C,N-palladacycles containing N-heterocyclic carbene and azido ligands - Effective catalysts for Suzuki-Miyaura cross-coupling reactions

Article abstract of DOI:10.1002/ejic.201200988

Azido-palladacycles containing C,N-donor and N-heterocyclic carbene ligands, [(C,N-L)Pd(N₃)(NHC)] [NHC = IPr; 1,3-bis(2,6- diisopropylphenyl)imidazol-2-ylidene], were prepared from (i) IPr and dinuclear Pd^II azides, [Pd(μ-N₃)(C,N-Lⁿ)]₂ [C,N-L¹H = N,N′-dimethylbenzylamine; C,N-L²H = 2-(2′-thienyl)pyridine; C,N-L³H = azobenzene; C,N-L ⁴H = 2-(p-tolyl)pyridine], or from (ii) NaN₃ and mononuclear Pd^II chloride, [Pd(Cl)(IPr)(C,N-Lⁿ)], in aqueous solution. The structures of two of these products were determined by X-ray crystallography. The palladacycles showed high catalytic efficiency toward activated and nonactivated aryl bromides (at room temperature) as well as aryl chlorides (at 80 C) in Suzuki-Miyaura cross-coupling reactions. In addition, coupling reactions of aryl chlorides using potassium aryl trifluoroborates instead of phenyl boronic acid gave good-to-excellent product yields. Suzuki-Miyaura cross-coupling reactions of aryl bromides and chlorides with organoboronic acid as well as potassium aryl trifluoroborates catalyzed by C,N-donor palladacycles containing N-heterocyclic carbene (NHC) and azido ligands under various conditions have been performed. Copyright

Full text of DOI:10.1002/ejic.201200988

FULL PAPER
DOI: 10.1002/ejic.201200988
C,N-Palladacycles Containing N-Heterocyclic Carbene and Azido Ligands –
Effective Catalysts for Suzuki–Miyaura Cross-Coupling Reactions
Yong-Joo Kim,*[a] Jung-Hyun Lee,[a] Taejung Kim,[b] Jungyeob Ham,*[b] Zhen Nu Zheng,[c]
and Soon W. Lee[c]
Keywords: Carbene ligands / Cross-coupling / Palladium / Azides
Azido-palladacycles containing C,N-donor and N-heterocy- of two of these products were determined by X-ray crystal-
clic carbene ligands, [(C,N-L)Pd(N3)(NHC)] [NHC = IPr; 1,3-
lography. The palladacycles showed high catalytic efficiency
bis(2,6-diisopropylphenyl)imidazol-2-ylidene], were pre- toward activated and nonactivated aryl bromides (at room
pared from (i) IPr and dinuclear PdII azides, [Pd(μ-N3)(C,N-
Ln)]2 [C,N-L1H = N,NЈ-dimethylbenzylamine; C,N-L2H = 2-
(2Ј-thienyl)pyridine; C,N-L3H = azobenzene; C,N-L4H = 2-(p-
tolyl)pyridine], or from (ii) NaN3 and mononuclear PdII chlor-
ide, [Pd(Cl)(IPr)(C,N-Ln)], in aqueous solution. The structures
temperature) as well as aryl chlorides (at 80 °C) in Suzuki–
Miyaura cross-coupling reactions. In addition, coupling reac-
tions of aryl chlorides using potassium aryl trifluoroborates
instead of phenyl boronic acid gave good-to-excellent prod-
uct yields.
catalysts that show higher activity toward chloroaryl deriva-
tives.
Introduction
Palladacycles (Pd-containing metallacycles) are widely
used as precursors, starting materials, or catalysts in Pd-
mediated organic syntheses.[1–8] C,N-Palladacycles have
been intensively investigated for use as catalysts in C–C or
C–N bond formation reactions. In this regard, numerous
studies on Suzuki–Miyaura C–C cross-coupling reactions
with dinuclear or mononuclear palladacycles containing
C,N-donor ligands have been reported.[9–21] The introduc-
tion of supporting ligands such as tertiary phosphanes or
other labile ligands into palladacycles has proved to be im-
portant for enhancing the catalytic efficiency.
Recently, we reported the C–C coupling reactivity of
azido-palladacycles containing C,N-donor and phosphane
ligands, in which the tertiary phosphane acts as a support-
ing ligand.[21] Interestingly, this class of palladacycles
showed moderate-to-high catalytic activity toward bro-
moaryl derivatives but poor reactivity toward chloroaryl de-
rivatives. This difference prompted us to develop efficient
To this end, we prepared several NHC azido-pallada-
cycles containing C,N-donor ligands, wherein the N-hetero-
cyclic carbene (NHC) ligand is known to be a stable alter-
native to tertiary phosphane ligands in many transition-
metal-catalyzed organic reactions, and analyzed their ac-
tivity for Suzuki–Miyaura C–C cross-coupling reactions.
