One-pot synthesis of monodisperse palladium tin nanoparticles with controlled composition and size and its catalytic ability study

Article abstract of DOI:10.1007/s10562-015-1593-5

We have developed a novel one-pot synthetic procedure for monodisperse palladium tin bimetallic alloy nanoparticles (NPs) with tunable compositions and sizes by the co-reduction of tin(II) acetate and palladium(II) bromide in the presence of oleylamine and trioctylphosphine. These NPs loaded on active carbon (PdSn/C) were used as active catalysts for Heck reactions, and exhibited composition dependent catalytic activities. Among these nanocatalysts, Pd₆₃Sn₃₇ NPs showed the best catalytic performance which is even superior to pure Pd NPs. Graphical Abstract PdSn NPs with controlled compositions and sizes were synthesized and characterized systematically, and Pd₆₃Sn₃₇/C NPs showed the best catalytic ability and stability that is even superior to pure Pd NPs with higher catalytic activity and stability in multi-recycled Heck reactions.

Full text of DOI:10.1007/s10562-015-1593-5

Catal Lett (2015) 145:1837–1844
DOI 10.1007/s10562-015-1593-5
One-Pot Synthesis of Monodisperse Palladium Tin Nanoparticles
with Controlled Composition and Size and Its Catalytic Ability
Study
Yong Li1 Yu Dai1 Xi-ke Tian1
•
•
Received: 3 May 2015 / Accepted: 15 July 2015 / Published online: 4 August 2015
Ó Springer Science+Business Media New York 2015
Abstract We have developed a novel one-pot synthetic
procedure for monodisperse palladium tin bimetallic alloy
nanoparticles (NPs) with tunable compositions and sizes by
the co-reduction of tin(II) acetate and palladium(II) bro-
mide in the presence of oleylamine and trioctylphosphine.
These NPs loaded on active carbon (PdSn/C) were used as
active catalysts for Heck reactions, and exhibited compo-
sition dependent catalytic activities. Among these
nanocatalysts, Pd63Sn37 NPs showed the best catalytic
performance which is even superior to pure Pd NPs.
Graphical Abstract PdSn NPs with controlled composi-
tions and sizes were synthesized and characterized sys-
tematically, and Pd63Sn37/C NPs showed the best catalytic
ability and stability that is even superior to pure Pd NPs
with higher catalytic activity and stability in multi-recycled
Heck reactions.
Keywords Palladium tin nanoparticles Á Controlled
composition and size Á Transmission electron microscope Á
Heck reaction
Electronic supplementary material The online version of this
article (doi:10.1007/s10562-015-1593-5) contains supplementary
material, which is available to authorized users.
1 Introduction
& Xi-ke Tian
xktian@cug.edu.cn
The olefination of aryl halides (Heck reaction) is one of the
most important reactions used to generate new carbon–
carbon bond [1]. This reaction is often catalyzed by
1
Faculty of Material Science and Chemistry, China University
of Geosciences, Wuhan 430074, People’s Republic of China
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Y. Li et al.
palladium (Pd) complex of phosphines, amines or hetero-
cyclic carbenes in homogeneous solutions under inert
atmosphere with good synthetic yields [2]. However, these
Pd-complex catalysts do have their limitations. They are
only active when the Pd(II) is reduced to Pd(0), which
requires the reaction to proceed under a non-oxidizing
environment; the active Pd(0) intermediate species are
unstable in the reaction conditions and tend to aggregate
into inactive components, making it impossible to recycle
them for further use; the Pd(II) and Pd(0) as well as the
specially chosen ligands contaminate the reaction product
and must be removed from the product via tedious sepa-
ration process before the newly prepared organic com-
pounds can be used for further applications [3]. To
overcome these problems associated with the previous
catalysts, novel catalyst systems are also developed and
tested.
ability of PdSn NPs is mainly due to the unique charac-
teristics of tin. And the unique characteristics of tin are
probably attributed to the strong metal-support interaction
and/or the alloy formation between tin and precious metal,
such as Pd and Pt [20]. In other words, some electronic
effects are of interesting importance for the enhanced
performance of tin. For instance, in electronic effects, tin
could modify the electronic density of Pt due to positive
charge transfer from Snn ? species to noble metals, such
as Pd and Pt, and the formation of different alloys of Pd-Sn
and Pt–Sn. These modifications may be responsible for
some changes in the heat of adsorption of different
adsorbates, facilitating the reaction [21, 22]. Previous
studies also indicated that the compositions or morpholo-
gies of PdSn alloy NPs can be controlled by tuning the
amount of the precursors. In the literature, PdSn NPs were
synthesized by traditional co-reduction of Pd and Sn salts
directly on various supporting materials such as amorphous
carbon [23]. However, all the reported syntheses did not
provide sufficient control over the morphology and com-
position of the NPs simultaneously to meet the high stan-
dard of a catalyst [24].
