Room-temperature Suzuki-Miyaura reaction catalyzed by palladium nanoparticles in lactate-anion ionic liquid

Article abstract of DOI:10.1002/cjoc.201400497

A palladium nanoparticle catalyst (PdNPs[Bmim]Lac) has been prepared by a simple, mild and efficient chemical approach using 1-butyl-3-methylimidazolium lactate ([Bmim]Lac) ionic liquid) as a stabilizer. This catalyst exhibits excellent activity, stability, recyclability and simple manipulation in Suzuki-Miyaura reactions at room temperature in air.

Full text of DOI:10.1002/cjoc.201400497

FULL PAPER
DOI: 10.1002/cjoc.201400497
Room-Temperature Suzuki-Miyaura Reaction Catalyzed by
Palladium Nanoparticles in Lactate-Anion Ionic Liquid
Furong Wang, Sisi Tang, Hao Ma, Lefu Wang, Xuehui Li,* and Biaolin Yin*
School of Chemistry and Chemical Engineering, State Key Laboratory of Pulp and Paper Engineering of China,
South China University of Technology, Guangzhou, Guangdong 510640, China
A palladium nanoparticle catalyst (PdNPs@[Bmim]Lac) has been prepared by a simple, mild and efficient
chemical approach using 1-butyl-3-methylimidazolium lactate ([Bmim]Lac) ionic liquid) as a stabilizer. This cata-
lyst exhibits excellent activity, stability, recyclability and simple manipulation in Suzuki-Miyaura reactions at room
temperature in air.
Keywords palladium nanoparticles, room temperature, Suzuki-Miyaura reaction, lactate anion, ionic liquid
Introduction
bility to hydrolysis with the formation of corrosive
[
10]
HF.
Furthermore, most Suzuki-Miyaura reactions in
The palladium-catalyzed Suzuki-Miyaura coupling
reaction is one of the most powerful tools for the forma-
tion of C－C bonds in preparing biaryl compounds,
such as natural products, pharmaceuticals, and poly-
ILs typically require an inert atmosphere or elevated
[11]
temperature with limited substrate scope.
From the
economic and environmental aspect, ambient tempera-
ture catalysis has become high importance, considering
both needs for low cost energy and thermal instability of
[
1]
mers. Palladium nanoparticles (PdNPs) are attracting
much interest due to their enhanced catalytic activity
that arises from their high surface area and rotational
degrees of freedom caused by their nanoscale dimen-
[12]
substrates. Thus, there is an urgent need for the de-
velopment of highly active nanocatalysts stabilized by
halogen-free anions ILs which can catalyze Suzuki-
Miyaura reaction under mild reaction condition.
[
2]
sions. Nevertheless, PdNPs show a tendency for
self-agglomeration, resulting in a decrease of catalytic
[3]
In this context, we report herein the desired prepara-
tion of a 1-butyl-3-methylimidazolium-lactate IL-stabi-
lized PdNPs catalyst (PdNPs@[Bmim]Lac), which
shows high activity in catalyzing the Suzuki-Miyaura
reaction at room temperature (r.t.) in air. Lactate was
selected as the anion of the IL on the basis of following
considerations. First, the naturally-occurring lactate an-
ion is non-toxic and pharmaceutically acceptable, and
activity during reaction processes. To circumvent this
problem, one of the most attractive methods is currently
the preparation of PdNPs in the presence of stabilizers.
Ionic liquids (ILs) have emerged as important stabiliz-
ing and recyclable agents for metal NPs, simultaneously
avoiding the use of highly toxic solvents. Hence, tran-
sition metal NPs stabilized by ILs have been extensively
employed for hydrogenation, oxidation, C－C coupling
[4]
[5]
[
13]
[
6]
remains inactive toward microorganisms. Second, the
electron-donating hydroxyl and carboxyl groups of the
lactate anion are able to interact with surface metal at-
reactions, and so on. For instance, ILs with imida-
zolium cations displaying a high degree of 3-D struc-
tural organization have been used as “entropic drivers”
[5b]
(
the so-called IL effect) for the preparation of a plethora
oms, thus further stabilizing PdNPs.
Third, the hy-
of well-defined and extensively ordered nanoscale
droxyl group of the lactate anion might be helpful for
the formation of monodisperse PdNPs showing en-
hanced dispersibility in protic solvents.
