Mechanistic Insights on Pd/Cu-Catalyzed Dehydrogenative Coupling of Dimethyl Phthalate

Article abstract of DOI:10.1021/acscatal.8b01095

Despite its industrial importance, very limited mechanistic information on the dehydrogenative coupling of dimethyl phthalate has been reported. Herein we report the detailed mechanism for dehydrogenative coupling of dimethyl phthalate catalyzed by [Pd(OAc)₂]/[Cu(OAc)₂]/1,10-phenanthroline·H₂O (phen·H₂O). The solution-phase analysis of the catalytic system by XANES shows the active species to be Pd(II), and EXAFS supports the formation of an (acetato)(dimethyl phthalyl)(phen)palladium(II) complex from [Pd(OAc)₂]. A formation pathway of tetramethyl 3,3′,4,4′-biphenyltetracarboxylate via disproportionation of independently prepared [Pd(OAc){C₆H₃(CO₂Me)₂-3,4}(phen)] is observed with regeneration of [Pd(OAc)₂(phen)].

Full text of DOI:10.1021/acscatal.8b01095

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Article
Mechanistic Insights on Pd/Cu-Catalyzed
Dehydrogenative Coupling of Dimethyl Phthalate
Masafumi Hirano, Kosuke Sano, Yuki Kanazawa, Nobuyuki
Komine, Zen Maeno, Takato Mitsudome, and Hikaru Takaya
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b01095 • Publication Date (Web): 15 May 2018
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ACS Catalysis
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Mechanistic Insights on Pd/Cu-Catalyzed Dehydrogenative Coupling of
Dimethyl Phthalate
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§
Masafumi Hirano,*,† Kosuke Sano,† Yuki Kanazawa,† Nobuyuki Komine,†Zen Maeno,‡,
Takato Mitsudome,*,‡ and Hikaru Takaya*,¶
†Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-
24-16 Nakacho, Koganei, Tokyo 184-8588, Japan
‡Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3
Machikaneyama, Toyonaka, Osaka 560-8531, Japan
¶Institute of Chemical Research, Kyoto University, Gokashou, Uji, Kyoto 611-0011, Japan
Supporting Information
ABSTRACT: Despite industrial importance, very limited mechanistic information on the dehydrogenative coupling of
dimethyl phthalate had been reported. Herein we report the detailed mechanism for dehydrogenative coupling of dime-
thyl phthalate catalyzed by [Pd(OAc)2]/[Cu(OAc)2×H2O]/1,10-phenanthroline×H2O (phen×H2O). The solution-phase anal-
ysis of the catalytic system by XANES shows the active species to be Pd(II) and the EXAFS supports the formation of
an (acetato)(dimethyl phthalyl)(phen)palladium(II) complex from [Pd(OAc)2]. A formation pathway of tetramethyl
3,3’,4,4’-biphenyltetracarboxylate via disproportionation of independently prepared [Pd(OAc){C6H3(CO2Me)2-
3,4}(phen)] is observed with regeneration of [Pd(OAc)2(phen)].
KYEWORDS: dehydrogenative coupling, dimethyl phthalate, mechanism, Pd-catalysis, XAFS
tetramethyl 3,3’,4,4’-biphenyltetracarboxylate (4) along
■ INTRODUCTION
with small amounts of the regioisomer, tetramethyl
2,3,3’,4’-biphenyltetracarboxylate (5), catalyzed by
Transition-metal mediated formations of biaryls are
powerful and indispensable approaches to produce elec-
tronic materials, liquid crystals, and pharmaceutical mol-
1a/[Cu(OAc)2×H2O] (2a×H2O)/1,10-phenanthroline×H2O
(phen×H2O) (eq. 1).2 Such a Wacker-type catalyst system
ecules. The synthetic methods of biaryls involve the
Ullmann coupling, the cross-coupling, and the direct ary-
lation. They are reliable but they need to prepare a halo-
genated compound and/or arylmetal compound in ad-
vance. The other problem is emission of wastes from the
reaction. The dehydrogenative coupling of arenes is the
most straightforward coupling between arenes, which is
generally catalyzed by a Pd complex with a Cu co-cata-
lyst in the presence of oxygen. This is a halogen-free pro-
cess and one can directly use aromatic compounds as re-
actants with high atom economy. However, efficiency of
the catalysis is still limited.
works only under sufficiently diluted conditions, and this
reaction requires harsh conditions. The total product yield
is mostly less than 10%. Nevertheless, this process is op-
erated in an industrial plant for production of monomers
for polyimides.
[Pd(OAc)2] (1a) (0.0653 mol %)
1,10-phenanthroline H2O (0.0653 mol %)
[Cu(OAc)2 H2O] (2a H2O) (0.196 mol %)
CO2Me
CO2Me
air, 200 ˚C, 6 h
3
MeO2C
CO2Me
(1)
CO2Me
CO2Me
+
MeO2C
MeO2C
yield 9.3% (4/5 = 94/6)
MeO2C
MeO2C
The first catalytic dehydrogenative coupling was re-
ported by Itatani and Yoshimoto for the coupling of tolu-
ene catalyzed by [Pd(OAc)2] (1a).1 They also reported de-
hydrogenative coupling of dimethyl phthalate (3) to give
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According to the analogy of the Wacker-type catalysis, a well-considered approach is indispensable to gain dis-
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the dehydrogenative arene coupling is generally proposed
to proceed as shown in Scheme 1. Namely, [Pd(OAc)2L]
gives [Pd(OAc)ArL] probably by the internal electro-
philic substitution (IES)3-7 or electrophilic aromatic sub-
stitution mechanism (step A). The resulting
[Pd(OAc)ArL] reacts with second arene, as observed by
Hartwig8 and Ozawa9 to give [PdAr2L] (step B), or
[PdAr2L] is produced by disproportionation reaction of
[Pd(OAc)ArL] (step C) as suggested by the detailed ki-
netic study using o-xylene by Stahl and co-workers.10
Then, the reductive elimination from [PdAr2L] occurs to
give the biaryl product and [PdL], which is oxidized by 2
equiv of [Cu(OAc)2L] to regenerate [Pd(OAc)2L] (step E).
tinct evidences from the XAFS experiments. In order to
shed light on the ambiguous mechanism for Pd/Cu-cata-
lyzed dehydrogenative arene coupling of 3, we prepared
putative intermediates according to the working hypothe-
sis shown in Scheme 1 by alternative methods. With their
single crystal X-ray structure analysis, NMR studies, and
their stoichiometric and catalytic reactions, we obtained a
solid evidence on the mechanism by the XAFS studies.
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■ RESULTS AND DISCUSSION
Synthesis
of
Putative
Intermediates.
[Pd(OAc)2(phen)] (1b) was prepared from [Pd(OAc)2]
(1a) according to literature method (Scheme 2).24 Be-
cause Sakaki and co-workers have shown the C-H bond
cleavage of benzene by [Pd(O2CR)2] to give
[Pd(O2CR)Ph] in the Fujiwara-Moritani reaction,4a the
2 AcOH
2 Cu(OAc)L
+
1/2O2
ArH
putative
intermediates
in
this
process
are
LPd(OAc)2
[Pd(OAc){C6H3(CO2Me)2-3,4}(phen)]
(1c)
and
step A
step E
[Pd(OAc){C6H3(CO2Me)2-2,3}(phen)] (1d). According
to the modification of the literature method,25 complex 1c
was newly prepared by the oxidative addition of dimethyl
4-bromophthalate to [Pd(dba)2] in the presence of tmda
followed by the treatments with phen×H2O and AgOAc
(route A in Scheme 2). On the other hand, the oxidative
addition of dimethyl 3-bromophthalate to [Pd(dba)2] was
almost ineffective (less than 3% yield). However, the ox-
idative addition of dimethyl 3-iodophthalate to [Pd(dba)2]
in the presence of phen×H2O gave [PdI{C6H3(CO2Me)2-
2,3}(phen)] (1e) in 78% yield, which eventually gave 1d
by the treatment with AgOAc in 91% yield (route B).
These new complexes were fully characterized by 1H and
13C NMR and elemental analysis, and 1c was also char-
acterized by X-ray structure analysis (Figure 1). The X-
ray structure of 1c is consistent with the structure esti-
mated by NMR. The Pd(1)-N(1) distance [2.123(3) Å] is
significantly longer than Pd(1)-N(2) [2.034(3) Å], which
suggests strong trans influence of C(4) in the dimethyl
phthalyl group. The selected bond distances for 1c are
listed in Table 1, along with the related Pd complexes.
H2O
AcOH
2 Cu(OAc)2L
LPd
step C
LPd(OAc)Ar
ArH
stepD
step B
Ar Ar
LPdAr2
L = ligand
AcOH
Scheme 1. Putative Mechanism for Dehydrogena-
tive Arene Coupling.
Since such dehydrogenative arene coupling of 3 is op-
erated under harsh conditions in the presence of paramag-
netic copper species, observation of the catalyst system
by conventional NMR experiments and isolation of the
key intermediate is difficult. The detailed mechanism has
therefore been largely unknown.
In this paper, we report the mechanistic insight on the
dehydrogenative coupling of 3 by the solution-phase
XAFS (X-ray absorption fine structure) using a synchro-
tron radiation. To our best knowledge, Stluts, Friedman
and co-workers were the first to bring the synchrotron
XAFS in a study of homogeneous catalysts using a Rh
complex.11 Following the pioneering study, homogeneous
catalysts involving Ti,12 V,13 Cr,14 Mo,15 Mn,16 Fe,17 Ru,18
Ni,19 Pd,20 Au21 and Cu22 were studied by XAFS. Note
that one of the authors succeeded to elucidate the mecha-
nism of paramagnetic Fe-catalyzed Kumada-Tamao-Cor-
riu coupling by the solution-phase XAFS analysis.17c The
reviews for XAFS analysis of homogenous catalysts have
been reported.23 Nevertheless, detailed mechanistic study
of homogenous catalysis using XAFS remains difficult.
The problems include inherently poor signal-to-noise ra-
tio, a result of low concentration of catalyst and back-
ground absorption by organic materials.23b In other words,
In the 1H NMR spectrum of 1c in dmso-d6, the all res-
onances assignable to the phen ligand were observed in-
equivalently because of the different ligands in the trans
positions in a square planar geometry. Upon warming to
80 ˚C, the inequivalent phen resonances eventually coa-
lesced to be equivalent.
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phen H2O
1
2
[Pd(OAc)2(phen)]
[Pd(OAc)2]
acetone
r.t., 30 min
1a
1b
3
4
5
6
7
ArBr/tmeda
benzene
phen H2O
[PdBr(Ar)(phen)]
[PdBr(Ar)(tmeda)]
THF
r.t., 24 h
50 ˚C, 38.5 h
route A
CH2Cl2
AgOAc
8
[Pd(dba)2]
r.t., 39 h
9
route B
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AgOAc
ArI/phen
[Pd(OAc)Ar(phen)]
[PdI(Ar)(phen)]
N(2)
C(4)
benzene
50 ˚C, 4 h
CH2Cl2
r.t., 4 h
1e
Ar =
3,4-C6H3(CO2Me) (1c)
2,3-C6H3(CO2Me) (1d)
Pd(1)
O(5)
N(1)
N
O
O
O
O
O
O
Pd
O
Pd
N
O
1a
commercially available
used as received
Figure
1.
Molecular
structure
of
1b
yellow crystals, 61%
CO2Me
[Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] (1c) by X-ray
with selected numbering schemes. All hydrogen at-
oms are omitted for clarity. Ellipsoids represent 50%
probability.
MeO2C
CO2Me
CO2Me
N
N
N
Pd
O
Pd
N
O
O
O
1d
variable temperature NMR experiments of 1c in the pres-
ence of added phen ligand.
1c
pale yellow prisms, 79%
yellow solid, 91%
Scheme 2. Preparations of [Pd(OAc)2(phen)] (1b),
[Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] (1c) and
[Pd(OAc){C6H3(CO2Me)2-2,3}(phen)] (1d).
