Highly active NHC-Pd(ii) complexes for cross coupling of aryl chlorides and arylboronic acids: An investigation of the effect of remote bulky groups

Article abstract of DOI:10.1039/c8nj01047a

A series of palladium(ii) complexes bearing remote bulky ligands were synthesized and characterized. Their catalytic activity for Suzuki-Miyaura cross-coupling reactions and the effect of remote bulky groups were investigated. These new palladium complexes are highly efficient for the Suzuki-Miyaura cross-coupling reactions of aryl chlorides and arylboronic acids with low catalyst loadings (0.05 mol%) at room temperature in air.

Full text of DOI:10.1039/c8nj01047a

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Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
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ARTICLE
Highly Active NHC-Pd (II) Complexes for Cross Coupling of Aryl
Chlorides and Arylboronic Acids: An Investigation of the Remote
Bulky Group Effect
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
b
a
a
b
DOI: 10.1039/x0xx00000x
Fangwai Han, Ying Xu, Rongjiao Zhu, Guiyan Liu,* Chen Chen,* and Jianhui Wang *
www.rsc.org/
A series of palladium (II) complexes bearing remote bulky ligands were synthesized and characterized. Their catalytic
activity for Suzuki-Miyaura cross-coupling reactions and the effect of the remote bulky groups were investigated. These
new palladium complexes are highly efficient for the Suzuki-Miyaura cross-coupling reactions of aryl chlorides and
arylboronic acids with low catalysts loadings (0.05 mol %) at room temperature in air.
1
have been reported by Organ et al., and Liu et al.
1
12,13
and
Introduction,
these catalysts have shown significant improvements in
catalytic activity. These sterically bulky ligands were usually
introduced at the ortho positions of the N-aryl moieties of the
NHCs or onto the backbone derived from the NHCs (Chart 1).
Palladium-catalyzed Suzuki-Miyaura cross-coupling (SMC)
reactions have been widely used as versatile tools in the
synthesis of biaryls in natural products, drugs, and other
1
materials. Traditionally aryl iodides or aryl bromides have
Chart 1 Bulky NHC-Pd/ligand Precatalysts
been used as the electrophilic coupling partner, but from an
economic standpoint, aryl chlorides are better cross-coupling
electrophiles for Suzuki-Miyaura reactions. However the SMC
reaction of aryl chlorides and arylboronic acids presents many
challenges such as the need for harsh reaction conditions and
Previous work:
N
N
steric bulk on the ortho-position
of the N-aryl moiety
2
Cl Pd Cl
N
high catalyst loadings. In order to solve these problems and
steric bulk onthe backbone
derived from NHCs
improve catalytic efficiency, many Pd precatalysts have been
3
designed.
R
R= H, or Cl
N-heterocyclic carbenes (NHCs) have excellent σ-donating
properties and can significantly improve the stability of
This work:
Ph
4
precatalysts. The use of NHCs as ligands in Pd/ligand catalytic
N
N
Ph
Ph
N
N
Ph
Ph
Ph
5
Cl Pd Cl
N
X
Pd X
Ph
systems has led to a variety of satisfactory developments.
6
Several different donor groups, such as N-donors, P-donors
Ph Ph
Ph Ph
Ph
N
7
N
8
steric bulk on the
para-position of the
N-aryl moiety
Ph
Ph
R
and others, have been used as auxiliary ligands in Pd/ligand
catalytic systems. Among them, N-donor groups, such as
pyridine and imidazole are excellent throw-away ligands which
are cheap and stable in air and they can increase the steric
4
steric bulk on the
para-position of the
N-aryl moiety
5:X = Cl, R = Cl
6:X = Cl, R = H
7:X = Br, R = Br
Ph
steric bulk on the auxiliary ligand
bulk and enhance the stabilization and initiation of palladium
9
In contrast, para-position modifications of the N-aryl
precatalysts. Increasing the steric bulk of NHC ligands has moieties of NHCs and auxiliary ligands containing remote bulky
1
0
been shown to promote the coupling reactions. Recently, ligands have received little attention. In our previous studies, a
pyridine enhanced precatalyst preparation stabilization and [Pd(1-tritylimidazole) Cl complex with 1-tritylimidazole
]
2
2
3
g
initiation (PEPPSI) palladium complexes bearing bulky NHCs ligands was reported. The introduction of triphenylmethyl as
a remote bulky group greatly improved the stability of the
palladium metal and this complex showed good catalytic
Tianjin Key Laboratory of Structure and Performance for Functional Molecules;
activity at room temperature for SMC reactions using aryl
Key Laboratory of Inorganic-Organic hybrid Functional Material Chemistry (Tianjin
a.
