Aqueous Suzuki coupling reaction catalyzed by water-soluble diimine/Pd(II) systems

Article abstract of DOI:10.1016/j.jorganchem.2008.11.060

A series of water-soluble diimine ligands were applied for the Suzuki reaction of arylbromide in different media. Low loading of catalyst (0.01 mol%) were necessary for the coupling reaction to proceed in water or water/ethanol. The catalytic system was found to tolerate a broad range of functional groups.

Full text of DOI:10.1016/j.jorganchem.2008.11.060

Journal of Organometallic Chemistry 694 (2009) 697–702
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Aqueous Suzuki coupling reaction catalyzed by water-soluble
diimine/Pd(II) systems
*
Jin Zhou, Xuming Guo, Changzheng Tu, Xiaoyan Li, Hongjian Sun
School of Chemistry and Chemical Engineering, Shandong University, Shanda Nanlu 27, 250100 Jinan, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 10 October 2008
Received in revised form 24 November 2008
Accepted 25 November 2008
Available online 7 December 2008
A series of water-soluble diimine ligands were applied for the Suzuki reaction of arylbromide in different
media. Low loading of catalyst (0.01 mol%) were necessary for the coupling reaction to proceed in water
or water/ethanol. The catalytic system was found to tolerate a broad range of functional groups.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Suzuki coupling
Water-soluble
Diimine
Palladium
Aqueous
1. Introduction
ous Suzuki coupling, and this catalytic system could be efficiently
reused in 12 reaction cycles.
In the past two decades, the palladium-catalyzed Suzuki cou-
pling reaction of aryl halides with arylboronic acids has evolved
into one of the most important and powerful methods to form biar-
yls [1–3] and has been extensively used in the synthesis of phar-
maceuticals [4,5], ligands [6], polymers [7], and advanced
materials [8,9].
As a well-known family of ligands, diimines have been applied
in many catalytic processes, such as in the notable olefin polymer-
ization [28,29]. Nolan and his co-workers [30,31] have reported the
use of Pd(OAc)2/DAB-Cy (N,N0-dicyclohexyl-1,4-diazabutadiene)
system for the Suzuki reaction and Heck reaction. Herein, we re-
ported a series of disulfonated water-soluble
a-diimine ligands
Lots of highly active supporting ligands have been developed
for Suzuki coupling reaction, such as phosphine ligands [10,11],
N-heterocyclic carbene ligands [12–14], palladacycle [15–18].
Recently, Suzuki reaction in aqueous phase including neat water
and water/organic co-solvent has also received much more atten-
tion. Casalnuovo initially reported the palladium-catalyzed cross-
ing-coupling reactions in aqueous solvents catalyzed by TPPMS/
Pd(OAc)2 [19]. Several water-soluble analogues of phosphines have
been developed for the Suzuki coupling reactions [20–22]. Di-2-
pyridylmethylamine-based palladium complexes [23,24] have
been shown to be versatile catalysts for Heck, Suzuki and Sono-
gashira reactions in organic and aqueous solvents. Nájera and co-
workers [25,26] reported a new oxime-carbapalladacycle with
hydroxy substituents on the aromatic ring as a highly active cata-
lyst for arylchloride Suzuki coupling reaction in water with TBAB
(tetrabutylammonium bromide) as an additive. Another water-
soluble palladacyle [27] supported by a water-soluble phosphine
ligand (t-Bu-Amphos) has been prepared and applied for the aque-
as supporting ligands for the Suzuki cross-coupling reaction in or-
ganic solvents and in aqueous phase.
2. Results and discussion
2.1. Synthesis of ligands and Pd(II) complex
2,6-Di(alkyl)aniline was first sulfonated with concentrated sul-
phuric acid at 200 °C, followed by neutralization with NaOH or
NaOCH3 to form the sodium salts. The ionic sulfonated
a-diimine
ligands (Table 1) were prepared by condensing an -dione (2,3-
a
butanedione, acenaphthenequinone, or 40% aqueous glyoxal) with
the corresponding sulfonated anilines in methanol with a catalytic
amount of formic acid. The sulfonated ligands are easily diffluent
and stable in neat water and water–organic co-solvents. Ligands
9, 10 and 11 were synthesized as yellow powders by an ion ex-
change reaction between the ligand 4 (or 5) and excess 1-butyl-
3-methylimidazolium chloride (BmimCl) or tetrabutylammonium
chloride (TBAC) in iso-propanol.
