Palladium nanoparticles supported on modified hollow Fe3O4@TiO2: Preparation, characterization, and catalytic activity in Suzuki cross-coupling reactions

Article abstract of DOI:10.1002/jccs.201700341

Hollow Fe₃O₄@TiO₂-NH₂/Pd as a light-weight, magnetically heterogeneous catalyst was successfully prepared, and characterized by using different techniques including X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) measurements, and thermogravimetric analysis (TGA). Then this heterogeneous catalyst was tested in the Suzuki cross-coupling reaction, and the results confirmed the success of this method. The catalyst could be separated easily using an external magnet and reused at least in five runs successfully without any appreciable loss in its catalytic activity.

Full text of DOI:10.1002/jccs.201700341

Received: 3 October 2017
Revised: 10 January 2018
Accepted: 6 February 2018
DOI: 10.1002/jccs.201700341
A R T I C L E
Palladium nanoparticles supported on modified hollow
Fe3O4@TiO2: Preparation, characterization, and catalytic
activity in Suzuki cross-coupling reactions
Ali Elhampour | Marzie Sadat Mirhosseyni | Firouzeh Nemati
Department of Chemistry, Semnan University,
Hollow Fe3O4@TiO2-NH2/Pd as a light-weight, magnetically heterogeneous cata-
Semnan, Iran
lyst was successfully prepared, and characterized by using different techniques
Correspondence
Firouzeh Nemati, Department of Chemistry,
including X-ray powder diffraction (XRD), Fourier transform infrared spectros-
copy (FT-IR), field-emission scanning electron microscopy (FE-SEM), transmis-
sion electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX),
Semnan University, Semnan 35131-19111, Iran.
Email: fnemati@semnan.ac.ir
vibrating sample magnetometer (VSM) measurements, and thermogravimetric
analysis (TGA). Then this heterogeneous catalyst was tested in the Suzuki cross-
Funding information
Semnan University Science and Technology Park
coupling reaction, and the results confirmed the success of this method. The cata-
lyst could be separated easily using an external magnet and reused at least in five
runs successfully without any appreciable loss in its catalytic activity.
KEYWORDS
hollow heterogeneous catalyst, palladium, Suzuki cross-coupling reaction
immobilization of Pd nanoparticles on solid supports is
one of the useful solutions to this problem.[16] Doubtless,
magnetically supported heterogeneous catalysts have been
found important industrial chemistry owing to their effi-
ciency, stability, and especially their ease of recyclability.
So, using a magnetic substrate consisting of an iron oxide
core and functional shell is the best and simple
way.[17–19]
Since precious metals such as palladium are the key
components in heterogeneous catalysts, and also because
of their rare availability on the earth, there is a great need
to achieve sustainable use of these metals in catalytic
reactions.[20,21]
Recently, there has been a large interest among
researchers on the influence of morphology on the proper-
ties of nanoparticles. Their special structure as well as
physical and chemical properties such as well-defined mor-
phology, uniform size, low density, light weight, and high
surface area, all make hollow Fe3O4 particles gain more
consideration.[22–25]
1
| INTRODUCTION
In the past decade, much attention has been focused on
noble metals, such as palladium, as promising materials for
various applications, owing to their unique optical,
electronic, biomedical[1–3] and especially catalytic activities
in a number of chemical reactions such as hydrogenation of
alkenes and alkynes, carbon–fluorine bond formation, and
a number of C–C cross-coupling transformations including
Suzuki, Negishi, Kumada, Hiyama, and Stille reac-
tions.[4–15]
The surface properties of nanoparticles influence their
catalytic activity, so smaller particles of Pd show
good and acceptable catalytic activity due to their high
surface-to-volume ratio. This superior property (surface to
volume ratio) means higher catalytic participation in the
reaction. In other words, by reducing the size of Pd parti-
cles, the surface energy and also the aggregation of the
nanoparticles increase. The aggregation of nanoparticles
reduces the catalytic activity of Pd nanoparticles. So,
© 2018 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J. Chin. Chem. Soc. 2018;1–8.
http://www.jccs.wiley-vch.de
1

2
ELHAMPOUR ET AL.
