Highly efficient polymer-stabilized palladium heterogeneous catalyst: Synthesis, characterization and application for Suzuki–Miyaura and Mizoroki–Heck coupling reactions

Article abstract of DOI:10.1002/aoc.5121

A suitable approach to stabilize palladium nanoparticles (Pd NPs), with an average diameter of 3–4 nm, on magnetic polymer is described. A new magnetic polymer containing 4′-(4-hydroxyphenyl)-2,2′:6′,2″-terpyridine (HPTPy) ligand was prepared by the polymerization of itaconic acid (ITC) as a monomer and trimethylolpropane triacrylate (TMPTA) as a cross-linker and fully characterized. Pd NPs embedded on the magnetic polymer were successfully applied in Suzuki–Miyaura and Mizoroki–Heck coupling reactions under low palladium loading conditions, and provided the corresponding products with excellent yields (up to 98%) and high catalytic activities (TOF up to 257 hr^?1). Also, the catalyst can be easily separated and reused for at least consecutive five times with a small drop in catalytic activity.

Full text of DOI:10.1002/aoc.5121

Received: 26 February 2019
DOI: 10.1002/aoc.5121
Revised: 23 June 2019
Accepted: 25 June 2019
F U L L P A P E R
Highly efficient polymer‐stabilized palladium
heterogeneous catalyst: Synthesis, characterization and
application for Suzuki–Miyaura and Mizoroki–Heck
coupling reactions
1
2
1,3
Homa Targhan | Alireza Hassanpour | Kiumars Bahrami
1
Department of Organic Chemistry,
A suitable approach to stabilize palladium nanoparticles (Pd NPs), with an
average diameter of 3–4 nm, on magnetic polymer is described. A new mag-
netic polymer containing 4′‐(4‐hydroxyphenyl)‐2,2′:6′,2″‐terpyridine (HPTPy)
ligand was prepared by the polymerization of itaconic acid (ITC) as a monomer
and trimethylolpropane triacrylate (TMPTA) as a cross‐linker and fully charac-
terized. Pd NPs embedded on the magnetic polymer were successfully applied
in Suzuki–Miyaura and Mizoroki–Heck coupling reactions under low palla-
dium loading conditions, and provided the corresponding products with excel-
Faculty of Chemistry, Razi University,
Kermanshah, Iran, 67149‐67346
2
Department of Analytical Chemistry,
Faculty of Chemistry, Razi University,
Kermanshah, Iran, 67149‐67346
3
Nanoscience and Nanotechnology
Research Center (NNRC), Razi University,
Kermanshah, Iran, 67149‐67346
Correspondence
−
1
Kiumars Bahrami, Department of Organic
Chemistry, Faculty of Chemistry, Razi
University. Kermanshah, Iran, 67149‐
lent yields (up to 98%) and high catalytic activities (TOF up to 257 hr ). Also,
the catalyst can be easily separated and reused for at least consecutive five
times with a small drop in catalytic activity.
67346.
Email: kbahrami2@hotmail.com;
k.bahrami@razi.ac.ir
KEYWORDS
Mizoroki–Heck reactions, palladium nanocatalyst, polymer‐stabilized nanoparticles, Suzuki–Miyaura
reactions, terpyridine ligand
1
| INTRODUCTION
reactions have been widely applied in the synthesis of
many drugs, natural products and starting materials via
both intermolecular and intramolecular reactions.
[3]
The C‐C bond‐forming reactions have played a remarkable
role in organic synthesis, since its origins in 1845 by
During the last few decades, major advances in homo-
[1]
Kolbe. The progress in C‐C cross‐coupling came from
the use of reactive homogeneous and heterogeneous palla-
dium catalysts for the reaction of aryl halides or vinyl
halides with organometallic compounds (Suzuki, Corriu–
Kumada, Hiyama, Negishi and Stille reactions), or with
alkenes (Heck reaction), or with alkynes (Sonogashira
geneous palladium‐catalyzed C‐C coupling reactions have
[4]
been described by a number of research groups. Con-
sidering the extensive use of palladium in coupling reac-
tions, and the high cost and toxicity of palladium on the
other hand, there is a growing interest in applying hetero-
geneous and recoverable palladium catalysts, therefore
the heterogenization of palladium catalysts is extremely
important from both environmental and economic points
[2]
reaction). Nowadays, Suzuki–Miyaura and Mizoroki–
Heck reactions have become among the most robust and
efficient synthetic protocols for the formation of C‐C
bonds. These reactions have enabled chemists to join two
organic fragments using relatively mild conditions,
allowing for the creation of delicate intricate organic scaf-
folds. Therefore, the Suzuki–Miyaura and Mizoroki–Heck
[
5–8]
of view.
