A click strategy for the immobilization of palladium nanoparticles onto silica: Efficient and recyclable catalysts for carbon-carbon bond formation under mild reaction conditions

Article abstract of DOI:10.1039/c6ra11734a

An interesting silica-supported nano-palladium catalyst was successfully prepared through "click" reaction of azide-functionalized silica with methylpropargylimidazolium bromide followed by immobilization of palladium nanoparticles (NPs), in which the click-triazole as an important functional entity acts as both a stable linker and a good chelator. The palladium-NPs are stabilized by synergistic effect of coordination and electrostatic interactions. The as-prepared nanocatalyst was well characterized and found to be highly efficient in Heck and Suzuki-Miyaura coupling in terms of activity and recyclability in aqueous ethanol under phosphine-free and low Pd loading (0.1 mol%) conditions.

Full text of DOI:10.1039/c6ra11734a

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: A. R. Hajipour, P.
Abolfathi and F. Mohammadsaleh, RSC Adv., 2016, DOI: 10.1039/C6RA11734A.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Please do not adjust margins
Page 1 of 11
RSC Advances
View Article Online
DOI: 10.1039/C6RA11734A
Journal Name
ARTICLE
A Click Strategy for the Immobilization of Palladium nanoparticles
onto Silica: Efficient and recyclable catalysts for carbon–carbon
bond formation under mild reaction conditions
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Abdol R. Hajipour a,b*, Parisa Abolfathia and Fatemeh Mohammadsaleha
www.rsc.org/
An interesting silica-supported nano-palladium catalyst was successfully prepared through ‘‘click’’ reaction of azide-
functionalized silica with methylpropargylimidazolium bromide followed by immobilization of palladium nanoparticles
(NPs), in which the click-triazole as an important functional entity acts as both a stable linker and a good chelator. The
palladium-NPs are stabilized by synergistic effect of coordination and electrostatic interactions. The as-prepared
nanocatalyst was well characterized and found to be highly efficient in Heck and Suzuki–Miyaura coupling in terms of
activity and recyclability in aqueous ethanol under phosphine-free and low Pd loading (0.1 mol%) conditions.
as efficient catalysts for the important reactions involving
low catalyst loadings mild and environment-friendly
conditions. The metal-NPs stabilized on the solid surface
have been widely used as efficient catalysts in organic
synthesis. The stabilizers are generally Ligands,9 polymers,10
ionic liquids (ILs),11 and dendrimers12 have developed as
common metal-stabilizers in the literatures.The novel
supported palladium nano-catalysts can be applied in a
Introduction
Heterogeneous catalysis is noteworthy for both academic
and industrial synthesis owing to its advantages over
homogeneous catalysis.1-3 These solid-supported catalysts
improve catalyst stability and facilitate the separation of
the catalyst from reaction media. In fact, one of the
challenging areas of research in heterogeneous catalysis is
stabilization of nano-catalysts on
Supported nano-catalysts are manufactured by reacting a
functionalized surface with available functional groups on
the catalyst atoms.
The palladium-catalyzed coupling reactions are classified
nowadays among the most general transformations in
organic synthesis, which have great applications in both
laboratory and large-scale synthesis.6, 7 In view of advanced
synthesis, the non-renewable use of expensive palladium
catalysts is less valuable, in particular, for industrial scale
synthesis. Over the past few years, considerable interest
has been focused on metallic nanoparticles (NPs) because
of their potential applications in various fields. Metal-NPs
usually display unique properties in comparison with their
bulk materials and the isolated atoms in catalytic
reactions.8 In recent years, Pd-NPs have been widely used
5
diversity of reactions, including Heck and Suzuki carbon-
a
solid surface.4,
17
carbon coupling reactions.13,
The copper(I)-catalyzed
azide−alkyne cycloaddition18 (CuAAC), known as the ‘‘click
reaction’’,19 has
shown wide applications in
bioconjugation,20 drug discovery,21 and polymerscience22
during the past decade. Additionally, the 1,2,3-triazoles
produced in the CuAAC reaction have also drawn much
attention for metal-catalyst immobilization as a highly
stable linker or/and a chelator to graft catalysts onto the
solid supports.23, 24
Grafting of the ionic liquids on the solid surfaces gives a
material with a charged surface. It is found that ILs are able
to stabilize metal NPs through electrostatic interaction,but
the most applications of the reaction are using 1,2,3-triazolyl25,
26 and ionic liquid27 alone as stable linkages for the connection of
two chemical/biological components. The combination of ionic
liquids and 1,2,3-triazolyl coordination group is expected to lead
to the optimum balance between stability and reactivity of
metal NPs, resulting from the highly synergistic effect of
coordination and electrostatic interactions from 1,2,3-triazolyl
and imidazolium group. Niu et al.28 used Multiwalled Carbon
Nanotubes-IL to support Au nanoparticles. Wang et al.29
reported a click-imidazolium- modified copolymer as a solid
support to stabilize the pd- NPs. They also prepared a series of
click ionic salts through click reaction of organic azides with
alkynefunctionalized imidazolium or 2-methylimidazolium
salts.30
a.Pharmaceutical Research Laboratory, Department of Chemistry, Isfahan
University of Technology, Isfahan 84156, Islamic Republic of Iran. E-mail:
haji@cc.iut.ac.ir; arhajipour@wisc.edu; Fax: +98 311 391 2350; Tel: +98 313
3913262
bDepartment of Neuroscience, University of Wisconsin, Medical School,
1300 University Avenue, Madison, 53706-1532, WI, USA
†Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 2 of 11
ARTICLE
Journal Name
In continuation of our efforts to develop eco-friendly
catalytic protocols, and catalysts containing quaternary
ammonium and phosphonium salts.31-34 herein, we present
the synthesis and characterization of a click ionic-silica
supported Pd–NPs, in which the NPs are immobilized by
synergetic effect of coordination and electrostatic
interactions from nitrogen-rich 1,2,3-triazolyl ligands and
imidazolium salts, respectively. The as-prepared material
was evaluated as a solid catalyst in Heck and Suzuki-Mura
coupling reactions.
