Palladium(II)-phosphine complexes supported on magnetic nanoparticles: Filtration-free, recyclable catalysts for Suzuki-Miyaura cross-coupling reactions

Article abstract of DOI:10.1002/adsc.200900698

An organic-inorganic hybrid heterogeneous nanocatalyst system was synthesized by covalent grafting a palladium dichloride complex of the type (L)₂PdCl₂ (L = trimethoxysilyl-functionalized triphenylphosphine) on silica-coated magnetic nanoparticles. It is a highly active and recyclable catalyst for the Suzuki-Miyaura cross-coupling reaction. The new catalyst can easily be separated from the reaction mixture by applying an external magnetic field and can be recycled many times without any loss of activity.

Full text of DOI:10.1002/adsc.200900698

FULL PAPERS
DOI: 10.1002/adsc.200900698
Palladium(II)-Phosphine Complexes Supported on Magnetic
Nanoparticles: Filtration-Free, Recyclable Catalysts for Suzuki–
Miyaura Cross-Coupling Reactions
Sankaranarayanapillai Shylesh,a Lei Wang,a and Werner R. Thiela,*
a
Fachbereich Chemie, TU Kaiserslautern, Erwin-Schrçdinger-Str., Geb. 54, 67663 Kaiserslautern, Germany
Fax : (+49)-631-205-4676; e-mail: thiel@chemie.uni-kl.de
Received: October 6, 2009; Revised: December 21, 2009; Published online: February 10, 2010
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200900698.
Abstract: An organic-inorganic hybrid heterogene- tion mixture by applying an external magnetic field
ous nanocatalyst system was synthesized by covalent and can be recycled many times without any loss of
grafting a palladium dichloride complex of the type activity.
(L)2PdCl2 (L=trimethoxysilyl-functionalized triphe-
nylphosphine) on silica-coated magnetic nanoparti-
cles. It is a highly active and recyclable catalyst for Keywords: coupling reactions; heterogenization;
the Suzuki–Miyaura cross-coupling reaction. The magnetic nanoparticles; palladium; phosphine li-
new catalyst can easily be separated from the reac- gands
Introduction
the pores of the support. Often the activity of hetero-
genized catalysts was found to be poorer than that of
Palladium-catalyzed Suzuki–Miyaura cross couplings their homogenous analogues.[3] Alternatively, ligand-
of aryl halides and arylboronic acids open up an free palladium catalysts were deveopled by simply
access to biaryl structures which have found applica- supporting Pd(0) or Pd2+ on porous solids.[4] However,
tions in fine chemical and pharmaceuticals synthesis.[1] such systems often suffer from palladium leaching.
A phlethora of palladium-derived catalysts were re-
Notably, the nature of the ligand coordinated to the
ported for this transformation, however, most of them active palladium sites had a profound influence on
are homogenous systems possessing the intrinsic ad- the catalytic activity and stability of the catalyst.
vantages of homogeneous catalysts (single-site reac- Phosphines,[5] amines,[6] carbenes,[7] thiols,[8] pincer li-
tivity, high activity and selectivity, etc.).[2] On the gands,[9] or palladacycles[10] were verified in detail for
other hand, the difficulty to separate a soluble cata- the Suzuki–Miyaura cross-coupling. In particular, tri-
lyst from the reaction mixture gives rise to metal con- phenylphosphine-palladium complexes were widely
tamination in the products and hampers reuse of the used for coupling reactions mainly due to the simple
expensive noble metal. Thus, a facile and efficient handling of these complexes and the cheap phosphine
separation of expensive catalysts and their consecu- ligand.[11] Besides, some heterogeneous systems re-
tive reuse remains a scientific challenge in terms of quire the addition of phosphine ligands such as PPh3
economic and environmental considerations.
