Carbonylative Suzuki-Miyaura cross-coupling by immobilized Ni?Pd NPs supported on carbon nanotubes

Article abstract of DOI:10.1039/d0ra03915b

In this study, a novel carbon nanotube (CNT) based nanocatalyst (Ni?Pd/CNT) was synthesized by modifying CNTs using Ni?Pd core-shell nanoparticles (NPs). Ni?Pd/CNT was used in catalytic carbonylative cross-coupling between 4-iodoanisole and phenylboronic acid. The Ni?Pd NPs possessed a magnetic nickel (Ni) core with a palladium (Pd) structural composite shell. Thus, the use of Ni had led to a reduced consumption of Pd without sacrificing the overall catalytic performance, simultaneously making it reusable as it could be conveniently recovered from the reaction mixture by using an external magnetic field. Immobilization of the Ni?Pd NPs on carbon nanotubes not only prevented their aggregation, but also significantly enhanced the accessibility of the catalytically active sites. The abovementioned approach based on carbon nanotubes and Ni?Pd NPs provided a useful platform for the fabrication of noble-metal-based nanocatalysts with easy accessibility and low cost, which may allow for an efficient green alternative for various catalytic reductions. This journal is

Full text of DOI:10.1039/d0ra03915b

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Carbonylative Suzuki–Miyaura cross-coupling by
immobilized Ni@Pd NPs supported on carbon
nanotubes
Cite this: RSC Adv., 2020, 10, 27923
a
b
b
c
Liu Nan, Cai Yalan, Li Jixiang, Ouyang Dujuan,a Duan Wenhui,a Jalal Rouhi
*
*
and Mazli Mustaphad
In this study, a novel carbon nanotube (CNT) based nanocatalyst (Ni@Pd/CNT) was synthesized by
modifying CNTs using Ni@Pd core–shell nanoparticles (NPs). Ni@Pd/CNT was used in catalytic
carbonylative cross-coupling between 4-iodoanisole and phenylboronic acid. The Ni@Pd NPs possessed
a magnetic nickel (Ni) core with a palladium (Pd) structural composite shell. Thus, the use of Ni had led
to a reduced consumption of Pd without sacrificing the overall catalytic performance, simultaneously
making it reusable as it could be conveniently recovered from the reaction mixture by using an external
magnetic field. Immobilization of the Ni@Pd NPs on carbon nanotubes not only prevented their
aggregation, but also significantly enhanced the accessibility of the catalytically active sites. The
abovementioned approach based on carbon nanotubes and Ni@Pd NPs provided a useful platform for
the fabrication of noble-metal-based nanocatalysts with easy accessibility and low cost, which may
allow for an efficient green alternative for various catalytic reductions.
Received 30th April 2020
Accepted 4th July 2020
DOI: 10.1039/d0ra03915b
rsc.li/rsc-advances
It should be noted that many reactions of noble metal nano-
particle catalysts are commonly performed only on the nano-
Introduction
particle site and a wide fraction of atoms within the core can be
inactive catalytically. However, to make a considerable percentage
of noble metal atoms available in catalysis and to reduce their
utilization, the inner atoms of a noble metal can be varied with
other non-noble metals. The existence of a different metal core
usually allows control over catalytic activity, selectivity, and
stability, because of “synergistic inuences” coming from core–
shell metal interactions.10 Transition Fe-group metals such as Fe,
Ni, and Co, among distinct non-noble metals, are generally
hybridized using noble metals for creating magnetic NPs that can
be simply reproduced utilizing an external magnetic area.11–16
However, cost-effective catalysts of noble metal NPs, which possess
great catalytic activities, inactive cores, and effective recoverable
properties are extremely rare.
In organic chemistry, the production of biaryl ketones was
attended with an impressive reaction. Biaryl ketones can be
placed on central construction blocks prepared in a wide
diversity of molecules, which include pharmaceutical drugs and
natural products as well as sunscreen agents. The production of
biaryl ketones is known to be one of the most important and
customary applications through Friedel–Cras acylation.17 It
can also utilize stoichiometric amounts of Lewis acid, and
tolerates adaptability issues with different functional groups.
This can lead to the production of signicant amounts of waste,
so causing poor atom economy. Producing the isomers of ortho
and para that has low regioselectivity, their separation and
availability biaryl ketones and meta substitution are extra issues
Recently, noble metal nanoparticles have been given signicant
consideration as catalysts due to their appropriate catalytic
activity in organic catalytic reactions. The catalytic activity of
noble metal nanoparticles was usually based on size, crystal-
linity, or shape and also the surface zone.1–5 Moreover, the
development of nano-sized metal catalysts in the case of catalyst
supports has been dramatically investigated. Many supporting
materials have been utilized to suggest Pd nanoparticles (NPs)
as catalysts for organic catalytic reactions, like Pd/SBA-15, Pd/
Al2O3, or Pd/C nanospheres.6–9 The pores of considered mate-
rials along with large particular surface zones prevent the
aggregation of NPs, allowing homogeneous scattering in the
catalytic spaces and improving the catalytic activity of the
approach. However, poor accessibility of these active zones into
the pores limits their applications and signicant mass trans-
port is known to be necessary for them. Therefore, silica
supports and the simple availability of high surface zones were
usually desirable.
aChina Key Laboratory of Light Industry Pollution Control and Recycling, Department
of Material and Chemical Engineering, Zhengzhou University of Light Industry,
Zhengzhou 450001, PR China
bShanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai
201210, PR China. E-mail: lijixiang@sari.ac.cn
cFaculty of Physics, University of Tabriz, Tabriz 51566, Iran. E-mail: jalalrouhi@gmail.
