In situ stabilization of Pd(0) nanoparticles into a mixture of natural carbohydrate beads: A novel and highly efficient heterogeneous catalyst system for Heck coupling reactions

Article abstract of DOI:10.1002/aoc.3588

A convenient, mild and cost-effective synthesis of palladium nanoparticles stabilized by a mixture of natural carbohydrate beads (gum arabic and pectin) as a new bio-organometallic catalyst is reported. Powder X-ray diffraction, transmission and scanning

Full text of DOI:10.1002/aoc.3588

Received: 20 July 2016
DOI 10.1002/aoc.3588
Accepted: 22 July 2016
F U L L PA P E R
In situ stabilization of Pd(0) nanoparticles into a mixture of
natural carbohydrate beads: A novel and highly efficient
heterogeneous catalyst system for Heck coupling reactions
1
1
2
Sadegh Rahmati | Ameneh Arabi | Ardeshir Khazaei | Marzieh Khazaei2
*
*
1 Department of Chemistry, Payame Noor
A convenient, mild and cost‐effective synthesis of palladium nanoparticles stabi-
University (PNU), PO Box 19395‐3697,
Tehran, Iran
2 Faculty of Chemistry, Bu‐Ali Sina University, PO
Box 651783868, Hamedan, Iran
lized by a mixture of natural carbohydrate beads (gum arabic and pectin) as a new
bio‐organometallic catalyst is reported. Powder X‐ray diffraction, transmission
and scanning electron microscopies and energy‐dispersive X‐ray and UV–visible
spectroscopies were employed to characterize this supported Pd nanoparticles/
gum arabic/pectin catalyst. The nanocatalyst exhibited efficient activity in
Mizoroki–Heck cross‐coupling reactions between various aryl halides and n‐butyl
acrylate under solvent‐free conditions. The catalyst can easily be recovered from
the reaction system and reused several times with high yields. The products were
obtained in short reaction times with excellent yields.
Correspondence
Sadegh Rahmati, Department of Chemistry,
Payame Noor University (PNU), PO Box
19395‐3697, Tehran, Iran.
Email: rahmati61@yahoo.com
Ardeshir Khazaei, Faculty of Chemistry, Bu‐Ali
Sina University, PO Box 651783868,
Hamedan, Iran.
Email: khazaei_1326@yahoo.com
KEYWORDS
gum arabic, Mizoroki–Heck reaction, palladium nanoparticles, pectin, solvent‐free
1
|
INTRODUCTION
Gum arabic, also known as acacia gum, is a natural gum
made of hardened sap taken from two species of the acacia
tree.[28] Gum arabic is a biologically active branched polysac-
In recent years, the synthesis of metal nanoparticles with a
variety of geometries has been an especially important issue
because their optical, electronic, magnetic and biomedical
properties can be tuned by controlling their shape and size.[1]
Also design and development of green catalysts have
attracted a large number of studies by academic and industrial
groups to reduce or eliminate the use of hazardous
substances.[2]
Recently, immobilization of palladium nanoparticles on
solid supports to prepare active and stable catalytic
systems has attracted interest, and various supports have
been employed to stabilize the nanoparticles, such as
silica‐based materials,[3–8] dendrimers,[9] metal oxides,[10–12]
carbon nanotubes,[13–15] polymers,[16] ionic liquids,[17–20]
polyvinylpyrrolidone,[21,22] gelatin,[23] polyaniline[24] and
carbohydrate‐based materials.[25–27]
charide[29] with wide applications in food and pharmaceutical
industries.[30] This natural carbohydrate has also been used
for stabilization of nanostructures.[31–33]
Pectin is a natural polymer extensively employed in the
food industry, as a thickener or stabilizing agent. It is a poly-
saccharide that is found extensively in citrus peel. Some
unique properties of pectin, such as biodegradability, flexibil-
ity, non‐toxicity and carrying freely available hydroxyl
groups, make it suitable for many applications in various
areas of science.[34,35] Pectin contains free carboxyl groups
on its backbone which can form complexes with Pd(II) ions
in solution and reduce them to Pd(0) without using any extra
reducing agent such as NaBH4, hydrazine or molecular
hydrogen. This slow‐rate in situ reduction of Pd(II) to Pd(0)
causes the formation of small‐size and well‐distributed palla-
dium nanoparticles on the surface of pectin.[36] Therefore
gum arabic/pectin mixture being used as a new support for
palladium species has two advantages: first, it can reduce
Pd(II) to Pd(0) via its available free carboxyl groups by liber-
ation of CO2 gas; and, second, it acts as a highly
In order to develop the use of carbohydrate‐based mate-
rials as supports for palladium nanoparticles, we decided to
introduce a gum arabic/pectin mixture as a suitable and natu-
rally degradable support for the stabilization of palladium
nanoparticles.
