Combination of palladium and oleic acid coated-magnetite particles: Characterization and using in Heck coupling reaction with magnetic recyclability

Article abstract of DOI:10.1016/j.ica.2013.09.042

The magnetic Fe₃O₄ nanoparticles were prepared by co-precipitation method and coated with oleic acid. The oleic acid coated Fe₃O₄ (Fe@OA) particles were used for the immobilization of palladium particles to prod

Full text of DOI:10.1016/j.ica.2013.09.042

Accepted Manuscript
Combination of palladium and oleic acid coated-magnetite particles: character-
ization and using in Heck coupling reaction with magnetic recyclability
Ezzat Rafiee, Ali Ataei, Shirin Nadri, Mohammad Joshaghani, Sara Eavani
PII:
S0020-1693(13)00527-6
http://dx.doi.org/10.1016/j.ica.2013.09.042
ICA 15670
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Please cite this article as: E. Rafiee, A. Ataei, S. Nadri, M. Joshaghani, S. Eavani, Combination of palladium and
oleic acid coated-magnetite particles: characterization and using in Heck coupling reaction with magnetic
recyclability, Inorganica Chimica Acta (2013), doi: http://dx.doi.org/10.1016/j.ica.2013.09.042
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Combination of palladium and oleic acid coated-magnetite particles:
characterization and using in Heck coupling reaction with magnetic
recyclability
*
Ezzat Rafiee , Ali Ataei, Shirin Nadri, Mohammad Joshaghani, Sara Eavani
Faculty of Chemistry, Razi University, Kermanshah, 67149, Iran
Abstract: The magnetic Fe
3
O
4
nanoparticles were prepared by co-precipitation method and coated
(Fe@OA) particles were used for the immobilization of
with oleic acid. The oleic acid coated Fe
3
O
4
palladium particles to produce Fe@OA-Pd. Catalyst was characterized by FTIR, XRD, SEM, TEM,
VSM, elemental analysis and laser particle size analyzer. The catalytic behavior of Fe@OA-Pd nano
particles was measured by the Heck coupling reaction of the various aryl halides (Ar-Br, Ar-Cl) with
styrene. With respect to the electron-rich, electron-neutral, and electron-poor aryl halide, they reacted
with styrene smoothly to provide the corresponding arylated olefins products in high to excellent
yields in most cases. The magnetic catalyst was reused without loss of its high catalytic activity and
low Pd leaching after four cycles. Metal leaching of the catalyst was further investigated by ICP-AES
and AAS.
Keywords: C-C Coupling reaction; Heck reaction; Magnetite iron oxide; Heterogeneous catalyst;
Palladium; Oleic acid
*
Corresponding author: Tel/Fax: +98 831-4274559; E-mail: e.rafiei@razi.ac.ir, ezzat_rafiee@yahoo.com
1

1
. Introduction
Heck coupling reaction, based on the palladium-catalyzed arylated of olefins (Scheme 1), has
benefited from variety of applications in areas of polymerization processes, pharmaceuticals, and
advanced synthesis of natural products [1-6]. Many publications concerning the improvements to the
original Heck reaction conditions have appeared in the literature.
Development of this reaction is greatly dependent on the reactivity 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
catalyst, problems associated with the separation and recovery of the expensive active catalyst, limit
their use in industrial and synthetic applications. In light of this, continuous efforts are now being
made to carry out the reactions with heterogeneous system to aid recovery, recyclability and re-use of
the catalyst. Immobilization of homogeneous catalysts on various insoluble supports (especially
porous materials with high surface areas) can lead to simplify catalyst recycling via filtration or
centrifugation. But, 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 diffusion factors. In the
attempt to resolve such problems, nanoparticles (NPs) have used as alternative soluble matrixes for
supporting homogeneous catalysts. When the size of the support materials is decreased to the
nanometer scale, the surface area of NPs will increase dramatically. As a consequence, NPs could
have higher catalyst loading capacity and higher dispersion than many conventional support
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
incorporation of magnetic NPs (MNPs) into supports offers a solution to this problem. The renewed
interest in synthesis of magnetic nanoparticles (MNPs) is due to their technological applications such
as data storage, biological imaging, and biomedicine [7-11]. One of the attractive features of MNPs
2

