Synthesis, characterization and structural study of a phosphonium salt containing the [Pd2Br6]2- ion and its application as a novel, efficient and renewable heterogeneous catalyst for amination of aryl halides and the Stille cross-coupling reaction

Article abstract of DOI:10.1016/j.poly.2015.11.051

In this study palladium(II) acetate reacts with a phosphonium salt, [Ph₃PCH₂C₆H₄CH₂Br]Br, to give [Ph₃PCH₂C₆H₄CH₂OC(O)CH₃]₂[Pd₂Br₆]. Characterization of the obtained compound was performed by elemental analysis, IR, ¹H, ³¹P, ¹³C NMR and X-ray crystallography. It was found that this compound can act as an efficient catalyst for amination of aryl halides to afford primary amines and satisfactory results were obtained. It has also been successfully employed in the catalytic Stille cross-coupling reaction. The catalyst is easily recoverable and reusable without significant loss of its catalytic activity.

Full text of DOI:10.1016/j.poly.2015.11.051

Accepted Manuscript
Synthesis, characterization and structural study of a phosphonium salt contain-
2
ing the [Pd Br ] ion and its application as a novel, efficient and renewable
-
2
6
heterogeneous catalyst for amination of aryl halides and the Stille cross-coupling
reaction
Ali Naghipour, Arash Ghorbani-Choghamarani, Fateme Heidarizadi, Behrouz
Notash
PII:
S0277-5387(15)00746-9
DOI:
http://dx.doi.org/10.1016/j.poly.2015.11.051
POLY 11697
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
20 October 2015
28 November 2015
Please cite this article as: A. Naghipour, A. Ghorbani-Choghamarani, F. Heidarizadi, B. Notash, Synthesis,
2
characterization and structural study of a phosphonium salt containing the [Pd Br ] ion and its application as a
-
2
6
novel, efficient and renewable heterogeneous catalyst for amination of aryl halides and the Stille cross-coupling
reaction, Polyhedron (2015), doi: http://dx.doi.org/10.1016/j.poly.2015.11.051
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Synthesis, characterization and structural study of a phosphonium salt containing the
2
-
[
Pd
2
Br ] ion and its application as a novel, efficient and renewable heterogeneous
6
catalyst for amination of aryl halides and the Stille cross-coupling reaction
a
a
a
b
Ali Naghipour , Arash Ghorbani-Choghamarani , Fateme Heidarizadi , Behrouz Notash
a
Department of Chemistry, Faculty of Science, Ilam University, Ilam, Iran.
Department of Chemistry, Shahid Beheshti University, Tehran, Iran.
b
Abstract
In this study palladium(II) acetate reacts with a phosphonium salt, [Ph
3
PCH
2
C
6
H
4
CH Br]Br,
2
to give [Ph PCH CH OC(O)CH [Pd Br ]. Characterization of the obtained compound
3
2
C
6
H
4
2
3
]
2
2
1
6
31
13
was performed by elemental analysis, IR, H, P, C NMR and X-ray crystallography. It
was found that this compound can act as an efficient catalyst for amination of aryl halides to
afford primary amines and satisfactory results were obtained. It has also been successfully
employed in the catalytic Stille cross-coupling reaction. The catalyst is easily recoverable and
reusable without significant loss of its catalytic activity.
Keywords: Phosphonium salt, Palladium(II), Amination, C-C coupling.
1
. Introduction
Aniline is one of the most important intermediates in many different kinds of applications,
such as producing agrochemicals, pigments and dyes, pharmaceuticals, rubber processing
chemicals and isocyanates, etc. [1,2]. Hence continuous efforts towards finding more
efficient catalytic reactions under mild conditions, with high turnover numbers and fast
reaction rates are being pursued for the preparation of aniline and its derivatives.
One of the routes for the synthesis of aniline is the reaction of aryl halide with ammonia in
the presence of various transition-metal catalysts; however there are many problems in the
direct utilization of ammonia, which can displace the ligand bound to the metal center
causing the formation of a catalytically non-reactive species [3-5]. Ammonia, as well, has the
tendency to form amido bridges with some catalysts, giving stable structures [6,7]. In
addition, the resultant primary aniline is more active than ammonia, leading to diaryl amines.
Because of these problems, the amination of aryl halides to produce primary aryl amines has
been less studied, while many studies have been done on the production of secondary and
tertiary amines [8-18].
In many studies, at the beginning of the reactions, ammonia equivalents, including
t
(
di)allylamine, buthylcarbamate, imines and sulfoximines, are utilized for the conversion of

