Synthesis and catalytic activity of nickel(II) complexes of CNC pincer-type N-heterocyclic carbene ligands

Article abstract of DOI:10.1016/j.jorganchem.2015.04.019

Air- and moisture-stable nickel(II) complexes 2a-c of CNC pincer-type N-heterocyclic carbene ligands have been prepared from the corresponding imidazolium salts by carbene-transfer reaction of a silver-NHC complex with Ni(DME)Cl₂ (DME = dimethoxylethane). Pincer complexes 2a-c are characterized by mass and NMR spectroscopy. The structure of 2a is also identified by X-ray diffraction analysis. Pincer complex 2a has been shown to be active catalyst for the Suzuki coupling reactions.

Full text of DOI:10.1016/j.jorganchem.2015.04.019

Accepted Manuscript
Synthesis and catalytic activity of nickel(II) complexes of CNC pincer-type N-
heterocyclic carbene ligands
Shuchao Wang, Fang Ren, Yuping Qiu, Meiming Luo
PII:
S0022-328X(15)00220-X
10.1016/j.jorganchem.2015.04.019
JOM 19005
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 3 December 2014
Revised Date: 27 March 2015
Accepted Date: 6 April 2015
Please cite this article as: S. Wang, F. Ren, Y. Qiu, M. Luo, Synthesis and catalytic activity of nickel(II)
complexes of CNC pincer-type N-heterocyclic carbene ligands, Journal of Organometallic Chemistry
(2015), doi: 10.1016/j.jorganchem.2015.04.019.
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ACCEPTED MANUSCRIPT
Graphical abstract: synopsis
A new type of nickel(II) complexes containing CNC pincer-type bis-NHC ligands with an anionic
diarylamindo backbone has been synthesized and characterized.

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Synthesis and catalytic activity of nickel(II) complexes of
CNC pincer-type N-heterocyclic carbene ligands
Shuchao Wang, Fang Ren, Yuping Qiu, Meiming Luo*
Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of
Chemistry, Sichuan University, Chengdu 610064, People’s Republic of China
*Corresponding author, Tel. & Fax: 86-28-85462021
E-mail address: luomm@scu.edu.cn
Abstract
Air- and moisture-stable nickel(II) complexes 2a-c of CNC pincer-type N-heterocyclic
carbene ligands have been prepared from the corresponding imidazolium salts by
carbene-transfer reaction of a silver-NHC complex with Ni(DME)Cl2 (DME =
dimethoxylethane). Pincer complexes 2a-c are characterized by mass and NMR spectroscopy.
The structure of 2a is also identified by X-ray diffraction analysis. Pincer complex 2a has
been shown to be active catalyst for the Suzuki coupling reactions.
Keywords
Nickel complex; pincer-type ligand; N-heterocyclic carbene; Ni(II)-N-heterocyclic carbene
complex; Suzuki reaction

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1. Introduction
Transition metal-catalyzed Suzuki coupling reactions represent a powerful synthetic
method for the synthesis of biaryl compounds [1] which are important components in
materials science, natural products, and medicines [2]. The easy availability of boron reagents,
broad functional group tolerance, and general applicability of the reaction contributed to its
increasing importance in both academic research and industrial production [3]. In this field,
the catalysts are largely dominated by palladium and nickel complexes due to their high
catalytic activity for a wide range of substrates and high functional group tolerance [4].
However, in the majority of cases, these common catalysts are hampered by (1) the high cost
of palladium and related ligands; (2) most of the so far reported nickel catalysts use nickel(0)
such as Ni(COD) , Ni(PPh ) , etc. as catalysts, and such nickel sources would be difficult to
2
3 4
handle because of their toxicity and thermal instability [5]; (3) nickel (II) complexes with
expensive and air-sensitive phosphine ligands [6,7] or AgBF for the necessary ion-exchange
4
[
8]; (4) a high loading of the nickel complex (usually 3-10 mol% is required) [9], which limits
their use in industrial applications. Therefore, development of inexpensive, efficient and
practical Ni-based catalysts for Suzuki coupling reactions is desirable.
During the past decades, nickel-pincer complexes based on CNC [8,10], NNN [11], PNP
[
12], and PCP [13] ligands have attracted considerable attention, and been widely employed
as versatile active catalysts in organic synthesis. In addition, a pincer ligand with one or two
N-heterocyclic carbene (NHC) donors would combine the unique properties of the NHC
ligand and amplify the high thermal stability of pincer catalysts. For these reasons, much
effort has been devoted to the synthesis and structural characterization of nickel-pincer
complexes containing NHC ligands. However, nickel complexes of CNC pincer-type
bis-NHC ligands have rarely been studied. So far, only a few CNC-type pincer complexes of

