A facile synthesis of a solvent-dispersible magnetically recoverable Pd0 catalyst for the C-C coupling reaction

Article abstract of DOI:10.1039/c6ra11674d

Solvent-dispersible magnetite particles (Fe₃O₄) functionalized with dopamine (DA) and N,N-dimethylglycine (DMG) were successfully prepared by a one-pot synthesis method with environment-friendly materials. Then Pd⁰ nanoparticles were anchored onto the functionalized Fe₃O₄. The prepared materials were thoroughly characterized by TEM, XRD, XPS, FT-IR and VSM. The resultant magnetically recoverable Pd catalyst exhibited excellent catalytic activity for the C-C coupling reaction. In addition, this catalyst revealed high efficiency and stability during recycling stages. This work should be useful for the development and application of a magnetically recoverable Pd catalyst on the basis of green chemistry principles.

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ARTICLE TYPE
0
A facile synthesis of solvent-dispersible magnetically recoverable Pd
catalyst for C-C coupling reaction
abc
c
c
c
c
c
a
Li Wu , Bin Yuan , Mengmeng Liu , Hongfei Huo , Yu Long , Jiantai Ma* , Gongxuan Lu*
5
Solventꢀdispersible magnetite particles (Fe O ) functionalized with dopamine (DA) and
3
4
N,Nꢀdimethylglycine (DMG) were successfully prepared by a oneꢀpot synthesis method with
0
environmentꢀfriendly materials. Then Pd nanoparticles were anchored onto the functionalized Fe O . The
3
4
prepared materials were thoroughly characterized by TEM, XRD, XPS, FTꢀIR and VSM. The resultant
magnetically recoverable Pd catalyst exhibited excellent catalytic activity for the CꢀC coupling reaction.
In addition, this catalyst revealed high efficiency and stability during recycling stages. This work should
be useful for the development and application of magnetically recoverable Pd catalyst on the basis of
green chemistry principles.
1
0
Introduction
which cause concerns of high costs and environmental issues
extensively. Although these homogeneous palladium catalyst
nanoparticles have shown outstanding catalytic properties, it
remains a major challenge to solve several disadvantages such as
costꢀeffectiveness and environmentꢀfriendly . Therefore, it is
highly desirable to develop reusable heterogeneous palladium
catalysts which can be easily used from the reaction systems
Immobilization of Pd NPs on inorganic supports such as silica,
5
5
6
6
7
7
8
0
5
0
5
0
5
0
Since the 1970s, a series of methodologies have been well
developed to construct C–C bonds through metalꢀcatalyzed
crossꢀcoupling, including the Suzuki coupling, Heck coupling,
1
2
2
3
3
4
4
5
0
5
0
5
0
5
1
Kumada coupling, Stille coupling, and so on .
Metal
nanoparticles (MNPs) have attracted scientists due to their unique
physical and chemical properties, such as high surface area, high
reactivity, and enormous specific surface area. MNPs have been
widely applied in many fields, such as drug delivery, photonics,
catalysis, energy storage, and conversion devices . Over the
past few years, MNPs, especially supported magnetic metal
nanoparticles (SꢀMMNPs), have emerged as a new class of
nanocatalyst. Recently, the noble metals supported on magnetic
nanoparticles have emerged as promising catalysts because of the
combined advantages of high surface areaꢀtoꢀvolume ratio and
better magnetic recovery. For example, Zhu et al. reported
Pd immobilized onto magnetic nanoparticles that showed good y
ields and reusability for Suzuki and Heck reaction.
Hoseini et al used the Pd/Fe O /rꢀGO nanohybrid as
nonꢀphosphine catalyst for SuzukiꢀMiyaura reaction in water .
Some palladium magnetic ꢀnanoparticles (NPs) as catalysts for
carbonꢀcarbon coupling reactions such as the Suzuki reaction
alumina, or mesoporous materials, as well as carbon, has been
18ꢀ20
known to produce active catalysts for CꢀC coupling reactions
.