com
dCentre for Corrosion Research, Department of Mechanical Engineering, Universiti
Teknologi PETRONAS, 32610 Bandar Seri Iskandar, Perak Darul Ridzuan, Malaysia
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accompanied with the acylation of Friedel–Cras. With determination of FTIR spectra. Samples were pulverized and
different aims, the transition metal catalyzed distinct compo- pelletized with spectroscopic-grade KBr. The determination of the
nent carbonylative cross-coupling between aryl organometallic size and structure of nanoparticles was done with a transmission
and aryl halides reagents, using carbon monoxide (as the C1 electron microscope (TEM) (Phillips CM10) operated at 100 kV.
origin), is known to be a direct protocol.18 Carbonylative Suzuki– The crystallographic structures of nanoparticles were determined
Miyaura cross-coupling was particularly proposed because of its using powder X-ray diffraction (Bruker D8 Advance model) with Cu
broad functional group tolerance along with the fact that aryl Ka radiation. Thermogravimetric analysis (TGA) (NETZSCH
boronic acids are nontoxic, ease of controlling air and moisture STA449F3) was utilized under a nitrogen atmosphere with a heat-
1
ing rate of 10 C minꢁ1. NMR spectra of H and 13C were deter-
ꢀ
and thermal strength.
The development of supported catalysts is the central step in mined with a BRUKER DRX-300 AVANCE spectrometer and
a lot of work because of increasing demands in terms of a BRUKER DRX-400 AVANCE spectrometer. The NMR spectra for
ecologically-viable and economic procedures. Carbonaceous both elements were recorded at 300.13 and 75.46 MHz; and 400.22
materials are considered to be appropriate candidates in terms of and 100.63 MHz, respectively. A Heraeus CHN–O-Rapid analyzer
synthesis supported catalysts.19–22 Carbonaceous materials are was used to perform elemental analyses for carbon, hydrogen and
commonly used supports, yet they have many disadvantages, such nitrogen. Thin later chromatography (TLC) was done on silica gel
as the presence of distinct impurities, which can act in micropore polygram SILG/UV 254 plates which were used in determining the
construction or poison the catalyst leading to mass-transfer product purity and monitoring the reaction. A Shimadzu GCMS-
restrictions. In addition, the problem of spectroscopic character- QP5050 mass spectrometer was used to record the mass spectra.
istics may result in a lack of basic comprehension. Nano-carbons
are encountered as a promising option in the layout of sup- General approach in the case of the preparation of Ni@Pd NPs
ported catalysts to overcome these problems.23,24 Carbon nano-
tubes (CNTs) have been studied as catalyst supports due to their
Ni@Pd core–shell NPs were synthesized by a high-temperature one-
port solution phase production process, like the consecutive
outstanding characteristics, such as high surface zone, and high
reduction of palladium(II) and nickel(II) into oleylamine (OAm), as
thermal as well as chemical stability.25,26
suggested by Metin et al.37 We combined about 49.7 mg of nickel(II)
acetate tetrahydrate (Ni(ac)2$4H2O, 0.2 mmol) and 53.4 mg of pal-
ladium(II) bromide (PdBr2, 0.2 mmol) with 0.3 mL of TOP and
In this paper, for the nanoscale composition of Ni@Pd NPs,
carbon nanotubes (CNTs) were chosen as supports. Due to the
richness in the level of functional groups and deciencies, the
18.0 mL of OAm at room temperature. Under a ow of mild argon
interest in utilizing CNTs as supports is illustrated for distrib-
(with a 5 ꢀC minꢁ1 rate), the reaction was heated to a temperature
uting metal catalyst nanoparticles. The single electronic struc-
of 245 ꢀC. Expansion of nucleation and related particles was indi-
ture of CNTs shows a signicant charge transfer, which
cated by a gradual change in color from yellow-green to dark brown
that was specied in the production stage. The reaction mixture
was kept at a temperature of 245 ꢀC for 60 min and was later le to
kinetically decreases the diffusion resistance apart from their
accessibility for the active part and appropriate chemical
consistency in aggressive media. In addition, active stages,
cool to room temperature. The NP product was obtained from the
which forcefully interact with CNTs, can lead to structural
reaction mixture by utilizing 40 mL of isopropanol and using
centrifugation at 8500 rpm for 8 min. The nanoparticles were
further rened and later gathered by scattering them in 5 mL of
deciencies in CNTs along with more inuenced over products
and reactant transfer outside or inside CNTs.27–36 Given our
consecutive interest in catalyst expansion for carbonylation
hexane, utilizing an equivalent mixture of isopropanol and ethanol,
reactions and nanocatalysis, Ni@Pd nanoparticles supported
and separating them for 8 min under 8500 rpm. The production
on CNTs were therefore used as a promising catalyst for car-
gathered Ni/Pd core/shell NPs, which had Ni/Pd ¼ 3/2. 62.2 mg of
bonylative Suzuki–Miyaura cross-coupling (refer to Scheme 1).
Ni(ac)2$4H2O (0.25 mmol) and also 53.4 mg of PdBr2 (0.2 mmol)
prepared 49.7 mg of Ni(ac)2$4H2O (yielding 0.2 mmol) and Ni/Pd
(Ni/Pd ¼ 7/3) as well as 80 mg of PdBr2 (0.3 mmol), which led to
Experimental
Materials and methods
the production of Ni/Pd (Ni/Pd ¼ 2/3) for similar reaction states.
Usual approaches for the production of Ni@Pd/CNT NPs
High-purity chemicals were procured from Fluka and Merck.