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nickel with pyridine backbone have been reported recently [8,10]. Although palladium and
rhodium complexes of CNC pincer-type bis-NHC ligands with an anionic amido backbone
have been reported exhibiting unique structural feature and excellent catalytic activity [14],
nickel complex of CNC pincer-type bis-NHC ligands with an anionic amido backbone is still
unprecedented. We previously reported palladium(II) complexes of CNC pincer-type
bis-NHC ligands with an anionic diarylamido backbone and their high catalytic activity in
Suzuki coupling reactions [14c]. As a continuation, here in this paper we describe the
synthesis and structural characterization of nickel(II) complexes containing CNC pincer-type
bis-NHC ligands with an anionic amido backbone. These pincer nickel complexes have been
found to be highly efficient catalysts for the Suzuki coupling reactions.
2
. Results and discussion
2.1. Preparation of bis-NHC-Ni(II) complexes
Imidazolium salts 1a-c were prepared by our previously reported procedures [14c]. Like
the synthesis of palladium(II) complexes [14c], complexes 2a-c were successfully obtained by
the carbene-transfer reaction of the corresponding silver-NHC complex with Ni(DME)Cl2
(
DME = dimethoxylethane ) (Scheme 1). These complexes were isolated as air- and
moisture-stable purple crystalline solids. The formation of 2a-c is confirmed by comparing
1
13
their H and CNMR spectra with those of imidazolium salt precursors 1a-c. The absence of
1
the NH and the NC(H)N proton resonances in the H NMR spectra demonstrates that the
ligand is coordinated to nickel in a monoanionic bis-NHC form. Notably, the signals for the
13
carbene carbon atoms of 2a-c in the C NMR spectra appear at 161.9-160.9 ppm, which are
1
3
characteristic peaks for nickel-carbene complexes. Usually the C chemical shifts of known

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Ni-NHC complexes appear in the range of 149-171 ppm depending on the ancillary ligands
[
15].
Scheme 1. Synthesis of complexes 2a-c.
Purple single crystals of complex 2a suitable for an X-ray diffraction study were grown
from a solution of CH Cl and ethyl acetate.[16] The molecular structure of complex 2a is
2
2
depicted in Figure 1. The central Ni(II) ion is coordinated by the amido nitrogen, two carbene
atoms and one chloride ion, forming two six-membered chelate rings. The geometry about Ni
is approximately square planar, with the C28-Ni1-C11 angle of 172.8(2)° being a consequence
of the chelate constraint. N3, Ni1, and Cl lie on a crystallographic axis of symmetry. The two
aromatic rings in 2a are distinctly nonparallel, with an angle of ca. 67.04°. The twist in the
chelate backbone presumably arises from repulsion between the two ortho hydrogens on the
1
aromatic rings. H NMR spectra showed that the benzylic CH protons are diastereotopic in
2
solution, indicating that the two ortho hydrogens prevent ligand twisting in solution at room
temperature. In addition, the NHC rings are not coplanar with the aryl backbone (two
aromatic rings) and are all tilted by 25°. The nickel-carbene distances (Ni1−C11 = 1.899(5) Å
and (Ni1−C28 = 1.902(5) Å) are very similar to the Ni−Ccarbene bond distances found for
pincer complexes with two trans-positioned imidazolin-2-ylidene donor groups [8a,10a]. The

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Ni1−N3 bond distance is 1.891(4) Å which is similar to the distance observed in NNN and
PNP pincer-type nickel (II) complexes based on a diarylamido backbone [11a,12a].
Figure1. Molecular structure of complex 2a, showing 30% probability displacement ellipsoids. Selected
interatomic distances (Å) and angles (deg): Ni1−N3 = 1.891(4), Ni1−C11 = 1.899(5), Ni1−C28 = 1.902(5),
Ni1−Cl = 2.2178(14), N3−Ni1−Cl = 179.43(13), C11−Ni1−C28 = 172.8(2).
2.2. Catalytic Suzuki coupling reactions
To evaluate the catalytic activity of complexes 2a-c in the Suzuki coupling reactions, the
reaction of 4-bromoanisole with phenylboronic acid was initially chosen to optimize the
reaction conditions. The results listed in Table 1 showed that the use of Ni(DME)Cl alone
2
gave essentially no coupling product (entry 1). The combination of Ni(DME)Cl and
2
pincer-type imidazolium salt 1a did not exhibit any catalytic activity (entry 2). Fortunately,
4-bromoanisole was successfully reacted with phenylboronic acid in dioxane in the presence
of 2 mol% complex 2a together with potassium phosphate at reflux to afford the desired
product in 95% yield (entry 3). When the amount of catalyst loading was reduced to 1 mol%,
the yield was not significantly changed (entry 4). However, further decrease of the catalyst

