Anchoring of palladium (II) in functionalized SBA-16: An efficient heterogeneous catalyst for Suzuki coupling reaction

Article abstract of DOI:10.1016/j.molcata.2013.01.012

A new functionalized SBA-16 catalyst immobilized palladium (II) has been synthesized. Inductively coupled plasma (ICP), small-angle X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen physical adsorption and Fourier transform infrared (FTIR) studies have been used to characterize the catalyst. The catalyst exhibited very high activity for Suzuki coupling reaction of aryl halides with arylboronic acids in EtOH/water under air atmosphere. On the other hand, the synthesized catalyst could be separated from the reaction mixture by simple filtration and reused up to five runs without significant loss in activity.

Full text of DOI:10.1016/j.molcata.2013.01.012

Journal of Molecular Catalysis A: Chemical 370 (2013) 175–181
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Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Anchoring of palladium (II) in functionalized SBA-16: An efficient heterogeneous
catalyst for Suzuki coupling reaction
Shuoyun Wei, Zongyan Ma, Peng Wang, Zhengping Dong, Jiantai Ma∗
The Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000,
China
a r t i c l e i n f o
a b s t r a c t
Article history:
A new functionalized SBA-16 catalyst immobilized palladium (II) has been synthesized. Inductively cou-
pled plasma (ICP), small-angle X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen
physical adsorption and Fourier transform infrared (FTIR) studies have been used to characterize the cata-
lyst. The catalyst exhibited very high activity for Suzuki coupling reaction of aryl halides with arylboronic
acids in EtOH/water under air atmosphere. On the other hand, the synthesized catalyst could be sepa-
rated from the reaction mixture by simple filtration and reused up to five runs without significant loss
in activity.
Received 22 October 2012
Received in revised form 6 January 2013
Accepted 7 January 2013
Available online 26 January 2013
Keywords:
Palladium
Heterogeneous catalyst
Schiff-base
© 2013 Elsevier B.V. All rights reserved.
SBA-16
Suzuki reaction
1. Introduction
diatomite [21], dendrimers [22,23], magnetic nanoparticles [24],
mesoporous silica [25–27], polymeric microspheres, microcapsules
Palladium is the most versatile and widely applied metal for the
catalysis of various carbon–carbon bond forming reactions. Of these
reactions, the palladium-catalyzed Suzuki cross-coupling reaction
has become an extremely powerful synthetic method for prepar-
ing biaryl compounds, which constitute a wide range of natural
products, agrochemicals, pharmaceuticals, and advanced materials
[1–6]. The organoboronic acids commonly employed in the Suzuki
reaction, which are nontoxic and thermally, air-, and moisture-
stable. Typically, the reaction is catalyzed by soluble palladium
complexes including different phosphorous or nitrogen-based as
well as ligand-free palladium [7–10]. Although homogeneous cat-
alysts frequently exhibit very high activity, the drawbacks of these
catalysts are apparent. For example, homogeneous palladium cat-
alysts are usually not reusable and the products are frequently
contaminated by residual palladium or ligands [11]. To overcome
these problems, it is highly desirable to develop new efficient and
recyclable heterogeneous catalysts for Suzuki reaction. Therefore,
the heterogenization of palladium catalyst is a promising option
[12,13].
and resin [28–30]. However, some heterogeneous palladium cata-
lysts show lower reactivity than homogeneous ones due to leaching
of palladium from the supports. In fact the leached palladium
species is responsible for the catalytic activity in most of the cases
[31–33]. Thus, there is a need to design of new heterogeneous cata-
lysts that can retain the activities and selectivities of homogeneous
catalysts. Now it is well known that the nature of supports plays
a key role in palladium-based heterogeneous catalysis. Among
different supports, mesoporous silica materials remain the most
popular choice because of their relatively low cost, high thermal,
mechanical stability and good catalytic performance [34]. SBA-15
and MCM-41 are the representative example for these types of
materials and have been used as supports for palladium catalysts
[35–37].
Recently, Molnar et al. [38] observed that palladium immobi-
lized on silica modified with methyl or phenyl groups exhibited
high activity and selectivity in the Heck reaction. So the choice
of ligand for functionalization of mesoporous silica has an impor-
tant effect on the catalytic activity and stability. In this context,
nitrogen-containing ligands have received much attention owing
to their ability to form various stable complexes with palladium,
possible extended supramolecular systems and good properties.
