Heterogenized Cu (II) salen complex grafted on graphene oxide nanosheets as a precursing catalyst for the Pd-free Sonogashira coupling

Article abstract of DOI:10.1002/aoc.4545

Cu (II) salen complex immobilized on graphene oxide nanosheets [Cu (II) salen@GO] was synthesized with 3-chloropropyltrimethoxysilan as a linker and wholly characterized using various techniques like X-ray diffraction, Fourier-transform infrared, scanning electron microscopy/energy-dispersive X-ray spectroscopy, transmission electron microscopy, as well as atomic absorption spectroscopy (AAS). Cu (II) salen@GO as an effective heterogeneous catalyst has been investigated for the Sonogashira coupling reaction in dimethylsulfoxide with good to high yield (98%) in 4?hr at 110°C when the loading of Cu was 0.7?mmol?g^?1 based on Cu element analysis by AAS. It was understood that heterogeneous catalyst was as active as its homogeneous analog, and presented good recoverability and no significant loss in activity within successive runs.

Full text of DOI:10.1002/aoc.4545

Received: 9 February 2018
DOI: 10.1002/aoc.4545
Revised: 8 June 2018
Accepted: 15 July 2018
F U L L P A P E R
Heterogenized Cu (II) salen complex grafted on graphene
oxide nanosheets as a precursing catalyst for the Pd‐free
Sonogashira coupling
Mahdieh Ghabdian1
| Mohammad A. Nasseri1 | Ali Allahresani1
|
Alireza Motavallizadehkakhky2
1 Department of Chemistry, Faculty of
Science, University of Birjand, P.O. Box
97175‐615, Birjand, Iran
2 Department of Chemistry, Neyshabur
Branch, Islamic Azad University, P.O. Box
9318813‐639, Neyshabur, Iran
Cu (II) salen complex immobilized on graphene oxide nanosheets [Cu (II)
salen@GO] was synthesized with 3‐chloropropyltrimethoxysilan as a linker
and wholly characterized using various techniques like X‐ray diffraction,
Fourier‐transform infrared, scanning electron microscopy/energy‐dispersive
X‐ray spectroscopy, transmission electron microscopy, as well as atomic
absorption spectroscopy (AAS). Cu (II) salen@GO as an effective heteroge-
neous catalyst has been investigated for the Sonogashira coupling reaction in
dimethylsulfoxide with good to high yield (98%) in 4 hr at 110°C when the
loading of Cu was 0.7 mmol g−1 based on Cu element analysis by AAS. It
was understood that heterogeneous catalyst was as active as its homogeneous
analog, and presented good recoverability and no significant loss in activity
within successive runs.
Correspondence
Mahdieh Ghabdian, Department of
Chemistry, Faculty of Science, University
of Birjand, P.O. Box 97175‐615, Birjand,
Iran.
Email: ghabdianm@birjand.ac.ir
Funding information
University of Birjand
KEYWORDS
Cu (II) salen@GO nanocatalyst, heterogeneous catalysis, Sonogashira reaction
1 | INTRODUCTION
were first introduced by Rothenberg and his co‐workers,
use one of the most abundant and readily available
The Sonogashira cross‐coupling reaction of terminal
alkynes with aryl halides that produces aryl alkynes that
are valuable intermediates in versatile agrochemicals,
medicines and functional organic molecules synthesis
has had a lot of attention over the past decade.[1–5] Com-
mon procedures for the Sonogashira coupling reaction
apply costly palladium along with a metal co‐catalyst
and a base.[6] The most broadly utilized co‐catalysts are
copper salts, zinc, tin, boron, aluminum, Ag2O and Ag
(OTf).[7–11] Recently, palladium‐free catalysis has been
surveyed, and cheap metals like iron and nickel have
been used as catalysts as well, but the use of such metals
creates some problems, including requiring copper as a
co‐catalyst, complex ligands, zinc additives and tough
reaction conditions.[12–14] Copper‐based catalysts, which
metals that can catalyze palladium‐free Sonogashira cross
coupling reactions.[15–21]
However, some reports suggest limitations, including
multi‐step operation for synthesizing the Cu nanoparti-
cles, a relatively large amount of the Cu catalyst, and Cu
(I) instability against oxidation. Therefore, development
of Cu (II) catalysts with more effective copper in smaller
catalytic amounts and less demanding synthetic
procedures is desirable.[22] The use of nanocatalysts can
be an effective key for these problems. Nanocatalysis can
assist in designing excellent catalysts with greater activity
and selectivity, and high stability, but the separation of
nanoparticles from the reaction mixtures has still
restricted their practical applications. Thus, the design of
heterogenized nanocatalysts is pretty interesting for
Appl Organometal Chem. 2018;e4545.