1
−4
Furthermore, taking into account the perspective of green
chemistry, it is preferable to use water to replace toxic organic
solvents as the reaction medium. But many developed
heterogeneous catalytic systems get the drawbacks of low
catalytic activity and poor dispersibility in water. How to address
these issues is now a major problem to chemists studying in this
region.
5
It should be mentioned that N, Nꢀdimethylglycine (DMG) is a
cheap, efficient and general catalytic ligand for the coupling
reaction. DMG has a Chinese name: vitamin B16, which has been
applied in many aspects, such as pharmaceutical intermediates,
S.
Jafar
3
4
6
18
medicine, food and other industries . So it is an environmentally
friendly chemical precursor, and it has a useful application for a
7
ꢀ9
10ꢀ12
have been reported
. Previous studies
of our group have
21ꢀ22
ligand in some catalytic coupling reaction
. Dopamine is an
done a lot in this regard in those years. Importantly, these
catalysts can be easily separated from the reaction system using
an external magnet without filtration. Furthermore, SꢀMMNPs
catalysts showed high catalytic activities and chemical stabilities
in environment friendly solvents.
Homogeneous catalysis for CꢀC bond coupling in organic
synthesis has evolved over the years, which has many
advantages, but also has several disadvantages: difficult
important neurotransmitter that plays a number of important roles
in the human brain and body，also it is widely used to prepare on
various
substrates
as
an
ecoꢀfriendly
magnetically separable
heterogeneous Pd /Fe O ꢀDA/DMG catalyst was synthesized by
surface
24
modification substance . Herein,
a
0
3
4
anchoring palladium onto amineꢀfunctionalized magnetite
particles (Fe O ꢀDA/DMG), which was prepared by a facile
3
4
oneꢀpot solvothermal method. This recyclable heterogeneous
catalyst was used to catalyze CꢀC coupling reaction in an aqueous
solvent, including Suzuki, Heck and Kumada reaction.
13ꢀ17
separation and recovery, high cost etc. Palladiumꢀcatalyzed
Suzuki and Heck crossꢀcoupling reactions constitute important
methods for CꢀC bond formation in organic synthesis. Currently,
these CꢀC coupling reactions are performed mainly in organic
solvents with homogeneous palladium salts and complexes,
Experimental
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Materials
2 mol%), and K CO (2 mmol) was stirred in H O at suitable
2 3 2
temperature for indicated time in air. After completion of the
reaction, the mixture was cooled to room temperature, separated
Ferric chloride hexahydrate (FeCl ·6H O, >99%) anhydrous
3
2
sodium acetate, ethylene glycol, 1, 6ꢀhexanediamine and
dopamine hydrochloride ， ethanol ， N,Nꢀdimethylglycine ，
Palladium chloride, and Sodium borohydride were purchased
from Sinopharm Chemical Reagent Co. Ltd. Various reaction
reagents were purchased from Alfa Aesar. All reagents were of
analytical grade and used without further purification. Deionized
water was used in all of the experiments.
by magnetic decantation, and extracted by Et O (10 mL) for three
2
6
0
times. And then the organic phase was combined and evaporated
under reduced pressure. Finally, the reaction yields were obtained
by GC. The yields of the concrete calculation method is
Gas chromatography area normalization method.
5
0
Pd /Fe O -DA/DMG catalyst for Heck reaction
3
4
65
0.5 mmol of the aryl halides, 0.6 mmol of styrene, and 0.6 mmol
of K CO were taken into 5 mL of H O. and 1 mol% palladium
1
0
Synthesis of Fe O -DA/DMG particles
3
4
2
3
2
catalyst was stirred in the reaction mixture and refluxed at 90℃.
After completion of the reaction, the mixture was cooled to room
temperature, separated by magnetic decantation, and extracted by
Magnetite particles were prepared by oneꢀpot hydrothermal
method. In a typical synthesis, 1.35g FeCl .6H O, 2.96g
3
2
anhydrous sodium acetate and 0.085 g dopamine hydrochloride
were dissolved in 45 mL ethylene glycol. Then 1.0 g DMG was
added under continuous stirring. The mixture was stirred
vigorously for 30 min at 50℃ and then sealed in a Teflonꢀlined
autoclave (50 mL capacity) .The autoclave was heated to 200℃
and maintained at 200℃ for 10 h, and allowed to cool to room
temperature. The black products were thoroughly washed several
times with deionized water and ethanol, then dried at 60℃ for 12
h.
