Pincer-type bis(carbene)-derived complexes of nickel(II): Synthesis, structure, and catalytic activity

Article abstract of DOI:10.1016/j.jorganchem.2008.11.003

Air- and moisture-stable NHC (N-heterocyclic carbene)-derived CNC-type pincer complexes of nickel(II) 4a-d were successfully synthesized, and their structures were fully characterized using X-ray crystallography and analytical and spectroscopic methods. These complexes exhibit a high catalytic activity for the Suzuki-Miyaura coupling reaction of aryl bromides and chlorides with aryl- and alkenylboronic acids, providing an array of biphenyls and stilbenes generally in high yields.

Full text of DOI:10.1016/j.jorganchem.2008.11.003

Journal of Organometallic Chemistry 694 (2009) 389–396
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Pincer-type bis(carbene)-derived complexes of nickel(II): Synthesis, structure,
and catalytic activity
a,*
a
b
a
a,*
Kiyofumi Inamoto , Jun-ichi Kuroda , Eunsang Kwon , Kou Hiroya , Takayuki Doi
a
Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3, Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan
Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, 6-3, Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Air- and moisture-stable NHC (N-heterocyclic carbene)-derived CNC-type pincer complexes of nickel(II)
Received 26 September 2008
Received in revised form 29 October 2008
Accepted 4 November 2008
Available online 7 November 2008
4
a–d were successfully synthesized, and their structures were fully characterized using X-ray crystallog-
raphy and analytical and spectroscopic methods. These complexes exhibit a high catalytic activity for the
Suzuki–Miyaura coupling reaction of aryl bromides and chlorides with aryl- and alkenylboronic acids,
providing an array of biphenyls and stilbenes generally in high yields.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Pincer complex
Nickel
N-heterocyclic carbene
Suzuki–Miyaura coupling
1
. Introduction
The longstanding search for efficient catalytic systems in transi-
2. Results and discussion
2.1. Synthesis and characterization of NHC-derived nickel–pincer
tion metal-catalyzed coupling reactions remains an active subject
in organic synthesis. Metallacycles possessing the pincer ligand
framework could be an efficient system because of their consider-
able thermal and oxidative stabilities [1–9]. Various types (e.g.,
PCP–, NCN–, CNC–) of pincer complexes of transition metals have
been reported to date; among them, palladium–pincer complexes
have been widely investigated and employed as catalysts for
cross-coupling reactions [10–15]. Much less attention has been
paid to the nickel–pincer complexes [16–22], although the use of
nickel catalysts instead of palladium catalysts sometimes offers
advantages, such as cost effectiveness and distinct catalytic abili-
ties [23–33]. In this regard, we recently reported the synthesis of
a CNC-type pincer complex of nickel 1 (Fig. 1) and showed its high
catalytic activities in Heck reaction, Suzuki–Miyaura coupling, and
Kumada–Tamao–Corriu coupling [34,35]. Herein, we report the
synthesis and characterization of a series of new NHC-derived
nickel–pincer complexes 4a–d and provide a preliminary account
of their catalytic activities.
complexes 4a–d
Scheme 1 shows the synthetic route for novel NHC-derived
nickel–pincer complexes 4a–d. Bis-imidazolium salts 2a–d were
readily prepared from the reactions of 2,6-dibromopyridine or
2,6-dibromomethylpyridine with the corresponding imidazoles
[36]. Unlike the synthesis of nickel complex 1 we previously re-
ported, the direct cyclometallation of 2 with several nickel sources
was not successful. Instead, nickel–pincer complexes were ob-
tained via the transmetallation of silver salts 3a–d, which were
easily synthesized from the reactions of the corresponding imi-
dazolium salts 2 with Ag
AgBF finally gave the desired nickel–pincer complexes 4a–d,
which were all yellow crystals and quite stable in air [37]. They
2
O [36]. Counter anion exchange using
4
were soluble in CHCl
be recrystallized from CH
3
, CH
2
Cl
2
, MeOH, DMSO, and MeCN and could
and light petroleum. The complexes
2
Cl
2
4a–d were characterized by analytical and spectroscopic methods.
1
In the H NMR spectra of 4c and 4d, the signals corresponding to
the methyl groups of the ortho-methyls of mesityl groups and
the DIPP (2,6-diisopropylphenyl) appear as one singlet (12H) and
two doublets (12H + 12H), respectively, indicating that these two
complexes have a symmetrical plane. On the other hand, the 1
H
NMR spectra of 4a and 4b show that signals corresponding to the
same methyl groups appear as two singlets (6H + 6H) and four
doublets (6H + 6H + 6H + 6H), respectively, resulting from the
*
Corresponding authors. Tel.: +81 22 795 6866; fax: +81 22 795 6864
K. Inamoto).
E-mail address: inamoto@mail.pharm.tohoku.ac.jp (K. Inamoto).
(
0
022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.11.003

3
90
K. Inamoto et al. / Journal of Organometallic Chemistry 694 (2009) 389–396
lected crystallographic data. The molecular structures are depicted
Br
N
in Fig. 2 and Table 2 lists selected bond lengths and bond angles.
The nickel center of all complexes exhibited an only slightly dis-
torted square-planar coordination geometry, similar to that of the
previously reported nickel complex 1. A least-squares plane fitted
to the nickel and surrounding ligand atoms (i.e., the chlorine atom,
the nitrogen atom of pyridine, and the two carbenes) showed a
small deviation within 0.048 Å for all four complexes.
N
N
Ni
N
N
Me
Me
Br
1
Fig. 1. Previously reported nickel–pincer complex.
Although the pyridine ring plane was nearly coplanar with the
least-square planes (i.e., the Cl(1)–C(1)–N(3)–C(11)) for both 4c
(
(
3.80°) and 4d (2.63°), the pyridine plane of 4a and 4b rotated
i.e., the pyridine ring and Cl(1)–C(1)–N(3)–C(13) planes) through
unsymmetrical structures of these complexes. These observations
were previously reported for the palladium analogues [36].
an angle of 46.60° and 46.73°, respectively. These structural differ-
ences could be correlated with the catalytic activity of 4a,b and
2.2. Crystal structures of complexes 4a–d
4
c,d, as described later.
The structural feature of the complexes that is related to the sta-
bility toward air and moisture is also found in a crystal structure.