is the possibility of fast and cost-efficient separation by applying an external magnetic field, which
makes them as the ideal candidates for practical use in catalysis process. This new direction in
catalysis galvanized the academic research and led to the development of a great number of
magnetic-based catalysts, especially magnetite (Fe
12-21]. Several accounts about synthesis, characterization and application of Fe
in Heck coupling reaction have been reported in the literature [22-29].
It should be noted that magnetostatic interactions between particles, makes Fe
3
O
4
) that found application in the various reactions
[
3
O
4
MNPs utilized
3
O
4
particles
susceptible for agglomeration. On the other hand, the oxidation of Fe causes depletion of
magnetism of Fe . Thus, in order to decrease the agglomeration degree and increase the oxidation
2
+
3
O
4
resistance, effective coating of magnetite particles is essential. Several molecules have been used to
coat on the surface of MNPs. Oleic acid is particularly useful in this regards [30-33], since it is
readily available and non-toxic. In addition, Oleic acid has a strong affinity for magnetite particles
through interaction between its carboxy groups and iron cations on the magnetite surface.
Furthermore, the twisty hydrocarbon tails of oleic acid may help to stabilize the transition metal
catalysts by chains wrapping up the individual metal nanoparticles, thus preventing them from
aggregating with each other.
As a part of our project about the use of magnetic catalyst in organic synthesis [34, 35] and
emanating from our interest in palladium catalyzed cross-coupling reactions [36-42], the present
study evaluates the usefulness of a combination of palladium and oleic acid coated-Fe
3
O
4
nanoparticle (designed as Fe@OA-Pd) in the Heck coupling reaction.
2
. Material and Methods
2.1. General Information
3

All reactions were performed under an atmosphere of dry nitrogen. All chemicals used in this
work were obtained from Fluka, Aldrich or Merck companies and used without further purification.
FTIR spectra were recorded with KBr pellets using a Shimadzu 470 spectrophotometer. XRD
measurements were performed using a Bruker axs Company, D8 ADVANCE diffractometer
(
(
Germany). The morphology of supported catalyst was studied by scanning electron microscopy
SEM) on a model XL30 Philips SEM. The size distribution of the samples was obtained using a
laser particle size analyzer (HPPS5001, Malvern, UK). Gas chromatography was performed on a
Varian CP-3800 (column: CP-Sil 8 CB fused silica capillary column). Thin layer chromatography on
precoated silica gel Fluorescent 254 nm (0.2 mm) on aluminum plates were used for monitoring the
1
reactions. The cross coupling products were characterized by their H NMR spectra. The Fe@OA-Pd
MNPs were observed by transmission electron microscopy (TEM, LEO912-AB). The magnetic
properties of Fe@OA-Pd MNPs were measured using a BHV-55, Riken, Japan vibrating sample
magnetometer (VSM). Elemental analysis was performed using Herause rapid model.
2
.2. Synthesis of Oleic Acid Coated-Fe
The oleic acid coated- Fe
according to a synthesis route described by Yang et al. [43]. Typically, FeCl
FeCl .6H O (11.6 g) were mixed with 350 mL of deionized water. The resulting solution was heated
to 80 °C while stirring, vigorously. Then, 20 mL of 25% NH OH was quickly added into the
3
O
4
Nanoparticles
nanoparticles were prepared by co-precipitation method,
.4H O (4.3 g) and
3
O
4
2
2
3
2
4
solution. The resulting suspension was vigorously stirred for 5 min and then, 1 mL oleic acid was
added into the suspension. After mixing for 25 min, the black precipitates were collected with the
help of a magnet and washed repeatedly with deionized water and ethanol, then dried at vacuum
conditions.
4

