Synthesis, crystal structure study and high efficient catalytic activity of di-μbromo-trans–dibromobis[(benzyl)(4-methylphenyl)(phenyl)phosphine] dipalladium(II) in Suzuki–Miyaura and Heck–Mizoroki C–C coupling reactions

Article abstract of DOI:10.1016/j.poly.2016.08.040

The current research aims to present a straightforward synthesis of binuclear palladated triphenylphosphine derivative by the reaction of the phosphonium salt [(PhCH₂)P(Ph)₂(Ph-4-CH₃)]Br with palladium(II) chloride and to afford the dimeric palladated complex {Pd[P(Ph)(CH₂Ph)(Ph-4-CH₃)]((μ-Br)Br)}₂. Moreover, elemental analysis (CHN), FT-IR, 1H, 31P, 13C NMR and X-ray crystallography led to the characterization of the obtained compound. Finally, This compound was found to be an efficient catalyst in C–C bond formation between various aryl halides with phenylboronic acid (Suzuki–Miyaura reaction) and aryl halides with n-butyl acrylate (Heck–Mizoroki reaction).

Full text of DOI:10.1016/j.poly.2016.08.040

Accepted Manuscript
Synthesis, crystal structure study and high efficient catalytic activity of di-
μbromo-trans–dibromobis[(benzyl)(4-methylphenyl)(phenyl)phosphine)] di-
palladium(II) in Suzuki-Miyaura and Heck-Mizoroki C–C coupling reactions
Arash Ghorbani-Choghamarani, Ali Naghipour, Heshmatollah Babaee,
Behrouz Notash
PII:
S0277-5387(16)30399-0
DOI:
http://dx.doi.org/10.1016/j.poly.2016.08.040
POLY 12177
Reference:
Polyhedron
To appear in:
Received Date:
Revised Date:
Accepted Date:
5 August 2016
24 August 2016
24 August 2016
Please cite this article as: A. Ghorbani-Choghamarani, A. Naghipour, H. Babaee, B. Notash, Synthesis, crystal
structure study and high efficient catalytic activity of di-μbromo-trans–dibromobis[(benzyl)(4-methylphenyl)
(phenyl)phosphine)] dipalladium(II) in Suzuki-Miyaura and Heck-Mizoroki C–C coupling reactions, Polyhedron
(2016), doi: http://dx.doi.org/10.1016/j.poly.2016.08.040
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Synthesis, crystal structure study and high efficient catalytic activity of di-µbromo-trans–
dibromobis[(benzyl)(4-methylphenyl)(phenyl)phosphine)] dipalladium(II) in Suzuki-
Miyaura and Heck-Mizoroki C–C coupling reactions
Arash Ghorbani-Choghamarani a,∗, Ali Naghipour a, Heshmatollah Babaee a, Behrouz Notash b
a Department of Chemistry, Faculty of Science, Ilam University, P.O. Box 69315516, Ilam, Iran.
b Department of Chemistry, Shahid Beheshti University, Tehran, Iran.
Abstract
The current research aims to present a straightforward synthesis of binuclear palladated
triphenylphosphine derivative by the reaction of the phosphonium salt
[(PhCH2)P(Ph)2(Ph-4-CH3)]Br with palladium(II) chloride and to afford the dimeric
palladated complex {Pd[P(Ph)(CH2Ph)(Ph-4-CH3)]((µ-Br)Br)}2. Moreover, elemental
1
analysis (CHN), FT-IR, H, 31P, 13C NMR and X-ray crystallography led to the
characterization of the obtained compound. Finally, This compound was found to be an
efficient catalyst in C-C bond formation between various aryl halides with phenylboronic
acid (Suzuki-Miyaura reaction) and aryl halides with n-butyl acrylate (Heck–Mizoroki
reaction).
Keywords Phosphonium salt, Palladium(II) chloride, Suzuki reaction, Heck reaction
:
1. Introduction
In organometallic chemistry, phosphines have been considered as significant ligands since
they have been extensively applied in organic reactions. Phosphine ligands are soft, strong
σ-donors and their electronic, steric, and stereo-chemical properties vary based on the
multiple substitutes connected to the phosphorus atoms [1-4]. Hence, the correct phosphine
for a metal complex needs to be selected in order to influence the electronic and steric
environment of the complex. Such a characteristic is most beneficial for maximizing the
activity of homogeneous catalysts. Therefore, plenty of phosphine containing
homogeneous catalysts has been developed for various organic reactions including
hydrogenation, cross couplings, and carbon-hetero atom bond formations [5-8].
Palladium-catalyzed carbon–carbon coupling reactions have been recognized as powerful
method and major area of interest in organic synthesis, advanced materials, agrochemicals,
pharmaceuticals, herbicides, biologically active compounds, polymers, preparation of
∗
Address correspondence to A. Ghorbani-Choghamarani; Department of Chemistry, Faculty of Science, Ilam
University, P.O. Box 69315516, Ilam, Iran; Tel/Fax: +98 84 32227022; E-mail address: a.ghorbani@mail.ilam.ac.ir or
arashghch58@yahoo.com
1