which demonstrated that the click reaction was successfully
View Article Online
completed. In Fig. 1d, the intensity ofDtOhI:e10p.1e0a3k9s/Cis6RwA1e1a7k34eAr
than that of Silica-Click-IL (Fig. 1c) due to the formation of a
metal–ligand bond. These characteristic absorption peaks
confirm the successful attachment of organic groups and
subsequent coordination of palladium nanoparticles within
the hybrid material. In this catalyst system, since there
were no significant shifts or evidences which have been
35, 36
reported for the NHC-Pd complex based catalysts,
we
could not certainly conclude that N-heterocyclic
carbene/Pd complex (Pd (0)/NHC) is formed. According to
the results of elemental analysis, the loading of click-
methylimidazolium bromide ligand on the silica
Result and Discussion
Preparation and characterization of the catalysts
The pathway to synthesize Si–IL@Pd(0)NPs was depicted in
Scheme 1. Firstly, imidazolium salt was prepared from the
reaction of N-methylimidazole and propargyl bromide. In
the following step, silica was functionalized with 3-
azidopropyltrimethoxysilane, which was subsequently
reacted with N-propargylimidazolium via click reaction in
the presence of CuSO4·5H2O and sodium ascorbate as a
catalytic system. Afterwards, the immobilization of
palladium was carried out by the reduction of Pd(OAc)2 in
the presence of NaBH4 as reducing agent, in CH3CN/H2O as
the solvent system.
The Suzuki–Miyaura reaction of 4-bromonitrobenzene with
phenylboronic acid was chosen as a model to evaluate the
catalytic activity. To begin this investigation, we initially
used immoblilized-palladium (II) click ionic support, which
obtained without using any reducing agent like NaBH4. It
was found that by employing 0.12 mol% of catalyst, and
K2CO3 (0.2 mmol) in the mixed solvent EtOH/H2O (1:1) at 50
oC, the corresponding suzuki product was obtained in 40%
yield after 3 h. However, under the same reaction
conditions, the use of Si–IL@Pd(0)NPs as the catalyst, gave
better conversions and improved the yield well, up to 97%.