Electrothermal 9100 apparatus was utilized for the determination
of uncorrected melting points in open capillaries. A VERTEC 70
spectrometer (Bruker) in transmission mode was used for the
A constant amount of CNT (0.40 g) was ultrasonically scattered
in 50 mL of water, and aer that 80 mg of Ni@Pd nanoparticles
was added. Since the mixture was being stirred as well as
ultrasonically scattered for about 120 min, Ni@Pd/CNT was
prepared by utilizing an external magnet. Aer that the mixture
was le to dry in a vacuum.
Common method for synthesis of the carbonylative Suzuki
reaction of aryl iodides
Aryl boronic acid (1.2 mmol), anisole (10 mL), aryl iodide (1.0
mmol), Ni@Pd/CNT MNPs (2 mg), and K2CO3 (3 mmol) were
Scheme 1 Carbonylative Suzuki–Miyaura coupling in the presence of
a catalyst.
27924 | RSC Adv., 2020, 10, 27923–27931
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added to a 100 mL autoclave. The autoclave was sealed, puried 3049, 2979, 2923, 2850, 1645, 1311, 1286, 1082, 850, 781, 705,
twice with CO, pressurized under 1.5 MPa of CO and heated 671; HRMS: m/z calculated for C13H9ClONa+ [M + Na+]:
under reux for 30 min. When the reaction had been per- 239.0251, found: 239.0257.
formed, the reaction compound was cooled to 25 ꢀC and the
Compound 4e. 1H NMR (CDCl3, 400 MHz) d 7.69 (dd, J ¼ 5.2,
residual CO gas was carefully vented. Aer that, the reactor was 3.1 Hz, 2H), 7.54–7.45 (m, 1H), 7.36 (dd, J ¼ 10.5, 4.6 Hz, 2H),
opened. The progress of the reaction was analyzed by taking 7.30 (td, J ¼ 7.4, 1.6 Hz, 1H), 7.24–7.10 (m, 3H), 2.22 (s, 3H) ppm;
advantage of TLC. When the reaction was done, EtOH was 13C NMR (CDCl3, 400 MHz) d 197.54, 137.55, 136.62, 135.63,
released to the reaction compound and the catalyst was 132.09, 129.91, 129.20, 129.02, 127.47, 127.41, 124.14,
removed using an external magnet. In this way, the solvent was 18.94 ppm. IR (KBr) (cmꢁ1): 3064, 2961, 2928, 2850, 1672, 1589,
removed from the solution at a decreased pressure and the nal 1444, 1325, 1264, 931, 766, 700; HRMS: m/z calculated for
product was puried using recrystallization by n-hexane/ethyl
acetate.
C
14H12ONa+ [M + Na+]: 219.0779, found: 219.0786.
Compound 4f. 1H NMR (CDCl3, 400 MHz) d 7.78–7.69 (m,
2H), 7.51–7.42 (m, 1H), 7.41–7.29 (m, 3H), 7.25 (dt, J ¼ 8.5,
4.1 Hz, 1H), 6.99–6.83 (m, 2H), 3.65 (s, 3H) ppm; 13C NMR
(CDCl3, 400 MHz) d 195.51, 156.28, 138.44, 136.76, 131.89,
130.89, 128.76, 128.53, 127.16, 119.46, 110.37, 54.52 ppm. IR
Usual approaches for the production of the carbonylative
Suzuki reaction of aryl iodides
1.0 mmol of aryl iodide, 10 mL of anisole, 3 mmol of K2CO3, (KBr) (cmꢁ1): 3064, 2965, 2932, 2831, 1669, 1589, 1475, 1440,
1.2 mmol of aryl boronic acid, and 2 mg of Ni@Pd/CNT MNPs 1293, 1249, 1021, 925, 760, 694; HRMS: m/z calculated for
were added to a 100 mL autoclave. The autoclave was sealed,
purged twice using carbon monoxide, pressurized under
C
14H12O2Na+ [M + Na+]: 235.0727, found: 235.0733.
Compound 4g. H NMR (CDCl3, 400 MHz) d 7.70–7.59 (m,
1
a pressure of 1.5 MPa with a CO atmosphere and heated under 2H), 7.54 (dt, J ¼ 2.8, 2.1 Hz, 1H), 7.48 (ddd, J ¼ 8.4, 3.9, 1.4 Hz,
reux for 30 min. When the reaction had occurred, the product 3H), 7.34–7.23 (m, 1H), 6.76 (dd, J ¼ 8.4, 1.0 Hz, 1H), 6.68–6.53
of the reaction was cooled to a temperature of 25 ꢀC and the (m, 1H), 6.09 (s, 2H) ppm; 13C NMR (CDCl3, 400 MHz) d 199.15,
residual CO was carefully vented. Then, the reactor was opened. 150.92, 140.08, 134.64, 134.29, 131.03, 129.16, 128.09, 118.12,
The progress of the reaction was analyzed using TLC. When the 116.98, 115.57 ppm. IR (KBr) (cmꢁ1): 3429, 3320, 3049, 2923,
reaction had been performed, EtOH was released to the reaction 2861, 1624, 1557, 1486, 1439, 1315, 1246, 1151, 1020, 936, 752,
compound. Aer that the catalyst was removed by an external 699, 640; HRMS: m/z calculated for C13H11NONa+ [M + Na+]:
magnet, aer it had performed the reaction. In addition, the 220.0721, found: 220.0727.
solvent was separated from the solution at a reduced pressure
and the obtained product was puried using recrystallization by
Results and discussion
adding n-hexane/ethyl acetate.