hydrocarbons and liquid crystal materials, and building blocks in macromolecular
chemistry [9–13]. Coupling of aryl halides with alkenes and arylboronic acids have
substantial significance, and are well-established methodologies in novel organic synthesis
[14]. Nowadays, researchers have developed different efficient palladium precatalysts,
which permit aryl halides to be effectively coupled with olefins [15] and aryl boronic acids
[16] without exclusion of air. Considering that catalytic activities can be effectively
modulated by the electronic and steric properties of the ligands, palladium complexes
containing phosphine ligands are intensively investigated [17,18].
Recently, researchers have developed diverse homogeneous palladium-phosphine catalysts
for the efficient cross-coupling reactions [19,20], however, they mostly have not yielded
good results on the process of joining of less reactive aryl halides substrates in Suzuki and
Heck coupling reactions. Moreover, in order to achieve better conversions, high loading of
catalysts and an inert atmosphere in most reactions, especially one involving phospha–
pallada cycles are required [21].
In this paper, we report the synthesis, characterization and crystal structure determination of di-µ
bromo-trans–dibromobis[(benzyl)(4-methylphenyl)(phenyl)phosphine)] dipalladium(II) complex
as novel and efficient catalyst for the C-C bond formation in coupling reactions in the presence of
phenylboronic acid (Suzuki reaction) and n-butyl acrylate (Heck reaction) under mild reaction
conditions.
2. Experimental
2.1. Materials and physical measurements
The required chemicals were purchased from commercial sources and used without further
purification. Melting points were measured on a Stuart SMP3 apparatus and are reported without
correction. Elemental analysis was carried out with a CHNS-O costech ECS 4010 analyzer. IR
spectra were recorded on a Shimadzu 435-U-04 spectrophotometer from KBr pellets. NMR
spectra (1H, 31P and 13C NMR) recorded on a 400 MHz Bruker spectrometer in DMSO-d6 or
CDCl3 as the solvent at room temperature. Chemical shifts (δ) are reported based on internal TMS
and external 85% phosphoric acid. Thin-layer chromatography (TLC) was performed using Merck
silica gel 60 F254 precoated plates (0.25 mm) and visualized by UV fluorescence lamp.
2.2. X-ray crystallography
The single crystal X-ray diffraction data of suitable crystals of 2 was collected on a STOE IPDS-II
diffractometer at 120(2) K, using graphite monochromated Mo Ka radiation (0.71073 Å). The data
collection was performed using the ω-scan technique and using the STOE X-AREA software
package [22], whereas data diminution was carried out using the program X-RED [23]. The
structure was solved by direct methods and subsequent difference Fourier maps and then refined
on F2 by full-matrix least-squares procedures using the programs SHELX and SHELXL
2