Single crystals of ligand 11 suitable for X-ray diffraction were
obtained from iso-propanol solution. The molecular structure of
* Corresponding author. Tel.: +86 0531 88361350; fax: +86 0531 88564464.
E-mail address: hjsun@sdu.edu.cn (H. Sun).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.11.060

698
J. Zhou et al. / Journal of Organometallic Chemistry 694 (2009) 697–702
Table 1
Table 1 continued
Influence of diimine ligands.a
Ligand
9d
Structure
Yieldb,c
>99
B(OH)2
Br
Bu4NO3S
N
N
SO3NBu4
+
Ligand
1
Structure
Yieldb,c
40
a
Reaction condition: 1.0 mmol bromobenzene, 1.3 mmol phenylboronic acid,
2 mmol K2CO3, 3 mol% Pd(OAc)2, 3.3 mol% ligand, 2 ml DMA, 80 °C, 1 h.
b
GC conversion based on bromobenzene.
All reactions were monitored by GC, yields are average of two runs.
95 °C 1 h or 80 °C 2.5 h.
c
NaO3S
N
N
N
N
SO3Na
SO3Na
d
2
60
NaO3S
NaO3S
3
4
58
71
N
N
N
SO3Na
NaO3S
NaO3S
N
N
SO3Na
SO3Na
5
6
74
25
N
Fig. 1. ORTEP Drawing of Ligand 11. Ellipsoids are given at the ꢀ30% probability
level.
NaO3S
NaO3S
N
N
SO3Na
ligand 11 is depicted in Fig. 1. The C1–N1@C7–C7A@N1A–C1A
moiety is planar, and has transoid arrangement with respect to
the centre C7–C7A. The molecule has an inversion centre. Both
imine groups assume an (E)-configuration to avoid repulsion be-
tween the substituted phenyl groups. The four ethyl groups are ori-
ented toward the two different sides of the phenyl planes,
respectively.
Furthermore, two new diimine palladium complexes 1 and 2
were synthesized from the reaction between the ligand 5 and suit-
able palladium precursor in anhydrous methanol (Scheme 1).
These two complexes were also both easily diffluent and stable
in neat water and water/organic co-solvents. Solutions of these
complexes could be stored for several weeks without decomposi-
tion (1H NMR) and decrease of the catalytic activity.
7
8
22
27
N
N
SO3Na
NaO3S
N
N
N
N
SO3Na
9
10
11
85
82
81
Bu4NO3S
SO3NBu4
2.2. Influence of the diimine ligands on Suzuki reaction
We initiated the research of Suzuki reaction in the organic sol-
vents in order to study the influence of the diimine ligands (Table
1). Coupling reaction of bromobenzene and phenylboronic acid
was selected as a model reaction. DMA (dimethyl acetamide) was
used as the solvent, and K2CO3 as the base. The similar reactivity
trend with Nolan’s report [30] is in agreement with the stronger
donating ability of alkyl substituents, making the donor atoms
more electron-rich. In the series of ligands (1–8), ligand 5 gave
the highest yield while the acenaphthenequinone and glyoxal dii-
mines gave low or moderate yields. Using [Bmim]+ or [NBu4]+ in-
stead of [Na]+ the yields improved. But the mechanisms leading
BmimO3S
BmimO3S
N
N
N
N
SO3Bmim
SO3Bmim

J. Zhou et al. / Journal of Organometallic Chemistry 694 (2009) 697–702
699
NaO3S
N
N
SO3Na
NaO3S
N
N
SO3Na
Pd
Pd
Cl
OAc
Cl
AcO
Complex 1
Complex 2
Scheme 1.
to improved yields were different. The ionic liquid ligand 11 (li-
gand 11 could be considered as a special ionic liquid) could be
deprotonated at the 2-position of [Bmim]+ by the base to form a
carbene catalytic precursor [14,32] while the [NBu4]+ of ligand 9
stabilizes the active Pd(0) species. The ligand 9 was selected for Su-
zuki coupling of aryl halide and aryl boronic acid.