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loading to 0.5 mol% led to 78% coupling product yield (entry 5). These data illustrated that 1
mol% of catalyst 2a is sufficient for the coupling of 4-bromoanisole with phenylboronic acid.
At this catalyst loading, complexes 2b and 2c catalyzed the couplings to afford the
biphenyls in 77% and 63%, respectively (entries 6 and 7). We next examined the effect of the
solvent, and found that the choice of solvent was very critical, as the reaction in dioxane was
much more efficient than those in toluene, DMSO and THF (entries 8-10). Subsequently, the
reaction was investigated in the presence of different bases. The results showed that among
the bases explored, K PO is the most effective, and others such as Na CO , K CO , Cs CO
3
3
4
2
3
2
3
2
t
and KO Bu led to lower yields (entries 11-14). Thus, the optimized reaction conditions for the
present corss-coupling of 4-bromoanisole with phenylboronic acid involve the use of 1.0
mol% of 2a as the catalyst, K PO as the base, dioxane as the solvent and at reflux.
3
4
Table 1.
Optimization of reaction conditions in Suzuki coupling reactions catalyzed by complexes 2a-c
a
b
Entry
Catalyst (mol%)
Solvent
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
toluene
DMSO
THF
Base
Yield (%)
1
2
3
4
5
6
7
8
9
Ni(DME)Cl (2)
K PO4
3
0
2
1a (2) + Ni(DME)Cl (2)
K PO4
3
trace
95
95
78
77
63
64
trace
0
2
2a (2)
2a (1)
2a (0.5)
2b (1)
2c (1)
2a (1)
2a (1)
2a (1)
K PO4
3
K PO4
3
K PO4
3
K PO4
3
K PO4
3
K PO4
3
K PO4
3
1
0
K PO4
3

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1
1
2a (1)
2a (1)
2a (1)
2a (1)
dioxane
dioxane
dioxane
dioxane
Na CO3
59
49
0
2
1
1
1
2
3
4
K CO3
2
Cs CO3
2
t
KO Bu
44
a
Reaction conditions: 0.5 mmol of 4-bromoanisole, 0.75 mmol of phenylboronic acid, 2.0 mmol of base,
4
.0 mL of solvent, reflux, under N2.
b
Isolated by silica gel column chromatography and based on 4-bromoanisole.
Having defined the optimized reaction conditions, we then attempted the cross-coupling
reactions of various aryl bromides with arylboronic acids under the optimal reaction
conditions. As shown in Table 2, most of the substrates with a variety of substituents afforded
the products in good to excellent yields. Bromobenzenes bearing electron-donating groups
such as methoxy (entries 1-3 and 13), methyl (entries 6 and 14) and amino (entry 15) reacted
with arylboronic acids smoothly giving the corresponding cross-coupling products in 86-95%
yields. Ortho methoxy-substituted aryl bromides (entry 3) gave lower yields as compared to
para- and meta-substituted analogues (entries 1 and 2, respectively), probably due to the
steric hindrance. Aryl bromides with electron-withdrawing cyano (entries 4 and 5), fluoro
(entry 16) and acetyl (entry 17) could be transformed to biaryl products in 85-91% yields.
Coupling reactions of phenylboronic acid (entries 1-6) and arylboronic acids containing
electron-donating groups (entries 7, 8 and 13-19) with aryl bromides gave products in high
yields. Arylboronic acids with electron-withdrawing para- and meta-cynao group gave
products in slightly lower yields of 78% and 80%, respectively (entries 9 and 10). The
reactions involving 1-naphthylboronic acid and its analogue, 2-naphthylboronic acid,
performed well to give products in 92% and 89% yields, respectively (entries 11 and 12).

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Finally, we also investigated the Suzuki reactions between heteroaryl bromides and boronic
acids using 2a as the catalyst. Bromopyridine and 2,6-dibromopyridine were used as the
heteroaromatic component in these reactions, and the high yields of 86-94% (entries 18-21)
indicated that complex 2a also exhibited excellent catalytic activity for the coupling of
heteroaryl-halides with different arylboronic acids.
Table 2.
a
Catalytic Suzuki coupling reactions of aryl bromides with arylboronic acids
K PO
4
2
a,
3
1
2
1
2
Ar -X + Ar -B(OH)
Ar -Ar
a-q
2
dioxane, refulx, 8-24 h
3
b
Entry
1
Arylbromide
Arylboronic acid
Product
Yield(%)
3a
95
H CO
3
2
3b
91
Br
3
4
5
3c
3d
3e
86
91
88
c
6
3f
89 (5)
95
7
8
3a
3b
3d
3e
85
78
80
d
9
d
1
0