to reach reasonable catalytic activity.[12] Therefore, the
The recovery of an expensive catalyst, often synthe- heterogenization of triphenylphosphine-palladium
sized by multi-step procedures, can be realized by im- complexes was extensively investigated. However, the
mobilization on solid supports. During the past years benefits related to the separation of the catalyst and
palladium catalysts heterogenized on organic poly- its reuse are reduced by the moderate activity of such
mers or inorganic solid supports such as zeolites and systems, since a pronounced part of the active sites is
mesoporous materials were systematically investigat- not easily available for the reactants.[13] Thus there is
ed. However, a substantial decrease of the reaction still a demand to develop new protocols for ecologi-
À
rates, compared to homogeneous systems, had fre- cally benign C C couplings which should fulfill the
quently to be considered due to limitations related to following requirements: a low amount of catalyst,
the diffusion of the substrates and products through high activity and selectivity, and an efficent recycling
Adv. Synth. Catal. 2010, 352, 425 – 432
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
425

Sankaranarayanapillai Shylesh et al.
FULL PAPERS
and reuse of the catalyst with consistent yields over a Results and Discussion
large number of experiments.
Nanoparticles that can be magnetized in the pres- For this purpose, we synthesized magnetic nanoparti-
ence of an external magnet had first been explored cles (MNP) of approximately 10 nm in diameter by a
for biological and medicinal applications.[14] Recently co-precipitation method. The particles were subse-
they also emerged as efficient catalyst supports for quently coated with a dense silica layer, using tetra-
[15]
C C bond-forming reactions, hydrogenation,[16] hy-
ACHTUNGTRENeNGNU thoxysilane (TEOS) as the silica source and aqueous
À
droformylation,[17] oxidation[18] and organocatalytic[19] NH3 as the hydrolyzing agent. The silica layered
reactions. Due to the small particle size they possess system SMP then offers the binding sites (Si OH
À
high specific surface areas without porosity. This units) for the heterogenization of the molecular cata-
makes the catalytically active sites on the surface well lysts. The silylated derivative 2 of triphenylphosphine
accessible for the reactants. Since there is almost no was achieved as reported by the solvent-free,
limitation by diffusion, catalytic nanoparticles can be NaOMe-catalyzed thermal aminolysis of 4-diphenyl-
considered as quasi-homogeneous systems. Moreover, phosphinylbenzenecarboxylic acid methyl ester (1)
magnetic nanoparticles can simply be removed from with 3-trimethoxysilylpropylamine. The formation of
the reaction mixture by application of a magnetic the palladium(II)-phosphine complex (3) was realized
field (magnetic filtration).
by simply dissolving 2 in CH2Cl2 and treating it with
In continuing our efforts to develop greener syn- half an equivalent of di(benzonitrile)dichloropalla-
thetic pathways for organic transformations,[20] we
here report the synthesis of a novel, highly active,
ACHTUNGTRENNUNG
magnetically recoverable palladium-phosphine cata- process, two phosphine ligands are coordinated to one
lyst for the Suzuki–Miyaura cross-coupling. Its activity palladium centre. The catalytically active system
and stability were evaluated by comparison with simi- Pd@SMP is then accessible by reacting SMP with 3 in
lar active sites grafted on a conventional silica gel and toluene at 908C.
a mesoporous MCM-41 support. Compared to palla-
High-resolution transmission electron microscopy
dium grafted on magnetic nanoparticles by simple li- (HR-TEM) images of the MNPs depict relatively uni-
gands like amines or thiols,[6,8] the heterogenity is form g-Fe2O3 particles with an average size of
guarenteed in our system (Scheme 1). At the outset ~10 nm. TEM images of the silica-coated SMP show
of this study no example of a magnetic nanoparticle- the typical core-shell structure with a uniform silica
supported palladium-phosphine complex was reported coating and a mean thickness of approximately 50 nm
despite the inherent high activity of such complexes (see Supporting Information). The dense silica shell
in various coupling reactions.
prevents leaching of iron from the core during the
catalytic reactions and also assists in a stable anchor-
ing of the silylated palladium complexes (Figure 1).
