A highly stable and efficient magnetically recoverable and reusable Pd nanocatalyst in aqueous media heterogeneously catalysed Suzuki C-C cross-coupling reactions

Article abstract of DOI:10.1002/aoc.3282

Surface modification of Fe₃O₄ nanoparticles with triethoxyethylcyanide groups was used for the immobilization of palladium nanoparticles to produce Fe₃O₄/Ethyl-CN/Pd. The catalyst was characterized using Fourier transform infrared, wavelength-dispersive X-ray, energy-dispersive X-ray and X-ray photoelectron spectroscopies, field-emission scanning electron and transmission electron microscopies, and X-ray diffraction, vibrating sample magnetometry and inductively coupled plasma analyses. In this fabrication, cyano groups played an important role as a capping agent. The catalytic behaviour of Fe₃O₄/Ethyl-CN/Pd nanoparticles was measured in the Suzuki cross-coupling reaction of various aryl halides (Ar-I, Ar-Br, Ar-Cl) with phenylboronic acid in aqueous phase at room temperature. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture by applying an external magnet device and recycled seven times without any significant loss in activity.

Full text of DOI:10.1002/aoc.3282

Full Paper
Received: 13 December 2014
Revised: 26 December 2014
Accepted: 29 December 2014
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/aoc.3282
A highly stable and efficient magnetically
recoverable and reusable Pd nanocatalyst in
aqueous media heterogeneously catalysed
Suzuki C–C cross-coupling reactions
Bahareh Abbas Khakiania, Khalil Pourshamsiana and Hojat Veisib*
Surface modification of Fe3O4 nanoparticles with triethoxyethylcyanide groups was used for the immobilization of palladium
nanoparticles to produce Fe3O4/Ethyl-CN/Pd. The catalyst was characterized using Fourier transform infrared, wavelength-
dispersive X-ray, energy-dispersive X-ray and X-ray photoelectron spectroscopies, field-emission scanning electron and transmis-
sion electron microscopies, and X-ray diffraction, vibrating sample magnetometry and inductively coupled plasma analyses. In
this fabrication, cyano groups played an important role as a capping agent. The catalytic behaviour of Fe3O4/Ethyl-CN/Pd nano-
particles was measured in the Suzuki cross-coupling reaction of various aryl halides (Ar–I, Ar–Br, Ar–Cl) with phenylboronic acid
in aqueous phase at room temperature. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction
mixture by applying an external magnet device and recycled seven times without any significant loss in activity. Copyright © 2015
John Wiley & Sons, Ltd.
Keywords: immobilized palladium catalyst; magnetic nanoparticles; heterogeneous catalyst; recyclable; Suzuki reaction
As a consequence, nanoparticles can have higher catalyst loading
capacity and higher dispersion than many conventional support
Introduction
The Suzuki reaction is one of the most versatile and utilized reac-
tions for the selective construction of carbon–carbon bonds,[1–4]
in particular for the construction of biaryls,[4–7] since these have a
diverse spectrum of applications,[8] ranging from pharmaceuti-
cals to materials science. Therefore, the development of easily
available or prepared, inexpensive catalysts, and environmen-
tally benign solvents and methodology avoiding the use of ex-
pensive and toxic ligands remain a highly desirable goal.
Recently, various catalytic systems have been reported for
Suzuki coupling reactions.[9,10]
Development of this reaction is greatly dependent on the reac-
tivity of the palladium catalyst. Generally, catalysts are divided into
two groups: most examples are homogeneous systems and the
others are heterogeneous systems. Despite the observed beneficial
effects with homogeneous catalysts, problems associated with the
separation and recovery of the expensive active catalyst limit their
use in industrial and synthetic applications. In light of this, continu-
ing efforts are now being made to carry out the reactions with het-
erogeneous systems to aid recovery, recyclability and re-use of the
catalyst. Immobilization of homogeneous catalysts on various insol-
uble supports (especially porous materials with high surface areas)
can lead to simple catalyst recycling via filtration or centrifugation.