Although the added free phen resonances broadened
at high temperature, almost no effect on the dynamic be-
havior of 1c was observed (cf. SI). Figure 2 shows the
variable temperature 1H NMR spectra for 1c (left) and 1d
(right) in the presence of added NaOAc. A significant
broadening of the acetate resonances of 1c and NaOAc
was observed even at 30 ˚C and they were reversibly co-
alesced around 70 ˚C. This behavior clearly shows ex-
change of the acetato ligand in 1c with NaOAc (mecha-
nism iii) on the NMR time-scale, and a reversible disso-
ciation of the acetato ligand in 1c is suggested in dmso-d6
(eq 2). Admso-d6 molecule presumably coordinates to the
cationic Pd(II) species and both O- and S-bound dmso
complexes of cationic Pd(II) are reported.29 The added
phen is presumably perturbed by some interaction with
resulting coordinatively unsaturated species.
This phenomenon can be explained either by (i) re-
versible dissociation of the phen ligand, (ii) rapid and re-
versible reductive elimination between the acetato and
3,4-dimethyl phthalyl groups,27 (iii) reversible dissocia-
tion of the acetato ligand, or (iv) twist-rotation via
pseudotetrahedral transition state.28 We conducted the
Table 1. Selected Bond Distances of Pd Complexes 1b,
1c and 1e (Å).
1ba
1c
1e
2.002(3)
2.018(3)
---
2.123(3)
2.034(3)
1.984(4)
2.023(3)
---
2.127(3)
2.072(3)
---
Pd(1)
-
-
N(1)
N(2)
Pd(1)
In relation to this fact, Itami, Studer and co-workers
proposed a similar dissociation of the acetato ligand from
Pd(1)-C(4)
---
---
Pd(1)
Pd(1)
Pd(1)
Pd(1)
-
-
-
-
O(5)
C(1)
O(1)
O(3)
---
1.992(3)
---
+
2.017(3)
1.999(3)
---
CO2Me
---
---
N
AcO-
aThe bond distances of 1b was taken from ref. 26.
Pd
CO2Me
(2)
1c
N
dmso-d6
dmso-d6
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1
2
NaOAc
3
4
1c
1d
X
NaOAc
5
6
7
8
30 ˚C
90 ˚C
(i)
(h)
(g)
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80 ˚C
C(1)
N(2)
70 ˚C
60 ˚C
(f)
Pd(1)
N(1)
(e)
(d)
(c)
I(1)
50 ˚C
40 ˚C
Figure 3. Molecular structure of [PdI{C6H3(CO2Me)2-
2,3}(phen)] (1e) by X-ray with selected numbering
schemes. All hydrogen atoms are omitted for clarity.
Ellipsoids represent 50% probability.
(b)
(a)
30 ˚C
30 ˚C
and side views of a merged structures of 1c and 1d. Inter-
estingly, these optimized structures show high coinci-
dence among the acetato, phen and the ipso carbons in the
dimethylphthalyl groups. Their major differences can be
found in the deviation of the planes between the square
plane constituted by the Pd center and the benzene-ring in
dimethylphthalyl group [118.7˚ (1c) and 81.1˚ (1d)]. We
will discuss about these optimized structures in the sec-
tion of XAFS studies.
2.0
1.6
2.0
1.6
ppm
ppm
1
Figure 2. Variable temperature H NMR spectra of
[Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] (1c) (left) and
[Pd(OAc){C6H3(CO2Me)2-2,3}(phen)] (1d) (right) in
the region of the acetato groups (400 MHz, dmso-d6).
(a): before addition of NaOAc, (b)-(i): after addition of
´
1 equiv of NaOAc. indicates an impurity.
Other
Compounds.
Preparation
of
[Pd(OAc)2(phen)] (1b) from commercially available 1a
was well-established,24,32 and the molecular structure of
1b by X-ray analysis was also reported.26 We made single
crystals of 1b for this study according to literature
method.26 We also prepared [Cu(OAc)2(phen)] (2b).33
Although the molecular structure of 2b by X-ray has been
already reported,34 we independently solved the molecu-
lar structure of 2b.
[Pd(Ar)(OAc)(bpy)] in the C4-selective arylation of thio-
phenes.30 Yu and co-workers also suggested dissociation
of the acetato ligand from [PdX(OAc)(phen)].31 The pre-
sent observation may also support these proposals.
In the case of 1d, although broadening of the acetato
ligand and added NaOAc resonances were observed in the
range 50-90 ˚C in 1H NMR (Figure 2, right), no trend of
coalescence was observed. Note that no broadening of the
added phen resonances was observed for 1d. Probably, 1d
also releases the acetato group at high temperature but the
event is much slower than 1c.
The target product 4 was obtained by the dehydro-
genative coupling of dimethyl phthalate (3) and the mo-
lecular structure of 4 was unequivocally determined by
X-ray structure analysis (Figure 5). This molecule has the
2-fold axis in the molecule, suggesting a very symmetric
structure and the C-C bond length between the aryl
groups is 1.491(3) Å. The dihedral angle between two
biaryl planes are -0.2(3)˚, suggesting to be a planar mol-
ecule.
Attempts to make single crystals of 1d failed but we
obtained
single
crystals
of
the
precursor
[PdI{C6H3(CO2Me)2-2,3}(phen)] (1e) suitable for X-ray
structure analysis. The molecular structure of 1e by X-ray
is depicted in Figure 3.
Stoichiometric Reactions of Dimethylphtha-
lylpalladium(II) Complexes. Because preparation and
isolation of 1c from 1a or 1b was difficult, the reverse
We also performed the DFT calculations to obtain the
optimized structures of 1c and 1d. Figure 4 shows the top
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1
2
3
4
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8
CO2Me
CO2Me
N
N
AcOH
Pd
O
O
100 ˚C, 30 min
1c (3,4-phtharyl)
1d (2,3-phtharyl)
CO2Me
CO2Me
9
[Pd(OAc)2(phen)] +
(3)
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1b
3
98% from 1c
96% from 1d
78% from 1c
87% from 1d
Pyrolysis of 1c at 180 ˚C resulted in the formation of
4 in 60% (30%/Pd) yield, suggesting disproportionation
reaction of 1c under these conditions (eq 4). When 1d was
treated under the same conditions, however, no coupling
product was observed at all and small amount of dimethyl
phthalate (3) was observed in 10% yield. Pyrolysis in the
presence of both 1c and 1d produced a mixture of 4 (21%)
and 5 (4%), and 6 was not observed at all (eq 5). Dimethyl
phthalate (3) was also not observed in this reaction. These
results suggest one of the possible pathways to give 4 and
5 to be a disproportionation reaction of 1c, and
transmetallation between 1c with 1d. In addition, the pre-
sent result also suggests that disproportionation reaction
of 1d does not occur.
Figure 4. Top and side views of a merged structure of 1c
and 1d optimized by the DFT calculations.
CO2Me
N
CO2Me
Pd
dimethyl adipate
180 ˚C, 1 h
N
O
O
1c (3,4-phtharyl)
1d (2,3-phtharyl)
MeO2C
CO2Me
CO2Me
CO2Me
+
MeO2C
MeO2C
MeO2C
MeO2C
4
5
not detected (from 1c and 1d)
60% yield (30% yield/Pd) (from 1c)
not detected (from 1d)
Figure 5. Molecular structure of tetramethyl 3,3’4,4’-bi-
phenyltetracarcboxylate (4). All hydrogen atoms are
omitted for clarity. Ellipsoids represent 50% probabil-
ity.
MeO2C
CO2Me
CO2Me
+
+
(4)
CO2Me
reaction, formation of 1b from 1c, was conducted. Treat-
ment of 1c with acetic acid at 100 ˚C for 30 min produced
1b and dimethyl phthalate (3) in 98% and 78% yields, re-
spectively (eq. 3).
46
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60
MeO2C
CO2Me
6
3
not detected (from 1c)
10% (from 1d)
not detected (from 1c and 1d)
A similar treatment of 1d with acetic acid also pro-
duced 1b (96%) and 3 (87%). According to the view of
microscopic reversibility, these backward reactions make
the connection between 1b and 1c or 1d. A related study
As discussed above, the variable temperature NMR
suggests that 1c reversibly dissociates the acetato anion at
elevated temperature. Osakada and co-workers docu-
mented the disproportionation reaction of PdIArL (L =
tmeda, bpy, Me2bpy) to proceed from a cationic
[PdArL2]+ complex giving a biaryl.36 They noted strong
concerning
microscopic
reversibility
between
[Hg(O2CR)2] and [Hg(O2CR)Ph] has been documented.35
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(5)
4
+
5
+
6
1c
+
1d
1
2
dimethyl adipate
180 ˚C, 1 h
(pin)B
CO2Me
CO2Me
21%
4%
0%
CO2Me
CO2Me
3
4
5
6
7
8
9
total yield 25% (12.5% / Pd) by NMR
Ag2O
CD2Cl2,
r.t., 13-25 d
MeO2C
MeO2C
4/5 = 86/14
4
dependence of the reaction on the solvent used, and ace-
tone was the best solvent for disproportionation reaction.
43% (X = Br)
53% (X = OAc)
[PdX{C6H3(CO2Me)2}(phen)]
(pin)B
When
we
conducted
the
reaction
of
CO2Et
CO2Et
[PdBr{C6H3(CO2Me)2-3,4}(phen)] with AgBF4 in ace-
tone, however, no biaryl product was observed. After
screening of the solvents, we found the reaction in dime-
thyl phthalate (3) produced 4 in 62% yield (eq 6). The
reaction also produced 4 in CH2Cl2, although the yield
was not particularly high (21%). Note that neither of the
regioisomers 5 nor 6 were observed in these reactions.
These reactions, and pyrolysis of 1c, suggest formation of
4 by the disproportionation reaction/reductive elimination
at Pd(II) species.
CO2Me
Ag2O
EtO2C
EtO2C
CO2Me
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
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51
52
53
54
55
56
57
58
59
60
1,2-dichloroethane
50 ˚C, 7 d
7
42% (X = OAc)
along with 4 in 2%
Scheme
3.
Transmetallations
of
PdX{C6H3(CO2Me)2-3,4}(phen)] (X = Br, OAc)
with dialkyl 4-(pinacolboryl)phthalate.
(0.1 MPa) at 200 ˚C for 6 h as the standard set of condi-
tions (Table 2). The catalyst system involving [Pd(OAc)2]
(1a: 0.065 mol %)/[Cu(OAc)2×H2O] (2a×H2O: 0.020
mol %)/[phen×H2O] (0.065 mol %) produced the biaryls
in 8.5% yield (4/5 = 90/10) with 64 TONs (entry 1), which
was almost consistent with the reported catalysis (eq. 1).2
The reaction was completely shut-down in the absence of
phen (entry 3). Without use of copper co-catalyst, the
product yield was significantly diminished (entry 4).
[Cu(OAc)2(phen)×0.5H2O] (2b×0.5H2O), [Cu(acac)2] (2c)
and [Cu(OAc)] (2d) were found to be promising co-cata-
lysts (entries 4-6). Although Mitsudome, Kaneda and co-
workers documented the Cu-free Wacker reaction of elec-
tron-deficient internal alkenes,38 the present reaction did
not work well in the absence of a Cu complex (entry 7).
[Pd(OAc)2(phen)] (1b) also showed similar catalytic
properties (entries 8-13).
AgBF4
[PdBr{C6H3(CO2Me)2-3,4}(phen)]
(6)
4
r.t.
0% by NMR in acetone
62% by NMR in 3 (1 day)
21% by NMR in CH2Cl2 (4 days)
In order to generate a putative [Pd{C6H3(CO2Me)2-
3,4}2(phen)], reactions of [PdX{C6H3(CO2Me)2-
3,4}(phen)] (X = Br, OAc) with dimethyl 4-(pinacol-
boryl)phthalate were conducted. According to a similar
reaction reported by Osakada and co-workers,37 Ag2O
would promote this transmetallation. However, present
reactions were very sluggish even in the presence of
Ag2O, and complex mixtures involving 4 were obtained
(4: 43-53 % yield) (Scheme 3). The transmetallation
product [Pd{C6H3(CO2Me)2-3,4}2(phen)] was not ob-
served during the reactions. A similar treatment of
[Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] (1c) with diethyl
4-(pinacolboryl)phthalate gave 7 in 42% yield along with
trace amount of 4 (2%). These experiments suggest the in
situ formation of diarylpalladium(II) species by the
transmetallation to release 4 or 7 by the reductive elimi-
nation. By taking into account all these stoichiometric re-
actions, the present formation of 4 is consistent with the
disproportionation reaction of 1c followed by reductive
elimination from a bis(3,4-dimethyl phthalyl)palla-
dium(II) species. Osakada and co-workers proposed dis-
proportionation of cationic [PdAr(solvent)(bpy)]+ via a
dinuclear dicationic Pd species [(bpy)ArPd(µ2-
Ar)Pd(bpy)(solvent)]2+,36 and such dinuclear dicationic
species may also play a key role in the present reaction.