Address correspondence to A. Naghipour, Department of Chemistry, Faculty of Science, Ilam
University, P.O. Box 69315516, Ilam, Iran; Tel/Fax: +98 841 2227022; E-mail address:
Naghipour2002@yahoo.com

aryl halides into the corresponding primary aryl amines, and finally deprotection is done [19].
Despite these problems, the use of ammonia as an N-nucleophile is still the most desired
approach due to its low cost and availability [20-29].
Indeed, many researches have accomplished the amination of aryl halides in aqueous
ammonia, but they mostly confronted some constraints, including needing a nitrogen or argon
atmosphere, toxic solvents such as toluene, high temperatures and pressures, special
equipment and materials like autoclaves, dry ice, etc. [30,31]. Recently, phosphonium salts
have attracted considerable attention as effective catalysts for a range of organic reactions,
including oxidation, polymerization, cross-coupling reactions [32,33]. Previously it has been
demonstrated that certain phosphines are suitable ligands for palladium-catalyzed C–C, C–N,
and C–O bond forming reactions [34-36], however, to the best of our knowledge,
phosphonium salts have not been examined for the amination of aryl halides with aqueous
ammonia. Thus, in continuation of our previous works on catalytic reactions [37,38], herein,
in order to obtain primary amines, aqueous ammonia is utilized successfully as an
environmentally friendly direct nitrogen source under air atmosphere and solvent free
conditions. Furthermore we report the catalytic activity of this phosphonium compound for
carbon-carbon bond formation by the Stille cross-coupling reaction using triphenyltin
chloride (Ph SnCl) under green medium to obtain biphenyl derivatives. Biphenyl derivatives
3
have wide range of activities, such as antimicrobial, antifungal, anti-proliferative, anti-
diabetic, immunosuppressant, analgesic, anti-inflammatory, etc [39]. Biphenyl derivatives are
also used as precursors for the synthesis of oligo(p-phenylene)s that have been extensively
studied in the domain of artificial ion channels [40]. Palladium-catalyzed substitution and
addition reactions involving organotin compounds have been used by many research groups
throughout the world for synthetic purposes [41]. This is essentially due to the stability of the
organotin reagents in air and moisture and their compatibility with various functional groups.
2
. Experimental
2
.1. Materials and physical measurements
All reactants and solvents were obtained from Merck, Aldrich and Fluka Chemical
Companies and were used without further purification. Melting points were measured on a
-
1
Stuart SMP
3
apparatus. IR spectra (in the range 4000-400 cm ) were recorded on a Shimadzu
1
4
35-U-04 spectrophotometer and samples were prepared as KBr pellets. NMR spectra ( H,
P and C NMR) were recorded on a 400 MHz Bruker spectrometer in CDCl
3
1
13
3
or DMSO-d
6
as the solvent at room temperature. Elemental analysis was carried out with a CHNS-O
Costech ECS 4010 analyzer. Thin-layer chromatography (TLC) was performed using Merck
silica gel 60 F254 precoated plates (0.25 mm) and visualized by a UV fluorescence lamp.
2
.2. X-ray crystallography
Crystal data of compound 1 were collected using graphite monochromated Mo-Kα radiation
λ = 0.71073 Å) on a STOE IPDS-2T diffractometer at 120(2) K. The molecular structure
(
2
was solved by direct methods and then refined by full-matrix least-squares on F using the X-
STEP32 crystallographic software package [42]. All hydrogen atoms were added in their
geometrically idealized positions. Non-hydrogen atoms were refined with anisotropic thermal