As part of our continuing interest in the synthesis of
magnetic nanocatalysts and metal-mediated transformations,
we report here the synthesis and full characterization of a
new heterogeneous catalyst involving Pd based on hollow
Fe3O4@TiO2 particles.[26–35] After preparation of the hol-
low Fe3O4 spheres through the hydrothermal method,[36]
a
TiO2 layer was applied to prevent the aggregation of nano-
particles. Functionalization of these nano-magnetic hollow
spheres was done with (3-aminopropyl) triethoxysilane
(APTES).[37,38] Finally, immobilization of the Pd nanoparti-
cles on core/shell hollow Fe3O4@TiO2-NH2 was done
through a reduction reaction (Scheme 1).[39] Easy prepara-
tion process, reusability, and stability against the air make it
a good choice for the Suzuki cross-coupling reaction.
2
| RESULTS AND DISCUSSION
SCHEME 1 Synthesis of H-Fe3O4@TiO2-NH2/Pd catalyst
The H-Fe3O4@TiO2-NH2/PD composite was fabricated via
a four-step synthetic procedure, which is given in the exper-
imental section. The composite was characterized using
powder X-ray diffraction (XRD), Fourier transform infrared
spectroscopy (FT-IR), field-emission scanning electron
microscopy (FE-SEM), transmission electron microscopy
(TEM), energy-dispersive X-ray spectroscopy (EDX),
vibrating sample magnetometer (VSM) measurements, and
thermogravimetric analysis (TGA).The process of the prepa-
ration of the composite is graphically shown in Scheme 1.
H-Fe3O4 are sharp, suggesting the formation of micrometer-
sized particles. Moreover, the sharp and strong peaks con-
firm that the H-Fe3O4 microparticles are highly crystalline.
In the XRD pattern of H-Fe3O4@TiO2-NH2/Pd (Figure 2c),
the characteristic peaks of H-Fe3O4 (identified by *), those
of amorphous TiO2 (identified by O), and three clear dif-
fraction bands centered at 2θ of 39.9ꢀ, 46.6ꢀ and 68.0ꢀ
(identified by #) corresponding to the (111), (200), and
(220) planes of palladium can be observed.[43] This indi-
cates the presence of Pd NPs with the face-centered cubic
structure.[44] Furthermore, the appearance of a peak at 39.9ꢀ
confirms the presence of palladium in the metallic state.[45]
According to the Debye–Scherer formula, the average crys-
tal size of hollo magnetite and Pd NPs were calculated as
34.5 and 7.2 nm, respectively, which are in good agreement
with TEM observations (see below).
2.1 | FT-IR analysis
The FT-IR spectra of H-Fe3O4, H-Fe3O4@TiO2, H-
Fe3O4@TiO2-NH2, and H-Fe3O4@TiO2-NH2/PD are given
in Figure 1. As observed in Figure 1a–d, the absorption
band in the range 500–700 cm−1 corresponds to the Fe–O
and Ti–O stretching modes.[40]
After functionalization of H-Fe3O4@TiO2 with APTES,
the NH2 symmetric bending vibration and the C-N bond
stretching vibration \ confirmed the presence of the NH2 moi-
ety on the surface of the core/shell particles (Figure 1d).[41]
A decrease in the intensity of all peaks in Figure 1d indicated
the interaction of H-Fe3O4@TiO2-NH2 with the Pd nanopar-
ticles, which was further verified using other techniques.