However, a substantial decrease in the activity of the immobilized
catalyst is frequently observed due to the loss of the catalyst in
the separation processes and/or to diffusion factors. In an attempt
to resolve such problems, nanoparticles have been used as alterna-
tive soluble matrixes for supporting homogeneous catalysts. When
the size of the support materials is decreased to the nanometre
scale, the surface area of nanoparticles will increase dramatically.
matrixes, leading to the improved catalytic activity of the supported
catalysts. However, conventional separation methods may become
inefficient for support particle sizes below 100 nm. The incorpora-
tion of magnetic nanoparticles (MNPs) into supports offers a solu-
tion to this problem. The renewed interest in synthesis of MNPs is
due to their technological applications such as data storage, biolog-
ical imaging and biomedicine.[11–15] One of the attractive features
of MNPs is the possibility of fast and cost-efficient separation by ap-
plying an external magnetic field, which makes them ideal candi-
dates for practical use in catalysis processes. This new direction in
catalysis has galvanized academic research and led to the
development of a great number of magnetic-based catalysts, espe-
cially magnetite (Fe3O4) that has found application in various
reactions.[16–25] Several accounts of the synthesis, characterization
and application of Fe3O4 MNPs utilized in coupling reactions have
been reported in the literature.[26–37]
It should be noted that magnetostatic interactions between
particles make Fe3O4 particles susceptible to agglomeration. On
the other hand, the oxidation of Fe2+ causes depletion of the
magnetism of Fe3O4. Thus, in order to decrease the degree of
*
Correspondence to: Hojat Veisi, Department of Chemistry, Payame Noor
University, Tehran, Iran. E-mail: hojatveisi@yahoo.com
a Department of Chemistry, Tonekabon Branch, Islamic Azad University,
Tonekabon, Iran
b Department of Chemistry, Payame Noor University, Tehran, Iran
Appl. Organometal. Chem. (2015)
Copyright © 2015 John Wiley & Sons, Ltd.

B. Abbas Khakiani et al.
agglomeration and increase the oxidation resistance, effective coat-
ing of magnetite particles is essential.
In this context, we considered that Fe3O4 supporting ethyl cya-
nide groups (Fe3O4/Ethyl-CN) would serve as an efficient and robust
support material for metal ions. Our interest in this area[38–43] has
prompted us to explore the immobilization of PdCl2 on the surface
of Fe3O4/Ethyl-CN. Here, we report a convenient procedure for syn-
thesizing a recoverable Fe3O4/Ethyl-CN/Pd nanocatalyst for the
Suzuki coupling reaction in a green medium (H2O–EtOH). More im-
portantly, the synthesized Fe3O4/Ethyl-CN/Pd nanocomposite has
good magnetic property, and can be easily separated from the re-
action mixture using a magnet. By utilizing this property, it can be
reused for seven cycles without loss of catalytic activity, indicative
of potential application in industry.
Scheme 1. Preparation of Fe3O4/Ethyl-CN/Pd nanocatalyst.
spectroscopy (ICP-AES) and energy dispersive X-ray spectroscopy
(EDS).
Experimental
Preparation of Fe3O4 MNPs
Suzuki–Miyaura Coupling Reaction
Naked Fe3O4 nanoparticles were prepared by chemical co-
precipitation of Fe3+ and Fe2+ ions with a molar ratio of 2:1. Typi-
cally, FeCl3Á6H2O (5.838 g, 0.0216 mol) and FeCl2Á4H2O (2.147 g,
0.0108 mol) were dissolved in 100 ml of deionized water at 85°C un-
der nitrogen atmosphere and with vigorous mechanical stirring
(500 rpm). Then, 10 ml of 25% NH4OH was quickly injected into
the reaction mixture in one portion. The addition of the base to
the Fe2+/Fe3+ salt solution resulted in the immediate formation of
a black precipitate of MNPs. The reaction continued for another
25 min and the mixture was cooled to room temperature.
Subsequently, the resultant ultrafine magnetic particles were
treated by magnetic separation and washed several times with de-
ionized water.
In a typical reaction, 7 mg of Fe3O4/Ethyl-CN/Pd (0.0021 mmol Pd)
was placed in a 25 ml Schlenk tube, to which was added 1 mmol
of aryl halide in 5 ml of water–ethanol (1:1), 0.134 g (1.1 mmol) of
phenylboronic acid and 0.276 mg (2 mmol) of K2CO3. The mixture
was then stirred for the desired time at 20–25°C. The reaction was
monitored using TLC. After completion of the reaction, 5 ml of eth-
anol was added, and the catalyst was removed using an external
magnet. Further purification was achieved with column
chromatography.