This result indicated that the effect of the palladium (0)-NPs
was a significant factor in promoting the reaction. Hence,
Si–IL@Pd(0)NPs was selected as the benchmark catalyst for
further studies on the reaction parameters. The catalyst
was well characterized using techniques including
elemental analysis (EA), inductively coupled plasma analysis
(ICP), FT-IR, TEM, SEM, EDX, XPS and XRD. The progress of
the immobilization of the functional groups was confirmed
by FT-IR Spectroscopy. As shown in Fig. 1a, in the spectrum
of propargylimidazolium, a typical band at about 2934 cm-1
should be ascribed to C–H stretching vibrations. The
characteristic peaks of 1573, 1432, 1163, 752 and 850 cm-1
were corresponding to the FT-IR spectra of the imidazolium
cation. In addition, the absorption at 2124 cm−1 was
attributed to CH stretching vibration of the propargyl
group. In Fig. 1b, the absorption peak at 1098 cm-1
corresponded to the Si–O–Si vibration. Furthermore, the
presence of an absorption band at 2100 cm-1 in FT-IR
Scheme 1 The nanocatalyst preparation
surface was determined to be 0.3 mmol g-1. The
content
inductively coupled plasma (ICP) analysis, which
was 0.12%. Energy dispersive X-ray (EDX)
of
palladium
was
measured
by
analysis of the obtained catalyst approved the
presence of the expected elements such as;
spectrum of compound
3 revealed the successful
immobilization of N3 on silica. In Fig. 1c, after the click
reaction the peaks of azide and alkyne were disappeared,
Fig.1 FT-IR spectra of 1-propargyl-3-methylimidazolium bromide
(a), SiO2 -N3 (b), Silica-Click-IL (c), Silica-Click-IL-Pd (d)
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 11
RSC Advances
Please do not adjust margins
Journal Name
ARTICLE
silicon, bromide, carbon and palladium (Fig. 2). As shown
in Fig. 3a, X-ray diffraction spectroscopy (XRD) pattern of
catalyst that matched well with that of it (Reference
code: 01-087-0643) shows the presence of Pd (0)
particles on the amorphous silica support. The wide
diffraction peak at 2θ = 23O attributed to SiO2 and other
peaks in the sample at 2θ of 39.9O, 46.4O, 67.7O, 81.6O can
be assigned to the diffraction of (111), (200), (220), (311)
crystal planes of Pd (0). XPS measurement was also
performed to elucidate the oxidation state of Pd in the
catalyst. The XPS spectra reveal that Pd is present in the
zero oxidation state (Fig. 3b). The observed binding
energy peaks of Pd 3d5/2 and Pd 3d3/2 electrons at about
335.48 and 340.9 eV, respectively, clearly indicate the
presence of Pd(0) species in the Si-IL@Pd catalyst.
reaction (Table 1). Firstly, we studied efficiency of the
different solvent in Suzuki reaction. Among the tested
View Article Online
DOI: 10.1039/C6RA11734A
solvents, a mixture of H2O/EtOH (1:1, V/V) was chosen as
the most effective solvent, which might be attributed to the
good solubility of the organic reactants and the inorganic
base. In the following step, to obtain the proper base for
the cross-coupling, we examined different bases. The
results of this experiment demonstrated that K2CO3 gave
rise to the most suitable activity of the catalyst in the
Fig.2 EDX spectrum of the catalyst
As displayed in Fig 4 (A and B), TEM images of the fresh
catalyst reveals that palladium nanoparticles were
produced in discrete spherical shape without any signs of
aggregations. The particle size histogram shows that these
nanoparticles have average diameter ranging about 13 nm
(Fig. 4c), indicating that Silica-Click-IL can effectively isolate
adjacent Pd nanoparticles. The information about the
surface of catalyst was also investigated by scanning
electron microscopy (SEM). As shown in Fig. 4d, the organic
components were created with sphere-shaped morphology
and monotonic nanometer-sized particles. The elemental
mapping images for the synthesized catalyst reveals that Pd
nanoparticles are well dispersed on the surface of silica.
The selected-area elemental analysis figure shows the
presence of Si, O and Pd throughout the composite in a
homogeneous manner.The result indicated that the
prepared sample was dispersed uniformly onto the surface
of silica (Fig. 4e).
Fig. 3 XRD pattern of the catalyst (a), XPS spectra of the
catalyst (b)
reaction among other bases such as K3PO4, NaHCO3 and
KOH. Subsequently, we investigated different amounts of
catalyst ranging from 0.05 mol% to 0.2 mol%. On the basis
of this study, 0.1 mol% was found to be the most efficient
and suitable amount of catalyst for the reaction. For the
higher amounts of catalyst, there was no significant
increase in the yield of the reaction. However, the yield of
the reaction was decreased in 0.05 mol% of Pd loading. In
continuation, we investigated the optimum temperature
for the cross-coupling reaction. It was found that, the
reaction was not completed in room temperature, and only
52% of conversion was observed after 12 h. Therefore, the
reaction temperature was raised to 50 oC; in which the
reaction afforded the coupled product in 97% yield. Finally,
the effect of the molar ratio of phenylboronic acid to 4-
bromonitrobenzene on the cross-coupling reaction was
Catalytic tests
The catalytic performance of the nanocatalyst was