When [Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] (1c)
was used as the catalyst, the catalytic activity was im-
proved to give the biaryls in 11.7% (with 2b, entry 15)
and 12.0% yield (with 2c, entry 18). However, addition of
an excess phen×H2O to this system also discouraged the
reaction (entry 19). The reaction was also catalyzed by
[Pd(OAc){C6H3(CO2Me)2-2,3}(phen)] (1d) (entries 21-
22). This catalysis never ever proceeded in the absence of
a Pd catalyst (entries 23-25).
The time-course curve for the dehydrogenative cou-
pling of 3 catalyzed by 1b/2b×0.5H2O at 200 ˚C under air
showed an induction period and the biaryls yield plat-
eaued around 6 h (Figure 6). However, when a combina-
tion of 1b/2a was used as the catalyst, no induction period
was observed with comparable yield under the same con-
ditions. One of the possible explanations for this phenom-
enon is that [Cu(OAc)2×H2O] (2a) shows higher activity
than [Cu(OAc)2(phen)] (2b). Note that coordination of
phen is indispensable for [Pd(OAc)2] (1a) as shown in en-
try 3 in Table 2.
Catalytic Dehydrogenative Coupling of Dimethyl
Phthalate. Catalytic dehydrogenative couplings of di-
methyl phthalate (3) were screened under the conditions
of Pd catalyst (4.00 mM), 1,10-phenanthroline·H2O (4.00
mM), Cu co-catalyst (1.20 mM) in 3 (25 mL) under air
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Table 2. Catalytic Dehydrogenative Coupling of Dime-
thyl Phthalate. a
8
6
4
Pd cat. (0.0653 mol %)
1,10-phenanthroline H2O (0.0653 mol %)
Cu cat. (0.0196 mol %)
CO2Me
CO2Me
air, 200 ˚C, 6 h
3
8
MeO2C
CO2Me
CO2Me
CO2Me
9
2
0
+
MeO2C
MeO2C
MeO2C
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MeO2C
5
4
0
1
2
3
4
5
6
time/h
entry Pd cat. Cu cat.
yield/% 4/5
TONb conv./%
90/10 64 18.3
×
Figure 6. Time-yield curves for 1b/2b 0.5H2O (1b =
0.0634 mol %, 2b 0.5H2O = 0.0190 mol %) (open circles)
and for 1b/2a×0.5H2O (1b = 0.0635 mol %, 2a 0.5H2O =
0.0173 mol %) (closed circles) at 200 ˚C under air in 3 (25
mL).
1
2c
3d
1a
1a
1a
1a
1a
1a
1a
1b
1b
1b
1b
1b
1b
1c
1c
1c
1c
1c
1c
1c
1d
1d
2a·H2O
2a·H2O
2a·H2O
8.5
8.1
0.0
×
92/8 62
15.9
3.4
×
0
89/11 53
94/6 73
94/6 83
94/6 14
89/11 48
91/9 55
91/9 47
94/6 73
93/7 28
4
2b·0.5H2O 7.0
16.6
16.0
14.2
6.2
5
2c
9.6
10.9
1.9
6.3
7.2
6
2d
studied by the XAFS analysis. We used a synchrotron ra-
diation at SPring-8 BL01B1 beamline.39 First of all we
compared the XAFS spectra of 1b in the crystalline solid-
phase in a BN pellet40 with the solution-phase in dimethyl
phthalate (3).
7
8d
9e
none
2a·H2O
2a·H2O
15.9
15.7
12.9
15.4
10.8
5.9
10d
11ef
12f
13d,
14d
15e
16d
17e
18e
19 f
20d
21e
22d
23d
24d
25
2b·0.5H2O 6.2
As shown in Figure 7, 1b in 3 shows almost identical
Pd K-edge (24.357 keV) XANES (X-ray absorption near
edge structure) spectra, suggesting the Pd valency and
basic geometry in a solution to be identical with the crys-
tal structure.
2c
9.6
3.7
0.8
6.2
11.7
2c
none
2a·H2O
2a·H2O
92/8
6
92/8 47
93/7 89
92/8 75
94/6 67
94/6 91
93/7 31
93/7 17
94/6 73
94/6 64
0
15.2
15.4
13.5
9.8
Figure 8 shows the Pd K-edge solution-phase EXAFS
(extended X-ray absorption fine structure) spectra of a
mixture of 1a and 2b in 3.
2b·0.5H2O 9.7
2b·0.5H2O 8.7
2c
12.0
4.1
2.3
9.6
12.7
10.8
6.4
2c
none
2a·H2O
13.1
12.1
0.9
2b·0.5H2O 8.3
none 2a·H2O 0.0
none 2b·0.5H2O 0.0
none none 0.0
0
2.1
0
0.5
aStandard conditions: [Pd] = 4.00 mM (0.065 mol %), [2a×H2O] = 1.20 mM
(0.020 mol%), [phen·H2O] = 4.00 mM (0.065 mol %), 3: 25 mL. Air = 0.1
MPa, temp = 200 ˚C, time = 6 h. bTONs: turn over numbers. c[phen·H2O] =
5.20 mM. dwithout addition of PHEN. e[phen·H2O] = 1.20 mM. f[phen·H2O]
= 5.20 mM.
In summary of this section, all Pd complexes 1a-d cat-
alyzed the dehydrogenative coupling of dimethyl
phthalate.
Figure 7. The Pd K-edge XANES spectra of 1b in solid-
phase in BN pellet (black line) and solution-phase in 3
(red dotted line).
Solid- and Solution-Phase XAFS Studies. The cat-
alyst solution for the dehydrogenative arene coupling was
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Figure 8. The Pd K-edge solution-phase EXAFS of
×
1a/2b 0.5H2O in 3 (black), 1a (blue) and 1b (red) in 3
as the reference. The green circles in the k-space graph
point major unconformities between 1a (black) and 1b
(red).
Figure 9. The Pd K-edge solution-phase EXAFS spectra
×
after addition of phen H2O to a solution of 1a and
×
2b 0.5H2O in 3 (black), 1a (blue) and 1b (red) as the ref-
erence. The green circles in the k-space graph high-
lighted conformities between 1a (black) and 1b (red).
The green circles in the k-space graph point major un-
conformities of the 1a/2b (black line) and 1b (red line).
These data suggest that spontaneous migration of the
phen ligand in 2b to 1a would insufficiently occur at room
temperature.
XAFS. The catalysis gave the biaryl products in 3.3%
(4/5 = 95/5) suggesting 4 TONs by GLC analysis. Figure
10 shows the changes in the EXAFS before and after the
reaction at 200 ˚C catalyzed by 1a/2b×0.5H2O /phen×H2O .
Similar catalyses for dehydrogenative coupling of 3 by
1c/2b×0.5H2O/phen×H2O and 1d/2b×0.5H2O/phen×H2O at
200 ˚C for 1 h produced the biaryls in 4.1% (4/5 = 94/6)
with 5 TONs, and 2.1% (4/5 = 88/12) with 3 TONs, re-
spectively (Figures 11 and 12). According to these
EXAFS spectra (Figures 10-12), an almost identical Pd
species was formed regardless of the starting Pd com-
plexes 1a, 1c and 1d. In fact, the merged EXAFS spectra
of the catalytic solution starting from 1a, 1c and 1d over-
lapped each other both in the k- and R-spaces (Figure 13).
Notably no significant change was observed after the ca-
talysis in the EXAFS spectra of 1c and 1d. The TONs for
Addition of phen×H2O to the solution of 1a/2b in 3
caused significant change in the solution-phase EXAFS
spectrum and the resulting spectrum almost completely
overlapped with 1b (Figure 9). Accordingly, we have suc-
ceeded to confirm coordination of phen to 1a and for-
mation of 1b by EXAFS.
Next, we have conducted the dehydrogenative cou-
pling reaction of 3 catalyzed by 1a/2b×0.5H2O/phen×H2O
at 200 ˚C for 1 h under the atmosphere of oxygen (0.1
MPa), and measured the solution-phase XAFS of the cat-
alytic solution to know the changes of the Pd species. In
order to obtain sufficient Pd K-edge XAFS data, we per-
formed the reaction under the higher catalyst concentra-
tions [1a (25 mM), 2b×0.5H2O (7.5 mM), phen×H2O (25
mM)] than the standard set of conditions. We stopped the
catalysis after 1 h in order to observe the catalysis by
the
1c/2b×0.5H2O/phen×H2O
and
1d/2b×0.5H2O/phen×H2O systems suggest that the catalyst
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Figure 11. The Pd K-edge solution-phase EXAFS spec-
Figure 10. The Pd K-edge solution-phase EXAFS spec-
×
×
tra of 1c/2b 0.5H2O/phen H2O (red dotted line) before
×
×
tra of 1a/2b 0.5H2O/phen H2O before (red dotted line)
and after (black line) catalysis.
and after (black line) the catalysis.
XANES, the isosbestic point would suggest these constit-
uents being mixed in different amount in the catalyst so-
lution.41
averagely goes through 5 and 3 catalytic cycles, respec-
tively. Nevertheless, a slight difference was observed be-
tween them on the EXAFS peaks after the catalysis.
Given the low reactivity of 1d in the stoichiometric reac-
tion, a certain amount of 1d might remain unreacted after
the catalysis in the 1d/2b×0.5H2O/phen×H2O system.
For further considerations of these EXAFS spectra of
the intermediate or resting state, we calculated the
EXAFS spectra by the FEFF program42 based on the op-
timized structures of 1c and 1d obtained by the DFT cal-
culations. As shown in Figure 4, the optimized structures
of 1c and 1d are very close to each other, and the differ-
ences between 1c and 1d for the bond distances of the
Pd-C, Pd-N and Pd-O in the primary coordination
sphere are only within 0.01 Å. Since resolution of the
atomic distances by EXAFS is around 0.1 Å, the differ-
ence between 1c and 1d appears in the second coordina-
tion sphere and beyond. Figures 15 and 16 show the solu-
tion-phase EXAFS spectra of 1c and 1d and their FEFF
calculation fits based on the optimized structures obtained
by the DFT calculations (Figure 4).
Figure 14 shows the merged XANES spectra of after
the catalyses in 3 catalyzed by 1a/2b×0.5H2O/phen×H2O,
and
1c/2b×0.5H2O/phen×H2O,
and
1d/2b×0.5H2O/phen×H2O. These spectra clearly show the
valency of the new species derived from 1a in the cataly-
sis is a divalent, which shows almost the same spectrum
as 1c and 1d. Furthermore, an isosbestic point is found in
these normalized XANES spectra at 24.341 keV. An isos-
bestic point generally shows transformation between two
species either by the extent of reaction or the position of
the equilibrium. However, given the resolution of
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Figure 13. The solution-phase EXAFS spectra after ca-
×
×
talyses in 3 starting from 1a/2b 0.5H2O/phen H2O
Figure 12. The Pd K-edge solution-phase EXAFS spec-
Figure 14. The Pd K-edge normalized solution-phase
×
×
(black), 1c/2b 0.5H2O/phen H2O (red dotted line) and
×
×
tra of 1d/2b 0.5H2O/phen H2O before (red dotted line)
×
×
1d/2b 0.5H2O/phen H2O (blue dotted line).
×
×
XANES spectra of 1a/2b 0.5H2O/phen H2O in 3 (green),
and after (black line )catalysis.
×
×
after the catalysis by 1a/2b 0.5H2O/phen H2O in 3
(black), 1c (red) and 1d in 3 (blue). The dotted line shows
a Pd foil. Spectra around edge jump region and spectra
and 1d, also suggests the [Pd(OAc)(dimethyl phtha-
lyl)(phen)] structure basically remained intact. Therefore,
we can conclude that [Pd(OAc)(dimethyl phtha-
lyl)(phen)] species is surely produced from 1a or 1b dur-
ing the catalysis.