wileyonlinelibrary.com/journal/aoc
© 2018 John Wiley & Sons, Ltd.
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GHABDIAN ET AL.
economic as well as environmental causes.[14] A wide
variety of approaches to obtain an ideal heterogenized
metal catalyst have been studied. Covalent binding of
metal complexes onto the support through a ligand spacer
is the most efficient and widely used strategy amongst
them. Therefore, a wide range of matrixes has been
developed for metal complexes covalent attachment, for
example, inorganic mesoporous materials, organic
polymers, SBA‐15, MCM‐41, zeolite and dendrimers.[23–26]
Among them, graphene oxide (GO) with fascinating
two‐dimensional structures and exclusive characteristics
has emerged as ideal support for various catalytic species.
In addition to the availability of surface functionalization,
the two‐dimensional structures allow excellent dispersion
of the catalytic species.[27] GO is a lamellar flexible mate-
rial with a great number of functional groups, such as
epoxy (C–O–C), hydroxyl (‐OH) on basal planes and car-
boxyl (‐COOH) groups on the edges, and is inexpensive in
comparison with zeolites such as MCM‐41 and SBA‐15,
allowing it to be the ideal option for catalyst supports.[28]
In this article, Cu (II) salen complex was grafted onto the
surface of GO nanosheets [Cu (II) salen@GO], and a
promising protocol for Sonogashira coupling of aryl
FIGURE 1 Fourier‐transform infrared (FT‐IR) spectra of (a)
salen complex (1), (b) 2, (c) heterogeneous catalyst Cu (II)
salen@GO (d) GO
FIGURE 3 (a) The scanning electron microscopy (SEM) image
and (b–d) transmission electron microscopy (TEM) of
heterogeneous catalyst Cu (II) salen@GO
FIGURE 2 The X‐ray diffraction (XRD) patterns of (a) graphene
oxide (GO) and (b) heterogeneous catalyst

GHABDIAN ET AL.
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halides with terminal acetylenes using heterogenized Cu
(II) salen@GO in dimethylsulfoxide (DMSO) media
applying K2CO3 as a base at 110°C for 4 hr in high yield
is presented.
and a significant decrease in intensities of peaks such as
3414 cm−1, 1737 cm−1 and 1385 cm−1, which correspond
to the OH, C=O stretching vibration and O–H deforma-
tion peak, respectively, suggest the grafting of homoge-
neous Cu salen ligand complex on GO surface.
Moreover, Figure 2 shows the X‐ray diffraction (XRD)
patterns of GO and heterogeneous catalyst. Upon oxida-
tion of graphite, the basal reflection (002) peak appeared
at 2θ = 26.6° (d spacing = 0.335 nm) and shifts to a lower
angle (2θ = 11.79°, d spacing = 0.79 nm; Figure 2a). The
decrease in the intensity of the 002 reflection peak of GO
and the appearance of a broad peak that appeared at
2θ = 15–27° indicated the immobilization of 3 on the GO
(Figure 2b).
The morphological properties of Cu (II) salen @GO
were determined by means of transmission electron
microscopy (TEM) and scanning electron microscopy
(SEM). The TEM and SEM images of Cu (II) salen @GO
(Figure 3a–d) revealed the nanoscopic features of GO.