FE-SEM images showed the spherical morphology of
Pd@SMP with slight aggregation and spongy surfaces
confirming the successful coating of MNP by a dense
silica layer (Figure 1). Energy dispersive X-ray
(EDX) analysis carried out with SMP showed the
presence of silica and iron, while after the grafting re-
action the presence of palladium was noted on
Pd@SMP, confirming the successful anchoring of the
palladium-phosphine complexes on the magnetic
nanoparticles. Besides, elemental mapping analysis
proves that the palladium species are uniformly dis-
persed over the magnetic silica nanocomposites (see
Supporting Information).
XRD measurements of MNP exhibit diffraction
peaks corresponding to the typical spinel maghemite
structure while the silica-layered systems SMP and
Pd@SMP showed an additional broad band (2q=20–
30) for the amorphous silica (Figure 2). The average
crystallite size of the g-Fe2O3 particles was calculated
to be ~9.3 nm by Scherrerꢁs equation for the (311) re-
flection, which is in well accordance with the HR-
TEM results. No peaks characteristic for palladium
nanoparticles were observed which proves the excel-
Scheme 1. Synthesis of the palladium(II)-triphenylphosphine
complex 3 functionalized with two trimethoxysilyl side
chains.
426
asc.wiley-vch.de
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 425 – 432

Palladium(II)-Phosphine Complexes Supported on Magnetic Nanoparticles
Figure 1. HR-TEM and FE-SEM images of Pd@SMP.
À1
À
appears for the Si O vibration at 1080 cm . In the
À
IR spectrum of Pd@SMP absorptions at 3300 (N H),
2930 cmÀ1 (CH2), 1640 cmÀ1 (C=O) and a weak amide
band at 1540 cmÀ1 were observed indicating the pres-
ence of silylated palladium-phosphine groups (see
Supporting Information).[21] By determination of the
nitrogen content (C,H,N elemental analysis), a palla-
dium-phosphine complex loading of approximately
0.20 mmolgÀ1 was calculated for Pd@SMP. To confirm
alternatively the structural integrity after the grafting
processes, compound 3 was grafted on a silica gel sup-
port and the stability of this system was analyzed by
solid state 31P MAS NMR spectroscopy (see Support-
ing Information). The results confirm the retention
and stability of the palladium-phosphine precusor (3):
the phosphorus resonance of 3 (24.6 ppm) is only
slightly shifted in comparison to 23.6 ppm for the
silica gel-supported palladium-phosphine complex
Pd@SG.
Figure 2. XRD patterns of (a) MNP, (b) SMP and (c)
Pd@SMP.
lent dispersion of the palladium sites on the magnetic
The
magnetically
separable
nanocomposite
silica nanocomposites. The field-dependent magneti- Pd@SMP was then used as catalyst for the Suzuki–
zation curve at 300 K of the magnetic nanoparticles Miyaura cross-coupling of phenyl halides and phenyl-
investigated by SQUID magnetometry, shows no hys- boronic acid (Scheme 2).
teresis revealing that the materials exhibit superpara-
Initial experiments with bromobenzene and phenyl-
magnetic behaviour at room temperature with a satu- boronic acid were performed to optimize the reaction
ration magnetization (Ms) of 50 emugÀ1 and conditions (base, solvent, reaction temperature). As
18 emugÀ1 for MNP and SMP, respectively, whereas shown in Table 1 and Table 2, Cs2CO3 gave better
Mçssbauer spectroscopy identifies the superparamag- conversions than other bases like K2CO3, Na2CO3, KF
netic particles as g-Fe2O3 since there is no evidence or CH3COONa and dioxane and DMF are the first
for spectral components representing Fe(II) ions.[20d]
The presence of magnetic iron oxide inside
Pd@SMP prevents the analysis of organic functional
groups by solid state NMR spectroscopy. Therefore,
these hybrid materials were further analyzed by IR
spectroscopy and elemental analysis. The IR spectrum
choice among a series of other solvents. The solvent
À
of MNP shows the Fe O stretching absorption at
Scheme 2. Suzuki–Miyaura cross coupling of aryl halides
576 cmÀ1. After coating with silica a new sharp band and phenylboronic acid in presence of Pd@SMP.