evaluated in Suzuki–Miyaura cross-coupling. In order to
obtain appropriate conditions, the efficiency of the various
parameters such as solvent, bases, catalyst loading and
temperature were examined on the reaction of 4-
bromonitrobenzene with phenylboronic acid as the model
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 4 of 11
ARTICLE
Journal Name
View Article Online
DOI: 10.1039/C6RA11734A
Fig. 4 TEM images of the catalyst (a and b), Histogram of the catalyst (c), SEM images of the catalyst (d), the corresponding elemental mapping
images of the catalyst (e)
explored (Table 2). As shown in Table 2, the isolated yield
97% was obtained when the molar ratio was 1.2, while
higher substrate ratios did not provide any improved yields
under the investigated conditions. After optimization, we
Table 1 Effect of different parameters for the reaction of 4-
bromonitrobenzene with phenylboronic acid catalyzed by Si–
IL@Pd(0)NPs catalysta
Entry
Solvent
T(°C)
Base
Time
(h)
Yieldb
applied the nanocatalyst for the reaction of various aryl
halides with phenylboronic acid under optimized
conditions. The results depicted in Table 5 clearly exhibit
that the protocol was amenable to various substrates (iodo,
bromo and chloro-derivatives) and substituents, providing
1
2
3
EtOH
H2O
50
50
50
K2CO3
K2CO3
K2CO3
3.5
62
55
97
4
3
EtOH/H2O
(1:1, V/V)
PEG-400
very good to excellent yields to products. In order to clarify
the generality of the protocol, the reactions of different aryl
halides with phenylboronic acid were checked and the
results are shown in Table 5. Aryl iodides were rapidly
converted into the desired biphenyl products in excellent
yields. The reaction of aryl bromides with phenylboronic
acid under the optimized conditions afforded the desired
products in high yields. Also, for aryl chlorides a little more
time was needed to obtain substantial yields. Overall, the
coupling reaction of phenylboronic acid with electron
withdrawing aryl halides gave better conversions in shorter
reaction times. For the nitro-substituted aryl bromides
(Table 5, Entry 4), the position of the nitro group has a large
effect on the reaction, and moderate yields were obtained
when the methyl group was at the meta position. Steric
hindrance of the procedure was examined using 2-
bromoacetophenone as hindered substituted aryls (Table 5,
Entry 7). As expected, an increasing steric hindrance of
ortho substituents can cause a decrease in the reaction
conversion.
4
5
50
50
K2CO3
K3PO4
5
3
85
93
EtOH/H2O
(1:1, V/V)
EtOH/H2O
(1:1, V/V)
EtOH/H2O
(1:1, V/V)
EtOH/H2O
(1:1, V/V)
EtOH/H2O
(1:1, V/V)
6
7
8
9
50
50
rt
4.5
6
86
73
52
88
NaHCO3
KOH
K2CO3
K2CO3
12
3
40
aReaction conditions: 4-bromonitrobenzene (0.1mmol), phenylboronic
acid (0.12mmol), Si-IL@Pd(0)NPs catalyst 0.1 mol%, base (0.2 mmol)
b GC yield
Reusability and heterogeneity test
The recyclability of the solid catalyst was also examined in
the coupling of 4-bromoacetophenone with phenylboronic
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 11
RSC Advances
Please do not adjust margins
Journal Name
ARTICLE
acid using 0.1 mol% of catalyst in solvent mixture of
H2O/EtOH (1:1) at 50 °C in the presence of 2 mmol of K2CO3.
For this, at the end of each reaction, the catalyst was
separated by centrifugation from the reaction mixture,
washed with water and ethanol several times, dried under
vacuum and used for the next cycle. As shown in Table 3,
no significant decrease catalyst performance was observed
until the fourth reuse. To determine the nature of the
reactive species, i.e., surface or leached Pd, we have also
performed the hot filtration test by using 4-
bromoacetophenone and phenylboronic acid as coupling
partners. The solid catalyst was separated from the solution
after 20 min reaction(~32% conversion) and the reaction
spectra were recorded on a Bruker 400 spectrometer using
deutrated CDCl3 as solvent and tetramethylsilane (TMS) as
View Article Online
DOI: 10.1039/C6RA11734A
Table 3 Reusability of the catalyst in the Suzuki-Miyaura
Run
1
2
3
4
5
6
7
Time (h)
Yield(%)a
95
3
3
4
4
4
5
6
95
93
89
78
75
76
a GC yield
Table 2 Effect of the molar ratio of substrates on the
cross-coupling reactiona
Entry
internal standard. X‐ray diffraction (XRD) powder patterns
Molar ratiob
Yield(%)c
88
were obtained using an X’PERT MPD, with Cu Kα radiation
(40 kV, 30 mA). X-ray photoelectron spectroscopy (XPS)
were obtained using twin anode XR3E2 X-ray source system
operating at a vacuum by X-ray 8025-BesTec spectrometer.
The XPS peaks were deconvoluted by using Voigt function
1
2
3
4
5
1
1.2
1.2
1.5
1.75
97
95d
97
which
is
combination
of
Lorentzian
and
97
Gaussian.Transmission electron microscopy (TEM) images
were obtained using a Philips CM10 microscope. FT-IR
spectroscopy (JASCO FT-IR 680-Plus spectrophotometer)
was employed for characterization of products. Also we
used Inductive coupled plasma Perkin Elmer Optima 7300
DV. Gas chromatography (GC) (BEIFIN 3420 gas
chromatograph equipped with a Varian CP SIL 5CB column:
30 m, 0.32 mm, 0.25 mm) was used for consideration of
reaction conversions and yields. Elemental mapping images
and scanning electron micrographs of the catalyst were
taken on [FE-SEM, HITACHI (S-4160)].