7
0
Et O (10 mL) for three times. And then the organic phase was
2
combined and evaporated under reduced pressure. Finally, the
reaction yields were obtained by GC. The yields of the concrete
calculation method is area normalization method.
1
5
0
Pd /Fe O -DA/DMG catalyst for Kumada coupling reaction
3
4
75
All manipulations were carried out under an inert N atmosphere
2
，
a
mixture of iodobenzene (1 mmol) and
1 mol%
2
0
0
Pd /Fe O ꢀDA/DMG in freshly distilled anhydrous THF (5 mL)
3
4
under N atmosphere was prepared. Then a solution of BuMgCl
2
0
Synthesis of Pd /Fe O -DA/DMG catalyst
(1 mL, 25 wt% in THF, 1.84 mmol) was added dropwise at room
temperature (20 ℃ ) with gentle magnetic stirring. After
completion of the reaction, the mixture was cooled to room
temperature, separated by magnetic decantation, and extracted by
3
4
80
Fe O ꢀDA/DMG (0.15 g) was dispersed in a 50 mL ethanol
3
4
solution under ultrasonication for 1 h. The formed black
suspension was ultrasonically mixed with 1.3 mM of a PdCl2
2
5
Et O (10 mL) for three times. And then the organic phase was
2
solution for 1 h. Then an excess 0.01M NaBH aqueous solution
4
combined and evaporated under reduced pressure. Finally, the
reaction yields were obtained by GC. The yields of the concrete
calculation method is area normalization method.
was slowly dropped into the above system with vigorous stirring,
and the reaction proceeded at room temperature overnight under
stirring. The product was collected, washed with water and
ethanol, and finally dried in vacuum. The weight percentage of
85
3
0
0
Results and Discussion
Pd in Pd /Fe O ꢀDA/DMG, as determined by atomic absorption
3
4
spectroscopic (AAS) analysis, was 5.6wt%.
Catalyst preparation
0
Characterization of Pd /Fe O -DA/DMG catalyst
The process for the preparation of the catalyst
3
4
0
9
0
Pd /Fe O ꢀDA/DMG is schematically described in Scheme 1.
3
4
These magnetic microꢀmaterials were characterized by
transmission electron microscopy (TEM), inductively coupled
plasma (ICP), Xꢀray diffraction (XRD), Xꢀray photoelectron
spectroscopy (XPS), Fourier transformꢀinfrared (FTꢀIR)
spectroscopy and vibrating sample magnetometry (VSM). XRD
measurements were performed on
diffractometer using Cu–Kαradiation as the Xꢀray source in the
θ range of 10–90°. The size and morphology of the magnetic
microparticles were observed by a Tecnai G2 F30 transmission
electron microscopy and samples were obtained by placing a drop
of a colloidal solution onto a copper grid and evaporating the
solvent in air at room temperature. Magnetic measurements of
First, the functionalized magnetite particles were synthesized by a
3
4
4
5
5
0
5
0
11
facile solvothermal synthetic strategy . The purpose of this
operation was to introduce the DA and DMG onto the surface of
0
Fe O particles. Second, Pd nanoparticles were immobilized on
3
4
95
DA/DMGꢀfunctionalized magnetic particles through the
reduction of PdCl by NaBH . We were pleased to acquire a
a Rigaku D/maxꢀ2400
2
4
simply green efficiently method to prepare magnetically
recoverable nanocatalyst.
2
0
Pd /Fe O ꢀDA/DMG were obtained by using a Quantum Design
3
4
VSM at room temperature in an applied magnetic field sweeping
from −8 to 8 kOe. XPS was recorded on a PHIꢀ5702 instrument
and the C 1s line at 284.8 eV was used as the binding energy
reference. The Pd content of the catalyst was measured by ICP on
an IRIS Advantage analyzer to found 5.6 wt% Pd of the catalyst.
