A new strategy to design a graphene oxide supported palladium complex as a new heterogeneous nanocatalyst and application in carbon–carbon and carbon-heteroatom cross-coupling reactions

Article abstract of DOI:10.1002/aoc.4842

The palladium nanoparticles were successfully stabilized with an average diameter of 6–7?nm through the coordination of palladium and terpyridine-based ligands grafted on graphene oxide surface. The graphene oxide supported palladium nanoparticles were thoroughly characterized and applied as an efficient heterogeneous catalyst in carbon–carbon (Suzuki-Miyaura, Mizoroki-Heck coupling reactions) and carbon–heteroatom (C-N and C-O) bond-forming reactions. The catalyst was simply recycled from the reaction mixture and was reused consecutive four times with small drop in catalytic activity.

Full text of DOI:10.1002/aoc.4842

Received: 28 October 2018
DOI: 10.1002/aoc.4842
Revised: 9 January 2019
Accepted: 11 January 2019
F U L L P A P E R
A new strategy to design a graphene oxide supported
palladium complex as a new heterogeneous nanocatalyst
and application in carbon–carbon and carbon‐heteroatom
cross‐coupling reactions
Kiumars Bahrami1,2
| Homa Targhan1
1 Department of Organic Chemistry,
The palladium nanoparticles were successfully stabilized with an average
diameter of 6–7 nm through the coordination of palladium and terpyridine‐
based ligands grafted on graphene oxide surface. The graphene oxide supported
palladium nanoparticles were thoroughly characterized and applied as an
efficient heterogeneous catalyst in carbon–carbon (Suzuki‐Miyaura, Mizoroki‐
Heck coupling reactions) and carbon–heteroatom (C‐N and C‐O) bond‐
forming reactions. The catalyst was simply recycled from the reaction mixture
and was reused consecutive four times with small drop in catalytic activity.
Faculty of Chemistry, Razi University,
Kermanshah 67149‐67346, Iran
2 Nanoscience and Nanotechnology
Research Center (NNRC), Razi University,
Kermanshah 67149‐67346, Iran
Correspondence
Kiumars Bahrami, Nanoscience and
Nanotechnology Research Center
(NNRC), Razi University, Kermanshah,
67149‐67346, Iran.
Email: kbahrami2@hotmail.com
KEYWORDS
cross‐coupling, graphene oxide, heterogeneous nanocatalyst, palladium‐catalyzed, terpyridine‐based
Funding information
Razi University Research Council
ligands
1 | INTRODUCTION
Palladium catalysts are well known for the carbon–
carbon and carbon–heteroatom bonds formation in reac-
Cross‐coupling reactions have found widespread use in the
creation of carbon–carbon (Suzuki–Miyaura, Kumada–
Corriu, Stille, Mizoroki–Heck, Sonogashira, Hiyama and
Negishi reactions) and carbon–heteroatom (C‐O, C‐N
and C‐S) bonds[1] and always get prior importance in the
field of synthetic organic chemistry as well as in medicinal
chemistry.[2,3] It should be noted that progress on cross‐
coupling reactions plays an important role in the develop-
ment of pharmaceutical industry. These reactions provide
new roads for design and preparation of drug sub-
stances.[4] For example, the cross‐coupling reactions are
considered as key steps in production of Losartan®,[5]
Zyprexa,[6] Singulair,[7] (+)‐Dynemicin,[8] Morphine[9]
and Paclitaxel.[10] The importance of scientific advances
associated with cross‐coupling was demonstrated by
awarding Richard F. Heck, Ei‐ichi Negishi and Akira
Suzuki the Nobel Prize in chemistry in 2010 for the devel-
opment of palladium‐catalyzed cross coupling.[2,11]
tions of aryl halides via cross‐coupling reactions on both
academic and industrial scales.[12] During the last few
decades, major advances in homogeneous palladium‐
catalyzed coupling reactions have been described by a
number of research groups.[2] Considering the extensive
use of palladium in cross‐coupling reactions and high cost
and toxicity of palladium on the other hand, there is a
growing interest in applying heterogeneous and recover-
able palladium catalysts, therefore the heterogenization
of palladium catalysts is extremely important from both
environmentally and economic points of view.[13–19]
Recent developments in nanotechnology has signifi-
cantly improved catalyst performance.[20] Nano‐sized cat-
alysts have high surface area thereby increase the contact
between reactants and catalyst and speed up the catalytic
process. In other hand, due to insolubility in reaction sol-
vents, nanocatalysts are easily separated from the reaction
mixture and are reusable systems. In addition, researchers
Appl Organometal Chem. 2019;e4842.
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© 2019 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4842