We determined the structures of all complexes in the solid-
state using X-ray crystallographic analysis. Table 1 summarizes se-
BF4
N
Ag
Å MS
ClCH CH Cl
2
O
N
NiCl -glyme
CH Cl , rt, 24 h
2
2
N
4
2
N
N
N
N
N
N
ClAg
AgCl
then AgBF
rt, 16 h
Ni
Cl
2
2
4
N
R
N
R
Reflux, 16 h
N
R
N
N
R
N
R
2Br
R
2
a : R = Mes
3a : R = Mes (94%)
3b : R = DIPP (>99%)
4a : R = Mes (>99%)
4b : R = DIPP (78%)
2
b : R = DIPP
BF4
Ag O
NiCl -glyme
2
2 2
2
N
N
N
N
N
N
CH Cl , rt, 24 h
4
Å MS
N
N
N
ClAg
ClCH CH Cl
then AgBF4
rt, 16 h
N
R
N
R
2
2
N
R
N
Ni
AgCl
N
R
N
R
Reflux, 16 h
2Br
R
Cl
2
c : R = Mes
d : R = DIPP
3c : R = Mes (85%)
3d : R = DIPP (87%)
4c : R = Mes (99%)
4d : R = DIPP (88%)
2
Scheme 1. Synthesis of 4a–d.
Table 1
Summary of crystallographic data for 4a–d.
Compound
4a
4b
4c
4d
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C
31
H
33BClF
4
N
5
Ni ꢀ CH
3
COCH
3
C
37
H
45BClF
4
N
5
2
Ni ꢀ CH Cl
2
C
29
H
29BClF
4
N
5
2
Ni ꢀ CH Cl
2
35 4 5
C H41BClF N Ni
714.67
173(1)
0.71073
Monoclinic
P2 /n
8.969(3)
21.811(8)
17.727(7)
90
96.947(5)
90
3442(2)
4
1.379
1.432
1488
825.69
173(1)
0.71073
Triclinic
713.47
173(1)
0.71073
Monoclinic
P2 /c
10.631(6)
19.059(11)
16.230(9)
90
99.646(9)
90
3242(3)
4
1.462
1.114
1464
712.70
173(1)
0.71073
Monoclinic
C2/c
35.07(6)
8.559(20)
23.06(4)
90
100.399(19)
90
6809(23)
8
1.390
1.421
2976
ꢀ
1
P1
1
9.297(4)
12.077(4)
17.791(7)
85.993(9)
88.314(7)
85.993(8)
1987.1(13)
2
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
3
V (Å )
Z
D
l
3
calcd. (g/m )
1.380
1.346
860
(mm 1
ꢁ
)
F(000)
Reflections collected/unique
49991/7812 (0.142)
29797/9033 (0.064)
45833/7272 (0.079)
48592/7745 (0.084)
(int)
[R ]
Completeness to h
27.47 (99.0%)
Numerical
Full-matrix least-squares on F
27.47 (99.3%)
Numerical
27.35 (99.1%)
Numerical
27.50 (99.2%)
Numerical
Absorption correction
Refinement method
2
Full-matrix least-squares on F2
Full-matrix least-squares on F2
Full-matrix least-squares on F2
1.002
Goodness-of-fit on (GOF) F2
0.796
1.010
1.005
Final R indices [I > 2
r
I)]
R
1
= 0.0543,
wR = 0.1087
2.67/ꢁ1.46
R
1
= 0.0536,
wR = 0.1262
0.98/ꢁ0.84
R
1
= 0.0594
wR = 0.1600
1.11/ꢁ0.99
R
1
= 0.0518,
wR = 0.0899
1.03/ꢁ0.92
2
2
2
2
Maximum peak/hole (e Å 3
ꢁ
)

K. Inamoto et al. / Journal of Organometallic Chemistry 694 (2009) 389–396
391
Fig. 2. Molecular structures of the complexes of 4a–d showing 30% probability
ꢁ
ellipsoids. Hydrogen atoms, (BF
omitted for clarity.
4
)
anion, and the solvent molecular have been
Fig. 3. Space-filling representation of the solid-state molecular structure of the
complexes of 4a–d. Hydrogen atoms, (BF4) anion, and the solvent molecular have
been omitted for clarity.
ꢁ
Thus, the metal center is effectively protected by the ligand, as
shown in the space-filling model of the complexes (Fig. 3).
2
.3. Catalytic activity of complexes 4a–d
ing groups were smoothly reacted with phenylboronic acid in the
presence of 1 mol% of nickel–pincer complexes 4a–d, producing
biphenyl compounds 5–9 generally in high yields (Table 4).
Various aryl- and alkenylboronic acids also were suitable sub-
strates for this coupling process (Table 5). Thus, an array of biphe-
nyl or stilbene compounds were successfully obtained from this
reaction in the presence of 4d.
To evaluate the catalytic activity of the nickel–pincer complexes
4
4
1
a–d, we first examined the Suzuki–Miyaura coupling reaction of
-bromobenzonitrile with phenylboronic acid in the presence of
mol% of 4a (Table 3). After several screenings, 4a turned out to
3 4
be an efficient catalyst for this process. Thus, using K PO as a base,
the coupling reaction proceeded efficiently at 120 °C in various sol-
vents such as MeCN (entry 2), dioxane (entry 4), and toluene (entry
6
). Decreasing the reaction temperature to 100 °C, however, led to
3. Conclusion
poorer results in those solvents (entries 3, 5, and 7). Among the
s
reaction media tested, only BuOH produced a relatively high yield
In summary, a series of novel NHC-derived nickel–pincer
complexes were successfully synthesized, fully characterized by
analytical and spectroscopic methods, and further identified by
X-ray crystallography. These complexes were all four-coordinated
cationic complexes with a slightly distorted square-planar coordi-
nation geometry, and they were successfully used as catalysts for
the Suzuki–Miyaura coupling reaction of aryl bromides and chlo-
rides with aryl- or alkenylboronic acids, producing biphenyls and
stilbenes in good to high yields. It is worth noting that nickel cat-
alysts 4a–d we developed, which are easily prepared from inex-
pensive, commercially available materials, are considerably stable
to both air and moisture, which makes our system highly applica-
ble. Ongoing work is directed at elucidating the precise reaction
mechanism, further evaluating the catalytic activities of these
even at 100 °C, although a longer reaction time was necessary for
the completion of the reaction (entries 12 and 13) [38]. Complexes
b, 4c, and 4d also showed a catalytic activity for this process.
4
Interestingly, the reaction proceeds faster with 4c and 4d, which
both have the five-membered metallacycle backbone, compared
to 4a and 4b, which possess two fused six-membered rings [39].
A possible explanation for this result is that 4c and 4d possess a
more sterically hindered environment around nickel compared to
a and 4b, which could enhance the reductive elimination step
during the catalytic cycle. However, the precise reaction mecha-
nism remains to be elucidated.
4
Under the optimal conditions identified, several aryl bromides
and chlorides with both electron-withdrawing and electron-donat-
Table 2
Selected bond length and angles of 4a–d.