The energy‐dispersive X‐ray spectroscopy (EDX) mapping
of Cu salen @GO demonstrated that the elements N, O
and Si (Figure 4) are homogeneously distributed on the
whole surface of this compound, which indicates that
the functional groups are anchored uniformly on GO,
whereas EDX of GO just recognizes the elements C, O.
These results proved that copper salen complex (3)
immobilized on GO surface successfully. Analysis by
atomic absorption spectroscopy (AAS) demonstrated that
0.7 mmol g−1 based on Cu element was the loading of
homogeneous Cu (II) complex (3) in the heterogeneous
catalyst.
2 | RESULTS AND DISCUSSION
In this study, the Cu (II) salen complex was immobilized
onto GO support through an in situ strategy. Briefly, in
order to produce a Schiff‐base, 2‐hydroxy benzaldehyde
was condensated with the diethylentriamine, then for
the protection of the NH group against bonding with
metal and playing the role of coupling agent with GO in
the last section, 3‐chloropropyltrimethoxysilane was
added, later Cu (OAC)2 was added to prepare the copper
salen complex. Eventually the synthesized copper salen
complex anchored onto the GO.
A broad peak appearing at 3399 cm−1 in the Fourier‐
transform infrared (FT‐IR) spectrum of GO (Figure 1d)
revealed the abundance of hydroxyl groups in GO. The
strong band at 1735 cm−1 (C=O) and 1059 cm−1 (C‐O)
revealed the presence of stretching vibration in carboxylic
acid and epoxy functional groups in GO. The peak at
1619 cm−1 showed C=C stretching vibration in the
aromatic ring. The IR spectra of the ligand salen (1)
showed an enhanced, sharp band at almost 1635 cm−1
,
which is assigned to the stretching vibration of the C=N
group (Figure 1a). Figure 1b, which is assigned to salen
after reaction with 3‐chloropropyltrimethylsilane, shows
peaks at 1080 cm−1 and 1049 cm−1 that provide direct evi-
dence for the strong stretching vibrations of Si‐O in 2. In
the spectrum of Cu (II) salen@GO (Figure 1c), the band
related to the C=N functional group shifts to a lower
position (∼15 cm−1) compared with the Schiff‐base. This
red shift to relatively lower frequency might be attributed
to the coordination of Cu through C=N. The new
The catalytic activity of Cu (II) salen@GO was
investigated towards the C‐C coupling of iodobenzene
with phenylacetylene as a model for the Sonogashira
reaction. The effects of different reaction parameters,
such as the amount of catalyst, solvent, base and
temperature, were evaluated (Table 1). To optimize the
amount of catalyst, the reaction was carried out in the
stretching vibration bands at 1620 cm−1 and 1080 cm−1
,
FIGURE 4 The scanning electron microscopy (SEM) images and corresponding energy‐dispersive X‐ray spectroscopy (EDX) analysis of (a)
graphene oxide (GO) and (b) heterogeneous catalyst Cu (II) salen@GO

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GHABDIAN ET AL.
presence of different amounts of heterogeneous Cu (II)
complex (0.25–2.5 mol% based on Cu element) at
110°C. It was found that by increasing the amount of
catalyst from 0.25 mol% to 2 mol%, the yields increased
from 35% to 98%, and an additional amount of catalyst
did not show any significant effect on the conversion
of the products (Table 1, entries 1–6). For comparison,
the homogeneous Cu (II) complex (3) was also investi-
gated under the same reaction conditions, (Table 1,
entry 7). The application of only GO afforded a low yield
of the corresponding cross‐coupling product and, in the
absence of heterogeneous catalyst, we did not observe
any product (Table 1, entries 8, 9).
As shown in Table 1, the effect of solvent was consid-
ered in this coupling reaction. The best performance of
the catalytic system was observed when DMSO was used
(Table 1, entry 5).