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BAHRAMI AND TARGHAN
have shown that activity and selectivity of nanocatalysts
can be controlled by tailoring chemical and physical prop-
erties of nanocatalysts including particle size and surface
composition, shape and morphology via techniques for
preparing nanocatalysts.[21] It is well known that particle
size of metals strongly impacted their catalytic properties,
a decrease in particle size increases the surface area the
number of edge and corner atoms and these lead to the
improvement of the catalytic properties of metals.
Therefore, metal particles must be generated as small as
possible. For this purpose and stabilization of metal nano-
particles, different types of stabilizers, such as surfactants,
polymers, and dendrimers, micelles and various ligands as
well as anchoring of metal particles on supports are pre-
sented.[22] In the last decade, metal nanoparticles sup-
ported on high‐surface‐area solid carriers such as porous
silica, alumina, zeolites, Fe3O4 and other oxides, mesopo-
rous materials, carbon nanofibers, multi‐walled carbon
nanotubes, hollow carbon nanospheres, graphene oxide
etc. have been prepared and employed as catalysts.[23,24]
Graphene oxide (GO) is a two‐dimensional carbon
sheet decorated with oxygenated functional groups, such
as hydroxyl (OH), carbonyl (C=O) and alkoxy (C–O–C)
groups, which is prepared from oxidation of graph-
ite.[25,26] GO is commonly produced by the oxidative
treatment of graphite with KMnO4 and NaNO3 in con-
centrated H2SO4 via Hummers method as a reliable
method.[27] The peculiar properties of graphene oxide
such as easy dispersibility in many solvents and particu-
larly in water,[28] low cost,[29] electronic, optical, thermal,
mechanical, and electrochemical properties, as well as
chemical reactivity and high surface area[30] make it as
a good candidate for application in electronic and energy
storage devices, biosensors, coating agents, water purifi-
cation machine and as a support material for the synthe-
sis of heterogeneous catalysts.[26,31]
has also been applied as nanocatalyst for the C − C,
C − N and C‐O bond formations via cross‐coupling reac-
tions of aryl halides.
The terpyridines were first discovered by Morgan and
Burstall in 1932, from the reaction of pyridine with
FeCl3.[32] The terpyridine derivatives consist of three
pyridine rings and because of efficient and stable
chelating ability to transition metals, are used as
multidentate polypyridine ligands to prepare coordination
complexes.[33–35]
The GO‐supported palladium TPy complex [denoted
as (1,4‐C6H4)(GO‐CPTMS@HPTPy‐Pd‐TPy)2] was facilely
prepared through a simple process and applied as an
effective and reusable catalyst to create carbon–carbon
bond via Suzuki‐Miyaura, Mizoroki‐Heck and carbon–
heteroatom (C‐O, C‐N) bonds (Scheme 1).
2 | RESULTS AND DISCUSSION
2.1 | Catalyst characterization
The stages of (1,4‐C6H4)(GO‐CPTMS@HPTPy‐Pd‐TPy)2
preparation are summarized in Scheme 2. Initially, the
graphene oxide is typically prepared employing modified
Hummers method[27,36] and modified by using CPTMS,[26]
then HPTPy ligand (see Supporting Information), prepared
according to the literature reports,[35,37] connected to GO‐
CPTMS. Subsequent, the process for preparing the catalyst
is complete with added TPy‐C6H4‐TPy, synthesized accord-
ing to Vaduvescu and Potvin report,[38] and PdCl2.
The prepared catalyst was extensively analyzed
through some characterization techniques including Fou-
rier transform infrared spectroscopy (FT‐IR), transmis-
sion electron microscopy (TEM), scanning electron
microscopy (SEM), thermogravimetric analysis (TGA),
energy‐dispersive X‐ray spectroscopy (EDX), X‐ray dif-
fraction spectroscopy (XRD), UV–Vis spectra analysis
and inductively coupled plasma (ICP).
Inspiring from recent developments in the field of
nanocatalyst, herein, we report preparation and charac-
terization of GO‐supported palladium complex with two
types of 2,2′: 6′,2″‐terpyridine ligands (4′‐(4‐hydroxy-
phenyl)‐2,2′:6′,2″‐terpyridine (HPTPy) and 1,4‐Bis(2,2′:
6′,2″‐terpyridin‐4′‐yl)benzene (TPy‐C6H4‐TPy)) which
Conversion of PdCl2 to Pd NPs using EtOH as reduc-
ing agent has been well documented and recog-
nized.[39,40] In this regard, the synthesis of the Pd(0)
SCHEME 1 GO supported Pd
nanoparticles catalyzed C‐C, C‐N and C‐O
bonds‐forming reactions

BAHRAMI AND TARGHAN
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SCHEME 2 Synthesis steps of the catalyst
FIGURE 1 UV–visible spectra of PdCl2
solution and Pd NPs
FIGURE 2 Representative UV–Vis
spectra of soluble PdCl2 in EtOH (A), PdCl2
and GO‐CPTMS in EtOH (B) and mixtures
of PdCl2 and GO‐CPTMS@TPy in EtOH in
the absence and presence of the TPy‐C6H4‐
TPy (C and D respectively) monitored at
24 hr. The solution was refluxed at 80 °C
and spectra are recorded at 30 °C

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BAHRAMI AND TARGHAN
FIGURE 3 (a) and (b) SEM images, (c) and (d) TEM images of (1,4‐C6H4)(GO‐CPTMS@HPTPy‐Pd‐TPy)2, (e) SEM image (f) TEM image
of GO

BAHRAMI AND TARGHAN
5 of 13
catalyst was initially monitored by UV–Visible spectros-
copy (Figure 1). In UV–visible spectroscopy, the PdCl2
solution showed a distinct peak approximately at
425 nm indicating the existence of Pd (II) ion. During
the formation of Pd NPs on the GO‐CPTMS@-
terpyridine‐based ligands, the UV–Vis spectrum showed
conversion of Pd (II) to Pd(0) by the absence of the peak
at 425 nm. The formation of Pd(0) nanoparticles was also
confirmed by the color change of palladium solution from
yellowish into dark brown during the catalyst synthesis
within 24 hr (Figure 1).[13,41,42]
As mentiomed in leterature, in the case of noble
metals, one of the most widely used methods to stabilize
the nanoparticles and control their growth is to use
ligands[43] and it is observed that tridentate nitrogen
ligands, including terpyridine‐based ligands, increase the
dispersion and stability of the metal nanoparticles due
to the strong interaction metal‐nitrogen and the forma-
tion of two five‐membered metallacycles.[44,45]
Furthermore, the reduction of Pd (II) ions and the sta-
bilization of Pd NPs on GO‐CPTMS and GO‐CPTMS@-
TPy in the presence and absence of the TPy‐Ph‐TPy was
monitored by the UV–Vis spectra analysis in the presence
of EtOH as green solvent and reducing agent. Figure 2
shows UV–Vis spectra of soluble PdCl2 in EtOH (A),
PdCl2 and GO‐CPTMS in EtOH (B) and mixtures of PdCl2
and GO‐CPTMS@TPy in EtOH in the absence and pres-
ence of the TPy‐Ph‐TPy (C and D respectively), in PdCl2
and GO‐CPTMS@TPy sample, the intensity at 240 nm is
decreased more than the case of GO‐CPTMS after 24 hr
which indicates the more stabilization of Pd NPs on
GO‐CPTMS@TPy (C). The peak of 245 nm began to
disappear in the presence of the TPy‐C6H4‐TPy, which
showed significant increase in stabilization of Pd NPs
on GO‐CPTMS@TPy was observed after 24 hr (D). As
was expected, TPy and TPy‐Ph‐TPy ligands can act as
effective stabilizers for Pd species.
Figures 3a and 3b display SEM images (1,4‐C6H4)(GO‐
CPTMS@HPTPy‐Pd‐TPy)2 with different magnifications.
TEM images of the prepared nanocatalyst are shown in
Figures 3c and 3d. It can be seen that uniform and small
sized Pd nanoparticles, with 6–7 nm average diameters,
have been dispersed on surface of GO layers. Figures 3e
and 3f also show SEM and TEM images of Go, respectively.
EDX technique can be used for the elemental analysis
of the nanocatalyst, therefore successful functionalization
of the GO can be inferred from this technique. EDS spec-
trum shows the presence of C, Si, O, N and Pd in the
structure of (1,4‐C6H4)(GO‐CPTMS@HPTPy‐Pd‐TPy)2
(Figure 4).
Figure 5 presents XRD patterns of the synthesized
graphene oxide and (1,4‐C6H4)(GO‐CPTMS@HPTPy‐Pd‐
TPy)2. The diffraction peaks at the Bragg angles of 41.1°,
46.7°, and 68.2° correspond to the 111, 200, and 220 facets
of elemental palladium.[46,47]
FT‐IR technique can also be used to track the synthesis
and modification of GO and connection of HPTPy on the
surface of modified graphene oxide (Figure 6). In the FT‐
IR spectrum of GO, following functional groups were iden-
tified: OH stretching vibrations (3424 cm−1), C=O
stretching vibration (1729 cm−1), C=C from unoxidized
sp2 CC bonds (1414, 1627 cm−1), and CO vibrations
(1225 cm−1). In the case of GO‐CPTMS, the sharp band
at 1037 cm−1 corresponds to Si–O–Si antisymmetric
FIGURE 4 EDX pattern of (1,4‐C6H4)
(GO‐CPTMS@HPTPy‐Pd‐TPy)2