parameters. Cell constants and orientation matrices were obtained by least-squares refinement
of diffraction data from 13453 unique reflections.
2
.3. Synthesis of bis(2-bromomethylbenzyl)triphenylphosphonium hexabromodipalladate(II)
[
Ph PCH CH OC(O)CH [Pd Br ]:
3
2
C
6
H
4
2
3
]
2
2
6
To a solution of 1,2-bis(bromomethyl)benzene (0.263 g, 1 mmol) in benzene (2 mL), a
solution of triphenylphosphine (PPh ) (0.262 g, 1 mmol) in benzene (2 mL) was added and
the resulting mixture was stirred for 4 h at room temperature. The separated solid was filtered
off and washed with diethyl ether (10 mL) to give [Ph PCH CH Br]Br as a white
powder. Yield: 0.446 g (85%). M.p. 180 ˚C. H NMR (400 MHz, CDCl , ppm) δ: 4.27 (s, 2H,
3
3
2
C
6
H
4
2
1
3
1
3
1
CH
2
Br), 5.48 (d, 2H, CH
2
P, J= 15.01 Hz), 6.95-7.72 (m, 19H, Ph). C{ H} NMR (75.45
P, J = 46.04 Hz), 45.60 (s, CH Br), 117.67 (d, C-P),
28.01, 128.13, 128.44, 128.50, 129.18, 129.22, 130.07, 130.24, 131,53, 131,60, 131.71,
MHz, DMSO, ppm) δ: 30.41 (d, CH
1
1
2
2
3
1
1
31.78, 134.26, 134.39, 134.90, 134.94 (C, PPh ). P{ H} NMR (121.50 MHz, DMSO,
3
ppm) δ: 23.66.
The prepared (2-bromomethylbenzyl)triphenylphosphonium bromide (0.526 g, 1 mmol) was
dissolved in 5 mL of ethanol. Then palladium(II) acetate (0.224 g, 1 mmol) in 5 mL of
ethanol was added to this solution and the mixture was stirred at room temperature. After 3
hours, the product was filtered off and washed with diethyl ether (10 mL) to yield
[
˚
(
Ph
C. IR (υ, cm ): 1432 (CH
s, 2H, CH O), 5.13 (d, 2H, CH
(acetate group)), 25.4 (d, CH
3
PCH
2
C
6
H
4
1
CH
2
OC(O)CH
3
]
2
[Pd
2
Br ] as a brown powder. Yield: 0.46 g (60 %). M.p. 268
6
-
1
2
-P), 1106-1160 (C-O). H NMR (400 MHz, CDCl
3
, ppm) δ: 4.29
P, J = 15.1 Hz), 6.97-7.93 (m, Ph). C NMR (75.45 MHz,
P, J = 37 Hz), 55.5 (s, CH O),
17.1-137.9 (Ph), 170.0 (s, C=O). P{ H} NMR (121.50 MHz, DMSO, ppm) δ: 22.6. Anal.
Calc. for C28 P, 0.5(Br Pd ): C, 43.57; H, 3.37. Found: C, 44.05; H, 3.65%.
1
3
2
2
DMSO, ppm) δ: 16.9 (s, CH
1
3
2
2
3
1
1
H
26
O
2
6
2
2
.4. General procedure for amination of aryl halides:
To a solution of the aryl halide (1 mmol) and ammonium hydroxide (28%) (1 mL, 0.003
mmol), 0.005 g (0.003 mmol) of [Ph PCH CH OC(O)CH [Pd Br ] as a catalyst were
3
2
C
6
H
4
2
3
]
2
2
6
added and the reaction mixture was stirred at 60 ˚C for an appropriate time. The progress of
the reaction was followed by TLC. After completion of the reaction, the product was
extracted with ethyl acetate (3 × 10 mL). The combined ethyl acetate extracts were dried over
anhydrous sodium sulfate (1.5 g), filtered and evaporated to give the pure product. The
1
products were characterized by a comparison of their spectral ( H NMR and IR) and physical
data with those of authentic samples.
2
.5. General procedure for the Stille cross-coupling reaction
A mixture of the aryl halide (1 mmol), Ph SnCl (0.4 mmol), K
3
2
CO (1.5 mmol), 0.005 g of
3
[
Ph PCH CH OC(O)CH [Pd Br ] (0.003 mmol) as a catalyst and 1 mL polyethylene
3
2
C
6
H
4
2
3
]
2
2
6
glycol (PEG) as the solvent was heated at 90 ˚C for an appropriate time. After completion of
the reaction, based on TLC, the mixture was cooled to room temperature. The reaction
mixture was added to water (10 mL), filtered (to remove the catalyst) and extracted three
times with diethyl ether (3 × 5 mL). The combined diethyl ether extracts were dried over
anhydrous sodium sulfate (1.5 g), filtered and evaporated to give the pure product. The
1
products were characterized by a comparison of their spectral ( H-NMR and IR) and physical
data with those of authentic samples.