In recent years, ultrafine noble metal nanoparticles
have been broadly explored for the improvement of the
[
9]
catalysts’ performance. It is confirmed that noble metal
nanoparticles perform superior activity for catalysis due
Appl Organometal Chem. 2019;e5121.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5121

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TARGHAN ET AL.
[
10]
to their extremely small size and high surface areas.
polymerization of Fe O @SiO ‐TMSPM with HPTPy‐
3
4
2
However, high surface energies and large surface area of
noble metal nanoparticles could lead to thermodynami-
cally instability; therefore, protecting capping agents are
often used to stabilize them in a nano region during their
ITC and TMPTA as a cross‐linker was achieved in the
presence of 2,2′‐azobisisobutyronitrile (AIBN) as an initi-
ator in MeOH/CH CN affording the final magnetic poly-
3
mer. The MP‐TPy/Pd was obtained by interaction of
[11]
synthesis.
There are several stabilizing agents, such as
PdCl with MP‐TPy in EtOH as solvent and green reduc-
2
surfactants, polymers, porous organic polymers,
dendrimers, micelles, and various ligands that are able
ing agent (Scheme 2). Moreover, Pd NPs can be success-
fully prepared on MP‐TPy without the addition of
external reducing agents because HPTPy ligands serve
[12,13]
to stabilize metal nanoparticles.
In the case of noble
[16]
metals, the most widely used methods to stabilize the
metal nanoparticles and control their growth are to use
also as a reducing agent due to its nitrogen atoms.
The MP‐TPy/Pd was extensively analyzed through
some characterization techniques, including Fourier
transform‐infrared spectroscopy (FT‐IR), transmission
electron microscopy (TEM), scanning electron micros-
copy (SEM), thermogravimetric analysis (TGA), energy‐
dispersive X‐ray spectroscopy (EDX), X‐ray diffraction
spectroscopy (XRD), X‐ray photoelectron spectroscopy
(XPS), vibrating‐sample magnetometer (VSM), UV–Vis
spectra analysis and inductively coupled plasma (ICP).
The FT‐IR technique can be used to track the synthesis
of MP‐TPy/Pd (Figure 1). In the FT‐IR spectrum of
HPTPy, the following functional groups were identified:
[14]
polymers or ligands.
It is observed that tridentate
nitrogen ligands, including terpyridine‐based ligands,
increase the dispersion and stability of the metal nano-
particles due to the strong interaction of metal–nitrogen
and
metallacycles.
the
formation
of
two
five‐membered
[
15,16]
Currently, polymer supports have found widespread
use as stabilizing agents for noble metal nanoparticles.
“
Use of polymer‐immobilized catalysts provides an essen-
tial technique for the green chemistry process of organic
synthesis. In addition to the aspect of simplicity of cata-
lyst recovery and recycling, it is even possible to apply
the polymeric catalysts to the continuous flow system
which can lead to an economical automation sys-
−
1
2
OH stretching vibrations (3386 cm ), sp C‐H stretching
−
1
vibrations (3036 cm ) and C=N stretching frequency
−
1
(1598 cm ). In the case of HPTPy‐ITC, the band at
[17–19]
−1
tem.”
1740 cm corresponds to C=O stretching of ester groups.
−
1
−1
Due to advantages of polymers as well as facile
removal and recycling of the magnetic catalyst from the
solution system, herein, we report the synthesis and char-
acterization of a new magnetic polymer containing 4′‐(4‐
hydroxyphenyl)‐2,2′:6′,2″‐terpyridine (HPTPy) palladium
complex, namely, MP‐TPy/Pd. The catalytic activity of
the MP‐TPy/Pd was evaluated in the Suzuki–Miyaura
and Mizoroki–Heck coupling reactions (Scheme 1).
The weak absorptions at 2856 cm and 2926 cm are
3
attributed to the sp C‐H stretching vibrations. The bands
−
1
−1
observed at 1592 cm and 3055 cm can be attributed to
the C=N stretching frequency and C‐H aromatic (pyri-
dine rings) stretching vibration, respectively. The C=N
bands of complex TPy‐Pd in MP‐TPy/Pd are shifted to a
−
1
lower frequency (1583 cm ) in the FT‐IR spectrum com-
−
1
pared with that of TPy (1598 cm ). The lowering in fre-
quency of the C=N peak is indicative of the interaction of
[
20]
TPy with Pd.