The R-factors for 1c and 1d are 0.0124 and 0.0137,
respectively. These data suggest the intermediate or rest-
ing state after the catalysis also contains the acetato,
phthalyl, and the phen ligand. However, the solution-
phase EXAFS spectrum of the Pd species after the catal-
ysis has a slight difference from 1c or 1d in the third co-
ordination sphere and beyond. One of the possibilities is
the presence of a Cu complex in the far side from the Pd
center. In fact, Hosokawa, Murahashi and co-workers
suggested formulation of Pd-Cu dinuclear species in the
Wacker-type reactions,43 and they obtained crystals of
[(dmf)4Cl2Cu-(PdCl2)2]n in the [PdCl2]/[CuCl]/O2 cata-
lyzed Wacker reaction in DMF.44 However, we remain
this issue for further study because we do not have any
evidence for this point so far. An important conclusion
achieved in the part of the EXAFS study is that a same
species is eventually formulated regardless of the starting
Pd catalysts 1a, 1c and 1d as an intermediate or resting
state. The fact that no significant change has been ob-
served in the EXAFS spectrum after the catalysis for 1c
Consistent Catalytic Cycle. These stoichiometric
and catalytic reactions, and the XAFS data provide useful
mechanistic insights and the catalytic cycle shown in
Scheme 4 is consistent with all experimental data. The
added PHEN immediately coordinates to [Pd(OAc)2] (1a)
to give [Pd(OAc)2(phen)] (1b), which is confirmed by the
EXAFS experiment. Then, heating of 1b in dimethyl
phthalate (3) produces 1c and 1d probably either by C-H
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Figure 15. Solution-phase EXAFS spectra of 1c (red)
and the FEFF-calculated fits based on the optimized
structures obtained by the DFT calculations (blue).
The FEFF fitting area is shown in the gray box.
Figure 14. The Pd K-edge normalized solution-phase
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×
×
XANES spectra of 1a/2b 0.5H2O/phen H2O in 3 (green),
×
×
after the catalysis by 1a/2b 0.5H2O/phen H2O in 3
(black), 1c (red) and 1d in 3 (blue). The dotted line shows
a Pd foil. Spectra around edge jump region and spectra
around the isosbestic point (bottom).
Figure 16. Solution-phase EXAFS spectra of 1d (red)
and the FEFF-calculated fits based on the optimized
structures obtained by the DFT calculations (blue).
The FEFF fitting area is shown in the gray box.
bond activation through the IES mechanism3 or electro-
philic aromatic substitution. The reverse reactions, aci-
dolyses of 1c and 1d with AcOH to 1b, may connect
among them. Although the second C-H bond activation
of the coming 3 cannot be ruled out, present results show
the presence of disproportionation of 1c to give 1b and 1f,
and subsequent reductive elimination releases 4. Note that
as can be seen in the stoichiometric reactions, a diarylpal-
ladium(II) species is not stable and is prone to carry on
subsequent reductive elimination. The reversible libera-
tion of the acetato anion from 1c may be responsible to
this disproportionation. The oxidation of resulting 1g oc-
curs by 2a to regenerates 1b. On the other hand, reaction
of 1b with 3 also produces the regioisomer 1d. While the
disproportionation between 1c and 1d produces 5, no dis-
proportionation occurs between 1d complexes. Because
the present catalysis involves 1b, 1c and 1d according to
the XAFS analyses, 1c and 1d would be regarded as an
active intermediate and resting state, respectively. The
rate-determining step would be the disproportionation re-
action.
■ CONCLUDING REMARKS
We elucidated the detailed mechanism for the dehy-
drogenative coupling of dimethyl phthalate catalyzed by
[Pd(OAc)2]/[Cu(OAc)2]/phen system. The present catal-
ysis involves [Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] (1c)
and [Pd(OAc){C6H3(CO2Me)2-2,3}(phen)] (1d), where
disproportionation of 1c is a consistent pathway to give
tetramethyl 3,3’4,4’-biphenyltetracarcboxylate (4). The
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on a Shimadzu GC-14B or GC2014 with FID detector
CO2Me
1
2
3
4
5
6
7
8
equipped with InertCap 1 column (0.25 mm i.d. x 30 m).
The GC-MS analyses were performed on a Shimadzu
QP2010 with use of TC-1 column (0.25 mm i.d. x 30 m).
A stoichiometric transmetallation was performed with a
personal organic synthesizer EYELA ChemiStation
PPM-5512. The ESI TOF-MS analysis was performed on
a Bruker micrOTOF. The UV-vis analysis was performed
on a Shimadzu MultiSpec 1500 with a photo-diode-alley
detector. The catalyses were carried out with use of an
EYELA SynFlex aluminum block heater system.
MeO2C
LPd
AcOH
OAc
dimethyl
phthalate
3
2 AcOH
+
0.5 O2
1d
2 Cu(OAc)
dimethyl
phthalate
3
OAc
LPd
H2O
OAc
AcOH
CO2Me
CO2Me
2 Cu(OAc)2
2a
1b
9
CO2Me
CO2Me
10
11
12
13
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LPd
LPd
1g
OAc
1c
[PdBr{C6H3(CO2Me)2-3,4}(tmeda)]. Under a nitro-
gen atmosphere, [Pd(dba)2] (2.8766 g, 5.0028 mmol)
were placed in a Schlenk tube (250 mL), to which ben-
zene (70 mL), tmeda (750 µL, 5.10 mmol) and dimethyl
4-bromophthalate (950 µL, 5.25 mmol) were added by a
syringe or hypodermic syringe. The reaction mixture was
warmed at 50 ˚C for 38.5 h to give a grayish green solid.
After removal of the solution, the solid was washed with
benzene (150 mL) to give [PdBr(C6H3(CO2Me)2-
3,4)(tmeda)] in 70% yield (1.72345 g, 3.4767 mmol).
This compound was characterized by 1H NMR. 1H NMR
(400 MHz, CD2Cl2, r.t.): d 2.39 (s, 6H, NMe), 2.56 (t, 3JH-
H = 5.4 Hz, 2H, NC2H4N), 2.62 (s, 6H, NMe), 2.73 (t,3JH-
H = 5.4 Hz, 2H, NC2H4N), 3.79 (s, 3H, CO2Me), 3.82 (s,
3H, CO2Me), 7.33 (d, 3JH-H = 8.0 Hz, 1H, 6-CH), 7.50 (dd,
3JH-H = 8.0 Hz, 4JH-H = 1.7 Hz, 1H, 5-CH), 7.58 (d, 4JH-H
= 1.7 Hz, 1H, 3-CH). 13C{1H} NMR (100.5 MHz, CD2Cl2,
r.t.): d 48.79 (s, tmeda), 50.96 (s, tmeda), 52.38 (s,
CO2Me), 52.53 (s, CO2Me), 58.67 (s, tmeda), 63.04 (s,
tmeda), 125.81 (s), 126.37 (s), 130.26 (s), 135.04 (s),
138.33 (s), 157.28 (s), 168.50 (s, CO2Me), 169.47 (s,
CO2Me).
LPd
CO2Me
OAc
1c
CO2Me
MeO2C
MeO2C
OAc
LPd
CO2Me
LPd
OAc
1b
CO2Me
CO2Me
1f
CO2Me
4
L = 1,10-phenanthroline
Scheme 4. A Proposed Catalytic Cycle for Dehydro-
genative Coupling of Dimethyl Phthalate catalyzed
by [Pd(OAc)2]/[Cu(OAc)2]/phen.
present solution-phase EXAFS data clearly suggests for-
mation of 1c and 1d as intermediates or resting states in
the catalysis. The mechanistic insights in copper cycle
and possibility to form a Pd-Cu dinuclear species are fur-
ther field to be solved.
■ EXPERIMENTAL SECTION
General Procedures. All procedures described in
this paper were carried out under atmosphere except
noted. Dimethyl phthalate (3), dimethyl adipate, and di-
chloromethane were used as received from commercial
suppliers. Benzene, Et2O and tetrahydrofuran (thf) were
taken from a Glass Contour Ultimate Solvent Systems.
1,2-dichloroethane was used as received. Dmso-d6 was
dried over activated molecular sieves 4A and dichloro-
methane-d2 and chloroform-d1 were used as received.
[Pd(OAc)2] (1a), [Cu(OAc)2·H2O] (2a×H2O), 1,10-phe-
nanthroline·H2O, and tmeda were used as received.
[PdBr{C6H3(CO2Me)2-3,4}(phen)].
[PdBr(C6H3-
(CO2Me)2-3,4)(tmeda)] (247.89 mg, 0.50007 mmol) and
1,10-phehtanthroline·H2O (93.18 mg, 0.5168 mmol) were
dissolved in thf (20 mL) and the reaction mixture was
stirred at room temperature for 24 h to give a white pre-
cipitate. After removal of the solution, the white residue
was washed with acetone and hexane. Removal of vola-
tile matters gave white powder of [PdBr{C6H3(CO2Me)2-
1
3,4}(phen)] in 89% yield (250.1 mg, 0.4468 mmol). H
NMR (400 MHz, CD2Cl2, r.t.): d 3.84 (s, 3H, CO2Me),
3.85 (s, 3H, CO2Me), 7.50 (d, 3JH-H = 7.9 Hz, 1H, 3-CH),
[Pd(OAc)2(phen)]24
(1b),
[Pd(dba)2]45
and
7.67 (dd, 3JH-H = 8.2, 5.2 Hz, 1H, phen), 7.72 (dd, 3JH-H
=
[Cu(OAc)2(phen)·0.5H2O]33 (2b×0.5H2O) were prepared
according to literature methods. Dimethyl 4-bromoph-
thalate,46 dimethyl 3-iodophthalate,47 dimethyl 4-(pina-
8.0 Hz, 4JH-H = 1.4 Hz, 1H, 2-CH), 7.79 (d, 4JH-H = 1.4 Hz,
1H, 6-CH), 7.92 (dd, 3JH-H = 8.2, 4.9 Hz, 1H, phen), 7.99
(AB, 3JH-H = 8.9 Hz, 1H, phen), 8.03 (AB, 3JH-H = 8.9 Hz,
1H, phen), 8.08 (dd, 3JH-H = 5.2 Hz, 4JH-H = 1.4 Hz, 1H,
phen), 8.45-8.63 (m, 2H, phen), 9.58 (dd, 3JH-H = 4.9 Hz,
4JH-H = 1.6 Hz, 1H, phen). 13C{1H} NMR (100.5 MHz,
CD2Cl2, r.t.): d 52.51 (s, CO2Me), 52.62 (s, CO2Me),
125.90 (s), 126.48 (s), 127.14 (s), 127.26 (s), 127.88 (s),
130.08 (s), 130.47 (s), 130.95 (s), 138.45 (s), 138.61 (s),
138.72 (s), 145.39 (s), 147.44 (s), 150.94 (s), 151.00 (s),
157.13 (s), 168.53 (s, CO2Me), 169.49 (s, CO2Me).
colboryl)phthalate48
and
diethyl
4-pinacol-
boryl)phthalate48 were prepared according to the modifi-
cation of literature methods . H and 13C NMR spectra
1
1
were recorded on a JEOL ECX-400P (400 MHz for H).
Chemical shifts (d) are given in ppm, relative to TMS. All
coupling constants are given in Hz. Elemental analyses
were carried out on a Perkin-Elmer 2400 series II CHN
analyzer. IR spectra were recorded on JASCO FT/IR-
4100 with use of KBr disks. GLC analyses was performed
12
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1
ACS Catalysis
7.58 (dd, 3JH-H = 8.2, 5.2 Hz, 1H, phen), 7.61 (d, 3JH-H
=
[Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] (1c). In a 50
8.9 Hz, 1H, 3- or 5-CH), 7.89 (dd, 3JH-H = 8.2, 4.9 Hz, 1H,
mL round bottom flask, above solid (279.90 mg, 0.50008
mmol as [PdBr(C6H3(CO2Me)2-3,4)(phen)]) was reacted
with AgOAc (166.26 mg, 0.99611 mmol) in dichloro-
methane (20 mL) for 2.5 h at room temperature in the dark.