Results and Discussion
Dinuclear azido-palladacycles, [Pd(μ-N3)(C,N-Ln)]2
[C,N-L1H = N,NЈ-dimethylbenzylamine; C,N-L2H = 2-(2Ј-
thienyl)pyridine; C,N-L3H = azobenzene; C,N-L4H = 2-(p-
tolyl)pyridine], were prepared from [Pd(μ-Cl)(C,N-Ln)]2 and
NaN3 by the previously described method.[21] Subsequent
reaction with an NHC [1,3-bis(2,6-diisopropylphenyl)imid-
azol-2-ylidene (IPr)] in a suitable solvent and at the required
temperature gave the desired NHC–azido-palladacycles
containing C,N-donor ligands, [Pd(N3)(IPr)(C,N-Ln)] (C1–
C4, see Schemes 1 and 2).
[a] Department of Chemistry, Kangnung-Wonju National
University,
Gangneung 210–702, South Korea
Fax: +82-33-640-2264
E-mail: yjkim@kangnung.ac.kr
Homepage: http://knusun.gwnu.ac.kr/~yjkim/
[b] Marine Chemomics Laboratory, Natural Medicine Center,
Korea, Institute of Science and Technology,
Gangneung 210–340, South Korea
Fax: +82-33-650-3629
E-mail: ham0606@kist.re.kr
[c] Department of Chemistry, Sungkyunkwan University, Natural
Science Campus,
Scheme 1.
Suwon 440–746, Korea
The NHC chloro palladacycle [Pd(Cl)(IPr)(C,N-L1)] (C5)
was prepared by cleaving a dinuclear palladacyle, [Pd(μ-
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201200988.
Eur. J. Inorg. Chem. 2012, 6011–6017
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6011

Y.-J. Kim, J. Ham et al.
FULL PAPER
Scheme 2.
Cl)(C,N-L1)]2, with IPr. C5 was previously prepared by the
one-pot reaction of IPr·HCl, N,N-dimethylbenzylamine,
PdCl2, and a base at 80 °C in CH3CN.[22] Treatment of C5
with an equimolar amount of aqueous NaN3 afforded the
azido-palladacycle C1. Several dinuclear azido-pallada-
cycles have been cleaved by tertiary or chelating phospha-
nes,[21,23] but cases involving NHC ligands (Scheme 1) have
not been reported to date. The IR spectra of C1–C4 in-
cluded a characteristic N3 stretching band at 2030–
Figure 1. ORTEP drawing of C1·THF, in which the cocrystallized
tetrahydrofuran (THF) molecule is omitted. Hydrogen atoms are
also omitted for clarity. Selected bond lengths [Å] and angles [°]:
Pd1–C28 2.022(3), Pd1–N4 2.033(3), Pd1–N3 2.111(2), Pd1–C1
2.129(2), N4–N5 1.178(4), N5–N6 1.160(4); C28–Pd1–N4 93.9(1),
C28–Pd1–N3 81.3(1), N4–Pd1–N3 174.8(1), C28–Pd1–C1 178.3(1),
N6–N5–N4 174.8(4).
1
2046 cm–1. The H NMR spectra of C1–C4 showed four
doublets in the range δ = 1.00–1.67 ppm, which indicates
the presence of isopropyl substituents. The 13C{1H} NMR
spectra showed weak singlets at δ = 175.6–190.5 ppm,
which are assignable to the NCN carbon atoms of the
NHCs coordinated to the Pd atom.
The molecular structures of C1 and C4 are shown in Fig-
ures 1 and 2, respectively. The details on the crystallo-
graphic data are given in the Supporting Information. C1
and C4 showed a slightly distorted square-planar Pd com-
plex with one C,N-donor ligand, one IPr ligand, and one
azido ligand. The donor nitrogen (N3 and N4) and carbon
atoms (C1 and C38) in C4 are mutually trans-oriented.
The molecular plane, defined by N3, N4, C1, C38, and
Pd1, is roughly planar with an average atomic displacement
of 0.075 Å. The five-membered ring (N1, N2, C1–C3) in
the NHC ligand is significantly twisted away from the mo-
lecular plane with a dihedral angle of 67.35(8)°. On the
other hand, the C,N-ligand (N3, C28–C38) is roughly co-
planar with the molecular plane with a dihedral angle of
8.07(8)°.
Figure 2. ORTEP drawing of C4·(THF) showing the atomic num-
bering and 30% probability displacement ellipsoids. For clarity, the
cocrystallized THF molecule and the hydrogen atoms are omitted.