2
.3. Synthesis of Fe
A solution of Na
mmol) and NaCl (0.33 g, 5.64 mmol) at room temperature. Fe@OA nanoparticles (0.5 g in 700 mL
methanol) solution was held at 25 °C for 1 h and then Na [PdCl ] (100 mL, 0.011 M) was added.
3
O
4
@OA-Pd Catalyst
2
[PdCl ] (0.011 M) in ethanol was prepared by reacting PdCl (0.50 g, 2.82
4
2
2
4
Then 100 mL of 5 molar NaOAc was added rapidly into the solution. After that, 50 mL of methanol
was added, and the product was separated by magnetic field and washed it with ethanol and water 3
times and dried at vacuum conditions.
2.4. General Procedure for the Heck Coupling Reactions
For Heck coupling reaction, a reaction tube was charged with aryl halide (4 mmol), styrene (4
mmol), tetrabutylammonium bromide, TBAB (4 mmol), K
2
CO (4 mmol), Fe@OA-Pd (0.01 g) and
3
5
mL DMAc and the resulting mixture was refluxed at 120 ºC under a dry nitrogen atmosphere for
appropriate time. Progress of the reaction was monitored by thin layer chromatography (TLC). Upon
completion of the reaction, the reaction mixture was then cooled to room temperature and the catalyst
was separated by magnet, washed with diethyl ether (2 × 10 mL), water (2 × 10 mL), and then dried
under vacuum for reusability. The residual mixture was extracted by CH
2
Cl
2
(3 × 20 mL), the
combined organic layer was dried over MgSO
4
. The solvent was evaporated and the crude products
1
were characterized by H NMR spectroscopy (Supplementary materials).
3. Results and Discussion
3
.1. Characterization Results
The Fe
3
O
4
particles were synthesized according to the literature using ferric chloride
OH. The Fe@OA particles were
hexahydrate and ferrous chloride tetrahydrate upon addition of NH
4
prepared by coating oleic acid on the surface of Fe
3
O
4
particles. For the preparation of palladium
5

loaded materials, Fe@OA particles were treated with a PdCl -NaCl solution, and then a NaOAc
2
solution was added. Finally, the mixture was filtered, followed by drying in vacuum (Scheme 2). The
Pd content in Fe@OA-Pd catalyst was determined 8.4 wt.% by atomic absorption spectroscopic
(
AAS) analysis. The weight percent of oleic acid in Fe@OA-Pd was calculated as 12.3 wt.% using
elemental analysis. The prepared Fe@OA-Pd catalyst was characterized by FTIR, XRD, SEM-WDX,
TEM, VSM and laser particle size analyzer.
Fig. 1 shows the FTIR spectra of Fe@OA (a) and Fe@OA-Pd (b). The broad band near 3442
-1
cm in Fig. 1a refers to the OH stretching vibration associated with absorbed water molecule. Two
−
1
bands at around 2921 and 2851 cm were attributed to the asymmetric and symmetric stretching of
−
1
CH groups of oleic acid, respectively. The peak at 1637 cm exhibited the presence of the C=C
2
−
1
stretching vibration. From the Fig. 1a it is clear that the band at 1710 cm , which was assigned to the
stretching vibration of C=O in oleic acid, is absent in the spectrum of Fe@OA particles. Meanwhile,
−
1
–
two new bands at 1404 and 1542 cm appeared which are characteristic of the asymmetric –(COO )
–
and the symmetric –(COO ) stretch vibration band, respectively. These results could be explained by
the fact that oleic acid was chemically absorbed onto the surface of Fe
3
4
O particles. Literature data
concerning coordination modes of carboxylate group and the metal atom show that in our case the
two oxygen atoms in the carboxylate connected to Fe atoms as bridging bidentate form [30, 43]. The
−
1
−1
absorption bands at 583 cm in Fig. 1a, 571 cm in Fig. 1b, were attributed to Fe-O stretch
vibrations which confirm the existence of Fe in the two samples. Fig. 1b shows that coordination
mode of oleic acid to Fe does not change after immobilization of palladium.
The crystalline structure of the catalyst was investigated by XRD. Fig. 2 shows the
characteristic peaks of Fe alone (ca. 2θ= 30°, 35°, 43°, 53°, 57° and 63°). The absence of main
3
O
4
3
O
4
3
O
4
characteristic peaks of palladium (2θ= 40° and 46°) may be due to a well dispersed metal phase as
6