respectively [24], and all refinements were performed using the XSTEP32 crystallographic
software package [25]. All hydrogen atoms were added in geometrically idealized positions.
2.3. Synthesis of [(PhCH2)P(Ph)2(Ph-4-CH3)]Br (1)
A solution consisting of diphenyl(p-tolyl)phosphine (0.691 g, 2.5 mmol) and then a
solution (10 ml) benzyl bromide (0.427 g, 2.5 mmol) in dry toluene (15 mL) was stirred for
6 h at room temperature. The separated solid was filtered off and washed with diethyl ether (10
mL) to give [(PhCH2)P(Ph)2(Ph-4-CH3)]Br as a white powder. Yield: 1.04 g, 96%. M.p.: 255-
258 °C. Anal. Calc. for C26H24BrP (446.08 g/mol): C, 69.81; H, 5.41. Found: C, 69.3; H,
5.30%. IR (KBr disk, ϑ cm-1): 1586 (C=C), 687-900 (C-H in Ph), 1436 (P-CH2), 2790-
1
2717 (CH3). H NMR (400 MHz, CDCl3, ppm)
δ
: 6.32-6-35 (d, 2H, PCH2); 2.27 (s, 3H,
CH3); 7.02-7.60 (m, 19H, Ph). 31P{1H} NMR (162 MHz, CDCl3, ppm)
P(Ph)2(PhCH3)(CH2Ph)). C NMR (100 MHz, CDCl3, ppm) δ: 36.12 (d, JCP = 17.02 Hz,
PCH2); 20.05 (s, CH3); 127.02, 127.51, 128.23, 128.73, 129.18, 129.22, 130.12, 130.82,
131.39, 131.75, 134.23 (d, J = 9.80 Hz); 134.73 (d, J = 12.1 Hz), (Ph).
δ
: 20.38 (s,
13
2.4. Synthesis of {Pd[P(Ph)(CH2Ph)(Ph-4-CH3)]((µ-Br)Br)}2 (2)
To a stirred suspension of [(PhCH2)P(Ph)2(Ph-4-CH3)]Br (0.669 g, 1.5 mmol) in dry methanol (15
ml), palladium(II) chloride (0.265 g, 1.5 mmol) was slowly added. The resulting solution was set
to reflux for 2 h. After this time, to the aforementioned mixture was added a solution 37% NaOH
(3.5 mL, 2.0 M) in a dropwise fashion over 30 min. The resulting solution was stirred at room
temperature for 24 h. The suspension that formed was filtered off, washed with diethyl ether and
dried to give {Pd[P(Ph)(CH2Ph)(Ph-4-CH3)]((µ-Br)Br)}2 as an orange powder. Yield: 0.134 g,
85%. M.p.: 215 °C. Anal. Calc. for C40H38Br4P2Pd2 (1113.72 g/mol): C, 43.16; H, 3.44. Found: C,
43.02; H, 3.18%. IR (KBr disk, ϑ cm-1): 1495-1587 (C=C), 689-900 (C-H in Ph), 1438 (P-CH2),
1
2917 (CH3). H NMR (400 MHz, CDCl3, ppm) δ: 5.34 (d, 4H, J = 14.33 Hz, PCH2); 2.43 (s, 6H,
CH3); 7.02-7.80 (m, 28H, Ph). 31P{1H} NMR (162 MHz, CDCl3, ppm) δ: 22.78 (s,
13
P(Ph)(PhCH3)(CH2Ph)). C NMR (100 MHz, CDCl3, ppm) δ: 38.12 (d, JCP = 16.13 Hz, PCH2);
21.89 (s, CH3); 127.61, 128.18, 128.55, 131.34, 131.73, 133.08, 133.28, 133.33, 134.31, 134.43,
136.12 (d, J = 14.23 Hz); 137.27 (d, J = 16.72 Hz), (Ph).
2.5. General procedure for Suzuki cross-coupling reaction
A mixture of aryl halide (1 mmol), phenylboronic acid (1 mmol), K2CO3 (1.5 mmol), 0.005 g of
give {Pd[P(Ph)(CH2Ph)(PhCH3)]((µ-Br)Br)}2 as catalyst and 2 mL polyethylene glycol (PEG) as
solvent were heated at 100 °C using an oil bath and the progress of the reaction was monitored by
TLC. After completion of the reaction, catalyst was separated and washed three times with diethyl
ether. The reaction mixture was extracted with water and diethyl ether and organic layer dried
3