Normal University); Ministry of Education; College of Chemistry, Tianjin Normal
University, Tianjin, 300387, P. R. China. E-mail: guiyanliu2013@163.com
Department of Chemistry, College of Science, Tianjin University, Tianjin 300350, P.
R. China. E-mail: wjh@tju.edu.cn
chlorides as the electrophilic coupling partner. With this result
in mind, we sought to determine if catalytic efficiency could be
further enhanced by simultaneously introducing remote bulky
groups onto NHCs and auxiliary ligands. Herein, a series of new
palladium(II) complexes with bulky NHC ligands and auxiliary
b.
1
13
Electronic Supplementary Information (ESI) available: Copies of H and C
NMR spectra. summary of the most important crystallographic data. See
A
DOI: 10.1039/x0xx00000x
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ARTICLE
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ligands (pyridine or 1-tritylimidazole) are reported for the
Suzuki-Miyaura reaction of aryl chlorides with arylboronic
acids at room temperature in air.
Results and discussion,
The synthetic route for several palladium(II) complexes
containing a bulky N-heterocyclic carbene and an auxiliary
ligand is illustrated in Scheme 1. All the complexes were
obtained in good yields using commercially available 4-
tritylaniline
glyoxal in ethanol to give compound
with paraformaldehyde and trimethyl chlorosilane to give
compound in good yields. Complexes 4-7 were prepared by
heating the NHC precursor with PdCl and a pyridine
1
as the starting material. First
1 was reacted with
2
which was then refluxed
3
3
2
2 3
derivative (or 1-tritylimidazole) in the presence of K CO .
Figure 1. Perspective view of complex
4
. Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are set at the 50% probability level. Selected
interatomic distances (Å) and bond angles (deg): Pd1-C1 = 1.965(3), Pd1-N3 =
2.080(2), Pd1-Cl1 = 2.3012(7), Pd1-Cl2 = 2.3272(7), C1-N1 = 1.348(3), C1-N2 =
Scheme 1. Synthesis of Complexes 4-7.
Ph
1
.353(3), C1-Pd1-N3 = 175.17(9), Cl1-Pd1-Cl2 = 176.85(3), N3-Pd1-Cl1 = 90.64(7),
Ph
Ph
C1-Pd1-Cl1 = 85.55(8).
O
O
NH
2
N
N
Ph
EtOH,reflux Ph
Ph
Ph
Ph
Ph
2
1
N
N
Ph
Ph
(
HCHO)n
Cl
(
3 3
CH ) SiCl,reflux
Ph
Ph
3
Ph Ph
N
PdCl
2
,
1
-tritylimidazole
K
CO
reflux
, THF,
K CO , THF, PdCl
2
,
2
3
2
3
R
reflux
N
N
Ph
N
N
Ph
Ph
Ph Ph
Ph
Ph Ph
Cl Pd Cl
N
X
Pd X
Ph Ph
Ph Ph
N
N
Ph
Ph
R
4
5:X = Cl, R = Cl
6:X = Cl, R = H
Ph
Figure 2. Perspective view of complex 5. Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are set at the 50% probability level. Selected
7
:X = Br, R = Br
interatomic distances (Å) and bond angles (deg): Pd1-C1 = 1.959(10), Pd1-N3 =
Single crystals of complexes 4-7 that were suitable for X-ray 2.110(8), Pd1-Cl1 = 2.329(2), Pd1-Cl2 = 2.323(2), C1-N1 = 1.337(11), C1-N2 =
analyses were obtained by slow evaporation from petroleum C1-Pd1-Cl1 = 87.6(3).