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BAHRAMI AND TARGHAN
FIGURE 5 (a) XRD patterns of (1,4‐C6H4)(GO‐CPTMS@HPTPy‐Pd‐TPy)2 and (b) GO
which is ascribed to the thermal decomposition of
organic compounds from nanocatalyst surface
(Figure 7).
2.2 | Catalytic studies
The catalytic activity of the prepared GO supported
nanocatalyst was evaluated in the carbon–carbon
(Suzuki–Miyaura, Mizoroki–Heck reactions) and
carbon–heteroatom (C‐O, C‐N) bonds formation via cross
coupling reactions. Initially, for the optimization of the
Suzuki C‐C coupling reaction, a reaction of iodobenzene
with phenylboronic acid under different reaction condi-
tions such as different temperatures, solvents, bases and
in the presence of various amounts of catalyst was exam-
ined as a model reaction. The best result (95% yield) was
obtained by using iodobenzene (1.2 mmol), phenylboronic
acid (1 mmol) and K2CO3 (1.5 mmol) in the presence of
the catalyst (0.01 gr, 1.38 mol%) in a mixture of
EtOH/H2O (2/1) at 80 °C (Table 1, entry 3). To show the
necessity of terpyridine ligand in this catalyst, we run a
control experiment with GO‐CPTMS‐Pd as a catalyst with-
out the terpyridine attachment (Table 1, entry 4). As can
be seen, the reaction produces lower yield of product.
Under these optimized conditions, the generality and
scope of the procedure was assessed in the reaction of
substituted aryl halides with arylboronic acids and the
results are summarized in Table 2. As shown in Table 2,
the coupling reaction between aryl halides containing
electron‐donating groups (Table 2, entry 8) as well as
electron withdrawing groups (Table 2, entries 2, 4) with
arylboronic acids performed to afford corresponding
biaryl products in good to excellent yields. As expected,
the Suzuki reaction of aryl chlorides required longer reac-
tion times, because aryl chlorides are generally less reac-
tive toward aryl bromides and iodides.
FIGURE
CPTMS@TPy
6
FT‐IR spectra of GO, GO‐CPTMS and GO‐
stretching. The peak appearing at 799 cm−1 is due to
thesymmetric vibration of Si–O–Si. The weak absorption
in 2975 cm−1 is attributed to the sp3 C‐H stretching vibra-
tions. When the HPTPy was connected on the GO‐CPTMS
surface, the band observed at 1598 cm−1 can be attributed
to the C=N stretching frequency. The weak sp2 C‐H
stretching vibration of aromatic rings is appeared in
3052 cm−1
.
The thermal behaviour of the nanocatalyst was inves-
tigated by thermogravimetric analysis (TGA). According
to literature graphene oxide tends to lose up to ~50% of
its weight between 150 and 350 °C. This is an irreversible
effect caused by the detachment of labile oxygen‐
containing functional groups located on GO support.[48]
The weight loss in this temperature range for our
nanocatalyst is 9.84%, which indicates that the most oxy-
gen carrying functionalities from GO surface were uti-
lized in Si‐O bond formation between GO and CPTMS.
A weight loss of 10.14% is observed from 350 to 500 °C,

