Org. Chem. 1962, 27, 1336. (c)
Folli, U.; Iarossi, D.; Montanari, F.; Torre, G. J. Chem. Soc. C. 1968, 1317.
(d) Folli, U.; Iarossi, D.; Montanari F. J. Chem. Soc. C. 1968, 1372. (e)
Montanari, F.; Moretti, I.; Torre, G. Chem. Commun. 1969, 135.
(26) Luo Y-R. Comprehensive Handbook of Chemical Bond
Energies. Taylor & Francis: Boca Raton, FL, 2007.
Palluccio, T. D.; Filatov, A. S.; Müller, P.; Cranswick, M. A.; Que, L., Jr.;
Rybak-Akimova, E. V. Chem. Commun. 2014, 50, 645. (b) Oloo, W. N.;
Meier, K. K.; Wang, Y.; Shaik, S.; Münck, E.; Que, L., Jr. Nat. Commun.
2014, 5, 3046. (c) Nakazawa, J.; Terada, S.; Yamada, M.; Hikichi, S. J. Am.
Chem. Soc. 2013, 135, 6010. (d) Hikichi, S.; Hanaue, K.; Fujimura, T.;
Okuda, H.; Nakazawa, J.; Ohzu, Y.; Kobayashi, C.; Akita, M. Dalton Trans.
2
013, 42, 3346. (e) Zhang, X.; Furutachi, H.; Tojo, T.; Tsugawa, T.;
(27) (a) Groves, J. T.; Nemo, T. E. J. Am. Chem. Soc. 1983, 105,
6243. (b) Brown, R. B.; Hill, C. L. J. Org. Chem. 1988, 53, 5762. (c) Barton,
D. H. R.; Beck, A. H.; Taylor, D. K. Tetrahedron 1995, 51, 5245. (d) Chen,
K.; Que, L., Jr. J. Am. Chem. Soc. 2001, 123, 6327. (e) Mitra, M.; Lloret-
Fillol, J.; Haukka, M.; Costas, M.; Nordlander, E. Chem. Commun. 2014,
50, 1408. (f) Olivo, G.; Nardi, M.; Vìdal, D.; Barbieri, A.; Lapi, A.; Gómez,
L.; Lanzalunga, O.; Costas, M.; Stefano S. D. Inorg. Chem. 2015, 54, 10141.
(28) (a) Sono, M.; Roach, M. P.; Coulter, E. D.; Dawson, J. H. Chem.
Rev. 1996, 96, 2841. (b) Groves, J. T.; Nemo, T. E.; Myers, R. S. J. Am.
Chem. Soc. 1979, 101, 1032. (c) Kim, C.; Chen, K.; Kim, J.; Que, L., Jr. J.
Am. Chem. Soc. 1997, 119, 5964. (d) Nam, W.; Goh, Y. M.; Lee, Y. J.; Lim,
M. H.; Kim, C. Inorg. Chem. 1999, 38, 3238. (e) Gómez, L.; Garcia-Bosch,
I.; Company, A.; Benet-Buchholz, J.; Polo, A.; Sala, X.; Ribas, X.; Costas, M.
Angew. Chem. Int. Ed. 2009, 48, 5720. (f) Prat, I.; Company, A.; Postils, V.;
Ribas, X.; Que, L., Jr.; Luis, J. M.; Costas, M. Chem. Eur. J. 2013, 19, 6724.
(29) (a) Meunier, B.; Bernadou, J. Top. Catal. 2002, 21, 47. (b) Nam,
W.; Kim, I.; Lim, M. H.; Choi, H. J.; Lee, J. S.; Jang, H. G. Chem. Eur. J.
2002, 8, 2067. (c) Groves, J. T.; Lee, J.; Marla, S. S. J. Am. Chem. Soc. 1997,
119, 6269. (d) Lee, K. A.; Nam, W. J. Am. Chem. Soc. 1997, 119, 1916. (e)
Bernadou, J.; Fabiano, A.-S.; Robert, A.; Meunier, B. J. Am. Chem. Soc.
Fujinami, S.; Sakurai, T.; Suzuki, M. Chem. Lett. 2011, 40, 515. (f)
Hessenauer-Ilicheva, N.; Franke, A.; Meyer, D.; Woggon, W.-D.; van Eldik,
R. J. Am. Chem. Soc. 2007, 129, 12473. (g) Soper, J. D.; Kryatov, S. V.;
Rybak-Akimova, E. V.; Nocera, D. G. J. Am. Chem. Soc. 2007, 129, 5069.