2
2
| RESULTS AND DISCUSSION
.1 | Catalyst characterization
Figure 2(a) displays the SEM image of MP‐TPy/Pd
showing clearly the synthesized catalyst with irregular
morphology of various particle sizes. The size of the pal-
ladium nanoparticles (Pd NPs) produced on the magnetic
polymer was analyzed by TEM. The TEM images of the
Fe O @SiO ‐TMSPM and MP‐TPy/Pd are shown in
Figure 2(b) and (c), respectively. The TEM images dem-
onstrate the formation of small sized Pd NPs with an
average diameter of 3–4 nm on MP‐TPy/Pd. The TEM
The stages of MP‐TPy/Pd preparation are summarized in
Scheme 2. Initially, HPTPy‐itaconic acid (ITC) was pre-
pared via esterification reaction of ITC and HPTPy. On
the other hand, the Fe O @SiO was modified by using
3
4
2
3
4
2
3‐(trimethoxysilyl) propyl methacrylate (TMSPM). Then,
SCHEME 1 The MP‐TPy/Pd catalyzed
Suzuki–Miyaura and Mizoroki–Heck
coupling reactions

TARGHAN ET AL.
3 of 11
SCHEME 2 Synthetic steps for the
preparation of MP‐TPy/Pd
UV–Vis spectroscopy (Figure 3). In UV–Vis spectroscopy,
the PdCl solution showed a distinct peak at approxi-
2
mately 425 nm, indicating the existence of the Pd (II)
ion. During the formation of Pd NPs on the polymer con-
taining HPTPy ligand, the UV–Vis spectrum showed con-
version of Pd (II) to Pd (0) by the absence of the peak at
[
22]
425 nm.
The formation of Pd (0) nanoparticles was also con-
firmed by the color changes of the magnetic polymer from
brown to dark gray during the synthesis of catalyst in EtOH
within 24 hr (Figure 4). The color changes are due to inter-
[23]
action of terpyridine ligands of the polymer with PdCl2.
The thermal behaviour of the nanocatalyst was investi-
gated by TGA in oxidative (air) environment. The TGA
thermogram for the magnetic polymers is shown in
Figure 5. The polymer displayed excellent thermal stabil-
ities up to 300°C in air. It presented maximum decompo-
sition rate temperature above 300°C, and weight loss of
~84% between 300°C and 450°C is mainly assigned to
the decomposition of the polymer shell and HPTPy
entrapped in polymer.
FIGURE 1 Fourier transform‐infrared (FT‐IR) spectrum of
HPTPy, HPTPy‐ITC and MP‐TPy/Pd
images also determined the magnetic nanoparticles cores,
with sizes significantly larger than Pd NPs due to aggrega-
tion (~30 nm).
Conversion of PdCl to Pd NPs using EtOH as reduc-
2
[
21]
ing agent has been well documented and recognized.
In addition, the nitrogen‐based ligands can also be
regarded as a reducing agent.
Figure 6 presents the XRD pattern of MP‐TPy/Pd. The
diffraction peaks at the Bragg angles of 40.10°, 46.66° and
68.14° correspond to the 111, 200 and 220 facets of
[16]
In this regard, the syn-
thesis of the Pd (0) catalyst was initially monitored by

4
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TARGHAN ET AL.
FIGURE 2 (a) Scanning electron microscopy (SEM) image of MP‐TPy/Pd, (b) transmission electron microscopy (TEM) image of
Fe @SiO ‐TMSPM and (c) TEM image of MP‐TPy/Pd
3
O
4
2
2
FIGURE 3 UV–Vis spectrum of MP‐TPy/Pd and PdCl solution
in EtOH
[24]
elemental palladium in MP‐TPy/Pd.
The XRD pattern
also contains peaks at 2θ values 30.05°, 35.94°, 53.41°,
5
7.38° and 62.98° related to the (220), (311), (422), (511)
[
25]
and (440) that agree with the structure of Fe O NPs.
3
4
The EDX technique can be used for the elemental
analysis of the nanocatalysts, therefore successful synthe-
sis of MP‐TPy/Pd can be inferred from this technique.