BAHRAMI AND TARGHAN
7 of 13
FIGURE 7 TGA curve of (1,4‐C6H4)(GO‐CPTMS@HPTPy‐Pd‐TPy)2
TABLE 1 Optimization of conditions in the Suzuki‐Miyaura coupling reactiona
Entry
Catalyst
Base
Solvent
T (°C)
Yield (%)b
1
2
3
4
5
6
7
8
0.69 mol%
1.10 mol%
1.38 mol%
0.01 grc
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
NEt3
EtOH/H2O (2/1)
EtOH/H2O (2/1)
EtOH/H2O (2/1)
EtOH/H2O (2/1)
DMF
80
80
80
80
80
80
80
r.t.
35
75
95
35
96
20
50
20
1.38 mol%
1.38 mol%
1.38 mol%
1.38 mol%
H2O
EtOH/H2O (2/1)
EtOH/H2O (2/1)
K2CO3
aReaction conditions: Iodobenzene (1.2 mmol), phenylboronic acid (1 mmol), base (1.5 mmol), solvent (3 mL), under air atmosphere, 3 hr.
bIsolated yields.
cCatalyst: GO‐CPTMS‐Pd.
In a subsequent step, we investigated the catalytic
activity of (1,4‐C6H4)(GO‐CPTMS@HPTPy‐Pd‐TPy)2 for
the Mizoroki−Heck C‐C coupling reaction. The
bromobenzene (1 mmol) and styrene (1.2 mmol) were
selected as substrates to establish the best condition for
the preparation of the corresponding trans‐stilbenes in
the presence of different amount of the catalyst and vari-
ous bases and solvents at 100 °C. Initially, the reaction
was performed in the absence of catalyst and no product
obtained. After careful examinations, the use of 0.01 gr
(1.38 mol%) of the catalyst in the presence of Et3N
(3 mmol) as a base under solvent‐free conditions at
100 °C was found to be the optimal condition for the syn-
thesis of trans‐stilbenes (Table 3, entry 4). In Table 4 are
reported the results for the coupling of styrene with aryl
halides using the Pd nanocatalyst and forming corre-
sponding trans‐stilbenes in the optimal conditions. As
Table 4 shows, donor‐ and acceptor substituted aryl

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BAHRAMI AND TARGHAN
TABLE 2 Suzuki−Miyaura coupling reactions of aryl halides with phenylboronicacida
Entry
X
R1
R2
Time (h)
Yield (%)b
TOF (h−1
)
MpRef.
1
2
3
4
5
6
7
8
9
I
H
H
3
3
3
3
3
3
3
3
5
95
92
98
95
92
93
95
95
90
23.19
22.22
23.67
23.19
22.22
22.46
23.19
23.19
13.04
66[49]
I
4‐NO2
H
H
114[50]
I
4‐CH3
3‐NO2
H
42–44[50]
180–184[51]
65–67[49]
85–88[50]
74–76[52]
45[50]
I
4‐NO2
H
Br
Br
Br
Br
Cl
H
4‐OCH3
4‐F
H
4‐CH3
H
H
H
65[49]
aReaction conditions: Iodobenzene (1.2 mmol), phenylboronic acid (1 mmol), catalyst (1.38 mol%), base (1.5 mmol), solvent (3 mL), under air atmosphere.
bIsolated yields.
TABLE 3 Optimization of reaction conditionsa
As an extension to use of the GO‐supported palla-
dium complex, we also employed this nanocatalyst for
arylation of amines and phenols with aryl halides. The
reaction of iodobenzene (1.2 mmol) with aniline
(1 mmol) was first studied as standard substrate with
the prepared nanocatalyst (Table 5). We found that the
reaction occurred to afford diphenylamine in 92% yield
when it was stirred for 24 hr at 100 °C in the presence
of 0.01 gr (1.38 mol%) (1,4‐C6H4)(GO‐CPTMS@HPTPy‐
Pd‐TPy)2 and 3 mmol of K2CO3 in DMF under air
(Table 5 entry 2).
Entry Catalyst (mol%) Base
Solvent
Yield(%)b
1
2
3
4
5
No catalyst
0.69
NEt3
NEt3
NEt3
NEt3
No solvent
0
No solvent 35
No solvent 70
No solvent 92
1.10
1.38
1.38
K2CO3 DMF
92
aReaction conditions: bromobenzene (1 mmol), styrene (1.2 mmol), base
(3 mmol), solvent (3 mL), at 100 °C, under air atmosphere, 4 hr.
bIsolated yields.
In order to study the generality of this procedure, the
reaction of other amines and substituted phenols were
next studied. As shown in Table 6, electron‐rich, −neutral,
and ‐poor substituted anilines are all converted to second-
ary aromatic amines by reaction with iodobenzene in the
yield ranging from 85 to 92%. Secondary amines, e.g.,
diphenylamine (yield 50%), do not exhibit as high yields
as primary amines. When iodobenzene was replaced by
bromides and iodides have been reacted with styrene in
mostly excellent yields, however, aryl bromides require
longer reaction times.
TABLE 4 Coupling reactions of aryl halides with styrenea
Entry
X
R
Time (h)
Yield (%)b
TOF (h−1
)
MpRef.
1
2
3
4
5
I
H
4
4
5
5
5
95
92
92
90
90
17.21
16.67
13.33
13.04
13.04
115–120[53]
148–150[53]
112–116[53]
150–152[53]
116[54]
I
4‐NO2
H
Br
Br
Br
4‐NO2
4‐CH3
aReaction conditions: Aryl halide (1 mmol), styrene (1.2 mmol), catalyst (1.38 mol%), NEt3 (3 mmol), under solvent‐free, 100 °C.
bIsolated yields.