These novel catalysts are either Pd complexes or Pd-
based elemental, alloy and core/shell nanoparticles (NPs)
supported on various forms of carbons, oxides, polymer
resins, or even magnetic NPs [4–9]. Mahmoud Nasrol-
lahzadeh has prepared Pd/CuO NPs for Heck coupling
reactions with the high yields, simple methodology, easy
preparation and handling of the catalyst and also easy work
up [10]. Pd NPs also can be supported on pectin and
gelatin, respectively to exhibit a high activity toward Heck
reaction, and the catalysts can be recycled for several runs
without any losses of catalytic ability [11, 12]. Pd NPs on
amino-vinyl silica functionalized Fe3O4 magnetic NPs
were also applied as nanocatalysts for Heck reaction and
the catalysts were recoverable magnetically and could be
reused for five runs without significant loss of catalytic
activity [13]. Among a great number of Pd based NPs for
Heck reaction, bimetallic Pd alloy NPs are particularly
important in the area of catalysis because they often
exhibited high catalytic ability than their monometallic
counterparts [14]. For Pd alloy NPs, mixing a second non-
precious element with Pd metal is an effective way to
reduce the precious metal usage and may enhance its
internal properties due to synergistic effects and the rich
diversity of the compositions [15, 16]. Seong-Ho Choi
synthesized a series of Pd alloy NPs, such as PdAg, PdNi,
and PdCu NPs for Heck reactions, and found the NPs
showed excellent capabilities as catalysts for Heck reac-
tions with the comparable catalytic ability of Pd NPs [17].
Palladium tin (PdSn) alloy nanostructures have attracted
intense attention in both synthesis and catalysis fields.
Earlier studies have shown that PdSn is an active catalyst
for hydrogenation of chloro(Cl)-benzene as Sn on PdSn has
higher affinity for the chloride, stabilizing Pd against oxi-
dation by Cl [18]. PdSn alloys are also active for
hydrogenolysis reactions and their activity are Pd/Sn
composition dependent [19]. The reason for high catalytic
Recently a facile synthetic approach of monodisperse Pd
NPs, Pd alloy and PtSn NPs was developed systematically
[25, 26]. We found that the synthesis could be extended to
PdSn as well and monodisperse PdSn alloy NPs with
compositions and sizes controlled. Herein, we report the
one-pot preparation of monodisperse PdSn alloy NPs and
study their catalytic abilities for Heck reaction between
aryl halides and styrene. We studied the catalytic properties
of Pd77Sn23, Pd67Sn33, Pd63Sn37, Pd52Sn48 and Pd49Sn51 for
model Heck reaction and found their catalytic abilities are
highly composition dependent. They were indeed more
active and stable catalyst than pure Pd NPs with Pd63Sn37
NPs being the most active one due to its high catalytic
ability, low active species leaching and high stability dur-
ing the recycle Heck reactions. In addition, Pd63Sn37 NPs
can be extended to be applied in a number of similar Heck
reactions, indicating that this kind of nanocatalysts provide
a new synthetic approach for carbon coupling reactions.
2 Experimental Section
2.1 Materials and Characterization Techniques
Palladium(II) bromide (PdBr2, 99 %), Tin(II) acetate
(Sn(ac)2, 99 %), oleylamine (OAm, technical grade, 70 %),
trioctylphosphine (TOP, technical grade, 90 %), acetic
acid, tributylamine borane complex (TBAB), Et3N, Na2-
CO3, NaHCO3, Na3PO4, chlorobenzene, bromobenzene,
iodobenzene, N-methylpyrrolidone (NMP), N,N-dimethy-
lacetamide (DMAc), N-dimethylformide (DMF), and
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One-Pot Synthesis of Monodisperse Palladium Tin Nanoparticles with Controlled Composition…
1839
triethylamine (Et3N) were purchased from Sigma-Aldrich
and Strem Chemicals and used without further purification.