Results and Discussion
Fe3O4/Ethyl-CN/Pd was prepared using the concise route outlined
in Scheme 1. Naked Fe3O4 MNPs were prepared through a chemical
co-precipitation method, and subsequently coated with 2-
cyanoethyltriethoxysilane to achieve cyanoethyl-functionalized
MNPs. Ultimately, the reaction of cyano groups with PdCl2 and sub-
sequent its reduction led to the corresponding Pd nanoparticles
supported on MNPs. Finally, the mixture was collected using an ex-
ternal magnet, followed by drying in vacuum. The Pd content in
Fe3O4/Ethyl-CN/Pd catalyst was determined as 2.75 wt% (0.27 mmol
Preparation of Fe3O4/Ethyl-CN
The obtained MNP powder (500 mg) was dispersed in 50 ml of tol-
uene solution by sonication for 20 min, and then triethoxyethyl-
cyanide (3 mmol) was added to the mixture. The mixture was
refluxed under argon atmosphere at 100°C for 48 h. The product
was separated by filtration, washed with ethanol and dried under
vacuum for 24 h at 50°C. The precipitated product (Fe3O4/Ethyl-
CN) was dried at room temperature under vacuum.
Preparation of Fe3O4/Ethyl-CN/Pd(0)
Fe3O4/Ethyl-CN (500 mg) was dispersed in CH3CN (30 ml) in an ul-
trasonic bath for 30 min. Subsequently, a yellow solution of PdCl2
(30 mg) in 30 ml of CH3CN was added to the dispersion of Fe3O4/
Ethyl-CN and the mixture was stirred for 10 h at 20–25°C. Then,
the Fe3O4/Ethyl-CN/Pd(II) thus obtained was separated using
magnetic decantation and washed with CH3CN, water and acetone
successively to remove the unattached substrates.
The reduction of Fe3O4/Ethyl-CN/Pd(II) using hydrazine hydrate
was performed as follows. Fe3O4/Ethyl-CN/Pd(II) (50 mg) was dis-
persed in 60 ml of water, and then 100 μl of hydrazine hydrate
(80%) was added. The pH of the mixture was adjusted to 10 with
25% ammonium hydroxide and the reaction was carried out at
95°C for 2 h. The final product, Fe3O4/Ethyl-CN/Pd(0), was washed
with water and dried in vacuum at 40°C. Scheme 1 depicts the syn-
thetic procedure for Fe3O4/Ethyl-CN/Pd. The concentration of palla-
dium in Fe3O4/Ethyl-CN/Pd was 2.75 wt% (0.27 mmol gÀ1), which
was determined using inductively coupled plasma atomic emission
Figure 1. FT-IR spectra of (a) Fe3O4, (b) Fe3O4/Ethyl-CN and (c) Fe3O4/Ethyl-
CN/Pd.
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Appl. Organometal. Chem. (2015)

Magnetically recoverable and reusable Pd nanocatalyst
the surface of the modified Fe3O4 nanoparticles with ethyl cyanide
groups as organic shell. In the TEM images, iron oxide nanoparticles
of 15–20 nm in diameter and palladium nanoparticles of ca 3 nm
entrapped in iron oxide are observed. As shown in Fig. 3, aggrega-
tion of individual nanoparticles occurs. Such aggregations cause
the difference between particle sizes derived from TEM analysis.
The presence of Pd atoms in Fe3O4/Ethyl-CN/Pd is also confirmed
using EDS, recorded at random points on the surface for qualitative
analysis (Fig. 4). The EDS spectrum also shows signals of iron, silicon
and oxygen atoms, which also indicate their presence in the composite.
Figure 5 shows FESEM images of the synthesized Fe3O4/Ethyl-
CN/Pd loaded magnetite nanoparticles. It is confirmed that the cat-
alyst is made up of uniform nanometre-sized particles.
In combination with SEM, WDX can provide qualitative informa-
tion about the distribution of various chemical elements in the
catalyst matrix. Figure 6 collects representative SEM and corre-
sponding elemental map (WDX) images for the synthesized cata-
lyst. It can be seen that the particles are not fully spherical. In
Figure 2. XRD patterns of (a) Fe3O4 and (b) Fe3O4/Ethyl-CN/Pd.
g
À1) using ICP-AES. The characterization of the catalyst was carried
out using Fourier transform infrared (FT-IR) spectroscopy,
wavelength-dispersive X-ray spectroscopy (WDX), EDS, X-ray photo-
electron spectroscopy (XPS), X-ray diffraction (XRD), field-emission
scanning electron microscopy (FESEM), transmission electron mi-
croscopy (TEM), ICP and vibrating sample magnetometry (VSM).