BAHRAMI AND TARGHAN
9 of 13
TABLE 5 Optimization of reaction conditions for arylation of
method has been utilized for the creation of C‐O bond
and provided a number of diaryl ethers in high to excellent
yields. In the case of C‐O bond formation, bromobenzene
is reactive almost as much as iodobenzene. Both hydroxyl
groups of the hydroquinone molecule can conceivably
react with iodobenzene and 1,4‐diphenoxybenzene is syn-
thesized in 92% yield (Table 6, entry 10).
amines and phenolsa
Catalyst
Entry (mol%)
Base
Solvent T (°C) Yield (%)b
Furthermore, the catalyst easily separated from the
reaction mixture by centrifugation and washed two times
with ethanol and followed by water, finally dried for the
next run. Remarkably, the recovered catalyst still
remained highly active and was reused consecutive three
times with small drop in catalytic activity. Reusability
results confirm that no substantial loss of palladium from
the catalyst surface happens during the reactions. To con-
firm this further, leaching of Pd during the course of the
catalytic reactions was examined by ICP analysis. ICP
showed 1 gr of the manufactured catalyst and the catalyst
after four catalytic cycles, containing 1.38 and 1.22 mmol
of Pd, respectively. The results confirmed the chemical
stability and reusability of the (1,4‐C6H4)(GO‐CPTMS@
HPTPy‐Pd‐TPy)2 nanocatalyst.
1
2
3
4
5
6
7
1.10
1.38
1.38
1.38
1.38
1.38
1.38
K2CO3 DMF
K2CO3 DMF
K2CO3 Toluene
K2CO3 EtOH
K2CO3 DMF
K2CO3 DMF
100
100
100
100
r.t
80
92
65
60
trace
50
60
NEt3
DMF
100
55
aReaction conditions: Iodobenzene (1.2 mmol), aniline (1 mmol), under air
atmosphere, 24 hr.
bIsolated yields.
bromobenzene, the coupling reaction was not effective.
Indeed, the reaction of bromobenzene with aniline
occurred in 15% yield (Table 6, entry 6), significantly lower
than the reaction of iodobenzene with aniline. This
The efficiency of the synthesized catalyst in this work
is compared to some graphene oxide supported Pd
TABLE 6 Arylation of amines and phenols
Entry
X
Y
R1
R3
Yield (%)b
TOF (h−1
)
MpRef.
53[55]
1
I
NH
NH
NH
NH
N‐Ph
NH
O
H
H
92
85
90
85
50
15
96
93
90
92c
90
92
92
88
25
2.78
2.57
2.72
2.57
1.51
0.45
2.90
2.81
2.72
2.78
2.72
2.78
2.78
2.66
0.75
2
I
4‐NO2
H
H
130[56]
129[57]
85–90[57]
124[58]
‐
Oil[59]
56–58[59]
145[60]
75–77[61]
76[62]
3
I
4‐NO2
4‐CH3
H
4
I
H
5
I
H
6
Br
I
H
H
7
H
H
8
I
O
4‐NO2
4‐NO2
H
H
9
I
O
4‐NO2
4‐OH
4‐Cl
4‐OCH3
3,5‐diMe
H
10
11
12
13
14
15
I
O
I
O
4‐NO2
4‐NO2
4‐NO2
H
I
O
108[63]
74–76[64]
Oil[59]
‐
I
O
Br
Cl
O
O
H
H
aReaction conditions: Iodobenzene (1.2 mmol), amines or substituted phenols (1 mmol), catalyst (1.38 mol%), K2CO3 (3 mmol), DMF, 100 °C, under air atmo-
sphere, 24 hr.
bIsolated yields.
c2.4 mmol of iodobenzene was used.

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BAHRAMI AND TARGHAN
nanocatalysts in Suzuki and Heck coupling reactions.
Table 7 shows that this catalyst is superior to some
previously reported nanocatalysts in terms of yields and
reaction times.
3.2 | Synthesis of GO
GO was synthesized employing modified Hummer's
method.[27,36] Briefly, concentrated H2SO4 (15 mL) was
added to a mixture of graphite (0.3 g) and NaNO3 (0.3 g),
and the mixture was cooled to 0 °C in an ice‐salt bath.
Under stirring, KMnO4 (1.5 g) was added slowly to the sus-
pension over 2 hr at 0 to 10 °C with ice‐salt bath cooling.
The mixture was warmed to 35 °C and stirred for 30 min,
and the resulting solution was diluted by slowly adding
30 mL of water under stirring. Then the reaction was
stirred under reflux for 15 min at 98 °C. After cooling to
room temperature, the resulting mixture was treated with
30% H2O2 solution (7 mL). The mixture was washed with
HCl and H2O respectively, followed by centrifugation
and drying, graphene oxide was thus obtained (0.38 g).
3 | EXPERIMENTAL
3.1 | Material and physical measurements
The materials were purchased from Merck and Fluka
and were used without any additional purification. All
reactions were monitored by TLC. Melting points were
determined using a Stuart Scientific SMP2 apparatus.
FT‐IR spectra were determined with a PerkinElmer
683 instrument. 1H NMR and 13C NMR spectra were
recorded with a Bruker (250 and 400 MHz) spectrometer
in CDCl3 as solvent. TGA was carried out with a STA
PT‐ 1000 Linseis instrument (Germany) under air atmo-
sphere at a heating rate of 10 °C min−1. SEM and
energy‐dispersive X‐ray (EDX) measurements were per-
formed using a TESCAN‐ MIRA3 operated at 26 kV
with the electron gun filament: tungsten. TEM observa-
tions were carried out with a Zeiss‐EM10C (Germany)
operating at 100 kV with samples on formvar carbon‐
coated grid Cu mesh 300. The elemental palladium con-
tent of nanocatalyst was determined by Perkin Elmer
Optima 7300D inductively coupled plasma (ICP). X‐rays
diffraction (XRD) patterns were obtained using STOE
STADI‐P diffractometer (Cu K‐alpha1 radiation
wavelength = 1.54060 Å).
3.3 | Synthesis of GO‐CPTMS
The prepared GO (0.5 gr) was dispersed in 10.0 mL of tol-
uene by ultrasonic treatment for 15 min. Then, CPTMS
(0.8 mL) was added to the mixture. At reflux temperature,
the resulting mixture was stirred for 24 hr. Finally, after air
cooling, the mixture was centrifuged and the solid
obtained on the filter was dried at room temperature.
3.4 | Preparation of HPTPy
To a solution of 4‐anisaldehyde (0.12 mL, 1 mmol) in eth-
anol (5 mL) was added 2‐acetylpyridine (0.22 ml, 2 mmol)
and potassium hydroxide (0.15 g, 2 mmol). After stirring
TABLE 7 Comparison of the efficiency of the synthesized catalyst with some previously reported catalysts in cross‐coupling reactions
Entry
Reaction
Conditions
Pd (mol%)
Time
Yielda (%)
[65]
1
2
3
4
5
6
7
8
GO/NHC‐Pd, Na3PO4.12H2O, H2O, 100 °C
1
1
1
6 h
1 h
91.6
98
87
100
99
98
GO–NHC–Pd, Cs2CO3, DMF/H2O, 50 °C[66]
[67]
GO‐NH2‐Pd, K2CO3, EtOH/H2O, 60 °C
30 min
30 min
2 h
2.5 h
15 min
3 h
[68]
GO–2 N–Pd (II), K2CO3, EtOH, 80 °C
0.5
0.01
0.1
10
[69]
Pd‐slGO‐60, K2CO3, EtOH, rt
[70]
NHC‐Pd/GO‐ Ionic Liquid, K2CO3, EtOH/H2O, 60 °C
GO‐CPTMS@Pd‐TKHPP, K2CO3, EtOH/H2O, 80 °C[26]
99
95
This work
1.38
9
GO/NHC‐Pd, K2CO3, H2O,
1
12 h
80
120 °C[65]
10
11
12
13
14
15
16
Pd/Metformin/GO, Et3N, DMF, 110 °C[71]
TRGO‐NPy‐Pd, Na2CO3, DMF, 140 °C[72]
ERGO‐Pd, Et3N, DMF, 120 °C[73]
Pd/GO, C16TAB, 50% aq. EG, 80 °C[74]
GO‐PMMA‐Pd, H2O, K2CO3,TBAB, 100 °C[75]
GO‐CPTMS@Pd‐TKHPP, K2CO3, DMF, 120 °C[26]
This work
0.1
0.3
0.3
0.09
0.2
10
1 h
5 h
2 h
24 h
4 h
96
97
91
96
80
95
95
20 min
4 h
1.38
aIsolated yields.