over anhydrous sodium sulfate (1.5 g). Then the solvent was evaporated and pure biphenyl
derivatives were obtained in good to excellent yields.
2.6. General procedure for Heck reaction
A mixture of aryl halide (1 mmol), n-butyl acrylate (1.2 mmol), K2CO3 (1.5 mmol), 0.010 g of
give {Pd[P(Ph)(CH2Ph)(PhCH3)]((µ-Br)Br)}2 as catalyst and 2 mL polyethylene glycol (PEG) as
solvent were heated at 120 °C using an oil bath and the progress of the reaction was monitored by
TLC. After completion of the reaction, the mixture was cooled down to room temperature and
then catalyst was separated, washed with diethyl ether and the reaction mixture was extracted with
water and diethyl ether. The organic layer was dried over sodium sulfate (1.5 g), evaporated to
obtain pure products in good to excellent yields.
2.7. Selected Spectral data
Biphenyl (Table 4, entry 1-3): 1H NMR (400 MHz, CDCl3, ppm): δ: 7.33-7.37 (m, 2H), 7.46-7.51
(m, 4H), 7.63 (d, J = 7.5Hz, 4H);
4-Methyl-1,1'-biphenyl (Table 4, entries 4,5): 1H NMR (400 MHz, CDCl3, ppm): δ= 7.64-7.67 (m,
2H), 7.55-7.57 (m, 2H), 7.46-7.51 (m, 2H), 7.36-7.41 (tt, J =7.12 Hz, 1H), 7.30-7.32 (d, J = 8.21
Hz, 2H), 2.46 (s, 3H).
4-Cyano-1, 1'-biphenyl: (Table 4, entries 6-7): 1H NMR (400 MHz, CDCl3, ppm) δ: 7.76-7.79 (m,
2H); 7.69-7.71 (m, 2H); 7.62 -7.64 (m, 2H); 7.53-7.55 (m, 2H); 7.44-7.48 (m, 1H).
1
4-Chloro-1, 1’-biphenyl (Table 4, entry 8): H NMR (400 MHz, CDCl3, ppm): δ: 7.58- 7.61 (m,
2H), 7.53-7.56 (m, 2H), 7.44-7.49 (m, 4H), 7.37-7.41 (tt, J=7.6 Hz, 1H).
1
4-Nitro-1, 1'-biphenyl (Table 4, entries 9-10): H NMR (400 MHz, CDCl3, ppm) δ: 8.30 (d, J =
8.38 Hz, 2H), 7.75 (d, J = 7.8 Hz, 2H), 7.65–7.67 (m, 2H), 7.50–7.55 (m, 2H), 7.44–7.48 (m, 1H).
1
4-methoxy-1,1'-biphenyl (Table 4, entries 11-12): H NMR (400 MHz, CDCl3, ppm) δ: 7.56-7.60
(m, 4H); 7.44-7.49 (m, 2H); 7.32-7.37 (m, 1H); 7.03-7.7.05 (m, 2H); 3.89 (s, 3H).
1
(E)-n-Butyl cinnamate (Table 6, entries 1-3): H NMR (400 MHz, CDCl3, ppm): δ: 7.68 (d, J =
16.40 Hz, 1 H), 7.51-7.53 (m, 2 H), 7.38-7.42 (m, 3 H), 6.44 (d, J = 15.67 Hz, 1 H), 4.25 (t, J =
6.07 Hz, 2 H), 1.62-1.70 (m, J = 7.32 Hz, 2 H), 1.45 (m, J = 6.95 Hz, 2 H), 0.98 (t, J = 6.49 Hz,
3H).
1
(E)-n-Butyl 3-(4-methylphenyl)acrylate (Table 6, entries 4,5): H NMR (400 MHz, CDCl3, ppm)
δ: 7.68-7.72 (d, J=15.87 Hz, 1H), 7.47-7.49 (d, J=8.10 Hz, 2H), 7.20-7.23 (d, J=7.32 Hz, 2H),
6.43-6.47 (d, J=15.85 Hz, 1H), 4.21-4.26 (t, J=13.42 Hz, 2H), 2.47 (s, 3H), 1.67-1.74 (quint,
J=6.64 Hz, 2H), 1.46-1.50 (sixt, J= 7.46 Hz, 2H), 0.99-1.04 (t, J=7.66 Hz, 3H).
4