Figure 1 shows the FT-IR spectra for MNPs, MNPs/Ethyl-CN and
MNPs/Ethyl-CN/Pd. The FT-IR spectrum for the MNPs alone shows
a stretching vibration at 3381 cmÀ1 which incorporates contribu-
tions from both symmetric and asymmetric modes of the O–H
bonds which are attached to the surface iron atoms.[44] The bands
at low wavenumbers (≤700 cmÀ1) come from vibrations of Fe–O
bonds of iron oxide, which for bulk Fe3O4 samples appear at 570
and 375 cmÀ1, but for Fe3O4 nanoparticles are blue-shifted to 624
and 572 cmÀ1 due to the size reduction.[45–47] The presence of an
adsorbed water layer is confirmed by a stretching vibrational mode
of water at 1622 cmÀ1. The FT-IR spectra of MNPs/Ethyl-CN and
MNPs/Ethyl-CN/Pd show Fe–O vibrations in the same vicinity. The
introduction of cyano groups to the surface of MNPs is confirmed
by the bands at 1009, 2245 and 2952 cmÀ1 assigned to Fe–O–Si,
CN and C–H stretching vibrations, respectively. The cyanide signal
appearing at 2245 cmÀ1 in Fig. 1(b) for the metal–ligand co-
ordination[48] presumably leads to a shift of this peak to lower fre-
quency. This shift can be observed comparing Fig. 1(c). This peak
in Figs. 1(b) and (c) indicates the successful attachment of
ethylcyanides organic ligands and subsequent coordination of Pd
nanoparticles within the hybrid material.
The high-angle XRD patterns of Fe3O4 nanoparticles and Fe3O4/
Ethyl-CN/Pd are shown in Fig. 2. It can be seen that the strong char-
acteristic diffraction peaks at 2θ of 30.09°, 35.44°, 43.07°, 53.43°,
56.96° and 62.55° corresponding to the diffraction of (220), (311),
(400), (422), (511) and (440) of Fe3O4 (JCPDS 89–3854) appear for
both samples. This result means that the catalyst has been synthe-
sized successfully without damaging the crystal structure of the
Fe3O4 core. The broad peak at 2θ of 17–25° in Fig. 2(b) is assigned
to the amorphous silica shell on the surface of the MNPs. Moreover,
apart from the original peaks, new peaks at 2θ of 39.4°, 47.2° and
67.9°, corresponding to (111), (200) and (220) crystalline planes
of Pd, are observed in the spectrum, indicating that Pd exists in
the form of Pd(0), not Pd(II). The broad nature of the diffraction
peak clearly indicates the Pd composition is composed of small
nanocrystals, which agrees well with the TEM analysis.
Figure 3. TEM image of Fe3O4/Ethyl-CN/Pd.
TEM imaging of the Fe3O4/Ethyl-CN/Pd catalyst reveals that Pd
nanoparticles with nearly spherical morphology are formed on
Figure 4. EDS spectrum of the catalyst.
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B. Abbas Khakiani et al.
WDX analysis reveals that Pd metal particles are well dispersed in
the catalyst, which agrees well with the XRD analysis.
XPS is a powerful tool for investigating the electron properties of
species formed on surfaces, such as the electron environment, oxi-
dation state and the binding energy of the core electrons of a
metal. Figure 7 shows the XPS spectra of Fe3O4/Ethyl-CN/Pd
(recorded with a Shimadzu ESCA-3400 electron spectrometer).
The XPS spectrum of Fe 2p contains two peaks, strong peaks lo-
cated at 712.5 and 726.8 eV, which are the typical Fe 2p1/2 and Fe
2p3/2 XPS signals of magnetite.[49] Moreover, investigation of
Fe3O4/Ethyl-CN/Pd at the Pd 3p level shows peaks at 532.6 and
553.8 eV for Pd 3p3/2 and Pd 3p1/2, respectively, which clearly indi-
cates that the Pd nanoparticles are stable as metallic state in the
nanocomposite structure (Fig. 7). In comparison to the standard
binding energy of Pd0, with Pd 3p3/2 of about 532.4 eV and Pd
3p1/2 of about 560.2 eV,[50] it can be concluded that the Pd peaks
in Fe3O4/Ethyl-CN/Pd shift to lower binding energy than Pd0 stan-
dard binding energy. It has been reported that the position of the
Pd 3p peak is usually influenced by the local chemical/physical en-
vironment around Pd species besides the formal oxidation state,
and shifts to lower binding energy when the charge density
increases.[51] Therefore, the peaks at 553.8 and 532.6 eV could be
due to Pd0 species bound directly to amino groups in Fe3O4/
Ethyl-CN, which is in agreement with FT-IR results. The characteristic
peaks corresponding to carbon (C 1s), nitrogen (N 1s) and oxygen
(O 2s) are also clearly observed in XPS elemental surveys of
Fe3O4/Ethyl-CN/Pd.