[7]
structures. Meanwhile, the anionic component of an
IL is also an important factor with regard to controlling
[
8]
of the size and shape of PdNPs. To date, halo-
gen-anion ILs have been predominantly adopted as sta-
bilizers for the preparation of metal NP catalysts for
Experimental
[9]
General
reactions such as Suzuki-Miyaura coupling. However,
halides are the most common and persistent contami-
nants to environment. For example, fluorinated-anion
ILs display high cytotoxicity due to their high suscepti-
Palladium acetate [Pd(OAc) , w(Pd)＝47.5%, reagent
2
grade], methanol (HPLC grade) and ethanol (anhydrous)
were obtained from Acros (Belgium). [Bmim]Lac,
*
E-mail: cexhli@scut.edu.cn, blyin@scut.edu.cn; Tel.: 0086-020-87114707; Fax: 0086-020-87114707
Received July 23, 2014; accepted September 29, 2014; published online XXXX, 2014.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201400497 or from the author.
Chin. J. Chem. 2014, XX, 1—8
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1

Wang et al.
FULL PAPER
1
-butyl-3-methylimidazolium acetate ([Bmim]CH
3
COO),
hydrous Na
2
SO
4
overnight, filtered and the hexane was
1
-butyl-3-methylimidazolium propionate ([Bmim]C
2
H
5
-
removed by a rotary evaporator. The products were fur-
ther purified by recrystallization with ethanol. The iden-
tification was conducted by H, C NMR and GC-MS
analysis (see Supporting Information).
COO), 1-butyl-3-methylimidazolium tetrafluoroborate
1
13
([Bmim]BF
4
) and 1-butyl-3-methylimidazolium glycolate
COO) ( ＞99%, reagent grade) were
([Bmim]HOCH
2
purchased from Chengjie Co., Ltd (Shanghai, China).
Aryl halides (reagent grade) and arylboronic acids (re-
agent grade) were from Darui Co., Ltd (Shanghai, China).
Other reagents (analytic grade) were purchased from
Guangzhou Reagent Factory (Guangzhou, China). All
chemicals were used as received without further purifica-
tion.
Recyclability of the catalyst
The recyclability of the catalytic system was inves-
tigated by choosing the coupling of 4-bromoanisole
with phenylboronic acid as a model reaction. After one
run, the reaction mixture was extracted by hexane (15
mL×3) after the removal of the solvent by a rotary
evaporator. Then, the resulting residual mixture was
used for the next run.
UV-vis absorption measurement (UV/Vis) spectra
were obtained on a Shimadzu UV-2450 spectropho-
tometer using methanol as solvent. The transmission
electron microscopy (TEM) micrographs were recorded
Results and Discussion
TM
on a Tecnal G2 F30 transmission electron microscope
Characterization of PdNPs@[Bmim]Lac
at 300 kV. Samples were prepared by directly dropping
the mixture of PdNPs and IL/ethanol solution onto car-
bon-coated Cu grids. X-Ray diffraction (XRD) analysis
was performed in a Bruke D8 advance by using Cu Kα
radiation (λ＝0.15418 nm) and operating at 40 kV and
The reduction progress of Pd(II) ion to Pd(0) in the
preparation of PdNPs@[Bmim]Lac was confirmed by
UV/Vis absorption measurement (Figure 1). UV/Vis
absorption spectra show two characteristic absorption
peaks at 249 and 380 nm before reduction, correspond-
4
0 mA. X-Ray photoelectron spectroscopy (XPS)
[14]
measurements were carried on a Thermo Scientific Es-
calab 250 spectrometer by using non-monochromatic Al
Kα radiation and C1s (284.8 eV) as the internal standard.
The mixture of PdNPs and IL was coated on the glass
slice for XPS and XRD analysis after the removal of
ethanol by a rotary evaporator at r.t. Melting points
were recorded on an Electrothermal X6 microscopic
digital melting point apparatus. Products of Suzuki-
Miyaura reactions were analyzed by NMR (Bruker
ing to the absorbances of imidazolium ring of IL and
[15]
Pd(II) ions. With the reduction proceeding, the peak
at 380 nm reduced gradually but the absorbance in-
creased due to the enhancement of surface plasmon
[16]
scattering.
The peak at 380 nm disappeared com-
pletely and a broad continuous absorption was observed,
indicating complete reduction of Pd(II) ions to Pd(0).
[17]
6
DRX 400 MHz instrument; DMSO-d as solvent and
TMS as the internal standard) and gas chromatography-
mass spectrometry (GC-MS, Shimadzu QP 2010; capil-
lary column: 30 m×0.25 mm×0.25 μm, helium as the
carrier gas and identified by the NIST 08 MS library).