Dhara et al. [39] reported the palladium (II)–Schiff base complex
anchored onto MCM-41 which showed high reactivity and recy-
clability for the Suzuki reaction. Compared with two-dimensional
channel-like hexagonal mesoporous materials such as MCM-41 and
In recent years, many reports have appeared on Suzuki coupling
catalyzed by supported palladium catalysts, which are loaded on
activated carbon [14–16], zeolites and molecular sieves [17–20],
∗
Corresponding author. Tel.: +86 0931 8912311; fax: +86 0931 891 2582.
E-mail address: majiantai@lzu.edu.cn (J. Ma).
1381-1169/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2013.01.012

176
S. Wei et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 175–181
Scheme 1. Preparation of the catalyst Pd (II)–SBA-16.
SBA-15, SBA-16 has been found to be more attractive due to the
three-dimensional cage-like mesoporous network (in which each
spherical cage is connected with eight neighboring cages through
entrances) [40,41]. Such a unique pore structure of SBA-16 has been
proven to facilitate the fast diffusions of reaction molecules [42].
Considering that SBA-16 support has a three-dimensional cage-like
pore structure and the catalytic palladium species is anchored onto
the inner surface of the mesoporous material, we expect that SBA-
16 supported palladium catalyst will exhibit high activity, stability
and good reusability. Up to date, there exist a few reports on SBA-16
supported palladium catalysts that have been applied to the Suzuki
reactions [27].
the solution was magnetically stirred at 35 ◦C for 4 h. And then
5.6 mL of tetraethylorthosilicate was added dropwise to the solu-
tion. After being magnetically stirred for 40 min, the suspension
was transferred into a Teflon autoclave. The autoclave was placed
under static conditions at the same temperature for 24 h. Subse-
quently, the temperature of the autoclave was raised up to 100 ◦C
and kept at that temperature for 32 h. After the hydrothermal treat-
ment, the precipitated solid was isolated by filtration, dried in air
at room temperature, and yielding white powders. The products
were calcined at 550 ◦C for 10 h to remove the templates. Thus, the
final mesoporous silica material was obtained.
In this paper, we explore the synthesis (Scheme 1) of a new
palladium(II) bound heterogeneous catalyst through functional-
ization of 3D-hexagonally ordered SBA-16 type material with
3-aminopropyltriethoxysilane followed by the grafting with 2-
acetylpyridine. This functionalized mesoporous material acts as an
effective palladium catalyst for the Suzuki reaction.
2.3. Preparation of the 3-APTES functionalized SBA-16
Mesoporous material (SBA-16) (1 g) was added to a solution
of 3-aminopropyltriethoxysilane (1.8 g) in toluene (150 mL) and
refluxed for 24 h under N2 atmosphere. The white solid was fil-
tered and washed repeatedly with ethanol, and finally dried at 50 ◦C
under vacuum.
2. Experimental
2.4. Grafting of 2-acetylpyridine on functionalized SBA-16
2.1. Materials
The 3-APTES functionalized SBA-16 (1 g) was added to the solu-
tion of 2-acetylpyridine (1.0 g) in methanol (25 mL) at 60 ◦C for 8 h.
The resulting solid was collected by filtration, repeatedly washed
with ethanol to remove unreacted 2-acetylpyridine. It was dried at
50 ◦C under vacuum.
Pluronic P123 (EO20PO70EO20) and F127 (EO106PO70EO106) were
purchased from Sigma–Aldrich. 3-Aminopropyltriethoxysilane
was obtained from Alfa Aesar. PdCl2 (99%) and 2-acetylpyridine
were obtained from Lanzhou Aihua Chemical Reagent Company.
Arylboronic acids, aryl halides were purchased from Shanghai
Chemical Reagent Company. Tetraethoxysilane and other reagents
were obtained from Tianjin Guangfu Fine Chemical Research Insti-
tute. All solvents were of analytical grade and used without further
purification. Deionized water was used in the present study.
2.5. Synthesis of the Pd (II)–SBA-16 catalyst
The catalyst was prepared by stirring a mixture of modified
mesoporous silica (1 g) and palladium chloride (0.05 g) in ethanol
(50 mL) at room temperature for 24 h. After stirring, the catalyst
was filtered, washed several times with ethanol and dried under
vacuum at 50 ◦C.