Carbon black (Ketjen EC 300 J) is purchased from the
Ketjen Black International Company, Japan. Water used in
the experiments was deionized (DI) and doubly distilled
prior to use.
then dispersed in acetic acid. PdSn/C and acidic acid
mixture was heated at 70 °C for 10 h to clean the surfaces
of NPs. After cooled to room temperature, PdSn/C were
separated by adding 30 mL of ethanol and centrifugation,
followed by extra two ethanol washes to clean all acid
residues. PdSn/C catalysts were dried, weighed and finally
dispersed in a measured amount of de-ionized water by 1 h
sonication, resulting in 2 mg PdSn/C nanocatalysts per
1 mL water dispersion.
Transmission electron microscopy (TEM) images were
acquired on a Philips CM 20 (200 kV) transmission elec-
tron microscope. High resolution transmission electron
microscopy (HRTEM) images are obtained with JEOL
2010 (200 kV) and JEOL 4000 EX transmission electron
microscopes. X-ray powder diffraction (XRD) patterns of
the samples were recorded on a Bruker AXS D8-Advanced
2.4 General Procedure for the Catalytic Tests
The model Heck reaction of bromobenzene and styrene
was performed. Typically, the as-prepared 2 mg nanocat-
alyst was added into the mixture solution of 10 mmol
bromobenzene, 20 mmol base and 5 mL organic solvent.
The mixture solution was preheated for 1 h, and then
12 mmol styrene was added, and the solution was refluxed
and stirred for 6 h. After that, the catalysts were filtered via
hot filtration, and the filtrated solution was collected and
evaporated to get a white solid. The product was purified
by column chromatography. Pd content in the product
solution was analyzed using an ICP–AES. The experiments
were repeated with the catalyst recycled from last reaction.
˚
diffractometer with Cu Ka radiation (k = 1.5418 A). The
compositions of the samples were measured by Inductively
Coupled Plasma–Atomic Emission Spectroscopy (ICP–
AES). The Heck reaction products were determined by gas
chromatography method.
2.2 Synthesis of PdSn NPs
In a typical synthesis for Pd77Sn23 NPs, 0.2 mmol PdBr2
and 0.05 mmol Sn(ac)2 were mixed with 12 ml OAm in the
reaction flask with magnetic stirring and degassed at room
temperature for 10 min under N2 flow. 0.5 ml TOP was
added into the degassed reaction mixture and the mixture
was degassed at room temperature for another 30 min
before being quickly heated up to 260 °C with in 10 min;
the reaction was maintained at this temperature for 1 h to
complete the synthesis. After it was cooled to room tem-
perature, the Pd77Sn23 NPs were precipitated out through
ethanol addition and collected through centrifugation. The
Pd77Sn23 NPs were redispersed in hexane and washed
twice with hexane and ethanol mixture. Finally the as
prepared Pd77Sn23 NPs was dispersed and stored in hexane.
Composition control of the PdSn NPs: the composition
control was achieved simply by changing the molar ration
of PdBr2/Sn(ac)2 used in the synthesis. For PdBr2/Sn(ac)2
(mmol/mmol) of 0.2/0.07, 0.2/0.1, 0.2/0.15, 0.2/0.2, PdSn
NPs with Pd/Sn atomic ratios of 67/33, 63/37, 52/48, 49/51
were synthesized respectively. Size control of the PdSn
NPs: the size control was achieved by controlling the
amount of TOP in the synthesis. In the synthesis, 6.5, 8 and
9.5 nm PdSn alloy NPs were synthesized by using 0.5,
0.75, 1.0 mL TOP.
3 Results and Discussion
The monodisperse Pd77Sn23 NPs was synthesized by
quickly heating up a solution of 0.2 mmol PdBr2,
0.05 mmol Sn(ac)2, 0.5 mL TOP and 12 mL OAm to
260 °C and maintained at this temperature for 1 h. The
presence of TOP was important to initiate co-reduction of
PdBr2 and Sn(ac)2 for PdSn nucleation and growth.
Without TOP, a mixture of Pd and Sn NPs was formed.
The composition of the PdSn NPs measured by ICP–AES
was controlled by the molar ratio of the metal precursors.
When PdBr2/Sn(ac)2 (mmol/mmol) = 0.2/0.05, 0.2/0.07,
0.2/0.1, 0.2/0.15, 0.2/0.2, PdSn NPs with different molar
ratios of Pd77Sn23, Pd67Sn33, Pd63Sn37, Pd52Sn48 and
Pd49Sn51 were obtained respectively, and the atomic ratio
of Pd in the precursors was carried over to the final product.