The palladium contents of the samples were determined
quantitatively by atomic absorption spectroscopy (AAS)
on a HITACHI Z-5000 instrument.
Preparation of PdNPs@[Bmim]Lac
0
2
.3 mmol of Pd(OAc) , 60 mL of EtOH and 6.0
mmol of [Bmim]Lac were added to a 150 mL round-
bottom flask and stirred at r.t. condition. The color of
reaction mixture changed from bright yellow to black
indicating the achievement of PdNPs@[Bmim]Lac.
Figure 1 UV/Vis spectra of the mixture at different reduction
stages.
General procedure for the Suzuki-Miyaura reaction
TEM shows that the obtained PdNPs (Figure 2a) are
well dispersed with an average particle size of (1.50±
0.39) nm. Several crystalline planes were distinguish-
able and the interplanar distances were measured from
the Fast Fourier Transform (FFT) (Figure 2b) and the
corresponding crystalline planes were specified. The
interplanar distance with the value of 0.228 nm matches
Aryl halide (1.0 mmol), arylboronic acid (1.1 mmol),
Na
3
PO
4
•12H
2
O (3.0 mmol), prepared PdNPs@[Bmim]-
O (V∶V＝2∶1; 6.0
Lac (1.0 mol% Pd) and EtOH/H
2
mL) were added to a 15 mL round-bottom flask and
stirred at r.t. in air. The end of reaction was tracked by
TLC (thin layer chromatography). After completion of
the reaction, the mixture was extracted by hexane (15
mL×3) after the removal of the solvent by a rotary
evaporator. The combined extracts were dried with an-
[18]
well with (111) planes in face-centered cubic (fcc) Pd.
[19]
According to “lattice-matching model”,
lactate ani-
ons are effective for coordinating the Pd(111) face of a
2
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Chin. J. Chem. 2014, XX, 1—8

Room-Temperature Suzuki-Miyaura Reaction Catalyzed by Palladium Nanoparticles
metal nanocluster.
action temperature, and PdNPs@[Bmim]Lac (2.0 mol%
Pd) as the catalyst. Anhydrous solvents such as toluene
PhMe), N,N-dimethylformamide (DMF) and EtOH
(
give low yields of less than 30% (Entries 1－3). Or-
ganic/aqueous mixed solvent enhances the yield sig-
nificantly (Entry 4). Water plays an important role in the
reactions, having a solubilizing effect on the inorganic
bases and aiding the dispersibility of the IL with hy-
droxyl groups. Similar result has been observed in lit-
[
22]
erature. A mixed solvent of EtOH/H
2
O (V∶V＝2∶1)
achieves a good yield of 79% (Entry 4). So EtOH/H
2
O
was then used for the screening of different bases (En-
tries 5－9). The highest yield of 99% was obtained
when Na PO •12H O was used (Entry 9). Notably,
3 4 2
since EtOH was employed as the solvent in both the
preparation of the catalyst and the coupling reaction
steps, the prepared catalysis system can be directly de-
ployed in the coupling reaction without further work-up
2
when EtOH/H O was used. In the investigation of reac-
tion temperature (Entries 10－12), it is gratifying to find
that the coupling proceeds well at r.t., giving 99% yield
Figure 2 (a) TEM image of fresh PdNPs@[Bmim]Lac catalyst;
(
Entry 12). Finally, we assessed the influence of catalyst
(b) HRTEM image and Fast Fourier Transforms (FFT, top right
loading on this reaction (Entries 13－18). The coupling
reaction does not proceed in the absence of the Pd cata-
lyst (Entry 13). The low loading of PdNPs can catalyze
this reaction prominently (Entry 14), but it is time-
consuming to obtain the acceptable product yield (Entry
images); (c) TEM image of Pd(OAc)2 and [Bmim]Lac after
cross-coupling (Table 2, Entry 2); (d) TEM image of PdNPs@
[
Bmim]Lac catalyst after six cycles.
As shown in Figure 3, XRD pattern of the PdNPs
1
5). Hence, 1.0 mol% was the suitable loading of cata-
lyst while maintaining a 99% yield of the product (Entry
8).