BAHRAMI AND TARGHAN
11 of 13
at room temperature, to the mixture was added ammo-
nium hydroxide (2.9 mL, 2.5 mmol) and stirring was con-
tinued for 8 hr. The resulting precipitate was filtered and
recrystallized from ethanol to produce 4′‐(4‐
methoxyphenyl)‐2,2′:6′,2″‐terpyridine as white crystals
in 85% yield (Found: Mp = 156 °C).[35] Then 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. The mixture was allowed to cool to
room temperature. The resultant solution was then basi-
fied to pH = 10 by adding aqueous NaOH (20%) dropwise
and extracted repeatedly with CH2Cl2. The 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 in 60% yield
(Found: Mp = 290 °C,[35] IR (KBr): 3385, 1594, 1526,
3.7 | Synthesis of (1,4‐C6H4)(GO‐
CPTMS@HPTPy‐Pd‐TPy)2
0.1. g of GO‐CPTMS@TPy was sonicated in 5 mL etha-
nol for 10 min. To the resulting mixture Pd (Cl)2
(0.03 gr, 0.169 mmol) and TPy‐C6H4‐TPy (0.054 gr,
0.1 mmol) were added and refluxed for 24 hr. Then,
the mixture was filtered and the solid catalyst was
washed with EtOH and deionized water to remove
the excess TPy‐C6H4‐TPy and PdCl2 and dried
under vacuum for 24 hr. ICP showed 0.138 mmol
of palladium is loaded on the 0.1 gr of (1,4‐C6H4)
(GO‐CPTMS@HPTPy‐Pd‐TPy)2 (14.7 wt%).
3.8 | General procedure for Suzuki–
Miyaura cross‐ coupling reactions
1460, 1175, 779 and 734 cm−1 1H NMR (250 MHz,
.
DMSO‐d6): δ = 9.03–9.06 (d, J = 7.75 Hz, 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, OH).[13] 13C NMR
(250 MHz, DMSO‐d6): δ = 160.21, 151.23, 150.35,
146.08, 143.50, 132.12, 129.33, 128.40, 127.00, 124.17,
120.01, 116.45. MS: 327, 326, 325(M+), 324, 308, 297,
296, 248, 247, 221, 220, 219, 218, 190, 163, 78, 51.
The catalyst (0.01 gr, 1.38 mol%) was dispersed in a mix-
ture of EtOH/H2O (2/1). ArX (1.2 mmol), ArB (OH)2
(1 mmol) and K2CO3 (1.5 mmol) were added consecu-
tively. The mixture was then stirred in an 80 °C oil bath
for an appropriate reaction time. The progress of the reac-
tion was monitored by TLC. After completion of the reac-
tion, ethyl acetate (10 mL) was added into the reaction
mixture, the catalyst was separated by centrifugation
and the organic solvent was evaporated to obtain a biaryl
product.
3.5 | Synthesis of GO‐CPTMS@TPy
The GO‐CPTMS (0.1 gr) was dispersed in DMF (10 mL)
and HPTPy (0.0325 g, 0.1 mmol), Na2CO3 (0.04 g,
0.4 mmol) and KI (0.05 g, 0.3 mmol) were added. The
mixture was heated to reflux for 24 hr. The excess of
HPTPy and sodium and potassium salts were removed
by washing three times with EtOH and deionized H2O,
respectively. Eventually, the obtained GO‐CPTMS@TPy
was separated and dried at 50 °C.
3.9 | General procedure for Mizoroki
−Heck cross‐ coupling reactions
To a flask, a mixture of the catalyst (0.01 gr, 1.38 mol%),
aryl halide (1 mmol), styrene (1.2 mmol) and Et3N
(3 mmol) was added and heated at 100 °C under
solvent‐free conditions for a specific time. When the reac-
tion was completed as indicated by TLC, ethylacetate
(10 mL) was added to the flask. The catalyst was sepa-
rated by centrifugation. Water (3 × 15 mL) was added
to the ethylacetate phase and decanted. After evaporation
of the solvent, the resulting crude products were product
was purified in hexane–ethylacetate giving the pure prod-
ucts in high to excellent yields.
3.6 | Preparation of TPy‐C6H4‐TPy
A mixture of 2‐acetylpyridine (0.9 mL, 8.3 mmol),
benzene‐1,4‐dicarbaldehyde (0.27 g, 2.1 mmol) and 15%
aq. KOH (2.9 mL) in ethanol (20 mL) was stirred. After
stirring at room temperature, NH4OH (29 mL) was added
to the solution and vigorous stirring was maintained at
refluxing temperature for 48 hr. After this time, the
resulting mixture was cooled, and the precipitate col-
lected by filtration, washed with ethanol and water and
dried. The 1,4‐bis(2,2′:6′,2″‐terpyridin‐4′‐yl)benzene
(TPy‐C6H4‐TPy) was obtained in 50% isolated yield.
(Found: Mp > 320 °C,[38] IR (KBr): 1588, 1560, 1469,
3.10 | General procedure for arylation of
amines and phenols
A mixture of aryl halide (1 mmol), amine or phenol
(1 mmol), K2CO3 (3 mmol) and the Pd nanocatalyst
(0.01 gr, 1.38 mol%) in DMF (3.0 mL) was stirred at
100 °C (oil bath temperature). After completion of the
1
1388, 785 and 734 cm−1. H NMR (250 MHz, (CDCl3):
δ = 8.69–8.81 (m, 12H), 7.99–8.07 (m, 8H), 7.38 (s, 4H).