Appl Organometal Chem 2016; 1–7
wileyonlinelibrary.com/journal/aoc
Copyright © 2016 John Wiley & Sons, Ltd.
1

2
RAHMATI ET AL.
functionalized support that can stabilize the reduced form of
the palladium nanoparticles by ligation.
2H, J = 8 Hz), 4.03 (t, 2H, J = 8 Hz), 6.39 (d, 1H,
J = 16 Hz), 7.3 (t, 3H), 7.44 (M, 2H), 7.6 (d, 1H,
J = 16 Hz). 13C NMR (CDCl3, 100.6 MHz, δ, ppm): 13.74,
21.02, 30.78, 60.37, 64.41, 118.3, 128.07, 130.19, 134.48,
144.53, 167.08. FT‐IR (ν, cm−1): 1714.17 (C═O).
The Mizoroki–Heck coupling reaction is among the most
important and widely used reaction for the formation of car-
bon–carbon bonds, which allows the arylation, alkylation or
vinylation of various alkenes through their reactions with
aryl, vinyl, benzyl or allyl halides, acetates or triflates in the
presence of palladium and a suitable base in a single step
under mild conditions.[37]
It is of current interest to develop new catalytic systems
which meet the goals of simple operation procedure, low cat-
alyst loading and high activity towards aryl halides. Herein,
we report that palladium nanoparticles supported on gum ara-
bic/pectin mixture (Pdnp/gum arabic/pectin) generated from
PdCl2 in situ showed high activity in Mizoroki–Heck cross‐
coupling reactions between activated and non‐activated aryl
halides and n‐butyl acrylate under solvent‐free conditions.
Product 3a. 1H NMR (CDCl3, 400.2 MHz, δ, ppm): 0.86
(t, 3H, J = 8 Hz), 1.33 (quint, 2H, J = 8 Hz), 1.60 (sex, 2H,
J = 8 Hz), 3.17 (s, 3H), 4.11 (t, 2H, J = 8 Hz), 6.40 (d, 1H,
J = 8 Hz), 6.71 (m, 2H), 7.20 (m, 1H), 7.39 (m, 1H), 7.8
(1H). 13C NMR (CDCl3, 100.6 MHz, δ, ppm): 13.72,
19.21, 30.82, 55.40, 64.31, 77.15, 111.11, 120.62, 123.39,
128.88, 131.46, 139.98, 158.3, 167.6. FT‐IR (ν, cm−1):
1710.62 (C═O).
Product 4a. 1H NMR (CDCl3, 400.2 MHz, δ, ppm): 0.87
(t, 3H, J = 8 Hz), 1.35 (sex, 2H, J = 8 Hz), 1.60 (m, 2H), 2.21
(s, 3H), 4.11 (d, 2H, J = 8 Hz), 6.28 (d, 1H, J = 16 Hz), 7.11
(d, 2H, J = 8 Hz), 7.30 (d, 2H, J = 8 Hz), 7.50 (d, 1H,
J = 16 Hz). 13C NMR (CDCl3, 100.6 MHz, δ, ppm): 11.27,
13.79, 19.22, 21, 44, 30.81, 64.32, 117.20, 128.04, 131.75,
144.50, 167.27. FT‐IR (ν, cm−1): 1714 (C═O).
