Intermolecular C-H bond activation of alkanes and arenes by NCN pincer iridium(III) acetate complexes containing bis(oxazolinyl)phenyl ligands

Article abstract of DOI:10.1021/om3002137

Carbon-hydrogen bond activation of arenes by the pincer Ir(III) acetate complex (phebox)Ir(OAc)₂(H₂O) (1; phebox = bis(oxazolinyl)phenyl) proceeded at 100 °C to give the corresponding aryl Ir(III) complexes (phebox)Ir(Ar)(OAc) in high yields. Reactions of the monosubstituted arenes anisole, toluene, chlorobenzene, acetophenone, and nitrobenzene resulted in the formation of meta- and para-substituted aryl complexes in high yields. Competitive experiments between two monosubstituted arenes exhibited relative reaction rates in the order C₆H ₅OMe > C₆H₅NO₂ > C ₆H₅COMe > C₆H₅Cl > C ₆H₅Me. The kinetic isotope effects of C-H bond activation of benzene and nitrobenzene were determined to be 2.9 ± 0.1 and 2.0 ± 0.4, respectively. The Ir complex 1 underwent catalytic borylation of arenes with bis(pinacolato)diboron (B₂(pin)₂) or pinacolborane (HB(pin)), giving the corresponding borylated products. The Ir complex 1 was also reactive toward alkane C-H bond activation, demonstrated by the reactions with n-heptane and n-octane at 160 °C that cleanly afforded the corresponding alkyl complexes (phebox)Ir(n-C_nH _2n+1)(OAc) (n = 7, 8, respectively).

Full text of DOI:10.1021/om3002137

Article
pubs.acs.org/Organometallics
Intermolecular C−H Bond Activation of Alkanes and Arenes by NCN
Pincer Iridium(III) Acetate Complexes Containing
Bis(oxazolinyl)phenyl Ligands
Jun-ichi Ito,* Tomoko Kaneda, and Hisao Nishiyama*
Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan
S
* Supporting Information
ABSTRACT: Carbon−hydrogen bond activation of arenes by the
pincer Ir(III) acetate complex (phebox)Ir(OAc)2(H2O) (1; phebox
= bis(oxazolinyl)phenyl) proceeded at 100 °C to give the
corresponding aryl Ir(III) complexes (phebox)Ir(Ar)(OAc) in
high yields. Reactions of the monosubstituted arenes anisole,
toluene, chlorobenzene, acetophenone, and nitrobenzene resulted
in the formation of meta- and para-substituted aryl complexes in
high yields. Competitive experiments between two monosubstituted
arenes exhibited relative reaction rates in the order C6H5OMe >
C6H5NO2 > C6H5COMe > C6H5Cl > C6H5Me. The kinetic isotope
effects of C−H bond activation of benzene and nitrobenzene were determined to be 2.9 0.1 and 2.0 0.4, respectively. The Ir
complex 1 underwent catalytic borylation of arenes with bis(pinacolato)diboron (B2(pin)2) or pinacolborane (HB(pin)), giving
the corresponding borylated products. The Ir complex 1 was also reactive toward alkane C−H bond activation, demonstrated by
the reactions with n-heptane and n-octane at 160 °C that cleanly afforded the corresponding alkyl complexes (phebox)Ir(n-
CnH2n+1)(OAc) (n = 7, 8, respectively).
complex was reactive toward C−H bond activation of arenes
across the Ru−OH bond.8
INTRODUCTION
■
Carbon−hydrogen bond activation of alkanes and arenes is
fundamental in organometallic chemistry for stoichiometric and
catalytic reactions used for transformation of simple and stable
molecules.1 Several reaction mechanisms have been proposed
that involve oxidative addition, σ-bond metathesis, electrophilic
activation, and 1,2-addition processes in accordance with the
properties of metal centers.2 For group 9 metals, oxidative
addition by electron-rich Ir(I) and Rh(I) complexes containing
electron-donating ligands, such as Cp* and Tp* ligands, is the
predominant process. In contrast, several reaction mechanisms
of C−H bond activation by Ir(III) complexes have been
proposed. Oxidative addition has been proposed for C−H
activation by the Ir alkyl complexes Cp*IrIII(OTf)Me.3
Similarly, C−H bond activation of benzene with an Ir(III)
bis(phenolate)pyridine methyl complex likely proceeded via an
oxidative addition process.4 On the other hand, electrophilic
activation promoted by the acetate ligand for intramolecular
cyclometalation by iridium and rhodium complexes
(Cp*MCl2)2 (M = Ir, Rh) has been proposed by experimental
and theoretical studies.5 In particular, theoretical studies
indicated that a six-membered cyclic transition state with a
Lewis basic carboxylate anion and a Lewis acidic metal center
could facilitate C−H bond activation via ambiphilic metal
ligand activation (AMLA).6 The Ir(III) methoxide complexes
underwent C−H bond activation of benzene, with assistance of
the alkoxide ligand proposed as an internal electrophilic
substitution process.7 As a related process, a Ru−hydroxide
Apart from the facial ligands Cp* and Tp*, pincer type
ligands are valuable tools for generating active metal complexes
in stoichiometric and catalytic C−H bond activation. PXP (X =
C,9 N10) pincer Ir complexes generally underwent oxidative
addition of arenes via an Ir(I) intermediate. The C−H bond
activation of arenes by NCN pincer Rh(III) acetate complexes
containing bis(oxazolinyl)phenyl (phebox) ligands to afford the
corresponding aryl complexes was reported recently.11 In this
reaction, the acetate ligand was essential for C−H bond
cleavage, suggesting that AMLA may proceed. As a polydentate
ligand framework, porphyrin complexes have been used for C−
H bond activation in both base-assisted and radical processes.12
This report describes the stoichiometric and catalytic C−H
bond activation of arenes by the phebox Ir(III) acetate complex
(phebox)Ir(OAc)2(H2O) (1).13,14 The Ir(III) acetate complex
exhibited unique reactivity toward alkane C−H bond activation,
giving the alkyl complex.
RESULTS AND DISCUSSION
■
Molecular Structure of 1. The preparation of (phebox)-
Ir(OAc)2(H2O) (1) by cyclometalation of a ligand precursor
with Ir chloride has been reported.14 First, the molecular
structure of 1 was confirmed by X-ray analysis (Figure 1). The
Received: March 16, 2012
Published: June 4, 2012
© 2012 American Chemical Society
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the Ir(III) center underwent C−H bond cleavage of benzene.
Note that the reaction of the Ir complex 1 was much faster than
that of the Rh analogue 2. Furthermore, the reaction of
benzene also occurred in n-octane at 100 °C to afford 3 in high
yields (entries 2−4). Although use of 1,4-dioxane as a solvent
led to a lower yield, the reaction in diglyme (2-methoxyethyl
ether) gave 3 in 96% yield (entries 5 and 6). The resulting
phenyl complex 3 was isolated as an air-stable orange solid in
95% yield by column chromatography on silica gel.