2.2. Synthesis of SBA-16
Mesoporous material SBA-16 was synthesized according to the
procedure described elsewhere [43,41]. A mixture of Pluronic F127
(1.484 g) and P123 (0.238 g) were used as the templates. The mixed
templates were completely dissolved in a solution of 60 mL of
deionized water and 10.5 g of concentrated hydrochloric acid (36%),
2.6. Catalytic Suzuki reactions
In a typical procedure, aryl halide (0.5 mmol), phenylboronic
acid (0.75 mmol), K2CO3 (1.0 mmol), EtOH/H2O (v/v = 9:1, 5.0 mL)

S. Wei et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 175–181
177
and catalyst (0.5 mol% Pd) were added in a 10 mL round bottom
flask. The mixture was vigorously stirred at 80 ◦C for required time
under air atmosphere. After the completion of the reaction, the mix-
ture was cooled to room temperature and filtered. The filtrate was
extracted with ethyl acetate (2× 5 mL). The combined extracts were
dried with Na2SO4, filtered and analyzed by GC (P.E. AutoSystem
XL) or GC–MS (Agilent 6890 N/5973 N).
2.7. Catalyst recycling in Suzuki reaction
A
mixture of aryl iodide (0.5 mmol), phenylboronic acid
(0.75 mmol), K2CO3 (1.0 mmol), EtOH/H2O (v/v = 9:1, 5.0 mL) and
the catalyst (0.5 mol% Pd) was stirred at 80 ◦C under air atmosphere.
At the end of reaction, the mixture was cooled to room temperature
and filtered to obtain the palladium catalyst. The separated catalyst
was washed with ethanol and dried under vacuum at 50 ◦C. After
this, it could be used for the next run.
2.8. Characterization
Fig. 1. Small angle XRD patterns of (a) SBA-16 and (b) Pd (II)–SBA-16.
The Pd content of catalyst was measured by inductively cou-
pled plasma (ICP) on IRIS Advantage analyzer. Small-angle powder
X-ray powder diffraction was performed on a Rigaku D/max-2400
diffractometer using Cu-Ka radiation as the X-ray source in the 2q
range of 0.5–5◦. The morphology and microstructure of the meso-
porous material were observed by a Tecnai G2 F30 transmission
electron microscopy and samples were obtained by placing a drop
of a colloidal solution onto a copper grid and evaporating the sol-
vent in air at room temperature. The BET surface area and pore-size
distribution were obtained by measuring N2 adsorption isotherms
at 77 K by using a TriStar 3020 (Micromeritics). Fourier transform
infrared spectra were collected on a Nicolet NEXUS 670 FTIR spec-
trometer with a DTGS detector, and samples were measured with
KBr pellets.
structure. Comparison of the diffraction patterns of Pd (II)–SBA-16
and SBA-16 indicates that the ordered cubic mesoporous struc-
ture of the material remains intact even after formation of the Pd
complex in SBA-16 matrix. An overall decrease in the intensity of
the peaks is observed after bound with Pd (II)–complex. This is
attributed to the presence of guest moieties on the mesoporous
framework of SBA-16, resulting in the decrease of crystallinity but
not collapse of the pore structure of mesoporous materials [44].
Fig. 2 shows the TEM images of SBA-16, Pd (II)–SBA-16 and
Pd (II)–SBA-16 after five runs. For fresh SBA-16 (Fig. 2a), the
highly ordered arrangements of mesopores reveal that the mate-
rial consists of a high-quality body-centered cubic mesostructure.
In Fig. 2b, Pd (II)–SBA-16 presents a well-ordered mesopores struc-
ture characteristic of the SBA-16 material, which indicates that the
mesostructure of SBA-16 can be substantially conserved after the
grafting process.
3. Results and discussion
3.1. Catalyst preparation and characterization
In order to obtain the structural information about the solid cat-
alyst on a mesoscopic scale, the N2 sorption isotherms and pore
size distribution plots for SBA-16 and Pd (II)–SBA-16 are displayed
in Figs. 3 and 4 respectively. SBA-16 exhibits a type IV isotherm
with a steep capillary condensation/evaporation step and a type
H2 hysteresis loop, which is characteristic of the mesoporous cage-
like structure. Similar to the parent SBA-16, Pd (II)–SBA-16 also
shows a type-IV isotherm with an H2 hysteresis loop, indicat-
ing that the catalyst still maintains a good mesoporous cage-like
structure. The BET surface area and pore volume of SBA-16 is
The immobilization of Pd (II) in chemically modified SBA-16
consists of the following steps as shown in Scheme 1. The con-
tent of Pd in the catalyst determined by inductive coupled plasma
emission spectrometer (ICP) was 2.18 wt%.