2
.6. General procedure for the recovery of the catalyst
In both catalytic reactions, after completion of the reaction based on TLC, the reaction
mixture was cooled to room temperature. Then water (5 mL) and the organic phase of the
reaction (5 mL), ethyl acetate in the amination reaction or diethyl ether in the Stille cross-
coupling reaction, were added and the mixture was filtered off to separate the catalyst. The
catalyst was dried at 100 ˚C and directly used for the repeated reactions.
2
.7. Representative NMR and IR data
1
Aniline: H NMR (400 MHz, CDCl
3
, ppm) δ : 7.27-7.21 (m, 2H), 6.88-6.84 (tt, J = 7.2, 1
H
-
1
Hz, 1H), 6.78-6.76 (m, 2H), 3.65 (s, 2H). IR (υ, cm ): 3433, 3376, 3298, 3189, 2969, 2916,
1
8
852, 1719, 1633, 1604, 1578, 1508, 1456, 1379, 1298, 1274, 1214, 1164, 1116, 1021, 1004,
74, 862, 811, 779, 742, 722, 703, 572, 552, 488.
1
4
(
-Nitroaniline: H NMR (400 MHz, CDCl
3
, ppm) δ: 8.12-8.10 (d, J = 9.2 Hz, 2H), 6.67-6.65
-1
d, J = 8.8 Hz, 2H), 4.43 (br, 2H). IR (υ, cm ): 3419, 3391, 3096, 3061, 2958, 2927, 2856,
1
1
921, 1733, 1600, 1568, 1515, 1472, 1436, 1398, 1356, 1344, 1306, 1276, 1173, 1120, 1106,
066, 1011, 958, 853, 839, 738, 723, 693, 675, 620, 541, 522.
1
4
4
1
-Cyanoaniline: H NMR (400 MHz, CDCl
3
, ppm) δ: 7.65-7.68 (m, 2H), 7.54-7.58 (m, 2H),
-1
.26 (br, 2H). IR (υ, cm ): 3085, 3032, 2965, 2929, 2860, 2288, 2221, 1915, 1728, 1655,
580, 1475, 1397, 1277, 1176, 1121, 1066, 1010, 960, 823, 767, 746, 722, 699, 540, 430.
1
4
(
-Cyano-1,1'-biphenyl: H NMR (400 MHz, CDCl
3
, ppm) δ: 7.78-7.76 (m, 2H), 7.72-7.68
-1
m, 2H), 7.65-7.62 (m, 2H), 7.53-7.49 (m, 2H), 7.49-7.45 (m, 1H). IR (υ, cm ): 3433, 3066,
2
922, 2351, 2218, 1929, 1637, 1596, 1475, 1398, 1275, 1110, 953, 843, 767, 693, 559, 512.
1
4
(
-Nitro-1,1'-biphenyl: H NMR (400 MHz, CDCl
3
, ppm) δ: 8.32 (d, J = 8.8 Hz, 2H), 7.78
-1
d, J = 8.8 Hz, 2H), 7.66-7.64 (m, 2H), 7.56-7.50 (m, 2H), 7.50-7.46 (m, 1H). IR (υ, cm ):
3
4
447, 3074, 2926, 2840, 1920, 1672, 1591, 1513, 1397, 1344, 1103, 926, 851, 738, 692, 530,
68.
1
4
7
2
-Methoxy-1,1'-biphenyl: H NMR (400 MHz, CDCl
3
, ppm) δ: 7.55-7.60 (m, 4H), 7.43-
-1
.47 (m, 2H), 7.32-7.36 (m, 1H), 7.02 (m, 2H), 3.86 (s, 3H). IR (υ, cm ): 3061, 2997, 2926,
844, 1600, 1524, 1482, 1280, 1248, 1191, 1032, 688.
3
. Results and discussion
3
.1. Synthesis of the catalyst
Initially, (2-methylacetatobenzyl)triphenylphosphonium hexabromodipalladate(II) (1) was
synthesized by the treatment of 1,2-bis(bromomethyl)benzene with PPh in benzene as a
3
solvent, yielding the corresponding phosphonium salt as the exclusive product, as only the
monophosphonium salts are insoluble in benzene (their diphosphonium derivatives are