EDX spectra show the presence of Fe, Si, C, O, N and
Pd in magnetic polymer‐Pd (Figure 7).
The magnetic properties of Fe O NPs and magnetic
3
4
polymer were determined by VSM. As expected, the mag-
netization of magnetic polymer is smaller than that of
Fe O NPs (Figure 8). Nonetheless, the magnetization of
3
4
magnetic polymer is still large enough for the catalyst
separation from the reaction mixtures.
The MP‐TPY/Pd was also studied by XPS, and high‐
resolution XPS results confirmed the presence of Pd (0)
and Pd (II) on the catalyst (Figure 9). The peaks at
3
35.5 eV (Pd 3d5/2) and 340.5 eV (Pd 3d3/2) are assigned
to Pd (0), whereas peaks at 336.5 eV (Pd 3d5/2) and
42.0 eV (Pd 3d3/2) are assigned for Pd (II) species present
FIGURE 4 The color change of the magnetic polymer, magnetic
polymer (a), preparation of Pd catalyst after 1 min (b), after 2 hr (c),
and after separating with a magnet (d)
3

TARGHAN ET AL.
5 of 11
FIGURE 5 Thermogravimetric analysis (TGA) thermogram of
the magnetic polymer
FIGURE 7 Energy‐dispersive X‐ray spectroscopy (EDX) pattern
of MP‐TPy/Pd
[
26]
on the polymer.
The XPS spectrum shows that Pd (0)
was predominant on MP‐TPy/Pd as the area under the
peak of Pd (II) is relatively small.
or electron‐withdrawing substituents with arylboronic
acids performed to afford corresponding biaryl products
in excellent yields. As expected, the Suzuki reaction of aryl
chlorides required longer reaction times, because aryl chlo-
rides are generally less reactive toward aryl bromides and
iodides.
As an extension to the use of this, we also investigated
the catalytic activities of MP‐TPy/Pd for the Mizoroki
−Heck C‐C coupling reaction. Iodobenzene and styrene
were selected as substrates to establish the best conditions
for the preparation of the corresponding trans‐stilbenes in
the presence of different amounts of the catalysts and var-
ious bases and solvents at 100°C (Table 3). As can be seen
from the table, the best result of 97% yield was obtained
by carrying out the reaction with aryl halide (1 mmol),
2.2 | Catalytic studies
The catalytic activity of the prepared MP‐TPy/Pd was eval-
uated in C‐C formation via Suzuki–Miyaura and
Mizoroki–Heck reactions. Initially, for the optimization
of the Suzuki C‐C coupling reaction, a reaction of
iodobenzene with phenylboronic acid under different reac-
tion conditions, such as different temperatures, solvents
and bases, and in the presence of various amounts of MP‐
TPy/Pd was used as a model reaction (Table 1). The best
result (98% yield) was achieved by using iodobenzene
(1 mmol), phenylboronic acid (1.2 mmol) and K CO3
2
(1.5 mmol) in the presence of the catalyst (0.01 g,
styrene (1.2 mmol) in the presence of 0.015 g
0
1
.19 mol%) at 80°C for 2 hr in a mixture of EtOH/H O (2/
) as solvent (Table 1, entry 4).
Under these optimized conditions, the generality and
(0.285 mol%) of MP‐TPy/Pd and Et N (3 mmol), under
2
3
solvent‐free at conditions at 100°C (Table 3, entry 4).
In order to study the generality of this procedure, the
reaction of other aryl halides with styrene were next stud-
ied. Table 4 contains the results of forming corresponding
trans‐stilbenes in the optimal conditions. As the table
shows, donor‐ and acceptor‐substituted aryl iodides have
been reacted with styrene in mostly excellent yields.
scope of the procedure was assessed in the reaction of com-
mercially available aryl halides with arylboronic acids, and
the results are summarized in Table 2. As shown in Table 2,
MP‐TPy/Pd effectively catalyzed the coupling reaction
between aryl halides possessing either electron‐donating
FIGURE 6 X‐ray diffraction (XRD)
pattern of MP‐TPy/Pd

6
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TARGHAN ET AL.
FIGURE 8 Magnetization curves
obtained by vibrating‐sample
magnetometer (VSM) of Fe
3 4
O
nanoparticles (NPs) and magnetic polymer
TABLE 1 Optimization of conditions in the Suzuki–Miyaura
a
coupling reaction
Cat.