a Reaction conditions: 4-bromonitrobenzene (0.1 mmol), catalyst
0.1mol%, base (0.2 mmol), 50 0c, 3h
b The ratio of phenylboronic acid to 4-bromonitrobenzene
c GC yield
d
At 90 °C for 1.5 h
was then allowed to continue stirring to react for another 3
h. After this time, no further progress in product yield was
observed upon catalyst removal. The ICP analysis only
showed 0.02 ppm palladium in solution, indicating that
essentially no Pd species was leached out into the reaction
mixture and the reaction has truly been catalyzed by the
heterogeneous system. On the other hand, TEM image of
the seventh cycle of the catalyst showed that the structure
of Pd/silica has no significant change in comparison with
fresh catalyst (Fig. S1, ESIϮ). The XRD measurements of the
recovered catalysts showed that the metallic state of
palladium was kept after the catalytic reaction Fig. S2,
(ESIϮ). Both the TEM and XRD results indicate that the
attachment between palladium nanoparticles and silica
matrix is sufficiently strong. To further evaluate the
efficiency of our catalyst, a comparison was made with the
reported heterogeneous Pd-catalysts in the Suzuki and
Heck reactions. The results for the reactions of
bromobenzene with phenylboronic acid and methyl
acrylate are listed in Table 7. It can be clearly seen that our
catalyst is superior to others in terms of reaction condition,
reaction time, and yield.
Synthesis of propargyl imidazolium bromide
The propargylimidazolium bromide was prepared according
to the literature method.37 Propargyl bromide (20.09 mmol,
80 wt% solution in toluene) was added dropwise to N-
Methylimidazole (18.27 mmol) at room temperature, and
then the reaction mixture was stirred overnight. Afterward,
the solvent was removed and the obtained product was
washed thoroughly with acetone. IR (KBr, cm−1): 3425,
3228, 3080, 2934, 2124, 1629, 1573, 1432, 1334, 1163,
1088, 1014, 850, 752, 620.
Synthesis of 3-azidopropyltrimethoxysilane
To a solution of sodium azide (0.33 g, 5 mmol) and
tetrabutylammonium bromide (TBAB, 0.32 g, 1 mmol) in
dry acetonitrile (10 mL), 3-chloropropyltrimethoxysilane
(0.92 mL, 5 mmol) was added and the mixture was refluxed
for 48 h under a nitrogen atmosphere. After that, the
solvent was removed under vacuum. The residue was then
diluted in Et2O, filtered and washed twice with Et2O.38
FT-IR (KBr, cm-1): 2948, 2870, 2840, 2100, 1469, 1356, 1259,
1091, 895, 820, 424.
Experimental
All chemical reagents were purchased from Merck Chemical
1
Company and used without further purification. H-NMR
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 6 of 11
ARTICLE
Journal Name
the reaction of aryl bromides and aryl chlorides proceeded
smoothly and the desired products were obtained in 64–
View Article Online
DOI: 10.1039/C6RA11734A
Synthesis of azide-functionalized silica
88% yields (Table 6, Entries 4–12). We also surveyed the
electronic on the yields and reaction times of the couplings.
Generally electron-poor aryl halides, in comparison to
electron-rich aryl halides, transform to the corresponding
coupled products with better conversion and shorter
reaction times. For the reaction of 4-bromoacetophenon
with metyl acrylate, elongations of the reaction times with
the decrease of the yields of the products were observed.
This result is rather unexpected.
Before immobilization, Silica-gel (60-120 mesh) (1.5 g) was
immersed in hydrochloric acid for 12 h, and washed several
times with deionized water to reach pH=7, and dried under
◦
vacuum at 120 C for 12 h. Afterward, the activated silica
was suspended in toluene (10 mL), and 3-
azidopropyltriethoxysilane was added. The solution was
refluxed for 24 h under nitrogen atmosphere.39
FT-IR (KBr, cm-1): 3419, 2927, 1639, 1098, 799, 468.
Click Reaction
Table 4 Optimization of conditions for the Heck–
Mizoroki reaction for the reaction of 4-iodoanisole and
methyl acrylate using Si–IL@Pd(0)NPs catalysta
The propargyl IL grafted silica was synthesized via click
reaction. Briefly, (1.5 g) azide functionalized silica was
dispersed in 10 mL methanol/water (1:1, V/V) solution and
propargyl IL (5 mmol, 1.5 g) was added. Then, CuSO4·5H2O
(0.08 mmol, 0.02 g) and (0.48 mmol, 0.092 g) sodium
ascorbate were added to the above solution. The mixture
was stirred for 72 h at room temperature. The completion
of the reaction was monitored by IR. Finally, the solid
particles were separated from the mixture by
centrifugation, washed several times with ethanol, HCl
solution (5% solution in water), water and acetone and
dried in vacuum at 60 oC.