In order to gain further insights into the catalytic
does not show any diffraction peak of Pd metal. The
Bragg reflection at 21.85° corresponds to diffraction
[20]
1
2
peak of SiO of glass slice. TEM analysis shows the
presence of PdNPs of about 1.5 nm. The particle size of
PdNPs might be too small to form long range ordering
so that XRD diffraction, which works on periodicity,
mechanism of as prepared PdNPs catalyst, a series of
control experiments were carried out under optimized
conditions (Table 2), namely catalyst (1.0 mol% of Pd),
[18,21]
could not be detected.
EtOH/H
2 3 4
O (V∶V＝2∶1) as solvent and Na PO •
1
2H O as a base at r.t. At first, Pd(OAc) without ILs
2
2
offers a moderate yield with the formation of less-active
palladium black (Entry 1). Direct addition of Pd(OAc)
2
and [Bmim]Lac to the reaction system leads to a low
yield of 63% (Entry 2). Under this condition, the Pd(II)
species is reduced by ethanol to Pd metal with uncon-
trolled size (Figure 2c). These findings clearly indicate
that very small size of the prepared PdNPs plays an im-
portant role for the catalytic activity. Then, the effect of
a series of ILs with different anions was evaluated. The
use of acetate, propionate, and tetrafluoroborate anions
instead of lactate anion results in apparently lower
yields (Entries 3－5)
obtained by the use of PdNPs@[Bmim]HOCH
Entry 6) due to the similar structure of glycolate anion
.
Interestingly, yield of 99% can be
2
COO
Figure 3 XRD patterns of PdNPs@[Bmim]Lac on glass slice.
(
as that of lactate anion (Entry 7). Low yield of 68% is
obtained with the formation of Pd black while NaLac
was used for the replacement of [Bmim]Lac (Entry 8). It
has reported that a three-dimensional network formed
by anions and the imidazolium ring cations of ILs
brings metal NPs with the needed electrostatic and steric
Catalytic studies
The coupling of 4-bromoanisole with phenylboronic
acid was employed as a model reaction for screening of
the parameters of the Suzuki-Miyaura reaction catalyzed
by PdNPs@[Bmim]Lac (Table 1). Initially, various
solvents were screened, keeping the other parameters
[
9a]
stabilization.
Hence, it is thought that [Bmim]Lac
2 3
fixed, those were Na CO as the base, 70 ℃ as the re-
comprised with the hydroxyl group is able to strengthen
Chin. J. Chem. 2014, XX, 1—8
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www.cjc.wiley-vch.de
3

Wang et al.
FULL PAPER
a
Table 1 Optimization of the reaction conditions
b
Entry
Base
Solvent (V∶V)
PhMe
T/℃
70
70
70
70
70
70
70
70
70
60
40
25
25
25
25
25
25
25
[Pd]/mol%
2.0
Yield /%
1
2
3
4
5
6
7
8
9
Na
Na
2
2
CO
3
3
3
3
16
18
25
79
68
76
79
89
99
99
99
99
0
CO
DMF
2.0
Na CO
EtOH
2.0
2
Na CO
EtOH/H O (2∶1)
2.0
2
2
K
2
CO
3
EtOH/H
2
O (2∶1)
2.0
KOAc
EtOH/H O (2∶1)
2.0
2
K PO •3H O
EtOH/H O (2∶1)
2.0
3
4
2
2
NaOH
EtOH/H O (2∶1)
2.0
2
Na PO •12H O
EtOH/H O (2∶1)
2.0
3
4
2
2
10
Na PO •12H O
EtOH/H O (2∶1)
2.0
3
4
2
2
1
1
2
3
4
Na
3
PO
4
•12H
2
O
EtOH/H
2
O (2∶1)
2.0
1
1
1
Na PO •12H O
EtOH/H O (2∶1)
2.0
3
4
2
2
2
2
2
2
Na PO •12H O
EtOH/H O (2∶1)
0
3
4
2
Na PO •12H O
EtOH/H O (2:1)
0.25
0.25
0.5
40
79
90
93
3
4
2
c
1
5
Na PO •12H O
EtOH/H O (2∶:1)
3
4
2
16
17
18
Na PO •12H O
EtOH/H O (2∶1)
3
4
2
Na
3
PO
4
•12H
2
O
EtOH/H
2
O (2∶1)
0.75
1.0
Na PO •12H O
EtOH/H O (2∶1)
99
3
4
2
2
a
b
Conditions: 4-bromoanisole (1.0 mmol), phenylboronic acid (1.1 mmol), base (3.0 mmol), solvent (6.0 mL) in air for 4 h. Determined
c
by GC analysis (hexamethylbenzene as an internal standard). The reaction time is 8 h.