0
100 Scheme 1. Schematic formation of Fe
3
O
4
ꢀDAꢀDMG/Pd nanoparticles.
Catalytic performance
Catalyst characterization
0
Pd /Fe O -DA/DMG catalyst for Suzuki reaction
3
4
The TEM images of Fe O , Fe O ꢀDA/DMG and
3
4
3
4
A mixture of aryl halide (1 mmol), arylboronic acid (1.5 mmol),
0
0
Pd /Fe O ꢀDA/DMG catalyst are presented in Fig. 1. The
3 4
5
5
Pd /Fe O ꢀDA/DMG (for aryl bromide 1 mol%, for aryl chloride
3
4
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obtained Fe O ꢀDA/DMG microparticles have an average
3
4
diameter of 200±5 nm (Fig. 1b). As shown in Fig. 1b, a
continuous layer can be observed on the surface. Meanwhile, the
resulting Fe O ꢀDA/DMG composites have good dispersibility
3
4
0
5
and spherical morphology(Fig. 1a,b). After the loading of Pd
Fig. 1c), Pd nanoparticles supported on Pd /Fe O ꢀDA/DMG
0
(
3 4
disperse well and have a uniform particle size. In order to give a
0
powerful evidence for the existence of Pd , EDX spectra of
0
Pd /Fe O ꢀDA/DMG is presented in Fig. 2. The peaks
3
4
1
0
corresponding to Pd are clearly found in EDX spectra of
0
Pd /Fe O ꢀDA/DMG.
3
4
0
30
Figure 3. FTꢀIR spectra of (a) Fe
3
O
4
(b) Fe
3
O
4
ꢀDA –DMG (c) Pd
Fe
3
O
4
ꢀDA –DMG
The
XRD
patterns
of
the
Fe O ꢀDA/DMG
and
3
4
0
3 4 3 4
Figure 1. TEM images of (a) Fe O , (b) Fe O ꢀDA–DMG, and (c)
Pd /Fe O ꢀDA/DMG are presented in Fig 4. The characteristic
diffraction peaks in the samples at 2θ of 30.2º, 35.5º, 43.3º, 53.8º,
57.2º, and 62.8º are corresponded to the diffraction of (220),
3
4
0
Pd /Fe
3
O
4
ꢀDA/DMG catalyst.
35
(
311), (400), (422), (511), and (440) of the Fe O . All the
3 4
diffraction peaks match with the magnetic cubic structure of
19
Fe O (JCPDS 65ꢀ3107) . Figure 4b shows that apart from the
3
4
original peaks, the appearance of the new peaks at 2θ= 40.1, 46.5
and 68.0 are attributed to the Pd (111), (200), (220) species. The
results from XRD imply that the Pd nanoparticles have been
successfully immobilized onto the surface of the magnetic
particles.
40
0
1
5
Figure 2. EDX spectra of Pd /Fe
3
O
4
ꢀDA/DMG.
The FTꢀIR spectra of (a) Fe O , (b) Fe O ꢀDA ꢀDMG and (c)
3
4
3
4
0
Pd Fe O ꢀDA –DMG are shown in Figure 3. In Figure 3, the
band at 585 cm can be attributed to FeꢀO stretching vibration. In
curve b and c, the absorption bands at 1617, 1469, and 878 cm
associated with amine and 1635, 1416 cm associated with
carboxylate, indicating that plenty of Lꢀdopa molecules are
immobilized on the surface of the nanoparticles. The bands at
3
4
ꢀ
1
ꢀ
1
ꢀ
1
2
0
ꢀ
1
ꢀ1
ꢀ1
1
625 cm , 1570cm ， 1436 cm can be attributed to the C=O
ꢀ
1
ꢀ1
stretching vibration. The band at 1089 cm and 1092 cm in the
curve b and c can be attributed to CꢀN stretching vibration. All
the characteristic bands in the FTꢀIR spectrum (Fig. 3b)
demonstrate that the Fe O ꢀDA ꢀDMG magnetic microgel has
2
5
45
Figure 4 XRD patterns of (a) Fe
3
O
4
ꢀDA/DMG and (b)
3
4
0
Pd /Fe O ꢀDA/DMG
3 4
been successfully prepared.