A brown solid deposited from the reaction system. The
insoluble solid was filtered off and the solution was evap-
orated to give a pale yellow solid, which was recrystal-
lized from dichloromethane/hexane to give 1c as pale yel-
low crystals in 50% yield (135.1 mg, 0.2515 mmol). 1H
NMR (400 MHz, CD2Cl2, 20.9 ˚C): d 2.02 (s, 3H, OAc),
3.84 (s, 3H, 3H, CO2Me), 3.85 (s, 3H, CO2Me), 7.48 (d,
3JH-H = 7.9 Hz, 1H, 5-CH), 7.62 (dd, 3JH-H = 8.2, 5.2 Hz,
1H, phen), 7.82 (dd, 3JH-H = 7.9 Hz,4JH-H = 1.4 Hz, 1H, 6-
CH), 7.86 (d, 4JH-H = 1.4 Hz, 1H, 2-CH), 7.91 (dd, 3JH-H
= 7.9, 5.2 Hz, 1H, phen), 7.98 (AB, 3JH-H = 13.6 Hz, 1H,
phen), 7.95 (AB, 3JH-H = 8.9 Hz, 1H, phen), 8.00 (AB, 3JH-
2
3
4
5
6
7
8
9
= 8.9 Hz, 1H, phen), 8.04 (dd, 3JH-H = 7.6 Hz, JH-H
=
4
H
1.1 Hz, 5- or 3-CH), 8.15 (dd, 3JH-H = 5.3 Hz, 4JH-H = 1.4
Hz, 1H, phen), 8.49 (dd, 3JH-H = 8.2 Hz, JH-H = 1.4 Hz,
4
1H, phen), 8.55 (dd, 3JH-H = 8.3 Hz, 4JH-H = 1.4 Hz, 1H,
phen), 8.77 (dd, 3JH-H = 4.9 Hz, 4JH-H = 1.4 Hz, 1H, phen).
13C{1H} NMR (100.5 MHz, CD2Cl2, r.t.): d 23.64 (s,
OAc), 52.27 (s, CO2Me), 52.47 (s, CO2Me), 125.26 (s),
125.65 (s), 127.24 (s), 127.49 (s), 128.07 (s), 129.98 (s),
130.18 (s), 138.33 (s), 128.40 (s), 139.91 (s), 141.03 (s),
145.14 (s), 147.75 (s), 149.59 (s), 151.23 (s), 153.28 (s),
167.63 (s, CO2Me), 171.66 (s, CO2Me), 177.34 (s, OAc).
Anal. Calcd for C24H20N2O6Pd·0.23CH2Cl2: C, 52.50; H,
3.74; N, 5.20. Found: C, 52.14; H, 3.59; N, 5.14. Note that
including of 0.23 equiv of CH2Cl2 was confirmed by 1H
NMR.
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11
12
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3
phen), 8.02 (AB, JH-H = 13.6 Hz, 1H, phen), 8.26 (dd,
3JH-H = 5.2 Hz, 4JH-H = 1.4 Hz, 1H, phen), 8.53 (dd, 3JH-H
3
= 8.3 Hz, 4JH-H = 1.4 Hz, 1H, phen), 8.55 (dd, JH-H
=
8.3Hz,4JH-H = 1.6 Hz, 1H, phen), 8.80 (dd, 3JH-H = 4.9 Hz,
4JH-H = 1.4 Hz, 1H, phen). 13C{1H} NMR (100.5 MHz,
CD2Cl2, 21.7 ˚C): d 23.78 (s, OAc), 52.50 (s, CO2Me),
52.61 (s, CO2Me), 125.65 (s, C6H3), 125.80 (s, C6H3),
126.73 (s, C6H3), 126.79 (s, C6H3), 127.73 (s, C6H3),
130.03 (s, phen), 130.41 (s, phen), 130.66 (s, phen),
134.83 (s, phen), 135.49 (s, phen), 138.59 (s, phen),
144.94 (s, phen), 147.91 (s, phen), 149.56 (s, phen),
152.44 (s, phen), 149.85 (s, phen), 168.71 (s, CO2Me),
169.59 (s, CO2Me), 177.34 (s, OAc). Anal. Calcd for
C24H20N2O6Pd: C, 53.50; H, 3.74; N, 5.20. Found: C,
53.93; H, 4.16; N, 5.43.
[PdI{C6H3(CO2Me)2-2,3}(phen)] (1e). Treatment of
[Pd(dba)2] (996.0 mg, 1.403 mmol) with dimethyl 3-
iodophthalate (640.4 mg, 2.001 mmol) and 1,10-phehtan-
throline·H2O (327.4 mg, 1.817 mmol) in benzene (20 mL)
at 50 ˚C for 4 h gave yellow powder of 1e in 78% yield
(663.2 mg, 1.093 mmol). This compound was character-
1
1
ized with H NMR and X-ray analysis (vide infra). H
NMR (400 MHz, CD2Cl2, r.t.): δ 3.65 (s, 3H, CO2Me),
3.85 (s, 3H, CO2Me), 7.19 (t, 3JH-H = 7.7 Hz, 1H, 5-CH),
7.56 (dd, 3JH-H = 7.6 Hz, 4JH-H = 1.1 Hz, 1H, 4- or 6-CH),
7.69 (dd, 3JH-H = 8.2, 5.2 Hz, 1H, phen), 7.83 (dd, 3JH-H
7.7 Hz, 4JH-H = 1.1 Hz, 1H, 6- or 4-CH), 7.87 (dd, 3JH-H
8.2, 4.9 Hz, 1H, phen), 7.90 (dd, 3JH-H = 5.2 Hz, 4JH-H
=
=
=
1.4 Hz, 1H, phen), 7.98 (AB, 3JH-H = 8.9 Hz, 1H, phen),
8.01 (AB, 3JH-H = 8.9 Hz, 1H, phen), 8.52 (dd, 3JH-H = 2.8
Hz, JH-H = 1.5 Hz, 1H, phen), 8.54 (dd, 3JH-H = 2.9 Hz,
4
4JH-H = 1.4 Hz, 1H, phen), 9.83 (dd, 3JH-H = 4.9 Hz, 4JH-H
= 1.5 Hz, 1H, phen).
[Pd(OAc){C6H3(CO2Me)2-2,3}(phen)] (1d). Treat-
ment of 1e (663.2 mg, 1.093 mmol) with AgOAc (184.1
mg, 1.103 mmol) for 4 h at room temperature in dichloro-
methane (70 mL) gave pale yellow powder of 1d in 91%
1
yield (536.4 mg, 0.9955 mmol). H NMR (400 MHz,
CD2Cl2, r.t.): d 2.01 (s, 3H, OAc), 3.65 (s, 3H, CO2Me),
3.85 (s, 3H, CO2Me), 7.21 (t, 3JH-H = 7.6 Hz, 1H, 4-CH),
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Page 14 of 19
triphenylmethane (2.53 mg) was added as an internal
to give 4 in 53% yield. [PdI{C6H3(CO2Me)2-2,3}(phen)]
standard. The 1H NMR spectrum suggested formation of
(1e): 1e (6.11 mg, 0.0101 mmol) reacted with dimethyl 4-
(pinacolboryl)phthalate (3.22 mg, 0.0101 mmol) and
Ag2O (4.78 mg, 0.0206 mmol) in CD2Cl2 at room tem-
perature for 10 days but 5 was not observed. A similar
treatment of 1c (5.39 mg, 0.0100 mmol) with diethyl (4-
pinacolboryl)phthalate (3.55 mg, 0.0102 mmol) and
Ag2O (4.66 mg, 0.0201 mmol) in 1,2-dichloroethane at
50 ˚C for 7 days produced 3,4-diethyl-3’,4’-dimethyl
3,3’,4,4’-biphenyltetracarboxylate (7) in 42% along with
small amount of 4 in 2%. In this reaction, because reso-
nances of 7 heavily overlapped with reactants in 1H NMR
and pure 7 was not available, we postulated the relative
intensity for 7 in GLC analysis to be the same as 4 based
on biphenyl as an internal standard. Formation of 7 was
also confirmed with the GC-MS analysis.
1
2
3
4
5
6
7
8
4 in 60% yield (0.01508 mmol).
Pyrolysis of [Pd(OAc){C6H3(CO2Me)2-2,3}(phen)]
(1d). Similar to the procedure in 4-6-1, treatment of 1d
(27.97 mg, 0.05005 mmol), dimethyl adipate (0.7 mL) at
180 ˚C for 8 h produced only dimethyl phthalate (3) in
10.2% and no formation of 4, 5, or tetramethyl 2,2’,3,3’-
biphenyltetracarboxylate (6) was observed.
9
Pyrolysis
[Pd(OAc){C6H3(CO2Me)2-3,4}(phen)]
in
the
presence
(1c)
of
and
10
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[Pd(OAc){C6H3(CO2Me)2-2,3}(phen)] (1d). A solution
of dimethyl adipate (1.0 mL) of 1c (13.48 mg, 0.02502
mmol) and 1d (13.48 mg, 0.02502 mmol) was heated at
180 ˚C for 8 h. Then, triphenylmethane (2.49 mg) was
added to the solution as an internal standard. After dilu-
tion of the reaction mixture with thf, the GLC analysis
suggested total yield of 4 and 5: 25.0%, 4/5 ratio: 86/14,
yield of 3: 11.8%. Formation of tetramethyl 2,2’,3,3’-bi-
phenyltetracarboxylate was not observed.
Catalytic Dehydrogenative Coupling of Dimethyl
Phthalate. Typical catalysis was carried out as follows:
On a four-necked round bottle flask, a reflux condenser,
gas inlet, thermometer and a stopper were installed. Then,
[Pd(OAc)2] (1a) (22.46 mg, 0.1000 mmol),
[Cu(OAc)2×H2O] (2a×H2O) (5.45 mg, 0.0300 mmol),
phen×H2O (19.82 mg, 0.09998 mmol), and dimethyl
phthalate (3) (25.0 mL, 157.8 mmol) were added to the
flask. Air stream was passed through the solution by use
of a mini-compressor and the reaction system was heated
at 200 ˚C for 6 h with magnetic stirring at the rate of 460
rpm. The products were estimated by an internal standard
method using triphenylmethane, GLC analysis showed
total yield of 4 and 5 in 9.7%, TON: 75, 4/5 ratio: 94/6,
conversion: 12.0% and yield of methyl benzoate: 0.1%.
Treatment of [PdBr{C6H3(CO2Me)2-3,4}(phen)]
with AgBF4. In acetone: [PdBr{C6H3(CO2Me)2-
3,4}(phen)] (55.99 mg, 0.1000 mmol) was treated with
AgBF4 (46.35 mg, 0.2381 mmol) in the presence of bi-
phenyl (15.47 mg, 0.1003 mmol) as an internal standard
in acetone (5 mL) at room temperature for 24 h in the dark.
The GLC analysis showed no formation of 4 and 5. In
dichloromethane:
A
similar
treatment
of
[PdBr{C6H3(CO2Me)2-3,4}(phen)] (55.98 mg, 0.1000
mmol) with AgBF4 (46.04 mg, 0.2365 mmol) in dichloro-
methane at room temperature for 4 days gave 4 in 21%
yield (0.0106 mmol). Compound 5 was not observed at
all.
Time-course Curves for the Dehydrogenative
Coupling of 3 Catalyzed by 1b/2b and 1b/2a. 1b/2b:
In a four-necked round bottom flask, 1b (40.44 mg,
0.1001 mmol) and 2b×0.5H2O (10.84 mg, 0.02996 mmol)
were added in 3 (25.0 mL, 157.8 mmol). Air stream was
passed through the solution and the system was heated at
200 ˚C at the stirring rate of 460 rpm. When the tempera-
ture reached at 200 ˚C, we set the start time for the catal-
ysis and the progress of the catalysis was monitored the
reaction for every 1 h by GLC. Finally, triphenylmethane
(24.31 mg) as an internal standard and THF were added
to the solution. 1b/2a×H2O: 1b (40.47 mg, 0.1002 mmol),
2a×H2O (5.43 mg, 0.0273 mmol) in 3 (25.0 mL, 157.8
mmol) at 200 ˚C for 6 h. The reaction was monitored for
every 1 h by GLC.
Treatment of [PdI{C6H3(CO2Me)2-2,3}(phen)] (1e)
with AgBF4. Complex 1e (24.27 mg, 0.04000 mmol) was
treated with AgBF4 (25.9 mg, 0.133 mmol) and biphenyl
(10.04 mg, 0.06511 mmol) as an internal standard in 3 (2
mL) at room temperature for 24 h. No formation of 4, 5
or 6 was observed.
Reactions of [PdX{C6H3(CO2Me)2}(phen)] with Di-
alkyl
4-(pinacolboryl)phthalate.