1
Complex 3 was identified on the basis of H and 13C NMR
spectra. The spectral features are consistent with Cs symmetry
in solution. In the 1H NMR spectrum of 3 measured in CDCl3,
phenyl group signals were observed at δ 6.42 (1H) and 6.52−
6.69 (4H). The signal for the acetate ligand at δ 2.03 was
shifted to slightly higher field than that of 1 (δ 1.67), probably
due to the κ2 coordination. In the 13C NMR spectrum, the
signal for the ipso carbon of the phenyl group appeared at δ
121.6. The IR spectrum of 3 showed the bands arising from the
κ2-acetate ligand at 1448 and 1382 cm−1, which were shifted
from the that for the κ1-acetate ligand of 1 (1645 cm−1).
The molecular structure of 3 was unambiguously confirmed
by single-crystal X-ray diffraction using crystals obtained from
dichloromethane/hexane solution. The ORTEP diagram of 3 is
shown in Figure 2. The geometry of the Ir atom was a distorted
Figure 1. ORTEP diagram of 1 with thermal ellipsoids given at the
50% probability level. Selected bond lengths (Å): Ir1−C1 = 1.936(3),
Ir1−N1 = 2.058(3), Ir1−N2 = 2.052(3), Ir1−O3 = 2.037(3), Ir1−O5
= 2.058(3), Ir1−O7 = 2.206(3). Selected bond angles (deg): N2−
Ir1−N1 = 158.73(12), C1−Ir1−N1 = 78.98(14), C1−Ir1−N2 =
79.76(13), C1−Ir1−O3 = 85.46(12), C1−Ir1−O5 = 88.53(12), C1−
Ir1−O7 = 176.51(14).
structural features of the Ir complex 1 are similar to those of the
Rh(III) acetate complex (phebox)Rh(OAc)2(H2O) (2).15 At
the Ir center, two κ1-acetate ligands are coordinated to the
apical positions and the water is attached to the equatorial
position. The O4−O7 and O6−O7 bond lengths of 2.64 and
2.56 Å, respectively, suggest the existence of hydrogen bonding
between the acetate ligands and H2O. The Ir−C1 bond length
of 1.936(3) Å is comparable to that of 2 (Rh−C = 1.9234(18)
Å).15
Reaction of 1 with Arenes. When a solution of the Ir
acetate complex 1 was heated in benzene, the corresponding
phenyl complex (phebox)Ir(Ph)(OAc) (3) was obtained in
84% NMR yield (Table 1, entry 1). This result indicates that
a
Table 1. Reaction of 1 with Benzene
Figure 2. ORTEP diagram of 3 with thermal ellipsoids given at the
50% probability level. Selected bond lengths (Å): Ir1−N1 = 2.051(3),
Ir1−N2 = 2.047(3), Ir1−O3 = 2.239(3), Ir1−O4 = 2.243(3), Ir1−C1
= 1.919(3), Ir1−C19 = 2.011(4), C19−C20 = 1.407(5), C20−C21 =
1.397(6), C21−C22 = 1.384(6), C22−C23 = 1.374(6), C23−C24 =
1.394(5), C19−C24 = 1.405(5), O3−C25 = 1.273(5), O4−C25 =
1.261(5). Selected bond angles (deg): N1−Ir1−N2 = 158.54(13),
C1−Ir1−N1 = 79.33(14), C1−Ir1−N2 = 79.33(14), C1−Ir1−C19 =
93.19(15), C1−Ir1−O3 = 107.21(13), C1−Ir1−O4 = 165.77(13),
C20−C19−Ir1 = 127.8(3), C24−C19−Ir1 = 115.7(3).
yield
b
b
entry amt of C6H6 (equiv)
solvent
conversn of 1 (%)
(%)
c
octahedron with an N1−Ir1−N2 angle of 158.54(13)°. The
phenyl group was coordinated at a position perpendicular to
the phebox plane. The Ir−C19 bond length of 2.011(4) Å was
comparable to that of (phebox)Rh(Ar)(OAc) (Rh−C =
1.993(2) Å).11 In addition, the phenyl moiety was bent slightly
toward the acetate ligand in comparison with the C20−C19−
Ir1 (127.8(3)°) and C24−C19−Ir1 (115.7(3)°) bond angles,
indicating large steric repulsion between the phenyl moiety and
the phebox ligand. The κ2-acetate ligand was coordinated to the
1
2
3
4
5
6
2200
100
200
500
100
100
100
95
99
99
79
99
84
90
95
99
67
96
n-octane
n-octane
n-octane
1,4-dioxane
diglyme
a
Reaction conditions unless noted otherwise: 1 (0.03 mmol), benzene
(100−500 mmol), solvent (3 mL), 100 °C, 9 h. Determined by H
NMR. Reaction conditions: 80 °C, 8 h.
b
1
c
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Ir center. The two Ir−O bond lengths of 2.239(3) and 2.243(3)
Å were slightly longer than that of the κ1-acetate ligand in 1.
Previous observations revealed that the Rh(III) chloride
complex (phebox)RhCl2(H2O) did not react with benzene
upon heating.11 Similarly, the Ir(III) chloride complex
(phebox)IrCl2(H2O) (4) did not undergo C−H bond
activation of benzene, even when heated to 80 °C for 24 h;
only the starting complex 4 was recovered. These results
suggest that the acetate ligand has a significant effect on the
formation of 3 via C−H bond activation of benzene.
Table 3. Relative Reaction Rate Among Monosubstituted
Arenes
a
b
entry
arene (X)
ratio
1
2
3
4
OMe
Cl
1.7
1.1
1.4
1.6
COMe
NO2
a
Reaction conditions: 1:toluene:C6H5R = 1:250:250, 100 °C, 2 h, n-
b
1
octane. Determined by H NMR.
To obtain additional information about the reactivity of 1,
the monosubstituted arenes C6H5R (R = OMe, Me, Cl, COMe,
NO2) were investigated. Reactions of 1 with 500 equiv of
C6H5R in n-octane at 100 °C for 9 h were performed (Table 2).
faster than those with toluene. Similar results for C−H bond
activation of monosubstituted arenes with the Rh acetate
complex 2 have been reported, which showed the relative rate
order C6H5OMe (1.8) > C6H5COMe (1.6) > C6H5CF3 (1.2) >
C6H5Cl (1.2) > C6H5Me (1).11 If C−H activation proceeds
under an electrophilic activation process, a linear correlation
between the reaction rate of substituted aromatic compounds
and Hammett constant σ should be obtained.10 Aoyama and
Ogoshi reported electrophilic C−H bond activation of arenes
by the Rh(III) porphyrin complex, where a good correlation
between the reaction rates and σ values provided a substituent
constant ρ of −5.43.17 Shul’pin also described electrophilic C−
H bond activation of an arene by PtCl62−, which produced a ρ
value of −3.0.18 The result of the phebox-Ir complex 1 is
inconsistent with the electrophilic activation process.