XPS is performed to investigate the chemical state of the surface
0
of the obtained Pd /Fe O ꢀDA/DMG catalyst (Fig. 5). The XPS
3
4
0
50
elemental survey scan of the surface of the Pd /Fe O ꢀDA/DMG
3 4
catalyst reveals the presence of the O, Fe, Pd, N, and C elements
in the samples. As shown in Fig. 5b, the spectra of the Pd 3d
0
region of the two catalysts confirm the presence of Pd with the
peak binding energy of 338.65 and 333.45 ev, which are assigned
to Pd 3d3/2 and Pd 3d5/2, respectively. It is powerful and direct
evidence confirming the existence of Pd (0) in
55
0
Pd /Fe O ꢀDA/DMG catalyst.
3
4
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series of reactions was performed using several time durations,
solvents, bases, and temperatures to obtain the best possible
combination. According to the evaluated results: K CO is found
35
2
3
29
to be the most effective base , the best reaction temperature is 80
, H O is the best solvent.
℃
2
Table 1. Optimization of conditions for the Suzuki reaction of
a
iodobenzene with phenylboronic acid
b
Entry
Solvent
DMF
base
temp
80℃
80℃
80℃
80℃
70℃
60℃
80℃
80℃
80℃
80℃
time
Yield(%)
0
Figure 5. XPS spectra of (a) Pd /Fe
3
O
4
ꢀDA/DMG; and (b) show Pd 3d3/2
,
1
2
3
4
5
6
7
8
9
K
2
CO
CO
CO
3
3
3
30min
30min
30min
30min
30min
30min
30min
30min
30min
30min
69.1
0
Pd 3d5/2 binding energies of Pd /Fe
3
4
O ꢀDA/DMG.
Toluene
EtOH
K
2
54.3
5
0
5
The magnetic measurements were carried out by VSM at room
temperature. The magnetization curves measured for
K
2
66.9
2
H O
2
K CO3
99.9
0
Fe O ꢀDA/DMG and Pd /Fe O ꢀDA/DMG are presented in Fig 6.
3
4
3
4
H
2
H
2
H
2
O
O
O
K
2
CO
3
3
95.3
The magnetic saturation values of Fe O ꢀDA/DMG and
3
4
0
K
2
CO
61.2
Pd /Fe O ꢀDA/DMG are 31.8 and 19.6 emu/g, respectively. The
3
4
NaHCO
NaOAc
KOH
3
80.3
1
decrease in the saturation magnetization is due to the presence of
the DAꢀDMG and Pd nanoparticles on the Fe O4 surface.
2
H O
17.4
3
Moreover, the inset image shows the separation–redispersion
H
2
2
O
O
55.7
0
process of the Pd /Fe O ꢀDA/DMG catalyst. Therefore, the above
3
4
1
0
H
No base
Trace
mentioned results indicated an easy and efficient way to separate
0
1
and recycle the Pd /Fe O ꢀDA/DMG catalyst from the solution by
a Reaction conditions: iodobenzene (0.5 mmol), phenylboronic acid
3
4
an external magnetic force.
(0.75 mmol), H2O (5.0 mL), in air. Pd catalyst (1 mol%) b Determined
by using GC.
With the optimized reaction conditions in hand, the scope of the
0
4
4
5
0
5
0
Pd /Fe O ꢀDA/DMGꢀcatalyzed Suzuki reactions was investigated
3
4
employing various substituted aryl halides to react with various
substituted arylboronic acid. The results are summarized in Table
. The most relevant results in terms of conversion were obtained
by using 4ꢀsubstituted bromoarenes bearing electronꢀwithdrawing
groups (entries 4, 7, Table 2), but for the substrates bearing
electronꢀdonating groups the yield dropped significantly, as
expected . The scope of the reaction was expanded to other
challenging chloride derivatives (entries 19 and 20, Table 1).