Further increase of the Sn(ac)2 to 0.25 mmol cannot lead to
further increase of Sn in the NPs, and the excess Sn(ac)2
leads to a polydisperse and ununiform product (Fig. S1f).
So this synthesis has a limited control over the composition
with the Pd1Sn1 to be the Sn rich end. It looks that under
current synthetic conditions, Sn-rich PdSn alloy NPs could
not be synthesized.
2.3 Preparation of Catalysts: PdSn/C
Ten milligram of PdSn NPs were dispersed in 10 mL
hexane in a 20 mL vial and 10 mg of Ketjen carbon sup-
port was carefully added to it. This mixture was sonicated
for 2 h to load all PdSn NPs on carbon (denoted PdSn/C).
PdSn/C was separated from hexane by centrifugation and
Figure 1 is the representative TEM image of the Pd77-
Sn23 NPs with an average diameter of 6.5 0.5 nm. TEM
images of other PdSn NPs are given in Fig. S1(a–e). The
sizes of all PdSn NPs prepared here are around 6.5 nm, and
123

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Y. Li et al.
Fig. 1 a TEM image and
SAED (inset), b HRTEM image
of the as prepared Pd77Sn23
NPs, XRD patterns of the as
prepared Pd77Sn23, Pd63Sn37
and Pd52Sn48 NPs (c) and the
crystallized NPs after thermal
treatment (d)
the detailed sizes of the NPs were listed in Table S1. In
addition, while keeping the composition constant, we could
tune the sizes of the NPs by varying the amount of TOP
added in the reaction. For example, 6.5, 8, and 9.5 nm
Pd77Sn23 NPs (Fig. S2) were synthesized by using 0.5,
0.75, 1.0 mL TOP. It seems that more TOP can protect Pd
via Pd-TOP from the formation of PdSn nuclei in the
reaction mixture, allowing more Pd (and Sn) to grow
around the existing nuclei into larger NPs. The as-synthe-
sized PdSn NPs are in polycrystalline structure as indicated
by diffused diffraction rings observed in the selected area
electron diffraction pattern (SAED, Fig. 1a inset). High
resolution TEM (HRTEM) image of the single Pd77Sn23
NPs (Fig. 1b) show the smaller crystal domains on each NP
with crystal lattice fringes at 0.226 nm, corresponding to
(111) crystal planes. X-ray diffraction (XRD) was further
used to characterize the structure of the as prepared PdSn
NPs. Fig. 1c is the XRD patterns of the Pd77Sn23, Pd63Sn37
and Pd52Sn48 NPs. The broad XRD diffraction peaks agree
with the polycrystalline nature. However, the XRD peaks
of the as prepared PdSn NPs cannot be simply ascribed to
any Pd3Sn1, Pd2Sn1, Pd1Sn1 or Pd phases. To identify the
crystal phases, we heated the as prepared NPs at elevated
temperatures in Argon. The Pd77Sn23 NPs after high tem-
perature crystallization showed a cubic Pd3Sn1 phase. And
the Pd63Sn37 NPs and Pd52Sn48 NPs after annealing
showed orthorhombic Pd2Sn1 and Pd1Sn1 crystal phases,
respectively (Fig. 1d). The XRD characterizations
demonstrate that by controlling Pd/Sn composition, we can
obtain PdSn NPs with different crystal phases. Our syn-
thesis is advantageous compared to what have been
reported. For example, the PdSn NPs made from b-Sn
nanocube templates only show Pd1Sn1 crystal phase [27].
The PdSn NPs formed directly on carbon support have an
fcc structure same as Pd, and the doping of Sn atoms leads
to a lattice change [28]. It looks that in these two studies,
only a small amount of Sn was successfully alloyed with
Pd, as seen from the phase diagram of Pd-Sn system [29],
the fcc solid solution with a Pd structure only exists at Pd
rich end (at.% of Pd[84.5 %). Our synthesis is carried out
at a temperature as high as 260 °C that benefits alloy for-
mation, thus our synthesis leads to the formation PdSn NPs
with controlled alloy structure.