2
| EXPERIMENTAL
Product 5a. 1H NMR (CDCl3, 400.2 MHz, δ, ppm): 0.89
(t, 3H, J = 8 Hz), 1.37 (sex, 2H), 1.62 (quint, 2H), 2.44
(s, 3H), 4.15 (t, 2H, J = 4 Hz), 6.40 (d, 1H, J = 16 Hz),
7.59 (d, 1H, J = 8 Hz), 7.82 (d, 1H, J = 16 Hz), 7.98 (quarter,
2H). 13C NMR (CDCl3, 100.6 MHz, δ, ppm): 13.66, 13.7,
13.75, 19.16, .68, 64.85, 121.37, 123.33, 125.45, 127.28,
138.98, 139.73, 148.14, 166.17. FT‐IR (ν, cm−1): 1716
(C═O).
2.1 | Synthesis of Pdnp/Gum arabic/Pectin
Pectin (0.5 g) and gum arabic (0.5 g) were dissolved in water
(100 ml) at room temperature. To this solution was added a
solution of PdCl2 (100 ml, 1 mM) and diluted with water
(100 ml). The reaction mixture was refluxed at 100°C for
5 h so that the complete conversion of Pd(II) to Pd(0) was
ensured. The mixture was cooled to room temperature and
the solvent was evaporated. The obtained dark grey
composite was dried by a flow of air over night and then
under vacuum for 24 h.
Product 6a. 1H NMR (CDCl3, 400.2 MHz, δ, ppm): 0.86
(t, 3H, J = 8 Hz), 1.34 (sex, 2H), 1.59 (sex, 2H), 3.70 (s, 3H),
4.09 (t, 2H, J = 4 Hz), 6.19 (d, 1H, J = 16 Hz), 6.8 (d, 2H,
J = 8 Hz), 7.3 (d, 2H, J = 12 Hz), 7.5 (d, 1H, J = 16 Hz).
13C NMR (CDCl3, 100.6 MHz, δ, ppm): 10.16, 10.15, 12.7,
15.68, 18.1, 29.67, 47.47, 63.81, 112.31, 120.89, 126.93,
130.69, 137.75, 165.5. FT‐IR (ν, cm−1): 1711 (C═O).
Product 7a. 1H NMR (CDCl3, 400.2 MHz, δ, ppm): 0.88
(t, 3H, J = 7.2 Hz), 1.36 (sex, 2H), 1.63 (sex, 2H), 4.15
(t, 2H, J = 8 Hz), 6.42 (d, 1H, J = 16 Hz), 7.55 (t, 3H,
J = 12 Hz), 7.60 (d, 2H, J = 8 Hz). 13C NMR (CDCl3,
100.6 MHz, δ, ppm): 10.16, 12.7, 18.06, 29.67, 53.24,
63.841, 112.31, 117.34, 120.89, 127.06, 130.69, 165.2. FT‐
IR (ν, cm−1): 1713 (C═O).
2.2 | General method for Mizoroki–Heck reaction
using nanocatalyst
To a flask were added Pdnp/gum arabic/pectin (0.05 g of the
composite), aryl halide (1 mmol), n‐butyl acrylate (1.5 mmol,
0.21 ml) and n‐Pr3N (1.5 mmol, 0.29 ml) under solvent‐free
conditions. The mixture was stirred at 140°C in air. The
reaction having been completed (monitored by TLC), ethyl
acetate (10 ml) was added to the flask. The catalyst was
separated by simple filtration. Water (3 × 15 ml) was added
to the ethyl acetate phase and decanted. The organic layer
was dried over anhydrous Na2SO4. After evaporation of the
solvent, the crude product was purified by column
chromatography.
Product 8a. 1H NMR (CDCl3, 400.2 MHz, δ, ppm): 0.88
(t, 3H, J = 8 Hz), 1.36 (quint, 2H), 1.62 (sex, 2H), 4.10
(t, 2H, J = 8 Hz), 6.43 (d, 1H, J = 8 Hz), 7.54 (t, 3H,
J = 8 Hz), 7.61 (quart, 2H). 13C NMR (CDCl3,
100.6 MHz, δ, ppm): 13.7, 19.14, 30.66, 64.78, 113.29,
118.34, 121.87, 128.33, 132.61, 138.73, 142.07, 166.18.