Adv. Synth. Catal. 2010, 352, 425 – 432
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
427

Sankaranarayanapillai Shylesh et al.
FULL PAPERS
Table 1. Suzuki–Miyaura coupling of phenyl bromide and
Table 3. Substrate scope of the Suzuki–Miyaura coupling
phenylboronic acid using different bases.[a]
with phenylboronic acid.[a]
Base
Cs2CO3 K2CO3 KF Na2CO3 CH3COONa
Entry Substrate
Product
Yield [%]
>99 (96)
>99 (95)
34
Yield [%][b] >99
71
62 47
42
1
2
3
4
[a]
Reaction conditions: PhBr (1 mmol), PhB(OH)2
(1.5 mmol), base (1.2 mmol), catalyst (1 mol%), dioxane
(5 mL), 808C, 15 h.
Determined by GC-MS using n-decane as the internal
standard.
[b]
73
5
6
90 (83)
93
Table 2. Suzuki–Miyaura coupling of phenyl bromide and
phenylboronic acid using different solvents.[a]
Solvent
dioxane
DMF
95
DMA
91
EtOH
63
THF
34
Yield [%]
>99
7
35
[a]
Reaction conditions: PhBr (1 mmol), PhB(OH)2
(1.5 mmol), Cs2CO3 (1.2 mmol), catalyst (1 mol%), sol-
vent (5 mL), 808C, 15 h.
8
9
24
93
effect is probably determined by the solubility of the
base. Reducing the amount of catalyst 0.5 mol% still
gives a good yield of coupled products (see Support-
ing Information). Since biphenyl might result from a
cross-coupling or homo-coupling reaction, we used 4-
bromoacetophenone to prove the chemoselectivity of
the catalyst. The formation of the homo-coupled
product was not significant under the given reaction
conditions (<5%).
Further optimization studies revealed that the cata-
lysts were inactive at room temperature, while heating
the mixture to 80–1008C gave high conversions. In-
creasing the reaction temperature to >1208C decreas-
es the activity of the catalysts (<50% of conversion
after 15 h) probably due to decomposition of the pal-
ladium-phosphine sites.
10
11
89 (80)
75
73
12[b]
[a]
Reaction conditions: substrate (1 mmol), PhB(OH)2
(1.5 mmol), Cs2CO3 (1.2 mmol), Pd (1 mol%), solvent
(5 mL), 808C, 15 h; values in parenthesis shows the iso-
lated yield.
With the optimized reaction conditions (Cs2CO3, di-
oxane, 808C, 15 h) we examined the scope of the pal-
[b]
Selectivity: 41% for binary and 59% for ternary product.
ladium-catalyzed Suzuki–Miyaura coupling on
a
series of different substrates (Table 3). Control ex-
À
periments carried out in the absence of Pd@SMP con- couple 2-substituted Ar X derivatives gave the de-
firmed the crucial role of palladium (0% of conver- sired products in only low yields probably due to the
sion after 24 h). The coupling of phenyl iodide and steric hindrance (entries 7 and 8). Only 1-bromo-2-
phenyl bromide with phenylboronic acid afforded the methylnaphthalene could be converted with high ac-
formation of biphenyl in >99% yield. Notably, the tivity. The Br Ar Br substrate 1,4-dibromobenzene
less reactive and less expensive phenyl chloride also gave 73% of conversion with selectivities of 41% and
showed moderate reactivity in the presence of 59% for 4-bromobiphenyl and terphenyl.