a
Table 2 Results of control experiments
ILs or salts
b
Entry
Pd catalyst
Yield /%
Cation
－
Anion
－
Lac
1
2
3
4
5
6
7
8
Pd(OAc)
2
80
+
+
+
+
+
+
Pd(OAc) and [Bmim]Lac
2
[Bmim]
[Bmim]
[Bmim]
[Bmim]
[Bmim]
[Bmim]
63

PdNPs@[Bmim]CH COO
CH COO
81
3
3

PdNPs@[Bmim]C H COO
2
C H COO
79
2
5
5
-
PdNPs@[Bmim]BF4
PdNPs@[Bmim]HOCH COO
PdNPs@[Bmim]Lac
Pd(OAc) @NaLac
BF4
58
COO
99
2
HOCH
2
Lac
Lac
99
68
+
2
Na
a
Conditions: 4-bromoanisole (1.0 mmol), phenylboronic acid (1.1 mmol), Na
3
PO
4
•12H
2
O (3.0 mmol), EtOH/H
2
O (V∶V＝2∶1, 6.0 mL),
b
and catalyst (1.0 mol% of Pd) in air for 4 h. Determined by GC analysis (hexamethylbenzene as an internal standard).
this network. Moreover, the nature of the Pd surface
was analyzed by XPS (Figure 4) as both the catalyst
preparation and the coupling reaction were carried out
in air. Peaks at 334.2 and 339.4 eV can be attributed to
occurred during the reaction. However, no obvious det-
rimental effect on the activity of the PdNPs was ob-
served as an oxide layer has a significant stabilizing
[
9b]
effect on metal NPs and fresh PdNP surfaces can be
continuously generated through reduction by the ethanol
[23]
Pd 3d5/2 and Pd 3d3/2 of Pd(0).
Peaks at 335.5 and
[25]
3
40.8 eV corresponded to binding energies of Pd 3d5/2
solvent.
[24]
and Pd 3d3/2 of Pd(II) in PdO, respectively.
It is
To test the generality of this PdNPs@[Bmim]Lac
catalyst, couplings of various aryl halides and aryl
found that partial oxidation of the PdNP surfaces to PdO
4
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Chin. J. Chem. 2014, XX, 1—8

Room-Temperature Suzuki-Miyaura Reaction Catalyzed by Palladium Nanoparticles
boronic acids were investigated under the optimized
conditions (Table 3). It is noteworthy that the PdNPs@
Bmim]Lac catalyst shows high efficiency and good
functional group tolerance. Aryl bromides and iodides
bearing electron-donating (CH , OCH ), electron-neu-
tral (H), and electron-withdrawing (NO , CHO, CN)
[
3
3
2
groups are all efficiently coupled with phenylboronic
acid to afford the desired biaryls in good to excellent
yields at r.t. (Entries 1－10). However, 2-bromoanisole
is coupled in a lower yield due to the effect of steric
hindrance (Entry 8 vs. Energy 9). In addition, the cou-
pling reaction can be efficiently accomplished with aryl
3
boronic acids bearing electron-donating (CH ) or elec-
Figure 4 XPS spectra of PdNPs@[Bmim]Lac.
tron-withdrawing groups (Cl) (Entries 11－23).
a
Table 3 Reaction scope
1
2
b
Entry
1
X
I
R
R
Time/h
4
Product
Yield /%
4-OCH
3
H
H
H
H
H
H
H
H
H
99
93
99
98
93
94
92
99
87
O N
2
2
3
4
5
6
7
8
9
I
4-NO
2
4
4
4
4
4
4
4
6
b
I
4-CH3
Br
Br
Br
Br
Br
Br
4-CHO
4-CN
H
NC
e
4-CH
3
4-OCH3
2-OCH3
OCH3
g
Chin. J. Chem. 2014, XX, 1—8
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
5

Wang et al.