1
Ni@Pd NPs were derived from the decomposition of PdBr2 over
the surface of Ni NP cores. The Ni core was rstly produced from
Ni(ac)2 as the starting material by adding seeds of Pd to the
reaction admixture at a temperature of 25 ꢀC. Aer that, the
PdBr2 was decomposed and the shell of Pd was formed at
a temperature of 245 ꢀC. The CNT was functionalized with
mercaptopropyl groups in order to produce a Ni@Pd/CNT
nanocatalyst. The Ni@Pd NPs can be simply anchored on the
CNT (see Scheme 2).
Fig. 1a shows the SEM picture of the unutilized Ni@Pd/CNT
catalyst. An extremely tangled rope-like CNT construction is
clear. The TEM picture, as shown in Fig. 1b, suggests that CNT
was properly modied using the Ni@Pd catalyst. The obvious
black spots suggest that the Ni@Pd catalyst was used in the
support and the CNTs were open-ended and relatively short,
which was likely due to acid pre-treatment that was performed
Compound 4a. H NMR (CDCl3, 400 MHz) d 7.80–7.69 (m,
4H), 7.51–7.46 (m, 2H), 7.43–7.32 (m, 4H) ppm; 13C NMR
(CDCl3, 400 MHz) d 196.81, 137.59, 132.45, 130.10, 128.27 ppm.
IR (KBr) (cmꢁ1): 2961, 2923, 2857, 1653, 1585, 1434, 1310, 1273,
1064, 945, 909; HRMS: m/z calculated for C13H10ONa+ [M + Na+]:
205.0619, found: 205.0628.
1
Compound 4b. H NMR (CDCl3, 400 MHz) d 7.74–7.65 (m,
2H), 7.63–7.57 (m, 2H), 7.51–7.40 (m, 2H), 7.38–7.33 (m, 2H),
7.21 (d, J ¼ 7.9 Hz, 2H), 2.33 (s, 3H) ppm; 13C NMR (CDCl3, 400
MHz) d 196.49, 143.28, 137.95, 134.89, 132.16, 130.35, 129.93,
128.99, 128.21, 21.69 ppm. IR (KBr) (cmꢁ1): 3058, 2965, 2922,
2850, 1652, 1583, 1445, 1318, 1273, 939, 768; HRMS: m/z
calculated for
219.0786.
C
14H12ONa+ [M Na+]: 219.0779, found:
+
1
Compound 4c. H NMR (CDCl3, 400 MHz) d 7.90–7.81 (m,
2H), 7.78–7.69 (m, 2H), 7.62–7.53 (m, 1H), 7.54–7.41 (m, 2H),
7.00–6.93 (m, 2H), 3.88 (s, 3H) ppm; 13C NMR (CDCl3, 400 MHz)
d 195.59, 163.25, 138.30, 132.57, 131.94, 130.16, 129.73, 128.23,
113.54, 55.53 ppm. IR (KBr) (cmꢁ1): 3064, 3009, 2954, 2841,
1662, 1589, 1485, 1273, 1122, 1049, 965, 818, 705; HRMS: m/z
calculated for C14H12O2Na+ [M + Na+]: 235.0727, found:
235.0733.
1
Compound 4d. H NMR (CDCl3, 400 MHz) d 7.81–7.69 (m,
4H), 7.64–7.52 (m, 1H), 7.51–7.43 (m, 4H) ppm; 13C NMR
(CDCl3, 400 MHz) d 195.51, 138.89, 137.24, 135.90, 132.62,
131.49, 129.95, 128.64, 128.39 ppm. IR (KBr) (cmꢁ1): 3096, 3064, Scheme 2 Preparation of the Ni@Pd/CNT nanocatalyst.
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Fig. 1 (a) SEM image of Ni@Pd/CNT, and (b) TEM image of Ni@Pd/
CNT.
in providing surface functional groups. Such groups conrmed
that Ni@Pd was added to CNT and also the metal was properly
dispersed. No dark spots were found in the background to
Fig. 1b, suggesting that the metal particles were completely
used up by the support. As can be seen in the TEM and SEM
pictures, in the cases of raw CNTs and metal, full CNTs show
a similar nature.
XRD analysis demonstrated the existence of the mixture of
Ni@Pd/CNT nanocatalyst. As can be observed in Fig. 2, the
broad hump that is located in the range of 2q from 15 to 30ꢀ
indicates the CNT properties. A comparison with the informa-
tion from JCPDS with referral number 65-5788 clearly indicated
the existence of Ni–Pd NPs for more validation. It was found
that NiO and PdO did not exist. The XRD pattern of the Ni@Pd/
CNT nanocatalyst, presented aer the Ni@Pd nanoparticle
correction on CNT, specied the existence of all the feasible
characteristic peaks of Ni@Pd nanoparticles and the peak with
respect to CNT, indicating the rich immobilization of Ni@Pd
nanoparticles onto CNT. In addition, XPS was utilized to study
the chemical elements upon the Ni@Pd/CNT MNP surface.
Fig. 3 shows a full-scan XPS spectrum for the as-prepared
catalyst. Peaks relating to Pd, O, Ni, and C can obviously be
seen.
Fig. 3 XPS spectrum of Ni@Pd/CNT MNPs.
with the magnetization curves of the obtained nanocomposite
registered at 300 K. In Fig. 4, it is shown that no residual
magnetism was detected; thus paramagnetic characteristics
were exhibited by the nanocomposites. Saturation magnetiza-
tion values of 47.4, and 23.6 emu gꢁ1 were determined for
Ni@Pd, and Ni@Pd/CNT MNPs, respectively. Responsivity
towards an external magnetic eld and the ability for quick
redispersion upon the removal of the magnetic eld are char-
acteristic of paramagnetic nanocomposites with high magneti-
zation values. Hence, the resultant nanocomposite exhibited
good magnetic responsivity, suggesting potential applications
for targeting and separation. The EDS pattern was used for the
detection of the chemical composition of Ni@Pd/CNT MNPs.