1.347(11), C1-Pd1-N3 = 178.2(3), Cl1-Pd1-Cl2 = 175.72(9), N3-Pd1-Cl1 = 92.2(2),
ether and CH Cl2 solvent mixtures. The structures of
2
complexes 4-7 and some selected bond lengths and bond
angles are shown in Figs. 1-4, respectively. The Pd atoms in
complexes 4-7 all have four-coordinated square planar
geometries constituting of Pd1/C1/Cl1/N3/Cl2. The Pd1-C1
distance in complex 4 is 1.965(3) Å and this same distance in
complexes and 7 is 1.959(3), 1.957(3) and 1.951(11) Å,
5,
6
respectively. The Pd1-N3 distance in complex
and this same distance in complexes and
.095(2) and 2.108(9) Å, respectively, indicating that 1-
4
is 2.080(2) Å
5,
6
7 is 2.110(8),
2
tritylimidazole has a better coordination with metal palladium
comparing with other auxiliary ligands. The C1-Pd1-N3 bond
angles in
1
4
,
5
,
6
76.3(4) respectively. The steric bulk of 1-tritylimidazole
and
7 are 175.17(9), 178.2(3), 179.04(12) and
Figure 3. Perspective view of complex
clarity. Thermal ellipsoids are set at the 50% probability level. Selected
interatomic distances (Å) and bond angles (deg): Pd1-C1 = 1.957(3), Pd1-N3 =
.095(2), Pd1-Cl1 = 2.3066(9), Pd1-Cl2 = 2.3110(9), C1-N1 = 1.352(3), C1-N2 =
.353(4), C1-Pd1-N3 = 179.04(12), Cl1-Pd1-Cl2 = 176.38(3), N3-Pd1-Cl1 =
91.79(8), C1-Pd1-Cl1 = 88.07(9).
6. Hydrogen atoms have been omitted for
o
2
1
ligand made the C1-Pd1-N3 bond angles in
distortion.
4 have a larger
2
| J. Name., 2012, 00, 1-3
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The catalytic activities of complexes
examined (entries 14-16). Compared with complex
contains a bulky auxiliary ligand, , and all required longer
5,
6
, and
7
was also
4
which
5,
6
7
reaction times (7 to 27 h versus 4 h) to reach a 95% yield. For
comparison, a Pd-PEPPSI-IPr complex with a normal NHC
ligand and an auxiliary ligand was also tested and under the
same conditions as complex
4, the yield was only 85% (versus
9
5%) (entry 17). However, the yield can also reach 95% after 6
hours (entry 17).
It’s clear that catalyst
4 bearing remote bulky groups on the
para-positions of the N-aryl moieties of the NHC and at the
same time on the auxiliary ligand gives a significant
improvement in catalytic activity over the other catalysts.
These results show that the catalytic efficiency of a catalyst is
not only affected by bulky NHC and auxiliary ligands but also
by the distant of the bulky substituents from the metal. This
may be because the remote bulky auxiliary ligands can strongly
coordinate to the Pd(0) which effectively protects the Pd(0).
Figure 4. Perspective view of complex 7. Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are set at the 50% probability level. Selected
interatomic distances (Å) and bond angles (deg): Pd1-C1 = 1.951(11), Pd1-N3 =
2.108(9), Pd1-Br1 = 2.4069(15), Pd1-Br2 = 2.4046(16), C1-N1 = 1.346(13), C1-N2
= 1.383(13), C1-Pd1-N3 = 176.3(4), Br1-Pd1-Br2 = 171.27(6), N3-Pd1-Br1 =
94.2(3), C1-Pd1-Br1 = 87.3(3).
In order to optimize the reaction conditions, the catalytic
activity of complex
4 (0.05 mol% loading) for the Suzuki-
Miyaura reaction of chlorobenzene (0.25 mmol) and
phenylboronic acid (0.3 mmol) was tested in the presence of
different bases and solvents. The results are shown in Table 1.
The activities of complexes
4 and 5 for Suzuki-Miyaura
reactions of other aryl chlorides and arylboronic acids were
then investigated under the optimized conditions. The results
are summarized in Table 2. All the reactions proceeded
smoothly with a 0.05 mol % catalyst loading. For the aryl
chlorides, neither electron-donating nor electron-withdrawing
groups all gave excellent yields (entries 1-8). For the
arylboronic acids, various functional groups including –F, -Cl,
When single-solvent systems (MeOH, EtOH, i-PrOH, and H
were used, moderate yields were obtained (70%, 75%, 80%,
0%, respectively) (entries 1-4). Mixed solvents of H O with an
alcohol gave higher yields, 85-95% (entries 5-7). The 95% yield
was obtained using i-PrOH/H O (1:1) as the solvent (entry 7).