FULL PAPER
Continued
1
2
b
Entry
X
R
R
Time/h
4
Product
Yield /%
O N
2
1
0
1
Br
4-NO
2
H
98
99
92
90
97
99
90
86
93
90
91
b
1
I
4-CH
3
4-CH
3
4
4
4
4
4
4
4
5
4
4
12
13
14
15
16
17
18
19
20
I
4-OCH3
4-CH3
4-CH3
4-CH3
Br
Br
Br
Br
Br
Br
I
H
4-NO2
4-CHO
4-CN
4-CH
3
4-CH3
4-CH
3
4-CH
4-CH
4-Cl
3
4-OCH
3
3
i
O N
2
Cl
4-NO
2
m
Br
4-CH3
4-Cl
21
22
23
Br
Br
Br
4-OCH3
4-CN
4-Cl
4-Cl
4-Cl
4
4
4
94
84
NC
Cl
p
4-CHO
91
a
Conditions: aryl halide (1.0 mmol), arylboronic acid (1.1 mmol), Na
3
PO
PdNPs@[Bmim]Lac (1.0 mol% of Pd) in air. Isolated yield based on aryl halide.
4
•12H
2
O (3.0 mmol), EtOH/H
2
O (V∶V＝2∶1, 6.0 mL), and
b
6
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Chin. J. Chem. 2014, XX, 1—8

Room-Temperature Suzuki-Miyaura Reaction Catalyzed by Palladium Nanoparticles
To the best of our knowledge, this PdNPs@
Bmim]Lac system exhibits outstanding catalytic activ-
catalytic activity in promoting Suzuki-Miyaura reac-
[
tions at r.t. in air with an environmentally friendly sol-
vent system. The concept of designing new metal NP
catalysts employing ILs based on natural anions with
coordinating and protecting groups is attractive, which
would offer good prospects for the development of
highly efficient, stable, and recyclable catalysts for cou-
pling reactions. Further studies aimed at a series of or-
ganic transformations using other renewable ILs to sta-
bilize metal NPs as well as delineation of the relevant
mechanism, are currently underway in our laboratories.
ity among the reported catalysts used for the Suzuki-
Miyaura coupling reaction in ILs in terms of catalyst
loading (1.0 mol% Pd) at r.t. condition. PdNPs or
Pd-ligand complexes in ILs have been widely reported
to efficiently catalyze the Suzuki-Miyaura coupling of
aryl bromides and iodides with phenylboronic acid.
However, these coupling reactions require high tem-
peratures up to 100 ℃, high catalyst loadings, or envi-
[
26]
ronmentally unfriendly solvents.
The activity of the
present catalyst is also comparable to that of a recently
[27]
reported PdNPs-phosphine ligand catalyst.
It is
Acknowledgements
thought that the carboxyl and hydroxyl groups of the
lactate anion can provide sufficient stabilization and aid
the dispersion of the PdNPs, as hydroxyl-functionalized
ILs have been demonstrated to facilitate the formation
of near-monodisperse NPs and to enhance their stabil-
This work was supported by the National Natural
Science Foundation of China (Nos. 21336002 and
2
1276094) and the Doctoral Fund of Ministry of Educa-
tion of China (No. 20130172110043).
[
18,28]
ity.
References
The reusability of our prepared catalyst was next in-
vestigated in the coupling of 4-bromoanisole with phe-
nylboronic acid under the optimized condition. As
shown in Figure 5, the catalyst is still of high catalytic
activity without obvious decrease. A TEM image of the
catalyst after the sixth run (Figure 2d) indicates that the
mean diameter of the NPs (1.54±0.38 nm) is very close
to that of the fresh sample (Figure 2a, 1.50±0.39 nm).
AAS shows that about 0.2% of the total palladium ap-
pears in the hexane extract. It is interesting to see that
the recovered catalyst after eight runs could still give
the similar yield of product as fresh catalyst at the long-
[1] Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
[2] (a) Ghosh Chaudhuri, R.; Paria, S. Chem. Rev. 2012, 112, 2373; (b)
Ott, L. S.; Finke, R. G. Coord. Chem. Rev. 2007, 251, 1075.
[
[
3] (a) Zaera, F. Chem. Soc. Rev. 2013, 42, 2746; (b) Rao, C. N. R.;
Kulkarni, G. U.; Thomas, P. J.; Edwards, P. P. Chem. Soc. Rev. 2000,
2
9, 27.
4] (a) Cushing, B. L.; Kolesnichenko, V. L.; O'connor, C. J. Chem. Rev.
004, 104, 3893; (b) White, R. J.; Luque, R.; Budarin, V. L.; Clark,
2
J. H.; Macquarrie, D. J. Chem. Soc. Rev. 2009, 38, 481; (c) Chun, Y.
S.; Shin, J. Y.; Song, C. E.; Lee, S. G. Chem. Commun. 2008, 942;
(d) Tao, L. M.; Xie, Y. X.; Deng, C. L.; Li, J. H. Chin. J. Chem.