Ni–C(carbene_1)
Ni–N
Ni–C(carbene_2)
Ni–X
angle N–Ni–Cl
angle C–Ni–C
4
4
4
4
1
a
b
c
1.910(4)
1.918(2)
1.913(3)
1.910(3)
1.932(4)
1.921(3)
1.950(2)
1.867(2)
1.858(2)
1.862(3)
1.891(3)
1.911(2)
1.921(3)
1.912(2)
1.920(5)
2.1581(11)
2.1466(8)
2.1521(9)
2.1348(8)
2.2783(7)
170.31(10)
178.29(7)
177.05(10)
178.56(8)
176.36(11)
173.42(16)
174.73(11)
162.37(14)
162.31(12)
163.02(19)
d
a
a
Data from Ref. [34].

3
92
K. Inamoto et al. / Journal of Organometallic Chemistry 694 (2009) 389–396
Table 3
J = 1.6 Hz), 7.18 (2H, d, J = 7.7 Hz), 7.47 (2H, d, J = 1.6 Hz), 7.75
a
Optimization of reaction parameters.
13
(
3
1H, t, J = 7.7 Hz). 100 MHz C NMR (CDCl /TMS) d (ppm): 17.8,
2
1.1, 56.8, 121.4, 122.3, 123.0, 129.3, 134.4, 135.2, 138.0, 138.7,
1
mol% 4
K PO
NC
NC
139.5, 155.6.
3
4
+
PhB(OH)2
Solvent
Temp., Time
Br
Ph
4.3. Synthesis of 2,6-bis[3-(2,6-diisopropylphenyl)imidazolin-2-
ylidene]lutidine disilver dichloride (3b)
5
A mixture of 2b (0.20 g, 0.28 mmol), Ag
and powderous 4 Å molecular sieves in ClCH
2
O (0.13 g, 0.56 mmol),
CH Cl (10 mL) was
Yield (%)b,c
Entry
4
Solvent
Temperature (°C)/time (h)
2
2
heated to reflux for 16 h. The reaction mixture was filtered through
1
2
3
4
5
6
7
8
9
4a
DMSO
MeCN
MeCN
1,4-Dioxane
1,4-Dioxane
Toluene
Toluene
EtOH
120/1
120/1
100/1
120/1
100/1
120/1
100/1
120/1
100/1
100/1
120/1
100/1
100/3
100/3
100/45 (min)
100/20 (min)
100/1
0
82
31 (53)
83
31 (53)
77
64 (24)
53 (38)
26 (56)
Trace (84)
85
70 (20)
77
86
a pad of CeliteÒ and the filtrate was evaporated. The residue was
crystallized from acetone/light petroleum to obtain a light brown
1
solid (0.23 g, quant.). 400 MHz H NMR (CDCl
3
/TMS) d (ppm):
1
.14 (12H, d, J = 6.8 Hz), 1.23 (12H, d, J = 6.8 Hz), 2.36–2.43 (4H,
m), 5.56 (4H, s), 7.05 (2H, s), 7.21–7.27 (6H, m), 7.47 (2H, t,
J = 7.8 Hz), 7.52 (2H, s), 7.78 (1H, t, J = 7.6 Hz). 100 MHz 13C NMR
EtOH
BuOH
3
(CDCl /TMS) d (ppm): 24.3, 24.7, 28.3, 56.7, 121.4, 122.08,
10
11
12
13
14
15
16
17
1
22.13, 124.2, 130.5, 134.6, 138.6, 145.51, 145.43, 155.5.
s
BuOH
s
BuOH
s
4.4. Synthesis of 2,6-bis(3-mesitylimidazolin-2-ylidene)pyridine
disilver dichloride (3c)
BuOH
s
4b
4c
4d
1
BuOH
s
BuOH
80
87
88
s
BuOH
A mixture of 2c (1.2 g, 2.0 mmol), Ag
powderous 4 Å molecular sieves in ClCH
2
O (0.93 g, 4.0 mmol), and
CH Cl (15 mL) was heated
s
BuOH
2
2
a
Reagents: 4-bromobenzonitrile (0.20 mmol), PhB(OH)
2
(0.60 mmol),
4
to reflux for 16 h. The reaction mixture was filtered through a pad
(
0.0020 mmol), K PO (0.40 mmol), and a solvent (1 mL) in a sealed tube.
3
4
of CeliteÒ and the filtrate was evaporated. The residue was crystal-
b
Isolated yield.
Yield of recovered starting material in parentheses.
c
lized from acetone/light petroleum to obtain an off-white solid
1
(
1.2 g, 85%). 400 MHz H NMR (CDCl
3
/TMS) d (ppm): 2.01 (12H,
s), 2.36 (6H, s), 7.00 (4H, s), 7.16 (2H, s), 8.12–8.31 (5H, br).
1
3
complexes in various coupling processes, and preparing a series of
nickel–pincer complexes with various substitution patterns to dis-
close the correlation between the structure of nickel complexes
and their catalytic activities.
1
3
00 MHz C NMR (CDCl /TMS) d (ppm): 17.6, 20.8, 115.2, 121.0,
1
23.6, 129.0, 134.0, 135.0, 139.1, 142.5, 149.2.
4.5. Synthesis of 2,6-bis[3-(2,6-diisopropylphenyl)imidazolin-2-
ylidene]pyridine disilver dichloride (3d)
4
. Experimental
A mixture of 2d (1.4 g, 2.0 mmol), Ag
2
O (0.93 g, 4.0 mmol), and
CH Cl (15 mL) was heated
4.1. General procedure
powderous 4 Å molecular sieves in ClCH
2
2
to reflux for 16 h. The reaction mixture was filtered through a pad
1H NMR spectra were recorded on JEOL JNM-AL400 (400 MHz)
of CeliteÒ and the filtrate was evaporated. The residue was crystal-
spectrometer using tetramethylsilane (TMS) as an internal stan-
dard. Chemical shifts (d) are given from TMS (0 ppm) and coupling
constants are expressed in Hertz (Hz). The following abbreviations
are used: s = singlet, d = doublet, t = triplet, q = quartet, sext = sex-
tet, sept = septet, dd = double doublet, dt = double triplet, m = mul-
tiplet, and br = broad signal. 13C NMR spectra were recorded on
JEOL JNM-AL400 (100 MHz) spectrometer and chemical shifts (d)
lized from acetone/light petroleum to obtain a light brown solid
1
(1.4 g, 87%). 400 MHz H NMR (CDCl
3
/TMS) d (ppm): 1.17 (12H,
d, J = 6.8 Hz), 1.29 (12H, d, J = 6.8 Hz), 2.50 (4H, sept, J = 6.8 Hz),
7.23 (2H, d, J = 1.6 Hz), 7.31 (4H, d, J = 7.8 Hz), 7.52 (2H, t,
J = 7.8 Hz), 8.17–8.23 (3H, m), 8.33 (2H, br). 100 MHz 13C NMR
(CDCl /TMS) d (ppm): 24.2, 24.4, 28.1, 115.5, 120.8, 124.1, 124.9,
3
130.5, 134.4, 142.6, 145.2, 149.7, 172.5.