Fig. 5 shows the peaks related to Ni and Pd indicating the
compositions of Ni@Pd NPs as well as C and O indicating the
compositions of CNT. The copper (Cu) peak in the TEM pattern
is from the Cu grid.
In order to improve the reaction states, the carbonylative
cross-coupling reaction of iodobenzene as well as phenyl
boronic acid in the presence of Ni@Pd/CNT MNPs (a catalyst)
A vibrating sample magnetometer (VSM) was used for the
determination of the magnetic properties of the nanoparticles
Fig. 2 XRD pattern of Ni@Pd/CNT MNPs.
27926 | RSC Adv., 2020, 10, 27923–27931
Fig. 4 Room-temperature magnetization curves of (a) Ni@Pd, and (b)
Ni@Pd/CNT MNPs.
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Table 1 Carbonylative Suzuki–Miyaura reaction by Ni@Pd/CNT MNPs
with different solvents, bases, and timesa
Entry
Solvent
Base
Time (min)
Yieldb (%)
1
2
3
4
5
6
7
8
EtOH
H2O
CH3CN
DMF
CH2Cl2
EtOAc
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
—
CsF
Na2CO3
Et3N
NaOAc
KOH
K3PO4
Cs2CO3
tBuOK
K2CO3
K2CO3
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
30
15
—
—
49
62
35
24
33
60
—
38
45
—
—
—
98
—
—
—
63
—
—
45
73
65
—
98
62
THF
Toluene
n-Hexane
CHCl3
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
DMSO
MeOH
Dioxane
i-PrOH
Anisole
Solvent-free
Anisole
Anisole
Anisole
Anisole
Anisole
Anisole
Anisole
Anisole
Anisole
Anisole
Anisole
Fig. 5 EDS spectra of Ni@Pd/CNT MNPs.
was selected as the procedure. The effect of different factors like
base, time and solvent (refer to Table 1) were tested for the
model reaction. The effect of solvents on the carbonylative
Suzuki coupling reaction was investigated (Table 1, Entries 1–
15). Based on the obtained outcomes of solvents, when polar
protic solvents, like water, ethanol, isopropanol or methanol
were used, no quantity of the desirable product was created.
Nevertheless, the product of the cross-coupling yield was rela-
tively poor in polar aprotic solvents, including EtOAc, DMSO,
DMF, CHCl3, CH2Cl2, and anisole. When the reaction was done
in less polar solvents, such as toluene, appropriately high
amounts of product resulting from carbonylative cross-coupling
were isolated. Anisole was determined to be the most appro-
priate selection. Nevertheless, in polar solvents, the carbon-
ylative cross-coupling product is established in low yield. In the
present paper, it was determined that common heating under
anisole was more efficient in comparison with using organic
solvents (refer to Table 1, Entry 8). It was noted that bases play
a dramatic role in coupling reactions; therefore the reaction was
conducted with the existence of distinct organic and also inor-
ganic bases (refer to Table 1, Entries 16–26). As an outcome, the
most utilized base K2CO3 is a suitable base for generating car-
bonylative cross-coupling yield. Under the optimized states, the
reaction advance for the shortest time essential in the atten-
dance of 3 mg of Ni@Pd/CNT MNPs is detected using GC, that
great products of carbonylative Suzuki coupling reaction may be
obtained data of 30 min (refer to Table 1, Entry 26).
a
Reaction conditions: iodobenzene (1 mmol), phenyl boronic acid (1.2
mmol), Ni@Pd/CNT MNPs (3 mg), K2CO3 (3 mmol), solvent (10 mL), CO
pressure ¼ 3 MPa. b Isolated yields.
reaction was undertaken without a catalyst. While 0.2–1.8 mg of
Ni@Pd/CNT MNPs are weighted on sample reaction, moderate
products of carbonylative Suzuki coupling reaction are estab-
lished. The most appropriate outcome was obtained when the
model reaction was done in the presence of 2 mg of Ni@Pd/CNT
MNPs. An increase in the catalyst value had proved no
enhancement in the reaction model. No outcome was achieved
We investigated the effect of temperature in terms of the
production of the carbonylative Suzuki–Miyaura reaction in the
presence of catalyst Ni@Pd/CNT MNPs. The most appropriate
temperature for the introduced heating of the reaction for reux
led to variations in the efficiency of the reaction. It was
demonstrated that the catalytic activity can be changed by
varying the reaction temperature. The catalyst loading is
considered to be another signicant factor in the common
reaction for carbonylative cross-coupling (refer to Fig. 6). As
indicated in Fig. 6, a low amount of product from the carbon-
ylative Suzuki–Miyaura reaction was obtained when a model
Fig. 6 Effect of increasing the amount of Ni@Pd/CNT MNPs on the
carbonylative Suzuki–Miyaura reaction.
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not simply reusable and recoverable for the next runs. CNT was
utilized to prevent the dispersion of Ni@Pd nanoparticles with
easy separation to solve this issue.
With the improved reaction states, we developed the area of
the carbonylative Suzuki reaction for a diversity of distinct aryl
iodides by phenyl boronic acids. Different electron-donating
and electron-withdrawing groups, such as –NO2, –COCH3,
–CH3, –OCH3, –NH2, –Cl and –Br upon both aryl iodide as well
as aryl boronic acid smoothly tolerate the carbonylative Suzuki
Table 3 Carbonylative Suzuki coupling reaction of various aryl iodides
with arylboronic acid in the presence of the Ni@Pd/CNT MNPsa
Fig. 7 Effect of pressure on the yield of carbonylative Suzuki–Miyaura
reaction.