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1
1
3g
3h
92
89
1
2
13
14
15
16
17
3i
3j
87
95
92
85
87
3k
3l
3m
1
1
2
8
9
0
3n
3o
91
89
3p
3q
94
86
e
2
1
a
Reaction conditions: 0.5 mmol of aryl bromide, 0.75 mmol of arylboronic acid, 1.0 mol% of 2a, 2.0 mmol
of K PO , 4.0 mL of dioxane, reflux, under N .
3
4
2
b
c
Isolated by silica gel column chromatography and based on aryl bromides.
Self-coupling byproduct of phenylboronic acid in parentheses was detected by GC-MS. In this case the
self-coupling byproduct could not be separated from the cross-coupling product by silica gel column
chromatography.
d
2
.0 mol% of 2a.
e
1
.5 mmol of phenylboronic acid, 2.0 mol% of catalyst; 4.0 mmol of K PO . The product is
3 4
2
,6-diphenylpyridine.

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3. Conclusion
In summary, we have successfully prepared a new type of nickel(II) complexes containing
CNC pincer-type bis-NHC ligands with an anionic diarylamindo backbone. Complexes 2a-c
are stable toward moisture and air and tolerate high temperatures. The structure of complex 2a
has been revealed by X-ray structural analysis. The complexes have been shown to be
effective in the Suzuki cross-coupling reactions of a variety of aryl bromides, even with less
active aryl bromides and heteroaryl halides. The potential of these nickel complexes in other
organic transformation is under investigation.
4. Experimental Section
4.1. General
Unless otherwise noted, all manipulations were performed under an argon atmosphere
using standard Schlenk techniques. All solvents were dried according to standard procedures.
Ni(DME)Cl was prepared according to known procedures [17]. All other reagents are
2
1
commercially available and were used without further purification. H (400 MHz, 600 MHz)
1
3
1
and C NMR (100 MHz, 125 MHz) spectra were recorded using Bruker instruments. H and
1
3
C chemical shifts are reported in ppm and calibrated to TMS on the basis of the solvent as
an internal standard (2.49 ppm, DMSO-d ; 7.27 ppm, CDCl ). All NMR spectra were
6
3
acquired at room temperature. Melting points were determined with an XRC-1 melting point
apparatus and were uncorrected. Mass spectra were obtained by using Bruker Autoflex III
instrument. Elemental analyses were performed on a CARLO ERBA-1106 instrument.

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4.2. X-ray crystal structure determination and refinement
X-ray single-crystal diffraction data for complex 2a were collected on an Enraf−Nonius
CAD-4 diffractometer at 294(2) K with Mο Kα radiation (λ = 0.71073 Å) by ω/2θ scan mode.
The structures were solved with direct methods using SHELXS-97 and refined by full-matrix
2
least-squares refinement on F with SHELXL-97 [18]. All atoms except hydrogen atoms were
refined with anisotropic displacement parameters. In general, hydrogen atoms were fixed at
calculated positions, and their positions were refined by a riding model.
Crystal/refinement data for 2a⋅CH Cl : formula C H Cl N Ni, M = 771.87, size 0.42 ×
2
2
41 44
3
5
0
1
.38 × 0.30 mm, monoclinic, space group P21/c, a = 14.187(9)Å, b = 28.721(15) Å, c =
o
o
o
3
0.1289(6) Å, α = 90 , β = 102.06 (6) , γ = 90 , F(000) = 1616, V = 4036.1(4) Å , T = 294(2)
3
-1
K, Z = 4, D(calcd) = 1.270 Mg/m , µ = 0.714 mm , range of h, k, l = -17/11, -35/35, -12/12,
2
reflns collected 16072, unique reflns 8193, refinement method full-matrix least-squares on F ,
parameters 411, R1 = 0.0891 (observed data with I > 2σ(I)), wR2 = 0.2076, GOF = 1.210.
4
.3. General procedure for the synthesis of [bis(2-(3-alkylimidazolin-2-yliden-1-yl)-
-methylphenyl)amido]chloronickel(II) (2a-c)
4
A mixture of one of the bis(imidazolium) salts 1a-c (0.100 mmol) and silver(I) oxide (27.6
mg, 0.120 mmol) in 5 mL of solvent (CH Cl /MeCN, v/v = 1:1) was stirred at room
2
2
temperature for 24 h. The reaction mixture was filtered and washed with CH Cl (5 mL × 2).
2
2
The combined filtrate was reduced to 5 mL under vacuum. Ni(DME)Cl (22.0 mg, 0.100
2
mmol) in CH Cl (3 mL) was added to the resulting solution and stirred at room temperature
2
2
for 2 h. The reaction mixture was filtered and washed with CH Cl (5 mL × 2). The combined
2
2
solution was evaporated under reduced pressure to leave a raw product which was purified by