1
3
13
3 3 2
are given from CDCl (77.0 ppm) and ( CD ) SO (39.7 ppm).
Mass spectra and high resolution mass spectra were measured
on JEOL JMS-DX303 and MS-AX500 instruments, respectively. Ele-
mental analyses were performed by Yanaco CHN CORDER MT-6. IR
spectra were recorded on a SHIMADZU FTIR-8400. Melting points
were measured with a Yazawa micro melting point apparatus
and uncorrected. Compounds 2a–d were prepared according to
the literature [36].
4.6. Synthesis of [2,6-bis(3-mesitylimidazolin-2-
ylidene)lutidine]chloronickel tetrafluoroborate (4a)
To a suspension of NiCl
(120 mL) was added slowly a solution of 3a (0.30 g, 0.39 mmol)
in CH Cl (30 mL) and the mixture was stirred at room tempera-
ture for 24 h. To the mixture was added a solution of AgBF
0.080 g, 0.41 mmol) in CH Cl (30 mL) and stirred at room tem-
2 2 2
(DME) (0.091 g, 0.41 mmol) in CH Cl
2
2
4
(
2
2
4
.2. Synthesis of 2,6-bis(3-mesitylimidazolin-2-ylidene)lutidine
perature for 16 h. The reaction mixture was filtered through a
disilver dichloride (3a)
pad of CeliteÒ and the filtrate was evaporated. The resulting solid
was crystallized from CH
solid (0.26 g, quant.). The product was purified by recrystallization
from CH Cl /light petroleum to give yellow needles. M.p.: > 250 °C.
400 MHz H NMR (DMSO-d ) d (ppm): 1.85 (6H, s), 2.05 (6H, s),
6
2.25 (6H, s), 5.82 (2H, d, J = 15.8 Hz), 6.15 (2 H, d, J = 15.8 Hz),
2 2
Cl /light petroleum to obtain an yellow
A mixture of 2a (0.50 g, 0.79 mmol), Ag
and powderous 4 Å molecular sieves in ClCH
2
O (0.91 g, 3.9 mmol),
CH Cl (8 mL) was
2
2
2
2
1
heated to reflux for 16 h. The reaction mixture was filtered through
Ò
a pad of Celite and the filtrate was evaporated. The residue was
crystallized from acetone/light petroleum to obtain a light brown
6.84 (2H, s), 6.84 (2H, s), 7.01 (2H, s), 7.20 (2H, s), 7.81 (2H, d,
J = 7.1 Hz), 8.14 (1H, t, J = 7.1 Hz). 100 MHz C NMR (DMSO-d ) d
6
1
13
solid (0.56 g, 94%). 400 MHz H NMR (CDCl
3
/TMS) d (ppm): 1.99
(
12H, s), 2.34 (6H, s), 5.52 (4H, s), 6.96 (4H, s), 6.99 (2H, d,
(ppm): 17.7, 18.1, 20.5, 53.6, 121.8, 124.6, 125.2, 128.5, 128.7,

K. Inamoto et al. / Journal of Organometallic Chemistry 694 (2009) 389–396
393
Table 4
Suzuki–Miyaura coupling of aryl halides with phenylboronic acid.
a
1
mol% 4
K PO
3
4
Ar
+
PhB(OH)2
Ar
-9
s
BuOH
X
Ph
Temp., Time
5
Entry
1
Ar–X
4
Temperature (°C)/time (h)
Product
Yield (%)b,c
83
4a
120/2
6
Ac
2
3
4
4b
4c
4d
75
76
75
120/2
100/3
Br
100/2
5
6
7
8
s
7
8
9
5
9
6
64 (27)
63
50
73 (16)
BuO C
2
4a
120/3
120/4
100/2
100/2
4
4
4
b
c
d
Br
9
4a
4b
4c
4d
67
61
57
38
MeO
120/2
120/2
120/2
120/1
10
11
12
Br
1
1
3
4
4a
4b
100/5
100/5
100/2
100/1
85
85
97
94
Br
Cl
4
c
1
1
5
6
N
4d
17
18
19
20
4a
4b
4c
4d
100/3
100/3
100/2
100/2
71
77
74
67
NC
Cl
21
22
23
24
4a
4b
4c
4d
100/5
100/5
100/3
100/3
79
76
79
77
N
25
26
27
28
4a
4b
4c
4d
120/4
120/4
120/4
120/3
86
51
76
48
Ac
Cl
a
b
c
s
2 3 4
Reagents: an aryl halide (0.20 mmol), PhB(OH) (0.60 mmol), 4 (0.0020 mmol), K PO (0.40 mmol), and BuOH (1 mL) in a sealed tube.
Isolated yield.
Yield of recovered starting material in parentheses.
1
C
5
33.3, 134.6, 135.3, 137.4, 141.0, 156.0, 164.6. Anal. Calc. for
33BClF Ni: C, 56.70; H, 5.07; N, 10.67. Found: C, 56.60; H,
.09; N, 10.63%.
(1H, t, J = 7.7 Hz). 100 MHz 13C NMR (DMSO-d
23.7, 24.1, 25.3, 28.1, 28.2, 53.5, 121.5, 123.0, 123.5, 125.1, 126.4,
129.3, 134.9, 141.1, 144.1, 145.6, 155.7, 164.3. Anal. Calc. for
6
) d (ppm): 22.2,
31
H
4
N
5
C
37
H45BClF
4 5
N Ni: C, 59.99; H, 6.12; N, 9.46. Found: C, 59.74; H,
4.7. Synthesis of {2,6-bis[3-(2,6-diisopropylphenyl)imidazol-2-
6.24; N, 9.40%.
ylidene]lutidine}chloronickel tetrafluoroborate (4b)
4.8. Synthesis of [2,6-bis(3-mesitylimidazolin-2-
To a suspension of NiCl
120 mL) was added slowly a solution of 3b (0.29 g, 0.34 mmol)
in CH Cl (30 mL) and the mixture was stirred at room tempera-
ture for 24 h. To the mixture was added AgBF (0.070 g, 0.36 mmol)
2 2 2
(DME) (0.079 g, 0.36 mmol) in CH Cl
ylidene)pyridine]chloronickel tetrafluoroborate (4c)
(
2
2
To a solution of NiCl
(120 mL) was added slowly a solution of 3c (0.30 g, 0.41 mmol)
in CH Cl (30 mL) and the mixture was stirred at room tempera-
ture for 24 h. To the mixture was added AgBF (0.083 g, 0.43 mmol)
2 2 2
(DME) (0.095 g, 0.43 mmol) in CH Cl
4
and stirred at room temperature for 16 h. The reaction mixture was
2
2
filtered through a pad of CeliteÒ and the filtrate was evaporated.