The magnetic properties of Fe3O4, Fe3O4/Ethyl-CN and Fe3O4/
Ethyl-CN/Pd were characterized using VSM. The saturation magne-
tization of Fe3O4 nanoparticles at room temperature by measuring
the magnetization curve (Fig. 8) is 62.1 emu gÀ1; however, its minor
decrease to 61.7 emu gÀ1 further suggests the formation of an ethyl
cyanide coating on the surface of Fe3O4 nanoparticles. The Ms value
Figure 5. FESEM images of Fe3O4/Ethyl-CN/Pd.
addition, some particle aggregations are observed, which is likely to
be caused by the magnetostatic interactions between particles.
Figure 6. SEM image of Fe3O4/Ethyl-CN/Pd and elemental maps of Fe, Si, O, C and Pd atoms of Fe3O4/Ethyl-CN/Pd.
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Magnetically recoverable and reusable Pd nanocatalyst
Figure 7. XPS spectra of Fe3O4/Ethyl-CN/Pd catalyst for Pd 3p, Fe 2p, C 1s, N 1s and O 2s.
Scheme 2. Fe3O4/Ethyl-CN/Pd for Suzuki cross-coupling reaction.
amounts of catalyst were screened in order to establish ideal cou-
pling conditions (Table 1). Among the bases evaluated, K2CO3 is
found to be the most effective. H2O–EtOH (1:1) is the best choice
as solvent. The effect of catalyst loading was investigated
employing various quantities of the catalyst ranging from 0.1 to
0.3 mol% (Table 1, entries 5, 8, 9). The best result is obtained with
0.007 g (0.2 mol%) of the catalyst (Table 1, entry 5).
Figure 8. Room temperature magnetization curves of Fe3O4, Fe3O4/Ethyl-
CN and Fe3O4/Ethyl-CN/Pd.
of Fe3O4/Ethyl-CN/Pd is much decreased due to the Pd coating and
the immobilization of Fe3O4/Ethyl-CN (55.3 emu gÀ1). As a result,
the modified MNPs have a typical superparamagnetic behaviour
and can be efficiently attracted with a small magnet.
Fe3O4/Ethyl-CN/Pd was tested as a palladium magnetically sepa-
rable heterogeneous nanocatalyst for the Suzuki–Miyaura coupling
reaction in aqueous media under ligand-free conditions (Scheme 2).
We initially selected bromobenzene and phenylboronic acid as a
model reaction at room temperature. Various solvents, bases and
To investigate the generality of this cross-coupling reaction, we
studied the reaction of phenylboronic acid with a range of aryl ha-
lides (I, Br, Cl) under the optimized conditions (Table 2). Under the
optimized conditions, phenyl iodides, bromides and chlorides all re-
act efficiently with phenylboronic acid (Table 2, entries 1–6). Aryl
halides with electron-withdrawing or electron-releasing groups re-
act with phenylboronic acid to afford the corresponding products
in high yields. It is found that the yield when using an ortho-
substituted aryl bromide is lower (Table 2, entry 12) than when
Appl. Organometal. Chem. (2015)
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B. Abbas Khakiani et al.
Table 1. Optimization of conditions for the Suzuki–Miyaura reaction of
external magnet and the reaction was continued with the filtrate
for an additional 40 min. In the second experiment, the reaction
was terminated after 20 min. In both cases, the desired product is
obtained in the same yield (40%). The result of the magnetic sepa-
ration experiment confirms the heterogeneous nature of the
catalyst.
bromobenzene with phenylboronic acida
Entry
Solvent
Pd (mol%)
Base
Time (min) Yield (%)b
1
2
3
4
5
6
7
8
9
10
DMF
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.3
0.2
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
NaOAc
Et3N
80
60
60
90
40
60
90
60
60
90
82
60
Toluene
So, based on these evidences and the literature,[52] a reaction
mechanism for Suzuki coupling with the prepared nanocatalyst is
proposed in Scheme 3. Some of the Pd(0) species bound to the sup-
port undergoes oxidative addition with the aryl halide and is re-
leased to the solution, but some still remains on the surface. After
the reductive elimination step the Pd(0) is recaptured by free cya-
nide groups on the surface of the support and can start a new cat-
alytic cycle. We speculate these simultaneous mechanisms are
possible.
A schematic representation of the proposed catalytic route for
the Suzuki reaction is presented in Scheme 3. Firstly, the aryl halide
reacts with the active palladium catalyst (oxidative addition) to pro-
duce Pd(II) intermediate (II). Then the aryl moiety of phenylboronic
acid exchanges with halide on the surface of the catalyst (III), and
finally III undergoes reductive elimination to produce the expected
product.