T
Yield
b
Entry (mol%) Base
Solvent
(°C) (%)
1
2
3
4
5
6
7
8
0
K
K
K
K
2
2
2
2
CO
CO
CO
CO
3
3
3
EtOH/H
EtOH/H
EtOH/H
EtOH/H
EtOH/H
EtOH/H
2
2
2
2
2
2
O (2/1) 80
0
55
85
98
86
60
15
20
0.095
0.152
0.19
0.19
0.19
0.19
0.19
O (2/1) 80
O (2/1) 80
O (2/1) 80
O (2/1) 80
O (2/1) 80
80
3
Na
Et
2
CO
3
3
N
K
K
2
CO
3
3
2
H O
2
CO
EtOH/H
2
O (2/1) r.t
a
Reaction conditions: iodobenzene (1 mmol), phenylboronic acid (1.2 mmol),
base (1.5 mmol), solvent (3 ml), under air atmosphere, 2 hr.
b
Isolated yields.
FIGURE
9
The
high‐resolution
X‐ray
photoelectron
next run. Remarkably, recycling experiments confirmed
the chemical stability and reusability of the catalyst, and
the recovered catalyst can be used during four runs
(Figure 10). To confirm this further, leaching of Pd during
the course of the catalytic reactions was examined by ICP
analysis. ICP of the recovered catalyst after five catalytic
cycles indicated that 21% of palladium was leached into
the reaction medium (0.1 g of the manufactured catalyst
spectroscopy (XPS) scan spectrum over Pd 3d peak of MP‐TPy/Pd
However, when iodobenzene was replaced by
bromobenzene, the coupling reactions require longer reac-
tion times. However, the scope of this methodology was
found not to be effective to chlorobenzene (Table 4, entry
7
).
th
The generally accepted mechanisms for Pd‐catalyzed
and the catalyst after the 5 run, containing 0.019 and
Suzuki–Miyaura and Mizoroki–Heck reactions are shown
0.015 mmol of Pd, respectively).
in Scheme 3. Both the mechanisms start with oxidative
To illustrate the efficiency of the present catalyst in
comparison with some Pd‐based nanocatalysts, we com-
pared the results with respect to mol% of Pd, reaction
time and yields of the products (Table 5). Table 5 shows
that this catalyst is superior to some previously reported
nanocatalysts in terms of yields and reaction times.
1
addition of the organohalide (R ‐X) to the Pd (0) to form
[27–29]
a Pd (II) complex.
Finally, the catalyst was easily separated from the reac-
tion mixtures by using an external magnet, and washed
twice with ethanol followed by water, and dried for the

TARGHAN ET AL.
7 of 11
a
TABLE 2 Suzuki−Miyaura coupling reactions of aryl halides with phenylboronic acid
1
2
b
−1
[ref.]
Entry
X
R
R
Time (hr)
Yield (%)
TOF (hr
)
m.p.
[
32]
33]
1
2
3
4
5
6
7
8
9
I
H
H
2
2.5
2
98
95
98
92
95
93
92
92
92
92
257
250
257
242
125
122
121
121
48
65–68
[
I
4‐NO
H
2
2
H
112–115
[
33]
I
4‐Me
3‐NO
H
44–46
[
34]
I
4‐NO
H
2
2.5
4
183–187
[
[
[
[
[
[
32]
32]
32]
33]
32]
33]
Br
Br
Br
Br
Cl
Cl
65–69
85–88
75–78
45–47
63–67
49–51
H
4‐OMe
4‐F
4.5
5
H
4‐Me
H
H
4
H
10
10
1
0
H
4‐Me
48
a
Reaction conditions: iodobenzene (1 mmol), phenylboronic acid (1.2 mmol), catalyst (0.19 mol%), base (1.5 mmol), solvent (3 ml), under air atmosphere.
b
Isolated yields.
a
TABLE 3 Optimization of reaction conditions
carbon‐coated grid Cu mesh 300. The elemental palla-
dium content of the nanocatalyst was determined by
Perkin Elmer Optima 7300D ICP. The XRD pattern was
obtained using STOE STADI‐P diffractometer (Cu K‐
alpha1 radiation wavelength = 1.54060 Å). The chemical
compositions of the catalysts were performed using XPS a
Kratos Axis Ultra DLS spectrometer with an Al Kα as a
source.
b
Entry
Cat. (mol%)
Base
Solvent
Yield (%)
1
2
3
4
5
0
NEt
NEt
NEt
NEt
3
3
3
3
No solvent
No solvent
No solvent
No solvent
DMF
0
46
75
97
90
0.152
0.19
0.285
0.285
3.1 | Preparation of HPTPy
2 3
K CO
a
Reaction conditions: iodobenzene (1 mmol), styrene (1.2 mmol), base
3 mmol), solvent (3 ml), at 100°C, under air atmosphere, 4 hr.