Selected bond lengths [Å] and angles [°]: Pd1–C38 2.013(2), Pd1–
We evaluated the catalytic activity of C1–C5 by using N4 2.026(2), Pd1–N3 2.047(2), Pd1–C1 2.125(2), N1–C1 1.358(3),
N2–C1 1.367(3), N4–N5 1.184(3), N5–N6 1.149(3); C38–Pd1–N4
them (1 mol-%) in the room-temperature Suzuki–Miyaura
92.29(10), C38–Pd1–N3 80.81(10), N4–Pd1–N3 171.00(9), C38–
Pd1–C1 175.14(9), N5–N4–Pd1 128.0(2), N6–N5–N4 174.8(3).
cross-coupling reaction of 4-bromoacetophenone and phen-
ylboronic acid under N2 atmosphere; the reaction time and
bases were varied in each case and the results were com-
pared (Table 1). Most catalysts gave the desired product in chlorides (Table 2). The cross-coupling of 4-chloroaceto-
good-to-excellent yields.
phenone and phenylboronic acid in the presence of various
Complex C1 gave good product yields within a short re- palladacycles, solvents, and bases at 80 °C proceeded ef-
action time of less than 1 h (Table 1, Entries 6–8). Hence, ficiently to afford the optimal yields. The best result, 99%
we also carried out the same coupling reactions for aryl isolated yield, was obtained when using C1 and Cs2CO3 in
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C,N-Palladacycles Containing NHC and Azido Ligands
Table 1. Optimization of the reaction conditions for the Suzuki–
Miyaura reaction of 4-bromoacetophenone with phenylboronic
acid catalyzed by the azido-palladacycles, [Pd(N3)(IPr)(C,N-Ln)]
(C1–C4) and the chloro palladacycle (C5).
Table 3, Entries 1–5 show the results of C–C coupling re-
actions of various aryl bromides and phenylboronic acid in
methanol at room temperature (condition A). As expected,
the coupling products were obtained in high yields, which
are comparable to those other known Pd-catalyzed C–C
coupling reactions between aryl bromides and phenylbo-
ronic acid. The coupling reactions of aryl chlorides and
some heterocyclic chlorides with phenylboronic acid or or-
ganoboronic acids under condition B (Table 3, Entries 6–
13) also gave moderate-to-good yields. The exceptionally
low yield in Table 3, Entry 10 was probably caused by the
competing oxidative addition of an organic halide within
the catalytic cycle or deactivation of the phenyl ring by Cl
or CHO substituents. Therefore, these results suggest that
some NHC azido-palladacycles with C,N-donor ligands
can serve as efficient catalysts for C–C cross-coupling reac-
tions such as the reactions of aryl bromide or chlorides with
organoboronic acids.
Entry
Pd Solvent Base
cat.
Reaction
time
Isolated yield
[%]
1
2
3
4
5
6
C1 EtOH
C2 EtOH
C3 EtOH
C4 EtOH
C1 iPrOH
C1 MeOH K2CO3 40 min
C1 MeOH K2CO3 30 min
C1 MeOH Cs2CO3 25 min
C5 MeOH Cs2CO3 1.5 h
C1 MeOH NaOtBu 3 h
K2CO3 2.5 h
K2CO3 20 h
K2CO3 48 h
K2CO3 8.5 h
K2CO3 24 h
95
99
55[b]
99
94
97
98
98
98
93
7[a]
8[a]
9[a]
10[a]
Table 3. Suzuki–Miyaura coupling of aryl halides with organic bo-
ronic acid catalyzed by C1.
[a] Solvent (0.2 m). [b] Conversion yield.
Table 2. Optimization of the reaction conditions for the Suzuki–
Miyaura reaction of 4-chloroacetophenone with phenylboronic
acid catalyzed by complexes C1–C5.
Entry Pd cat.
Solvent
Base
Reaction Isolated
time
yield [%]
1
2
3
4
5
6
7
8
C1
C2
C3
C4
C1
C1
C1
C1
C1
C1
C5
EtOH
EtOH
EtOH
EtOH
MeOH
iPrOH
EtOH
EtOH
EtOH
EtOH
EtOH
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
NaOH
NaOtBu
Cs2CO3
Cs2CO3
2 h
2 h
2 h
4 h
5 h
5 h
5 h
30 min
30 min
10 min
5 h
99
98
99
94
73[a]
40[a]
51[a]
95
9
10
11
99
99
66[a]
[a] Conversion yield.
ethanol for a reaction time of 10 min (Table 2, Entry 10).