For additional insight into the reaction, the kinetic isotope
effect (KIE) was determined. Reaction of 1 with a 1:1 mixture
of benzene and benzene-d6 (500 equiv) at 100 °C for 6 h
afforded a KIE value of 2.9 0.1, which was smaller than that
of the Rh(III) acetate complex 2 (5.4).11 A KIE value for C−H
bond activation of nitrobenzene was 2.0 0.4 for the reaction
of 1 with a 1:1 mixture of nitrobenzene and nitrobenzene-d5 at
100 °C for 5 h. Periana reported inter- and intramolecular KIE
values of 1.07 0.24 and 2.65 0.56, respectively, for C−H
bond activation of benzene by the Ir(III) hydroxide complex,
indicating rate-determining precoordination of benzene.19
A plausible reaction mechanism might involve three steps:
formation of the η2-benzene intermediate A, subsequent
acetate-assisted C−H bond cleavage via the transition state B,
and dissociation of acetic acid from the intermediate C
(Scheme 1). Initially, dissociation of H2O from 1 could
Table 2. Reaction of 1 with C6H5X
ab
,
a
entry
arene (R)
product
yield (%)
ratio
1
2
3
4
5
OMe
Me
5a,b
6a,b
7a,b
8a,b
9a,b
99
85
90
90
98
1:0.7
1:1.2
1:1.9
1:4.1
1:12.3
Cl
COMe
NO2
a
b
1
Determined by H NMR. Yields of a mixture of para and meta
isomers.
Arenes with electron-donating and -withdrawing groups
provided the corresponding aryl complexes as a mixture of
two isomers formed by C−H bond activation at the meta and
para positions. For the electron-rich anisole and toluene, the
reaction at the para position occurs prior to the reaction at the
meta position, giving the methoxyphenyl complexes 5a,b (99%,
5a:5b = 1:0.7) and the tolyl complexes 6a,b (85%, 6a:6b =
1:1.2), respectively (entries 1 and 2). Reaction with
chlorobenzene afforded a 1:1.9 mixture of the chlorophenyl
complexes 7a,b (90%), indicating that the relative reaction rates
at the para and meta positions were nearly identical (entry 3).
In this reaction, products generated by C−Cl bond oxidative
addition were not detected. For the electron-withdrawing
arenes acetophenone and nitrobenzene, C−H bond activation
occurred predominantly at the meta position to give the
corresponding aryl complexes 8a,b (90%, 8a:8b = 1:4.1) and
9a,b (98%, 9a:9b = 1:12.3), respectively (entries 4 and 5). In
those reactions, ortho C−H bond activation was suppressed
even if a directing group was attached. As observed in the
molecular structure of 3, steric repulsion with the phebox
skeleton and an ortho substituent might be significant factors.
Furthermore, the relative reaction rates of several mono-
substituted arenes were determined by the reaction of 1 with a
1:1 mixture of toluene and C6H5R (R = OMe, Cl, COMe,
NO2) in n-octane at 100 °C. After heating for 2 h, the product
Scheme 1. Proposed Mechanism
1
ratio was analyzed by H NMR spectroscopy (Table 3). The
results showed that the order of C−H activation rate was
C6H5OMe (1.7) > C6H5NO2 (1.6) > C6H5COMe (1.4) >
C6H5Cl (1.1) > C6H5Me (1). Interestingly, reactions of arenes
with both electron-donating and -withdrawing groups were
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generate a 16-electron unsaturated intermediate, followed by
coordination of benzene to give η2-benzene intermediate A.
This equilibrium reaction for formation of A could affect the
relative reaction rate among monosubstituted arenes, as shown
in Table 3. In this case, an oxygen-containing functional group,
such as OMe, may promote incorporation of the arene into the
phebox−Ir framework. Subsequently, C−H bond cleavage
could proceed via the six-membered cyclic transition state B. In
this step, the agostic interaction of the C−H bond to the metal
center could enhance the acidity of the C−H bond, which
promotes proton abstraction by the acetate ligand.6 Finally,
elimination of acetic acid from C gives the phenyl complex 2.
The intermolecular KIE value obtained by reaction of 1 with
arenes implied two plausible mechanisms for the rate-
determining step.20 The simple mechanism involves irreversible
C−H bond cleavage as the rate-determining step. The other
mechanism involves reversible C−H bond cleavage followed by
the rate-determining dissociation of the coordinated acetic acid.
H/D Exchange. The reactivity of the phenyl complex 3 was
elucidated. Pyrolysis of 3 in C6D6 at 100 °C was monitored by
1H NMR spectroscopy, which revealed that the intensity of
signals for the para, meta, and ortho protons of the phenyl
group in 3 decreased simultaneously (Figure 3). The
deuterated complex 3-d5. In contrast, oxidative addition could
give the Ir(V) intermediate F, which could undergo reductive
elimination to produce 3-d5. Thus, the Cp*Ir(OTf)Me system
suggests an oxidative addition mechanism experimentally and
theoretically.3
Catalytic Borylation of Benzene. Iridium-catalyzed
borylation is a useful method for transformation of arenes
and alkanes by direct C−H functionalization.21,22 Reactivity of
the phenyl complex 3 toward bis(pinacolato)diboron
(B2(pin)2) or pinacolborane (HB(pin)) was examined (Scheme
3). Treatment of 3 with 5 equiv of B2(pin)2 in n-octane at 100
Scheme 3. Reaction of 3 with B2(pin)2 or HB(pin)
°C resulted in formation of PhB(pin) in 80% yield via C−B
bond formation. In contrast, the reaction of 3 with HB(pin)
was much slower than that of B2(pin)2 and a large amount of 3
(90%) was recovered.
Next, the catalytic borylation reaction of arenes with B2(pin)2
or HB(pin) in the presence of the Ir acetate complex 1 or Rh
acetate complex 2 was conducted (Table 4). The catalytic
a
Table 4. Catalytic Borylation of Arenes
b
entry
cat.
arene (R)
borane
yield (%)
1
2
3
4
5
6
7
1
2
H
B2(pin)2
B2(pin)2
B2(pin)2
HB(pin)
HB(pin)
B2(pin)2
B2(pin)2
B2(pin)2
70
52
0
H
Figure 3. Plot of the deuterated ratio of the phenyl group at para
(purple circles), meta (green squares), and ortho (blue triangles)
positions vs time for the reaction of 3 in C6D6 at 100 °C.
c
4
H
1
2
1
1
1
H
54
27
H
e
OMe
Cl
Me
62
f
54
deuterated ratio of each position was 54% at a reaction time
of 31 h, indicating replacement of the phenyl group with the
external C6D6. The reaction of 3 with toluene-d8 at 100 °C also
proceeded to give the tolyl complex 6-d7 (Figure S1,
Supporting Information). This arene exchange reaction may
proceed via (a) σ-bond metathesis or (b) oxidative addition and
reductive elimination (Scheme 2). As a first step, the reaction
site might be opened by κ1-acetate coordination. For σ-bond
metathesis, the four-center transition state E provides the
d
g
8
41
a
Reaction conditions unless noted otherwise: arene (60 mmol),
B2(pin)2/HB(pin) (1 mmol), cat. (5 mol %), 80 °C, 48 h. NMR
yields based on the number of borons. Use of tBuOK (10 mol %).