In view of industrial purposes and green chemistry, reusability of
the catalyst was tested by carrying out repeated runs of the reac-
tion on the same batch of the catalyst in the case of the model re-
action (Table 1). In order to regenerate the catalyst, after each cycle,
it was separated with a magnet, and washed several times with de-
ionized water and ethanol. Then, it was dried in an oven at 50°C and
used in the next run. The results show that this catalyst can be
reused seven times without any significant loss in activity (Fig. 9).
This high catalytic activity can be possibly related to the strong
interaction of Pd nanoparticles with active sites of cyano
groups. Palladium leaching of the catalyst was studied before
and after the reaction using ICP-AES analysis. The Pd content
is found to be 2.75 and 2.59 wt% before and after the seven
reactions series, respectively, which is indicative of insignificant
Pd leaching.
EtOH
75
H2O
50
EtOH–H2Oc
EtOH–H2Oc
EtOH–H2Oc
EtOH–H2Oc
EtOH–H2Oc
EtOH–H2Oc
98
60
85
K2CO3
K2CO3
No base
75
96
Trace
aReaction conditions: bromobenzene (1 mmol), PhB(OH)2 (1.1 mmol),
Fe3O4/Ethyl-CN/Pd, solvent (3 ml).
bIsolated yield.
cEtOH–H2O = 1:1.
using with para- or meta-substituted aryl bromides (Table 2, entries
4–11, 13,14). Notably, heteroaryl halides such as 2-bromothiophene
and 2-iodothiophene with phenylboronic acid give the correspond-
ing coupled products in 92 and 90% yields, respectively (Table 2,
entries 16 and 17).
The heterogeneity of the catalyst was evaluated to study
whether the reaction using solid Pd catalyst occurs on the Fe3O4/
Ethyl-CN surface or is catalysed by Pd species leached in the liquid
phase. To address this issue, two separate experiments were con-
ducted with bromobenzene and phenylboronic acid. In the first ex-
periment, the reaction was terminated after 20 min; at this juncture,
the catalyst was separated from the reaction mixture with an
Table 2. Heterogeneous Suzuki–Miyaura reaction of aryl halides with
phenylboronic acid catalysed by Fe3O4/Ethyl-CN/Pd at room
temperaturea
Entry
RC6H4X
X
Time (h)
Yield (%)b
1
H
H
H
I
0.2
1
98
96
25
98
90
20
98
88
95
90
98
88
92
80
96
90
92
2
Br
Cl
I
3
10
0.5
1
4
4-CH3
5
4-CH3
Br
Cl
I
6
4-CH3
12
0.5
1.5
0.5
2
7
4-COCH3
4-COCH3
4-CH3O
4-CH3O
4-Cl
8
Br
I
9
10
11
12
13
14
15
16
17
Br
Br
Br
I
0.8
4
2-CHO
3-NO2
1
3-NO2
Br
I
5
1-Naphthyl
2-Thienyl
2-Thienyl
1
I
2
Br
6
aReactions were carried out under aerobic conditions in 3 ml of H2O–
EtOH (1:1), 1.0 mmol arylhalide,1.1 mmol phenylboronic acid and
2 mmol K2CO3 in the presence of catalyst (0.007 g, 0.2 mol% Pd).
bIsolated yield.
Scheme 3. Possible mechanism of Suzuki coupling reaction using Fe3O4/
Ethyl-CN/Pd.
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Magnetically recoverable and reusable Pd nanocatalyst
E. Domínguez, Adv. Synth. Catal. 2006, 348, 1836; c) Q. Yang, S. Ma,
J. Li, F. Xiao, H. Xiang, Chem. Commun. 2006, 41, 2495.
[10] H. Wu, C. Wu, Q. He, X. Liao, B. Shi, Mater. Sci. Eng. C 2010, 30, 770.
[11] J. H. Xia, H. Shen, B. F. Shu, W. Zhang, Mater. Res. Bull. 2008, 43, 2213.
[12] T. Matsunaga, H. Takeyama, Science 1998, 5, 391.
[13] S. Sun, C. Murray, D. Weller, L. Folks, A. Moser, Science 2000, 287, 1989.
[14] E. H. Kim, Y. Ahn, H. S. Lee, J. Alloys Compd. 2007, 434–435, 633.
[15] M. Racuciu, D. E. Creanga, G. Calugaru, J. Optoelectron. Adv. Mater. 2005,
7, 2859.
[16] S. Tang, L. Wang, Y. Zhang, S. Li, S. Tian, B. Wang, Fuel Process. Technol.
2012, 95, 84.