well as low Pd loading. The result shows that the structure of Fe
3
4
O has been not damaged in the of
catalyst preparation process.
In combination with scanning electron microscopy (SEM), wavelength-dispersive X-ray
spectroscopy (WDX) can provide qualitative information about the distribution of different chemical
elements in the catalyst matrix. Fig. 3 collects representative SEM and corresponding elemental maps
(
WDX) images for the synthesized catalyst. It can be seen that the particles are not fully spherical. In
addition, some particle aggregations are observed, which is likely to be caused by the magnetostatic
interactions between particles. The WDX analysis reveals that Pd metal particles are well dispersed
in the catalyst, which agrees well with the XRD analysis.
The size distribution profile, as shown in Fig. 4, represents a typical batch of particles with a
mean diameter of 165 nm and a narrow size distribution. TEM image indicated that Fe@OA-Pd NPs
have uniform and spherical morphology and the mean diameter of the particles are about 15 nm (Fig.
5). As shown in Fig. 5, aggregation of individual NPs was occurred. Such aggregations cause the
difference between particle size derived from TEM analysis and the measurements made using the
laser particle size analyzer. The magnetic property of Fe@OA-Pd MNPs was characterized using
VSM (Fig. 6). The saturation magnetization (M
s
) of the sample is about 54 emu/g. There is no
hysteresis, suggesting that Fe@OA-Pd MNPs are superparamagnetic.
3
.2. Catalytic Results
At the onset of our catalytic studies, the Heck reaction was examined by treating bromobenzene
as an example of a non-activated aryl bromide, with styrene as coupling partner using of Fe@OA-Pd.
It was found that Fe@OA-Pd is capable of furnishing stilbene with a yield of 88%, when K CO and
2
3
DMAc were used as the base and solvent, respectively. With this result in hand, experiments were
conducted to optimize the reaction conditions for the Heck coupling and the results are summarized
7

in Table 1. Reducing the catalyst loading, from 0.1 g to 0.01 g did not affect the product yield
significantly, but under 0.001 g catalyst loading, the yield goes down to 57% after 24 h (Table 1,
entries 1-3). Having realized the optimum catalyst loading for the reaction (0.01 g), attention turned
to evaluation of the optimum number of equivalents of TBAB (so-called Jeffery condition) as an
additive [44] to effect the Heck coupling reaction (Table 1, entries 4-8). When 0.5 mmol of TBAB
was added, yield and reaction time slightly improved (Table 1, entry 4), while addition of 4 mmol of
TBAB permitted us to achieve 98% yield of the product after 12 h (Table 1, entry 7). The potential
and efficiency of the tetraalkylammonium salts has been illustrated. It is generally accepted that
promoting the oxidative addition step and prevention of palladium black formation, thereby
enhancing the catalyst concentration are factors of the high catalytic activity in the presence of
tetraalkylammonium salts. However, the use of a large excess of TBAB (i.e. 6 mmol) did not
influence the reaction time markedly (Table 1, entry 8).
The use of toluene as a representative non-polar solvent resulted in a significant attenuation of
yield to 35% after 24 h reaction time. A satisfactory result was obtained when water was used as
solvent, but the transformation proved to be sluggish with 72% yield within 24 h. Thus, DMAc
emerged as the most successful solvent for this reaction.
The rate of the Heck reaction was base-dependent as on switching the base from inorganic
(
K
2
CO
1), which suggests an important role for amines in the reduction and stabilization of catalytic active
species during the catalytic process. However, another reason for effectiveness of NEt is probably
due to its solubility in most organic solvents. Upon moving to stronger amine base such as N(Butyl)
reaction time was once again reduced and maximum yield of desired product is reached after 6 h
Table 1, entry 12). When cyclohexyl amine was used as base, longer reaction time was needed for
reasonable yield (Table 1, entry 13).
3
) to organic (NEt ) a remarkable improvement in reaction rate was observed (Table 1, entry
3
1
3
3
(
8