[PdBr{C6H3(CO2Me)2-3,4}(phen)]:
[PdBr{C6H3(CO2Me)2-3,4}(phen)] (5.70 mg, 0.0102
mmol), dimethyl 4-(pinacolboryl)phthalate (3.54 mg,
0.0111 mmol) and Ag2O (4.84 mg, 0.0209 mmol) were
placed in an NMR tube, to which CD2Cl2 was introduced.
After 13 days at room temperature, I2 (8.12 mg, 0.0320
mmol) was added to the reaction mixture. Based on dime-
thyl sulfone as an internal standard (1.03 mg, 0.0109
mmol), the yield of 4 was estimated to be 43% by GLC.
Solid and Solution-Phase XAFS Measurements.
Pd K-edge (24.357 keV) XANES and EXAFS measure-
ments were carried out at the BL01B1 beamline at
SPring-8 of the Japan Synchrotron Radiation Research
Institute (JASRI). The measurements were performed at
room temperature. A Si(311) two-crystal monochromater
was used. The Pd K-edge XAFS data were collected by
the transmission mode. The X-ray energy was calibrated
using a Pd-foil, and the data analysis was performed with
Athena in Demeter software package for Windows (ver.
Compound
5
was
not
observed
at
all.
[Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] (1c): 1c (5.91 mg,
0.0110 mmol) reacted with dimethyl 4-(pinacol-
boryl)phthalate (3.42 mg, 0.0108 mg) and Ag2O (4.84 mg,
0.0209 mmol) in CD2Cl2 at room temperature for 25 days
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ACS Catalysis
0.9.25).42 The BN pellets (ca. 0.5 mm thickness) were
prepared for the solid-phase XAFS by mixing the Pd
complex with commercial BN powder for dilution. For
solution-phase XAFS, the catalyst solution in dimethyl
phthalate (3) as a solvent were filtrated through a PTFE
membrane filter with a 0.2 µm pore size.
Catalyses for XAFS Studies. (Entry 1) [Pd(OAc)2]
(1a) (25 mM), [Cu(OAc)2(phen)×0.5H2O] ([2b×0.5H2O]
(7.5 mM) and [phen×H2O] (25 mM) in dimethyl phthalate
(3) at 200˚C for 1 h under oxygen. Total yield of 4 and 5:
3.3%, TON: 4, 4/5 ratio: 95/5. Conversion: 7.5%, Yield
NMR
data
of
new
complexes
1
2
3
4
5
6
7
8
[PdBr{C6H3(CO2Me)2-3,4}(tmeda)],
[PdBr{C6H3(CO2Me)2-3,4}(phen)], 1c, 1d, 1e, vari-
able temperature NMR data for 1c and 1d, GLC and
GC-MS charts for the reaction of 1c with diethyl 4-
(pinacolboryl)phthalate, Cartesian coordinates for
1c and 1d by DFT calculations, and FEFF parame-
ters for 1c and 1d (PDF)
Accession Codes
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
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40
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42
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45
46
47
48
49
50
51
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53
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55
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60
CCDC 1813927-1813928 and 1813930 contain the sup-
plementary crystallographic data for this paper. These
data can be obtained free of charge via
www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax:+44 1223 336033.
of
methyl
benzoate:
0.6%.
(Entry
2)
[Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] (1c) (25 mM),
[2b×0.5H2O] (7.5 mM) in dimethyl phthalate at 200 ˚C for
1 h under oxygen. Total yield of 4 and 5: 4.1%. TON: 5.
4/5 ratio: 94/6. Conversion: 8.5%. Yield of methyl benzo-
ate: 0.4 %. (Entry 3) [Pd(OAc){C6H3(CO2Me)2-
2,3}(phen)] (1d) (25 mM), [2b×0.5H2O] (7.5 mM) in di-
methyl phthalate at 200 ˚C for 1 h under oxygen. Total
yield of 4 and 5: 2.1%. TON: 3. 4/5 ratio: 88/12. Conver-
sion: 7.9%. Yield of methyl benzoate: 0.5%.
■ AUTHOR INFORMATION
Corresponding Authors
*E-mail for M.H.: hrc@cc.tuat.ac.jp.
*E-mail for T.M.: mitsudom@cheng.es.osaka-u.ac.jp.
*E-mail for H.T.: takaya@scl.kyoto-u.ac.jp.
DFT Calculations of 1c and 1d. The density func-
tional theory (DFT) calculations were employed with
B3LYP. The basis set was consisted of the Stuttgarte
Dresden SDD effective core potential basis set on the Pd
atom and the 6-31G(d) basis sets on all other atoms. Ef-
fect of methyl benzoate as a solvent was included in the
calculations by using the Polarizable Continuum Model
(PCM).
ORCID
Masafumi Hirano: 0000-0001-7835-1044
Nobuyuki Komine: 0000-0003-1744-695X
Zen Maeno: 0000-0002-9300-219X
Hikaru Takaya:0000-0003-4688-7842
Present Address
FEFF Fitting Analysis for EXAFS. The fitting calcu-
lations were performed on FEFF6 program embedded
with Artemis software,42 where the theoretical scattering
paths were generated from the DFT calculations of 1c and
1d.
§Institute for Catalysis, Hokkaido University, N-21,
W-10, Sapporo 001-0021, Japan.
Notes
Single Crystal X-ray Structure Analyses. Single
crystals of 1b, 1c, 1e, 2b and 4 were selected by a polar-
ized optical microscope. The selected crystals suitable for
single crystal X-ray structure analysis were mounted on
the top of a glass capillary with use of Paraton N® oil. A
Rigaku AFC-7R Mercury II diffractometer with graphite-
monochromated Mo Ka radiation (l = 0.71075 Å) was
used for data collection at 200 K. The collected data were
solved by direct methods and refined by a full-matrix
least-squares procedure using the CrystalStructure pro-
gram (ver. 4.2).49,50 All hydrogen atoms were treated as a
riding model. The POV-Ray program (ver. 3.6.2) was
used for depiction of the molecules.51 CCDC 1813927,
1813928, and 1813930 contain the supplementary crys-
tallographic data for 1c, 1e and 4, respectively.
The Authors declare no competing financial interest.
Author Contributions
The manuscript was written through contributions of all
authors.
Funding Sources
Grant-in-Aid for Scientific Research on Innovative Ar-
eas, “3D Active-Site Science”26105003.
■ ACKNOWLEDGMENT
We are grateful to Dr. Sayori Kiyota for elemental
analyses. We thank Dr. Tetsuo Honma at JASRI for facil-
itation in SPring-8. M.H also thank Prof. Kotohiro
Nomura at Tokyo Metropolitan University for fruitful dis-
cussion. This study was financially supported by Grant-
in-Aid for Scientific Research on Innovative Areas, “3D
■ ASSOCIATED CONTENT
Supporting Information
Active-Site Science”26105003.
The Supporting Information is available free of charge on
the ACS Publications website at DOI: 10.1021/xxxxxx.
15
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Page 16 of 19
Catalyzed Aerobic Oxidative Coupling of Arenes: Evidence for
■ ABBREVIATIONS
Transmetalation between Two Pd(II)-Aryl Intermediates. J. Am.
Chem. Soc. 2014, 136, 9914-9917. (c) Wang, D.; Stahl, S. S. Pd-
Catalyzed Aerobic Oxidative Biaryl Coupling: Non-Redox Co-
catalysis by Cu(OTf)2 and Discovery of Fe(OTf)3 as a Highly Ef-
fective Cocatalyst. J. Am. Chem. Soc. 2017, 139, 5704-5707. (d)
Wang, D.; Weinstein, A. B.; White, P. B.; Stahl, S. S. Ligand-
Promoted Palladium-catalyzed Aerobic Oxidation Reactions.
Chem. Rev. 2018, 118, 2636-2679.
1
2
3
4
5
6
bpy: 2,2’-bipyridine (C10H8N2). cod: cyclooctadiene
(C8H12). dba: dibenzylidene acetone (C17H14O). phen:
1,10-phenanthroline (C12H8N2). pin: pinacolyl (C6H12O2).
tmeda: tetramethylethylenediamine (C6H16N2). TON
(turn over number).
7
8
9
(11) Stults, B. R.; Friedman, R. M.; Koenig, K.; Knowles, W.; Greegor,
R. B.; Lytle, F. W. Homogeneous Asymmetric Catalysis: Struc-
tural Studies of Catalytic Intermediates using Extended X-ray Ab-
sorption Fine Structure. J. Am. Chem. Soc. 1981, 103, 3235-3237.
(12) Ti: Blanco-brieva, G.; Capel-sanchez, M. C.; Campos-martin, J.
M.; Ferro, J. L. G.; Lede, E. J.; Adrini, L.; Requejo, F. G. Titanium
K-edge XANES Analysis to Unravel the Local Structure of Al-
kene Epoxidation Titanium-Polysiloxane Homogeneous Cata-
lysts. Adv. Synth. Catal. 2003, 345, 1314-1320.
(13) V: (a) Nomura, K.; Mitsudome, T.; Igarashi, A.; Nagai, G.; Tsu-
tsumi, K.; Ina, T.; Omiya, T.; Takaya, H.; Yamazoe, S. Synthesis
of (Adamantylimido)vanadium(V) Dimethyl Complex Contain-
ing (2-Anilidomethyl)pyridine Ligand and Selected Reactions:
Exploring the Oxidation State of the Catalytically Active Species
in Ethylene Dimerization. Organometallics 2017, 36, 530-542.
(b) Nomura, K.; Oshima, M.; Mitsudome, T.; Harakawa, H.; Hao,
P.; Tsutsumi, K.; Nagai, G.; Ina, T.; Takaya, H.; Sun, W.-H.;
Yamazoe, S. Synthesis of Structural Analysis of (Imido)vanadium
Dichloride Complexes Containing 2-(2’-Benz-imidazoyl)pyri-
dine Ligands: Effect of Al Cocatalyst for Efficient Ethylene
(Co)polymerization. ACS Omega, 2017, 2, 8660-8673.
(14) Cr: Moulin, J. O.; Evans, J.; McGuinness, D. S.; Reid, G.; Ruck-
lidge, A. J.; Tooze, R. P.; Tromp, M. Probing the Effects of Lig-
and Structure on Activity and Selectivity of Cr(III) Complexes for
Ethylene Oligomerization and Polymerization. Dalton Trans.
2008, 1177-1127.
(15) Mo: Bartlett, S. A.; Wells, P. P.; Nachtegaal, M.; Dent, A. J.; Ci-
bin, G.; Reid, G.; Evans, J.; Tromp, M. Insights in the Mechanism
of Selective Olefin Oligomerization Catalysis using Stopped-
Flow Freeze-Quench Techniques: A Mo K-edge QEXAFS Study.
J. Catal. 2011, 284, 247-258.
■ REFERENCES AND NOTE
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(1) Itatani, H.; Yoshimoto, H. Palladium-catalyzed Synthesis of Aro-
matic Coupling Compounds. Chem. Ind. 1971, 674-675.
(2) Shiotani, A.; Itatani, H.; Inagaki, T. Selective Coupling of Dime-
thyl Phthalate with Palladium Catalysts at Atmospheric Pressure.
J. Mol. Catal. 1986, 34, 57-66.
(3) This mechanism is also called as the concerted metalation-depro-
tonation (CMD) mechanism or the ambiphilic metal-ligand acti-
vation (AMLA).
(4) (a) Biswas, B.; Sugimoto, M.; Sakaki, S. C-H Bond Activation of
Benzene and Methane by M(h2-O2CH)2 (M = Pd or Pt). A Theo-
retical Study. Organometallics 2000, 19, 3895-3908. (b) Moritani,
I.; Fujiwara, Y. Aromatic Substitution of Styrene-Palladium
Chloride Complex. Tetrahedron Lett. 1967, 8, 1119-1122. (c) Da-
vies, D. L.; Donald, S. M. A.; Macgregor, S. A. Computational
Study of the Mechanism of Cyclometalation by Palladium Ace-
tate. J. Am. Chem. Soc. 2005, 127, 13754-13755.
(5) (a) Davies, D. L.; Donald, S. M. A.; Al-Duaij, O.; Macgregor, S.
A.; Pölleth, M. Electrophilic C-H Activation at Cp*Ir: Ancillary-
Ligand Control of the Mechanism of C-H Activation. J. Am.