From Table 1, Entries 8 and 9 and Table 2, Entries 10 and
11, in it was apparent that the azido-palladacycle is a more
efficient catalyst than the corresponding chloride. Thus, we
speculate that the azido group is a much better leaving
group than the chloride ion during transmetallation by base
attack on the palladium intermediate. This result is consis-
tent with the general trend observed for leaving groups dur-
ing transmetallation in Pd-catalyzed Suzuki–Miyaura cou-
pling reactions, and thus confirms that a pseudo-halide is a
better leaving group than a halide.[2]
[a] Phenylboronic acid (0.36 mmol), Cs2CO3 (0.36 mmol), cat. C1
(2 mol-%). [b] [3-(Trifluoromethyl)phenyl]boronic acid was used. [c]
(4-Methoxyphenyl)boronic acid was used. [d] 3-Thiopheneboronic
acid was used.
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Y.-J. Kim, J. Ham et al.
FULL PAPER
400 MHz spectrometers. Chemical shifts were referenced to in-
ternal Me4Si. X-ray analysis was performed at CCRF (Cooperative
Center for Research Facilities) in the Sungkyunkwan University.
IPr [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene] was pre-
pared by the literature method[24] or purchased from Strem or TCI
chemical. [Pd(μ-N3)(C,N-Ln)]2 [C,N-L1H = N,NЈ-dimethylbenzyl-
amine; C,N-L2H = 2-(2Ј-thienyl)pyridine; C,N-L3H = azobenzene;
C,N-L4H = 2-(p-tolyl)pyridine] were prepared by the method de-
scribed in ref.[21] Aryl BF3K compounds were prepared by methods
reported in the literature.[25–26]
We also carried out Suzuki–Miyaura cross-coupling reac-
tions using other boron reagents such as potassium aryl tri-
fluoroborates with p-chloroacetophenone and obtained the
corresponding coupling products in good-to-excellent
yields. The results are listed in Table 4.
Table 4. Suzuki coupling of aryl chloride with potassium aryltri-
fluoroborates catalyzed by C1.
[Pd(N3)(IPr)(C,N-L1)](C,N-L1H = N,NЈ-dimethylbenzylamine) C1:
IPr (0.168 g, 0.43 mmol) in toluene (2 mL) was added to a toluene
(2 mL) solution of [Pd(μ-N3)(C,N-L1)]2 (0.123 g, 0.22 mmol) at
room temperature. An initial pale yellow suspension turned to a
yellow solution. After stirring for 6 h at 40 °C, the solvent was re-
moved, and the resulting residue was solidified with diethyl ether
and then washed with diethyl ether (1 mLϫ3) in an ice bath to
yield a white solid. Recrystallization from diethyl ether (20 mL)
gave white crystals of [Pd(N3)(IPr)(C,N-L1)] (C1, 0.162 g, 56%). IR
(KBr): ν = 2038 (N ) cm–1. 1H NMR (300 MHz, CDCl ): δ = 1.10
˜
3
3
[d, J = 6.6 Hz, 6 H, CH(CH3)2], 1.19 [d, J = 6.9 Hz, 6 H, CH-
(CH3)2], 1.43 [d, J = 6.6 Hz, 6 H, CH(CH3)2], 1.58 [d, J = 6.6 Hz,
6 H, CH(CH3)2], 2.00 (s, NMe2), 2.99 [sept, J = 6.8 Hz, 2 H,
CH(CH3)2], 3.22 [sept, J = 6.8 Hz, 2 H, CH(CH3)2], 3.64 (s, 2 H,
CH2), 6.76–6.98 (m, 3 H, ArH), 7.19–7.47 (m, 9 H, ArH) ppm. 13
C
NMR (75 MHz, CDCl3): δ = 15.3 [s, CH(CH3)2], 22.3 [s, CH-
(CH3)2], 22.9 [s, CH(CH3)2], 26.5 (s, NMe2), 29.2 [s, CH(CH3)2],
52.0 (s, CH2), 75.2, 120.6, 123.5, 123.6, 123.7, 125.1, 125.4, 129.8,
133.7, 135.9, 143.9, 146.9, 147.7, 154.9, 190.5 (NCN) ppm.
C36H48N6Pd (671.22): calcd. C 64.42, H 7.21, N 12.52; found C
64.29, H 7.23, N 12.33.
Complex C1 was also prepared by an alternate route by using
[Pd(Cl)(IPr)(C,N-L1)] (C5). Compound C5 was analogously pre-
pared by treating [Pd(μ-Cl)(C,N-L1)]2 with two equiv. of IPr. The
C5 was previously prepared[22] and is also commercially available
(TCI chemical). To a Schlenk flask containing C5 (0.502 g,
0.76 mmol) were added CH2Cl2 (3 mL) and NaN3 solution
(0.054 g, 0.83 mmol) dissolved in H2O (1 mL) in that order. After
stirring for 3 h at room temperature, the solvent was completely
evaporated to yield a gray solid, which was extracted with CH2Cl2.