4
The resulting solid was crystallized from CH
to obtain an yellow solid (0.20 g, 78%). The product was purified
by recrystallization from CH Cl /light petroleum to give yellow
needles. M.p.: > 250 °C. 400 MHz H NMR (DMSO-d
.71 (6H, d, J = 6.9 Hz), 0.99 (6H, d, J = 6.9 Hz), 1.02 (6H, d,
J = 6.9 Hz), 1.55 (6H, d, J = 6.9 Hz), 2.08 (2H, sept, J = 6.9 Hz), 2.32
2H, sept, J = 6.9 Hz), 5.85 (2H, d, J = 15.6 Hz), 6.04 (2H, d,
2
Cl
2
/light petroleum
and stirred at room temperature for 16 h. The reaction mixture was
filtered through a pad of CeliteÒ and the filtrate was evaporated.
2
2
The resulting solid was crystallized from CH
to obtain an yellow solid (0.26 g, 99%). The product was purified
by recrystallization from CH Cl /light petroleum to give yellow
needles. M.p.: > 250 °C. 400 MHz H NMR (DMSO-d
2 2
Cl /light petroleum
1
6
) d (ppm):
0
2
2
1
6
) d (ppm):
(
1.99 (12H, s), 2.21 (6H, s), 6.87 (4H, s), 7.53 (2H, s), 7.99 (2H, d,
J = 15.6 Hz), 7.16 (2H, d, J = 7.9 Hz), 7.28–7.30 (4H, m), 7.38 (2H,
t, J = 7.9 Hz), 7.68 (2H, d, J = 1.6 Hz), 7.85 (2H, d, J = 7.7 Hz), 8.20
J = 7.8 Hz), 8.54 (1H, t, J = 7.8 Hz), 8.67 (2H, s). 100 MHz 13C NMR
6
(DMSO-d ) d (ppm): 17.3, 20.5, 108.2, 117.5, 127.0, 128.2, 129.0,

3
94
K. Inamoto et al. / Journal of Organometallic Chemistry 694 (2009) 389–396
Table 5
Suzuki–Miyaura coupling of aryl halides with various boronic acids.a
The resulting solid was crystallized from CH
to obtain an yellow solid (0.23 g, 88%). The product was purified
by recrystallization from CH Cl /light petroleum to give yellow
6
needles. M.p.: > 250 °C. 400 MHz H NMR (DMSO-d ) d (ppm):
2
Cl /light petroleum
2
2
2
1
1
mol% 4d
K PO
1.04 (12H, d, J = 6.8 Hz), 1.13 (12H, d, J = 6.8 Hz), 2.42–2.49 (4H,
m), 7.14 (4H, d, J = 7.7 Hz), 7.32 (2H, t, J = 7.7 Hz), 7.69 (2H, d,
J = 1.6 Hz), 7.93 (2H, d, J = 8.4 Hz), 8.53–8.56 (3H, m). 100 MHz
3
4
Ar
+
RB(OH)2
Ar
,8-16
s
BuOH
Br
R
1
00-120 ºC, 2-3 h
1
3
5
C NMR (DMSO-d
23.1, 128.2, 129.7, 133.2, 144.0, 146.2, 150.6, 162.4. Anal. Calc.
for C35 41BClF Ni: C, 58.98; H, 5.80; N, 9.83, Found: C, 58.63;
H, 6.00; N, 9.55%.
6
) d (ppm): 22.9, 24.1, 27.9, 108.5, 117.1,
1
H
4 5
N
Entry
1
Ar–X
RB(OH)
2
Product
Yield (%)b
69
MeO
8
4.10. X-ray diffraction studies
Br
B(OH)2
B(OH)2
B(OH)2
B(OH)2
X-ray diffraction data of the crystal were collected with a Riga-
ku Saturn CCD diffractometer using a graphite monochromated Mo
NC
MeO
NC
2
3
4
10
5
77
49
42
K
a
(k = 0.71070 Å) at ꢁ100 °C. The data were corrected for Lorentz
and polarization effects, and a numerical absorption correction was
applied using a refined crystal shape. The structure was solved by
direct methods (SIR 2004) [40] and expanded using Fourier tech-
niques. All data were refined by full-matrix least-squares minimi-
Br
Br
Br
P
2
zations of (F
o
ꢁ F
c
) with anisotropic thermal parameters for all
NC
non-hydrogen atoms. The hydrogen atoms were assigned based
on expected geometry and a riding model was used during the
refinement process. A summary of the crystallographic data is gi-
ven in Table 1.
11
N
5
6
9
29
N
4.11. Typical procedure for the nickel-catalyzed Suzuki–Miyaura
coupling reactions (Table 3, entry 13)
Br
Br
B(OH)2
NC
Ac
12
82d
A mixture of 4-bromobenzonitrile (36.4 mg, 0.20 mmol), phen-
B(OH)2
ylboronic acid (73.2 mg, 0.60 mmol), 4a (1.3 mg, 0.0020 mmol),
Br
Br
s
3
K PO
4
(86.0 mg, 0.40 mmol), and BuOH (1 mL) was heated to
1
00 °C for 3 h. After cooling to room temperature, the reaction mix-
ture was treated with H O (15 mL) and extracted with AcOEt
15 mL ꢂ 3). The combined extracts were washed with saturated
aqueous NaCl (15 mL ꢂ 3) and the organic layer was dried over
MgSO . The solvent was removed under reduced pressure and
7
8
13
14
15
16
65d
48d
76d
80d
2
B(OH)2
(
4
B(OH)2
the residue was purified by silica gel column chromatography
using hexane/AcOEt (19:1) as an eluent to obtain 5 as a colorless
solid (27.6 mg, 77%).
N
NC
9c
B(OH)2
4-Cyanobiphenyl (5): M.p. 85–86 °C (colorless prisms from hex-
Br
Br
ꢁ1
ane/AcOEt, lit. [41] m.p. 84–86 °C. IR
m
(film) cm : 2228. 400 MHz
1
Ac
H NMR (CDCl
J = 7.2, 1.2 Hz), 7.66–7.73 (4H, m). 100 MHz C NMR (CDCl
TMS) d (ppm): 110.8, 118.9, 127.1, 127.6, 128.6, 129.0, 132.5,
3
/TMS) d (ppm): 7.40–7.50 (3H, m), 7.58 (2H, dd,
13
1
0
3
/
B(OH)2
+
1
39.0, 145.5. EI-MS m/z (relative intensity): 179 (M , 100%). HRMS
a
Reagents: an aryl bromide (0.10 mmol), RB(OH)
2
(0.30 mmol), 4d (0.0010
(0.20 mmol), and BuOH (0.5 mL) in a sealed tube.
s
Calcd. for C13 N: 179.0735; found: 179.0739.