Table 2
Suzuki coupling of aryl halides and various arylboronic acid.a
B(OH)2
X
+
z
Y
z
Y
2.3. Suzuki coupling of aryl halides and various arylboronic acid
Entry
X
Y
Z
t (h)
GC conv. (isolated yield)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17c
18c
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Cl
H
H
H
H
H
H
H
H
H
1.5
1
2
1
1
2
1.5
5
5
3.5
5
100 (99)
100 (98)
100 (98)
100 (97)
100 (93)
100 (97)
100 (99)
95 (92)
95 (93)
98 (95)
96 (95)
100 (97)
96 (94)
99 (90)
98 (96)
99 (97)
20
The catalytic system was applicable to a wide range of aryl bro-
mides and chloride (Table 2). The electron-deficient aryl bromides
showed an excellent reactivity and gave nearly quantitative yields
in short reaction times (Table 2, entries 2–6). A prolongation of
reaction time was required for the electron-rich and sterically hin-
dered aryl bromides (Table 2, entries 7–10). The coupling reaction
of active aryl chloride gave moderate yields at higher reaction tem-
perature (Table 2, entries 18, 19) while the coupling reaction of
chlorobenzene and the unactivated chloride showed much lower
reactivity and yields (Table 3, entries 17, 20). The coupling of 4-
bromochlorobenzene with the phenylboronic acid gave 4-chlorobi-
phenyl in 93% isolated yield with a little other coupling by-product
which was not identified (Table 2, entries 5). It was also shown that
the coupling of arylboronic acid and bromobenzene gave high
yields (Table 2, entries 12–16).
4-COMe
2-CHO
3-NO2
4-Cl
4-NH2
4-Me
4-OMe
2-Me
4-Ph
1-Naph
H
H
H
H
4-Me
4-OMe
4-Cl
4-Me
4-Me
H
1.5
2
3
H
H
4-Me
4-OMe
H
3
4.5
24
24
Cl
4-NO2
H
78 (76)
a
Reaction condition: 1.0 mmol aryl halide, 1.3 mmol arylboronic acid, 2 mmol
K2CO3, 3 mol% Pd(OAc)2, 3.3 mol% ligand 9, 2 ml DMA, 95 °C.
2.4. Suzuki reaction in aqueous phase
b
All reactions were monitored by GC, yields are average of two runs.
c
120 °C.
The use of neat water as solvent is attractive because of the
complete elimination of organic solvent. It is shown that the
Table 3
Pd source screening of aqueous Suzuki coupling.a
Br
B(OH)2
OMe
+
OMe
Entry
Catalyst
Catalyst (mol%)
Solvent
TBAB
T (°C)
t (h)
Yieldb
1
2
3
4
5
6
7
8
9
Complex 1
Complex 2
PdCl2
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.1
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
0
0
75
75
75
75
75
75
75
100
70
50
18
70
4
4
70c
57c
56
47
92
67
85e
98
99
99
93
98
0.5
0.5
0.5
0.5
0.5
0
0
0
0
0
1.5
1.5
1.5
1.5
1.5
45 min
1.5
3
Li2PdCl4
Complex 1
Complex 2
Complex 1
Complex 1
Complex 1
Complex 1
Complex 1
Complex 1
H2O/EtOHd
H2O/EtOHd
H2O/EtOHd
H2O/EtOHd
10
11
12
0.1
0.0001
12
10
a
Reaction conditions: 1 mmol of 4-bromoanisole, 1.3 mmol of 4-methylphenylboronic acid, 2 mmol of K2CO3, 5 ml of H2O, N2.
Isolated yields.
Toluene produced.
EtOH:H2O = 1 ml:1 ml, under air.
Reacted under air.
b
c
d
e

700
J. Zhou et al. / Journal of Organometallic Chemistry 694 (2009) 697–702
Table 5
reaction yields are moderate in neat water without any additive at
75 °C (Table 3, entry 1). The addition of 0.5 equiv. of TBAB to the
reaction mixture greatly accelerated the reaction and decreased
the yields of arene formed from protodeboronation of the boronic
acid. The role of the ammonium salt is thought to be twofold.