Reaction time: 4 days. ortho:meta:para = 0.6:3.2:1.0. meta:para =
b
c
d
e
f
g
2.9:1.0. benzyl:meta:para = 1.1:1.8:1.0.
Scheme 2. H/D Exchange of 2 with C6D6
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reaction of B2(pin)2 with excess benzene proceeded in the
presence of 5 mol % of 1 at 80 °C for 48 h to give PhB(pin) in
70% yield (entry 1). In contrast, use of the Rh analogue 2
decreased the yield, and the chloride complex 4 showed no
catalytic activity (entries 2 and 3). Use of HB(pin) as a boron
source also gave the borylated product in moderate yield
(entries 4 and 5). Reaction of monosubstituted arenes with
B2(pin)2 afforded a mixture of borylated products in moderate
yields. Anisole and chlorobenzene provided mixtures with the
ratios ortho:meta:para = 0.6:3.2:1 and 0:2.9:1, respectively
(entries 6 and 7). These isomer ratios are similar to those of
other Ir catalysts, such as the Ir/bipyridine system.23 For
toluene, a benzyl-substituted product as well as meta- and para-
substituted products were obtained in the ratio 1.1:1.8:1 (entry
8). The formation of benzyl-substituted products in the
iridium-catalyzed borylation of methyl-substituted arenes with
the silylborane Et3SiB(pin) has been reported previously.24 In
the present system, product distributions in the catalytic
reaction were inconsistent with the results of the stoichiometric
reaction. Although an active intermediate was not identified in
the catalytic reaction, a boryl intermediate, which was generated
by reaction of 1 with B2pin2 or HBpin, might be involved in C−
H bond activation.25
Figure 4. ORTEP diagram of 10 with thermal ellipsoids given at the
50% probability level. Selected bond lengths (Å): Ir1−N1 = 2.050(4),
Ir1−N2 = 2.051(3), Ir1−O3 = 2.245(3), Ir1−O4 = 2.265(4), Ir1−C1
= 1.922(4), Ir1−C19 = 2.061(5). Selected bond angles (deg): N1−
Ir1−N2 = 158.33(15), C1−Ir1−N1 = 78.89(17), C1−Ir1−N2 =
79.58(17), C1−Ir1−C19 = 85.15(18), C1−Ir1−O3 = 170.26(16),
C1−Ir1−O4 = 112.46(17).
Å, which was slightly longer than that of 3 (Ir−C19 = 2.011(4)
Å).
The kinetic isotope effect (KIE) was 4.0, as determined by
the reaction of 1 with a 1:1 mixture of octane and octane-d18 at
160 °C for 70 h. This large value suggests that the C−H bond
cleavage step could be the rate-determining step. A plausible
mechanism for alkane C−H bond activation is shown in
Scheme 5. A coordinatively unsaturated intermediate, generated
Reaction with n-Alkanes. The C(sp3)−H bond activation
of alkanes is challenging because of the weak interaction
between metal and alkane, and detailed studies for alkane
activation on metal complexes have been reported.26 We
investigated the C−H bond activation of n-alkanes by the Ir
acetate complex 1. Reaction of 1 in n-heptane in the presence
of K2CO3 at 160 °C for 70 h successfully afforded the
corresponding n-heptyl complex 10 (Scheme 4). After
Scheme 5. Proposed Mechanism for C−H Bond Activation
of n-Alkanes
Scheme 4. Reaction of 1 with n-Alkanes
purification by column chromatography on silica gel, the
complex 10 was isolated in 80% yield. Similarly, the reaction of
1 with n-octane gave the n-octyl complex 11 in 78% yield. In
these reactions, addition of K2CO3 enhanced the product yield,
likely due to trapping of acetic acid generated in situ. In the 1H
NMR spectrum of the heptyl complex 10, the signal of the Ir-
bonded methylene was observed at δ 0.59 (2H). The 13C NMR
spectrum of 10 also showed a signal for Ir−CH2 at δ −2.9 ppm.
by dissociation of H2O, captures the alkane to give a σ-alkane
intermediate. Successive C−H bond activation could proceed
via a six-membered cyclic transition state involving the agostic
interaction of the C−H bond with the metal center and outer-
sphere interaction with the acetate ligand. We propose that
both arene and alkane C−H bond activation might involve a
similar cyclic transition state.
1
In the H and 13C NMR spectra of the octyl complex 11, the
characteristic signals for Ir−CH2 were observed at δH 0.58 ppm
CONCLUSION
and δC −2.9 ppm.
■
The molecular structure of 10 was confirmed by X-ray
diffraction; the ORTEP diagram is shown in Figure 4. The
structural features of the alkyl complex 10 were similar to those
of the phenyl complex 3. The Ir center possessed pseudo-
octahedral geometry at the N1−Ir1−N2 angles (158.33(15)°),
and the acetate ligand was coordinated to the Ir atom in the κ2
coordination mode. The alkyl groups were coordinated to
apical positions. The Ir−C19 bond length of 10 was 2.061(5)
C−H bond activation by the Ir acetate complex 1 containing an
NCN pincer phebox ligand proceeded in n-octane at 100 °C to
give the corresponding aryl complexes. For monosubstituted
arenes, reactions at the para and meta positions occurred to
produce a mixture of isomers. The distribution of the isomers
depended on the electronic properties of the arenes. In
contrast, the relative reaction rates among monosubstituted
arenes were inconsistent with the electronic properties of the
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arenes, probably due to pre-equilibrium formation of an η2-
arene intermediate. A plausible mechanism might involve a
cyclic transition state containing a σ-coordinated C−H bond
and acetate ligand. The resulting phenyl complex 3 underwent
the arene exchange reaction, which involves σ-bond metathesis
or an oxidative addition and reductive elimination sequence.
Furthermore, the reaction of 3 with B2(pin)2 or HB(pin)
resulted in C−B bond formation to give the borylated
compound. The catalytic borylation reaction of arenes with
B2(pin)2 or HB(pin) in the presence of 1 also furnished the
corresponding arylborane derivatives. In addition, C−H bond
activation of n-alkane by 1 produced the corresponding alkyl
complexes.
2H); for 6b, 0.99 (s, 6H), 1.24 (s, 6H), 2.07 (s, 3H), 2.15 (s, 3H), 2.68
(s, 6H), 3.57 (d, J = 8.3 Hz, 2H), 3.66 (d, J = 8.3 Hz, 2H), 6.58 (s,
1H), 6.59 (d, J = 7.6 Hz, 1H), 6.63 (d, J = 7.6 Hz, 1H), 6.81 (t, J = 7.6
Hz, 1H), 6.92 (s, 1H). 13C NMR (75 MHz, C6D6, room temperature):
for 6a,b, δ 18.8, 20.6, 21.7, 25.6, 25.6, 26.5, 26.6, 26.6, 66.0, 816, 117.4,
122.1, 122.3, 123.5, 125.3, 125.6, 126.5, 129.5, 131.8, 133.7, 134.5,
135.4, 139.6, 139.6, 176.5, 181.2, 181.3, 184.4, 184.5.