dissolved in benzene). Subsequently, the reaction of the phosphonium bromide with
palladium(II) acetate in a molar ratio of 1:1 in ethanol at room temperature for 3 h led to the
formation of 1 as a brown solid, as shown in Scheme 1. The observed sharp and singlet peak
3
1
at δ 22.591 ppm in the P NMR spectrum confirmed the purity of the product.
Scheme 1 here
3
.2. X-ray crystallographic study of compound 1
Suitable crystals of compound 1 were obtained by slow evaporation from a dichloromethane
solution over several days and its structure was determined by single-crystal X-ray
diffraction. The anion and cation moieties of the compound are shown in Fig. 1. Compound 1
crystallizes in the triclinic space group P-1 with two molecules in the unit cell. It can be seen
from the ORTEP view of the compound that the geometry of the [Pd
planar and the structure around the phosphorus atom is close to tetrahedral. The bromo group
attached to CH in the ligand structure is replaced by an acetate group in the final compound
2
Br ] moiety is nearly
6
2
structure. Significant crystallographic data are summarized in Table 1 and some selected
bond distances and angles are given in Table 2.
Figure 1 here
Table 1 here
Table 2 here
3
3
.3. Catalytic study
.3.1. Amination of aryl halides
To study the catalytic activity of the synthesized compound (1), the amination reaction of aryl
halides was selected, a reaction that does not proceed in the absence of a catalyst. For this
purpose, aqueous ammonia was used as the supplier of the amine group. Initially,
heterogeneous catalyst optimization was carried out and the optimal amount was found to be
0
.005 g (0.3 mol %). The reaction of iodobenzene with aqueous ammonia was then
performed in various organic solvents and the results are shown in Table 3.
Table 3 here
Optimal conditions for the reaction determined are as follows: 1 mmol of aryl halide, 1 mL of
aqueous ammonia and 0.005 g (0.3 mol%) of catalyst in solvent free conditions. To evaluate
the efficiency of this method, various aryl halides were applied and the results are
summarized in Table 4 (Scheme 2). The products were characterized by spectral techniques
1
(
H NMR and IR). As can be seen, the products were obtained in very good to excellent
yields.
Scheme 2 here