Firstly, it facilitates solvation of the arylhalide in neat water. Sec-
ondly, it accelerates the coupling reaction by formation of a boro-
nate complex [ArB(OH)3]ꢀ[R4N]+ [33,34]. The complete conversion
and 99% isolated yield were obtained when the reaction was car-
ried out at 100 °C with no toluene and only a trace of 4,40-dimeth-
ylbiphenyl (Table 3, entries 8) as by-products. The reaction in
water under air showed a bit lower conversions than the reaction
under nitrogen (Table 3, entries 5, 7). When the Suzuki coupling of
4-bromoanisole and 4-methylboronic acid was run in EtOH/H2O
under air, shorter reaction times were necessary compared to the
water system with TBAB as an additive. High yields were also ob-
tained at lower reaction temperature (room temperature or 50 °C)
with 0.1 mol% loading of complex 1 for the EtOH/H2O co-solvent
system (Table 3, entries 10, 11). Complex 1 is a more active species
compared to the complex 2 and other palladium precursors for the
aqueous Suzuki coupling.
Recycling of catalyst.a
Entry
Catalyst (mol%)
Reaction yield by cycleb
1
2
3
4
1
2
0.01
0.1
97
99
61
90
0
60
10
a
Reaction condition: 1.0 mmol 4-bromoanisole, 1.3 mmol phenylboronic acid,
2 mol K2CO3, 100 °C, 5 ml H2O.
b
GC yield.
the coupling reaction could be accomplished in short time in
nearly quantitative yields. It is worth noticing that the catalytic
system was found to tolerate a wide range of functional group,
such as NO2, OMe, OH, Cl, NH2 (Table 4). The coupling of 4-bromo-
chlorobenzene with the phenylboronic acid showed good selectiv-
ity and gave exclusively 4-chlorobiphenyl in 99% yield (Table 4,
entry 3). Due to the steric hindrance and solubility of substrates,
reactions in neat water appear to be more sensitive to steric bulk
on the aryl bormide than in the water/ethanol system, as 2-bromo-
toluene gave 80% of the coupling product with phenylboronic acid
in neat water, while the yield in water/ethanol was up to 98% (Ta-
ble 4, entry 9A and B). The ammonium salt additive were not nec-
essary for the coupling reaction of 4-bromophenol with Method A
because of its water-solubility in basic aqueous phase (Table 4, en-
try 11). The coupling reactions of aryl chloride and phenylboronic
acid were carried out at 120 °C with 1 mol% catalyst and 1.0 equiv.
TBAB except for 4-nitrochlorobenzene. It was shown that the con-
version of activated aryl chloride was up to 98%. But the conversion
of unactivated aryl chloride was very low.
The Suzuki coupling of aryhalide and arylboronic acid in water
(Method A) or water/ethanol (Methods B and C) system (Table 4)
was studied. The reaction times were not optimized because all
Table 4
Aqueous Suzuki coupling of aryl halides and various arylboronic acid.a
B(OH)2
X
+
z
Y
z
Y
2.5. Catalyst recycling
Entry
1
X
Y
Z
Method
Isolated yield (%)b
The potential recyclability of the catalysts derived from diimine/
Pd system was also explored in the model cross-coupling of 4-
bromoanisole and phenylboronic acid (Table 5). The reaction was
carried out in water at 100 °C. After cooling to room temperature,
the organic products were extracted by ethyl ether and the yields
were determined by GC. The aqueous phase was then transferred
to a new reaction flask for the next cycle. It was shown that the cou-
pling reaction using 0.1 mol% catalyst could be reused by two cycles
and the yield significantly dropped for the third cycle. Employing
lower amounts of catalyst (0.01 mol%), the yield of the second cycle
dropped to 60%, and little product for the third cycle.
Br
Br
H
H
A
B
A
B
C
A
B
A
B
C
99
99
98
99
95
99
99
99
99
90
97
98
25
93
97
98
96
99
80
92
98
98
95
98
98
20g
<5g
2
4-Me
H
3
4
Br
Br
4-Cl
H
H
4-OMe
5
6
7
8
9
Br
Br
Br
Br
Br
4-OMe
4-OMe
4-OMe
4-OMe
2-Me
4-Me
A
B
4-Me
4-OMe
4-Cl
H
Cc
C
A
B
A
B
A
B
3. Conclusion
A series of new ionic diimine ligands were applied for the high
yield Suzuki coupling reaction of arylbromide and arylboronic acid
in organic solvent, neat water and water/ethanol co-solvent sys-
tem. Very low loading of catalyst (0.01 mol%) were necessary for
the coupling reaction in water or EtOH/water co-solvent system.