2.3 | TGA analysis
TGA thermograms of H-Fe3O4@TiO2-NH2 and H-Fe3O4@-
TiO2-NH2/Pd composites (Figure 3) were recorded in air
2.2 | XRD analysis
The XRD analysis of nano-Fe3O4, H-FE3O4, and H-
Fe3O4@TiO2-NH2/Pd was carried out, and their compara-
tive spectra are shown in Figure 2 (a,b,d), respectively. The
XRD spectrum of H-FE3O4 (Figure 2b) shows diffraction
peaks at 2Θ = 30.1ꢀ, 35.5ꢀ, 43.2ꢀ, 52.7ꢀ, 57.1ꢀ, and 62.7ꢀ,
which can be assigned to the (220), (311), (400), (422),
(511), and (440) planes of H-Fe3O4, respectively, and
they clearly match with those reported in the literature.[42]
Compared to those of the nano-Fe3O4 particles, the peaks of
FIGURE 1 FT-IR spectra of H-Fe3O4 (a), H-Fe3O4@TiO2 (b),
H-Fe3O4@TiO2-NH2 (c) and H-Fe3O4@TiO2-NH2/Pd (d) at room
temperature (using KBr pellets)

ELHAMPOUR ET AL.
3
FIGURE 4 Room-temperature magnetization curves of H-Fe3O4(a), H-
Fe3O4@TiO2 (b), and H-Fe3O4@TiO2-NH2/Pd (c)
FIGURE 2 XRD patterns of nano-Fe3O4 (a), H-Fe3O4 (b), and H-
Fe3O4@TiO2-NH2/Pd (c)
2.5 | FE-SEM, EDX, and TEM analysis
SEM and TEM analyses provided significant information
on the size and morphology of H-Fe3O4 microspheres
before and after functionalization. Figure 5 shows typical
FE-SEM images of H-Fe3O4, H-Fe3O4@TiO2, H-Fe3O4@-
TiO2-NH2, and H-Fe3O4@TiO2-NH2/Pd. The SEM images
reveal that the particles were spherical in shape and nearly
monodisperse in size. The images also reveal that the sur-
face of the spheres was not smooth and clearly changed
after coating, functionalization, and immobilization.
The elemental compositions of H-Fe3O4, H-Fe3O4@-
TiO2, H-Fe3O4@TiO2-NH2, and H-Fe3O4@TiO2-NH2/Pd
from EDX analyses further confirmed that the hollow Fe3O4
particles (Figure 6a) were covered with TiO2 (Figure 6b)
and functionalized with –NH2 (Figure 6c), and finally palla-
dium was immobilized on them (Figure 6d). In addition, the
EDX analysis revealed that the catalyst contained ~ 1.5%
Pd (by mass). ICP analysis results also indicated that the
loading of Pd on the support was 1.45%. The presence of
Au element in FE-SEM and EDX analysis confirmed the
coating of the materials by a layer of Au.
To investigate the hollow morphology of the catalyst,
TEM analysis was carried out. The difference in concentra-
tion between the edge and center in the specimens, which is
indicated by the change in color in these regions, indicates
the hollow core of the magnetic Fe3O4. The average diame-
ter of core/shell particles is ~500 nm, which indicates that
the hollow particles are covered completely by the TiO2-
NH2 shell. As shown in Figure 7, after functionalization,
the hollow morphology of the Fe3O4 is fully preserved. The
palladium nanoparticles could be observed with an average
diameter of ~7 nm, and they were homogeneously immobi-
lized on the surface of Fe3O4@TiO2-NH2 hollow spheres.
−1
ꢀ
with a ramp of 5 C min and revealed a weight loss of
ꢀ
nearly 16% in the temperature range 120–800 C, whereas a
weight loss of 7% was recorded for H-Fe3O4@TiO2 in the
same temperature range. Upon comparison of these TGA
data, it is estimated that 8% CH2-CH2-CH2-NH2 moiety is
successfully incorporated in to the H-Fe3O4@TiO2. There-
after, the NH2 groups were complexed with 1% Pd in the
composite material. Inductively coupled plasma (ICP)
spectrum also confirmed that the loading of palladium was
about 1%
2.4 | VSM analysis
The magnetic properties of the resulting products were
determined using a VSM at room temperature, and they
are shown in Figure 4. The saturation magnetization values
for the H-Fe3O4, H-Fe3O4@TiO2, and H-Fe3O4@TiO2-
NH2/Pd are 70.66, 46.78, and 39.26 emu g−1, respectively.