2
009, 27, 1365.
th
[5] (a) Fihri, A.; Bouhrara, M.; Nekoueishahraki, B.; Basset, J. M.; Pol-
shettiwar, V. Chem. Soc. Rev. 2011, 40, 5181; (b) Yan, N.; Xiao, C.;
Kou, Y. Coord. Chem. Rev. 2010, 254, 1179; (c) Parvulescu, V. I.;
Hardacre, C. Chem. Rev. 2007, 107, 2615.
er reaction time (9 run).
[
6] (a) Mu, X. D.; Meng, J. Q.; Li, Z. C.; Kou, Y. J. Am. Chem. Soc.
005, 127, 9694; (b) Antonietti, M.; Kuang, D.; Smarsly, B.; Zhou,
2
Y. Angew. Chem., Int. Ed. 2004, 43, 4988; (c) Plechkova, N. V.;
Seddon, K. R. Chem. Soc. Rev. 2008, 37, 123; (d) Yan, N.; Yuan, Y.;
Dykeman, R.; Kou, Y.; Dyson, P. J. Angew. Chem., Int. Ed. 2010,
4
9, 5549.
[
[
7] (a) Dupont, J. J. Braz. Chem. Soc. 2004, 15, 341; (b) Dupont, J.;
Scholten, J. D. Chem. Soc. Rev. 2010, 39, 1780.
8] (a) Zhao, D.; Fei, Z.; Geldbach, T. J.; Scopelliti, R.; Dyson, P. J. J.
Am. Chem. Soc. 2004, 126, 15876; (b) Amatore, C.; Jutand, A. Acc.
Chem. Res. 2000, 33, 314; (c) Amatore, C.; Jutand, A. J. Organomet.
Chem. 1999, 576, 254; (d) Xu, L. J.; Chen, W. P.; Xiao, J. L. Or-
ganometallics 2000, 19, 1123; (e) Roszak, R.; Trzeciak, A. M.; Per-
nak, J.; Borucka, N. Appl. Catal. A: Gen. 2011, 409－410, 148; (f)
Umpierre, A. P.; Machado, G.; Fecher, G. H.; Morais, J.; Dupont, J.
Adv. Synth. Catal. 2005, 347, 1404; (g) Yang, X.; Yan, N.; Fei, Z.;
Crespo-Quesada, R. M.; Laurenczy, G.; Kiwi-Minsker, L.; Kou, Y.;
Dyson, Y. L. A. P. J. Inorg. Chem. 2008, 47, 7444.
Figure 5 Recycling tests for the model reaction. Reaction con-
ditions: 4-bromoanisole (1.0 mmol), phenylboronic acid (1.1
mmol), Na
3 4 2 2
PO •12H O (3.0 mmol), EtOH/H O (V∶V＝2∶1;
6
.0 mL) and catalyst (1.0 mol% of Pd) in air for 4 h; Isolated
[
9] (a) Vollmer, C.; Janiak, C. Coord. Chem. Rev. 2011, 255, 2039; (b)
Ott, L. S.; Finke, R. G. Inorg. Chem. 2006, 45, 8382.
yield. *: The reaction time is 6 h.
[
[
10] (a) Petkovic, M.; Seddon, K. R.; Rebelo, L. P.; Silva Pereira, C.
Chem. Soc. Rev. 2011, 40, 1383; (b) Li, X. H.; Zhao, J. G.; Li, Q. H.;
Wang, L. F.; Tsang, S. C. Dalton Trans. 2007, 1875.
Conclusions
In conclusion, a PdNPs catalyst (PdNPs@[Bmim]-
Lac) stabilized by an IL with a natural, reusable, and
non-toxic lactate anion has been prepared by a very
simple method under mild conditions. It exhibits high
11] (a) Scholten, J. D.; Leal, B. C.; Dupont, J. ACS Catal. 2012, 2, 184;
(
b) Balanta, A.; Godard, C.; Claver, C. Chem. Soc. Rev. 2011, 40,
4973; (c) Amini, M.; Bagherzadeh, M.; Rostamnia, S. Chin. Chem.
Lett. 2013, 24, 433.
Chin. J. Chem. 2014, XX, 1—8
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
7

Wang et al.
FULL PAPER
[
12] (a) Kostas, I. D.; Tenchiu, A.-C.; Arbez-Gindre, C.; Psycharis, V.;
Raptopoulou, C. P. Catal. Commun. 2014, 51, 15; (b) Nan, G. M.;
Zhu, F. H.; Wei, Z. J. Chin. J. Chem. 2011, 29, 72.