An addition of TBAB greatly accelerated the rate of coupling reac-
tion and decreased the formation of by-products in neat water at
lower temperatures. The coupling reactions could be smoothly car-
ried out at room temperature with low loading of catalyst
(0.1 mol%). The catalytic system tolerates a broad range of func-
tional groups on the phenyl ring.
Bd
A
Ae
C
A
A
A
10
11
Br
Br
3-NO2
4-OH
H
H
12
Cl
Cl
Cl
4-NO2
H
4-CH3
H
H
H
13f
14f
a
Reaction condition: 1.0 mmol aryl halide, 1.3 mmol arylboronic acid, 2 mmol
K2CO3, reaction time not optimized, Method A: 0.01 mol% Complex 1, 5 ml deion-
ized water, 75 °C, 0.5 equiv. TBAB, under N2, 3–5 h. Method B: 0.01 mol% Complex 1,
EtOH/H2O = 1 ml:1 ml, 70 °C, under air, 1.5–2 h. Method C: same to method B, but
0.1 mol% catalyst, r.t. (about 18–20 °C), 10 h.
4. Experimental
b
All isolated yields, average of two runs.
0.01 mol% catalyst, 24 h.
0.02 mol% catalyst.
No additive.
1 mol% catalyst, 120 °C, 1 equiv. TBAB.
GC yield.
c
4.1. Materials
d
e
f
Alkyl substituted sulfonated aniline sodium salts [35,36],
Disulfonated diimine ligands [37,38] and [Bmim]Cl [39] were pre-
g

J. Zhou et al. / Journal of Organometallic Chemistry 694 (2009) 697–702
701
pared according to literature methods. All solvents were purchased
and purified according to standard methods. Other reagents were
used as received without further purification.
4.4. General procedure of Suzuki coupling reaction in organic solvent
A 25-ml-two-necked flask was equipped with a magnetic stir
bar and purged with nitrogen gas. 0.03 mmol of Pd(OAc)2,
0.033 mmol of ligands and 2 ml of DMA were added into the flask
under N2. The mixture was stirred for 30 min at room temperature.
Then 1 mmol of arylhalide, 1.3 mmol of arylboronic acid and
2 mmol of powdered K2CO3 were added into the flask under nitro-
gen. The reaction mixture was stirred and heated at reaction tem-
perature for appropriate time. It was then cooled to room
temperature, diluted with water, and extracted with CH2Cl2 for
three times. The organic phase was dried with Na2SO4 and concen-
trated to yield an oil or solid. The crude material was flash chro-
matographed on a short silica gel column eluting with a mixture
of ethyl acetate and petrol ether (the purified products were iden-
tified by 1H NMR spectra).
4.2. Apparatus
All NMR spectra were recorded at Bruker 300 or 400 MHz Spec-
trometer using CDCl3 or CD3OD. GC is Zheda Zhida 9790 with a
SE-30 GC column. Elementar analyses were carried out on Elemen-
tar Vario EL III.
4.3. Synthesis of ligands and complexes
4.3.1. Synthesis of ligands
Ligands (1–8) were prepared in the light of our recent publica-
tion [40].
Ligand 9: Ligand 5 (0.20 g, 0.33 mmol) and TBAC (0.24 g,
0.86 mmol) were added into 30 ml of isopropanol. The mixture
was stirred at 60 °C for 24 h. The yellow solid was gradually dis-
solved, and white NaCl precipitated. After cooling and filtration
the volatiles were completely removed in vacuo. The yellow resi-
due was recrystallized in iso-propanol and delivered ligand 9 as
yellow power (0.31 g, 91%).
4.5. General procedure of aqueous Suzuki coupling reaction
A 25-ml-two-necked flask was equipped with a magnetic stir
bar. Complex 1 and 5 ml of H2O (Method A) or EtOH/H2O
(1 ml:1 ml, Methods B and C) were added into the flask. Then
1 mmol of aryl bromide, 1.3 mmol of arylboronic acid and 2 mmol
of powdered K2CO3 were added into the flask under nitrogen if
necessary. The reaction mixture was stirred at the pre-arranged
temperature for appropriate reaction time. It was then cooled to
room temperature, diluted with water, and extracted with CH2Cl2
for three times. The organic phase was dried with Na2SO4 and con-
centrated to yield an oil or a solid. The crude material was flash
chromatographed on a short silica gel column.