From all of these observations, combination of Fe@OA-Pd and DMAc as the solvent,
N(Butyl)
system.
3
as the base and 4 mmol TBAB as additive was found to constitute as the best catalytic
This optimized reaction conditions was shown to be applicable to several classes of substrate
Table 2). Aryl bromides possessing a variety of electron-donor (entries 1-3) and electron-
(
withdrawing (entries 5-8) substituents were all shown to proceed with comparable yield. Of note, this
catalyst system also had ability to couple styrene with sterically hindered substrates such as 1-
bromonaphthalene and 4-bromobiphenyl in reasonable yields (Table 2, entries 9, 10).
It should be pointed out that catalytic system Fe@OA-Pd showed high selectivity for the trans-
configured product in all cases, and no cis/gem olefin products were observed. However, in the case
of 4-bromoacetophenone small amount of dehalogenation by-product was formed, (Table 2, entry 7).
On comparing results of Table 2, the electric effect of substrates is obvious. Aryl bromides
containing electron-withdrawing functional groups give higher yields with lower reaction times
compared to those containing electron-donating functional groups. From these results, it could be
concluded that under our catalytic system the oxidative addition of Ar-Br to palladium is rate
determining step of Heck coupling.
In studies subsequent to our work with aryl bromides, we found that Fe@OA-Pd can be also
promotes the coupling of aryl chlorides with styrene, albeit to a limited extent (Table 3). The
observed lower yield and longer reaction time for the reaction of aryl chlorides is due to the strength
of the C-Cl bond which causes the rate of oxidative addition C-Cl to Pd(0) species to be slow.
In these reactions, electron-deficient aryl chlorides (Table 3, entries 2-4) showed better
reactivity than the electron-rich analogous (Table 3, entry 1). In addition, steric hindrance had no
effect upon the rate of the reactions. For example, the sterically congested substrates, such as 1-
chloro-2,4-dinitro benzene and 1-chloro naphthalene reacted with styrene efficiently to provide
9

desired products in maximum yield (Table 3, entries 2, 5). In light of these results, we are inclined to
assume that electronic nature of the aryl chloride has a major effect on the catalytic activity.
Our attention next shifted to reaction of the heteroaryl chloride and styrene. From the Table 3
we can see that reaction of 2-chloro-5-nitro-pyridine with styrene was performed in relatively short
time producing the corresponding olefinated product in high yield.
Judged from the results in Tables 2 and 3, obtained conversions of aryl bromides and specially
aryl chlorides using Fe@OA-Pd are one of the best results ever published in literature for Fe
3
4
O -
based catalyst utilized in the Heck coupling reaction [22-25]. Therefore, it is speculated that the
electro-steric effect of oleic acid tail plays a pivotal role in the stabilization of palladium particles.
This interaction likely prevents the aggregation of palladium particles and helps to keep palladium in
solution, consequently enhances the catalytic activity.
3
.2. Reusability
The evaluation of reusability and stability of the catalyst is an important issue and must be
considered in heterogeneous process. The strategy of magnetic separation, taking advantage of
MNPs, is typically more effective than filtration or centrifugation as it prevents loss of the catalyst.
Magnetic separation of the MNPs is simple, economical and promising for industrial applications. To
test the reusability of the catalyst, recycling experiment were carried out using Heck reaction
between bromobenzene and styrene over Fe@OA-Pd. When the reaction was completed, the catalyst
could be placed on the side wall of the reaction vessel with the aid of an external magnet. Fig. 7
showed that a satisfactory yield (above 96%) is still obtained without any prolonged time. Metal
leaching of the catalyst was further investigated by ICP-AES. The results indicated that only a trace
amount of the Pd metal is leached out from the catalyst surface after four cycles. Furthermore, the
filtered solution exhibited no reactivity to model reactions. The Pd content in Fe@OA-Pd catalyst
1
0