Conclusions
We have prepared several NHC–azido-palladacycles that
contain C,N-donor ligands and have demonstrated their
catalytic efficiency for Suzuki–Miyaura cross-coupling reac-
tions. The coupling reactions with activated and nonacti-
vated aryl bromides at room temperature as well as those Recrystallization from CH2Cl2/hexane gave white crystals of C1
(0.432 g, 85%).
with aryl chlorides at 80 °C proceeded successfully to give
the products in moderate-to-good yields. Azido-pallada-
cycles showed higher catalytic efficiency than their chloride
counterparts. Our results suggest that the combination of
azide and C,N-donor ligands in the metallacycle might en-
[Pd(N3)(IPr)(C,N-L2)] [C,N-L2H = 2-(2Ј-thienyl)pyridine] C2: IPr
(0.194 g, 0.50 mmol) dissolved in THF (3 mL) was added to a THF
(2 mL) solution of [Pd(μ-N3)(C,N-L2)]2 (0.196 g, 0.32 mmol). An
initial pale yellow suspension instantly dissolved and then again
hance its catalytic activity. Our NHC–azido-palladacycles turned to another pale yellow suspension. After stirring the reac-
tion mixture for 4 h at 50 °C, the insoluble materials were removed
by filtration, and the resulting filtrate was evaporated to yield an
oily solid. The crude product was isolated with diethyl ether and
washed with diethyl ether (2 mLϫ3) to give a pale yellow solid.
Recrystallization from diethyl ether gave pale yellow crystals of
could also successfully catalyze Suzuki–Miyaura cross-cou-
pling reactions of aryl chlorides and potassium aryl trifluo-
roborates.
[Pd(N )(IPr)(C,N-L2)] (C2, 0.236 g, 68%). IR (KBr): ν = 2045 (N ).
˜
3
3
Experimental Section
1H NMR (300 MHz, CDCl3): δ = 0.89 [d, J = 6.6 Hz, 6 H,
CH(CH3)2], 1.08 [d, J = 6.9 Hz, 6 H, CH(CH3)2], 1.18 [d, J =
6.6 Hz, 6 H, CH(CH3)2], 1.54 [d, J = 6.6 Hz, 6 H, CH(CH3)2], 3.16
[sept, J = 6.9 Hz, 4 H, CH(CH3)2], 6.68 (d, J = 7.3 Hz, 1 H, ArH),
6.83 (dt, J = 1.4, 7.3 Hz, 1 H, ArH), 6.92 (dt, J = 1.4, 7.3 Hz, 1 H,
ArH), 7.12 (br., 1 H, ArH), 7.18 (dd, J = 2.2, 7.3 Hz, 1 H, ArH),
7.49 (d, J = 8.1 Hz, 1 H, ArH), 7.63 (dt, J = 1.8, 8.0 Hz, 1 H,
ArH), 8.55 (br., 1 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ =
22.3 [s, CH(CH3)2], 22.9 [s, CH(CH3)2], 26.3 [s, CH(CH3)2], 26.7 [s,
General: All manipulations of air-sensitive complexes were per-
formed under N2 or Ar by using standard Schlenk line techniques.
Solvents were distilled from Na–benzophenone. The analytical
laboratories at Kangnung-Wonju National University performed
elemental analyses with a CE Instruments EA1110 elemental ana-
lyzer. IR spectra were recorded with a Perkin–Elmer BX spectro-
photometer. NMR (1H and 13C{1H}) spectra were obtained with
JEOL Lamda 300, ECA 600 MHz, and Bruker UltraShield Plus
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Eur. J. Inorg. Chem. 2012, 6011–6017

C,N-Palladacycles Containing NHC and Azido Ligands
CH(CH3)2], 28.6 [s, CH(CH3)2], 29.3 [s, CH(CH3)2], 111.8, 122.4, over two runs. The products were identified by IR and NMR (1H
122.9, 123.3, 124.1, 124.4, 124.5, 129.1, 129.9, 135.4, 137.9, 138.2,
144.7, 146.1, 147.3, 149.5, 154.5, 164.1, 177.8 (NCN) ppm.
C39H42N6PdS (733.26): calcd. C 62.01, H 6.07, N 12.05; found C
62.27, H 6.38, N 12.51.
and 13C) spectroscopy based on the literature data.
4-Acetylbiphenyl:[27] White solid. IR (KBr): ν = 1679 (CO) cm–1.
˜
1H NMR (400 MHz, CDCl3, 25 °C): δ = 2.63 (s, 3 H, CH3), 7.37–
7.41 (m, 1 H), 7.44–7.48 (m, 2 H), 7.62 (dd, J = 1.6, 8.0 Hz, 2 H),
7.67 (d, J = 8.4 Hz, 2 H), 8.02 (d, J = 8.4 Hz, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 26.7 (CH3), 127.2, 127.3, 128.3, 128.9,
129.0, 135.9, 139.9, 145.8, 197.7 (CO) ppm.