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flash chromatography on silica gel (dichloromethane) to give a purple solid.
4.3.1.[Bis{2-(3-(2,4,6-trimethylbenzyl)imidazolin-2-yliden-1-yl)-4-methylphenyl}amido]chlor
onickel(II) (2a)
1
Yield: 38.0 %. H NMR (600 MHz, DMSO-d ): δ 7.80 (d, J = 2 Hz, 2H, imi-H), 7.51 (s,
6
2H, Ar-H), 6.83 (s, 4H, Ar-H), 6.77 (d, J = 1.6 Hz, 2H, imi-H), 6.72 (d, J = 8.4 Hz, 2H, Ar-H),
6
.70 (d, J = 8.4 Hz, 2H, Ar-H), 5.95 (d, J = 15.2 Hz, 2H, NCH ), 5.52 (d, J = 15.2 Hz, 2H,
2
13
NCH ), 2.30 (s, 18H, ArCH ), 2.19 (s, 6H, ArCH ). C NMR (150 MHz, DMSO-d ): δ 161.9
2
3
3
6
(
Ccarbene), 140.4, 137.9, 137.6, 132.2, 130.7, 129.6, 127.6, 126.5, 123.7, 122.7, 120.3, 118.4
Ar-C, imi-C), 48.4 (NCH ), 21.0 (CH ), 20.8 (CH ), 20.2 (CH ). Mp: > 280 °C. Anal. Calcd
(
2
3
3
3
for C H N NiCl: C, 69.94; H, 6.16; N, 10.19. Found: C, 69.87; H, 6.10; N, 10.22. MS
4
0
42
5
+
(
MALDI-TOF, m/z) calcd for C H N NiCl: 685.25, found 650.28 [M − Cl] .
40 42 5
4.3.2. [Bis(2-(3-benzylimidazolin-2-yliden-1-yl)-4-methylphenyl)amido]chloronickel(II) (2b)
1
Yield: 35.0 %. H NMR (400 MHz, DMSO-d ): δ 7.86 (s, 2H, imi-H), 7.48−7.55(m, 6H,
6
Ar-H, imi-H), 7.34 (s, 2H, Ar-H), 7.17−7.21 (m, 2H, Ar-H), 7.10−7.12 (m, 4H, Ar-H), 6.75 (d,
J = 8.4 Hz, 2H, Ar-H), 6.50 (d, J = 8.4 Hz, 2H, Ar-H), 6.02 (d, J = 14.8 Hz, 2H, NCH ), 5.34
2
1
3
(
d, J = 15.2 Hz, 2H, NCH ), 2.32 (s, 6H, ArCH ). CNMR (100 MHz, DMSO-d ): δ 161.5
2 3 6
(Ccarbene), 140.4, 138.6, 132.4, 128.7, 127.8, 127.7, 126.7, 124.9, 123.6, 120.5, 118.5 (Ar-C,
imi-C), 52.1 (NCH ), 20.8 (ArCH ). Mp：272−274 °C. Anal. Calcd for C H N NiCl: C,
2
3
34 30
5
67.75; H, 5.02; N, 11.62. Found: C, 67.68; H, 5.05; N, 11.66. MS (MALDI-TOF, m/z) calcd
+
for C H N NiCl: 601.15, found 566.19 [M − Cl] .
3
4
30
5
4.3.3. [Bis(2-(3-butylimidazolin-2-yliden-1-yl)-4-methylphenyl)amido]chloronickel(II) (2c)