after first and fourth runs were determined 8.3 and 7.9 wt.% using AAS analysis respectively. All
these results showed that this new version of Pd-immobilized magnetic catalyst is economic and
environmentally friendly because of its low Pd leaching after four cycles. We expect that this novel
heterogeneous magnetic nano catalyst has more wide applications in Pd-catalyzed reactions.
4
. Conclusions
The immobilized palladium on oleic acid-coated Fe
3
4
O was found to be effective in the Heck
arylation of various aryl bromides and especially less reactive aryl chlorides with styrene. In fact,
Fe@OA-Pd could combine the advantages of both homogeneous and heterogeneous reaction systems
in regard to high catalytic activity, easy recovering and reusability. It seems that oleic acid have
played an important role in stabilization of catalyst particles owing to its structural diversity. The
dependence of the rate on the electronic nature of the aryl halide suggests that the oxidative addition
of aryl halide affect the overall rate.
Acknowledgments
The authors thank the Razi University Research Council for support of this work.
References
[
[
[
[
[
1] R.F. Heck, J.P. Nolley, J. Org. Chem. 37 (1972) 2320–2322.
2] I.P. Beletskaya, A.V. Cheprakov, Chem. Rev. 100 (2000) 3009–3066.
3] M. Shibasaki, E.M. Vogl, J. Organomet. Chem. 576 (1999) 1–15.
4] J. Mo, L. Xu, J. Ruan, S. Liu, J. Xiao, Chem. Commun. (2006) 3591–3593.
5] W.A. Herrmann, C. Brössmer, K. Öfele, C.-P. Reisinger, Angew. Chem., Int. Ed. 34 (1995)
1
844–1848.
1
1

[
[
[
[
[
[
[
[
6] W.A. Herrmann, V.P.W. Böhm, C.-P. Reisinger, J. Organomet. Chem. 576 (1999) 23–41.
7] J.H. Xia, H. Shen, B.F. Shu, W. Zhang, Mater. Res. Bull. 43 (2008) 2213–2219.
8] T. Matsunaga, H. Takeyama, Supramol, Sci. 5 (1998) 391–394.
9] S. Sun, C. Murray, D. Weller, L. Folks, A. Moser, Science 287 (2000) 1989–1992.
10] H. Kim, Y. Ahn, H.S. Lee, J. Alloys Compd. 434–435 (2007) 633–637.
11] M. Racuciu, D.E. Creanga, G. Calugaru, J. Optoelectron. Adv. Mater. 7 (2005) 2859–2864.
12] S. Tang, L. Wang, Y. Zhang, S. Li, S. Tian, B. Wang, Fuel Process. Technol. 95 (2012) 84–89.
13] B.V. Subba Reddy, A. Siva Krishna, A.V. Ganesh, G.G.K.S. Narayana Kumar, Tetrahedron
Lett. 52 (2011) 1359–1362.
[
[
[
[
[
(
[
[
[
[
[
(
[
[
[
14] R. Parella, N. Srinivasarao, A. Babu, Catal. Commun. 29 (2012) 118–121.
15] H. Niu, Dizhang, Zh. Meng, Y. Cai, J. Hazard. Mater. 227–228, (2012) 195–203.
16] H. Liu, Zh. Jia, S. Ji, Y. Zheng, M. Li, H. Yang, Catal. Today. 175 (2011) 293–298.
17] L. Ai, C. Zeng, Q. Wang, Catal. Commun. 14 (2011) 68–73.
18] A. Kong, P. Wang, H. Zhang, F. Yang, S. Huang, Y. Shan, Appl. Catal. A: Gen. 417–418,
2012) 183–189.
19] J. Liu, Y. Zhou, F. Liu, C. Liu, J. Wang, Y. Pan, D. Xue, Rsc. Adv. 2 (2012) 2262–2265.
20] G. Li, L. Mao, Rsc. Adv. 2 (2012) 5108–5111.
21] Y. Ke, Y. Zeng, X. Pu, X. Wu, L. Li, Z. Zhu, Y. Yu, Rsc. Adv. 2 (2012) 5676–5682.
22] Zh. Wang, B. Shen, Z. Aihua, N. He, Chem. Eng. J. 113 (2005) 27–34.
23] F. Zhang, J. Niu, H. Wang, H. Yang, J. Jin, N. Liu, Y. Zhang, R. Li, J. Ma, Mater. Res. Bull. 47
2012) 504–507.
24] M. Ma, Q. Zhang, D. Yin, J. Dou, H. Zhang, H. Xu, Catal. Commun. 17 (2012) 168–172.
25] Q. Du, W. Zhang, H. Ma, J. Zheng, B. Zhou, Y. Li, Tetrahedron 68 (2012) 3577–3584.
26] Z. Wang, P. Xiao, B. Shen, N. He, Colloid Surface A. 276 (2006) 116–121.
1
2