12 of 13
BAHRAMI AND TARGHAN
[13] M. Gholinejad, F. Hamed, P. Biji, Dalton Trans. 2015, 44,
reaction, which was monitored by TLC, ethylacetate
(10 mL) was added to the mixture reaction. The catalyst
was separated by centrifugation. Water (15 mL) was
added to the ethylacetate phase and decanted. After evap-
oration of the solvent, the resulting crude products were
product was purified in ethanol–water giving the pure
products in high to excellent yields.
14293.
[14] V. Polshettiwar, A. Molnár, Tetrahedron 2007, 63, 6949.
[15] L. Yin, J. Liebscher, Chem. Rev. 2007, 107, 133.
[16] M. Lamblin, L. Nassar‐Hardy, J. C. Hierso, E. Fouquet, F. X.
Felpin, Adv. Synth. Catal. 2010, 352, 33.
[17] M. Mora, C. Jimenez‐Sanchidrian, J. Rafael Ruiz, Curr. Org.
Chem. 2012, 16, 1128.
[18] L. Djakovitch, F. X. Felpin, ChemCatChem 2014, 6, 2175.
4 | CONCLUSIONS
[19] T. Baran, I. Sargın, M. Kaya, P. Mulerčikas, S. Kazlauskaitė, A.
Mentes, Chem. Eng. J. 2018, 331, 102.
In summary, we have successfully prepared and charac-
terized GO supported palladium nanoparticles as a highly
efficient and general nanocatalyst that is produced by an
inexpensive and simple method. As expected, this
nanocatalyst exhibited excellent activity in the cross‐
coupling reactions. Ultimately, we believe that this work
provides directions for future rational design and produc-
tion of nanocatalysts and heterogenization of metal cata-
lysts. Further studies will be devoted to extend the
development of this class of nanocatalysts in order to
improve their catalytic efficiency in cross‐coupling
reactions.
[20] R. Jin, Nanotechnol. Rev. 2012, 1, 31.
[21] V. Polshettiwar, R. S. Varma, Green Chem. 2010, 12, 743.
[22] X. Chen, G. Wu, J. Chen, X. Chen, Z. Xie, X. Wang, J. Am.
Chem. Soc. 2011, 133, 3693.
[23] L. Wang, Y. Wang, X. Wang, X. Feng, X. Ye, J. Fu,
Nanomaterials 2018, 8, 113.
[24] D. Astruc, F. Lu, J. R. Aranzaes, Angew. Chem. Int. Ed. 2005,
44, 7852.
[25] A. M. Dimiev, J. M. Tour, ACS Nano 2014, 8, 3060.
[26] K. Bahrami, S. N. Kamrani, Appl. Organomet. Chem. 2018, 32,
4102.
[27] D. C. Marcano, D. V. Kosynkin, J. M. Berlin, A. Sinitskii, Z.
Sun, A. Slesarev, L. B. Alemany, W. Lu, J. M. Tour, ACS Nano
2010, 4, 4806.
ACKNOWLEDGEMENTS
[28] J. Paredes, S. Villar‐Rodil, A. Martínez‐Alonso, J. Tascon, Lang-
muir 2008, 24, 10560.
The authors acknowledge the Razi University Research
Council for support of this work.
[29] F. Li, J. Zhao, Z. Chen, J. Phys. Chem. C 2012, 16, 2507.
[30] D. Chen, H. Feng, J. Li, Chem. Rev. 2012, 112, 6027.
[31] S. Ray, Applications of graphene and graphene‐oxide based
nanomaterials, William Andrew, USA, 2015.
ORCID
[32] G. T. Morgan, F. H. Burstall, J. Chem. Soc. 1932, 20.
Kiumars Bahrami https://orcid.org/0000-0001-9229-0890
[33] D. Dong, Z. Li, D. Liu, N. Yu, H. Zhao, H. Chen, J. Liua, D. Liu,
New J. Chem. 2018, 42, 9317.
REFERENCES
[34] C. Zanardi, B. Zanfrognini, S. Morandi, F. Terzi, L. Pigani, L.
[1] P. Devendar, R. Qu, W. Kang, B. He, G. Yang, J. Agric. Food
Chem. 2018, 66, 8914.
Pasquali, R. Seeber, Electrochim. Acta 2018, 260, 314.
[35] W. Spahni, G. Calzagerri, Helv. Chim. Acta 1984, 67, 450.
[2] G. C. Fortman, S. P. Nolan, Chem. Soc. Rev. 2011, 40, 5151.
[3] J.‐P. Corbet, G. Mignani, Chem. Rev. 2006, 106, 2651.
[4] N. Yasuda, J. Organomet. Chem. 2002, 653, 279.
[36] W. S. Hummers Jr., R. E. Offeman, J. Am. Chem. Soc. 1958, 80,
1339.
[37] K. Bahrami, M. M. Khodaei, F. S. Meibodi, Appl. Organomet.
Chem. 2017, 31, 3627.
[5] D. Sierra, G. Brito, M. Fuentealba, A. H. Klahn, Inorg. Chem.
Commun. 2018, 88, 30.
[38] S. Vaduvescu, P. G. Potvin, Eur. J. Inorg. Chem. 2004, 8, 1763.
[6] P. Ruiz‐Castillo, S. L. Buchwald, Chem. Rev. 2016, 116, 12564.
[39] C. Putta, V. Sharavath, S. Sarkara, S. Ghosh, RSC Adv. 2015, 5,
6652.
[7] D. Lopez‐Tejedor, B. Rivas, J. M. Palomo, Molecules 2018, 23,
2358.
[40] C. B. Putta, S. Ghosh, Adv. Synth. Catal. 2011, 353, 1889.
[41] N. Basavegowda, K. Mishra, Y. R. Lee, New J. Chem. 2014, 39, 72.
[8] D. H. Howe, R. M. McDaniel, A. J. D. Magenau, Macromole-
cules 2017, 50, 8010.
[42] M. R. Shaik, Z. J. Q. Ali, M. Khan, M. Kuniyil, M. E. Assal, H.
Z. Alkhathlan, A. Al‐Warthan, M. R. H. Siddiqui, M. Khan, S.
F. Adil, Molecules 2017, 22, 165.
[9] S. Chu, N. Münster, T. Balan, M. D. Smith, Angew. Chem. Int.
Ed. 2016, 55, 14306.
[10] S. N. Jadhav, A. S. Kumbhar, C. V. Rode, R. S. Salunkhe, Green
Chem. 2016, 18, 1898.
[43] E. Ramirez, S. Jansat, K. Philippot, P. Lecante, M. Gomez, A. M.
Masdeu‐Bulto, B. Chaudret, J. Organom. Chem. 2004, 689, 4601.
[11] C. C. Johansson Seechurn, M. O. Kitching, T. J. Colacot, V.
[44] S. Sobhani, Z. Zeraatkar, F. Zarifi, New J. Chem. 2015, 39, 7076.
Snieckus, Angew. Chem. Int. Ed. 2012, 51, 5062.
[45] A. Villa, D. Wang, P. Spontoni, R. Arrigo, D. S. Su, L. Pratia,
[12] J. M. Brown, Angew. Chem. Int. Ed. 2015, 54, 5003.
Catal. Today 2010, 157, 89.