To a mixture of 4‐anisaldehyde (0.12 ml, 1 mmol) and
‐acetylpyridine (0.22 ml, 2 mmol) were added KOH
0.15 g, 2 mmol) and 5 ml EtOH. The reaction mixture
(
2
(
b
Isolated yields.
3
| EXPERIMENTAL
was stirred at room temperature for 2 min, ammonium
hydroxide (2.9 ml, 2.5 mmol) was added and then stir-
ring was continued for 8 hr. The resulting product was
filtered and recrystallized from ethanol to produce
4′‐(4‐methoxyphenyl)‐2,2′:6′,2″‐terpyridine as white
The materials were purchased from Merck and Fluka,
and were used without any additional purification. All
reactions were monitored by thin‐layer chromatography
[
30]
(TLC). Melting points were determined using a Stuart Sci-
crystals in 85% yield (found: m.p. = 156°C).
Then,
entific SMP2 apparatus. FT‐IR spectra were determined
with a PerkinElmer 683 instrument. H‐NMR and C‐
NMR spectra were recorded with a Bruker (400 MHz)
4′‐(4‐methoxyphenyl)‐ 2,2′:6′,2″‐terpyridine (0.676 g,
2 mmol) was treated with 30% HBr in acetic acid
(4 ml) at reflux conditions for 4 hr. After cooling to
room temperature, the resultant solution was then basi-
fied to a pH‐value of 10 by adding aqueous NaOH (20%)
dropwise, and extracted repeatedly with CH Cl . The
1
13
spectrometer in CDCl and dimethylsulfoxide (DMSO)
3
as solvent. TGA was carried out with a STA PT‐1000
Linseis instrument (Germany) under air atmosphere at
a heating rate of 10°C/min. SEM and EDX measurements
were performed using a TESCAN‐MIRA3 operated at
2
2
pH of the alkaline solution was then lowered with
HCl (20%). The addition of HCl converts the soluble salt
back into the water‐insoluble HPTPy as white crystals.
The precipitated product was then filtered and collected
2
6 kV with the electron gun filament: tungsten. TEM
observations were carried out with a Zeiss‐EM10C
Germany) operating at 100 kV with samples on formvar
[
30]
(
in 60% yield [found: m.p. = 290°C,
IR (KBr): 3385,

8
of 11
TARGHAN ET AL.
a
TABLE 4 Coupling reactions of aryl halides with styrene
b
−1
[ref.]
Entry
X
R
Time (hr)
Yield (%)
TOF (hr
)
m.p.
[
[
35]
35]
1
2
3
4
5
6
7
I
H
4
4.5
4
97
92
85
80
83
53
52
52
–
118–122
150–152
115‐118
114–116
152–154
115–117
–
I
4‐NO
4‐Me
H
2
2
[
36]
35]
35]
36]
I
95
[
[
[
Br
Br
Br
Cl
6
92
4‐NO
4‐Me
H
6.5
6
90
90
24
Trace
a
3
Reaction conditions: aryl halide (1 mmol), styrene (1.2 mmol), catalyst (0.285 mol%), NEt (3 mmol), under solvent‐free conditions, 100°C.
b
Isolated yields.
SCHEME 3 The general mechanisms
for Pd‐catalyzed Suzuki–Miyaura and
Mizoroki–Heck reactions
−
1
1
1
594, 1526, 1460, 1175, 779 and 734 cm ]. H‐NMR
(
250 MHz, DMSO‐d ): δ = 9.03–9.06 (d, J = 7.75 Hz,
6
2H), 8.93 (s, 2H), 8.78 (s, 2H), 8.45–8.50 (t, 2H), 7.91
(
s, 4H), 6.93–6.97 (d, J = 7.75 Hz, 2H), 4.47 (br. s,
13
OH). C‐NMR (250 MHz, DMSO‐d ): δ = 160.21,
6
1
1
3
1
51.23, 150.35, 146.08, 143.50, 132.12, 129.33, 128.40,
27.00, 124.17, 120.01, 116.45. MS: 327, 326, 325 (M ),
24, 308, 297, 296, 248, 247, 221, 220, 219, 218, 190,
63, 78, 51.