Entry Solvent T(°C)
Base
Time(h)
Yieldb
1
2
3
4
5
6
7
8
9
NMP
DMF
80
80
80
80
80
80
80
rt
K2CO3
K2CO3
K2CO3
K2CO3
K3PO4
KOH
4
4
79
95
76
69
84
63
76
28
83
Toluene
EtOH
DMF
6
FT-IR (KBr, cm−1): 3430, 2925, 1637, 1100, 800, 467.
6
5
Preparation of palladium NPs
At first, silica–IL (0.25 gr) was dispersed in acetonitrile/H2O
(3:2 V/V, 20 ml). Afterward, Pd(OAc)2 (0.045 mmol, 0.01 gr)
solution was added to this solution and stirred for 5 h at
room temperature. NaBH4 solution (0.45 mmol, 0.016 g)
was then dropwise added to the above solution with
vigorous stirring. After 2 h, the catalyst was separated from
the mixture by centrifugation, washed several times with
methanol to remove unreacted Pd(OAc)2 and dried under
vacuum to obtain a black solid powder.
DMF
5
DMF
NaHCO3
K2CO3
K2CO3
5
DMF
12
5
DMF
70
a
Reaction conditions: 4-iodoanisole (0.1 mmol), methyl acrylate
(0.12 mmol), Si–IL@Pd(0)NPs catalyst 0.1 mol%, base (0.2 mmol)
b GC yield
Heck–Mizoroki Reaction
Conclusions
The palladium-catalysed Mizoroki–Heck cross-coupling
reaction has become a powerful strategy for the synthesis
of carbon–carbon bonds. In this section, we applied this
catalyst for the Heck–Mizoroki coupling reaction of a
variety of aryl halides with methyl acrylate. For this
purpose, the effect of different solvents, bases and reaction
Temperature in the presence of 10 mg of the catalyst were
surveyed for the reaction of iodoanisole with methyl
acrylate. As shown in Table 4, DMF was the most effective
solvent and K2CO3 was a suitable base for this reaction. The
model coupling reaction was also studied at different
temperatures. On the basis of this study, the quantitative
conversion and shorter reaction times can be obtained with
increasing the temperature from room temperature to 80
oC. This catalytic system was also applied to the reaction of
varieties of aryl halides with methyl acrylate. As clearly
shown in Table 6, aryl iodides are successfully converted to
the corresponding Heck products in excellent yields. Also,
The click ionic-silica supported Pd-NPs were successfully
synthesized and well characterized by different techniques.
The obtained product was then applied as solid catalyst in
the Suzuki–Miyaura and Heck–Mizoroki cross-coupling
reaction and exhibits a high catalytic activity under mild
reaction conditions. The recyclability of the catalyst was
successfully examined in the Suzuki–Miyaura reaction for
seven consecutive runs
.
Acknowledgements
We gratefully acknowledge the funding support received
for this project from the Isfahan University of Technology
(IUT), IR of Iran, and Isfahan Science and Technology Town
(ISTT), IR of Iran. Further financial support from the Center
of Excellence in Sensor and Green Chemistry Research (IUT)
is gratefully acknowledged.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 11
RSC Advances
Please do not adjust margins
Journal Name
ARTICLE
View Article Online
DOI: 10.1039/C6RA11734A
Table 5 Suzuki cross-coupling reaction of various aryl halides with phenylboronic acida
Entry
1
Ar–X
Product
Time/ h Yieldb
TONc
920
4
3
3
92
95
97
2
3
950
970
4
4.5
68
680
5
6
3.5
4.5
95
81
950
810
7
6
32
320
8
2
2
100
93
1000
930
900
1000
910
950
870
9
10
11
12
13
14
2
90
1.5
6
100
91
5
95
6
87
a
b
Reaction conditions: aryl halide (0.1 mmol), phenylboronic acid (0.12 mmol), K2CO3 (0.2 mmol), catalyst (0.1 mol%)
GC yield
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 8 of 11