Table 4 here
3
.3.2. Stille cross-coupling reaction
Another reaction studied in this research was the Stille cross-coupling reaction. In order to
determine the most appropriate reaction conditions and evaluate the catalytic efficiency of
compound 1, we studied the influence of the amount of compound 1, solvent and temperature
on the reaction times and yields. Thus, the reaction of iodobenzene, triphenyltin chloride and
potassium carbonate in polyethylene glycol at 90 ˚C was selected as a model reaction and
different amounts of catalyst were investigated. The results are illustrated in Table 5.
Table 5 here
According to Table 5, to prove the true effectiveness of the heterogeneous catalyst, the
reaction without catalyst was performed. It was found that biphenyl was not made after 15
minutes of heating.
Before temperature and base optimization, it was necessary to choose a suitable solvent. For
this purpose, several solvents, including water, N,N-dimethylformamide, ethanol and
polyethylene glycol (PEG), were used. The results are shown in Table 6. Polyethylene glycol
was chosen as the optimal solvent for the reaction. The reason for the PEG selection was the
fact that this solvent is a green solvent. Furthermore it is cheaper than other organic solvents.
Table 6 here
Next the effect of temperature on the rate of the reaction was studied using the reaction of
iodobenzene, triphenyltin chloride and potassium carbonate in the presence of the optimum
quantity of catalyst (Table 7). It was observed that the reaction did not proceed at room
temperature. At 90 ˚C, the reaction proceeded to give the corresponding product in good
yield. A further increase in temperature to 100 ˚C had little effect on the rate of reaction.
Therefore, we kept reaction temperature at 90 ˚C as the optimal temperature.
Table 7 here
Finally, optimization of base was performed in this study. According to Table 8, potassium
carbonate could be selected as the optimum base among used bases.
Table 8 here
The best result was obtained with a 1:0.4:1.5 ratio of aryl halide:triphenyltin chloride:
potassium carbonate with 0.005 g of catalyst at 90 ˚C.
The generality of this reaction was examined using several types of aryl halides, having
electron donating and electron withdrawing groups (Scheme 3). In all cases, the

corresponding products were obtained in good to excellent yield (Table 9). The products were
1
13
characterized by spectral techniques ( H NMR, C NMR and IR).
Scheme 3 here
Table 9 here
As can be seen from Tables 4 and 9, the catalytic system worked exceedingly well in both
reactions with a wide range of substrates under the optimized reaction conditions.
3
.3.3. Recovery of the catalyst
The reusability of catalysts is an important advantage and makes them useful for commercial
applications. For an investigation of the heterogeneous catalyst stability, the activity of the
catalyst was tested for these reactions. The separated catalyst was reused over four
consecutive runs in the amination reaction (column a) and synthesis of biaryl compounds
(
column b), demonstrating excellent recoverability and reusability. The results are presented
in Fig. 2.
Figure 2 here
Conclusion
In this research, an efficient method was used for the amination of aryl halides by aqueous
ammonia in the presence of a phosphonium salt containing palladium(II), which enables the
direct synthesis of a number of primary amines with very good to excellent yields. This
method requires neither a solvent nor a base, which are often used for similar catalytic
amination reactions of aryl halides. Another advantage of this method is the ease of product
separation. Moreover, a small amount of catalyst (0.3 mol%) is required and di- or
triarylamine products were not observed in any reactions. Furthermore we demonstrated that
this compound is an efficient catalyst for the Stille cross-coupling reaction using the
commercially available and cheap reagent triphenyltin chloride. In addition, the reactions
need not be performed under an inert or dry atmosphere. The catalyst showed high activity,
and its reusability was examined for up to four consecutive cycles in both reactions.
1
030177
Acknowledgement
This work was supported by the research facilities of Ilam University, Ilam, Iran.
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Br
Br
PPh Br
3
benzene
r. t.
+
PPh3
Br
PPh Br
PPh3
O
3
EtOH
r. t.
3
+ 2 Pd(OAc)2
2-
[
Pd Br ]
Br
2 6
CCH3
O
2
1
+
[Ph PCH C H CH OCOCH ](CH COO)
3 2 6 4 2 3 3
Scheme 1. Synthesis of [Ph
3
PCH
2
C
6
H
4
CH
2
OC(O)CH
3
]
2
[Pd
2
Br ]
6
NH2
X
[
Ph PCH C H CH OC(O)CH ] [Pd Br ] (Cat.)
3 2 6 4 2 3 2 2 6
+
NH OH
4
0
Solvent free, 60 C
R
R
X= I, Br
Scheme 2. Amination of various aryl halides in the presence of compound 1.
X
R
[
Ph PCH C H CH OC(O)CH ] [Pd Br ] (Cat.)
3 2 6 4 2 3 2 2 6
+
Ph SnCl
3
0
K CO ,PEG, 90 C
2
3
R
X= I, Br
Scheme 3. Synthesis of biaryls in the presence of [Ph
3
PCH
2
C
6
H
4
CH
2
OC(O)CH
3
]
2
[Pd
2
Br ]
6