No hysteresis or coercivity was shown by the as-
synthesized particles, indicating that the samples were
superparamagnetic at room temperature.[46] According to
the results of this analysis, it can be concluded that the
catalyst would respond to an external magnetic field
reasonably well.
2.6 | Calculation of H-Fe3O4 density
One of the most important features of hollow spheres is
their low density, because it directly affects the functioning
of the final catalyst. So, in this study the shell density was
FIGURE 3 Thermogravimetric curve of H-Fe3O4 (a), H-Fe3O4@TiO2 (b),
H-Fe3O4@TiO2-NH2 (c), and H-Fe3O4@TiO2-NH2/Pd (d) under air
atmosphere

4
ELHAMPOUR ET AL.
FIGURE 6 EDX analyses of H-Fe3O4 (a), H-Fe3O4@TiO2 (b),
H-Fe3O4@TiO2-NH2 (c) and H-Fe3O4@TiO2-NH2/Pd (d)
FIGURE 5 FE-SEM images of H-Fe3O4 (a), H-Fe3O4@TiO2 (b),
H-Fe3O4@TiO2-NH2 (c) and H-Fe3O4@TiO2-NH2/Pd (d)
desirable substrates for this coupling reaction because of
their low cost and easy availability, but when compared
with aryl iodides and bromides, they are much less reactive
in C–C coupling reactions.[49]
One of the important aspects of an organic catalytic
reaction is the recovery of the catalyst because of industrial
profitability and environmental sustainability. So the reac-
tion between iodobenzene (1 mmol) and phenyl boronic
(1.1 mmol) under optimal conditions was selected to inves-
tigate the constancy of the catalyst activity. At the end of
the reaction, the catalyst was easily separated using an
external magnet. The H-Fe3O4@TiO2-NH2/Pd complex
could be employed six times in the Suzuki coupling reaction
with no significant decrease in its catalytic activity. The
determined by using the specific surface area and shell
thickness, as reported in the literature.[47] The shell density
ρ was calculated with the shell thickness t (nm) (obtained
from XRD), theinner radius of r (nm) (obtained from BET),
and specific surface area SA (m2 g−1) (obtained from
BJH).[36] Therefore, the shell ρ value was calculated as
2
4π ðr + tÞ + r2
f
g
SA = ð4=3Þπρ
:
3
ðr + tÞ −r3
shellf
g
giving ρ = 4.73 g cm−3
As mentioned in the literature, the density of Fe3O4 is
~5.18 g cm−3 [48]
so the as-synthesized hollow spheres have
.
,
a lower density than solid spherical Fe3O4.
2.7 | Catalytic activity of H-Fe3O4@TiO2-NH2/Pd
magnetic composite in Suzuki cross-coupling reaction
Having synthesized and characterized the H-Fe3O4@TiO2-
NH2/Pd magnetic composite, its catalytic activity was tested
in the Suzuki coupling reaction of iodobenzene and phenyl
boronic acid as a model substrate. We optimized the reac-
tion under different conditions, and the results are summa-
rized in Table 1
A preliminary study of the reaction conditions was con-
ducted, including the effect of different solvents, tempera-
ture, bases, and amounts of catalyst. As shown in Table 1,
the best result was achieved with K2CO3 as the base in the
presence of 30 mg of H-Fe3O4@TiO2-NH2/Pd in ethanol/
H2O (2:1) at 60 ꢀC (Table 1, entry 4)
In order to assess the efficiency of the novel magnetic
composite further, the substrate scope of the reaction for the
Suzuki reaction was tested. As shown in Table 2, the reac-
tion of aryl halides bearing electron-withdrawing groups
took more time to complete the reaction than that with
electron-donating groups. Aryl chlorides are highly
FIGURE 7 TEM image of H-Fe3O4@TiO2-NH2/Pd

ELHAMPOUR ET AL.