ARTICLE
Journal Name
c TON: product mole /Pd mole
Table 6 Heck cross-coupling reaction of various aryl halides with methyl acrylatea
View Article Online
DOI: 10.1039/C6RA11734A
TONc
900
Entry
1
Ar–X
Product
Time/ h
3
Yieldb
90
2
4
95
950
3
4
5
3
5
5
93
82
78
930
820
780
6
7
9
5
64
88
640
880
8
9
5
6
85
79
850
790
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 9 of 11
RSC Advances
Please do not adjust margins
Journal Name
ARTICLE
View Article Online
DOI: 10.1039/C6RA11734A
10
11
12
6
6
6
73
84
71
730
840
710
a Reaction conditions: aryl halide (0.1 mmol), methyl acrylate (0.12 mmol), K2CO3 (0.2 mmol), catalyst (0.1 mol%)
b GC yield
c TON: product mole /Pd mole
Table 7
. Comparison of catalytic activity of the Si-IL@Pd(0)NPs catalyst with literature examples
for Suzuki and Heck reactions
Entry
Catalyst
conditions
Yield(%)ref
1
2
3
4
5
6
7
Silica-Pd(0) (0.1 mol% Pd)
PFG-Pd(0) (1.2 mol% Pd)
K2CO3, H2O:EtOH, 4h, 50 °C
K2CO3, H2O:EtOH, 10h, 80 °C
K2CO3, H2O, 1h, 90 °C
92 (This work)
9540
Fe3O4@PUVS-Pd (0.09 mol% Pd)
Polymer–iminophosphine- Pd (0.05 mol% Pd)
Pd@agarose–Fe3O4
9341
9542
9243
9644
K2CO3, Dioxane, 1h, reflux
K2CO3, PEG 200, 0.75h, 80°C
K2CO3, EtOH/H2O, 3h, 80 oC
K2CO3, EtOH, 6h, 80 °C
Fe3O4/P(GMA-AA-MMA-Pd) (0.2 mol% Pd)
Pd/Fe3O4@SiO2@KCC-1(0.2 mol% Pd)
90.845
8
9
Silica-Pd(0) (0.1 mol% Pd)
PFG-Pd(0) (1.7 mol% Pd)
K2CO3, DMF, 5h, 80 °C
K2CO3, DMF, 6h, 120 °C
K2CO3, H2O, 12 h, reflux
82 (This work)
8840
10
Fe3O4@PUVS-Pd (0.09 mol% Pd)
9341
Polymer –iminophosphine- Pd
11
Et3N, Dioxane, 5h , reflux
7042
(0.5 mol%)
12
13
Fe3O4/SiO2/HPG-Pd (3 mol% Pd)
NaOAc, DMF, 140 oC, 12 h
Et3N, DMF, 110 oC, 3h
6746
8547
Fe3O4/DAG/Pd
Cell–OPPh2-Pd(0) (0.1 mol% Pd)
14
Bu3N, DMF, 110 oC, 7h
8148
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 10 of 11
ARTICLE
Journal Name
32 A. R. Hajipour S. H. Nazemzadeh and F. MohVaiemwmAraticdlesaOlnelihne,
References
Tetrahedron Lett, 2014, 55, 654.
33 A. R. Hajipour, R. Pourkaveh, SynlettD, O20I:1104.,1039/C6RA11734A
25, 1101.
1
2
M. E. Davis, Top. Catal., 2015, 58, 405.
M. J. Climent, A. Corma, S. Iborra and M. J. Sabater, ACS
Catal, 2014, , 870.
34 A. R. Hajipour and F. Rafiee, Appl. Organomet. Chem.,
2015, 29, 147.
4
3
4
F. Zaera, Chem. Soc. Rev., 2013, 42, 2746.
V. Polshettiwar and R. S. Varma, Green Chem., 2010, 12
743.
35 A. Z. Wilczewska, I. Misztalewska, Organometallics, 2014,
33, 5203.
36 A. R. Hajipour, N. S. Tadayoni, Z. Khorsandi, Appl.
Organomet. Chem, 2016, 30, 590.
,
5
6
D. Habibi, A. R. Faraji, D. Sheikh, M. Sheikhi and S. Abedi,
RSC Adv., 2014, , 47625.
4
37 N. Gonsior, H. Ritter, Macromol. Chem. Phys., 2011, 212
38 Q. Zhang, H. Su, J. Luo and Y. Wei, Catal. Sci. Technol.,
2013, , 235.
.
F. Ye, S. Qu, L. Zhou, C. Peng, C. Wang, J. Cheng, M. L.
Hossain, Y. Liu, Y. Zhang and Z.-X. Wang, J. Am. Chem.
Soc., 2015, 137, 4435.
3
39 G. Zhang, Y. Wang, X. Wen, C. Ding and Y. Li, Chem.
Commun., 2012, 48, 2979.
7
8
9
S. M. McAfee, J. S. McCahill, C. M. Macaulay, A. D.
Hendsbee and G. C. Welch, RSC Adv., 2015, 5, 26097.
40 R. Fareghi-Alamdari, M. G. Haqiqi, N. Zekri, New J. Chem.
2016, 40, 1287.
V. Polshettiwar and R. S. Varma, Green Chem., 2010, 12
,
743.
41 D. Wang, W. Liu, F. Bian, W. Yu, New J. Chem. 2015, 39
,
E. Amadio, A. Scrivanti, G. Chessa, U. Matteoli, V.
Beghetto, M. Bertoldini, M. Rancan, A. Dolmella, A. Venzo
and R. Bertani, J. Organomet. Chem., 2012, 716, 193.