It is a well‐known fact that base plays a crucial role in
the overall performance of a catalytic system in a
Sonogashira reaction (Table 1, entry 18). Thus, to investi-
gate its effect, several inorganic and organic bases were
tested in the Sonogashira reaction of iodobenzene
(1 mmol) and phenylacetylene (1.2 mmol) with Cu (II)
salen @GO catalyst (2 mol%) in DMSO (2 ml; Table 1,
entries 5, 19–25). Among the bases evaluated, K2CO3
was the best choice.
TABLE 1 Optimization of the conditions for Sonogashira coupling reactions of iodobenzene with phenylacetylenea
Entry
Catalyst (mol%)
Solvent
Base
Temp (°C)
Time (hr)
Yield (%)b
1
Cu (II)salen@GO (0.25 mol%)
Cu (II) salen@GO (0.5 mol%)
Cu (II) salen@GO (1 mol%)
Cu (II) salen@GO (1.5 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2.5 mol%)
Homogeneous Cu (II) salen complex (3; 2 mol%)
GO (2 mol%)
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
MeOH
EtOH
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
–
110
110
110
110
110
110
110
110
110
60
4
4
35
48
2
3
4
56
4
4
73
5
4
98
6
4
97
7
4
98
8
10
10
4
8
9
No catalyst
n.r
63
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
Cu (II) salen@GO (2 mol%)
60
4
75
DMF
110
90
7
90
Isopropanol:H2O
H2O
7
67
90
10
10
10
7
23
CH3CN
THF
82
45
60
35
Isopropanol
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
82
80
110
110
110
110
110
110
110
110
25
24
7
Trace
85
Na2CO3
Cs2CO3
KOH
10
12
12
12
12
12
12
4
80
52
NaOH
NaHCO3
Et3N
45
75
71
Pyridine
K2CO3
K2CO3
K2CO3
67
Trace
56
80
160
4
98
aReaction conditions: iodobenzene (1 mmol), phenylacetylene (1.2 mmol), Cu (II) salen@GO (2 mol%), base (3 mmol), solvent (2 ml) at different temperatures.
bDetermined by GC with a CBP1 column (Shimadzu 30 m × 0.32 mm × 0.25 mm).
DMF, dimethylformamide; DMSO, dimethylsulfoxide; GO, graphene oxide; THF, tetrahydrofuran.

GHABDIAN ET AL.
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Temperature plays an important role in the yield of
halides. As shown in Table 2, various electron‐donating
and electron‐withdrawing groups, such as –CH3, –NH2,
–CN, –COCH3 and –NO2, on aryl halide underwent
Sonogashira coupling reaction smoothly giving desired
products with appreciable yields. Aryl iodides containing
electron‐withdrawing groups, such as –COCH3, –CN and
–NO2, were found to be more active than aryl iodides
containing electron‐donating groups, such as –CH3 and
–NH2. Iodobenzene reacted with phenylacetylene giving
98% yield of diphenylacetylene (Table 2, entry 1). The
coupling reactions of aryl iodides and aryl bromides
occurred in short time with good to high yields, while
aryl chlorides due to the low reactivity of the C–Cl bond
cannot produce convincing yields of coupling products
the reaction. We also performed the model reaction at
different temperatures in DMSO in the presence of
heterogeneous catalyst and K2CO3 (25°C, 80°C, 110°C
and 160°C). There was a considerable decrease in the
yield at 25°C (Table 1, entry 26). The reaction proceeded
faster at 80°C compared with 25°C. However, when the
temperature was higher than 80°C (110°C and 160°C),
an obvious intensive increase was observed in the yield
of coupling reaction (Table 1, entries 5, 27, 28). Thus,
we came to the conclusion that the optimum temperature
is 110°C.