Reaction of 1 with Chlorobenzene. A solution of 1 (31.4 mg,
0.050 mmol) in chlorobenzene (2.6 mL, 25 mmol) and n-octane (3
mL) was heated at 100 °C for 9 h under an argon atmosphere. After
removal of the solvent, the yellow residue was purified by column
chromatography on silica gel (AcOEt) to give an orange solid of 7a,b
(30.1 mg, 0.045 mmol, 91%). Anal. Calcd for C26H30ClIrN2O4: C,
1
47.16; H, 4.57; N, 4.23. Found: C, 47.06; H, 4.54; N, 3.96. H NMR
(300 MHz, C6D6, room temperature): for 7a, δ 0.87 (s, 6H), 1.19 (s,
6H), 2.03 (s, 3H, OCOCH3), 2.65 (s, 6H), 3.57 (d, J = 8.3 Hz, 2H),
3.66 (d, J = 8.3 Hz, 2H), 6.54 (s, 1H), 6.80 (d, J = 7.5 Hz, 2H), 6.88
(d, J = 7.5 Hz, 2H); for 7b, 0.91 (s, 6H), 1.17 (s, 6H), 2.03 (s, 3H,
OCOCH3), 2.62 (s, 6H), 3.54 (d, J = 8.4 Hz, 2H), 3.63 (d, J = 8.4 Hz,
2H), 6.52 (s, 1H), 6.60 (t, J = 7.4 Hz, 1H), 6.65 (d, J = 7.4 Hz, 1H),
6.80 (d, J = 7.4 Hz, 2H), 7.20 (s, 1H). 13C NMR (75 MHz, C6D6,
room temperature): for 7a, δ 19.2, 25.9 (OAc), 26.9, 27.0, 66.3, 82.0,
120.8, 124.3, 125.9, 125.9, 126.0, 130.8, 140.3, 176.9, 180.5, 185.3; for
7b, 19.2, 25.9, 26.9, 27.0, 66.3, 82.0, 121.5, 124.5, 125.8, 126.8, 133.6,
134.7, 136.4, 140.5, 177.0, 180.2, 185.4.
EXPERIMENTAL SECTION
■
1
General Procedures. H and 13C NMR spectra were obtained at
1
25 °C on a Varian Mercury 300 spectrometer. H NMR chemical
shifts are reported in δ units, in ppm relative to the singlet at 7.26 ppm
for CDCl3 and at 7.16 ppm for C6D6. 13C NMR spectra are reported in
terms of chemical shifts (δ, ppm) relative to the triplet at 77.0 ppm for
CDCl3 and at 128 ppm for C6D6. Infrared spectra were recorded on a
JASCO FT/IR-230 or JASCO FT/IR-4200 spectrometer. Mass
spectra were recorded on a JEOL JMS-700 instrument. Elemental
analyses were recorded on a YANACO MT-6 instrument. Column
chromatography was performed with a silica gel column (Kanto
Kagaku Silica gel 60N).
Reaction of 1 with Acetophenone. A solution of 1 (31.5 mg,
0.0502 mmol) in acetophenone (2.6 mL, 25 mmol) and n-octane (3
mL) was heated at 100 °C for 9 h under an argon atmosphere. After
removal of the solvent, the yellow residue was purified by column
chromatography on silica gel (AcOEt) to give an orange solid of 8a,b
(29.9 mg, 0.0446 mmol, 89%). Anal. Calcd for C28H33IrN2O5: C,
Reaction of 1 with Benzene. A solution of 1 (62.7 mg, 0.1
mmol) in benzene (4.4 mL, 49 mmol) and n-octane (10 mL) was
heated at 100 °C for 9 h under an argon atmosphere. After removal of
the solvent, the yellow residue was purified by column chromatog-
raphy on silica gel (toluene/THF 1/1) to give an orange solid of 3
(59.6 mg, 0.095 mmol, 95%). HRMS (FAB, m/z): 628.1929; calcd
628.1913 [M+]. Anal. Calcd for C26H31IrN2O4: C, 49.75; H, 4.98; N,
4.46. Found: C, 49.53; H, 4.94; N, 4.37. 1H NMR (300 MHz, CDCl3,
room temperature): δ 1.05 (s, 6H), 1.42 (s, 6H), 2.03 (s, 3H), 2.63 (s,
6H), 4.37 (d, J = 8.3 Hz, 2H), 4.44 (d, J = 8.3 Hz, 2H), 6.42 (d, J = 6.9
Hz, 1H), 6.52−6.69 (m, 4H). 13C NMR (75 MHz, CDCl3, room
temperature): δ 18.9, 25.4, 26.9, 27.0, 66.2, 82.0, 120.6, 121.6 (Ir−
Cipso), 123.6, 124.9, 125.2, 134.4, 140.0, 176.6, 178.6, 184.7. IR (KBr,
cm−1): 1593, 1571, 1457, 1392.
Reaction of 1 with Anisole. A solution of 1 (31.6 mg, 0.05
mmol) in anisole (2.7 mL, 25 mmol) and n-octane (3 mL) was heated
at 100 °C for 9 h under an argon atmosphere. After removal of the
solvent, the yellow residue was purified by column chromatography on
silica gel (AcOEt) to give an orange solid of 5a,b (32.6 mg, 0.049
mmol, 99%). Anal. Calcd for C27H33IrN2O5: C, 49.30; H, 5.06; Ir, N,
4.26. Found: C, 49.18; H, 5.29; N, 3.94. 1H NMR (300 MHz, CDCl3,
room temperature): for 5a, δ 1.06 (s, 6H), 1.42 (s, 6H), 2.02 (s, 3H,
OCOCH3), 2.63 (s, 6H), 3.62 (s, 3H, OCH3), 4.37 (d, J = 8.3 Hz,
2H), 4.44 (d, J = 8.3 Hz, 2H), 6.26 (dt, J = 8.9, 2.4 Hz, 2H), 6.33 (dt, J
= 8.9, 2.4 Hz, 2H), 6.62 (s, 1H); for 5b, 1.07 (s, 6H), 1.42 (s, 6H),
2.02 (s, 3H, OCOCH3), 2.62 (s, 6H), 3.56 (s, 3H, OCH3), 4.37 (d, J =
8.3 Hz, 2H), 4.44 (d, J = 8.3 Hz, 2H), 5.65 (dd, J = 1.4, 2.5 Hz, 1H),
6.14 (ddd, J = 0.9, 2.5, 8.0 Hz, 1H), 6.44 (dt, J = 7.5, 1.4 Hz, 2H), 6.59
(t, J = 7.8 Hz, 1H), 6.62 (s, 1H). 13C NMR (75 MHz, C6D6, room
temperature): for 5a,b: δ 19.2, 26.0, 26.9, 27.0, 27.0, 66.3, 82.0, 121.8,
123.2, 124.4, 124.6, 125.3, 125.8, 126.0, 131.8, 135.2, 135.3, 135.5,
137.7, 140.0, 140.4, 177.1, 180.6, 185.3, 197.3.