To apply the PdSn NPs as nanocatalysts for Heck
reactions, the as prepared PdSn NPs (20 mg) were loaded
onto carbon black (20 mg) (denoted as PdSn/C) by soni-
cation followed by acetic acid cleaning. The PdSn NPs are
well dispersed on the carbon support as shown in the TEM
image (Fig. 2). For Heck reaction of bromobenzene and
styrene, reaction parameters, such as temperature, organic
solvent, and base are quite important. As shown in
Table S2, the optimum reaction parameters for Heck
123

One-Pot Synthesis of Monodisperse Palladium Tin Nanoparticles with Controlled Composition…
1841
and density of state of metal catalysts, and weaken the
energy of carbon and substituted atoms bond [30, 31],
which probably influences the chemisorption energy of
intermediates on the catalysts. In addition, the NPs with
smaller particle sizes display a higher core-level binding
energy shift and a higher valence band centre downshift
with respect to the Fermi level. According to the density
functional theory of heterogeneous catalysis and mecha-
nistic considerations, the observed valence band centre
downshifts can cause a weakening of the bond strength of
the reactants adsorbed on the catalyst surface, which results
in the increase in the yield of Heck reaction [32]. So
although Sn itself has no catalytic activity, it functions as a
co-catalyst, and the addition of appropriate amount of Sn a
pivotal factor influencing the catalytic performance for
Heck reaction.
Fig. 2 TEM images of Pd63Sn37/C NPs before catalytic reaction
The stability and reusability of Pd63Sn37/C NPs on Heck
reaction were further evaluated. We conducted catalysis
reaction with free standing Pd63Sn37 NPs and found many
of them quickly aggregated with each other during, thus
decreasing the catalytic ability (Fig. 4a). While Pd63Sn37/C
NPs exhibited negligible morphology changes after one
catalysis cycle (Fig. 4b). Then Pd63Sn37/C NPs were sep-
arated, recovered and reused at least six times without
significant loss of catalytic activity (Fig. 5a). The yield of
first recycle was 95 %, which is almost the same after six
cycles, and Pd63Sn37/C NPs after six cycles were charac-
terized by TEM studies (Fig. 4c). We can see that Pd63Sn37
NPs were still well-dispersed on the surface of amorphous
carbon and no great changes happened on their mor-
phologies. While the yields of Heck reaction catalyzed by
PdAg, PdNi, and PdCu NPs are all about 90 % and the
catalytic ability would decrease with the cycles increasing
[17], illustrating that Pd63Sn37 NPs are effective nanocat-
alysts for Heck reactions than the previously reported NPs.
Metal leaching is a serious problem for metal catalysts,
which prohibits their reaction ability, recycling ability and
effectiveness. We monitored Pd leaching of Pd63Sn37/C
NPs during the recycle experiments by analyzing the Pd
concentration in the extraction solution by ICP–AES
analysis. The Pd leaching percentage of Pd63Sn37/C NPs is
corresponding to 0.003 % leaching of the original Pd
content for the first cycle. After the sixth catalytic cycle,
the total Pd leaching is about 0.004 %, indicating that there
is no great increase during the recycle reactions (Fig. 5b).
While Pd/C NPs showed the Pd leaching of about 1.2 % in
the Heck reactions [33]. Pd-silica catalyst-4 reveals that the
leaching of Pd into the solution is about 0.2 ppm [34].
Through the comparations with other nanocatalysts, we
found Pd63Sn37/C NPs are good catalysts for Heck reaction
with little Pd leaching.
100
C-Pd63Sn37
95
C-Pd77Sn23
90
85
C-Pd
80
C-Pd52Sn48
75
70
-5
0
5
10 15 20 25 30 35 40 45 50 55
Sn / %
Fig. 3 Corresponding yield—Sn molar percentage curve for Pd/C
and PdSn/C NPs
reaction are Et3N as the base, DMF as solvent and 140 °C
as reaction temperature. Under the reaction conditions, we
evaluated the influence of PdSn/C alloy composition on
catalytic performances. The correlation of Pd/Sn compo-
sition versus yield is plotted in Fig. 3. For comparison, Pd/
C NPs with the size of 6.3 0.5 nm were prepared
according to previous literatures [27]. Pd/C and PdSn/C
NPs are active nanocatalysts for Heck reaction with the
yields in the range of 71–95 %. For Pd/C, Pd77Sn23/C and
Pd63Sn37/C NPs, the yield increased 80, 87–95 % with Sn
content increasing. However, further increase of Sn to
Pd52Sn48 reduced the yield to 71 %. This demonstrates that
the addition of appropriate amount of Sn can greatly
improve the catalytic performance. The enhancement
probably results from the electronic effect of Sn. The
addition of Sn in our study would lead to a decrease of Pd
(3d) binding energy, change the electronic structure of Pd
We have also conducted the catalyst poisoning experi-
ments to investigate the resistance of Pd63Sn37/C NPs to
123

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Y. Li et al.