FT‐IR (ν, cm−1): 1715 (C═O).
Product 1a. 1H NMR (CDCl3, 400.2 MHz, δ, ppm): 0.81
(t, 3H, J = 8 Hz), 1.29 (sex, 2H, J = 8 Hz), 1.62 (M, 2H,
J = 8 Hz), 4.11 (t, 2H, J = 8 Hz), 6.31 (d, 1H, J = 16 Hz),
7.17 (M, 2H), 7.28 (M, 1H), 7.50 (M, 1H), 7.90 (M, 1H).
13C NMR (CDCl3, 100.6 MHz, δ, ppm): 11.61, 13.62,
19.09, 30.65, 55.56, 64.48, 77.24, 120.81, 127.50, 130.09,
134.71. FT‐IR (ν, cm−1): 1716 (C═O).
1
Product 9a. H NMR (CDCl3, 400.2 MHz, δ, ppm):
0.88 (t, 3H, J = 4 Hz), 1.35 (sex, 2H), 1.63 (quint,
2H, J = 8 Hz), 4.10 (t, 2H, J = 8 Hz), 6.30 (d, 1H,
J = 16 Hz), 7.26 (d, 2H, J = 8 Hz), 7.36 (d, 2H, J = 8 Hz),
7.52 (d, 1H, J = 16 Hz). 13C NMR (CDCl3, 100.6 MHz,
δ, ppm): 11.24, 13.75, 16.83, 19.19, 30.75, 54.1, 64.55,
1
Product 2a. H NMR (CDCl3, 400.2 MHz, δ, ppm):
0.89, (t, 3H, J = 8 Hz), 1.35 (sex, 2H, J = 8 Hz), 1.62 (sex,

RAHMATI ET AL.
3
118.88, 128.12, 132.96, 166.85. FT‐IR (ν, cm−1): 1715
(C═O).
solvent‐free conditions. The results demonstrated that the
temperature plays a significant role in the reaction rate. The
activity of the catalyst increased with increasing temperature
(Table 2, entries 5–8) with the activity being very high at
140°C. During our optimization studies, various bases were
examined and the catalyst was found to be very active and
selective for the reaction in the presence of n‐Pr3N (Table 2,
entry 8) as a liquid organic base, while the reaction rate was
very slow when inorganic bases were used (Table 2, entries
10–12). Entry 8 (bold) shows our selected conditions for
the Mizoroki–Heck reaction.
2.3 | Procedure for reusability of nanocatalyst
After the completion of the reaction for the first run, the reac-
tion mixture was cooled to room temperature and ethyl ace-
tate (5 ml) was added to the reaction mixture in order to
extract the organic layer. The ethyl acetate phase was
removed using a syringe and the catalyst was dried under vac-
uum. The dry catalyst was reused for subsequent reaction.
This process was repeated three times with success (Table 1).
3
| RESULTS AND DISCUSSION
2.4 | Optimizing reaction conditions
Pdnp/gum arabic/pectin was prepared by addition of an aque-
ous solution of PdCl2 (100 ml, 1 mmol) to pectin and gum
arabic (0.5 g of each dissolved in 100 ml of water) without
any extra reducing agent under reflux conditions for 5 h
(Figure 1). This solution was refluxed giving a grey solution
and, after drying in vacuum, afforded a dark grey solid.
UV–visible spectroscopic data for the resulting supported
Pd nanoparticles indicate the conversion of Pd(II) to Pd(0) by
the disappearance of the peak at around 450 nm (Figure 2).