[17] B. V. Subba Reddy, A. Siva Krishna, A. V. Ganesh,
G. G. K. S. Narayana Kumar, Tetrahedron Lett. 2011, 52, 1359.
[18] R. Parella, N. Srinivasarao, A. Babu, Catal. Commun. 2012, 29, 118.
[19] H. Niu, Z. Meng Dizhang, Y. Cai, J. Hazard. Mater. 2012, 227–228, 195.
[20] H. Liu, Z. Jia, S. Ji, Y. Zheng, M. Li, H. Yang, Catal. Today 2011, 175, 293.
[21] L. Ai, C. Zeng, Q. Wang, Catal. Commun. 2011, 14, 68.
[22] A. Kong, P. Wang, H. Zhang, F. Yang, S. Huang, Y. Shan, Appl. Catal. A
2012, 417, 183.
[23] J. Liu, Y. Zhou, F. Liu, C. Liu, J. Wang, Y. Pan, D. Xue, RSC Adv. 2012, 2,
2262.
[24] G. Li, L. Mao, RSC Adv. 2012, 2, 5108.
[25] Y. Ke, Y. Zeng, X. Pu, X. Wu, L. Li, Z. Zhu, Y. Yu, RSC Adv. 2012, 1, 5676.
[26] Z. Wang, B. Shen, Z. Aihua, N. He, Chem. Eng. J. 2005, 113, 27.
[27] F. Zhang, J. Niu, H. Wang, H. Yang, J. Jin, N. Liu, Y. Zhang, R. Li, J. Ma,
Mater. Res. Bull. 2012, 47, 504.
[28] M. Ma, Q. Zhang, D. Yin, J. Dou, H. Zhang, H. Xu, Catal. Commun. 2012,
17, 168.
Figure 9. Recycling of Fe3O4/Ethyl-CN/Pd for the Suzuki coupling reaction
under similar conditions.
Conclusions
We have developed an efficient protocol for the preparation of
Fe3O4/Ethyl-CN/Pd nanoparticles. The catalyst was characterized
using FT-IR, XRD, FESEM, TEM, VSM, WDX, ICP, EDS and XPS analy-
ses. The heterogeneous catalyst demonstrates good catalytically
performance in the Suzuki coupling reaction. The advantageous
features of the proposed methodology include generality, high
efficiency and simplicity, which lead to short reaction times, high
yields, cleaner reaction profile and easy reusability of the heteroge-
neous catalyst using a magnet. These unique results open new
perspectives for the application of these types of magnetic catalysts
in other organic reactions.
[29] Q. Du, W. Zhang, H. Ma, J. Zheng, B. Zhou, Y. Li, Tetrahedron 2012, 68,
3577.
[30] Z. Wang, P. Xiao, B. Shen, N. He, Colloid Surf. A 2006, 276, 116.
[31] Z. Yinghuai, S. C. Peng, A. Emi, S. Zhenshun, R. A. Kemp, Adv. Synth.
Catal. 2007, 349, 1917.
[32] P. Li, L. Wang, L. Zhang, G. W. Wang, Adv. Synth. Catal. 2012, 354, 1307.
[33] A. N. Ay, N. V. Abramova, D. Konuk, O. L. Lependina, V. I. Sokolov,
B. Z. Karan, Inorg. Chem. Commun. 2013, 27, 64.
Acknowledgements
[34] a) D. Astruc, F. Lu, J. R. Aranzaes, Angew. Chem. Int. Ed. Engl. 2005, 44,
7852; b) C. Deraedt, D. Wang, L. Salmon, L. Etienne, C. Labrugère,
J. Ruiz, D. Astruc, ChemCatChem 2015, 7, 303; c) D. Wang, D. Astruc,
Chem. Rev. 2014, 114, 6949.
We are grateful to Islamic Azad University of Tonekabon and
Payame Noor University for partial support of this work.
[35] B. Sreedhar, S. Kumar, D. Yada, Synthesis 2011, 8, 1081.
[36] S. Li, W. Zhang, M.-H. So, C.-M. Chi-Ming Che, R. Wang, R. Chen, J. Mol.
Catal. A 2012, 359, 81.
References
[1] N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457.
[2] A. Suzuki, J. Organometal. Chem. 1999, 576, 147.
[37] F. Zamani, S. M. Hossein, Catal. Commun. 2014, 43, 164.
[38] H. Veisi, P. Mohammadi, J. Gholami, Appl. Organometal. Chem. 2014, 28,
868.
[39] R. Ghorbani-Vaghei, M. Chegini, H. Veisi, M. Karimi-Tabar, Tetrahedron
Lett. 2009, 50, 1861.