5
TABLE 1 Optimization of the conditions for the Suzuki cross-coupling
reaction of iodobenzene with phenylboronic acida
product yields for the six runs were 96%, 96%, 95%, 94%,
92%, and 90%, respectively (Figure 8)
Catalyst Temp. Time Yield
FE-SEM and XRD analyses were also performed on the
recycled catalyst after six runs (Figure 9). It was found that
the morphology and crystalline structure of catalyst almost
remained unaltered (Figure 9)
Entry Solvent
Base
(mg)
(ꢀC)
60
60
60
60
60
60
60
60
60
50
25
70
60
(min) (%)b
1
H2O
K2CO3
K2CO3
30
30
30
30
30
40
40
60
30
30
30
30
30
40
53
82
87
96
84
90
86
79
96
75
37
96
96
2
Ethanol
30
3
Ethanol/H2O (1:1) K2CO3
Ethanol/H2O (2:1) K2CO3
Ethanol/H2O (2:1) Et3N
30
4
30
5
30
3
| EXPERIMENTAL
6
Ethanol/H2O (2:1) Cs2CO3 30
7
Ethanol/H2O (2:1) NaOH
Ethanol/H2O (2:1) K2CO3
Ethanol/H2O (2:1) K2CO3
Ethanol/H2O (2:1) K2CO3
Ethanol/H2O (2:1) K2CO3
Ethanol/H2O (2:1) K2CO3
Ethanol/H2O (2:1) K2CO3
30
20
40
30
30
30
30
All chemicals, including FeCl3ċ6H2O, NH4Ac, ethylene
glycol (EG), ethanol, acetonitrile, NH3ċH2O, tetrabutyl
orthotitanate (TBOT), (3-aminopropyl) triethoxysilane
(APTES), and polyvinylpyrrolidone (PVP), were purchased
from Merck and Sigma-Aldrich, and used without further
purification. Thin-layer chromatography (TLC) on com-
mercial aluminum-backed plates of silica gel 60 F254 was
used to control the progress of the reactions, viewed under
ultraviolet light. Magnetic Fe3O4@ TiO2-NH2/Pd hollow
spheres were characterized by the following methods: FT-
IR spectra were obtained with KBr pellets by a Shimadzu
8400s spectrometer; X-ray diffraction (XRD) was carried
out on a Philips instrument using Cu Kα radiation of
wavelength 1.54 Å; scanning electron microscopy (FE-
SEM and EDX0 analysis was performed using a Tescan-
vega II XMU digital scanning microscope; transmission
electron microscope (TEM) images were obtained with a
CM30300Kv instrument; the magnetic properties were
characterized using a VSM (Lakeshore7407) at room tem-
perature. TGA was carried out with a LINSEIS model STS
PT 16000 thermal analyzer in air at the heating rate of
8
9
10
11
12
13
a
Reaction conditions: iodobenzene (1 mmol), phenyl boronic acid (1.1 mmol),
base (1 mmol), solvent (3 mL), and H-Fe3O4@TiO2-NH2-Pd as catalyst.
b
Isolated yield.
3.2 | Synthesis of Aminopropyl-modified hollow-
Fe3O4@TiO2 core shell (H-Fe3O4@TiO2-NH2)
H-Fe3O4@TiO2-NH2 was synthesized by a procedure
reported previously.[39] Here, 500 mg of the as-synthesized
H-Fe3O4@TiO2 was added to 20 mL dry toluene, and the
mixture was treated in an ultrasonic bath for 30 min to
ensure that the H-Fe3O4@TiO2 spheres were fully
dispersed. Finally, 2 mmol of APTES was added to the
resulting solution, and the mixture was refluxed for 24 h
under nitrogen atmosphere. 3-(Aminopropyl)triethoxysilane-
functionalized H-Fe3O4@TiO2 was collected by magnetic
separation, washed sequentially with ethanol (3 × 20 mL),
and dried under vacuum for 24 h
−1
ꢀ
5 C min
3.1 | Synthesis of H-Fe3O4@TiO2
The synthesis of H-Fe3O4 was carried in accordance with
our earlier report.[32] Briefly, 1.0 g of PVP was added and
3.3 | Loading of nano-Pd on Aminopropyl-modified
H- Fe3O4@TiO2 (H-Fe3O4@TiO2-NH2/Pd)
dissolved in 15 mL of EG.