The coupling reaction of iodobenzene with n‐butyl acrylate
was used as a model reaction to investigate the catalytic per-
formance of Pdnp/gum arabic/pectin. The influence of bases,
solvents and reaction temperature on the yield was investi-
gated (Table 2). Employing dimethylsulfoxide (DMSO) as
the solvent in the presence of n‐Pr3N at 140°C gave 100%
conversion of the starting material after 17 min (Table 2,
entries 1 and 2). The use of other protic and organic solvents
(Table 2, entries 2–4) was not beneficial to the process. We
also studied the reaction under solvent‐free conditions. The
results clearly show that the reaction under solvent‐free
conditions (Table 2, entry 8) proceeded better than in sol-
vents with an excellent yield and shorter reaction time. The
reaction was also studied at various temperatures under
TABLE 1 Recycling for the reaction of iodobenzene with n‐butyl acrylate
catalysed by Pdnp/gum arabic/pectin
Run
1
6
2
8
3
FIGURE 1 Preparation of Pdnp/gum arabic/pectin.
Time (min)
11
TABLE 2 Optimization studies for reaction of iodobenzene with n‐butyl
acrylate in presence of Pdnp/gum arabic/pectina
Entry
Base
Solvent
DMSO
T (°C)
Time (min)
Yield (%)b
1
n‐Pr3N
n‐Pr3N
n‐Pr3N
n‐Pr3N
n‐Pr3N
n‐Pr3N
n‐Pr3N
n‐Pr3N
DABCO
KOAc
140
Reflux
Reflux
Reflux
100
17 min
900
900
900
360
145
40
94 (100)
36 (41)
18 (12)
8 (16)
2
EtOH
3
H2O
4
Toluene
5
Solvent free
Solvent free
Solvent free
Solvent free
Solvent free
Solvent free
Solvent free
Solvent free
70 (79)
89 (100)
90 (100)
95 (100)
90 (100)
81 (87)
89 (94)
62 (70)
6
120
7
130
8
140
6
9
140
80
10
11
12
140
900
900
900
K2CO3
NaOH
140
140
aReactions carried out using 1 mmol of idobenzene, 1.5 mmol of n‐butyl acrylate
and 1.5 mmol of base.
bYields are given for isolated products. The data presented in parenthesis refer to
the conversion of iodobenzene.
FIGURE 2 UV–visible spectra of (A) Pd(II) before reduction and (B) Pd(0)
after reduction with gum arabic and pectin.

4
RAHMATI ET AL.
This change shows that the mixture of pectin and gum arabic
is able to form complexes with Pd(II) ions and reduce them to
Pd(0).
The result of energy‐dispersive X‐ray analysis (EDX)
shows the presence of palladium. Its loading amount is mea-
sured to be 1.83% (w/w) in the Pdnp/gum arabic/pectin cata-
lyst. In Figure 3, the EDX spectrum also shows signals of
carbon, nitrogen and oxygen being present in the gum arabic
and pectin.
The X‐ray diffraction (XRD) pattern of the Pdnp/gum
arabic/pectin catalyst confirms the formation of Pd
nanoparticles. The XRD pattern shows that the characteristic
peaks at (1 1 1), (2 0 0) and (3 1 1) can be clearly observed for
Pd particles (Figure 4). These characteristic peaks indicate
crystallographic planes of the Pd(0) nanoparticles. According
to crystallographic planes from the diffraction pattern, a face‐
centred cubic crystalline structure is indicated for Pd(0).
A transmission electron microscopy (TEM) image of the
catalyst shows that Pd nanoparticles with near‐spherical mor-
phology are formed onto the surface of gum arabic and pectin
with relatively good monodispersity. The TEM image indi-
cates that the size of the palladium particles must be in the
range 3–6 nm (Figure 5). Also a field‐emission scanning
electron microscopy (FESEM) image of the Pdnp/gum ara-
bic/pectin catalyst shows the size of the particles to be in
the range 3–6 nm (Figure 6).
FIGURE 5 TEM image of the Pdnp/gum arabic/pectin catalyst showing the
morphology of Pd nanoparticles on the surface.