IR (KBr): 1647 cmꢀ1
(m (m
C@N), 1188 cmꢀ1 S@O). 1H NMR
(300 MHz, CD3OD): d 7.80 (s, 4H) 3.09 (t, 4H), 2.79–2.87 (m, 4H),
2.15 (s, 6H), 1.48–1.56 (m, 4H), 1.34 (d, 12H), 1.28–1.21 (m,
16H), 0.84 (t, 6H).
Ligands 10 and 11 were synthesized by the reaction of ligand 5
or 4 with excess [Bmim]Cl in isopropanol.
Ligand 10: IR (KBr): 1647 cmꢀ1, ( C@N) 1188 cmꢀ1 S@O). 1H
m (m
NMR (400 MHz, DMSO-d6): d 0.90 (t, 6H), d 1.10 (d, 12H), 1.15 (d,
12H), 1.25 (m, 4H), 1.76 (m, 4H), 2.00 (s, 6H), 2.67 (m, 4H), 3.36
(s, 6H), 4.16 (m, 4H), 7.42 (s, 4H), 7.72 (s, 2H), 7.79 (s, 2H), 9.18
(s, 2H). Anal. Calc. for C44H68N6O6S2: C, 62.83; H, 8.15; N, 9.99.
Found: C, 62.41; H, 7.98; N, 10.24%.
4.6. Recycling of catalyst
A vial was charged with complex 1, K2CO3 2 mmol, and phenyl-
boronic acid 1.3 mmol. To this mixture were added water (5 ml)
and 4-bromoanisole (1.0 mmol). The reactions were run at 100 °C
for 1 h. After the reaction mixture was cooled to room tempera-
ture, diethyl ether (5 ml) was added and stirring was continued
for 1 min. The aqueous phase was transferred to another vial for
the next reaction cycle. The yields were determined by GC using
n-dodecane as an internal standard.
Ligand 11: IR (KBr): 1648 cmꢀ1 C@N), 1190 cmꢀ1 S@O). 1H
(m (m
NMR (400 MHz, DMSO-d6): d 0.90 (t, 6H), 1.08 (t, 12H), 1.25 (m,
4H), 1.76 (m, 4H), 1.98 (s, 6H), 2.32 (q, 8H), 3.85 (s, 6H), 4.16 (m,
4H), 7.36 (s, 4H), 7.72 (s, 2H), 7.79 (s, 2H), 9.18 (s, 2H). Anal. Calc.
for C40H60N6O6S2: C, 61.20; H, 7.70; N, 10.70. Found: C, 61.32; H,
7.88; N, 10.43%.
4.3.2. Synthesis of complex 1
4.7. 1H NMR of the coupling product
0.50 g (0.82 mmol) of ligand 5 and 0.31 g (0.82 mmol) of
PdCl2(PhCN)2 was dissolved in 20 ml of absolute methanol.
The mixture was stirred for 10 h at room temperature under
nitrogen. All the volatiles were removed in vacuo after filtration.
The residues were recrystallized from methanol/ethyl ether and
Biphenyl 1H NMR (CDCl3): d 7.59–7.57 (m, 4H), 7.45–7.40 (m,
4H), 7.35–7.30 (m, 2H).
4-Methylbiphenyl 1H NMR (CDCl3): d 7.54 (d, 2H), 7.45 (d 2H),
7.37 (t, 2H), 7.27 (t, 1H), 7.19 (d, 2H), 2.34 (s, 3H).
4-Methoxybiphenyl 1H NMR (CDCl3): d 7.57–7.52 (m, 4H), 7.42 (t,
2H), 7.30 (t, 1H), 6.98 (d, 2H), 3.85 (s, 3H).
delivered the complex
1 as an orange solid (0.55 g, 86%).
M.p. > 250 °C.
1H NMR (400 MHz, CD3OD): d 7.77 (s, 4H), 3.31–3.22 (m, 4H),
2.23 (s, 6H), 1.48 (d, J = 6.8 Hz, 12H), 1.28 (d, 12H, J = 6.8 Hz). Anal.