(E)-n-Butyl 3-(4-methoxyphenyl)acrylate (Table 6, entries 6,7): 1H NMR (400 MHz, CDCl3, ppm)
δ: 7.63-7.67 (d, J=15.62 Hz, 1H), 7.48-7.52 (d, J=6.18 Hz, 2H), 6.92-6.96 (d, J=7.2 Hz, 2H), 6.32-
6.36 (d, J=15.78 Hz, 1H), 4.21-4.25 (t, J= 6.44 Hz, 2H), 3.87 (s, 3H), 1.67-1.71 (quint, J=5.79 Hz,
2H), 1.44-1.50 (sixt, J=9.23 Hz, 2H), 0.98-1.05 (t, J= 6.86 Hz, 3H).
1
(E)-n-Butyl 3-(4-Cyanophenyl)acrylate (Table 6, entries 8,9): H NMR (400 MHz, CDCl3, ppm):
δ: 7.69-7.81 (d, J = 15.0 Hz, 1H), 7.41-7.45 (m, 2H), 7.33-7.40 (m, 3H), 6.36-6.39 (d, J = 17.70
Hz, 1H), 4.23-4.26 (t, J = 6.8 Hz, 2H), 1.62-1.68 (m, J = 7.15 Hz, 2H), 1.45 (m, J = 7.7 Hz, 2H),
0.86 (t, J = 7.5 Hz, 3H).
1
(E)-n-Butyl 3-(4-nitrophenyl)acrylate (Table 6, entries 10,11): H NMR (400 MHz, CDCl3, ppm):
δ: 7.69-7.72 (d, J = 15.51 Hz, 1H), 7.45-7.48 (m, 2H), 7.29-7.31 (m, 3H), 6.38(d, J = 17.20 Hz,
1H), 4.20 (t, J = 5.17 Hz, 2H), 1.60-1.63 (m, J = 6.2 Hz, 2H), 1.50 (m, J = 6.75 Hz, 2H), 0.93 (t, J
= 6.54 Hz, 3H).
3. Results and discussion
3.1. Catalyst characterization
In order to synthesize phosphonium salt, a solution containing diphenyl(p-tolyl)phosphane and
benzyl bromide, in toluene, was stirred at room temperature for 6 h. The resulting suspension was
filtered off and the obtained precipitate was washed with diethyl ether and then toluene, and
subsequently dried to give the related monophosphonium salt 1 as white powder. As the
monophosphonium salt is insoluble in toluene, the only product of the reaction is the
monophosphonium compound, with high purity. Moreover, the treatment of the phosphonium
bromide salt 1 with palladium (II) chloride and aqueous solution of NaOH in a molar ratio of 1:1:1
in methanol at room temperature for 24 h, followed by addition of diethyl ether, afforded the
binuclear palladium phosphine complex 2 as orange precipitate. It seems that at beginning the
monophosphonium salt in basic medium disproportionate on phosphine and phenol, then the
phosphine react with PdCl2 to from the binuclear palladium phosphine complex (Scheme 1). As it
is mentioned in experimental section and also in Scheme 1, these reactions led to the easy
synthesis of the palladium phosphine complex 2 as well as the phosphonium salt. The observed
sharp and singlet peak at δ: 22.78 ppm in the 31P NMR spectrum confirmed the purity of binuclear
palladium phosphine compound 2.
Scheme 1 here
3.2. X-ray crystallographic study of compound 2
Suitable crystals of complex 2 were obtained from a methanol/chloroform solution by slow
evaporation of the solvent over several days and its structure was determined by single-crystal X-
ray diffraction. The complex crystallized was done in the monoclinic space group P21/c with two
molecules in the unit cell. The structure of this compound contains of dinuclear units of palladium
5

(II) atoms bridged through double µ-bromo bridges (Fig. 1). Each palladium(II) centre is bound to
one phosphine ligand by its P atom and three bromide atoms (two Br atoms adopts µ2-bridged
mode and one Br atom as terminal mode) in a slightly distorted square-planar geometry. Relevant
parameters concerning the data collection and refinement are summarized in Table 1 and some
selected bond distances and angles are listed in Table 2. Crystallographic data for the complex 2 in
this paper can be found in the Supplementary Information.
Figure 1 here
Table 1 here
Table 2 here
3.3. Catalytic study
3.3.1. Application of the catalyst in the Suzuki cross coupling reaction
In order to examine the catalytic activity of Pd(II) complex in the Suzuki reaction, the
reaction between iodobenzene with phenyl boronic acid in presence of catalyst
2 was
chosen as model reaction. Influences of different parameters such as base, temperature,
solvent and catalyst concentration were examined to obtain the best possible combination.
As shown in Table 3, the coupling reaction yields were susceptible to temperature in the
presence of 5 mg catalyst and PEG-400 as solvent (Table 3, entries 3, 12-14). The increase
of reaction temperature up to 100 °C led to high yield 96% (Table 3, entry 3).
Nevertheless, when the temperature increased to 120 °C, the yield of the desired product
did not increase obviously (Table 3, entry 14). During the optimization process, it was
found that the best yields were obtained in the presence of 5 mg of catalyst at 100 °C
(Table 3, entry 3). The higher amount of catalyst was not found to be beneficial and the
lower amount of the catalyst had a deteriorating effect (Table 3, entries 1-3). The next
parameter, which was optimized, is solvent from the usually used ones. The examined
organic solvents were PEG-400, DMF, DMSO, EtOH and H2O (Table 3, entries 3, 5–7).
Results showed that PEG was the best solvent for the reaction. Finally, we then tested the
effect of bases and among the examined bases; K2CO3 was the most effective base for the
coupled product in presence of catalyst (Table 3, entry 3).
Table 3 here
After optimizing the reaction conditions, the scope of the reaction was explored with
various aryl halides with electron-withdrawing and electron donating groups and
phenylboronic acid. The results are summarized in Table 4. As illustrated in Table 4, the
coupling of aryl iodides and aryl bromides proceeded smoothly at 100 °C and the
6