2
O)
8
2
2
The effect of different bases was also investigated and K
3 4
PO
−
Me, and −OMe were all tolerated (entries 9-14). It is worth
gave the best results (entries 7-13).
noting that the reaction of chlorobenzene with 2-formylfuran-
Table 1. Optimization of the Suzuki-Miyaura Coupling Reaction of Chlorobenzene and 5-boronic acid gave high yields of 95 and 97% (entry 15).
a
Phenylboronic using Complex 4
However, when 3-furanboronic acid was used as the substrate,
Cl
B(OH)2
complex
50%) was obtained for complex
Encouraged by the above results, the scope of substrates
4
gave a good yield (80%), but only a moderate yield
(
5
(entry 16).
cat 4 (0.05 mol%), 3.5h
base, solvent, rt
+
was then extended to include sterically hindered 2-
methylphenyl and 2,5-dimethylphenyl chloride with ortho-
substituted arylboronic acids. The results with a 0.1 mmol %
catalyst loading are shown in Table 3. All the reactions
proceeded with good yields (80-96%) in the presence of
yield (%)b
entry
base
solvent
MeOH
EtOH
1
2
3
4
5
K
3
PO
4
70
75
80
80
85
K3PO4
K3PO4
i-PrOH
H O
2
K
3
PO
PO
4
4
complex
4 (entries 1-5). In addition, the even more sterically
K
3
MeOH/ H
O (1:1)
2
hindered 2,6-dimethylphenyl chloride also gave excellent
yields under the optimal conditions (entries 6-9).
6
7
K3PO
EtOH/ H O (1:1)
2
90
95
4
4
K
PO
i-PrOH/ H
O (1:1)
3
2
8
9
K2CO3
Na CO
i-PrOH/ H
i-PrOH/ H
i-PrOH/ H
i-PrOH/ H
2
O (1:1)
O (1:1)
O (1:1)
O (1:1)
80
65
Conclusions
2
3
2
1
0
1
NaHCO
Cs CO
3
2
2
2
2
55
90
In summary, a series of novel palladium(II) complexes
containing bulky N-heterocyclic carbenes and pyridine or 1-
tritylimidazole have been developed. Complexes 4 with a
remote bulky group on the para-positions of the N-aryl
moieties of the NHC and on the auxiliary ligand demonstrates
excellent catalytic activity for Suzuki-Miyaura cross-couplings
of aryl chlorides and arylboronic acids at room temperature.
The remote bulky ligands have been proven to be essential for
promoting this transformation.
1
2
3
1
1
1
1
2
KOH
KHCO3
i-PrOH/ H
i-PrOH/ H
O (1:1)
O (1:1)
70
30
3
4c
5d
95
95
95
85(95)
K PO
i-PrOH/ H O (1:1)
2
i-PrOH/ H O (1:1)
i-PrOH/ H
i-PrOH/ H
2
3
4
K
K
K
PO
3
4
e
16
3
3
PO
PO
4
2
O (1:1)
O (1:1)
f
g
17
4
2
a
Reactions were carried out using chlorobenzene (0.25 mmol, 1 equiv),
phenylboronic acid (0.3 mmol, 1.2 equiv), catalyst (0.000125 mmol), base (0.5
b
c
mmol, 2 equiv) in solvent (0.8 mL) at room temperature. Isolated yields.
d
e
f
g
catalyst 5, 7 h. catalyst 6, 12 h. catalyst 7, 27 h. catalyst Pd-PEPPSI-IPr, 3.5 h.
catalyst Pd-PEPPSI-IPr, 5 h.
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a
Table 2. Catalytic Activities of Complexes 4 and 5 for the Suzuki-Miyaura Coupling Reactions of Aryl Chlorides and Arylboronic Acids
cat (0.05 mol%)
Cl + (HO)
cat
2
B
K
3
PO
4 2
, H O/i-PrOH, rt
R
1
R
2
R2
time (h) yield (%)b
R
1
time (h) yield (%)b entry
product
cat
entry
1
product
4
5
3.5
7
95
95
4
5
1
3
97
99
9
F
F
4
5
1
3
95
98
2
3
4
5
3
7
95
95
10
11
Cl
4
5
4
10
95
95
4
5
4
8
98
95
F
4
5
4.5
10.5
98
95
4
5
17
37.5
97
97
4
12
4
5
17
37.5
95
95
5
6
7
4
5
6.5
14
95
95
13
14
OCH3
F
18
38
97
95
4
5
13.5
29
99
95
4
5
4
5
1
4
8
2.5
95
95
4
5
24
45
97
95
15
16
O
CHO
4
5
31
53
80
50
8
4
5
18.5
44
95
95
O
a
Reactions were carried out using aryl chloride (0.25 mmol, 1 equiv), arylboronic acid (0.3 mmol, 1.2 equiv), K
3
PO
4
(0.5 mmol, 2 equiv) in H
2
O/i-PrOH (0.8 mL) at room
b
temperature. Isolated yields.