The small-angle X-ray diffraction patterns of SBA-16 and the
catalyst Pd (II)–SBA-16 are shown in Fig. 1. The fresh SBA-16 shows
a strong diffraction peak and two small diffraction peaks for the
110, 200 and 211 planes. All the peaks indicate SBA-16 has a
well defined hexagonal symmetry and has long-range ordering of
Fig. 2. TEM images of (a) SBA-16, (b) Pd (II)–SBA-16 and (c) Pd (II)–SBA-16 after five runs.

178
S. Wei et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 175–181
Fig. 3. N2 adsorption-desorption isotherms of (a) SBA-16 and (b) Pd (II)–SBA-16.
Fig. 5. FT-IR spectra of (a) SBA-16, (b) 3-APTES-SBA-16, (c) Schiff base-SBA-16, (d)
Pd (II)–SBA-16 and (e) Pd (II)–SBA-16 after five runs.
2-acetylpyridine, the BET surface area decreased by 624 m2g−1
,
which was close to the value of 798 m2g−1 for a similarly prepared
mesoporous catalyst by Dhara et al. [39]. This can be attributed to
the more loading of organics, which occupy the void space inside
the mesopores.
Fig. 5 shows the FT-IR spectra of SBA-16 (a), 3-APTES-SBA-16 (b),
Schiff base-SBA-16 (c), Pd (II)–SBA-16 (d) and Pd (II)–SBA-16 after
five runs (e). The spectrum of parent SBA-16 exhibits a broad band
at 1633 cm−1 due to O H bending vibration. C H and N H vibra-
tion bands in the 3100–2800 cm−1 and 1650–1500 cm−1 regions
are found in the IR spectra of the 3-APTES-SBA–16, and these bands
are surely absent in SBA-16. Meanwhile, the intensity of the peak at
960 cm−1 (related to the bending vibration of Si–OH on SBA-16) sig-
nificantly decreases after grafting with 3-APTES. This result shows
that 3-APTES has been attached into the SBA-16 matrix. Interest-
ingly, after 2-acetylpyridine treatment, one change in the spectra
has been noticed, the O H band at 1628 cm−1 merges with a new
broad band centered at 1640 cm−1 attributable to the C N stretch-
ing of imine generated through Schiff base condensation between
amine group of 3-APTES and carbonyl group of 2-acetylpyridine.
Thus it is evident that the acetyl groups are converted into Schiff
base. In Fig. 5(d), the C N stretching frequency is shifted to lower
frequency (1632 cm−1) indicate to form Pd complex. The stretching
frequency at 576 cm−1 in the spectrum of Pd (II)–SBA-16 indicates
ꢀPd–N [45].
Fig. 4. Pore size distributions of (a) SBA-16 and (b) Pd (II)–SBA-16.
700 m2g−1 and 0.64 ccg−1, whereas for Pd (II)–SBA-16, this value
decrease to 76 m2g−1 and 0.10 ccg−1, respectively. It is worthwhile
to note that the surface area, pore volume and pore size of the
Pd (II)–SBA-16 undergo a drastic reduction. During functionaliza-
tion via 3-aminopropyltriethoxysilane and later grafting by the
Table 1
Optimisation of the reaction conditions.a
Pd ( )-SBA-16, K2CO3
B(OH)2
I
Entry
Catalyst(mol%)
Solvent
Temp(◦C)
Time(h)
Yield(%)b
1
2
3
4
5
6
0.5
0.5
0.5
0.5
1.0
0.1
0.5
0.5
0.5
0.5
0.5
0.5
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
MeOH
DMF
Toluene
H2O
MeOH/H2O (v/v = 9:1)
EtOH/H2O (v/v = 9:1)
40
60
80
80
80
80
80
80
80
80
80
80
2.5
2.5
2.5
4
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
64
83
97
97
97
59
98
62
53
27
100
100
8
9
10
11
12
aReaction condition: iodobenzene (0.5 mmol), phenylboronic (0.75 mmol), K2CO3 (1.0 mmol), solvent (5.0 ml), Pd (II)–SBA-16 catalyst (0.1–1.0 mol%), and 40–80 ◦C.
bYield was determined by GC analysis.