A solution containing
FeCl3.6H2O (1.35 g, 5 mmol), NaOAc.3H2O (3.85 g,
12.6 mmol), and 25 mL EG was added to the mixture, the
mixture was stirred vigorously for 15 min, and it was trans-
ferred to a 100-mꢀL Teflon-lined stainless steel autoclave
and heated at 200 C for 12 h. The black product was col-
lected and washed with ethanoꢀl and deionized water several
times, and finally dried at 80 C in an oven overnight. By
directly coating H-Fe3O4 with a layer of TiO2 through
hydrolyzing TBOT in ethanol and acetonitrile solution, H-
Fe3O4@TiO2 spheres were synthesized.[27] Fifty milligrams
of the as-synthesized H-Fe3O4 was dispersed in a mixed sol-
vent containing 90 mL of ethanol and 30 mL of acetonitrile
ultrasonically. Then, 0.5 mL of NH3.H2O was added to the
mixture. After that, 1 mL of TBOT was added to the above
suspension under stirring for 1.5 h. The products were col-
lected by magnetic separation and washed three times with
ethanol
Loading of Pd nanoparticles onto H-Fe3O4@TiO2-NH2 sub-
strate was performed according to our previous report.[39]
At first, 500 mg of H-Fe3O4@TiO2/NH2 was dispersed in
20 mL ethanol solution under ultrasonication for 0.5 h.
Next, a solution of PdCl2 (12.5 mg, 0.07 mmol) in 10 mL
hot water was added. To the resulting mixture, a solution of
1 mmol NaBH4 in 5 mL water was added, and the mixture
was stirred for 12 h at room temperature. The solid catalyst
was collected with an external magnet, washed sequentially
with EtOH (3 × 20 mL), and dried under vacuum for 24 h
3.4 | General procedure for the Suzuki coupling
reaction
A mixture of iodobenzene (1 mmol), phenyl boronic acid
(1.1 mmol), K2CO3 (1ꢀmmol), and 3 mL of EtOH: H2O
(2:1) was stirred at 60 C in the presence of 30 mg of H-

6
ELHAMPOUR ET AL.
TABLE 2 Suzuki cross-coupling reaction of aryl halide with phenylboronic acidsa
xx
Entry
Aryl halide
Product
Time (min)b
Yield (%)c
1
30
96
2
3
4
45
30
45
87
89
87
5
45
85
6
7
60
60
87
85
8
60
71
9
45
45
88
96
10
11
60
83
(Continues)

ELHAMPOUR ET AL.
7
TABLE 2 (Continued)
xx
Entry
Aryl halide
Product
Time (min)b
Yield (%)c
12
70
68
a
Reaction condition: 1 mmol aryl halide, 1.1 mmol phenyl boronic acid, 1 mmol K2CO3, 30 mg catalyst, and ethanol: H2O (2:1) as solvent (3 mL), at 60 ꢀC.
b
c
Time of the reaction detected by TLC.
Isolated yields.
ACKNOWLEDGMENTS
Fe3O4@TiO2-NH2/Pd as catalyst. The progress of the reac-
tion was monitored by TLC. At the end of the reaction, the
catalyst was separated from the mixture by means of an
external magnet, allowed to cool to room temperature, and
then filtered. Next, the filtrate was extracted with ethyl ace-
tate (20 mL), and the organic layer was washed with water
and brine three times alternatively, and dried with anhy-
drous Na2SO4. Na2SO4 was then filtered off and the filtrate
was concentrated under reduced pressure. The resulting
fragment was purified by short column chromatography
(EtOAc/n-hexane, 2:8) if necessary, to obtain the target
products in high purity.