Calc. for C28H38N2Na2O6S2PdCl2: C, 42.78; H, 4.87; N, 3.56. Found:
C, 42.62; H, 5.10; N, 3.42%.
2-Methylbiphenyl 1H NMR (CDCl3 ): d 7.43–7.35 (m, 2H), 7.34–
7.27 (m, 3H), 7.26–7.18 (m, 4H), 2.27 (s, 3H).
4-Acetylbiphenyl 1H NMR (CDCl3): d 8.04 (d, 2H), 7.67 (d, 2H),
7.62 (d, 2H), 7.55–7.30 (m, 3H), 2.64 (s, 3H).
4-Chlorobiphenyl 1H NMR (CDCl3): d 7.68–7.33 (m 9H).
4.3.3. Synthesis of complex 2
1
Biphenyl-4-carbaldehyde H NMR (CDCl3): d 9.98 (s, 1H), 8.03 (d,
0.70 g (1.15 mmol) of ligand 5 and 0.26 g (1.15 mmol) of
Pd(OAc)2 were dissolved in 20 ml of absolute methanol. The mix-
ture was stirred for 10 h at room temperature. After filtration of
the palladium black, the volatiles were removed in vacuo. The res-
idues were recrystallized from methanol/ethyl ether and delivered
complex 2 as an orange solid (0.65 g, 68%). M.p. > 250 °C.
1H NMR (300 MHz, D2O): d 7.42 (s, 4H), 2.89 (s, 6H), 2.74 (s, 6H),
2.60–2.55 (m, 4H), 1.07 (d, 12H), 1.01 (d, 12H). Anal. Calc. for
C32H44N2Na2O10S2Pd: C, 46.13; H, 5.32; N, 3.36. Found: C, 45.81;
H, 5.52; N, 3.60%.
1H), 7.67–7.61 (m, 1H), 7.52–7.36 (m, 7H).
3-Nitrobiphenyl 1H NMR (CDCl3): d 8.43 (s, 1H), 8.18 (d, 1H), 7.90
(d, 1H), 7.62–7.56 (m, 3H), 7.51–7.39 (m, 3H).
p-Terphenyl 1H NMR (CDCl3): d 7.68–7.55 (m, 8H), 7.46 (t, 4H),
7.37 (t, 2H).
4-Aminobiphenyl 1H NMR (CDCl3): d 7.52 (d, 2H), 7.48–7.35 (m,
4H), 7.25 (t, 1H), 6.71 (d, 2H), 3.66 (s, 2H).
4,40-Dimethoxybiphenyl 1H NMR (CDCl3): d 7.47 (d, 4H), 6.95 (d,
4H), 3.83 (s, 6H).

702
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7.45 (d, 2H), 7.22 (d, 2H), 6.96 (d, 2H), 3.83 (s, 3H), 2.38 (s, 3H).
40-Methylbiphenyl-2-carboxaldehyde 1H NMR (CDCl3): d 9.98 (s,
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4-Phenylphenol 1H NMR (CDCl3): d 7.56–7.25 (m, 6H), 6.91 (d,
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4-Chloro-40-Methoxybiphenyl 1H NMR (CDCl3): d 7.51–7.46 (m,
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4-Nitro-4-methylbiphenyl 1H NMR (CDCl3): d 8.25 (d, 2H), 7.72 (d,
2H), 7.53 (d, 2H), 7.30 (d, 2H), 2.42 (s, 3H).
1-Phenylnaphthalene 1H NMR (CDCl3): d 7.92–7.71 (m, 3H), 7.48–
7.36 (m, 9H).
2-Aminobiphenyl 1H NMR (CDCl3): d 7.42–7.28 (m, 5H), 7.12 (t,
1H), 6.82 (t, 1H), 6.72 (d, 1H), 3.58 (s, 2H).
4-Nitrobiphenyl 1H NMR (CDCl3 ): d 8.27 (d, 2H), 7.71 (d, 2H),
7.70–7.34 (m, 5H).
Acknowledgments
This work was supported by NSFC No. 20372042, Shandong Sci-
entific Plan 032090105 and the Science Foundation of Shandong
Y2006B18.
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Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2008.11.060.
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