H
9
mmol), K
3
PO
4
b
4-Acetylbiphenyl (6): M.p. 121–122 °C (colorless needles from
Isolated yield.
c
s
ꢁ1
1
,4-Dioxane was used instead of BuOH.
E-Isomer exclusively formed.
hexane/AcOEt, lit. [41] m.p. 117–119 °C). IR
m
(film) cm : 1680.
d
1
4
00 MHz H NMR (CDCl
3
/TMS) d (ppm): 2.64 (3H, s), 7.40 (1H, t,
J = 7.8 Hz), 7.47 (2H, t, J = 7.8 Hz), 7.62 (2H, d, J = 7.8 Hz), 7.68
(
(
1
2H, d, J = 8.4 Hz), 8.03 (2H, d, J = 8.4 Hz). 100 MHz 13C NMR
1
C
5
33.5,
29BClF
4.11; H, 4.80; N, 10.89%.
133.7,
137.9,
146.1,
150.3.
Anal.
Calc.
for
CDCl /TMS) d (ppm): 26.9, 127.26, 127.31, 128.3, 128.96, 129.00,
35.9, 139.9, 145.8, 197.7. EI-MS m/z (relative intensity): 196
3
29
H
4
N
5
Ni ꢀ H
2
O: C, 53.87; H, 4.83; N, 10.83, Found: C,
+
+
(
1
M , 64%), 181 (M ꢁ15, 100%). HRMS Calcd. for
14
C H12O:
96.0888; found: 196.0884.
-sec-Butoxycarbonylbiphenyl (7): IR
00 MHz H NMR (CDCl
3
4.9. Synthesis of {2,6-bis[3-(2,6-diisopropylphenyl)imidazol-2-
4
m
(film) cmꢁ1: 1279, 1713.
/TMS) d (ppm): 0.99 (3H, t, J = 6.3 Hz),
.35 (3H, d, J = 6.3 Hz), 1.63–1.82 (2H, m), 5.12 (1H, sext,
ylidene]pyridine}chloronickel tetrafluoroborate (4d)
1
4
1
To a suspension of NiCl
120 mL) was added slowly a solution of 3d (0.30 g, 0.37 mmol)
in CH Cl (30 mL) and the mixture was stirred at room tempera-
ture for 24 h. To the mixture was added AgBF (0.075 g, 0.39 mmol)
2 2 2
(DME) (0.085 g, 0.39 mmol) in CH Cl
J = 6.3 Hz), 7.38 (1H, tt, J = 7.4, 1.6 Hz), 7.46 (2H, t, J = 7.4 Hz),
.60–7.66 (4H, m), 8.11 (2H, dt, J = 8.4, 1.8 Hz). 100 MHz 13
NMR (CDCl /TMS) d (ppm): 9.8, 19.7, 29.0, 72.9, 126.9, 127.2,
28.0, 128.8, 129.6, 129.9, 140.0, 145.3, 166.0. EI-MS m/z (relative
(
7
C
2
2
3
4
1
and stirred at room temperature for 16 h. The reaction mixture was
+
+
+
filtered through a pad of CeliteÒ and the filtrate was evaporated.
intensity): 254 (M , 37%), 225 (M ꢁ29, 2%), 198 (M ꢁ56, 100%),

K. Inamoto et al. / Journal of Organometallic Chemistry 694 (2009) 389–396
395
+
1
2
81 (M ꢁ73, 61%). HRMS Calcd. for C17
H
18
O
2
: 254.1307; found:
1.51 (2H, sext, J = 7.2 Hz), 2.20–2.25 (2H, m), 6.33–6.42 (2H, m),
13
54.1306.
7.40 (2H, d, J = 8.4 Hz), 7.56 (2H, d, J = 8.4 Hz). 100 MHz
NMR (CDCl /TMS) d (ppm): 13.8, 22.3, 35.2, 109.8, 119.1, 126.3,
128.5, 132.2, 135.2, 142.3. EI-MS m/z (relative intensity): 171
C
4
-Methoxybiphenyl (8): M.p. 86–87 °C (colorless prisms from
3
ꢁ
1
hexane/AcOEt, lit. [41] m.p. 85ꢁ87 °C). IR
m
(film) cm : 1609,
1
+
+
+
1
(
7
1
(
(
036. 400 MHz H NMR (CDCl
3
/TMS) d (ppm): 3.83 (3H, s), 6.96
(M ꢁ15, 60%), 142 (M ꢁ29, 74%), 129 (M ꢁ42, 100%), 115
+
2H, d, J = 8.8 Hz), 7.29 (1H, t, J = 7.5 Hz), 7.40 (2H, t, J = 7.5 Hz),
(M ꢁ56, 19%). HRMS Calcd. for C12
H
13N: 171.1048; found:
.51–7.55 (4H, m). 100 MHz 13C NMR (CDCl
/TMS) d (ppm): 55.3,
14.1, 126.56, 126.64, 128.0, 128.6, 133.7, 140.7, 159.0. EI-MS m/z
171.1029.
3
ꢁ
1-(E)-Pentenyl-4-acetophenone (16): IR
1682. 400 MHz H NMR (CDCl /TMS) d (ppm): 0.96 (3H, t,
3
m
(film) cm 1: 1603,
+
+
1
relative intensity): 184 (M , 100%), 169 (M ꢁ15, 43%), 141
+
M ꢁ43, 26%). HRMS Calcd. for C13
84.0886.
-Phenylpyridine (9): IR
CDCl
.58 (2H, d, J = 7.4 Hz), 7.87 (1H, dt, J = 7.8, 1.9 Hz), 8.59 (1H, d,
H
12O: 184.0888; found:
J = 7.2 Hz), 1.52 (2H, sext, J = 7.2 Hz), 2.22 (2H, q, J = 7.2 Hz), 2.58
1
(3H, s), 6.35–6.44 (2H, m), 7.41 (2H, d, J 8 8.4 Hz), 7.88 (2H, d,
(neat) cm 1: 3396. 400 MHz H NMR
ꢁ
1
13
3
m
3
J = 8.4 Hz). 100 MHz C NMR (CDCl /TMS) d (ppm): 13.8, 22.4,
(
7
3
/TMS) d (ppm): 7.35–7.43 (2H, m), 7.48 (2H, t, J = 7.4 Hz),
26.6, 35.3, 125.8, 128.7, 129.0, 134.2, 135.3, 142.6, 197.5. EI-MS
+
+
m/z (relative intensity): 188 (M , 100%), 173 (M ꢁ15, 88%), 146
13
+ + +
J = 4.0 Hz), 8.85 (1H, s). 100 MHz C NMR (CDCl
23.4, 127.1, 128.0, 129.0, 134.2, 136.5, 137.7, 148.2, 148.3. EI-
MS m/z (relative intensity): 155 (M , 100%). HRMS Calcd. for
3
/TMS) d (ppm):
(M ꢁ42, 19%), 131 (M ꢁ57, 19%), 43 (M ꢁ145, 36%). HRMS Calcd.
for C13 16O: 188.1201; found: 188.1208.