S. Wei et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 175–181
179
Table 2
The Suzuki reaction of aryl halides with arylboronic acids using Pd (II)–SBA-16 catalyst.a
Pd ( )-SBA-16, K2CO3
X
B(OH)2
R1
R2
R1
R2
EtOH/H2O
Entry
Aryl halide
Arylboronic acid
Product(s)
Time/h
2.5
Yield(%)b
I
B(OH)2
B(OH)2
1
2
100
98
I
3
3
B(OH)2
3
97
I
I
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
H3CO
H3CO
4
5
6
3
96
98
93
H3COC
I
H3COC
2.5
6
Br
Br
7
8
81
92
95
93
97
99
H3COC
H2N
Br
H3COC
H2N
8
3
Br
9
8
O2N
Br
O2N
10
11
12
3
I
B(OH)2
B(OH)2
2.5
3
I
B(OH)2
13
3
95
I
I
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
H3CO
H3CO
14
15
16
17
18
19
20
3
94
99
91
84
96
90
95
H3COC
I
H3COC
2.5
6
Br
Br
8
H3COC
Br
H3COC
H2N
3
H2N
O2N
Br
Br
8
O2N
3

180
S. Wei et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 175–181
Table 2 (Continued)
Pd ( )-SBA-16, K2CO3
X
B(OH)2
R1
R2
R1
R2
EtOH/H2O
Entry
Aryl halide
Arylboronic acid
Product(s)
Time/h
12
Yield(%)b
28
Cl
B(OH)2
21
aReaction condition: aryl halide (0.5 mmol), arylboronic acid (0.75 mmol), K2CO3 (1.0 mmol), EtOH/H2O (5.0 ml, v/v = 9:1), Pd (II)–SBA-16 catalyst (0.5 mol%), and 80 ◦C.
bYield was determined by GC analysis.
3.2. Catalytic Suzuki coupling reaction
was observed a moderate yield with relatively longer time (entries
7 and 17), this phenomenon was probably due to the electronic and
steric effects of the substitutent. Usually, the electron-withdrawing
substitutent is generally more active than the electron- donating
substitutent (such as CH3). Although, aryl bromides and iodides
were found to be very effective substrates, unfortunately, we
prepared catalyst has failed to produce biaryl compounds when
chlorobenzene was used as substrate (entry 21). The low reactiv-
ity of chlorides was resulted from the strength of the C Cl bond,
whose bond dissociation energy was 96 kcal/mol [46]. Recently,
Dhara et al. [39] investigated the immobilization of Pd (II) on
amine-functionalized MCM-41 which showed high reactivity for
the Suzuki reaction of aryl bromide. It was noteworthy that we
prepared catalyst exhibited very high activity for Suzuki coupling
reaction not only with aryl bromide but also with aryl iodide. Mean-
while, contrary to our environmentally friendly aqueous-alcoholic
media under air atmosphere, the reported catalyst was used in DMF
medium at higher temperature (100 ◦C) under argon atmosphere
and it has been established that leaching of Pd often occurs in
To test the catalytic activity of Pd (II)–SBA-16 in the Suzuki reac-
tion, the reaction between iodobenzene and phenylboronic acid
was chosen as model reaction using K2CO3 as base. Influences of
different parameters were examined to obtain the best possible
combination. The parameters included solvent, reaction temper-
ature, catalyst concentration and the reaction period. As shown
in Table 1, the coupling reaction yields were susceptible to tem-
perature changes in the presence of 0.5 mol% catalyst and EtOH as
solvent (entries 1–3). The increase of reaction temperature up to
80 ◦C led to excellent yields (97%). After 2.5 h heating, the good
yields were given in the presence of 1.0 mol% catalyst at 80 ◦C
(entry 5), when the loading of catalyst was decreased to 0.1 mol%,
the yield were observed to be very slow (entry 6). The effect of
various solvents was next investigated. While protic solvents like
EtOH or MeOH were used as solvent, almost quantitative product
formation was obtained after 2.5 h (entries 3 and 7), the aprotic sol-
vents such as toluene, DMF gave low yields during the same time
(entries 8 and 9). Interestingly, when H2O was used as the solvent
only poor yield was obtained (entry 10). Comparing with these sol-
vents, the organic/aqueous mixture as reaction solvent provided
much better yields (entries 11 and 12). The merit of the co-solvent
was attributed to the good solubility of the organic reactants and
the inorganic base. Based on the reaction yields and environmen-
tal consideration, the EtOH/H2O (v/v = 9:1) combination was the
best solvent for Suzuki reaction. Therefore, the following condi-
tion was used for the Suzuki coupling: 0.5 mol% of Pd (II)–SBA-16
catalyst, 1.0 equiv. of K2CO3 in EtOH/H2O at a temperature of
80 ◦C.