The scope and limitation of the current protocol have
been investigated with several electronically diverse aryl
TABLE 2 The synthesis of internal acetylene promoted by Cu (II) salen@ GO
Entry
Ar‐X
Time (hr)
Yield (%)
TON
1
4
98
2800
2
5
83
2371
3
4
4
82
82
87
90
86
95
82
80
95
80
87
2342
2342
2485
2571
2457
2714
2342
2285
2714
2285
2485
4
5
4
6
4
7
8
8
6
9
6
10
11
12
13
6
5
6
10
14
15
16
6
6
6
65
70
88
1857
2000
2514
TON, turnover number.

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GHABDIAN ET AL.
TABLE 3 Comparison of the efficiency of Cu (II) salen@GO with different catalysts
Entry
X
Catalyst
Solvent
Base
Temp (°C)
Time (hr)
Yield (%)
Ref.
[29]
1
Br
I
CuI
Dioxane
Solvent‐free
Toluene
DMF
K2CO3
TBAFa
K2CO3
Cs2CO3
KOH
100
24
14
24
10
9
62
85
80
94
80
66
90
98
96
85
95
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
2
Cu (OAC)2·H2O
Cu (phen)(PPh3)Br
CuI
130–135
110
3
I
4
I
135–140
140
5
Br
I
Choline chloride/CuCl
Pd/C
DMF
6
Isopropanol/H2O
DMF
Na3PO4
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
80
0.5
48
7
7
Br
I
Cu NPs
135
8
Pd salen
Isopropanol
Solvent‐free
DMF
25
9
I
Cu2O/PPh3/TBAB
Cu2O@Cu
135–140
110
24
10
6
10
11
I
Br
Cu (II) salen/GO
DMSO
110
Present work
aTBAF, tetra‐n‐butylammonium fluoride.
DMF, dimethylformamide; DMSO, dimethylsulfoxide; GO, graphene oxide.
even after prolonged reaction times (compare entries
1–13 with 14–16), even though aryl bromides required a
longer reaction time to afford the same result as aryl
iodides (compare entries 1–7 with 8–13). This might be
duetotheleavinggroupabilityofhalogens(I>Br>Cl>F).
Furthermore, the turnover number (TON) of the catalyst
was also calculated, and the results are shown in Table 2.
Finally, we have developed a tetradentate Schiff‐base
derived from the copper complex for the Sonogashira
reaction in DMSO at 110°C using K2CO3. The catalyst is
very simple, and the starting materials used are commer-
cially available and cheap. Electronically diversified aryl
iodides underwent the coupling reaction with phenyl
acetylene in excellent yields. The absence of additives
and the broad substrate scope of this protocol make it
an attractive alternative for the existing protocols of the
Sonogashira reaction of aryl halides.
We compared the catalytic performance of our
catalyst with catalysts reported for the Sonogashira cou-
pling reaction (Table 3).[29–38] Though some of them can
also have high yields, the following factors cause our
catalysts to be superior to the others for such reactions.
(i) Well‐dispersed Cu (II) salen complexes over the sup-
port are strongly bound by 3‐chloropropyltrimethoxysilan
as a linker, which in turn offers excellent repeatability
without loss of catalytic activity. (ii) Using low catalyst
SCHEME 1 Schematic illustration for
the preparation of functionalized salen
with 3‐chloropropyltrimethoxysilane (2)
SCHEME 2 Schematic illustration for
the preparation of Cu (II) salen complex
(3)

GHABDIAN ET AL.
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SCHEME 3 Schematic illustration for
the preparation of Cu (II) salen@GO
determined in open capillaries using an Electrothermal
9100 apparatus. FT‐IR spectra were recorded on a VER-
TEX 70 spectrometer (Bruker) in the transmission mode
in spectroscopic‐grade KBr pellets for all the powders.
The particle sizes and structures were observed by using
a Philips CM10 TEM operating at 100 kV. Powder XRD
data were obtained using Bruker D8 Advance model with
Cu kα radiation. The purity determination of the
products and reaction monitoring were accomplished by
thin‐layer chromatography on silica gel polygram SILG/
UV 254 plates. The Cu content of the catalysts was
determined by Shimadzu AA‐6300 AAS. The yields were
determined by Shimadzu GC‐17A gas chromatograph
(GC) equipped with a flame ionization detector with a
capillary column (CBP‐1, 30 m × 0.32 mm × 0.25 mm),
using helium as carrier gas.