[Pd(N3)(IPr)(C,N-L3)] (C,N-L3H = azobenzene) C3: IPr (0.354 g,
0.91 mmol) in THF (5 mL) was added to a CH2Cl2 (25 mL) solu-
tion of [Pd(μ-N3)(C,N-L3)]2 (0.300 g, 0.46 mmol). An initial orange
suspension slowly turned to a red solution. After stirring the reac-
tion mixture for 4 h at room temperature, the solvent was removed,
and the resulting residue was solidified with diethyl ether and
washed with diethyl ether (2 mL ϫ 3) to yield a red solid.
Recrystallization from diethyl ether gave red crystals of
4-Fluorobiphenyl:[28] White solid. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 7.08–7.14 (m, 2 H), 7.31 (m, 1 H), 7.42 (m, 2 H), 7.51–
7.55 (m, 4 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 115.6 (d,
JCF = 21 Hz), 137.3 (d, JCF = 3.4 Hz), 140.3, 162.5 (d, JCF
=
245 Hz) ppm. 19F NMR: δ = –115.8 (s) ppm.
[Pd(N )(IPr)(C,N-L3)] (C3, 0.462 g, 71%). IR (KBr): ν = 2046 (N )
˜
3
1
3
4-Methoxybiphenyl:[29] White solid. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 3.85 (s, 3 H, OCH3), 6.97 (d, J = 8.4 Hz, 2 H), 7.28–
7.32 (m, 1 H), 7.39–7.43 (m, 2 H), 7.52–7.56 (m, 4 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 55.3 (OCH3), 114.2, 126.7, 126.8,
127.2, 127.3, 133.8, 140.8, 159.2 ppm.
cm–1. H NMR(300 MHz, CDCl3): δ = 0.92 [d, J = 6.4 Hz, 6 H,
CH(CH3)2], 0.95 [d, J = 6.8 Hz, 6 H, CH(CH3)2], 1.03 [d, J =
6.8 Hz, 6 H, CH(CH3)2], 1.75 [d, J = 6.8 Hz, 6 H, CH(CH3)2], 3.10
[sept, J = 6.8 Hz, 2 H, CH(CH3)2], 3.39 [sept, J = 6.8 Hz, 2 H,
CH(CH3)2], 6.71–6.72 (m, 2 H, ArH), 6.83–6.87 (m, 2 H, ArH),
6.94–6.98 (m, 4 H, ArH), 7.06–7.16 (m, 4 H, ArH), 7.22–7.24 (m,
2 H, ArH), 7.75–7.76 (dd, J = 1.9 Hz, 2 H, ArH), 7.79 (d, J =
7.3 Hz, 2 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ = 22.5 [s,
CH(CH3)2], 22.7 [s, CH(CH3)2], 26.2 [s, CH(CH3)2], 26.5 [s,
CH(CH3)2], 28.6 [s, CH(CH3)2], 29.4 [s, CH(CH3)2], 123.3, 123.9,
124.4, 124.5, 124.7, 128.0, 128.2, 129.9, 130.1, 130.2, 131.1, 135.3,
137.1, 144.3, 147.2, 152.0, 156.8, 165.1, 175.6 (NCN) ppm.
C39H45N7Pd (718.23): calcd. C 65.22, H 6.32, N 13.65; found C
65.58, H 6.78, N 13.73.
3-Methoxybiphenyl:[30,31] White solid. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 3.89 (s, 3 H, OCH3), 6.92 (dd, J = 2.4, 8.4 Hz, 1 H),
7.16 (d, J = 2.0 Hz, 1 H), 7.21 (d, J = 7.6 Hz, 1 H, 1 H), 7.35–7.40
(m, 2 H), 7.46 (t, J = 7.2 Hz, 2 H) 7.61 (d, J = 7.6 Hz, 2 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 55.3 (OCH3), 112.7, 112.9,
119.7, 127.2, 127.4, 128.8, 129.8, 141.1, 142.8, 160.0 ppm.
2-Methoxybiphenyl:[29] White solid. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 3.79 (s, 3 H, OCH3), 6.99 (d, J = 8.4 Hz, 1 H), 7.02 (d,
J = 1.2, 7.4 Hz, 1 H), 7.29–7.33 (m, 3 H), 7.38–7.42 (m, 2 H), 7.51–
7.54 (m, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 55.6
(OCH3), 111.3, 120.9, 126.9, 128.0, 128.8, 129.6, 130.8, 130.9,
138.6, 156.5 ppm.