Chem. Soc. 2006, 128, 4210-4211. (b) Boutadla, Y.; Davies, D.
L.; Macgregor, S. A.; Poblador-Bahamonde, A. I. Mechanisms of
C-H Bond Activation: Rich Synergy between Computation and
Experiment. Dalton Trans. 2009, 5820-5831. (c) Boutadla, Y.;
Davies, D. L.; Macgregor, S. A.; Poblador-Bahamonde, A. I.
Computational and Synthetic Studies on the Cyclometalation Re-
action of Dimethylbenzylamine with [IrCl2Cp*]2: Role of the
Chelating Base. Dalton Trans. 2009, 5887-5893.
(6) Oxgaard, J.; Tenn III, W. J.; Nielsen, R. J.; Periana, R. A.; God-
dard III, W. A. Mechanistic Analysis of Iridium Heteroatom C-H
Activation: Evidence for an Internal Electrophilic Substitution
Mechanism. Organometallics 2007, 26, 1565-1567. (b) Ess, D.
H.; Nielsen, R. J.; Goddard III, W. A.; Periana, R. A. Transition-
State Charge Transfer Reveals Electrophilic, Ambiphilic, and Nu-
cleophilic Carbon-Hydrogen Bond Activation. J. Am. Chem. Soc.
2009, 131, 11686-11688.
(7) (a) Laponte, D.; Fagnou, K. Overview of the Mechanistic Work
on the Concerted Metallation-Deprotonation Pathway. Chem. Lett.
2010, 39, 1118-1126. (b) Gorelsky, S. I. Reactivity and Regiose-
lectivity of Palladium-catalyzed Direct Arylation in Noncoorper-
ative and Cooperative Processes. Organometallics 2012, 31,
4631-4634. (c) Raybov, A. D. Mechanisms of Intramolecular Ac-
tivation of Carbon-Hydrogen Bonds in Transition-Metal Com-
plexes. Chem. Rev. 1990, 90, 403-424.
(8) Tan, Y.; Barrios-Landeros, F.; Hartwig, J. F. Mechanistic Studies
on Direct Arylation of Pyridine N-Oxide: Evidence for Coopera-
tive Catalysis between Two Distinct Palladium Centers. J. Am.
Chem. Soc. 2012, 134, 3683-3686.
(9) (a) Wakioka, M.; Nakamura, Y.; Hihara, Y.; Ozawa, F.; Sakaki,
S. Factors Controlling the Reactivity of Heteroarenes in Direct
Arylation with Arylpalladium Acetate Complexes. Organometal-
lics 2013, 32, 4423-4430. (b) Wakioka, M.; Nakamura, Y.; Wang,
Q.; Ozawa, F. Direct Arylation of 2-Methylthiophene with Iso-
lated [PdAr(µ-O2CR)(PPh3)]n Complexes: Kinetics and Mecha-
nism. Organometallics 2012, 31, 4810-4816.
(16) Mn: Feth, M. P.; Bolm, C.; Hildebrand, J. P.; Köhler, M.; Beck-
mann, O.; Bauer, M.; Ramamonjisoa, R.; Bertagnolli, H. Struc-
tural Investivation of High-valent Manganese-Salene Complexes
by UV/Vis, Raman, XANES, and EXAFS Spectroscopy. Chem.
Eur. J. 2003, 9, 1348-1359.
(17) Fe: (a) Bauer, M.; Gastl, C. X-Ray Absorption in Homogeneous
Catalysis Research: The Iron-Catalyzed Michael Addition Reac-
tion by XAS, RIXS and Multi-Dimensional Spectroscopy. Phys.
Chem. Chem. Phys. 2010, 12, 5575-5584. (b) Schoch, R.; Desens,
W.; Werner, T.; Bauer, M. X-Ray Spectroscopic Verification of
the Active Species in Iron-Catalyzed Cross-Coupling Reactions.
Chem. Eur. J. 2013, 19, 15816-15821. (c) Takaya, H.; Nakajima,
S.; Nakagawa, N.; Isozaki, K.; Iwamoto, T.; Imayoshi, R.; Gower,
N. J.; Adak, L.; Hatakeyama, T.; Honma, T.; Takagaki, M.;
Sunada, Y.; Nagashima, H.; Hashizume, D.; Takahashi, O.; Naka-
mura, M. Inverstigation of Organoiron Catalysis in Kumada-
Tamao-Corrium-Type Cross-Coupling Reaction Assisted by So-
lution-Phase X-ray Absorption Spectroscopy. Bull. Chem. Soc.
Jpn. 2015, 88, 410-418.
(18) Ru: Rohr, M.; Grunwaldt, J.-D.; Baiker, A. Formylation with Su-
percritical Carbon Dioxide over Ru/Al2O3 Modified by Phos-
phines: Heterogeneous or Homogeneous Catalysis?. J. Catal.
2005, 229, 144-153.
(19) Ni: (a) Asakura, H.; Shishido, T.; Tanaka, T. In Situ Time-Re-
solved XAFS Study of the Reaction Mechanism of Bromoben-
zene Homocoupling Mediated by [Ni(cod)(bpy)]. J. Phys. Chem.
A 2012, 116, 4029-4034. (b) Andrews, P.; Corker, J. M.; Evans,
J.; Webster, M. Highly Active Homogenous Nickel Catalysts for
Alkene Dimerization: Crystal Structure of [Ni(h3-C3H5)(PPh3)Br]
and In Situ Characterization of AlEt3-Activated [Ni(h3-
C3H3)(PPh3)Br] by Nuclear Magnetic Resonance and Extended
(10) (a) Izawa Y.; Stahl, S. S. Aerobic Oxidative Coupling of o-Xy-
lene: Discovery of 2-Fluoropyridine as a Ligand to Support Se-
lective Pd-catalyzed C-H Functionalization. Adv. Synth. Catal.
2010, 352, 3223-3229. (b) Wang, D.; Izawa, Y.; Stahl, S. S. Pd-
16
ACS Paragon Plus Environment

Page 17 of 19
1
ACS Catalysis
X-ray Absorption Fine Structure Spectroscopy. J. Chem. Soc.,
Dalton Trans. 1994, 1337-1347.
(28) (a) Obora, Y.; Tsuji, Y.; Nishiyama, K.; ebihara, M.; Kawamura,
T. Structure and Fluxional Behavior of cis-Bis(stannyl)bis(phos-
phine)platinum: Oxidative Addition of Organodistannane to Plat-
inum(0) Complex. J. Am. Chem. Soc. 1996, 118, 10922-10923.
(b) Tsuji, Y.; Nishiyama, K.; Hori, S.; Ebihara, M.; Kawamura, T.
Structure and Facile Unimolecular Twist-Rotation of cis-Bis(si-
(20) Pd: (a) Tromp, M.; van Bokhoven, J. A.; van Haaren, R. J.; van
Strijdonck, G. P. F.; van der Eerden, A. M. J.; van Leeuwen, P.
W. N. M.; Koningsberger, D. C. Structure-Performance Relations
in Homogeneous Pd Catalysis by In Situ EXAFS Spectroscopy. J.
Am. Chem. Soc. 2002, 124, 14814-14815. (b) Miyoshi, Y.;
Akatsuka, T.; Okuoka, S.; Tsukajima, A.; Makino, M.; Saito, M.;
Yonehara, K. Palladium-Catalyzed Aerobic Intermolecular Cy-
clization of Acrylic Acid with 1-Octene to Afford a-Methylene-
g-butyrolactones: The Remarkable Effect of Continuous Water
Removal from the Reaction Mixture and Analysis of Reaction by
Kinetic, ESI-MS, and XAFS Measurements. Chem. Eur. J. 2012,
18, 7941-7949.
2
3
4
5
6
7
8
9
lyl)bis(phosphine)platinum
and
cis-Bis(stannyl))bis(phos-
phine)palladium Complexes. Organometallics 1998 17, 507-512.
(c) Ozawa, F.; Kamite, J. Mechanistic Study on the Insertion of
Phenylacetylene into cis-Bis(silyl)platinum(II) Complexes. Or-
ganometallics 1998, 17, 5630-5639.
(29) (a) Calligaris, M.; Carugo, O. Structure and Bonding in Metal Sul-
foxide Complexes. Coord. Chem. Rev. 1996, 153, 83-154. (b)
Diao, T.; White, P.; Guzei, I.; Stahl, S. S. Characterization of
DMSO Coordination to Palladium(II) in Solution and Insights
into the Aerobic Oxidation Catalyst, Pd(DMSO)2(TFA)2. Inorg.
Chem. 2012, 51, 11898-11909.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(21) Au: (a) Hashmi, A. S. K.; Lothschuetz, C.; Ackermann, M.;
Doepp, R.; Anantharaman, S.; Marchetti, B.; Bertagnolli, H.;
Rominger, F. Gold Catalysis: In Situ EXAFS Study of Homoge-
nous Oxidative Esterification. Chem. Eur. J. 2010, 16, 8012-8019.
(b) Nguyen, B. N.; Adrio, L. A. Barreiro, E. M.; Brazier, J. B.;
Haycock, P.; Hii, K. K.; Nachtegaal, M.; Newton, M. A.;
Szlachetko, J. Deconvolution of the Mechanism of Homogenous
Gold-Catalyzed Reactions. Organometallics 2012, 31, 2395-2402.
(22) Cu: (a) He, C.; Zhang, G.; Ke, J.; Zhang, H.; Miller, J. T.; Kropf,
A. J.; Lei, A. Labile Cu(I) Catalyst/Spectator Cu(II) Species in
Copper-Catalyzed C-C Coupling Reaction: Operando IR, In Situ
XANES/EXAFS Evidence and Kinetic Investigations. J. Am.
Chem. Soc. 2013, 135, 488-493. (b) Walroth, R. C.; Uebler, J. W.
H.; Lancaster, K. M. Probing CuI in Homogenous Catalysis using
High-Energy-Resolution Fluorescence-Detected X-Ray Absorp-
tion Spectroscopy. Chem. Commun. 2015, 51, 9864-9867.
(23) (a) Nelson, R. C.; Miller, J. T. An Introduction to X-Ray Absorp-
tion Spectroscropy and Its In Situ Application to Organometallic
Compounds and Homogeneous Catalysts. Catal. Sci. Tech. 2012,
2, 461-470. (b) Stherborne, G. J.; Nguyen, B. N. Recent XAS
Studies into Homogeneous Metal Catalyst in Fine Chemical and
Pharmaceutical Syntheses. Chem. Cent. J. 2015, 9, 1-6. (c) Evans,
T. Tilden Lecture: Shining Light on Metal Catalysts. Chem. Soc.
Rev.1997, 11-19.
(30) Kirchberg, S.; Tani, S.; Ueda, K.; Yamaguchi, J.; Studer, A.; Itami,
K. Oxidative Biaryl Coupling of Thiophenes and Thiazoles with
Arylboronic Acids through Palladium Catalysis: Otherwise Diffi-
cult C4-Selective C-H Arylation Enabled by Boronic Acids. An-
gew. Chem. Int. Ed. 2011, 50, 2387-2391.
(31) Ye, M.; Gao, G.-L.; Yu, J.-Q. Ligand-Promoted C-3 Selective C-
H Olefination of Pyridines with Pd Catalysts. J. Am. Chem. Soc.
2011, 133, 6964-6967.
(32) (a) Halligudi, S. B.; Khan, N. H.; Kureshy, R. I.; Suresh, E.; Ven-
katsubramanian, K. Synthesis, Structural Characterization and
Catalytic Carbonylation of Nitrobenzene to Phenylurethane using
Palladium(II) 1,10-Phenanthroline Diacetato Complex. J. Mol.
Catal. A, 1997, 124, 147-154. (b) Ragaini, F.; Gasperini, M.;
Cenini, S.; Arnera, L.; Caselli, A.; Macchi, P.; Casati, N. Mecha-
nistic Study of the Palladium-phenanthroline Catalyzed Car-
bonylation of Nitroarenes and Amines: Palladium-Carbonyl Inter-
mediates and Bifunctional Effects. Chem. Eur. J. 2009, 15, 8064-
8077.