FIGURE 5 Reuses performance of the catalysts
loading, we achieved acceptable results in short reaction
times. (iii) A facile and efficient method was used in order
to prepare the low‐cost Cu‐based catalysts. (iv) Large
TON for catalyst reveals that the catalyst is stable and
pretty long‐lived.
4.2 | Synthesis of functionalized salen
with 3‐chloropropyltrimethoxysilane (2)
3 | CONCLUSIONS
The Schiff‐base was prepared with 98.9% yield in the
following way. Diethylentriamine (1.0 mmol) was added
to 2‐hydroxy benzaldehyde (2.0 mmol) in ethanol (5 ml)
mixture and stirred under reflux conditions for 4 hr.
The reaction solution color turned to yellowish, owing
to imine formation. The mixture was then washed three
times with water, methanol and ethanol, and dried at
80°C in the oven under vacuum. In order to achieve the
pure product, the crude product was recrystallized from
ethanol. Salen ligand (1; 1.0 mmol) was dissolved in dry
toluene (15 ml), and then was followed by dropwise addi-
tion of 3‐chloropropyltrimethoxysilane (1.5 mmol),
diluted in 5 ml dry toluene. The resulting mixture was
heated to reflux with non‐stop stirring for 24 hr under
nitrogen atmosphere (Scheme 1). After cooling, the mix-
ture was filtered, washed with ethanol and diethyl ether,
and this was followed by evaporation of the solvent under
reduced pressure to give the crude products with 98%
yield.
We have successfully synthesized new Cu (II) salen
complex tethered onto GO and evidenced by XRD, FT‐
IR, SEM/EDX and TEM. The catalyst exhibited high
catalytic activity towards the C‐C coupling of aryl halides
and phenylacetylene. Catalytic tests showed that the
heterogeneous Cu (II) salen@GO is the most active in
DMSO at 110°C using base. Furthermore, heterogeneous
catalyst showed good recoverability and relatively high
stability against leaching active species, and it can be
recycled many times without any significant loss of
catalytic activity.
4 | EXPERIMENTAL
4.1 | General
Highly pure chemical materials were purchased from
Merck Chemical Company. Melting points were

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GHABDIAN ET AL.
washed using ethanol and dichloromethane, and used
in repeated Sonogashira coupling. No copper was
detected in the filtrates by AAS in each run, as illustrated
in Figure 5, so it is clear that the catalyst worked well for
up to several cycles with no remarkable decrease in
reactivity.
4.3 | Synthesis of Cu (II) salen complex (3)
Functionalized salen ligand (2; 1.0 mmol) was dissolved
in ethanol (20 ml), and then NaOH (1.67 mmol) along
with copper (II) acetate one hydrate (1 mmol) in H2O
(3 ml) were added and the mixture was refluxed for
1 hr (Scheme 2). The resulting mixture was filtered and
washed with methanol, water and diethyl ether three
times, respectively. The solvents were evaporated off
and the residue was recrystallized from EtOH to give a
green solid (98% yield). This was followed by drying at
80°C in an oven under vacuum.
ACKNOWLEDGMENTS
The authors are grateful to the University of Birjand for
financial support.
ORCID
4.4 | General procedure for the
Mahdieh Ghabdian http://orcid.org/0000-0001-9088-6607
Ali Allahresani http://orcid.org/0000-0001-6209-6018
preparation of Cu (II) salen@GO
Graphene oxide was prepared and purified by the Hum-
mers method.[39] GO was dispersed in 75 ml dry toluene
for 20 min. Later, 0.5 g of homogeneous Cu (II) salen
complex (3) was added into the suspension (Scheme 3).