Unfortunately, they showed much less reactivity than the bromide
2
28
3
5
counterparts in good accord with the literature .The catalyst kept
similar conversion after 6 successive runs. The above mentioned
results revealed that the Pd /Fe O ꢀDA/DMG catalyst exhibited
0
3
4
Figure 6 .VSM spectra of (a) Fe
3
O
4
ꢀDA/DMG and (b)
0
excellent properties for the Suzuki cross coupling reactions.
Pd /Fe O ꢀDA/DMG
3 4
2
0
Catalytic Activity
Catalyst testing for the Suzuki coupling reaction
CꢀC coupling reactions such as the Suzuki and Heck coupling
reactions play an important role in many types of organic
syntheses, as well as in the chemical, pharmaceutical, and
2
6ꢀ27
2
5
agricultural industries
. Initially, the catalytic activity of
0
Pd /Fe O ꢀDA/DMG was tested for the Suzuki cross coupling
3
4
reaction of a variety of iodobenzene with phenylboronic acid to
their corresponding products. Firstly, the reaction of iodoanisole
with phenylboronic acid was used as a model reaction for the
screening of optimum reaction conditions, and the results were
summarized in Table 1. It was known that the Suzuki reaction
was largely affected by the type of alkaline and the amount of
3
0
2
8ꢀ34
catalyst used
. To explore the optimal reaction conditions, a
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0
a
Table 2. Suzuki cross coupling of aryl halides with aryl boronic acids
using the Fe O ꢀDAꢀDMG/Pd nanocatalyst in water
3 4
3 4
Table 3. Heck reactions using the Fe O ꢀDAꢀDMG/Pd nanocatalyst
0
a
b
Entry
R
1
X
I
R
2
T
Yield (%)
b
entry
R
1
X
I
R
2
T
Yield(%)
99.9
91.2
90.1
97.5
96.3
95.1
93.9
94.0
92.8
96.2
80.8
97.4
99.2
91.7
91.1
94.2
80.1
73.6
51.1
1
2
3
4
5
6
7
8
H
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
14h
14h
14h
14h
14h
14h
14h
14h
99.9
95.8
98.9
99.9
94.2
91.0
98.0
97.2
1
2
3
4
5
6
7
8
9
H
H
H
CH
CH
H
30min
60min
2h
4ꢀCH
3
I
I
3
3
4ꢀ OCH
3
I
4ꢀCH
3
I
4ꢀCOCH
3
I
4ꢀCOCH
4ꢀCH
4ꢀOH
3
I
2h
H
Br
Br
Br
Br
3
I
H
2h
4ꢀCH
4ꢀOCH
4ꢀ COCH
3
I
H
2h
3
4ꢀNO
2
I
H
2h
3
4ꢀNO
2
I
CH
3
2h
a. The reaction was carried out with 0.50 mmol of aryl halides, 0.6 mmol
of styrene, 0.6 mmol of K CO , 1 mol% palladium catalysts with respect
to the aryl halides and 5 mL of H O under an N atmosphere. b. Yield
4ꢀCN
4ꢀNHCOCH
I
H
2h
2
3
1
1
1
1
1
1
1
1
1
1
0
1
2
3
4
5
6
7
8
9
3
I
H
2h
2
2
was determined by GC analysis.
4ꢀNO
2
Br
Br
Br
Br
Br
Br
Br
Cl
Cl
H
9h
Catalyst testing for the Kumada coupling reaction
H
H
12h
1
5
Following the preferably catalytic properties, we carried out
similar Kumada crossꢀcoupling reactions on iodobenzene and
butylmagnesium. In organic chemistry, the Kumada coupling is a
useful cross coupling reaction for generating CꢀC bonds by the
reaction of a Grignard reagent and an organic halide. As shown in
Table 4, the reaction performed very well and the coupled
product was obtained in an excellent yield. The catalyst was
further recycled and reused again.