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1
Yield: 36.5 %. H NMR (400 MHz, DMSO-d ): δ 7.85 (d, J = 1.2 Hz, 2H, imi-H), 7.47 (s,
6
2H, imi-H), 6.66 (d, J = 8Hz, 2H, Ar-H), 6.45 (d, J = 8Hz, 2H, Ar-H), 4.52−4.59 (m, 2H,
NCH ), 4.06−4.15 (m, 2H, NCH ), 2.27 (s, 6H, ArCH ), 1.86−1.91 (m, 2H,
2
2
3
NCH CH CH CH ), 1.73−1.78 (m, 2H, NCH CH CH CH ), 1.17−1.22 (m, 4H,
2
2
2
3
2
2
2
3
1
3
NCH CH CH CH ), 0.82 (d, J = 7.2 Hz, 6 H, NCH CH CH CH ). CNMR (100 MHz,
2
2
2
3
2
2
2
3
DMSO-d ): δ 160.9 (Ccarbene), 140.4, 132.3, 127.4, 126.3, 124.6, 123.6, 120.3, 117.8 (Ar-C,
6
imi-C), 48.9 (NCH CH CH CH ), 33.3 (NCH CH CH CH ), 20.8 (ArCH ), 19.5
2
2
2
3
2
2
2
3
3
(
NCH CH CH CH ), 13.8 (NCH CH CH CH ). Mp: 144−146 °C. Anal. Calcd for
2 2 2 3 2 2 2 3
C H N NiCl: C, 62.89; H, 6.41; N, 13.10. Found: C, 62.78; H, 6.52; N, 13.09. MS
28
34
5
+
(
MALDI-TOF, m/z) calcd for C H N NiCl: 533.19, found 498.21 [M − Cl] .
28 34 5
4
.4. General procedure for the bis-NHC-Ni(II) complex-catalyzed Suzuki coupling reactions
In a typical reaction, to a 25-mL Schlenk tube equipped with a magnetic stirring bar were
added nickel(II) catalyst 2a (0.005 mmol, 1.0 mol %), aryl halides (0.5 mmol), phenylboronic
acids (0.75 mmol), and anhydrous K PO (2.0 mmol). The tube was then evacuated (3 × 5
3
4
min) under vacuum and backfilled with N . Dried dioxane (4.0 mL) was injected via a syringe,
2
and the reaction mixture was stirred at reflux until the aryl halides had disappeared as
monitored by TLC. The reaction mixture was treated with H O (20 mL), then extracted with
2
Et O (3 × 15 mL). The combined organic extracts were washed with sat. aq NaCl (10 mL) and
2
dried with anhydrous MgSO . The solvent was removed under reduced pressure and the crude
4
material was purified by silica gel column chromatography to give the corresponding biaryl.
All the coupling products are known and their structures were identified by comparing their
1
13
H NMR and C NMR spectral data with those reported in literature.

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Acknowledgments
We gratefully acknowledge the National Natural Science Foundation of China (21321061,
1072134 and J1103315/J0104) for financial support, and the Comprehensive Training
2
Platform of Specialized Laboratory, College of Chemistry, Sichuan University for NMR and
MS measurements.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
References
[
1] (a) N. Miyaura, K. Yamada, A. Suzuki, Tetrahedron Lett. 20 (1979) 3437;
(
(
(
(
(
(
(
(
b) N. Miyaura, A. Suzuki, Chem. Rev. 95 (1995) 2457;
c) A. Suzuki, J. Organomet. Chem. 576 (1999) 147;
d) N. Miyaura, J. Organomet. Chem. 653 (2002) 54;
e) A.F. Littke, G.C. Fu, Angew. Chem. Int. Ed. 41 (2002) 4176;
f) A. Suzuki, Chem. Commun. (2005) 4759;
g) F. Alonso, I.P. Beletskaya, M. Yus, Tetrahedron 64 (2008) 3047;
h) G.A. Molander, B. Canturk, Angew. Chem. Int. Ed. 48 (2009), 9240;
i) A. Suzuki, Angew. Chem. Int. Ed. 50 (2011) 6722.
[
2] For examples, see: (a) U. Mitschke, P. Bauerle, J. Mater. Chem. 10 (2000) 1471;
(
(
(
(
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Highlights
►
A new type of nickel(II) complexes containing CNC pincer-type bis-NHC ligands
was synthesized.
►
►
One of the complexes was characterized by X-ray diffraction.
The complexes showed high efficiency in catalyzing Suzuki cross-coupling
reactions.

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Supporting Information for
Synthesis and catalytic activity of nickel(II) complexes of
CNC pincer-type N-heterocyclic carbene ligands
Shuchao Wang, Fang Ren, Yuping Qiu, Meiming Luo*
Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of
Chemistry, Sichuan University, Chengdu 610064, P. R. China
Contents
I. Analytical data for cross-coupling products…........................S2–S6
II. Copies of NMR spectra for 2a−c…………………………....S7–S12
S1