1
H
+
C
11
H
9
N: 155.0735; found: 155.0738.
Acknowledgement
0
4-Cyano-4 -methoxybiphenyl (10): M.p. 101–102 °C (colorless
plates from hexane/AcOEt, lit. [42] m.p. 103–104 °C). IR
m
(film)
/TMS) d (ppm):
.86 (3H, s), 7.00 (2H, d, J = 8.8 Hz), 7.53 (2H, d, J = 8.8 Hz), 7.63
This work was supported in part by a Grant-in-Aid for JSPS Fel-
lows from the Japan Society for the Promotion of Science (JSPS).
ꢁ1
1
cm : 1038, 1607, 2224. 400 MHz H NMR (CDCl
3
3
1
3
(
(
1
2H, d, J = 8.0 Hz), 7.69 (2H, d, J = 8.0 Hz). 100 MHz C NMR
CDCl /TMS) d (ppm): 55.4, 110.1, 114.6, 119.1, 127.1, 128.3,
31.5, 132.6, 145.2, 160.2. EI-MS m/z (relative intensity): 209
Appendix A. Supplementary material
3
+
+
+
CCDC 701129, 701130, 701131 and 701132 contains the sup-
plementary crystallographic data for 4a, 4b, 4c and 4d. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2008.11.003.
(
M , 100%), 194 (M ꢁ15, 29%), 166 (M ꢁ43, 20%). HRMS Calcd.
for C14 11NO: 209.0841; found: 209.0826.
-(4-Cyanophenyl)pyridine (11): M.p. 94–96 °C (colorless
prisms from hexane/AcOEt, lit. [43] m.p. 95–96 °C). IR (film)
/TMS) d (ppm): 7.42
1H, t, J = 6.7 Hz), 7.69 (2H, d, J = 8.2 Hz), 7.78 (2H, d, J = 8.2 Hz),
H
3
m
cm : 2226, 3358. 400 MHz 1H NMR (CDCl
(
ꢁ
1
3
1
3
7
.89 (1H, d, J = 6.7 Hz), 8.67 (1H, s), 8.86 (1H, s). 100 MHz
C
NMR (CDCl
3
/TMS) d (ppm): 111.9, 118.5, 123.7, 127.7, 132.8,
References
1
1
1
34.4, 134.7, 142.2, 148.1, 149.6. EI-MS m/z (relative intensity):
+
[1] D. Benito-Garagorri, K. Kirchner, Acc. Chem. Res. 41 (2008) 201.
80 (M , 100%). HRMS Calcd. for C12
H
8
2
N : 180.0688; found:
[
[
2] H. Nishiyama, Chem. Soc. Rev. 36 (2007) 1133.
3] K.J. Szabó, Synlett (2006) 811.
80.0670.
(
E)-4-Cyanostilbene (12): M.p. 111–113 °C (colorless plates from
[4] M.E. van der Boom, D. Milstein, Chem. Rev. 103 (2003) 1759.
[5] J.T. Singleton, Tetrahedron 59 (2003) 1837.
ꢁ1
hexane/AcOEt, lit. [44] m.p. 114–116 °C). IR
m
(film) cm : 1601,
/TMS) d (ppm): 7.07 (1H, d,
J = 16.4 Hz), 7.20 (1H, d, J = 16.4 Hz), 7.31 (1H, t, J = 7.5 Hz), 7.38
2H, t, J = 7.5 Hz), 7.52 (2H, d, J = 7.5 Hz), 7.56 (2H, d, J = 8.4 Hz),
[
[
6] M. Albrecht, G. van Koten, Angew. Chem., Int. Ed. 40 (2001) 3750.
7] D. Morales-Morales, C.M. Jensen, The Chemistry of Pincer Compounds, Elsevier,
Oxford, 2006.
1
2
226. 400 MHz H NMR (CDCl
3
[
8] D. Pugh, A.A. Danopoulos, Coord. Chem. Rev. 251 (2007) 610.
(
.62 (2H, d, J = 8.4 Hz). 100 MHz 1 C NMR (CDCl
3
[9] E. Peris, R.H. Crabtree, Coord. Chem. Rev. 248 (2004) 2239.
10] T. Tu, J. Malineni, K.H. Dötz, Adv. Synth. Catal. 350 (2008) 1791.
7
1
1
3
/TMS) d (ppm):
[
10.5, 118.9, 126.6, 126.7, 126.8, 128.5, 128.7, 132.3, 132.4,
36.1, 141.7. EI-MS m/z (relative intensity): 205 (M , 100%). HRMS
Calcd. for C15
[11] H. Meguro, T. Koizumi, T. Yamamoto, T. Kanbara, J. Organomet. Chem. 693
2008) 1109.
+
(
[
[
12] J. Aydin, K.J. Szabó, Org. Lett. 10 (2008) 2881.
13] M. Minakawa, K. Takenaka, Y. Uozumi, Eur. J. Inorg. Chem. (2007) 1629.
[14] N.C. Mehendale, J.R.A. Sietsma, K.P. de Jong, C.A. van Walree, R.J.M.K. Gebbink,
G. van Koten, Adv. Synth. Catal. 349 (2007) 2619.
[15] S. Yamaguchi, T. Katoh, H. Shinokubo, A. Osuka, J. Am. Chem. Soc. 129 (2007)
H11N: 205.0892; found: 205.0903.
(
E)-4-Acetylstilbene (13): M.p. 139–142 °C (colorless prisms
ꢁ
1
from hexane/AcOEt, lit. [44] m.p. 141–144 °C). IR
601, 1678. 400 MHz H NMR (CDCl
.12 (1H, d, J = 16.4 Hz), 7.22 (1H, d, J = 16.4 Hz), 7.29 (1H, t,
m (film) cm :
1
1
7
3
/TMS) d (ppm): 2.60 (3H, s),
6392.
[
16] D. Pugh, A. Boyle, A.A. Danopoulos, Dalton Trans. (2008) 1087.