After refluxing for 20 hr, the immobilized catalyst was
washed with dry toluene, EtOH and dichloromethane,
respectively. The solid was dried at 70°C under vacuum
conditions for 6 hr to give Cu (II) salen@GO catalyst with
REFERENCES
[1] K. Sonogashira, J. Organomet. Chem. 2002, 653, 46.
[2] K. Sonogashira, in Metal‐Catalyzed Cross‐Coupling Reactions,
(Eds: F. Diederich, P. J. Stang), Weinheim, Wiley‐VCH Verlag
GmbH 1998 203.
[3] R. Chinchilla, C. Najera, Chem. Soc. Rev. 2011, 40, 5084.
1
99% yield. The H‐ and 13C‐NMR spectra of 3 are consis-
[4] N. Hussain, P. Gogoi, P. Khare, M. R. Das, RSC Adv. 2015, 5. 10
1
tent with the structure of the complex. In the H‐NMR
3105
spectrum of 1, a proton due to –CH=N was observed at
8.34 ppm, which upon coordination to Cu (II) ion showed
a downfield shift and occurred at 8.58 ppm for 3. Also, the
13C‐NMR signals for imine‐carbon of salen ligand
appeared at 166.84 ppm and this value undergoes a
downfield shift (169.44 ppm) upon coordination to Cu
(II) ion (for the NMR spectrum of 1–3, see SI, pp. S1–S6).
[5] S. Diyarbakir, H. Can, O. Metin, ACS Appl. Mater. Interfaces
2015, 5, 3199.
[6] K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. 1975,
16, 4467.
[7] J. Cheng, Y. Sun, F. Wang, M. Guo, J. Xu, Y. Pan, Z. Zhang,
J. Org. Chem. 2004, 69, 5428.
[8] B. Liang, M. Dai, J. Chen, Z. Yang, J. Org. Chem. 2005, 70, 391.
[9] R. Bhaskar, A. K. Sharma, M. K. Yadav, A. K. Singh, Dalton
Trans. 2017, 46. 15 235
4.5 | General procedure for Sonogashira
coupling reaction
[10] V. V. Singh, A. K. Singh, Dalton Trans. 2015, 44, 725.
[11] G. M. Roberts, W. Lu, L. K. Woo, RSC Adv. 2015, 5. 18 960
An aryl halide (1.0 mmol) and phenylacetylene (1.2 mmol)
were added to a mixture of Cu (II) salen @GO (2 mol%),
K2CO3 (3.0 mmol) and DMSO (2 ml) in a glass flask under
vigorous stirring. The reaction mixture was stirred at
110°C for 4 hr. At the end of the reaction, the catalyst
was separated by centrifugation, washed with ethyl acetate
and water, vacuum dried and kept for the next reaction.
Following GC analysis, the solvent was eliminated under
vacuum, and the crude product was subjected to silica
gel column chromatography using n‐hexane–ethyl acetate
as eluent to afford the pure product.
[12] C. X. Lin, J. F. Zhu, Q. S. Li, L. H. Ao, Y. J. Jin, F. B. Xu, F. Z.
Hu, Y. F. Yuan, Appl. Organomet. Chem. 2014, 28, 298.
[13] N. T. Tran, C. S. Cho, H. S. Sohn, S. C. Shim, Bull. Korean
Chem. Soc. 2011, 32, 1080.
[14] L.‐H. Zou, A. J. Johansson, E. Zuidema, C. Bolm, Chem. – Eur.
J. 2013, 19, 8144.
[15] N. Panda, A. K. Jena, S. Mohapatra, Chem. Lett. 2011, 40, 956.
[16] M. B. Thathagar, J. Beckers, G. Rothenberg, Green Chem. 2004,
6, 215.
[17] A. M. Thomas, A. Sujatha, G. Anilkumar, RSC Adv. 2014, 4. 21
688
[18] Z. Li, S. Wu, H. Ding, D. Zheng, J. Hu, X. Wang, Q. Huo, J.