corresponding products were obtained in excellent yields and high activity. The coupling
reaction of aryl chlorides with phenylboronic acid needed more reaction time than aryl
iodides and bromides, which gives us the desired product in good yield.
Table 4 here
3.3.2. Catalyst testing for the Heck-Mizoroki reaction
After the investigations of the Suzuki reaction of various aryl halides, we sought to check
the catalytic performance of described catalyst in Heck coupling reactions. In order to
optimize reaction conditions, the effect of different solvents, bases, reaction temperature
and amount of catalyst were studied through a model reaction of iodobenzene with n-butyl
acrylate. As shown in Table 5, various solvents such as DMSO, DMF, polyethylene glycol
400 (PEG-400) and H2O were tested. PEG was found to be the most appropriate media,
giving the C-C coupling product in a 95% yield (Table 5, entry 1-4). In next step, we
examined the effects of different bases on the Heck reaction in PEG-400. The organic and
inorganic bases including, K2CO3, NaOAc, KHCO3 and Et3N were investigated (Table 5,
entries 3, 6-8). As illustrated in Table 5, K2CO3 was the best base for the reaction in term
of reaction yield. Various amounts of catalyst between 5 and 15 mg were further
investigated for this reaction, and 10 mg catalyst was found to be optimal amount (Table 5,
entry 3). An increase of temperature from 80 to 120 °C promotes the reaction significantly
(Table 5 entries 3, 12 and 13). Nevertheless, when the temperature increased to 130 °C, the
yield of the desired product did not increase obviously (Table 5 entry 14).
Table 5 here
After optimizing the reaction conditions, the scope of the reaction was explored with
various substituted aryl halides with electron-withdrawing and electron-releasing groups
and butyl acrylate. Satisfactory catalytic activity was observed in the couplings of the aryl
iodides with butyl acrylates. The aryl bromides possessing electron-donating group
demonstrated a slight drop in reactivity compared to the aryl iodides possessing electron-
withdrawing groups. Moreover, the coupling of aryl bromides with n-butyl acrylate
proceeded at 120 °C and the corresponding products were obtained in high yields. To
extend the scope of our work, we next examined the coupling of various aryl chlorides with
n-butyl acrylate under the optimized reaction conditions (Table 6).
Table 6 here
7

3.3.3. Comparison of the catalyst
The results of the coupling of iodobenzene with phenylboronic acid (Table 7) were compared with
some reported carbon-carbon coupling reactions in the presence of other catalysts to examine the
efficiency of these procedures. Table 7 indicates that this catalyst has higher reaction yield and
shorter reaction time than the other catalysts. Particularly, the reaction catalyzed by
{Pd[P(Ph)(CH2Ph)(PhCH3)]((µ-Br)Br)}2 can be performed efficiently without using toxic organic
solvent moreover this new catalyst is a proper catalyst with easier separation and higher stability
than the previously reported works.
Table 7 here
4. Conclusions
To sum up, the present method is an attractive and easy way of performing the synthesis of
phosphine ligand and one of their palladium derivatives. This synthesized complex 2 was highly
active and efficient catalyst in promoting the Suzuki and Heck cross-coupling reactions of various
aryl halides to produce the corresponding products in a moderate to good yields under relatively
mild experimental conditions. The ease of precursor preparation of the catalyst, low catalyst
loading, and its high solubility in organic solvents make these compounds as ideal starting
materials for the described transformations.
Acknowledgements
Authors thank the research facilities of Ilam University, Ilam, Iran, for financial support of this
research project
Appendix. Supplementary data
CCDC No. 1440747 contains the Supplementary crystallographic data for the compound. These
data can be obtained free of charge via http://www.ccdc.ac.uk/conts/retriving.html, or from the
Cambridge crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ,UK; fax: (+44)
1223-336-033; or email:deposit@ccdc.cam.ac.uk
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& Cie GmbH: Darmatadt, Germany, 2005.
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Darmstadt, Germany, 2000.
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CH3
Br-
Br
P+
P
toluene
(1)
CH3
PdCl2
methanol
NaOH
H3C
Br
P
Br
Pd
Pd
Br
Br
P
CH3
( )
2
Scheme 1. Synthesis of {Pd[P(Ph)(CH2Ph)(Ph-4-CH3)]((µ-Br)Br)}2.
10