J = 7.1 Hz), 7.37 (2H, t, J = 7.1 Hz), 7.53 (2H, dd, J = 7.1, 1.2 Hz),
[17] C.A. Kruithof, H.P. Dijkstra, M. Lutz, A.L. Spek, R.J.M.K. Gebbink, G. van Koten,
Organometallics 27 (2008) 4928.
1
3
7
(
1
.58 (2H, d, J = 8.2 Hz), 7.94 (2H, d, J 8 8.2 Hz). 100 MHz C NMR
CDCl /TMS) d (ppm): 26.6, 126.4, 126.7, 127.3, 128.2, 128.7,
28.8, 131.4, 135.8, 136.6, 141.9, 197.3. EI-MS m/z (relative inten-
[
[
18] A. Bugarin, B.T. Connell, Organometallics 27 (2008) 4357.
19] K.A. Kozhanov, M.P. Bubnov, V.K. Cherkasov, N.N. Vavilina, L.Y. Efremova, O.I.
Artyushin, I.L. Odinets, G.A. Abakumov, Dalton Trans. (2008) 2849.
3
+
+
[20] Z. Csok, O. Vechorkin, S.B. Harkins, R. Scopelliti, X. Hu, J. Am. Chem. Soc. 130
2008) 8156.
sity): 222 (M , 99%), 207 (M ꢁ15, 100%). HRMS Calcd. for C16
H14O:
(
2
22.1045; found: 222.1060.
E)-1-Phenyl-2-(3-pyridyl)ethylene (14): IR
[
21] D. Benito-Garagorri, E. Becker, J. Wiedermann, W. Lackner, M. Pollak, K.
Mereiter, J. Kisala, K. Kirchner, Organometallics 25 (2006) 1900.
22] H. Behrens, R. Fröhlich, E.-U. Würthwein, Eur. J. Org. Chem. (2005) 3891.
23] L. Wang, Z.-X. Wang, Org. Lett. 9 (2007) 4335.
(
m
(film) cmꢁ1: 3393.
3
00 MHz H NMR (CDCl /TMS) d (ppm): 7.06 (1H, d, J = 16.4 Hz),
1
[
[
[
4
7
7
.16 (1H, d, J = 16.4 Hz), 7.25–7.31 (2H, m), 7.37 (2H, t, J 8
.2 Hz), 7.52 (2H, d, J = 7.2 Hz), 7.82 (1H, d, J = 8.0 Hz), 8.48 (1H,
24] V. Pandarus, D. Zargarian, Organometallics 26 (2007) 4321.
[25] L.C. Liang, P.-S. Chien, J.M. Lin, M.H. Huang, Y.L. Huang, J.H. Liao,
Organometallics 25 (2006) 1399.
13
d, J = 4.0 Hz), 8.72 (1H, s). 100 MHz
3
C NMR (CDCl /TMS) d
[
[
26] L. Fan, O.V. Ozerov, Chem. Commun. (2005) 4450.
27] O. Baldovino-Pantaleón, S. Hernández-Ortega, D. Morales-Morales, Adv. Synth.
Catal. 348 (2006) 236.
(
ppm): 123.4, 124.8, 126.6, 128.1, 128.7 (2 carbons), 130.7, 132.6,
+
1
1
1
32.9, 136.5, 148.4. EI-MS m/z (relative intensity): 181 (M , 59%),
+
80 (M ꢁ1, 100%). HRMS Calcd. for C13
H
11N: 181.0892; found:
[28] J.S. Fossey, C.J. Richards, J. Organomet. Chem. 689 (2004) 3056.
[
[
29] R.A. Gossage, L.A. van de Kuil, G. van Koten, Acc. Chem. Res. 31 (1998) 423.
30] C.-Y. Liao, K.-T. Chan, Y.-C. Chang, C.-Y. Chen, C.-Y. Tu, C.-H. Hu, H.M. Lee,
Organometallics 26 (2007) 5826.
81.0881.
1
-(E)-Pentenyl-4-benzonitrile (15): IR
00 MHz H NMR (CDCl
m
(film) cm 1: 1651, 2224.
ꢁ
1
4
3
/TMS) d (ppm): 0.96 (3H, t, J = 7.2 Hz),
[31] Z. Xi, X. Zhang, W. Chen, S. Fu, D. Wang, Organometallics 26 (2007) 6636.

3
96
K. Inamoto et al. / Journal of Organometallic Chemistry 694 (2009) 389–396
[
32] C.-C. Lee, W.-C. Ke, K.-T. Chan, C.-L. Lai, C.-H. Hu, H.M. Lee, Chem. Eur. J. 13
2007) 582.
33] C. Zhong, T. Sasaki, M. Tada, Y. Iwasawa, J. Catal. 242 (2006) 357.
34] K. Inamoto, J. Kuroda, K. Hiroya, Y. Noda, M. Watanabe, T. Sakamoto,
Organometallics 25 (2006) 3095.
35] K. Inamoto, J. Kuroda, T. Sakamoto, K. Hiroya, Synthesis (2007) 2853.
36] A.A. Danopoulos, A.A.D. Tulloch, S. Winston, G. Eastham, M.B. Hursthouse,
Dalton Trans. (2003) 1009.
[39] Shorter reaction time in the reaction catalyzed by 4a and 4b resulted in the
decreased yield of the coupling product 5 and the recovery of the starting
material.
[40] M.C. Burla, R. Caliandro, M. Camalli, B. Carrozzini, G.L. Cascarano, L.
De Caro, C. Giacovazzo, G. Polidori, R. Spagna, J. Appl. Crystallogr. 38
(2005) 381.
(
[
[
[
[
[41] V. Percec, G.M. Golding, J. Smidrkal, O. Weichold, J. Org. Chem. 69 (2004)
3447.
[
[
37] During this study, Danopoulos reported the synthesis of the nickel–pincer
complex similar to 4d, see Ref. [16].
38] Use of a reduced amount of the boronic acid led to a decreased yield and/or
longer reaction time. In addition, the major byproducts arising from the
boronic acids are the homo-coupling products (biphenyls), yields of which are
dependent on the reaction conditions employed (around 10–20%).
[42] S.-D. Cho, H.-K. Kim, H.-S. Yim, M.-R. Kim, J.-K. Lee, J.-J. Kimd, Y.-J. Yoond,
Tetrahedron 63 (2007) 1345.
[43] J. Zhang, L. Zhao, M. Song, T.C.W. Mak, Y. Wu, J. Organomet. Chem. 691 (2006)
1301.
[44] B. Mu, T. Li, W. Xu, G. Zeng, P. Liua, Y. Wu, Tetrahedron 63 (2007) 11475.