1
50.21; H, 4.97; N, 4.18. Found: C, 50.34; H, 4.91; N, 3.93. H NMR
(300 MHz, CDCl3, room temperature): for 8a, δ 1.01 (s, 6H), 1.42 (s,
6H), 2.03 (s, 3H, OCOCH3), 2.40 (s, 3H, COCH3), 2.64 (s, 6H), 4.37
(d, J = 8.4 Hz, 2H), 4.45 (d, J = 8.4 Hz, 2H), 6.63 (d, J = 8.7 Hz, 2H),
7.22 (d, J = 8.7 Hz, 2H); for 8b, 1.03 (s, 6H), 1.43 (s, 6H), 2.03 (s,
3H, OCOCH3), 2.36 (s, 3H, COCH3), 2.64 (s, 6H), 4.37 (d, J = 8.4
Hz, 2H), 4.46 (d, J = 8.4 Hz, 2H), 6.67 (s, 1H), 6.72 (d, J = 7.2 Hz,
1H), 6.73 (d, J = 7.5 Hz, 1H), 6.95 (s, 1H), 7.18 (d, J = 6.6 Hz, 1H).
13C NMR (75 MHz, CDCl3, room temperature): for 8a,b, δ 18.9, 25.4,
25.5, 26.3, 26.7, 26.9, 27.0, 27.1, 66.1 (8b), 66.2 (8a), 82.0 (8b), 82.1
(8a), 120.6, 122.0, 124.0, 124.2, 124.4, 124.9, 125.1, 130.5, 134.2,
134.8, 134.9, 136.3, 139.9, 140.3, 140.5, 176.6, 177.3, 178.0, 185.1
(8b), 185.3 (8a), 198.1 (8a), 199.2 (8b).
Reaction of 1 with Nitrobenzene. A solution of 1 (31.4 mg,
0.050 mmol) in nitrobenzene (2.6 mL, 25 mmol) and n-octane (3
mL) was heated at 100 °C for 9 h under an argon atmosphere. After
removal of the solvent, the yellow residue was purified by column
chromatography on silica gel (AcOEt) to give an orange solid of 9a,b
(29.8 mg, 0.0443 mmol, 88%). Anal. Calcd for C26H30IrN3O6: C,
1
46.42; H, 4.49; N, 6.25. Found: C, 46.65; H, 4.52; N, 6.06. H NMR
(300 MHz, C6D6, room temperature): for 9a, δ 0.75 (s, 6H), 1.58 (s,
6H), 2.00 (s, 3H, OCOCH3), 2.63 (s, 6H), 3.56 (d, J = 8.7 Hz, 2H),
3.63 (d, J = 8.7 Hz, 2H), 6.55 (s, 1H), 6.98 (d, J = 8.6 Hz, 1H), 7.67
(d, J = 8.6 Hz, 1H); for 9b, 0.80 (s, 6H), 1.16 (s, 6H), 2.03 (s, 3H,
OCOCH3), 2.62 (s, 6H), 3.53 (d, J = 8.4 Hz, 2H), 3.62 (d, J = 8.4 Hz,
2H), 6.55 (s, 1H), 6.55 (dd, J = 7.8, 8.1 Hz, 1H), 6.98 (dt, J = 7.8, 1.2
Hz, 1H), 7.60 (ddd, J = 8.1, 1.2, 2.2 Hz, 1H), 8.08 (t, J = 2.2 Hz, 1H).
13C NMR (75 MHz, C6D6, room temperature): for 9b, δ 19.2, 25.9,
26.8, 27.0, 66.3, 82.0, 116.4, 124.9, 125.6, 125.9, 125.9, 129, 140.8,
141.6, 146.2, 177.1, 179.5, 185.8.
Reaction of 1 with Toluene. A solution of 1 (31.4 mg, 0.050
mmol) in toluene (2.7 mL, 25 mmol) and n-octane (3 mL) was heated
at 100 °C for 9 h under an argon atmosphere. After removal of the
solvent, the yellow residue was purified by column chromatography on
silica gel (toluene/THF 2/1) to give an orange solid of 6a,b (31.5 mg,
0.049 mmol, 98%). Anal. Calcd for C27H33IrN2O4: C, 50.53; H, 5.18;
Reaction of 1 with n-Heptane. A mixture of 1 (62.9 mg, 0.100
mmol) and K2CO3 (13.9 mg, 0.10 mmol) in n-heptane (6 mL) was
heated at 160 °C for 70 h under an argon atmosphere. After removal
of the solvent, the yellow residue was purified by column
chromatography on silica gel (toluene/THF 2/1) to give an orange
solid of 10 (52.1 mg, 0.0802 mmol, 80%). Anal. Calcd for
C27H41IrN2O4: C, 49.90; H, 6.36; N, 4.31. Found: C, 50.11; H,
1
N, 4.36. Found: C, 50.71; H, 5.12; N, 3.88. H NMR (300 MHz,
C6D6, room temperature): for 6a, δ 0.99 (s, 6H), 1.24 (s, 6H), 2.07 (s,
3H), 2.15 (s, 3H), 2.68 (s, 6H), 3.58 (d, J = 8.4 Hz, 2H), 3.67 (d, J =
8.4 Hz, 2H), 6.56 (s, 1H), 6.74 (d, J = 8.0 Hz, 2H), 6.83 (d, J = 8.0 Hz,
1
6.17; N, 4.21. H NMR (300 MHz, C6D6, room temperature): δ 0.59
(m, 2H, IrCH2), 0.86 (t, J = 7.1 Hz, 3H, CH3), 1.20−1.45 (m, 6H),
4447
dx.doi.org/10.1021/om3002137 | Organometallics 2012, 31, 4442−4449

Organometallics
Article
1.27 (s, 6H), 1.39 (s, 6H), 2.10 (s, 3H), 2.66 (s, 6H), 3.81 (d, J = 8.4
Hz, 2H), 3.85 (d, J = 8.4 Hz, 2H), 6.49 (s, 1H). 13C NMR (75 MHz,
C6D6, room temperature): δ −2.9, 14.8, 19.3, 23.5, 26.3, 27.3, 27.5,
30.2, 31.6, 32.2, 32.9, 66.4, 82.4, 123.1, 125.9, 139.1, 177.0, 181.9,
184.1.
REFERENCES
■
(1) (a) Ackermann, L. Chem. Rev. 2011, 111, 1315−1345. (b) Ritleng,
V.; Sirlin, C.; Pfeffer, M. Chem. Rev. 2002, 102, 1731−1770.
(c) Balcells, D.; Clot, E.; Eisenstein, O. Chem. Rev. 2010, 110, 749−
823. (d) Lersch, M.; Tilset, M. Chem. Rev. 2005, 105, 2471−2526.
(e) Crabtree, R. H. J. Organomet. Chem. 2004, 689, 4083−4091.
(f) Kakiuchi, F.; Murai, S. Acc. Chem. Res. 2002, 35, 826−834. (g) Jia,
C.; Kitamura, T.; Fujiwara, Y. Acc. Chem. Res. 2001, 34, 633−639.
(2) (a) Arndtsen, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T.