In order to show the application of these nanoparticles in
organic synthesis, we applied them as catalyst in the
Mizoroki–Heck reaction. With the optimized reaction condi-
tions, a range of aryl iodides and bromides with various sub-
stituent groups with n‐butyl acrylate were examined in the
Mizoroki–Heck reaction. The reaction was performed under
FIGURE 6 FESEM image of Pdnp/gum arabic/pectin catalyst that shows the
morphology of Pd nanoparticles on the surface.
solvent‐free conditions at 140°C and in the presence of
n‐Pr3N. The desired products are obtained in short reaction
times with excellent yields (Table 3).
High reaction rates and yields are obtained with both acti-
vated and non‐activated aryl iodides (Table 3, entries 1–7).
Aryl iodides without any substituent and activated aryl
iodides with electron‐withdrawing substituents are reactive
substrates in Mizoroki–Heck reactions and the corresponding
reactions are completed in shorter times. As an example, the
reaction of iodobenzene with n‐butyl acrylate is completed
within 6 min giving the desired product in 95% isolated yield
(Table 3, entry 2). Non‐activated aryl iodides with electron‐
donating substituents on the aromatic ring are not reactive
substrates in Heck reactions and the corresponding reactions
are completed in longer reaction times.
FIGURE 3 EDX spectrum of Pdnp/gum arabic/pectin.
The Pdnp/gum arabic/pectin catalytic system was also
applied for reactions of substituted aryl bromides and
FIGURE 4 XRD pattern of Pdnp/gum arabic/pectin.

RAHMATI ET AL.
5
TABLE 3 Reaction of aryl halides with n‐butyl acrylate catalysed by Pdnp/gum arabic/pectin
Entry
Aryl halide
Product
Time (min)
Yield (%)
1
1a
2a
5
92
2
3
6
8
95
90
3a
4a
5a
4
5
10
20
92
93
6
7
8
6a
7a
8a
30
45
60
94
90
98
9
9a
120
78
heteroaryl bromides giving the desired products in moderate
to high yields (Table 3, entries 8 and 9).
To show the catalytic activity of the Pdnp/gum arabic/pec-
tin system, we compare previously reported systems with the
present system in the Mizoroki–Heck reaction. Bhaumik and
co‐workers reported the application of Pd nanoparticles teth-
ered into mesoporous polymer MPTA1 in the Mizoroki–
Heck reaction of iodobenzene with n‐butyl acrylate in the

6
RAHMATI ET AL.
presence of K2CO3 as a base in water under reflux. Under
these conditions, the reaction was completed within 5 h,[38]
while for a similar reaction with our catalytic system, the
desired product is obtained within 6 min in 95% yield
(Table 3, entry 2). Also, in another report, palladium
supported on superparamagnetic nanoparticles was used as
a catalyst for the Mizoroki–Heck reaction of iodobenzene
with n‐butyl acrylate. The reaction was completed within
5 h in the presence of K2CO3 in N‐methyl‐2‐pyrrolidone as
solvent at 130°C,[39] whereas a similar reaction using the
present catalyst, as mentioned above, is completed within
6 min. Wang and co‐workers reported the application of
Pd nanoparticles supported on functionalized mesoporous
silica in the Mizoroki–Heck reaction of iodobenzene
with n‐butyl acrylate in the presence of Et3N as a base in
dimethylformamide at 120°C. Under these conditions, the
reaction was completed within 1 h.[40] A similar reaction
under our conditions gives the desired product within only
6 min in 95% yield (Table 3, entry 2).
of aryl iodides and bromides, with respect to reaction time
and amount of catalyst, show that the catalyst has excellent
activity. The supported palladium nanoparticles can be eas-
ily recovered and reused.
ACKNOWLEDGMENTS
We gratefully acknowledge financial support from Bu‐Ali
Sina University Research Councils, Payame Noor University
and the Center of Excellence in Development of Chemistry
Methods (CEDCM).
REFERENCES
[1] Z. Huang, X. Jiang, D. Guo, N. Gu, J. Nanosci. Nanotechnol. 2011,
11, 9395.
[2] R. Tao, S. Miao, Z. Liu, Y. Xie, B. Han, G. An, K. Ding, Green Chem. 2009,
11, 96.