Figure 1. Asymmetric unit of [Ph
3
PCH
2
C
6
H
4
CH
2
OC(O)CH
3
]
2
[Pd
2
Br ]
6
100
a
b
80
60
40
20
0
1
2
3
4
Cycle
Figure 2. Reuse of the catalyst in the amination (a) and Stille cross-coupling (b) reactions.

Table 1
Crystal data and structure refinement for compound 1.
Chemical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C
28
H
26
O
2
P, 0.5(Br
6
Pd )
2
771.56
120(2)
0.71073
Triclinic
P-1
10.392(2)
12.015(2)
13.601(3)
72.65(3)
71.58(3)
65.73(3)
1440.7(6)
2
b (Å)
c (Å)
ꢀ
(°)
β (°)
ꢀ(°)
ꢁ
3
Volume (Å )
Z
-
1
Absorption coefficient (mm )
4.883
3
Crystal size (mm )
0.15ꢂꢃ.15ꢂ0.05
Crystal F(000)
752
2
Goodness-of-fit on F
0.907
Table 2
Selected bond distances and bond angles for compound 1.
Bond length (Å)
Bond angles (deg.)
Pd(1)–Br(2) 2.410(3)
Pd(1)–Br(1) 2.449(3)
Pd(1)–Br(3) 2.386(3)
Br(3)-Pd(1)-B 92.66(11)
Br(3)-Pd(1)-B 90.32(10)
Br(2)-Pd(1)-B 175.05(11)
P(1)–C(23) 1.778(17) C(23)-P(1)-C( 108.8(10)

P(1)–C(17) 1.78(2)
C(17)-P(1)-C( 108.5(9)
P(1)–C(10) 1.801(17) C(23)-P(1)-C( 109.5(9)
P(1)–C(11) 1.819(17) C(2)-O(1)-C(2 116.7(18)
O(1)–C(2) 1.21(3)
O(2)–C(2) 1.27(3)
O(2)–C(3) 1.45(2)
C(1)–C(2) 1.49(3)
P(1)-C(10)-H( 109.3
Table 3
Effect of solvent on amination of iodobenzene by aqueous ammonia.
Entry solvent
Time (h)
Yield (%)
1
2
Water
7
61
N,N-
7
46
Dimethylformamide
3
4
Ethanol
7
7
55
93
Solvent free
Reaction conditions: iodobenzene: 1 mmol, aqueous ammonia: 1 mL, catalyst: 0.005 g, at 60 ˚C, 7 h.
Table 4
The amination of various aryl halides.
a
Entry
Aryl halide
Product Yield (%) Time (h)
M. p. (˚C)
I
NH2
1
93
90
7
Colorless Oil [43]
Br
NH2
2
15
Colorless Oil [43]

Br
NH2
3
4
5
6
7
8
9
95
89
90
94
92
88
5
18
5
147-149 [44]
42-44 [43]
68-70 [43]
86-88 [45]
136-138 [46]
56-58 [44]
NO2
Br
NO2
NH2
CH3
CH3
NH2
Br
CHO
CHO
NH2
Br
4
CN
Br
CN
NH2
5
NH2
Br
NH2
NH2
9
OCH3
I
OCH3
NH2
93
90
8
6
55-58 [44]
OCH3
OCH3
NH2
I
COOH
COOH
1
0
142-145 [43]
a
Isolated Yield.