13] Pernak, J.; Goc, I.; Mirska, I. Green Chem. 2004, 6, 323.
14] Zhu, W. W.; Yang, H. M.; Yu, Y. Y.; Hua, L.; Li, H.; Feng, B.; Hou,
Z. S. Phys. Chem. Chem. Phys. 2011, 13, 13492.
Zare, A.; Iranpoor, N.; Beyzavi, M. H.; Luque, R. Green Chem.
2013, 15, 2132.
[24] Handbook of X-ray Photoelectron Spectroscopy, Eds.: Muilenberg,
G. E.; Wagner, C. D.; Riggs, W. M.; Davis, L. E.; Moulder, J. F.,
Perkin-Elmer Corporation (Physical Electronics), America, 1979, pp.
118, 119.
[
[
[
[
15] Coronado, E.; Ribera, A.; Garcia-Martinez, J.; Linares, N.;
Liz-Marzan, L. M. J. Mater. Chem. 2008, 18, 5682.
16] (a) Nadagouda, M. N.; Varma, R. S. Green Chem. 2008, 10, 859;
[25] (a) Soomro, S. S.; Ansari, F. L.; Chatziapostolou, K.; Kohler, K. J.
Catal. 2010, 273, 138; (b) Kohler, K.; Heidenreich, R. G.; Soomro,
S. S.; Prockl, S. S. Adv. Synth. Catal. 2008, 350, 2930.
(
1
b) Creighton, J. A.; Eadon, D. G. J. Chem. Soc., Faraday Trans.
991, 87, 3881.
[26] (a) Planellas, M.; Pleixats, R.; Shafir, A. Adv. Synth. Catal. 2012,
354, 651; (b) Yang, X.; Fei, Z.; Zhao, D.; Ang, W. H.; Li, Y.; Dyson,
P. J. Inorg. Chem. 2008, 47, 3292; (c) Song, H. B.; Yan, N.; Fei, Z.;
Kilpin, K. J.; Scopelliti, R.; Li, X. H.; Dyson, P. J. Catal. Today
2012, 183, 172; (d) Wang, R. H.; Twamley, B.; Shreeve, J. M. J.
Org. Chem. 2006, 71, 426; (e) Yang, X.; Fei, Z.; Geldbach, T. J.;
Phillips, A. D.; Hartinger, C. G.; Li, Y. D.; Dyson, P. J. Organome-
tallics 2008, 27, 3971; (f) Durand, J.; Teuma, E.; Malbosc, F.; Kihn,
Y.; Gomez, M. Catal. Commun. 2008, 9, 273.
[27] Iranpoor, N.; Firouzabadi, H.; Motevalli, S.; Talebi, M. J. Organ-
omet. Chem. 2012, 708－709, 118.
[28] Yuan, X.; Yan, N.; Xiao, C. X.; Li, C. N.; Fei, Z. F.; Cai, Z. P.; Kou,
Y.; Dyson, P. J. Green Chem. 2010, 12, 228.
[
[
17] Khazaei, A.; Rahmati, S.; Saednia, S. Catal. Commun. 2013, 37, 9.
18] Yuan, X.; Yan, N.; Katsyuba, S. A.; Zvereva, E. E.; Kou, Y.; Dyson,
P. J. Phys. Chem. Chem. Phys. 2012, 14, 6026.
19] Finke, R. G.; Zkar, S. Coord. Chem. Rev. 2004, 248, 135.
20] Kim, M.; Heo, E.; Kim, A.; Park, J. C.; Song, H.; Park, K. H. Catal.
Lett. 2012, 142, 588.
21] Feng, B.; Chen, C.; Yang, H. M.; Zhao, X. G.; Hua, L.; Yu, Y. Y.;
Cao, T.; Shi, Y.; Hou, Z. S. Adv. Synth. Catal. 2012, 354, 1559.
22] (a) Yu, T.; Wu, X.; Yang, J. Chin. J. Chem. 2012, 30, 2798; (b) Xie,
Y. X.; Wang, J.; Li, J. H.; Liang, Y. Chin. J. Chem. 2008, 26, 2261.
23] Zolfigol, M. A.; Khakyzadeh, V.; Moosavi-Zare, A. R.; Rostami, A.;
[
[
[
[
[
(Zhao, C.)
8
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Chin. J. Chem. 2014, XX, 1—8