4ꢀCOCH
4ꢀCH
4ꢀOCH
3
H
60min
90min
60min
90min
90min
24h
3
CH
Cl
CH
Cl
H
3
3
4ꢀ NO
2
3
20
H
H
H
OCH
3
24h
Table 4. Schematic representation of Kumada crossꢀcoupling reaction
between aryl halides and butylmagnesium chloride at room temperature
a Reaction condition: aryl halide (0.5 mmol), aryl boronic acid (0.75 mmol),
K CO (1.0 mmol), Fe O ꢀDAꢀDMG/Pd nanocatalyst (1mol%), and 80 C,
2 3 3 4
0
0
(20 ℃) in presence of Pd / Fe
3
O
4
@DAꢀDMG as catalyst.
in air. b. Yield was determined by GC analysis.
Catalyst testing for the Heck coupling reaction
Encouraged by the exciting results with the Suzuki reactions, the
newly environmentꢀfriendly catalyst was applied to the Heck
b
Entry
R
H
X
I
t
30min
2h
Yield (%)
reaction subsequently. With the intention of catalytic properties,
1
2
3
4
5
6
92.3
0
5
1.5 mol% of Pd /Fe O ꢀDA/DMG was used to the reaction of aryl
3
4
4ꢀCH3
4ꢀCOCH
H
I
90.1
halides and styrene in water. Table 3 displays the results of the
Heck reaction. As shown in Table 3, the Heck reaction of various
aryl iodides with styrene proceeded well in water at 90 ℃,
resulting in the corresponding coupling Heck products in yields
of 91%ꢀ99%. The reaction consequence shows that
electronꢀwithdrawing substituents enhance the coupling product
formation, while electronꢀdonating groups have a negative
influence on the reaction process.
3
I
2h
93.5
Br
Br
Br
12h
2h
94.1
4ꢀCN
85.1
1
0
4ꢀCH
3
2h
89.7
0
a. ArX (1 mmol), BuMgCl (1 mL, 1.84 mmol), Pd /Fe
3
O
4
ꢀDA/DMG (1
2
mol%，), THF (5 mL) stirring at room temperature (20℃) under N .b.
Yield was determined by GC analysis.
0
Reusability of the catalyst Pd /Fe O -DA/DMG
3
4
Finally, the durability is another important factor for catalysts
when involved in practical applications. Herein, asꢀsynthesized
25
0
Pd /Fe O ꢀDA/DMG catalyst has been tested for the reaction of
3
4
iodobenzene with phenylboronic acid employing mg of the
catalyst in the presence of K CO /H O at 80℃. The catalyst was
2
3
2
separated by an external magnet, washed with ethanol, water and
dried under vacuum. The resulting solid catalyst was used
directly for the next run. The yield of the desired product dropped
from 93% to 86% after six runs, which shows a negligible loss in
activity of the catalyst (Table 5). Inductively coupled
plasmaꢀatomic emission spectrometry (ICPꢀAES) measurements
30
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Journal Name, [year], [vol], 00–00
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5

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Page 6 of 7
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DOI: 10.1039/C6RA11674D
indicate that the Pd content in the recycled catalysts after six
reaction cycles is about 2.30wt%, close to that 2.61 wt % of the
6
7
Hoseini S J, Heidari V, Nasrabadi H. J. Mater. Chem A ,2015,
96,90ꢀ95.
a) L.X. Yin, J. Liebscher, Chem. Rev. 2007,107 133–173; b) A.K.
Diallo, C. Ornelas, L. Salmon, J.R. Aranzaes, D. Astruc, Angew.
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Nekoueishahraki, J.M. Basset, V. Polshettiwar, Chem. Soc. Rev.
3
0
asꢀmade Fe O ꢀDAꢀDMG/Pd sample.
3
4
0
50
Table 5. Recycling of Fe
iodotoluene with phenylboronic acid
3
O
4
ꢀDAꢀDMG/Pd for the reaction of
a
2
011 ,40,5181–5203.
a) G. Park, S. Lee, S.J. Son, S. Shin, Green. Chem. 2013, 15,
468ꢀ3473; b) G.M. Scheuermann, L. Rumi, P. Steurer, W.