Reaction conditions: aryl halide: 1 mmol, aqueous ammonia: 1 mL, catalyst: 0.005 g, at 60 ˚C.
Table 5
Optimization of the amount of compound 1 for the synthesis of biphenyl.
Entry
Compound 1 (g)
Time (min)
Yield (%)
1
2
3
4
0.00
15
15
15
15
0
0.002
65
95
95
0.005
0.007
Reaction conditions: iodobenzene: 1 mmol, Ph
min.
3 2 3
SnCl: 0.4 mmol, K CO : 1.5 mmol, 1 mL PEG, at 90 ˚C, 15
Table 6
Effect of solvent on the synthesis of biphenyl.
Entry solvent Time (min) Yield (%)
1
2
3
4
Water
15
15
15
15
44
86
79
93
N,N-Dimethylformamide
Ethanol
PEG
3 2 3
Reaction conditions: iodobenzene: 1 mmol, Ph SnCl: 0.4 mmol, K CO : 1.5 mmol, at 90 ˚C, 15 min.
Table 7
The effect of temperature on the synthesis of biphenyl.
Temperature (˚C) Compound 1 (g)
Time (min)
Yield (%)
2
6
9
5
0
0
0.005
0.005
0.005
0.005
15
15
15
15
0
55
95
1
00
95
Reaction conditions: iodobenzene: 1 mmol, Ph
3
SnCl: 0.4 mmol, K
2
3
CO : 1.5 mmol, 1 mL PEG, 15 min.

Table 8
Optimization of base in the Stille cross-coupling reaction
Base
Time (min)
Yield (%)
Potassium carbonate (K
2
CO
3
)
15
15
15
15
94
90
65
75
Potassium hydroxide (KOH)
Triethylamine (Et N)
Sodium bicarbonate (NaHCO
3
3
)
Reaction conditions: iodobenzene: 1 mmol, Ph
5 min, at 90 ˚C.
3
SnCl: 0.4 mmol, base: 1.5 mmol, 1 mL PEG, catalyst: 0.005 g,
1
Table 9
Stille cross-coupling for the synthesis of biaryls from aryl halides.
a
Entry Aryl halide
Product Yield (%) Time (min)
M. p. (˚C)
I
Ph
1
95
93
10
15
61-63 [47]
Br
Ph
2
62-64 [47]
Br
Ph
3
96
92
95
8
109-111 [48]
NO2
Br
NO2
Ph
4
35
10
42-44 [48]
56-58 [48]
CH3
Br
CH3
Ph
5
CHO
CHO

Br
Ph
6
7
8
94
90
91
8
82-84 [48]
49-51 [48]
82-84 [48]
CN
Br
CN
Ph
40
25
NH2
Br
NH2
Ph
OCH3
I
OCH3
Ph
9
1
1
93
92
95
15
15
10
82-84 [48]
116-119 [49]
75-77 [48]
OCH3
OCH3
I
Ph
COOH
COOH
0
1
Br
Ph
Cl
I
Cl
Ph
1
2
3
94
91
25
43-44 [48]
CH3
CH3
Br
Ph
1
15
Colorless Oil [48]
CF3
CF3
a
Isolated Yield.
Reaction conditions: iodobenzene: 1 mmol, Ph
3
SnCl: 0.4 mmol, K
2
3
CO : 1.5 mmol, PEG: 1 mL, catalyst: 0.005
g, at 90 ˚C.

Graphical Abstract
NH2
R
t
s
y
l
a
t
a
C
0
C
,
0
H
6
O
,
X
e
H 4
e
r
f
Catalyst
N
t
n
e
v
l
o
S
P
h
3
S
R
n
K
2
C
C
l
,
O
3
C
a
,
talys
9
X= I, Br
0 0
C
t
,
P
E
Ph
G
R