(h) Machii, K.; Watanabe, Y.; Morishima, I. J. Am. Chem. Soc. 1995, 117,
691. (i) Kitajima, N.; Fujisawa, K.; Moro-oka, Y. Inorg. Chem. 1990, 29,
57. (j) Groves, J. T.; Watanabe, Y. Inorg. Chem. 1987, 26, 785. (k) Ghosh,
P.; Tyeklar, Z.; Karlin, K. D.; Jacobson, R. R.; Zubieta, J. J. Am. Chem. Soc.
987, 109, 6889. (l) Groves, J. T.; Watanabe, Y.; McMurry, T. J. J. Am.
6
3
1
Chem. Soc. 1983, 105, 4489. (m) Kikunaga, T.; Matsumoto, T.; Ohta, T.;
Nakai, H.; Naruta, Y.; Ahn, K.-H.; Watanabe, Y.; Ogo, S. Chem. Commun.
2
013, 49, 8356.
15) MacBeth, C. E.; Gupta, R.; Mitchell-Koch, K. R.; Young, V. G.;
(
Lushington, G. H.; Thompson, W. H.; Hendrich, M. P.; Borovik, A. S. J.
Am. Chem. Soc. 2004, 126, 2556.
(
16) (a) Serrano-Plana, J.; Oloo, W. N.; Acosta-Rueda, L.; Meier, K.
K.; Verdejo, B.; García-España, E.; Basallote, M. G.; Münck, E.; Que, L., Jr.;
Company, A.; Costas, M. J. Am. Chem. Soc. 2015, 137, 15833. (b) Lyakin,
O. Y.; Zima, A. M.; Samsonenko, D. G.; Bryliakov, K. P.; Talsi,
E. P. ACS Catal. 2015, 5, 2702. (c) Panda, C.; Debgupta, J.; Díaz, D.
D.; Singh, K. K.; Gupta, S. S.; Dhar, B. B. J. Am. Chem. Soc. 2014, 136,
1
994, 116, 9375. (f) Nam, W.; Valentine, J. S. J. Am. Chem. Soc. 1993, 115,
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1772. (g) Groves, J. T.; Haushalter, R. C.; Nakamura, M.; Nemo, T. E.;
Evans, B. J. J. Am. Chem. Soc. 1981, 103, 2884.
30) We cannot rule out a possibility that although the oxygenating
intermediate is an iron-oxo species, the oxygen atoms in the epoxide and
alcohol products may not derive from the labeled water if the rate of the
oxygen exchange between the iron-oxo species and labeled water is much
slower than that of the oxygenation reaction by the iron-oxo species
(
(Scheme 6A, kex ˂˂ k
2
). Nonetheless, we expect that an iron(V)-oxo
1
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0
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species exchanges its oxygen atom with H
2
O at a fast rate.
31) Unfortunately, no O-labeled water experiments were
1
8
(
performed in the alkane hydroxylation reactions by a nonheme iron(V)-
oxo species: See ref 16a.
(
32) (a) McDonald, R. N.; Steppel, R. N.; Dorsey, J. E. Org. Synth.
1970, 50, 15. (b) Ogata, Y.; Sawaki, Y. Tetrahedron 1967, 23, 3327.
(33) Armarego, W. L. F.; Chai, C. L. L. Purification of Laboratory
Chemicals, 6th ed.; Pergamon Press: Oxford, U.K., 2009.
(
34) Tenderholt, A.; Hedman, B.; Hodgson, K. O. PySpline: A
Modern, Cross-Platform Program for the Processing of Raw Averaged XAS
Edge and EXAFS Data. AIP Conference Proceedings 2007, 882, 105.
(
35) (a) Zabinsky, S. I.; Rehr, J. J.; Ankudinov, A.; Albers, R. C.; Eller,
M. J. Phys. Rev. B: Condens. Matter 1995, 52, 2995. (b) Rehr, J. J.; Mustre
de Leon, J.; Zabinsky, S. I.; Albers, R. C. J. Am. Chem. Soc. 1991, 113, 5135.
(
c) Mustre de Leon, J.; Rehr, J. J.; Zabinsky, S. I.; Albers, R. C. Phys. Rev. B:
Condens. Matter 1991, 44, 4146.
36) George, G. N. EXAFSPAK and EDG-FIT. Stanford
(
Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center,
Stanford, CA, 2000.
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