[
(
[
[
27] Z. Yinghuai, S.C. Peng, A. Emi, S. Zhenshun, Monalisa, R.A. Kemp, Adv. Synth. Catal. 349
2007) 1917–1922.
28] P. Li, L. Wang, L. Zhang, G.W. Wang, Adv. Synth. Catal. 354 (2012) 1307–1318.
29] A.N. Ay, N.V. Abramova, D. Konuk, O.L. Lependina, V.I. Sokolov, B.Z. -Karan, Inorg. Chem.
Commun. 27 (2013) 64–68.
[
[
[
[
[
[
[
30] N. Wu, L. Fu, M. Su, M. Aslam, K.C. Wong, V.P. Dravid, Nano Lett. 4 (2004) 383–386.
31] G. Kataby, M. Cojocaru, R. Prozorov, A. Gedanken, Langmuir 15 (1999) 1703–1708.
32] R. Tadmor, R.E. Rosensweig, J. Frey, J. Klein, Langmuir 16 (2000) 9117–9120.
33] D. Li, D. Jiang, M. Chen, J. Xie, Y. Wu, S. Dang, J. Zhang, Mater. Lett. 64 (2010) 2462–2464.
34] E. Rafiee, S. Eavani, Green. Chem. 13 (2011) 2116-2122.
35] E. Rafiee, S. Eavani, B. Malaekeh-Nikouei, Chem. Lett. 41 (2012) 438-440.
36] M. Joshaghani, E. Faramarzi, E. Rafiee, M. Daryanavard, J. Xiao, C. Baillie, J. Mol. Catal. A:
Chem. 259 (2006) 35–40.
37] M. Joshaghani, M. Daryanavard, E. Rafiee, J. Xiao, C. Baillie, Tetrahedron Lett. 48 (2007)
025–2027.
[
2
[
[
[
[
38] Sh. Nadri, M. Joshaghani, E. Rafiee, Appl. Catal. A: Gen. 362 (2009) 163–168.
39] Sh. Nadri, M. Joshaghani, E. Rafiee, Tetrahedron Lett. 50 (2009) 5470–5473.
40] Sh. Nadri, M. Joshaghani, E. Rafiee, Organometallics 28 (2009) 6281–6287.
41] Sh. Nadri, E. Azadi, A. Ataei, M. Joshaghani, E. Rafiee, J. Organomet. Chem. 696 (2011) 2966–
2
970.
42] A. Ataei, Sh. Nadri, E. Rafiee, S. Jamali, M. Joshaghani, J. Mol. Catal. A: Chem. 366 (2013)
0–35.
[
3
[
[
43] K. Yang, H. Peng, Y. Wen, N. Li, Appl. Surf. Sci. 256 (2010) 3093–3097.
44] T. Jeffery, J.-C. Galland, Tetrahedron Lett. 35 (1994) 4103–4106.
1
3

Figure Captions:
Fig. 1. FTIR spectra of (a) Fe@OA and (b) Fe@OA-Pd.
Fig. 2. XRD pattern of Fe@OA-Pd.
Fig. 3. SEM image of Fe@OA-Pd and elemental maps of Fe and Pd atoms of Fe@OA-Pd.
Fig. 4. The size distribution profile of Fe@OA-Pd using laser particle size analyzer.
Fig. 5. TEM image of Fe@OA-Pd.
Fig. 6. VSM magnetzation curve of Fe@OA-Pd.
Fig. 7. Reusability of Fe@OA-Pd in model reaction after 6 h.
Scheme 1. The Heck coupling reaction, principle and possible isomers.
Scheme 2. Schematic illustration for preparation of Fe@OA-Pd catalyst.
1
4