Fig. 4 TEM images of unsupported Pd63Sn37 NPs after Heck reaction (a), Pd63Sn37/C NPs after one cycle (b) and Pd63Sn37/C NPs after six
cycles (c)
(a) 100
90
(b)
0.012
0.008
0.004
0.000
-0.004
-0.008
-0.012
80
70
60
50
1
2
3
4
5
6
1
2
3
4
5
6
Cycles
Cycles
Fig. 5 Yield (a) and Pd leaching (b) for Pd63Sn37/C NPs in Heck reaction of bromobenzene with styrene
poison and aging. Pyridines are known to bind strongly to
Pd(II), so pyridines were used as catalyst poison to study
the poison and aging resistance. The details of catalyst
poisoning experiment were as below. 30 equivalents of
pyridine sites were as catalyst poison and added into the
mixture solution of bromobenzene and styrene. During the
reaction, reaction yields were monitored for every 30 min.
For control, the Heck reaction of bromobenzene and styr-
ene were also conducted without catalyst poison, and also
the reaction yields were also monitored for every 30 min.
As shown from Fig. 6, we noticed that the reaction yields
didn’t decrease greatly with the addition of catalyst poison
pyridine. 30 equivalents of pyridine had almost no poi-
soning effect on the Heck reaction of bromobenzene and
styrene, indicating that the Pd63Sn37 NPs possess good
resistance against the catalyst poison and aging, and the
results are similar to the previously reported Pd-SH-SBA-
15 nanocatalyst [35]. In summary, Pd63Sn37/C NPs are
100
80
60
40
20
0
No pyridine
30 equiv. pyridine
0
20
40
60
Time /min
80
100
120
Fig. 6 Plot of yield of Heck reaction of bromobenzene and styrene
catalyzed by Pd63Sn37/C NPs versus time with and without pyridine
as catalyst poison
123

One-Pot Synthesis of Monodisperse Palladium Tin Nanoparticles with Controlled Composition…
Table 1 Different Heck reactions catalyzed by Pd63Sn37/C NPs under optimized conditions
1843
Entry
Ar-X
Alkene
Product
Yield/%a
95
1
2
Br
85
78
Br
MeO C
2
Me
CO2
3
Br
EtO2C
t
E
CO2
4
5
86
65
Br
CO2H
CO2
H
Cl
6
7
98
82
I
Cl
Cl
Br
Br
8
43
NO2
NO2
Reactions were carried out on a 10 mmol scale in 5.0 mL of organic solvent in air for the specified period of 6 h with 1.0 equiv. of Ar–X, 1.2
equiv. of styrene, 2.0 equiv. of base, and Pd63Sn37/C NPs as nanocatalysts
a
Isolated yields
good nanocatalysts for Heck reaction of bromobenzene and
styrene under optimum reaction conditions.
styrene and chlorobenzene and iodobenzene were also
performed, showing the product yields are different. That is
because the electron withdrawing groups facilitate the
process of oxidative addition presumably by lowing the
energy of the r* orbital of benzene–halide bonds (Table 1,
entries 5, 6) [36]. Chemoselectivity was observed when
1-chloro-4-bromobenzene was employed as the reaction
substrate. The reaction was occurred exclusively with aryl
To expand the scope of reaction substrates, different aryl
bromides and olefins were employed in Heck reaction to
investigate the catalytic ability of Pd63Sn37/C NPs, as
shown in Table 1. Heck reaction of bromobenzene with
methyl acrylate, ethyl acrylate, and acrylic acid afforded
good yields (Table 1, entries 2, 3, 4). Heck reactions of
123

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Y. Li et al.
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In summary, we have reported a unique solution phase
synthesis of monodisperse PdSn NPs with the controlled
sizes and compositions, and then their catalytic activities
for Heck reactions were investigated systematically. The
PdSn NPs showed the composition dependent catalytic
ability with Pd63Sn37 being the most active one. The Heck
reaction yield catalyzed by Pd63Sn37/C NPs is as high as
95 %, and the reaction yield is almost the same with the
cycle experiments. All these show that Pd63Sn37/C NPs are
the efficient nanocatalysts for Heck reactions with low
leaching, high stability and reusability, and they are of
great importance for practical applications.
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Acknowledgments This work is supported by Fundamental
Research Funds for the Central Universities (CUG120802).
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