BAHRAMI AND TARGHAN
13 of 13
[46] U. Yilmaz, H. Kucukbay, S. T. Celikesir, M. Akkurt, O.
[67] N. Shang, C. Feng, H. Zhang, S. Gao, R. Tang, C. Wang, Z.
Buyukgungor, Turk. J. Chem. 2013, 37, 721.
Wang, Cat. Com. 2013, 40, 111.
[47] F. Durap, O. Metin, M. Aydemir, S. Ozkar, Appl. Organomet.
Chem. 2009, 24, 498.
[68] C. Bai, Q. Zhao, Y. Li, G. Zhang, F. Zhang, X. Fan, Catal. Lett.
2014, 144, 1617.
[48] P. Kumar, G. Singh, D. Tripathi, S. L. Jain, RSC Adv. 2014, 4,
[69] S. Yamamoto, H. Kinoshita, H. Hashimoto, Y. Nishina, Nano-
scale 2014, 6, 6501.
50331.
[49] Y. Y. Peng, J. Liu, X. Lei, Z. Yin, Green Chem. 2010, 12, 1072.
[70] A. S. K. Movahed, R. Esmatpoursalmani, A. Bazgir, RSC Adv.
2014, 4, 14586.
[50] X. Zeng, T. Zhang, Y. Qin, Z. Wei, M. Luo, Dalton Trans.
2009, 8341.
[71] H. Veisi, N. Mirzaee, Appl. Organomet. Chem. 2018, 23, e4067.
[51] D. Hey, S. Orman, G. H. Williams, J. Chem. Soc. 1965, 101.
[52] N. A. Bumagin, V. V. Bykov, Tetrahedron 1997, 53, 14437.
[53] H. J. Xu, Y. Q. Zhao, X. F. Zhou, J. Org. Chem. 2011, 76, 8036.
[72] L. Fernández‐García, M. Blanco, C. Blanco, P. Álvarez, M.
Granda, R. Santamaría, R. Menéndez, J. Mol. Catal. A: Chem
2016, 416, 140.
[73] S. S. Shendage, J. M. Nagarkar, Colloids Interface Sci Commun
2014, 1, 47.
[54] N.
Iranpoor,
H.
Firouzabadi,
A.
Tarassoli,
M.
Fereidoonnezhad, Tetrahedron 2010, 66, 2415.
[74] A. Saito, S. Yamamoto, Y. Nishina, RSC Adv. 2014, 4, 59835.
[75] P. Basak, P. Ghosh, Synth. Commun. 2018, 48, 1.
[55] F. M. Beringer, A. Brierley, M. Drexler, E. M. Gindler, C. C.
Lumpkin, J. Am. Chem. Soc. 1953, 75, 2708.
[56] L. Hayward, R. Kitchen, D. Livingstone, Can. J. Chem. 1962,
40, 434.
SUPPORTING INFORMATION
[57] H. Zhang, Q. Cai, D. Ma, J. Org. Chem. 2005, 70, 5164.
[58] W. W. Leake, R. Levine, J. Am. Chem. Soc. 1959, 81, 1169.
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
[59] H. J. Cristau, P. P. Cellier, S. Hamada, J. F. Spindler, M.
Taillefer, Org. Lett. 2004, 6, 913.
[60] H. Xu, F. Ye, H. L. Dai, Chin. J. Chem. 2008, 26, 1465.
[61] H. M. Colquhoun, D. F. Lewis, Polymer 1988, 29, 1902.
How to cite this article: Bahrami K, Targhan H.
A new strategy to design a graphene oxide
supported palladium complex as a new
[62] R. Begunov, A. Valyaeva, V. Belyaev, N. Dobretsova, Russ.
Chem. Bull. 2015, 64, 1971.
[63] J. S. Sawyer, E. A. Schmittling, J. A. Palkowitz, W. J. Smith,
J. Org. Chem. 1998, 63, 6338.
heterogeneous nanocatalyst and application in
carbon–carbon and carbon‐heteroatom cross‐
coupling reactions. Appl Organometal Chem. 2019;
e4842. https://doi.org/10.1002/aoc.4842
[64] H. Keipoura, A. Hosseini, A. Afsari, R. Oladee, M. A.
Khalilzadeh, T. Ollevier, Can. J. Chem. 2016, 94, 95.
[65] S. Kim, H. Cho, D. Shin, S. Lee, Tetrahedron Lett. 2017, 58, 2421.
[66] J. H. Park, F. Raza, S. Jeon, H. Kim, T. W. Kang, D. B. Yim, J.
Kim, Tetrahedron Lett. 2014, 55, 3426.