a
Table 3. Catalytic Activities of Complex 4 for the Suzuki-Miyaura Coupling Reactions of Sterically Hindered Aryl Chlorides with o-methylsubstituted Arylboronic Acids
cat 4 (0.1mol%)
Cl + (HO)2B
K
3
PO
4
, H
2
O/i-PrOH, rt
R
1
R
2
R2
R
1
time (h) yield (%)b
product
time (h) yield (%)b
entry
6
product
entry
1
2
24
96
95
60
60
95
90
2
4
8
7
3
4
5
4
90
80
80
8
9
60
60
85
80
48
54
a
3 4 2
Reactions were carried out using aryl chloride (0.25 mmol, 1 equiv), arylboronic acid (0.3 mmol, 1.2 equiv), K PO (0.5 mmol, 2 equiv) in H O/i-PrOH (0.8 mL) at room
b
temperature. Isolated yields.
4
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1
3
4
H), 7.32 (s, 2H), 7.30-7.19 (m, 31H). C-NMR (100 MHz, CDCl
δ: 150.1, 149.1, 147.8, 146.3, 137.8, 137.0, 132.4, 132.0, 132.0,
31.1, 127.6, 126.1, 124.9, 124.7, 123.3, 64.9 ppm. Anal. Calcd
for C58H45Cl3N3Pd: C, 69.89; H, 4.55; N, 4.22. Found: C,
3
)
Experimental
1
Preparation of compound 2: A 100-mL flask was charged
6
9.92; H, 4.53; N, 4.26.
with compound
1 (2.8 g, 8 mmol) and ethanol (50 mL). After
Complex 6: Yellow solid. Yield: 60% (578 mg, 0.63 mmol).
the mixture was refluxed for a few minutes, 40% aqueous
glyoxal (0.4 mL) was added dropwise. The mixture was then
reacted for 4 h. After cooling to room temperature, the
resulting canary yellow precipitate was collected by filtration,
1
H-NMR (400 MHz, CDCl
3
) δ (ppm): 8.57-8.55 (m, 2H), 8.03 (d, J
=
7
1
1
8.8, 4H), 7.73-7.68 (m, 1H), 7.44 (d, J = 8.4, 4H), 7.32 (s, 2H),
1
3
3
.30-7.19 (m, 31H). C-NMR (100 MHz, CDCl ) δ: 168.1, 149.7,
49.4, 146.0, 144.6, 136.0, 135.5, 135.4, 130.3, 129.4, 125.9,
24.4, 123.2, 122.6, 121.5, 63.1 ppm. Anal. Calcd for
washed by methanol and dried under vacuum. Yield: 80% (4.4
1
g, 6.4 mmol). H-NMR (400 MHz, CDCl
3
) δ (ppm): 8.43 (s, 2H),
: 147.1, 146.6,
30.9, 130.3, 128.6, 128.3, 123.7, 118.4 ppm. Anal. Calcd for
1
3
C58H46Cl2N3Pd: C,72.39; H, 4.82; N, 4.37. Found: C,72.43; H,
3
7.28-7.20 (m, 38H). C-NMR (100 MHz, CDCl ) δ
4
.80; N, 4.38.
1
Complex 7: Orange-yellow solid. Yield: 50% (652 mg, 0.6
1
mmol). H-NMR (400 MHz, CDCl
C52H40N2: C, 90.14; H, 5.82; N, 4.04. Found: C, 90.20; H, 5.75;
N, 4.05.
3
) δ (ppm): 8.72-8.64 (m, 1H),
8
.55-8.42 (m, 1H), 7.99 (d, J = 8.0, 4H), 7.84-7.78 (m, 1H), 7.44
Preparation of compound 3: Under a N
mL round bottom flask was charged with compound
.8 mmol), paraformaldehyde (51 mg, 1.7 mmol) and ethyl
2
atmosphere, a 100-
1
3
(
d, J = 8.0, 4H), 7.38-7.05 (m, 33H). C-NMR (100 MHz, CDCl
δ: 180.7, 151.1, 150.6, 148.4, 145.6, 144.1, 138.2, 135.0, 129.7,
28.9, 125.4, 123.9, 122.9, 122.8, 121.1, 62.7 ppm. Anal. Calcd
for C58H45Br3N3Pd: C, 61.64; H, 4.01; N, 3.72. Found: C,
3
)
2
(1.28 g,
1
1
acetate (30 mL). The solution was refluxed for a few minutes,
and then trimethyl chlorosilane (0.283 mL) was added
dropwise. After the mixture was refluxed for 6 h, the resulting
gray white precipitate was isolated via filtration, washed with
6
1.67; H, 4.00; N, 3.67.