H. Acc. Chem. Res. 1995, 28, 154−162. (b) Labinger, J. A.; Bercaw, J. E.
Nature 2002, 417, 507−514. (c) Jones, W. D. Acc. Chem. Res. 2003, 36,
140−146.
(3) (a) Tellers, D. M.; Yung, C. M.; Arndtsen, B. A.; Adamson, D. R.;
Bergman, R. G. J. Am. Chem. Soc. 2002, 124, 1400−1410. (b) Niu, S.;
Hall, M. B. J. Am. Chem. Soc. 1998, 120, 6169−6170.
(4) Fu, R.; Bercaw, J. E.; Labinger, J. A. Organometallics 2011, 30,
6751−6765.
Reaction of 1 with n-Octane. A mixture of 1 (124.5 mg, 0.198
mmol) and K2CO3 (27.7 mg, 0.20 mmol) in n-octane (8 mL) was
heated at 160 °C for 70 h under an argon atmosphere. After removal
of the solvent, the yellow residue was purified by column
chromatography on silica gel (toluene/THF 2/1) to give an orange
solid of 11 (102.3 mg, 0.154 mmol, 78%). Anal. Calcd for
C28H43IrN2O4: C, 50.66; H, 6.53; N, 4.22. Found: C, 50.44; H,
6.72; N, 4.00. 1H NMR (300 MHz, C6D6, room temperature): δ 0.54−
0.61 (m, 2H), 0.85 (t, J = 6.8 Hz, 3H), 1.18−1.44 (m, 10H), 1.28 (s,
6H), 1.38 (s, 6H), 1.66−1.74 (m, 2H), 2.08 (s, 3H), 2.64 (s, 6H), 3.81
(d, J = 8.4 Hz, 2H), 3.85 (d, J = 8.4 Hz, 2H), 6.48 (s, 1H). 13C NMR
(75 MHz, C6D6, room temperature): δ −2.9, 14.8, 19.3, 23.5, 26.3,
27.3, 27.5, 30.3, 30.5, 31.6, 32.2, 32.6, 66.4, 82.1, 123.1, 125.9, 139.1,
177.0, 181.9, 184.0. IR (KBr, cm−1): 1591, 1541, 1448, 1382.
Kinetic Isotope Effect. Benzene. A mixture of 1 (10 mg, 0.016
mmol), C6H6 (350 μL, 3.9 mmol), and C6D6 (350 μL, 3.9 mmol) in
octane (2 mL) was heated at 100 °C for 6 h under an argon
atmosphere. After removal of the solvent, the crude product was
(5) (a) Davies, D. L.; Al-Duaij, O.; Fawcett, J.; Giardiello, M.; Hilton,
S. T.; Russell, D. R. Dalton Trans. 2003, 4132−4138. (b) Boutadla, Y.;
Davies, D. L.; Jones, R. C.; Singh, K. Chem. Eur. J. 2011, 17, 3438−
3448. (c) Boutadla, Y.; Davies, D. L.; Macgregor, S. A.; Poblador-
Bahamonde, A. I. Dalton Trans. 2009, 5887−5893. (d) Boutadla, Y.;
Al-Duaij, O.; Davies, D. L.; Griffith, G. A.; Singh, K. Organometallics
2009, 28, 433−440. (e) Davies, D. L.; Donald, S. M. A.; Al-Duaij, O.;
1
analyzed by H NMR spectroscopy in CDCl3.
Nitrobenzene. A mixture of 1 (10 mg, 0.016 mmol), C6H5NO2
(410 μL, 4.1 mmol), and C6D5NO2 (410 μL, 4.1 mmol) in octane (2
mL) was heated at 100 °C for 5 h under an argon atmosphere. After
Macgregor, S. A.; Polleth, M. J. Am. Chem. Soc. 2006, 128, 42104211.
̈
(f) Davies, D. L.; Donald, S. M. A.; Macgregor, S. A. J. Am. Chem. Soc.
2005, 127, 13754−13755.
1
removal of the solvent, the crude product was analyzed by H NMR
spectroscopy in CDCl3.
(6) (a) Ess, D. H.; Goddard, W. A., III; Periana, R. A. Organometallics
2010, 29, 6459−6472. (b) Ess, D. H.; Nielsen, R. J.; Goddard, W. A.,
III; Periana, R. A. J. Am. Chem. Soc. 2009, 131, 11686−11688.
(7) (a) Tenn, W. J., III; Young, K. J. H.; Bhalla, G.; Oxgaard, J.;
Goddard, W. A., III; Periana, R. A. J. Am. Chem. Soc. 2005, 127,
14172−14173. (b) Bischof, S. M.; Ess, D. H.; Meier, S. K.; Oxgaard, J.;
Nielsen, R. J.; Bhalla, G.; Goddard, W. A., III; Periana, R. A.
Organometallics 2010, 29, 742−756.
Octane. A mixture of 1 (19 mg, 0.030 mmol), K2CO3 (4.2 mg,
0.033 mmol), octane (706 mg, 6.2 mmol), and octane-d18 (833 mg, 6.3
mmol) was heated at 160 °C for 70 h under an argon atmosphere.
1
After removal of the solvent, the crude product was analyzed by H
NMR spectroscopy in C6D6.
Catalytic Reaction of Benzene with B2(pin)2. A mixture of
B2(pin)2 (253.9 mg, 1.0 mmol), benzene (5.3 mL, 60 mmol), and 3
(31.4 mg, 0.05 mmol) was stirred at 80 °C for 48 h under an argon
atmosphere. After heating, the reaction mixture was cooled to room
temperature and the solvent was removed under reduced pressure.
The product yield was determined by the 1H NMR spectrum by
comparison with the integral ratio of the reference compound Cp2Fe.
X-ray Analysis for 1, 3, and 10. The diffraction data were
collected on a Bruker SMART APEX CCD diffractometer with
graphite-monochromated Mo Kα radiation (λ = 0.710 73 Å). An
empirical absorption correction was applied by using SADABS. The
structure was solved by direct methods and refined by full-matrix least
squares on F2 using SHELXTL. All non-hydrogen atoms were refined
with anisotropic displacement parameters. All hydrogen atoms were
located on calculated positions and refined as rigid groups.
(8) (a) DeYonker, N. J.; Foley, N. A.; Cundari, T. R.; Gunnoe, T. B.;
Petersen, J. L. Organometallics 2007, 26, 6604−6611. (b) Cundari, T.
R.; Grimes, T. V.; Gunnoe, T. B. J. Am. Chem. Soc. 2007, 129, 13172−
13182. (c) Feng, Y.; Lail, M.; Barakat, K. A.; Cundari, T. R.; Gunnoe,
T. B.; Petersen, J. L. J. Am. Chem. Soc. 2005, 127, 14174−14175.
(9) (a) Zhang, X.; Kanzelberger, M.; Emge, T. J.; Goldman, A. S. J.
Am. Chem. Soc. 2004, 126, 13192−13193. (b) Krogh-Jespersen, K.;
Czerw, M.; Kanzelberger, M.; Goldman, A. S. J. Chem. Inf. Comput. Sci.