The authors gratefully acknowledge Semnan University Sci-
ence and Technology Park, Research Council, and the Vice-
chancellor for Education and Postgraduate Students for
financial support of this work.
ORCID
Firouzeh Nemati
http://orcid.org/0000-0002-9446-8936
REFERENCES
[1] L. Zhang, Z. Xie, J. Gong, Chem. Soc. Rev. 2016, 45, 3916.
[2] M. A. Bhosale, T. Sasaki, B. M. Bhanage, Powder Technol. 2016,
291, 154.
[3] D. Astruc, F. Lu, J. R. Aranzaes, Angew. Chem. Int. Ed. 2005, 44, 7852.
[4] S. Paul, M. M. Islam, S. M. Islam, RSC Adv. 2015, 5, 42193.
[5] H. Lin, D. Sun, Org. Prep. Proc. Int. 2013, 45, 341.
[6] A. Fihri, M. Bouhrara, B. Nekoueishahraki, J. -M. Basset, V. Polshettiwar,
Chem. Soc. Rev. 2011, 40, 5181.
[7] L. Yin, J. Liebscher, Chem. Rev. 2007, 107, 133.
[8] M. Lamblin, L. Nassar-Hardy, J. C. Hierso, E. Fouquet, F. X. Felpin, Adv.
Synth. Catal. 2010, 352, 33.
ꢀ
[9] A. Molnár, Chem. Rev. 2011, 111, 2251.
[10] K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. 1975, 16, 4467.
[11] S. Baba, E. Negishi, J. Am. Chem. Soc. 1976, 98, 6729.
[12] D. Milstein, J. Stille, J. Am. Chem. Soc. 1978, 100, 3636.
[13] N. Miyaura, K. Yamada, A. Suzuki, Tetrahedron Lett. 1979, 20, 3437.
[14] A. S. Guram, S. L. Buchwald, J. Am. Chem. Soc. 1994, 116, 7901.
[15] H. Dieck, F. Heck, J. Organomet. Chem. 1975, 93, 259.
[16] X. Le, Z. Dong, Y. Liu, Z. Jin, T. -D. Huy, M. Le, J. Ma, J. Mater.
Chem. A. 2014, 2, 19696.
[17] J. Xia, Y. Fu, G. He, X. Sun, X. Wang, Appl Catal B 2017, 200, 36.
[18] M. Esmaeilpour, J. Javid, J. Chin. Chem. Soc. 2015, 62, 614.
[19] N. Lu, K.-Y. Lin, C.-K. Li, C.-C. Kong, Y.-P. Yeh, Y.-Y. Cheng,
L.-K. Liu, J. Chin, Chem. Soc. 2015, 62, 64.
FIGURE 8 Reusability of the catalyst
[20] M. Pagliaro, V. Pandarus, R. Ciriminna, F. Beland, P. Demma Carà,
ChemCatChem 2012, 4, 432.
ꢁ
[21] M. Opanasenko, P. Štěpnicka, J. Čejka, RSC Adv. 2014, 4, 65137.
[22] S. Peng, S. Sun, Angew. Chem. 2007, 119, 4233.
[23] R. Xing, A. A. Bhirde, S. Wang, X. Sun, G. Liu, Y. Hou, X. Chen, Nano
Res. 2013, 6, 1.
[24] X. Wang, H. Huang, G. Li, Y. Liu, J. Huang, D. -P. Yang, Nanoscale Res.
Lett. 2014, 9, 1.
[25] Y. Liu, Y. Wang, S. Zhou, S. Lou, L. Yuan, T. Gao, X. Wu, X. Shi,
K. Wang, ACS Appl. Mater. Interfaces 2012, 4, 4913.
[26] F. Nemati, A. Elhampour, H. Farrokhi, M. B. Natanzi, Catal. Commun.