Entry
Aryl iodide
Product
Yieldb (%)
1
98
with the existence of the catalyst. The inuence of pressurized
CO in the presence of Ni@Pd/CNT MNPs, phenyl boronic acid
and iodobenzene for half an hour is indicated in Fig. 7. The
catalyst compound attained a mean > 98% conversion under
a pressure of 1.5 Mpa. The carbonylative Suzuki–Miyaura reac-
tion was achieved with 98% product and no by-products were
detected using GC in any of the measurements.
2
3
93
92
To further study the performance of the catalyst, various
control measurements were done and the results achieved are
shown in Table 2. In the rst step, a standard reaction was
performed by utilizing CNT and the result indicated that no
value of the desired outcome was produced aer a reaction time
of 30 min (refer to Table 2, Entry 1). Furthermore, when Ni/CNT
was utilized (as the catalyst), no reaction was shown (refer to
Table 2, Entry 2). The Ni cannot admit the middle catalytic
activity at mild reactions. In order to enhance the yield, Pd was
added according to these disappointing outcomes. These
results indicated that the reaction cycle was particularly cata-
lyzed using Pd NPs. It should be noted that, in the reaction
yields, there was no considerable variation when the reaction
was performed with Ni@Pd/CNT, Pd/CNT or a Ni@Pd NPs
catalyst (refer to Table 3, Entries 5–7). The activity of Ni/Pd was
analyzed by changing the ratio of Ni to Pd. The most appro-
priate efficiency was achieved at a ratio of 3 : 2 of Ni to Pd, as
can be observed in Table 2, Entries 3–5. In addition, Ni@Pd was
4
5
6
96
89
87
Table
2 Influence of different catalysts for carbonylative Suzuki
coupling reactiona
Entry
Catalyst
Catalyst loading
Yieldb (%)
7
89
1
2
3
4
CNT
2.0 mg
2.0 mg
2.0 mg
2.0 mg
—
—
98
97
Ni/CNT
Ni@Pd/CNT
Ni@Pd
a
Reaction conditions: aryl iodide (1.0 mmol), phenyl boronic acid (1.0
a
Reaction conditions: iodobenzene (1.0 mmol), phenyl boronic acid mmol), Ni@Pd/CNT MNPs (2.0 mg), K2CO3 (3.0 mmol), solvent (10
(1.0 mmol), K2CO3 (3 mmol), solvent (10 mL), CO pressure 1.5 MPa mL), CO pressure 1.5 MPa aer 30 min. Yield refers to isolated
b
aer 30 min. b Isolated yield.
product.
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Table 4 Comparison of the catalytic efficiency of Ni@Pd/CNT MNPs with various catalystsa
Entry
Catalyst
Experimental conditions
Yield (%)
Ref.
1
2
3
4
5
6
7
Pd/C
100 ꢀC, 8 h, 4 bar CO
120 ꢀC, 12 h, 30 bar CO
80 ꢀC, 8 h, 1 bar CO
100 ꢀC, 10 h, 7 bar CO
80 ꢀC, 9 h, 1 bar CO
80 ꢀC, 8 h, 1 bar CO
Reux, 0.5 h, 1.5 bar CO
90
86
91
94
94
91
98
38
39
40
41
42
43
P(DVB-NDIIL)-Pd
Fe3O4@SiO2-2N-Pd
PS-Pd-NHC
HMMS-SH-Pd
MCM-41-2N-Pd
Ni@Pd/CNT
This work
a
Reaction conditions: iodobenzene (1.0 mmol), phenylboronic acid (1.0 mmol), with different temperatures, times, and pressures of CO.
coupling reaction, presenting desirable outcomes with appre-
ciable products, as determined in Table 3. Iodobenzene reacted
with phenyl boronic acid, presenting a 98% product of benzo-
phenone (refer to Table 3, Entry 1). It is important to note that
aryl iodides, including electron-withdrawing groups, like –Br,
–COCH3, and –Cl are determined to be more active compared to
aryl iodides including electron-donating groups, like –CH3,
–OCH3 and –NH2.
In this paper, the catalytic efficiency of the suggested catalyst
compared with catalysts related to the carbonylative Suzuki
coupling reaction was investigated (refer to Table 4). Table 4
obviously displays that the most desirable parameters are
needed in the case of the carbonylative Suzuki coupling reac-
tion, utilizing Ni@Pd/CNT MNPs, when a suitable, excellent,
efficiency of the available catalyst is considered for the reaction.
In the catalyst, the values of Pd achieved aer and before the
reaction were about 2.6% and 2.7%, as detected by ICP-MS. Aer
accomplishing the reaction, as observed in Table 5, this indicated
that most of the Pd species leaching in solution were retaken on
the CNT bers. The most considerable characteristics of a catalyst
involve determining the stability as well as activity of a nano-
catalyst upon being recycled. However, recycling experiments were
done by taking into account the ten different periods under mild
conditions. The catalyst was recovered from the reaction solution
and aer that it was cleaned with DI water (deionized water) and
dried at a temperature of 80 ꢀC. Then, for the next period, the
carbonylative Suzuki coupling reaction was tested, and the residual
concentration was analyzed singly aer each period. The catalyst
activity experienced a 4% decrease aer accomplishing ten
implementations. Aer ten implementations, we observed that the
catalyst had undergone deactivation, as observed in Fig. 8. The
result displays the reusability of this heterogeneous approach.