Figure 1. X-ray crystal structure of {Pd[P(Ph)(CH2Ph)(Ph-4-CH3)]((µ-Br)Br)}2.
11

Table 1. Crystal data and structure refinement for compound 2.
Identification code
{Pd[P(Ph)(CH2Ph)(Ph-4-CH3)]((µ-Br)Br)}2 (2)
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C40H38Br4P2Pd2
1113.08
120(2)
0.71073
Monoclinic
P21/c
10.441(2)
13.840(3)
14.481(6)
90.00
b (Å)
c (Å)
α(°)
β (°)
γ(°)
112.87(2)
90.00
3
1928.1(10)
Volume (Å )
Z
2
Calculated density, Mg/m3
F(000)
1.917
1080
Theta range for data collection, (°)
Limiting indices
Completeness to theta = 25.00
Absorption correction
Absorption coefficient (mm-1)
Crystal size (mm3)
Reflections collected/ unique
Max. and min. transmission
Refinement method
2.54 to 25.00
-10≤h≤12, -16≤k≤16, -17≤l≤17
99.9 %
Numerical
5.189
0.12ꢀ×ꢀ0.12 × 0.10
3396/1376[ R(int) =0.213]
0.6249 and 0.5748
Full-matrix least-squares on F2
3396 / 3 / 134
Data/restraints/ parameters
Goodness-of-fit on F2
Final R indices [I>2 δ (I)]
R indices (all data)
0.908
R1 = 0.2343, WR2 = 0.971
R1 = 0.1852, WR2 = 0.1507
0.990 and -1.293
Largest diff. peak and hole, e Å-3
12

Table 2. Selected bond lengths (A˚) and bond angles (°) for compound 2.
Bond Lengths
Bond Angles
Pd(1)-P(1)
Pd(1)-Br(1)
Pd(1)-Br(2)
Pd(1)-Br(2)
P(1)-C(1)
P(1)-C(7)
P(1)-C(14)
C(7)-C(8)
C(19)-C(20)
C(14)-C(15)
C(14)-C(16)
C(19)-C(17)
C(19)-C(18)
2.214(5)
P(1)-Pd(1)-Br(1)
89.61(15)
94.13(14)
173.57(12)
176.5(2)
89.58(9)
86.37(8)
93.63(8)
106.2(12)
103.8(10)
104.7(9)
114.2(8)
107.9(7)
118.9(6)
2.383(3)
2.447(3)
2.515(2)
1.84(2)
1.850(19)
1.80(2)
1.48(3)
1.45(3)
1.36(3)
1.39(3)
1.43(3)
1.38(3)
P(1)-Pd(1)-Br(2)
Br(1)-Pd(1)-Br(2)
P(1)-Pd(1)-Br(2)
Br(1)-Pd(1)-Br(2)
Br(2)-Pd(1)-Br(2)
Pd(2)-Br(2)-Pd(1)
C(14)-P(1)-C(1)
C(14)-P(1)-C(7)
C(1)-P(1)-C(7)
C(14)-P(1)-Pd(1)
C(1)-P(1)-Pd(1)
C(7)-P(1)-Pd (1)
Table 3. Optimization of the reaction conditions for the Suzuki reaction of iodobenzene with
phenylboronic acid using catalyst 2.
Ph
B(OH)2
I
Catalyst, Base
+
Solvent, Temprature
Entry
1
2
3
4
5
6
7
8
Cat. (mg)
Solvent
PEG
PEG
PEG
PEG
DMF
DMSO
EtOH
H2O
PEG
PEG
PEG
PEG
PEG
PEG
Base
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
NaOAc
Et3N
Temp (°C)
100
100
100
100
100
100
100
100
100
100
100
r.t.
Time (min)
Yield (%)a
--
2
5
7
5
5
5
5
5
5
5
5
5
5
120
55
25
30
25
25
25
25
25
25
25
25
25
25
--
74
96
97
80
88
75
45
90
80
82
--
9
10
11
12
13
14
KHCO3
K2CO3
K2CO3
K2CO3
80
120
74
96
aIsolated yields.
13

Table 4. Suzuki cross-coupling reaction of aryl halides and phenyl boronic acid using catalyst 2.a
Ph
B(OH)2
X
Catalyst, K2CO3
PEG, 100 °C
+
I
R
R
Entry
1
Aryl halide
Product
Time (min) Yield (%)b
Mp (°C)
68 [26]
Ph
Ph
Ph
Ph
25
30
60
96
95
90
Br
Cl
I
2
3
68 [26]
68 [26]
4
5
35
40
93
91
45-47 [27]
45-47 [27]
H3C
H3C
Br
Ph
H3C
H3C
Br
Ph
Ph
Ph
6
7
8
45
75
55
87
86
90
84-86 [9]
84-86 [9]
76-77 [26]
NC
NC
Cl
NC
NC
Cl
Cl
Br
Br
Ph
Ph
Ph
Ph
9
50
90
35
89
84
91
111-113 [9]
111-113 [9]
86-88 [26]
O2N
O2N
O2N
Cl
10
11
O2N
I
H3CO
H3CO
Br
12
45
88
86-88 [26]
H3CO
H3CO
aReaction conditions: aryl halide (1 mmol), phenyl boronic acid (1 mmol), K2CO3 (1.5 mmol), 5 mg catalyst
at 100 ˚C.
b Isolated yield.
14