General Procedure for Suzuki-Miyaura Coupling Reaction
of aryl chloride with boronic acids. A Schlenk flask was
ethyl acetate and dried under vacuum to give compound
3
as a
white solid. Yield: 50% (0.68 g, 0.9 mmol). H-NMR (400 MHz,
DMSO-d ) δ (ppm): 10.32 (t, J = 4.0, 1H), 8.54 (s, 2H), 7.85 (d, J
8.0, 4H), 7.46 (d, J = 8.0, 4H), 7.35 (t, J = 8.0, 12H), 7.27-7.20
1
charged with aryl chloride (0.25 mmol), boronic acid (0.3
2 3 2
mmol), K CO (0.5 mmol), H O (0.4 mL), isopropanol (0.4 mL)
6
and catalyst. The mixture was stirred at 25 °C. After the
=
1
3
reaction was finished, the mixture was extracted with CH
3× 0.8 mL), washed with water (0.8 mL) and dried over Na
2
Cl
SO
2
(m, 18H). C-NMR (100 MHz, DMSO-d
6
) δ: 153.77, 151.05,
(
2
4
.
137.65, 137.16, 135.57, 133.23, 131.51, 126.69, 69.66 ppm.
The solvent was removed under vacuum. The product was
purified by flash chromatography on a silica gel column.
Anal. Calcd for C53H41ClN2: C, 85.86; H, 5.57; N, 4.78. Found:
C, 85.79; H, 5.52; N, 4.81.
Preparation of complex 4: Under a N
round bottom flask was charged with compound
mmol), 1-tritylimidazole (280 mg, 0.9 mmol), PdCl
.9 mmol) and K CO
3
(276 mg, 2 mmol). The mixture was There are no conflicts to declare.
2
atmosphere, a 25-mL
(740 mg, 1
(160 mg,
3
Conflicts of interest
2
0
2
refluxed in dry THF (10 mL) for 20 h. After cooling to room
temperature, the mixture was filtered and the filtrate was
concentrated in vacuum. The canary yellow product was Acknowledgements
purified by flash chromatography on a silica gel column. Yield:
This work was supported by the Natural Science Foundation of
1
3% (570 mg, 0.5 mmol). H-NMR (400 MHz, CDCl
5
8
8
3
) δ (ppm):
Tianjin (grant Nos. 16JCYBJC19700 and 16JCQNJC03200), the
National Natural Science Foundation of China (grant Nos.
.64 (s, 1H), 8.52 (t, J = 8.0, 1H), 7.99 (d, J = 8.0, 4H), 7.90 (t, J =
1
3
.0, 1H), 7.45 (d, J = 8.0, 5H), 7.35-7.15 (m, 32H). C-NMR (100
) δ: 179.6, 150.3, 146.7, 146.4, 144.5, 134,6, 132.2,
31.7, 131.2, 130.9, 129.9, 127.7, 127.4, 127.0, 125.8, 120.5,
2
1572155 and 21372175) and the Doctoral Fund of Tianjin
MHz, CDCl
3
Normal University (043135202-XB1703).
1
1
7
10.6, 77.0, 64.5 ppm. Anal. Calcd for C75H59Cl2N4Pd: C,
5.47; H, 4.98; N, 4.69. Found: C, 75.50; H, 5.01; N, 4.68.
Notes and references
General Procedure for complexes 5-7: Under a N
atmosphere, a 25-mL flask was charged with compound (740
mg, 1 mmol), PdCl (160 mg, 0.9 mmol), K CO (276 mg, 2
2
1
2
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J. Name., 2013, 00, 1-3 | 5
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DOI: 10.1039/C8NJ01047A
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| J. Name., 2012, 00, 1-3
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Page 7 of 7
New Journal of Chemistry
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DOI: 10.1039/C8NJ01047A
Highly active palladium (II) complexes bearing remote bulky ligands for the
Suzuki-Miyaura coupling reactions under mild condition are reported.