[40] H. Veisi, M. Hamelian, S. Hemmati, J. Mol. Catal. A 2014, 395, 25.
[41] R. Ghorbani-Vaghei, H. Veisi, Synthesis 2009, 6, 945.
[42] H. Veisi, J. Gholami, H. Ueda, P. Mohammadi, M. Noroozi, J. Mol. Catal. A
2015, 396, 216.
[3] A. F. Littke, G. C. Fu, Angew. Chem. Int. Ed. 2002, 41, 4176.
[4] a) L. Yin, J. Liebscher, Chem. Rev. 2007, 107, 133 and references therein;
b) H. Li, L. Wang, P. Li, Synthesis 2007, 39, 1635; c) V. Budarin, J. H. Clark,
J. J. E. Hardy, R. Luque, K. Milkowski, S. J. Tavener, A. J. Wilson, Angew.
Chem. Int. Ed. 2006, 45, 3782; dd) D. Choudhary, S. Paul, R. Gupta,
J. H. Clark, Green Chem. 2006, 8, 479 and references therein.
[5] a) W. Chen, Z. Huang, Y. Liu, Q. He, Catal. Commun. 2008, 9, 516; b)
A. Solhy, J. H. Clark, R. Tahir, S. Sebti, M. Larzek, Green Chem. 2006, 8,
871; c) D. Mahajan, B. A. Ganai, R. L. Sharma, K. K. Kapoor, Tetrahedron
Lett. 2006, 47, 7919.
[6] a) K. Mori, K. Yamaguchi, T. Hara, T. Mizugaki, K. Ebitani, K. Kaneda,
J. Am. Chem. Soc. 2002, 124, 11572; b) T. Hara, K. Mori, M. Oshiba,
T. Mizugaki, K. Ebitani, K. Kaneda, Green Chem. 2004, 6, 507; c)
K. Mori, T. Hara, M. Oshiba, T. Mizugaki, K. Ebitani, K. Kaneda, New J.
Chem. 2005, 29, 1174.
[43] B. Maleki, D. Azarifar, H. Veisi, S. F. Hojati, H. Salehabadi, R. Nejat Yami,
Chin. Chem. Lett. 2010, 21, 1346.
[44] S. Luo, X. Zheng, H. Xu, X. Mi, L. Zhang, J.-P. Cheng, Adv. Synth. Catal.
2007, 349, 2431.
[45] M. Z. Kassaee, H. Masrouri, F. Movahed, Appl. Catal. A 2011, 395, 28.
[46] Z. M. Rao, T. H. Wu, S. Y. Peng, Acta Phys. Chim. Sin. 1995, 11, 395.
[47] R. D. Waldron, Phys. Rev. 1955, 99, 1727.
[48] A. D. Becke, J. Chem. Phys. 1996, 104, 1040.
[7] a) A. Suzuki, N. Miyaura, Chem. Rev. 1995, 95, 2457; b) A. Suzuki,
J. Organometal. Chem. 2002, 653, 83; c) S. P. Stanforth, Tetrahedron
1998, 54, 263.
[8] a) D. A. Horton, G. T. Bourne, M. L. Smythe, Chem. Rev. 2003, 103, 893; b)
P. J. Hajduk, M. Bures, J. Praestgaard, S. W. Fesik, J. Med. Chem. 2000, 43,
3443; c) K. F. Croom, G. M. Keating, Am. J. Cardiovasc. Drugs 2004, 4,
395.
[49] D. Zhang, Z. Liu, S. Han, C. Li, B. Lei, M. P. Stewart, J. M. Tour, C. Zhou,
Nano Lett. 2004, 4, 2151.
[50] M. C. Militello, S. J. Simko, Surf. Sci. Spectra 1994, 3, 387.
[51] T. Teranishi, M. Miyake, Chem. Mater. 1998, 10, 594.
[52] a) A. F. Schmidt, A. A. Kurokhtina, Kinetics Catal. 2012, 53, 714; b)
D. Wang, C. Deraedt, L. Salmon, C. Labrugère, L. Etienne, J. Ruiz,
D. Astruc, Chem. Eur. J. 2015, 21, 1508; c) A. K. Diallo, C. Ornelas,
L. Salmon, J. Ruiz Aranzaes, D. Astruc, Angew. Chem. Int. Ed. Engl.
2007, 46, 8644.
[9] a) C. Fleckenstein, S. Roy, S. Leuthauber, H. Plenio, Chem. Commun.
2007, 42, 2870; b) F. Churruca, R. SanMartin, B. Inés, I. Tellitu,
Appl. Organometal. Chem. (2015)
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