a
Table 1. Optimization of reaction conditions
Fe@OA-Pd
Br
+
Ph
base, solvent, 120 °C
Ph
b
Entry Catalyst (g)
Base
Solvent
TBAB (mmol)
Time (h)
24
Yield (%)
1
2
3
4
5
6
7
8
9
0.1
0.01
0.001
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
K
2
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
3
3
3
3
3
3
3
3
3
3
3
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
Toluene
-
-
88
80
57
87
90
95
98
98
35
72
98
98
95
K
2
24
K
2
-
24
K
2
0.5
1
22
K
2
20
K
2
2
18
K
2
4
12
K
2
6
11
K
2
4
24
1
0
1
2
3
K
2
H
2
O
4
24
1
1
1
N(Et)
N(Butyl)
Cyclohexzyl amine
DMAc
DMAc
DMAc
4
8
3
4
6
4
12
a
Reaction conditions: bromobenzene (4 mmol), styrene (4 mmol), Base (4 mmol), Fe@OA-Pd and DMAc (5 mL) at 120
°
C.
b
NMR yield
1
5

a
Table 2. Heck reaction of various aryl bromides with styrene
R
R
Fe@OA-Pd
Br
+
Ph
DMAc, N(Butyl)3,
Ph
TBAB, 120 °C
b
Entry
Aryl bromide
Time (h)
6
Yield (%)
Me
Br
85
1
2
3
4
5
6
7
8
MeO
Br
6
10
6
70
70
98
96
98
H N
2
Br
Br
OHC
Br
Br
5
O N
2
5
MeOC
Br
5
3
72
98
N
C
Br
Br
3
4
98
93
9
Br
1
0
a
Reaction conditions: aryl bromide (4 mmol), styrene (4 mmol), N(Butyl)
3
(4 mmol), Fe@OA-Pd (0.01 g), TBAB (4
mmol) and DMAc (5 mL) at 120 °C.
b
NMR yield.
1
6

a
Table 3. Heck reaction of various aryl chlorides with styrene
R
R
Fe@OA-Pd
Cl
+
Ph
DMAc, N(Butyl)3,
TBAB, 120 °C
Ph
b
Entry
1
Aryl Chloride
Time (h)
24
Yield %
H
2
N
Cl
50
NO2
Cl
2
3
98
O N
2
3
4
MeOC
OHC
Cl
24
24
70
80
Cl
Cl
5
6
5
98
98
N
O N
Cl
10
2
a
Reaction conditions: aryl chloride (4 mmol), styrene (4 mmol), N(Butyl)
3
(4 mmol), Fe@OA-Pd (0.01 g), TBAB (4
mmol) and DMAc (5 mL) at 120 °C.
b
NMR yield.
1
7

Fig. 1.
1
8

Fig. 2.
1
9

Fig. 3.
2
0

Fig. 4.
2
1

Fig. 5.
2
2

60
40
20
0
-20
-40
-60
-10000 -8000 -6000 -4000 -2000
0
2000 4000 6000 8000 10000
Applied Field (Oe)
Fig. 6.
2
3

Fig. 7.
2
4

Pd Cat.
R'
R' X
+
R"
+
R"
+
R'
R"
R"
trans
R' cis
gem
R' = aryl, vinyl
R" = aryl, CO R, OR
2
_
+
X= halide, OSO R, N X , COCl
2
2
Scheme 1.
2
5

Scheme 2.
2
6

Highlights
•
•
•
Palladium-immobilized oleic acid-coated Fe
3
O was prepared and characterized.
4
Magnetically separable nano catalyst was found to be effective in Heck reaction.
Palladium leaching was found negligible.
2
7

Graphical Abstract
Combination of palladium and oleic acid coated-magnetite particles: characterization and
using in Heck coupling reaction with magnetic recyclability
Ezzat Rafiee, Ali Ataei, Shirin Nadri, Mohammad Joshaghani, Sara Eavani
Oleic acid-coated palladium-immobilized Fe
3
4
O catalyst was synthesized and used in the Heck
coupling reactions with high yield, magnetic recyclability and low Pd leaching.
2
8