4.6 | Reusability of the catalyst
Guan, Q. Kan, New J. Chem. 2013, 37, 1561.
So as to access the recyclability of the heterogeneous Cu
(II) salen @GO, the heterogeneous catalyst was totally
[19] A. Narani, R. K. Marella, P. Ramudu, K. S. Rama Rao, D. R.
Burri, RSC Adv. 2014, 4, 3774.

GHABDIAN ET AL.
9 of 9
[20] A. Zarnegaryan, M. Moghadam, S. Tangestaninejad, V.
Mirkhani, I. Mohammdpoor‐Baltork, New J. Chem. 2016, 40,
2280.
[34] Y. Monguchi, F. Wakayama, S. Ueda, R. Ito, H. Takada, H.
Inoue, A. Nakamura, Y. Sawamaa, H. Sajiki, RSC Adv. 2017,
7, 1833.
[21] R. Hashemi Fath, S. J. Hoseini, Appl. Organometal. Chem.
2018, 32, 3964.
[35] H. Oka, K. Kitai, T. Suzuki, Y. Obora, RSC Adv. 2017, 7. 22 869
[36] A. Gogoi, A. Dewan, G. Boraha, U. Bora, New J. Chem. 2015,
39, 3341.
[22] M. A. Bhosale, T. Sasaki, B. M. Bhanage, Catal. Sci. Technol.
2014, 4, 4274.
[37] B.‐X. Tang, F. Wang, J.‐H. Li, Y.‐X. Xie, M.‐B. Zhang, J. Org.
Chem. 2007, 72, 6294.
[23] J. Miao, B. Huang, H. Liu, M. Cai, RSC Adv. 2017, 7. 42 570
[24] I. G. Wenten, P. T. Dharmawijaya, P. T. P. Aryanti, R. R. Mukti,
[38] J. Kou, A. Saha, C. Bennett‐Stamper, R. S. Varma, Chem.
Commun. 2012, 48, 5862.
Khoiruddin, RSC Adv. 2017, 7. 29 520
[25] A.‐M. Caminade, Chem. Soc. Rev. 2016, 45, 5174.
[39] W. S. Hummers, R. E. Offeman, J. Am. Chem. Soc. 1958, 80, 1339.
[26] P. McMorn, G. J. Hutchings, Chem. Soc. Rev. 2004, 33, 108.
[27] Y. Gao, P. Tang, H. Zhou, W. Zhang, H. Yang, N. Yan, G.
Hu, D. Mei, J. Wang, D. Ma, Angew. Chem. Int. Ed. 2016,
55, 3124.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
[28] F. Zhang, H. Jiang, X. Wu, Z. Mao, H. Li, ACS Appl. Mater.
Interfaces 2015, 7, 1669.
[29] Y. F. Wang, W. Deng, L. Liu, Q. X. Guo, Chin. J. Chem. 2005,
16, 1197.
[30] C.‐L. Deng, Y.‐X. Xie, D.‐L. Yin, J.‐H. Li, Synthesis 2006, 20,
How to cite this article: Ghabdian M, Nasseri
MA, Allahresani A, Motavallizadehkakhky A.
Heterogenized Cu (II) salen complex grafted on
graphene oxide nanosheets as a precursing catalyst
for the Pd‐free Sonogashira coupling. Appl
Organometal Chem. 2018;e4545. https://doi.org/
10.1002/aoc.4545
3370.
[31] R. K. Gujadhur, C. G. Bates, D. Venkataraman, Org. Lett. 2001,
3, 4315.
[32] J.‐H. Li, J.‐L. Li, D.‐P. Wang, S.‐F. Pi, Y.‐X. Xie, M.‐B. Zhang,
X.‐C. Hu, J. Org. Chem. 2007, 72, 2053.
[33] A. R. Hajipour, S. H. Nazemzadeh, F. Mohammadsaleh,
Tetrahedron Lett. 2014, 55, 654.