2052.
42 X. Liu, X. Zhao, M. Lu, J. Organomet. Chem., 2014, 768
,
23.
10 K.V. Ranganath, S. Onitsuka, A.K. Kumar and J. Inanaga,
Catal. Sci. Tech., 2013, , 2161.
11 Y. Xu, Z. Zhang, J. Zheng, Q. Du and Y. Li, Appl.
Organomet. Chem., 2013, 27, 13.
43 H. Firouzabadi, N. Iranpoor, M. Gholinejad, S. Akbari, N.
3
Jeddi, RSC Adv., 2014, 4, 17060.
44 D. Z. Yuan and H. P. Zhang, Appl. Catal., A, 2014, 475, 249.
45 X. Le, Z. Dong, Y. Liu, Z. Jin, T.-D. Huy, M. Le, J. MaJ.
12 C. Ornelas, J. Ruiz, L. Salmon and D. Astruc, Adv. Synth.
Catal., 2008, 350, 837.
Mater. Chem. A, 2014, 2, 19696.
46 L. Zhou, C.Gao andW. J. Xu, Langmuir, 2010, 26, 11217.
47 H. Veisi, J. Gholami, H. Ueda, P. Mohammadi, M. Noroozi,
J. Mol. Catal. A: Chem. 2015. 396, 216.
13 R.L. Oliveira, W. He, R.J.K. Gebbink and K.P. de Jong,
Catal. Sci. Tech., 2015, 5, 1919.
14 D. Sahu and P. Das, RSC Adv., 2015,
15 S. Bahadorikhalili, L. Ma’mani, H. Mahdavi and A. Shafiee,
RSC Adv., 2015, , 71297.
5, 3512.
48 Q. Du and Y. Li, Res. Chem. Intermed., 2012, 38, 1807
5
16 H. Veisi, A. Sedrpoushan and S. Hemmati, Appl.
Organomet. Chem., 2015, 29, 825.
17 E. Nehlig, B. Waggeh, N. Millot, Y. Lalatonne, L. Motte and
E. Guénin, Dalton Trans., 2015, 44, 501.
18 M. Meldal and C. W. Tornøe, Chem. Rev., 2008, 108
,
2952.
19 H. C. Kolb, M. Finn and K. B. Sharpless, Angew. Chem. Int.
Ed., 2001, 40, 2004.
20 Z. Cai, B. T. Li, E. H. Wong, G. R. Weisman and C. J.
Anderson, Dalton Trans., 2015, 44, 3945.
21 H. C. Kolb and K. B. Sharpless, Drug discovery today, 2003,
8
, 1128.
22 A. R. Hajipour and F. Abrishami, J. Appl. Polym. Sci., 2012,
124, 1757.
23 Q. Zhang, H. Su, J. Luo and Y. Wei, Catal. Sci. Tech., 2013,
3
, 235.
24 E. Mieczyńska, T. Borkowski, M. Cypryk, P. Pospiech and
A. Trzeciak, Appl. Catal. A: Gen, 2014, 470, 24.
a) B. Helms, J.L. Mynar, C.J. Hawker, J.M. Fréchet, J. Am.
Chem. Soc., 2004, 126, 15020; b) M. Munteanu, S. Choi, H.
Ritter, Macromolecules, 2008, 41, 9619; c) E. Díez-Barra, J.
Guerra, V. Hornillos, S. Merino, J. Tejeda,
Organometallics, 2003, 22
, 4610; d) D. Maity, T.
Govindaraju, Chem. Commun., 2010, 46, 4499.
a) P.L. Golas, K. Matyjaszewski, Chem. Soc. Rev., 2010, 39
1338; b) Y. He, C. Cai, Chem. Commun., 2011, 47, 12319.
,
25 M.-J. Jin, A. Taher, H.-J. Kang, M. Choi and R. Ryoo, Green
Chem., 2009, 11, 309.
26 Z. Wang, Q. Zhang, D. Kuehner, X. Xu, A. Ivaska and L.
Niu, Carbon, 2008, 46, 1687-1692.
29 D. Zhang, C. Zhou and R. Wang, Catal. Commun., 2012,
22, 83-88.
30 L. Li, J. Wang, T. Wu and R. Wang, Chem. Eur. J., 2012,
18, 7842-7851.
31 A. R. Hajipour and F. Mohammadsaleh, Tetrahedron Lett.,
2014, 55, 3459.
10 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 11 of 11
RSC Advances
Please do not adjust margins
Journal Name
ARTICLE
View Article Online
DOI: 10.1039/C6RA11734A
The synthesis of silica-grafted palladium catalyst through
‘‘click’’ reaction of azide-functionalized silica with
methylpropargylimidazolium bromide, for Heck and Suzuki–
Miyaura coupling reactions.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 11
Please do not adjust margins