2001, 41, 56−63. (c) Kanzelberger, M.; Singh, B.; Czerw, M.; Krogh-
Jespersen, K.; Goldman, A. S. J. Am. Chem. Soc. 2000, 122, 11017−
11018.
(10) Ben-Ari, E.; Gandelman, M.; Rozenberg, H.; Shimon, L. J. W.;
Milstein, D. J. Am. Chem. Soc. 2003, 125, 4714−4715.
(11) Ito, J.; Nishiyama, H. Eur. J. Inorg. Chem. 2007, 1114−1119.
(12) Chan, K. S.; Lau, C. M. Organometallics 2006, 25, 260−265.
(13) Nishiyama, H.; Ito, J. Chem. Commun. 2010, 46, 203−212.
(14) Ito, J.; Shiomi, T.; Nishiyama, H. Adv. Synth. Catal. 2006, 348,
1235−1240.
(15) Kanazawa, Y.; Tsuchiya, Y.; Kobayashi, K.; Shiomi, T.; Itoh, J.;
Kikuchi, M.; Yamamoto, Y.; Nishiyama, H. Chem. Eur. J. 2005, 12, 63−
71.
ASSOCIATED CONTENT
■
S
* Supporting Information
A figure, a table, and CIF files giving experimental and
crystallographic data for 1, 3 and 10. This material is available
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
(16) Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165−195.
(17) Aoyama, Y.; Yoshida, T.; Sakurai, K.; Ogoshi, H. Organometallics
1986, 5, 168−173.
■
Corresponding Author
*E-mail: jito@apchem.nagoya-u.ac.jp (J.I.); hnishi@apchem.
nagoya-u.ac.jp (H.N.).
(18) Shul’pin, G. B.; Nizova, G. V.; Nikitaev, A. T. J. Organomet.
Chem. 1984, 276, 115−153.
Notes
(19) Tenn, W. J., III; Young, K. J. H.; Oxgaard, J.; Nielsen, R. J.;
Goddard, W. A., III; Periana, R. A. Organometallics 2006, 25, 5173−
5175.
The authors declare no competing financial interest.
(20) Simmons, E. M.; Hartwig, J. F. Angew. Chem., Int. Ed. 2012, 51,
ACKNOWLEDGMENTS
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3066−3072.
This work was supported by a Grant-in-Aid from the Japan
Society for the Promotion of Science (No. 22245014).
(21) (a) Hartwig, J. F. Acc. Chem. Res. DOI: 10.1021/ar200206a.
(b) Ishiyama, T.; Miyaura, N. J. Organomet. Chem. 2003, 680, 3−11.
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(c) Mkhalid, I. A. I.; Barnard, J. H.; Marder, T. B.; Murphy, J. M.;
Hartwig, J. F. Chem. Rev. 2010, 110, 890−931.
(22) Iverson, C. N.; Smith, M. R., III J. Am. Chem. Soc. 1999, 121,
7696−7697.
(23) (a) Ishiyama, T.; Takagi, J.; Ishida, K.; Miyaura, N.; Anastasi, N.
R.; Hartwig, J. F. J. Am. Chem. Soc. 2002, 124, 390−391. (b) Nguyen,
́ ́
D. H.; Perez-Torrente, J. J.; Lomba, L.; Jimenez, M. V.; Lahoz, F. J.;
Oro, L. A. Dalton Trans. 2011, 40, 8429−8435. (c) Murata, M.;
Odajima, H.; Watanabe, S.; Masuda, Y. Bull. Chem. Soc. Jpn. 2006, 79,
1980−1982.
(24) Boebel, T. A.; Hartwig, J. F. Organometallics 2008, 27, 6013−
6019.
(25) (a) Hartwig, J. F.; Cook, K. S.; Hapke, M.; Incarvito, C. D.; Fan,
Y.; Webster, C. E.; Hall., M. B. J. Am. Chem. Soc. 2005, 127, 2538−
2552. (b) Boller, T. M.; Murphy, J. M.; Hapke, M.; Ishiyama, T.;
Miyaura, N.; Hartwig, J. F. J. Am. Chem. Soc. 2005, 127, 14263−14278.
(26) (a) Janowicz, A. H.; Bergman, R. G. J. Am. Chem. Soc. 1982, 104,
352−354. (b) Janowicz, A. H.; Bergman, R. G. J. Am. Chem. Soc. 1983,
105, 3929−3939. (c) Hoyano, J. K.; Graham, W. A. G. J. Am. Chem.
Soc. 1982, 104, 3723−3725. (d) Bell, T. W.; Brough, S.-A.; Partridge,
M. G.; Perutz, R. N.; Rooney, A. D. Organometallics 1993, 12, 2933−
2941. (e) Jones, W. D.; Feher, F. J. J. Am. Chem. Soc. 1984, 106, 1650−
1663. (f) Jones, W. D.; Maguire, J. A. Organometallics 1986, 5, 590−
591. (g) Watson, P. L. J. Am. Chem. Soc. 1983, 105, 6491−6493.
(h) Cummins, C. C.; Baxter, S. M.; Wolczanski, P. T. J. Am. Chem. Soc.
1988, 110, 8731−8733. (i) Debad, J. D.; Legzdins, P.; Lumb, S. A.;
Batchelor, R. J.; Einstein, F. W. B. J. Am. Chem. Soc. 1995, 117, 3288−
3289. (j) Tran, E.; Legzdins, P. J. Am. Chem. Soc. 1997, 119, 5071−
5072. (k) Baillie, R. A.; Man, R. W. Y.; Shree, M. V.; Chow, C.;
Thibault, M. E.; McNeil, W. S.; Legzdins, P. Organometallics 2011, 30,
6201−6217. (l) Wayland, B. B.; Ba, S.; Sherry, A. E. J. Am. Chem. Soc.
1991, 113, 5305−5311. (m) Inagaki, A.; Takemori, T.; Tanaka, M.;
Suzuki, H. Angew. Chem., Int. Ed. 2000, 39, 404−406. (n) Matsubara,
K.; Inagaki, A.; Tanaka, M.; Suzuki, H. J. Am. Chem. Soc. 1999, 121,
7421−7422. (o) Driver, T. G.; Williams, T. J.; Labinger, J. A.; Bercaw,
J. E. Organometallics 2007, 26, 294−301. (p) Kostelansky, C. N.;
MacDonald, M. G.; White, P. S.; Templeton, J. L. Organometallics
2006, 25, 2993−2998. (q) Khaskin, E.; Zavalij, P. Y.; Vedernikov, A.
N. J. Am. Chem. Soc. 2006, 128, 13054−13055. (r) Vetter, A. J.;
Flaschenriem, C.; Jones, W. D. J. Am. Chem. Soc. 2005, 127, 12315−
12322. (s) Hoyt, H. M.; Michael, F. E.; Bergman, R. G. J. Am. Chem.
Soc. 2004, 126, 1018−1019. (t) Wong-Foy, A. G.; Bhalla, G.; Liu, X.
Y.; Periana, R. A. J. Am. Chem. Soc. 2003, 125, 14292−14293.
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