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I. Analytical data for cross-coupling products
[1]
4
-Methoxybiphenyl (3a) (Table 2, entry 1)
o
1
White solid, MP: 89-90 C. H NMR (400 MHz, CDCl ): δ 7.56-7.51 (m, 4H), 7.42 (t, J
3
1
3
=
7.5 Hz, 2H), 7.30 (t, J = 7.4 Hz, 1H), 7.15-6.96 (m, 2H), 3.85 (s, 3H). C NMR (100
MHz, CDCl ): δ 159.1, 140.8, 133.8, 128.7, 128.2, 126.8, 126.7, 114.2, 55.4.
3
[2]
3
-Methoxybiphenyl (3b) (Table 2, entry 2)
1
Colorless liquid, H NMR (400 MHz, CDCl ): δ 7.60-7.57 (m, 2H), 7.45-7.41 (m, 2H),
3
7
.37-7.32(m, 2H), 7.20-7.17(m, 1H), 7.13-7.12 (m, 1H), 6.91-6.88 (m, 1H), 3.86 (s, 3H).
1
3
C NMR (100 MHz, CDCl ): δ 159.9, 142.8, 141.1, 129.7, 128.7, 127.4, 127.2, 119.7,
3
112.9, 112.7, 55.3.
[2]
2
-Methoxybiphenyl (3c) (Table 2, entry 3)
1
Colorless liquid, H NMR (400 MHz, CDCl ): δ 7.53-7.51 (m, 2H), 7.41 (t, J = 7.3 Hz,
3
1
3
2
H), 7.33-7.30 (m, 3H), 7.06-6.96 (m, 2H), 3.81 (s, 3H). C NMR (100 MHz, CDCl )ꢀδ
3
1
56.4, 138.5, 130.9, 130.7, 129.5, 128.6, 128.0, 126.9, 120.8, 111.2, 55.5.
[
3]
biphenyl-4-carbonitrile (3d) (Table 2, entry 4)
o
1
White solid, Mp: 84-86 C. H NMR (400 MHz, CDCl ): δ 7.74-7.67 (m, 4H), 7.61-7.58
3
1
3
(
m, 2H), 7.51-7.47(m, 2H), 7.45-7.41 (m, 1H). C NMR (100 MHz, CDCl ): δ 145.6,
3
1
39.1, 132.6, 129.1 128.6, 127.7, 127.2, 118.9, 110.9.
[
3]
Biphenyl-3-carbonitrile (3e) (Table 2, entry 5)
S2

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o
1
White solid, Mp: 36-37 C. H NMR (400 MHz, CDCl ):δ7.89 (s, 1H), 7.85-7.83 (m,
3
1
H), 7.66 (d, J = 7.8 Hz, 1H), 7.60-7.57(m, 3H), 7.53-7.49 (m, 2H), 7.46-7.42 (m, 1H).
1
3
C NMR (100 MHz, CDCl ): δ 142.4, 138.8, 131.6, 130.6, 129.6, 129.1, 128.4, 127.0,
3
118.8, 112.9.
[4]
1
-Phenylnaphthalene (3g) (Table 2, entry 11)
1
Colorless oil, H NMR (400 MHz, CDCl ): δ 7.91 (d, J = 8.5 Hz, 2H), 7.86 (d, J = 8.3 Hz,
3
13
1
H), 7.52-7.46 (m, 6H), 7.45-7.41 (m, 3H). C NMR (100 MHz, CDCl ): δ 140.7, 140.2,
3
1
33.8, 131.6, 130.1, 128.2, 127.6, 127.2, 126.9, 126.0, 125.8, 125.4.
[2]
2
-Phenylnaphthalene (3h) (Table 2, entry 12)
o
1
White solid, Mp:101-102 C. H NMR (400 MHz, CDCl ): δ 8.04 (s, 1H), 7.92-7.85 (m,
3
1
3
3
H), 7.76-7.71 (m, 3H), 7.52-7.47 (m, 4H), 7.39-7.35 (m, 1H). C NMR (100 MHz,
CDCl ): δ 141.1, 138.5, 133.7, 132.6, 128.9, 128.4, 128.2, 127.6, 127.4, 127.3, 126.3,
3
125.9, 125.8, 125.6.
[5]
4
-(tert-Butyl)-4’-methoxy-1,1’-biphenyl (3i) (Table 2, entry 13)
o
1
White solid, Mp: 125-126 C. H NMR (400 MHz, CDCl ): δ 7.54-7.43 (m, 6H), 6.97 (d,
3
1
3
J = 8.8 Hz, 2H), 3.85 (s, 3H), 1.36 (s, 9H). C NMR (100 MHz, CDCl ): δ 158.9, 149.6,
3
1
37.9, 133.6, 128.0, 126.3, 125.6, 114.1, 55.3, 34.4, 31.4.
S3