[3] P. Wang, Q. Lu, J. Li, Mater. Res. Bull. 2010, 45, 129.
[4] J. Demel, S.‐E. Park, J. Cejka, P. Stepnicka, Catal. Today 2008, 132, 63.
[5] A. Barau, V. Budarin, A. Caragheorgheopol, R. Luque, D. J. Macquarrie,
A. Prelle, V. S. Teodorescu, M. Zaharescu, Catal. Lett. 2008, 124, 204.
The in situ generation of nanoparticles without addition
of any external reducing agents, stability toward air and
humidity, easy handling and recycle ability are some unique
features of the Pdnp/gum arabic/pectin catalytic system. It is
worth mentioning that some reactions proceeding in the pres-
ence of the Pdnp/gum arabic/pectin system under solvent‐free
conditions are among the fastest ever reported.
[6] R. Bernini, S. Cacchi, G. Fabrizi, G. Forte, S. Niembro, F. Petrucci,
R. Pleixats, A. Prastaro, R. M. Sebastian, R. Soler, M. Tristany, A.
Vallribera, Org. Lett. 2008, 10, 561.
[7] J. Demel, J. Cejka, P. Stepnicka, J. Mol. Catal. A 2007, 274, 127.
[8] V. Polshettiwar, P. Hesemann, J. J. E. Moreau, Tetrahedron 2007, 63, 6784.
[9] K. R. Gopidas, J. K. Whitesell, M. A. Fox, Nano Lett. 2003, 3, 1757.
[10] Q. Du, W. Zhang, H. Ma, J. Zheng, B. Zhou, Y. Li, Tetrahedron 2012,
68, 3577.
The reusability of heterogeneous catalysts is seen to be of
great importance. The reusability of the catalyst was checked
using the reaction of iodobenzene with n‐butyl acrylate
as substrates in the presence of the catalyst and n‐Pr3N at
140°C. After the reaction was completed in the first run, the
organic compounds were separated from the reaction mixture
by a simple extraction and the resulting solid mass was
reused three times. In the first run, the reaction is completed
within 6 min with 95% yield. The nanocatalyst was reused
three times with some decrease in the catalytic activity of
the catalyst. For the third run, the reaction was completed
within 11 min with 89% yield. It is interesting to note that
during the recycling process the shape and size of the
nanocatalyst do not change notably.
[11] M. Ma, Q. Zhang, D. Yin, J. Dou, H. Zhang, H. Xu, Catal. Commun. 2012,
17, 168.
[12] Z. Yinghuai, S. C. Peng, A. Emi, S. Zhenshun, R. A. Monalisa, Kemp, Adv.
Synth. Catal. 2007, 349, 1917.
[13] M. R. Nabid, Y. Bide, S. J. T. Rezaei, Appl. Catal. A 2011, 406, 124.
[14] J. Zhu, J. Zhou, T. Zhao, X. Zhou, D. Chen, W. Yuan, Appl. Catal. A 2009,
352, 243.
[15] A. Corma, H. Garcia, A. Leyva, J. Mol. Catal. A 2005, 230, 97.
[16] B. Tamami, S. Ghasemi, J. Mol. Catal. A 2010, 322, 98.
[17] V. Calo, A. Nacci, A. Monopoli, P. Cotugno, Angew. Chem. Int. Ed. 2009,
48, 6101.
[18] C. Ye, J. C. Xiao, B. Twamley, A. D. Lalonde, M. G. Norton, J. M. Shreeve,
Eur. J. Org. Chem. 2007, 30, 5095.
[19] Z. Zhang, Z. Zha, C. Gan, C. Pan, Y. Zhou, Z. Wang, M. M. Zhou, J. Org.
Chem. 2006, 71, 4339.
[20] C. C. Cassol, A. P. Umpierre, G. Machado, S. I. Wolke, J. Dupont, J. Am.
Chem. Soc. 2005, 127, 3298.