+
3.2 | Preparation of HPTPy‐ITC
A mixture of ITC (0.065 g, 0.5 mmol) and HPTPy (0.325 g,
mmol) in DMSO (4 ml) was stirred at 100°C for 48 hr.
1
After this time, EtOH (10 ml) and H O (5 ml) were added
2
FIGURE 10 Recycling of the catalyst for the reaction of
iodobenzene and phenylboronic acid
into the reaction mixture, and the precipitate collected by
filtration and dried at 70°C.

TARGHAN ET AL.
9 of 11
TABLE 5 Catalytic performances of some Pd‐based nanocatalysts
for Suzuki coupling of iodobenzene and phenylboronic acid
Finally, after air cooling, the mixture was collected by an
external magnet and the solid obtained was dried at 50°C.
Pd
Yield
Entry Conditions
(mol%) Time (%)
3
.6 | Preparation of magnetic polymer
1
2
3
GO/NHC‐Pd, Na
3
PO
4
·12H
2
O,
1
6 hr
1 hr
91.6
99
containing HPTPy (MP‐TPy)
[
37]
H
2
O, 100°C
Pd–HoMOF, KOH, DMF,
0.4
0.27
Fe O @SiO @TMSPM (0.1 g) was dispersed in 15 ml
MeOH/CH CN (40:60), and HPTPy‐ITC (0.033 g) was
added. The mixture was stirred at room temperature for
1 hr. To this mixture was added 0.9 ml of TMPTA and
3
4
2
[
38]
1
00°C
(Pd (II)–NHCs)
CO , DMF/H
2
3
n
@nSiO
O (2:1),
2
,
6 min 97
K
2
3
39]
[
6
0°C
0.06 g of AIBN as an initiator, and the final volume was
4
5
6
7
8
Pd NPs on polymer, K
2
CO
3
,
0.08
5 hr
3 hr
83
96
adjusted with MeOH/CH CN (40:60) to 35 ml. The mix-
3
[23]
H
2
O, 25–100°C
ture was sonicated for 3 min and then purged with nitro-
gen. The resulting mixture was refluxed at 60–70°C for
24 hr. The products were collected by using the external
magnetic field, washed with ethanol, deionized water
and acetone, then dried in vacuum at 50°C.
Pd (II)‐NiFe , K CO3, EtOH/ 0.5
2
[
O
4
40]
2
H
2
O, 80°C
GO‐CPTMS@Pd‐TKHPP,
CO , EtOH/H O, 80°C
Pd–IPG, NaOH, EtOH/H O,
10
15 min 99
[41]
K
2
3
2
2
0.1
1 hr
2 hr
99
98
[42]
6
0°C
3.7 | Preparation of MP‐TPy/Pd
MP‐TPy/Pd
0.19
MP‐TPy/Pd was prepared in a typical procedure as fol-
3
.3 | Preparation of Fe O NPs
3 4
lows. The magnetic polymer (0.1 g) and PdCl (0.003 g,
2
0
.028 mmol) were refluxed in EtOH (5 ml) for 24 hr.
Fe O NPs were prepared according to a reported litera-
3
4
The final catalyst was separated with a magnet, washed
with EtOH and dried at 50°C. ICP showed 0.019 mmol
of palladium is loaded on the 0.1 g MP‐TPy/Pd
[31]
ture procedure.
1 g) were dissolved in deionized water (100 ml) under
inert gas of N atmosphere. To this solution was added
FeCl ·6H O (2.7 g) and FeCl ·4H O
3 2 2 2
(
2
(
2.01 wt%).
1
1 ml of 25% NH OH while stirring vigorously under
4
N . Then the mixture was heated to 60°C and stirred for
2
1
hr under N atmosphere. After cooling to room temper-
3.8 | General procedure for Suzuki–
Miyaura cross‐coupling reactions
2
ature, the resultant nanoparticles were gathered using an
external magnet and washed several times with distilled
water. After drying, a black powder was obtained.
ArX (1 mmol), ArB (OH)2 (1.2 mmol) and K CO
2
3
(
1.5 mmol) were added into a flask containing MP‐TPy/
Pd (0.01 g, 0.19 mol%) and EtOH/H O (2/1). The mixture
2
3
.4 | Preparation of Fe O @SiO
3 4 2
was then stirred in an 80°C oil bath for an appropriate reac-
tion time. The progress of the reaction was monitored by
TLC. After completion of the reaction, ethyl acetate
The prepared Fe O NPs (0.5 g) were dispersed in 20 ml
3
4
of deionized water by ultrasonic treatment for 10 min.