[Pd(N3)(IPr)(C,N-L4)] [C,N-L4H = 2-(p-tolyl)pyridine] C4: IPr
(0.245 g, 0.63 mmol) dissolved in THF (3 mL) was added to a THF
(30 mL) solution of [Pd(μ-N3)(C,N-L4)]2 (0.200 g, 0.32 mmol). An
initial pale yellow suspension slowly turned to a pale yellow solu-
tion. After stirring the reaction mixture for 4 h at 40 °C, the solvent
was removed, and the resulting residue was solidified with diethyl
ether and washed with diethyl ether (2 mL ϫ3) to yield a pale
yellow solid. Recrystallization from diethyl ether gave white crystals
4-(Trifluoromethyl)biphenyl:[21,32] 1H NMR (400 MHz, CDCl3,
25 °C): δ = 7.37–7.41 (m, 1 H), 7.44–7.48 (m, 2 H), 7.58–7.60 (m,
2 H), 7.68 (s. 4 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 120.1,
123.0, 125.7 (q, JCF = 15 Hz), 127.3, 127.4, 129.0 (q, JCF = 129 Hz),
139.8, 144.8 ppm. 19F NMR: δ = –62.4 (s) ppm.
of [Pd(N )(IPr)(C,N-L4)] (C4, 0.340 g, 76%). IR (KBr): ν = 2030
˜
3
(N3) cm–1. 1H NMR (300 MHz, CDCl3, 25 °C): δ = 0.74 (d, J =
6.9 Hz, 6 H, CH(CH3)2), 1.02 [d, J = 6.9 Hz, 6 H, CH(CH3)2], 1.13
[d, J = 6.6 Hz, 6 H, CH(CH3)2], 1.50 [d, J = 6.6 Hz, 6 H, CH-
(CH3)2], 2.20 (s, 3 H, CH3), 2.98 [sept, J = 6.6 Hz, 2 H, CH-
(CH3)2], 3.25 [sept, J = 6.9 Hz, 2 H, CH(CH3)2], 6.40 (s, 1 H, ArH),
6.77 (d, J = 7.7 Hz, 1 H, ArH), 7.05 (br., 1 H, ArH), 7.18–7.25
(br., 5 H, ArH), 7.33–7.45 (br., 6 H, ArH), 7.57 (br., 1 H, ArH)
ppm. 13C NMR (75 MHz, CDCl3): δ = 21.9 [s, CH(CH3)2], 22.2 [s,
CH(CH3)2], 26.2 [s, CH(CH3)2], 26.7 [s, CH(CH3)2], 28.6 [s,
CH(CH3)2], 29.4 [s, CH(CH3)2], 122.0, 122.8, 124.2, 124.3, 124.9,
135.8, 137.8, 138.0, 139.2, 143.5, 144.7, 147.6, 149.3, 154.0, 164.2,
178.4 (NCN) ppm. C39H46N6Pd (705.23): calcd. C 66.42, H 6.57,
N 11.92; found C 66.61, H 6.81, N 12.20.
1
3-Phenylpyridine:[27,32,33] Yellow Oil. H NMR (400 MHz, CDCl3,
25 °C): δ = 7.36–7.43 (m, 2 H), 7.48 (t, J = 7.6 Hz, 2 H), 7.58 (d,
J = 7.6 Hz, 2 H), 7.88 (d, J = 8.0 Hz, 1 H), 8.62 (br., 1 H), 8.88
(br., 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 123.7, 127.2,
128.1, 129.1, 130.9, 134.4, 137.9, 130.9, 148.3, 148.5 ppm.
1,1Ј:3Ј,1ЈЈ-Terphenyl-4Ј-carbaldehyde:[34] White solid. 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 7.46–7.50 (m, 8 H), 7.67–7.68 (m, 3
H), 7.69–7.75 (m, 1 H), 8.11 (d, J = 8.0 Hz, 1 H), 10.0 (s, 1 H,
CHO) ppm. 13C NMR (100 MHz, CDCl3): δ = 126.5, 127.4, 128.3,
128.5, 129.0, 129.4, 130.1, 132.5, 137.9, 139.7, 146.3, 146.5, 192.1
(CO) ppm.
4-Acetyl-4Ј-(trifluoromethyl)biphenyl:[35] White solid. 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 2.65 (s, 3 H, CH3), 7.59 (t, J =
7.6 Hz, 1 H), 7.65–7.70 (m, 3 H), 7.79 (d, J = 7.6 Hz, 1 H), 7.86
(s, 1 H), 8.06 (dd, J = 1.6, 6.6 Hz, 1 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 26.7 (CH3), 120.1, 122.3, 124.5 (q, JCF = 3.7 Hz), 124.8
(q, JCF = 3.7 Hz), 125.4, 127.4, 129.1, 129.5, 130.6, 131.4 (q, JCF
= 32 Hz), 136.5, 140.7, 144.2, 197.6 (CO) ppm.