4
| CONCLUSIONS
[21] D. L. Martins, H. M. Alvarez, L. C. S. Aguiar, O. A. C. Antunes, Appl.
Catal. A 2011, 408, 47.
In summary, a novel, environmentally friendly, one‐step
method to synthesize stable Pd nanoparticles is reported
[22] C. Evangelisti, N. Panziera, P. Pertici, G. Vitulli, P. Salvadori, C. Battocchio,
G. Polzonetti, J. Catal. 2009, 262, 287.
[23] H. Firouzabadi, N. Iranpoor, A. Ghaderi, J. Mol. Catal. A. 2011, 347, 38.
here. Pdnp/gum arabic/pectin as
a new category of
[24] A. Houdayer, R. Schneider, D. Billaud, J. Ghanbaja, J. Lambert, Appl.
Organometal. Chem. 2005, 19, 1239.
nanocomposite was obtained easily under green conditions
without addition of any external reducing agent. The
nanoparticles immobilized on the mixture of gum arabic
and pectin showed high catalytic activity in the Heck reac-
tion for various aryl halides (iodides and bromides) under
solvent‐free conditions. This green approach for the synthe-
sis of Pd nanoparticles may find various medicinal as well
as technological applications. The yields for the reactions
[25] V. Calo, A. Nacci, A. Monopoli, A. Fornaro, L. Sabbatini, N. Cioffi, N.
Ditaranto, Organometallics 2004, 23, 5154.
[26] A. Khalafi‐Nezhad, F. Panahi, Green Chem. 2011, 13, 2408.
[27] H. Firouzabadi, N. Iranpoor, F. Kazemi, M. Gholinejad, J. Mol. Catal. A
2012, 357, 154.
[28] S. C. Smolinske, Handbook of Food, Drug, and Cosmetic Excipients, CRC
Press, Boca Raton, FL 1992 7.

RAHMATI ET AL.
7
[29] A. Bicho, A. C. A. Roque, A. S. Cardoso, P. Domingos, I. L. Batalha, J. Mol.
Recognit. 2010, 23, 536.
[37] V. Polshettiwar, A. Molnar, Tetrahedron 2007, 63, 6949.
[38] J. Mondal, A. Modak, A. Bhaumik, J. Mol. Catal. A 2011, 350, 40.
[30] M. P. Yadav, J. M. Igartuburu, Y. Yan, E. A. Nothnagel, Food Hydrocolloids
2007, 21, 297.
[39] F. Zhang, J. Niu, H. Wang, H. Yang, J. Jin, N. Liu, Y. Zhang, R. Li, J. Ma,
Mater. Res. Bull. 2012, 47, 504.
[31] M. K. Kumar, A. L. M. Reddy, S. Ramaprabhu, Sens. Actuators B 2008, 130,
[40] P. Wang, Q. Lu, J. Li, Mater. Res. Bull. 2010, 45, 129.
653.
[32] V. Kattumuri, K. Katti, S. Bhaskaran, E. J. Boote, S. W. Casteel, G. M. Fent,
D. J. Robertson, M. Chandrasekhar, R. Kannan, K. V. Katti, Small 2007,
3, 333.
How to cite this article: Rahmati, S., Arabi, A.,
Khazaei, A., and Khazaei, M. (2016), In situ stabiliza-
tion of Pd(0) nanoparticles into a mixture of natural
carbohydrate beads: A novel and highly efficient het-
erogeneous catalyst system for Heck coupling reac-
tions, Appl. Organometal. Chem., doi: 10.1002/
aoc.3588
[33] D. N. Williams, K. A. Gold, T. R. P. Holoman, S. H. Ehrman, O. C. Wilson,
J. Nanopart. Res. 2006, 8, 749.
[34] B. L. Ridley, M. A. O'Neill, D. Mohnen, Phytochemistry 2001, 57, 929.
[35] B. R. Thakur, R. K. Singh, A. K. Handa, Crit. Rev. Food Sci. Nutr. 1997,
37, 47.
[36] A. Khazaei, S. Rahmati, S. Saednia, Catal. Commun. 2013, 37, 9.