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[
6]
4
-Methoxy-4'-methylbiphenyl (3j) (Table 2, entry 14)
o
1
White solid, MP: 107-108 C. H NMR (400 MHz, CDCl ): δ 7.47-7.40 (m, 2H), 7.38 (d,
3
J = 8.1 Hz, 2H), 7.15 (d, J = 8.0 Hz, 2H), 6.91-6.87 (m, 2H), 3.77 (s, 3H), 2.31 (s, 3H).
1
3
C NMR (100 MHz, CDCl ): δ 158.9, 137.9, 136.3, 133.7, 129.4, 127.9, 126.6, 114.1,
3
55.3, 21.0.
[
7]
4
-Methoxy-4'-[(1,1'-biphenyl)-amine] (3k) (Table 2ꢁentry 15)
o
1
White solid, Mp: 144-145 C. H NMR (400 MHz, CDCl ): δ 7.49 (d, J = 8.1 Hz, 2H),
3
7
3
.40 (d, J = 7.6 Hz, 2H), 6.98 (d, J = 8.1 Hz, 2H), 6.77 (d, J = 7.5Hz, 2H), 3.87 (s, 3H),
1
3
.71 (brs, 2H). C NMR (100 MHz, CDCl ): δ 158.4, 145.5, 133.8, 131.4, 127.6, 127.4,
3
115.4, 114.1, 55.3.
[8]
4
-methoxyl-4'-fluorobiphenyl (3l) (Table 2ꢁentry 16)
o
1
White solid, Mp: 93-95 C. H NMR (400 MHz, CDCl ): δ 7.51-7.45 (m, 4H), 7.10 (t, J =
3
1
3
8
.8, 2H), 6.97 (d, J = 8.8, 2H), 3.85 (s, 3H). C NMR (100 MHz, CDCl ) δ 162.1(d, J =
3
244 Hz), 159.13, 136.98 (d, J = 3.4 Hz), 132.85, 128.22 (d, J = 7.9 Hz), 128.04, 115.53 (d,
J = 21.2 Hz), 114.26, 55.36.
[9]
4
(4'-Methoxyphenyl)acetophenone (3m) (Table 2ꢁentry 17)
o
1
White solid, Mp: 152-153 C. H NMR (400 MHz, CDCl ): δ 8.01 (d, J = 8.6 Hz, 2H),
3
7
2
1
.66 (d, J = 8.6 Hz, 2H), 7.58 (d, J = 8.8 Hz, 2H), 7.00 (d, J = 8.8 Hz, 2H), 3.87 (s, 3H),
1
3
.63 (s, 3H). C NMR (100 MHz, CDCl ): δ 197.7, 159.9, 145.3, 135.2, 132.2, 128.9,
3
28.3, 126.6, 114.4, 55.3, 26.6.
S4

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[10]
3
-(4-Methoxyphenyl)pyridine (3n) (Table 2, entry 18)
o
1
White solid, Mp: 60-61 C. H NMR (400 MHz, CDCl ): δ 8.82 (s, 1H), 8.55 (s, 1H),
3
7
.84 (s, 1H), 7.52 (d, J = 8.7 Hz, 2H), 7.34 (s, 1H), 7.02 (d, J = 8.6 Hz, 2H), 3.86 (s, 3H).
1
3
C NMR (100 MHz, CDCl ): δ 159.7, 148.0, 147.8, 136.6, 133.8, 130.2, 128.2, 123.6,
3
114.5, 55.3.
[
10]
3
-(p-Tolyl)pyridine (3o) (Table 2, entry 19)
1
Yellow oil, H NMR (400 MHz, CDCl ): δ 8.84 (d, J = 2.1 Hz, 1H), 8.57 (dd, J = 4.8, 1.4
3
Hz, 1H), 7.87-7.84 (m, 1H), 7.48 (d, J = 8.1 Hz, 2H), 7.35 (dd, J = 7.9, 4.8 Hz, 1H), 7.29
1
3
(
d, J = 8.0 Hz, 2H), 2.41 (s, 3H). C NMR (100 MHz, CDCl ): δ 148.1, 138.0, 136.5,
3
1
34.9, 134.1, 129.7, 126.9, 123.4, 21.1.
[11]
3
-(Naphthalen-2-yl)pyridine (3p) (Table 2, entry 20)
o
1
White solid, Mp: 99-100 C. H NMR (400 MHz, CDCl ): δ 9.01 (s, 1H), 8.66 (s, 1H),
3
8
1
1
.07 (s, 1H), 8.03-7.89 (m, 4H), 7.74 (dd, J = 8.5, 1.8 Hz, 1H), 7.56-7.52 (m, 2H), 7.44 (s,
1
3
H). C NMR (100 MHz, CDCl ): δ 148.5, 136.6, 135.1, 134.5, 133.6, 132.9, 128.9,
3
28.2, 127.7, 126.6, 126.4, 126.1, 125.0, 123.6.
[12]
2
,6-Diphenylprydine (3q) (Table 2, entry 21)
o
1
White solid, Mp: 78-79 C. H NMR(400MHz, CDCl ); δ 8.16 (d, J = 7.2, 4H), 7.82 (t, J
3
1
3
=
7.2, 1H) , 7.7 (d, J = 7.7, 2H) , 7.50(d, J = 7.7, 4H) , 7.46-7.40 (m, 2H). C NMR (100
MHz, CDCl ): δ156.9, 139.5, 137.6, 129.1, 128.8, 127.1, 118.5
3
S5

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References
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(
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2) Liu, W.; Cao, H.; Lei, A. Angew. Chem. Int. Ed. 2010, 49, 2004.
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S6

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II. Copies of NMR spectra for 2a−c.
S7

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S8

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S9