Moreover, a complete investigation was undertaken to
specify the heterogeneous nature of the catalyst. In the rst
step, a hot ltration experiment was performed on the
Fig. 8 Reuse performance of the catalysts.
carbonylative Suzuki–Miyaura reaction under mild conditions
and it was found that about 62% of the catalyst was removed
magnetically in situ aer 15 min of removal. Moreover, the
reactants were able to tolerate more reactions. The results
indicated that the remainder of the free catalyst was feebly
active, aer removing the heterogeneous catalyst, and
a conversion of 64% was achieved aer 30 min of the Suzuki–
Miyaura reaction. We had proved that the catalyst acted
heterogeneously in the reaction and there was only slight
leaching during the reaction. In the second step, to ensure the
heterogeneous type of catalyst, mercury poisoning analysis was
Table 5 The loading amount of Ni@Pd in Ni@Pd/CNT MNPs
Entry
Catalyst
wt%
1
2
Ni@Pd/CNT MNPs
Ni@Pd/CNT MNPs aer ten reuses
6.1
5.9
Fig. 9 Reaction kinetics, Hg(0) poisoning, and hot filtration studies for
the carbonylative Suzuki–Miyaura reaction.
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further undertaken. Mercury(0) was introduced as a metal or by reaction. The reaction area was stirred for more than 30 min
synthesis and it considerably deactivated the metal catalyst over and also, since the catalyst was poisoned, no more conversion
the active surface. Therefore, it can neutralize the catalyst was observed aer 30 min. A kinetic approach to the reaction
activity. Our experiments proved that the catalyst is homoge- with the existence of Hg(0) is proved in Fig. 9. The negative
neous. This analysis was done by the above-mentioned reaction results achieved from all the heterogeneity experiments (Hg(0)
model under optimized conditions. Around 300 moles mercury hot ltration along with poisoning) suggested that the solid
were released into the reaction compound aer 15 min of catalyst was particularly heterogeneous and there was no Pd
leaching obtained over the carbonylative Suzuki–Miyaura
reaction.
Eventually, to ensure the recovered catalyst structure was
maintained for the carbonylative Suzuki coupling reaction, we
investigated it aer the 10th passage in the determined
premium states, as observed in Fig. 10. The EDX pattern of the
resynthesized catalyst determined the presence of the attendant
parameters, so vouching for the catalyst's consistency in the
reactions, as can be seen in Fig. 10a. As can be observed in
Fig. 10b, the XRD pattern of the reproduced catalyst demon-
strated that the catalyst structure remained completely intact
aer recycling. The XPS pattern demonstrated that the Pd and
Ni elements shown in the catalyst were retained entirely aer
the passage of the 10th run when their oxidation condition was
the same as in the fresh catalyst. As can be seen in Fig. 10c and
d, no other oxidation states were specied for the catalyst. The
TEM picture demonstrated that the generic gray and white dots
placed over the straight chain of CNT aer the 10th run are
Ni@Pd (refer to Fig. 10e). Note that no morphological changes
in the nanocatalyst were indicated in the FE-SEM pictures,
which were captured from the recovered catalyst (refer to
Fig. 10f).
Conclusions
In the present paper, a new class of functionalized CNTs was
produced for selectively including Ni@Pd, that exhibited great
catalytic activity for the carbonylative Suzuki coupling reaction
with good products. EDS, TEM, VSM, SEM and XRD analyses
suggested the functionalization of Ni@Pd on the CNT. More-
over, the catalyst was quickly retrievable and reusable. A
rational plan for single-site catalysts with total usage of each
Ni@Pd active zone and also great recyclability and insignicant
catalyst leaching can coincide with the requirements of green
chemistry. Therefore, the investigation of the Ni@Pd/CNT
nanocatalyst can suggest a possible platform for the construc-
tion of other nanocatalysts with easy availability that could be
highly impressive for different catalytic reactions. This method
can be expanded in the future for further nanocatalysts, which
have desirable characteristics, like performance and ease of
reuse.
Conflicts of interest
There are no conicts to declare.
Acknowledgements
Fig. 10 (a) EDX, (b) VSM, (c) XRD, (d) XPS spectra of Ni, (e) XPS spectra
The authors appreciate the support of the National Key R&D
of Pd, (f) TEM, and (g) FE-SEM images of the recovered Ni@Pd/CNT
MNPs after the 10th run for the carbonylative Suzuki–Miyaura reaction. Program of China (2017YFE0116300); the Key Research
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Programs of Henan Educational Committee (19A610011); the 22 E. Auer, A. Freund, J. Pietsch and T. Tacke, Appl. Catal., A,
National Natural Science Foundation of China (51878646); and 1998, 173, 259–271.
the Natural Science Foundation of Henan Province 23 D. S. Su, S. Perathoner and G. Centi, Chem. Rev., 2013, 113,
(182300410102).
5782–5816.
24 A. Schaetz, M. Zeltner and W. J. Stark, ACS Catal., 2012, 2,
1267–1284.
25 D. Vairavapandian, P. Vichchulada and M. D. Lay, Anal.
Chim. Acta, 2008, 626, 119–129.
26 Y. Yan, J. Miao, Z. Yang, F.-X. Xiao, H. B. Yang, B. Liu and
Y. Yang, Chem. Soc. Rev., 2015, 44, 3295–3346.
27 J. Zhang, C. Xu, D. Zhang, J. Zhao, S. Zheng, H. Su, F. Wei,
B. Yuan and C. Fernandez, J. Electrochem. Soc., 2017, 164,
B92–B96.