8
9
3
55
Bannwarth, R. Mulhaupt, J. Am. Chem. Soc. 2009, 13,18262ꢀ8270;
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600.
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Jones, Adv. Synth. Catal. 2006, 34,8609–679.
No. of runs
1
2
3
4
5
6
b
Yield (%)
93
93
92
90
89
87
a Reaction conditions: iodobenzene (0.5 mmol), phenylboronic acid
0.75 mmol), H O (5.0 mL), K CO (1.0 mmol) in air.
(
2
2
3
60
1
1
0
1
X. Le, Z. Dong, Z. Jin, Q. Wang and J. Ma, Catal. Commun., 2014,
b Determined by using GC.
5
3, 47.
P. Wang, H. Liu, J. Niu, R. Li and J. Ma, Catal. Sci. Technol., 2014,
, 1333.
4
Conclusion
6
7
5
0
12 F. Zhang, J. Jin, X. Zhong, S. Li, J. Niu, R. Li and J. Ma, Green
Chem., 2011, 13, 1238.
3 A. Molnár, Chem. Rev., 2011, 111, 2251.
5
0
5
0
In this study, we have developed an efficient method to generate
1
0
highly active Pd /Fe O ꢀDA/DMG composite by a simple method
3
4
14 A. Balanta, C. Godard and C. Claver, Chem. Soc. Rev., 2011, 40,
4973.
15 M. Bakherad and S. Jajarmi, J. Mol. Catal. A: Chem., 2013, 370, 152.
1
1
with environmentꢀfriendly materials. This new compound was
characterized by TEM, EDX, FTꢀIR, VSM, and XRD analysis.
Pd /Fe O ꢀDA/DMG shows good magnetic properties and
6
7
J. Zeng, Q. Zhang, J. Chen and Y. Xia, Nano Lett., 2009, 10, 30.
a)M. Wang, T. Jiang, Y. Lu, H. Liu and Y. Chen, J. Mater. Chem. A,
0
3
4
1
1
2
solventꢀdispersiblity, and has been successfully applied as a
catalyst for Suzuki, Heck and Kumada crossing reactions of
structurally different substrates in water and THF. The
2
3
013, 1, 5923; (b) A. Khazaei et al. J. Mol. Catal. A: Chem. 2015，
98， 241–247. (c)H. Veisi et al. J. Mol. Catal. A: Chem. 2015,
75
396,216–223.
0
18 Kalmar I D, Verstegen M W A, Maenner K, et al. J. British Journal
Pd /Fe O ꢀDA/DMG catalyst exhibited excellent catalytic
3
4
of Nutrition, 2012, 107，1635.
R. B. Bedford, U. G. Singh, R. I. Walton, R. T. Williams and S. A.
Davis, Chem. Mater., 2005, 17, 701.
activity toward the Suzuki, Heck and Kumada cross coupling
reaction with a high yield in water. This catalyst offers a number
of advantages including high reactivity, mild reaction conditions,
and short reaction times in an environmentally benign solvent
system. Furthermore, the magnetic properties imparted by the
Fe O component of the catalyst enables the catalyst to be easily
1
9
8
8
9
9
0
5
0
5
20 A. Biffis, M. Zecca and M. Basato, Eur. J. Inorg. Chem., 2001, 2001，
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2
1
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3
4
2
2
isolated and recycled, thus increases the economic value of the
catalyst.
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The authors are grateful to the Key Laboratory of Nonferrous
Metals Chemistry and Resources Utilization, Gansu Province for
financial support.
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*
a Lanzhou Institute of Chemical Physics, CAS, Lanzhou 730000, China.
Eꢀmail: gxlu@lzb.ac.cn
b University of Chinese Academy of Sciences, Beijing 100049, China
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Journal Name, [year], [vol], 00–00
|
6

Page 7 of 7
RSC Advances
View Article Online
DOI: 10.1039/C6RA11674D
0
The Pd /Fe
3 4
O -DA/DMG catalyst exhibited excellent catalytic activity toward the Suzuki, Heck and Kumada cross
coupling reaction with a high yield . Especially its efficient catalyst for Suzuki and Heck coupling in water.