Then, to this mixture was added 80 ml of EtOH, 0.5 ml
of tetraethyl orthosilicate (TEOS) and 1.5 ml of 25%
(
10 ml) was added into the reaction mixture, the catalyst
was separated by using an external magnet, and the
organic solvent was evaporated to obtain a biaryl product.
NH OH at 30°C under mechanical agitation. After
4
1
Biphenyl (Table 2, entry 1): H‐NMR (400 MHz, CDCl ):
3
2
4 hr, the final product was collected by an external mag-
δ =7.53 (4H, d, J = 8 Hz), 7.37 (4H, t, J = 8 Hz), 7.28 (2H, t,
net, washed with EtOH and deionized water, and dried at
13
J = 8 Hz). C‐NMR (100 MHz, CDCl ): δ = 141.27, 128.80,
3
5
0°C to afford Fe O @SiO .
3 4 2
1
37.0, 127.29, 127.21.
1
4
‐Methylbiphenyl (Table 2, entry 3): H‐NMR
3
.5 | Preparation of Fe O @SiO @TMSPM
(400 MHz, CDCl
3
): δ = 7.17–7.52 (9H), 2.32 (3H, s).
3
4
2
1
3,4′‐Dinitrobiphenyl (Table 2, entry 4): H‐NMR
The prepared Fe O @SiO (0.1 g) was dispersed in 10 ml of
(400 MHz, CDCl ): δ =8.55 (1H, s), 8.40 (2H, d,
3
4
2
3
dry toluene by ultrasonic treatment for 15 min. Then,
TMSPM (0.3 ml) was added to the mixture. At reflux tem-
perature, the resulting mixture was stirred for 24 hr.
J = 8 Hz), 8.42 (2H, d, J = 8 Hz), 8.37 (1H, d,
J = 8 Hz), 8.02 (1H, d, J = 8 Hz) 7.86 (2H, d, J = 8 Hz),
7.76 (1H, t, J = 8 Hz). C‐NMR (100 MHz, CDCl3):
13

10 of 11
TARGHAN ET AL.
δ = 148.83, 148.02, 144.91, 140.48, 133.26, 130.32, 128.16,
24.51, 123.61, 122.35.
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3
.9 | General procedure for Mizoroki
Heck cross‐ coupling reactions
[
[
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Et N (3 mmol) and MP‐TPy/Pd (0.015 g, 0.28 mol%) was
3
[
9] M. Yuan, R. Yang, S. Wei, X. Hu, D. Xu, J. Yang, Z. Dong,
stirred at 100°C (oil bath temperature) under solvent‐free
conditions. After completion of the reaction, which was
monitored by TLC, ethylacetate (10 ml) was added to
the mixture reaction. The catalyst was separated by using
an external magnet. Water (3 × 15 ml) was added to the
ethylacetate phase and decanted. After evaporation of
the solvent, the resulting crude products were purified
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CDCl ): δ = 7.60 (4H, d, J = 8 Hz), 7.44 (4H, t, J = 8 Hz),
3
[
[
[
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.31–7.37 (2H, m), 7.20 (2H, s). C‐NMR (100 MHz,
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3
4
| CONCLUSIONS
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[20] K. Bahrami, M. M. Khodaei, F. S. Meibodi, Appl. Organomet.
In summary, magnetic polymer‐supported Pd NPs have
been prepared and fully characterized. As expected, MP‐
TPy/Pd exhibited excellent activity in Suzuki–Miyaura
and Mizoroki–Heck cross‐coupling reactions under low
palladium loading conditions, and provided the corre-
sponding products with excellent yields (up to 98%) and
high catalytic activities (TOF up to 257 hr ). It is note-
worthy that palladium ions are reduced to Pd NPs and
stabled in the presence of ethanol as a green reducing
agent and due to interaction with terpyridine‐based
ligand. Ultimately, we believe that this work offers sev-
eral advantages in preparative procedures, including sim-
plicity of product work‐up and separation of the catalyst.
In addition, MP‐TPy/Pd, magnetically recoverable
nanocatalyst, was reused for a consecutive five times with
a small drop in catalytic activity, considering the high
cost of palladium, reuse of the catalysts could lead to eco-
nomical automation system.
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