2015, 66, 15.
FIGURE 9 FE-SEM (a) and XRD (b) analyses of the recycled catalyst
after six runs

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ELHAMPOUR ET AL.
[27] F. Nemati, M. M. Heravi, A. Elhampour, RSC Adv. 2015, 5, 45775.
[28] A. Elhampour, F. Nemati, M. Kaveh, Chem. Lett. 2015, 45, 223.
[29] F. Nemati, A. Elhampour, Res. Chem. Intermed. 2016, 42, 7611.
[30] F. Nemati, M. M. Heravi, R. S. Rad, Chin. J. Catal. 2012, 33, 1825.
[31] F. Nemati, A. Elhampour, M. B. Natanzi, S. Sabaqian, J. Iran, Chem. Soc.
2016, 131, 1045.
[42] P. Wang, H. Zhu, M. Liu, J. Niu, B. Yuan, R. Li, J. Ma, RSC Adv. 2014,
4, 28922.
[43] J. Niu, F. Wang, X. Zhu, J. Zhao, J. Ma, RSC Adv. 2014, 4, 37761.
[44] W. Li, B. Zhang, X. Li, H. Zhang, Q. Zhang, Appl. Catal. A. 2013,
459, 65.
[45] B. Sreedhar, D. Yada, P. S. Reddy, Adv. Synth. Catal. 2011, 353, 2823.
[46] W. Cheng, K. Tang, Y. Qi, J. Sheng, Z. Liu, J. Mater. Chem. 2010, 20,
1799.
[32] M. S. Mirhosseyni, F. Nemati, A. Elhampour, J. Iran. Chem. Soc. 2017,
14, 791.
[33] A. Elhampour, M. Malmir, E. Kowsari, F. Nemati, RSC Adv. 2016, 6,
9623.
[34] A. Elhampour, F. Nemati, H. T. Nahzomi, V. Mohagheghi, Res. Chem.
Intermed. 2017, 43, 6737.
[35] A. Elhampour, F. Nemati, M. M. Heravi, Monatsh. Chem. 2017, 148,
1793.
[47] C. Takai, H. Watanabe, T. Asai, M. Fuji, Colloids Surf. A. 2012, 404, 101.
[48] X. Liu, J. Liu, S. Zhang, Z. Nan, Q. Shi, J. Phys. Chem. C 2016, 120,
1328.
[49] Y. -O. Kim, J. M. You, H. -S. Jang, S. K. Choi, B. Y. Jung, O. Kang,
J. W. Kim, Y. -S. Lee, Tetrahedron Lett. 2017, 58, 2149.
[36] Q. Xiong, J. Tu, Y. Lu, J. Chen, Y. Yu, Y. Qiao, X. Wang, C. Gu,
J. Phys. Chem. C 2012, 116, 6495.
[37] S. Shylesh, V. Schünemann, W. R. Thiel, Angew. Chem. Int. Ed. 2010, 49,
3428.
[38] M. Gholinejad, A. Aminianfar, J. Mol. Catal. A: Chem. 2015, 397, 106.
[39] A. Elhampour, F. Nemati, Org. Prep. Proc. Int. 2017, 49, 443.
[40] S. -H. Wu, J. -L. Wu, S. -Y. Jia, Q. -W. Chang, H. -T. Ren, Y. Liu, Appl.
Surf. Sci. 2013, 287, 389.
How to cite this article: Elhampour A,
Mirhosseyni MS, Nemati F. Palladium nanoparticles
supported on modified hollow Fe3O4@TiO2: Prepara-
tion, characterization, and catalytic activity in Suzuki
cross-coupling reactions. J. Chin. Chem. Soc. 2018;
1–8. https://doi.org/10.1002/jccs.201700341
[41] H. Naeimi, Z. Rashid, A. -H. Zarnani, R. Ghahremanzadeh, New J. Chem.
2014, 38, 348.