General Procedure for Suzuki–Miyaura Cross-Coupling Reactions:
To
a 13 ϫ90 mm test tube were added phenylboronic acid
(0.18 mmol), CsCO3 (0.18 mmol), Pd catalyst (1ϫ10–3 mmol,
1 mol-%), and aryl halide (0.15 mmol) with a stirring bar. Ethanol
or methanol (0.2 m) was added, and the resulting mixture was
heated in an oil bath at 80 °C. The reaction was monitored by TLC.
After the aryl halide was totally consumed, the reaction mixture
was cooled to room temperature and quenched with brine
(1.0 mL), and then extracted with EtOAc (3ϫ1.0 mL). The re-
sulting organic solution was dried with MgSO4 and concentrated
with a rotary evaporator. The crude product was purified by pre-
parative TLC (0.5 mm). Isolated yields are based on aryl halides
1
4-Acetyl-4Ј-methoxybiphenyl:[36] White solid. H NMR (400 MHz,
CDCl3, 25 °C): δ = 2.62 (s, 3 H, CH3), 3.85 (s, 3 H, OCH3), 6.99
(d, J = 8.8 Hz, 2 H), 7.60 (dd, J = 8.4, 25 Hz, 2 H), 7.99 (d, J =
8.4 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 26.6 (CH3),
55.4 (OCH3), 114.4, 126.6, 128.4, 129.0, 132.2, 135.3, 145.4, 159.9,
197.7 (CO) ppm.
Eur. J. Inorg. Chem. 2012, 6011–6017
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
6015

Y.-J. Kim, J. Ham et al.
FULL PAPER
1-[4-(Thiophen-3-yl)phenyl]ethanone:[30,32,37] White solid. H NMR
(400 MHz, CDCl3, 25 °C): δ = 2.62 (s, 3 H, CH3), 7.41–7.45 (m, 2
H), 7.57–7.58 (m, 1 H), 7.68 (d, J = 8.4 Hz, 2 H), 8.99 (d, J =
8.4 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 26.6 (CH3),
122.1, 126.2, 126.4, 126.8, 129.1, 135.6, 140.2, 141.1, 197.5 (CO)
ppm.
1
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4-Acetyl-(4Ј-methyl)biphenyl:[38] White solid. IR (KBr): ν = 1680
˜
1
(CO) cm–1. H NMR (400 MHz, CDCl3, 25 °C): δ = 2.41 (s, 3 H,
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CH3), 2.63 (s, 3 H, CH3), 7.28 (d, J = 8.0 Hz, 2 H), 7.53 (d, J =
8.1 Hz, 2 H), 7.67 (d, J = 8.4 Hz, 2 H), 8.02 (d, J = 8.4 Hz, 2 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 21.2 (CH3), 26.6 (CH3),
126.9, 127.1, 128.9, 129.7, 135.6, 136.9, 138.2, 145.7, 197.8 (CO)
ppm.
1-[4-(Naphthalen-2-yl)phenyl]ethanone:[39] White solid. 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 2.66 (s, 3 H, CH3), 7.50 (m, 2 H),
7.76 (dd, J = 1.6, 8.6 Hz, 2 H), 7.81–7.83 (m, 2 H), 7.87–7.96 (m,
3 H), 8.07–8.09 (m, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
26.7 (CH3), 125.2, 126.4, 126.5, 126.6, 127.5, 127.7, 128.4, 128.7,
129.0, 133.0, 133.6, 135.9, 137.2, 145.7, 197.8 (CO) ppm.
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4Ј-Acetyl-3,4-(methylenedioxy)biphenyl:[33] White solid. 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 2.63 (s, 3 H, CH3), 6.02 (s, 2 H),
6.90 (d, J = 8.0 Hz, 1 H), 7.10 (s, 1 H), 7.12 (s, 1 H), 7.60 (d, J =
8.4 Hz, 2 H), 7.99 (d, J = 8.4 Hz, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 26.6 (CH3), 101.4 (s, CH2), 107.6, 108.8, 121.1, 126.9,
128.9, 134.1, 135.6, 145.5, 147.9, 148.4, 197.6 (CO) ppm.
X-ray Structure Determination: All X-ray data were collected with
a Bruker Smart APEX or APEX2 diffractometer equipped with a
Mo X-ray tube. Collected data were corrected for absorption with
SADABS based upon the Laue symmetry by using equivalent re-
flections.[40] All calculations were performed with SHELXTL pro-
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hydrogen atoms were refined anisotropically, and all hydrogen
atoms were generated in ideal positions and refined in a riding
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Acknowledgments
This work was supported by Basic Science Research Program
through the National Research Foundation of Korea (NRF)
funded by the Ministry of Education, Science and Technology
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Received: August 29, 2012
Published Online: November 2, 2012
Eur. J. Inorg. Chem. 2012, 6011–6017
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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