Table 5. Optimization of the reaction conditions for the Heck reaction of iodobenzene with n-butyl
acrylate acid using catalyst 2.
O
O
I
Catalyst, Base
OC4H9
+
OC4H9
Solvent, Temprature
Entry Cat. (mg) Solvent
Base
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
--
NaOAc
KHCO3
Et3N
K2CO3
K2CO3
K2CO3
Temp (°C)
120
Time (min)
Yield (%)a
1
2
3
5
5
5
5
DMSO
DMF
PEG
H2O
45
45
45
45
45
45
45
45
45
45
45
45
45
45
71
64
75
35
--
95
96
--
89
70
81
--
77
96
120
120
120
120
120
120
120
120
120
120
r.t.
100
4
5
6
7
8
--
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
10
15
10
10
10
10
10
10
10
9
10
11
12
13
14
130
bIsolated yields.
Table 6. Heck reaction of aryl halides and n-butyl acrylate using catalyst 2.a
O
O
X
Catalyst, K2CO3
OC4H9
+
OC4H9
PEG, 120 °C
R
R
Aryl halide
Entry
1
Product
Time (min) Yield (%)b
Mp (°C)
O
I
Pale yellow
liquid [28]
45
55
95
92
OC4H9
OC4H9
O
Br
Pale yellow
liquid [28]
2
15

O
Cl
Pale yellow
liquid [9]
3
4
95
55
89
90
OC4H9
O
I
Pale yellow
liquid [26]
OC4H9
H3C
H3C
O
Br
Pale yellow
liquid [26]
OC4H9
OC4H9
OC4H9
5
6
7
70
45
65
89
93
90
H3C
H3C
O
I
Pale yellow
liquid [27]
H3CO
H3CO
H3CO
O
Br
Pale yellow
liquid [27]
H3CO
O
O
Br
Cl
8
9
95
89
84
43-46 [26]
43-46 [26]
OC4H9
OC4H9
OC4H9
NC
NC
NC
NC
120
O
Br
Cl
10
85
87
59–61 [27]
O2N
O2N
O
11
95
86
59–61 [27]
OC4H9
O2N
O2N
aReaction conditions: aryl halide (1 mmol), n-butyl acrylate (1 mmol), K2CO3 (1.5 mmol), 10 mg catalyst at 120 ˚C.
bIsolated yield.
16

Table 7. Comparison results of {Pd[P(Ph)(CH2Ph)(Ph-4-CH3)]((µ-Br)Br)}2 with other catalysts for the coupling
of iodobenzene with phenylboronic acid
Entry
catalyst
Condition
Time Yield
(min)
Ref.
%
{Pd[P(Ph)(CH2Ph)(PhCH3)]
((µ-Br)Br)}2
1
PEG, K2CO3, 100 ºC
25
96
This work
2
3
Pd-MPTAT-1
NaOH, DMF: H2O (1:5), 85 ºC
DMF, Cs2CO3, 130 ºC
8h
95
95
[29]
[30]
PdCl2
120
N,N'-bis(2-
4
pyridinecarboxamide)-1,2-
benzene palladium complex
NHC-Pd(II) complex
H2O, K2CO3, 100 ºC
180
97
[31]
5
6
THF, Cs2CO3, 80 ºC
K2CO3, 1,4-dioxane: H2O (1:1),
95 ºC
12h
4h
88
91
[32]
[33]
PANI-Pd
7
8
CA/Pd(0)
PVP–PdNPs
Pd/Au NPs
Pd NP
H2O, K2CO3, 100 ºC
K2PO4, EtOH/H2O, 90 ºC
EtOH/H2O, K2CO3, 80 ºC
H2O, KOH, 100 ºC
120
120
24h
12h
94
94
88
95
[34]
[35]
[36]
[37]
9
10
aIsolated yield
17

Graphical Abstract
Synthesis, crystal structure study and high efficient catalytic activity of di-
µbromo-trans–dibromobis(benzylphenylparatulylphosphine) dipalladium(II)
in Suzuki-Miyaura and Heck-Mizoroki C–C coupling reactions
Arash Ghorbani-Choghamarani,* Ali Naghipour, Heshmatollah Babaee, Behrouz Notash
18