(33) Devereux, M.; O’Shea, D.; O’Connor, M.; Grehan, H.; Connor,
G.; McCann, M.; Rosair, G.; Lyng, F.; Kellett, A.; Walsh, M.;
Egan, D.; Thati, B. Synthesis, Catalase, Superoxide Dismutase
and Antitumor Activities of Copper(II) Carboxylate Complexes
Incorporating Benzimidazole, 1,10-Phenanthroline and Bipyri-
dine Ligands: X-ray Crystal Structures of [Cu(BZA)2(bpy)(H2O)[,
[Cu(SalH)2(BZDH)2] and [Cu(CH3COO)2(5,6-DMBZDH)2]. Pol-
yhedron 2007, 26, 4073-4084.
(34) Barquín, M.; González Garmendia, M. J.; Larrínaga, L.; Pinilla,
E.; Torres, M. R. Complexes of Cu2(µ-OAc)4(H2O)2 with 1,10-
Phenathroline and Comparison with Those of 2,2’-Bipyridne.
Crystal Structure of the Dimer [Cu(OAc)2(phen)](µ-H2O). Z.
Anorg. Allg. Chem. 2005, 631, 2151-2155.
(35) (a) Kresge, A.; Brennan, J. Perchloric Acid Catalyzed Aromatic
Mercuration in Acetic Acid Solution. II. The Substitution Process.
J. Org. Chem. 1967, 32, 752-755. (b) Fung, C. W.; Khorramdel-
Vahed, M.; Ranson, R. J.; Roberts, R. M. G. Kinetics and Mech-
anism of Mercuation of Aromatic Compounds by Merury Tri-
fluoroacetate in Trifluoroacetic Acid. J. Chem. Soc. Perkin Trans
2 1980, 267-272.
(36) Yagyu, T.; Hamada, M.; Osakada, K.; Yamamoto, T. Cationic Ar-
ylpalladium Complexes with Chelating Diamine Ligands,
[PdAr(N-N)(solv)]BF4 (N-N = N,N,N’,N’-tetramethylethylenedi-
amine, 2,2’-bipyridine, 4,4’-dimethyl-2,2’-bipyridine). Prepara-
tion, Intermolecular Coupling of the Aryl Ligands, and Insertion
of Alkyne and Allene into the Pd-C Bond. Organometallics 2001,
20, 1087-1101.
(24) (a) Wooley, M. J.; Khairallah, G. N.; Donnelly, P. S.; O’Hair, R.
A. J. Nitrogen Adduction by Three Coordinate Group 10 Organ-
ometallic Cations: Platinum is Favored over Nickel and Palladium.
Rapid Commun. Mass Spectrom. 2011, 25, 2083-2088. (b) Qian,
B.; Guo, S.; Shao, J.; Zhu, Q.; Yang, L.; Xia, C.; Huang, H. Pal-
ladium-Catalyzed Benzylic Addition of 2-Methyl Azaarenes to N-
Sulfonyl Aldimines via C-H Bond Activation. J. Am. Chem. Soc.
2010, 132, 3650-3651. (c) Hammer, C. F.; Heller, S. R.; Craig, J.
H. Reactions of b-Substituted Amines. II. Nucleophilic Displace-
ment Reactions on 3-Chloro-1-ethylpiperidine. Tetrahedron 1972,
28, 239-253.
(25) Markies, B. A.; Canty, A. J.; de Graaf, W.; Boersma, J.; Janssen,
M. D.; Hogerheide, M. P.; Smeets, W. J.; Spek, A. L.; van Koten,
G. Synthesis and Structural Studies of Phenyl(iodo)- and Me-
thyl(phenyl)palladium(II) Complexes of Bidentate Nitrogen Do-
nor Ligands. J. Organomet. Chem. 1994, 482, 191-199.
(26) Milani, B.; Alessio, E.; Mestroni, G.; Sommazzi, A.; Garbassi, F.;
Zangrando, E.; Bresciani-Pahor, N.; Randaccio, L. Synthesis and
Characterization of Monochelated Carboxylatopalladium(II)
Complexes with Nitrogen-Donor Chelating Ligands. Crystal
Structures of Diacetato(1,10-phenanthroline)- and Diacetato(2,9-
dimethyl-1,10-phenanthroline)-palldium(II). J. Chem. Soc., Dal-
ton Trans. 1994, 1903-1911.
(27) A related rapid and reversible reductive elimination between the
acetato and allyl at Pd(II) was reported: Yamamoto, T.; Akimoto,
M.; Saito O.; Yamamoto, A. Interaction of Palladium(0) Com-
plexes with Allylic Acetates, Allyl Ethers, Allyl Phenyl Chalco-
genides, Allylic Alcohols, and Allylamines. Oxidative Addition,
Condensation, Disproportionation, and p-Complex Formation.
Organometallics 1986, 5, 1559-1567.
(37) Osakada, K.; Onodera, H.; Nishihara, Y. Diarylpalladium Com-
plexes with a Cis Structure. Formation via Transmetalation of Ar-
ylboronic Acids with and Aryliodopalladium Complex and Intra-
molecular Coupling of the Aryl Ligands, Affording Unsymmet-
rical Biaryls. Organometallics 2005, 24, 190-192.
(38) (a) Mitsudome, T.; Yoshida, S.; Mizugaki, T.; Jitsukawa, K.;
Kaneda, K. Highly Atom-Efficient Oxidation of Electron-Defi-
17
ACS Paragon Plus Environment

ACS Catalysis
Page 18 of 19
cient Internal Olefins to Ketones Using a Palladium Catalyst. An-
Ishii, Y.; Bonnett, J. J.; Ibers, J. A. Chemistry of Dibenzyli-
gew. Chem. Int. Ed. 2013, 52, 5961-5964. (b) Mitsudome, T.; Yo-
shida, S.; Tsubomoto, Y.; Mizugaki, T.; Jitsukawa, K.; Kaneda,
K. Simple and Clean Synthesis of Ketones from Internal Olefins
Using PdCl2/N,N-Dimethylacetamide Catalyst System. Tetrahe-
dron Lett. 2013, 54, 1596-1598. (c) Mitsudome, T.; Mizumoto,
K.; Mizugaki, T.; Jitsukawa, K.; Kaneda, K. Wacker-Type Oxi-
dation of Internal Olefins Using a PdCl2/N,N-Dimethylacetamide
Catalyst System under Copper-Free Reaction Conditions. Angew.
Chem. Int. Ed. 2010, 49, 1238-1240. A concise review on Pd-cat-
alyzed aerobic oxidation reactions is reported. See ref. 10d.
(39) The Pd K-edge (24.357 keV) XAFS data were collected by trans-
mission mode under air and calibrated by using a Pd foil as a ref-
erence. For solution-phase XAFS of 1a and 1b, we used dimethyl
phthalate as the solvent and measured the solution after filtration
with a PTFE Milipore filter (pore size: 0.2 µm) by use of a cylin-
drical glass cell (10 mm i.d. x 100 mm) for JASCO polarimeter.
(40) Boron nitride (BN) is widely used to dilute a solid sample for XAS
study because BN is almost transparent to the synchrotron radia-
tion.
deneacetone-Palladium(0) Complexes. I. Novel Tris(dibenzyli-
deneacetone)dipalladium(solvent) Complexes and Their Reac-
tions with Quinones. J. Organomet. Chem. 1974, 65, 253-266.
Related papers are as follows: (c) Zalesskiy, S. S.; Ananikov, V.
P. Pd2(dba)3 as Precursor of Soluble Metal Complexes and Nano-
particles: Determination of Palladium Active Species for Cataly-
sis and Synthesis. Organometallics 2012, 31, 2302-2309. (d)
Kapdi, A. R.; Whitwood, A. C.; Williamson, D. C.; Lynam, J. M.;
Burns, M. J.; Williams, T. J.; Reay, A. J.; Holmes, J.; Fairlamb, I.
J. S. The Elusive Structure of Pd2(dba)3. Examination by Isotopic
Labeling, NMR Spectroscopy, and X-ray Diffraction Analysis:
Synthesis and Characterization of Pd2(dba-Z)3 Complexes. J. Am.
Chem. Soc. 2013, 135, 8388-8399.
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50
51
52
53
54
55
56
57
58
59
60
(46) Schulze, B. M.; Shewmon, N. T.; Zhang, J.; Watkins, D. L.;
Mudrick, J. P.; Cao, W.; Bou Zerdan, R.; Quaretarao, A. J.; Ghi-
viriga, I.; Xue, J.; Castellano, R. K. Consequences of Hydrogen
Bonding on Molecular Organization and Charge Transport in Mo-
lecular Organic Photovoltaic Materials. J. Mater. Chem. A 2014,
2, 1541-1549.
(47) (a) Feng, M.-L.; Li, Y.-F.; Zhu, H.-J.; Zhao, L.; Xi, B.-B.; Ni, J.-
P. Synthesis, Insecticidal Activity, and Structure-Activity Rela-
tionship of Trifluoromethyl-Containig Phthalic Acid Diamide
Structures. J. Agric. Food Chem. 2010, 58, 10999-11006. (b)
Ruchelman, A. L.; Muller, G. W.; Man, H.-W. JP5927241 B2,
2016.. (c) Hiraiwa, Y.; Ida, M.; Kudo, T.; Morinaka, A.;
Chikauchi, K.; Mori, K. Patent WO 2008016007 A1, 2008. (d)
van Antwerpen, P.; Prévost, M.; Zouaoui-Boudjeltia, K.; Babar,
S.; Legssyer, I.; Moreau, P.; Moguilevsky, N.; Vanhaeverbeek,
M.; Ducobu, J.; Nève, J.; Dufrasne, F. Conception of Myelop-
eroxidase Inhibitors Derived from Flufenamic Acid by Computa-
tional Docking and Structure Modification. Bioorg. Med. Chem.
2008, 16, 1702-1720.
(48) Roubinet, B.; Weber, M.; Shojaei, H.; Bates, M.; Bossi, M. L.;
Belov, V. N.; Irie, M.; Hell, S. W. Fluorescent Photoswitchable
Diarylethenes for Biolabeling and Single-Molecule Localization
Microscopies with Optical Superresolution. J. Am. Chem. Soc.
2017, 139, 6611-6620.
(49) CrystalStructure ver. 4.2; Rigaku Corporation, Tokyo, Japan,
2015.
(50) Sheldrick, G. SHELXL97; University of Göttingen, Germany,
1997.
(41) Calvin, S. XAFS for Everyone; CRC: Boca Raton, 2013; pp.224-
225.
(42) The fitting calculations were performed by FEFF6 program (revi-
sion 9.6.4) embedded with Artemis where the theoretical scatter-
ing paths were generated from the Cartesian coordinates based on
the DFT calculations of 1b and 1c depicted in Figure 4. FEFF9
program: Rehr, J. J.; Kas, J. J.; Vila, F. D.; Prange, M. P.; Jorissen,
K. Parameter-Free Calculations of X-ray Spectra with FEFF9.
Phys. Chem. Chem. Phys. 2010, 12, 5503-5513. Athena and Arte-
mis program: (a) Newville, M. IFEFFIT: Interactive XAFS Anal-
ysis and FEFF Fitting. J. Synchrotron Rad. 2001, 8, 322-324. (b)
Ravel, B.; Newville, M. ATHENA, ARTEMIS, HEPHAESTUS:
Data Analysis for X-Ray Absorption Spectroscopy using
IFEFFIT. J. Synchrotron Rad. 2005, 12, 537-541.
(43) Hosokawa, T.; Uno, T.; Inui, S.; Murahashi, S.-I. Palladium(II)-
Catalyzed Asymmetric Oxidative Cyclization of 2-Allylphenols
in the Presence of Copper(II) Acetate and Molecular Oxygen.
Study of the Catalysis of the Wacker-type Oxidation. J. Am. Chem.
Soc. 1981, 103, 2318-2323.
(44) Hosokawa, T.; Nomura, T.; Murahashi, S.-I. Palladium-Copper-
DMF Complexes Involved in the Oxidation of Alkenes. J. Organ-
omet. Chem. 1998, 551, 387-389.
(45) (a) Takahashi, T. Ito, S. Sakai, Y. Ishii, Novel Palladium(0) Com-
plex; Bis(dibenzylideneacetone)palladium(0). J. Chem. Soc., D;
Chem. Commun. 1970, 1065-1066. (b) Ukai, T.; Kawazura, H.;
(51) POV-Ray for Windows, ver. 3.6.2; Persistence of Vision Ray
Tracer Pty, Ltd.
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