Notes and references
1 M. Garcia-Melchor, M. C. Pacheco, C. Najera, A. Lledos and
G. Ujaque, ACS Catal., 2012, 2, 135–144.
2 A. L. Isfahani, I. Mohammadpoor-Baltork, V. Mirkhani,
A. R. Khosropour, M. Moghadam, S. Tangestaninejad and
R. Kia, Adv. Synth. Catal., 2013, 355, 957–972.
3 Y. P. Shang, X. M. Jie, J. Zhou, P. Hu, S. J. Huang and
W. P. Su, Angew. Chem., Int. Ed., 2013, 52, 1299–1303.
4 H. Kamisaki, T. Nanjo, C. Tsukano and Y. Takemoto, Chem.–
Eur. J., 2011, 17, 626–633.
5 H. Li and J. J. Cooper-White, Nanoscale, 2013, 5, 2915–2920.
6 M. Cobo, A. Orrego and J. A. Conesa, Appl. Catal., A, 2012,
445, 83–91.
7 W. Hu, B. Liu, Q. Wang, Y. Liu, Y. Liu, P. Jing, S. Yu, L. Liu
and J. Zhang, Chem. Commun., 2013, 49, 7596–7598.
8 J.-H. Park, S.-K. Kim, H. S. Kim, Y. J. Cho, J. Park, K. E. Lee,
C. W. Yoon, S. W. Nam and S. O. Kang, Chem. Commun.,
2013, 49, 10832–10834.
9 S. Wang, W. C. Li, G. P. Hao, Y. Hao, Q. Sun, X. Q. Zhang and
A. H. Lu, J. Am. Chem. Soc., 2011, 133, 15304–15307.
10 O. Metin, S. F. Ho, C. Alp, H. Can, M. N. Mankin,
M. S. Gultekin, M. Chi and S. Sun, Nano Res., 2013, 6, 10–18.
11 S. M. Sadeghzadeh, R. Zhiani and S. Emrani, RSC Adv., 2017,
7, 24885–24894.
28 B. Singh, L. Murad, F. Laffir, C. Dickinson and E. Dempsey,
Nanoscale, 2011, 3, 3334–3349.
29 S. S. Munjewar, S. B. Thombre and R. K. Mallick, Renewable
Sustainable Energy Rev., 2017, 67, 1087–1104.
30 A. M. Al-Enizi, A. A. Elzatahry, A. M. Abdullah, A. Vinu,
H. Iwai and S. S. Al-Deyab, Appl. Surf. Sci., 2017, 401, 306–
313.
31 Y. Mu, H. Liang, J. Hu, L. Jiang and L. Wan, J. Phys. Chem. B,
2005, 109, 22212–22216.
32 C.-K. Cheng, T.-K. Yeh, M.-C. Tsai, H.-Y. Chou, H.-C. Wu and
C.-K. Hsieh, Surf. Coat. Technol., 2017, 320, 536–541.
33 J. Tang, D. Chen, C. Li, X. Yang, H. Liu and J. Yang, RSC Adv.,
2017, 7, 3455–3460.
34 G. Wu and B.-Q. Xu, J. Power Sources, 2007, 174, 148–158.
35 R. Nie, J. Wang, L. Wang, Y. Qin, P. Chen and Z. Hou,
Carbon, 2012, 50, 586–596.
36 S. H. Chae, Y. Jin, T. S. Kim, D. S. Chung, H. Na, H. Nam,
H. Kim, D. J. Perello, H. Y. Jeong, T. H. Ly and Y. H. Lee,
ACS Nano, 2016, 10, 1309–1316.
12 M. Li, X. Chen, J. Guan, X. Wang, J. Wang, C. T. Williams and
C. Liang, J. Mater. Chem., 2012, 22, 609–616.
13 S. M. Sadeghzadeh, R. Zhiani and S. Emrani, Appl.
Organomet. Chem., 2018, 32, e3941.
14 H. Bae, V. Burungale, J. B. Park, S. W. Bang, H. Rho,
S. H. Kang, S. W. Ryu and J. S. Ha, Appl. Surf. Sci., 2020,
510, 145389.
15 T. C. Lin and B. R. Huang, Sens. Actuators, B, 2012, 162, 108–
113.
16 A. Chaichi, S. K. Sadrnezhaad and M. Malekjafarian, Int. J.
Hydrogen Energy, 2018, 43, 1319–1336.
37 O. Metin, S. F. Ho, C. Alp, H. Can, M. N. Mankin,
M. S. Gultekin, M. Chi and S. Sun, Nano Res., 2013, 6, 10–18.
38 M. V. Khedkar, P. J. Tambade, Z. S. Qureshi and
B. M. Bhanage, Eur. J. Org. Chem., 2010, 6981–6986.
39 N. Jiao, Z. Li, Y. Wang, J. Liu and C. Xia, RSC Adv., 2015, 5,
26913–26922.
40 X. Sun, Y. Zheng, L. Sun, Q. Lin, H. Su and C. Qi, Nano-Struct.
Nano-Objects, 2016, 5, 7–14.
41 M. Deshmukh, P. J. Tambade and B. M. Bhanage, Synthesis,
2011, 2, 243–250.
17 P. H. Gore, Chem. Rev., 1955, 55, 229–281.
18 J.-J. Brunet and R. Chauvin, Chem. Soc. Rev., 1995, 24, 89–95.
42 J. Niu, M. Liu, P. Wang, Y. Long, M. Xie, R. Li and J. Ma, New
J. Chem., 2014, 38, 1471–1476.
´
´
19 V. Calvino-Casilda, A. J. Lopez-Peinado, C. J. Duran-Valle and
´
R. M. Martın-Aranda, Catal. Rev., 2010, 52, 325–380.
43 M. Cai, J. Peng, W. Hao and G. Ding, Green Chem., 2011, 13,
190–196.
20 S. M. Sadeghzadeh, RSC Adv., 2015, 5, 68947–68952.
21 S. M. Sadeghzadeh, RSC Adv., 2015, 5, 17319–17324.
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