Under the optimized reaction conditions, the scope of the
reaction was explored with various aryl halides and arylboronic
acids. As shown in Table 2, the coupling of aryl iodides proceeded
smoothly at 80 ◦C and the corresponding products were obtained
high yields (entries 1–5 and 11–15). We further investigated the
catalytic activity for the coupling of aryl bromides, aryl bromides
and their derivatives efficiently reacted with phenylboronic acid or
4-methylphenylboronic acid, to yield biphenyls in excellent yields
(entries 6–10 and 16–20). It could be concluded that aryl iodides
bearing an electron-donating or electron-withdrawing group were
obtained excellent yields. Meanwhile, for aryl bromides with sub-
stituents such as COCH3, NH2 and NO2, moderate to high
yields were achieved. However, the reaction of 4-bromotoluene
C
C coupling reaction if DMF is used as a solvent [47]. More-
over, the catalytic activity of the reported catalyst was significantly
decreased after the second run, although a satisfactory yield was
finally obtained with longer reaction time (10 h) in the second run.
Compared with their report, our catalyst showed excellent catalytic
activity even after five times of recycling under the same reaction
time.
The recyclability of Pd (II)–SBA-16 was further studied because
the recycling of the heterogeneous catalyst was an important issue
for practical applications. The coupling reaction of iodobenzene
with phenylboronic acid was chosen as the model reaction. As
shown in Table 3, the recovered catalyst was added to reaction
mixture under the same conditions for five cycles without a signif-
icant loss of yield and catalytic activity. Metal leaching was studied
by ICP analysis of the catalyst after the reaction. The Pd content
(2.06 wt%) of the recovered catalyst remained just about the same
as the fresh catalyst, indicating that Pd leaching was negligible. Fur-
thermore, the filtrate obtained from the filtration of the catalyst
after catalysis did not exhibit any catalytic activity. As was shown
in Fig. 5e, the FT-IR spectrum of Pd (II)–SBA-16 after five runs still
kept the characteristic peaks compared with that of fresh catalyst.
From the TEM images (Fig. 2c), it can be seen that the cage-like
structure of the reused catalyst did not have an obvious change.
The good reusability may be attributed to the isolated nanocages
Table 3
Reusability of the Pd (II)–SBA-16 catalyst for the Suzuki reaction.a
Pd ( )-SBA-16, K2CO3
B(OH)2
I
EtOH/H2O, 80 oC
Run
1
2
3
4
5
Yield at 2.5 h (%)b
100
96
96
98
94
a
Reaction condition: iodobenzene (0.5 mmol), phenylboronic (0.75 mmol), K2CO3 (1.0 mmol), EtOH/H2O (5.0 ml, v/v = 9:1), Pd (II)–SBA-16 catalyst (0.5 mol%), and 80 ◦C.
Yield was determined by GC analysis.
b

S. Wei et al. / Journal of Molecular Catalysis A: Chemical 370 (2013) 175–181
181
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4. Conclusions
In conclusion, a new mesoporous silica supported palladium
(II) catalyst had been successfully prepared via sequential graft-
ing of several organic molecules. The catalyst has shown high
activity towards Suzuki coupling reaction. It could be easily recov-
ered by simple filtration and a good yield was obtained even after
the catalyst was reused five times. These advantages make this
methodology attractive for the development of large-scale indus-
trial synthesis.
Acknowledgement
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This work was supported financially by the Key Laboratory
of Nonferrous Metals Chemistry and Resources Utilization, Gansu
Province.
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