À
À
Pd@SMP. Various 4-substituted aryl bromides as well
For the practical application of a heterogeneous
as heteroaromatic substrates like iodothiophene also catalyst system its stability and reusability are impor-
led to high yields of coupled products. The reaction tant factors. The literature demonstrates that many
rate is clearly influenced by the impact of other sub- immobilized catalysts behave homogeneously in their
À
stitutents at Ar X: electron-withdrawing groups en- reactions (leaching of the active site), which is partic-
hance, while electron-donating groups decrease the ularly true for palladium-based systems.[22] To ensure
rate (e.g., Table 3, entry 4 vs. entry 5). Attempts to that the high activity of Pd@SMP arises from the pal-
428
asc.wiley-vch.de
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 425 – 432

Palladium(II)-Phosphine Complexes Supported on Magnetic Nanoparticles
ladium sites on the surface and not from the leached
palladium species, the heterogenity of Pd@SMP was
first tested by hot filtration. For this, the coupling re-
action of phenyl bromide and phenylboronic acid was
carried out until a conversion of 30%. Then the cata-
lyst was separated magnetically from the solution at
the reaction temperature and half of the hot solution
was transferred to another batch reactor set under
identical reaction conditions. The portion containing
the suspended catalyst proceeded to 99% of conver-
sion where as the catalyst-free portion reacted only to
an additional 10% after 15 h. This shows that the
leaching of palladium from the magnetic silica nano-
composite is not a serious concern. However, as
shown in Table 4, the reactivity of Pd@SMP slightly
Figure 4. Magnetofiltration of finely dispersed superpara-
magnetic Pd@SMP nanoparticles (left: before application of
the magnet; right: 2 min later).
reduces after the first run and then stays constant. We
assign this to a slight leaching process parallel to the
formation of palladium nanoparticles, which carry on
the reactivity from the second run (Figure 3).
For investigations on the recyclability of the cata- tion of sensitive metal complexes. Pd@SMP could be
lyst, it was recovered by magnetic separation, washed reused seven times by simple magnetic separation
three times with an ethanol/CH2Cl2 mixture, dried in almost without any deterioration in catalytic activity
air and reused for the next reaction. More than 98% (Table 4). In our opinion, the high catalytic activity
of the catalyst could simply be recovered by fixing a and stability of the palladium catalyst relates to the
magnet near to the reaction vessel (Figure 4). This efficient site isolation, to the optimal dispersion of the
method avoids the inherent problems of filtration active sites on the particle surface and to the relative-
such as loss of catalytically active particles and oxida- ly strong interaction between the phosphine ligands
and the palladium centre supported on the magnetic
silica nanoparticles. Due to the preformation of the
palladium(II)-phosphine complex all phosphines are
grafted on the surface in a ideal position for complex-
ing the palladium centre. In combination with the sur-
face they can be considered as a chelating ligand
system.
Table 4. Reusability test for Pd@SMP in the Suzuki–
Miyaura coupling of phenyl bromide and phenylboronic
acid.[a]
Recycle
I
II
III
94
IV
94
V
VI
93
VII
92
Yield [%]
>99
94
93
In a previous study we noted that a catalyst system
wherein the palladium(II)-phosphine complex 3 is
simply grafted on a commercially available silica
turns gradually darker during its consecutive reuse.[20a]
This effect arises from the presence of metallic palla-
dium nanoparticles and is well documented in the lit-
erature for various palladium-ligated catalysts.[23]
However, the presence of the phosphines in ideal po-
sitions on the silica surface assists in the stabilization
of the nanoparticles and hence they do not diffuse
into the reaction mixture (Figure 3). To confirm this,
we had anayzed the used Pd@SG catalyst by means
of 31P MAS NMR spectroscopy. The 31P MAS NMR
spectrum (see Supporting Information) shows sharp
signals at 33.5 ppm and 3.9 ppm with a weak shoulder
at À3.1 ppm. These results prove that the phosphine
ligands gets partially oxidized to phosphine oxide
(peak at 33.5 ppm) whereas the peak at 3.9 ppm is as-
signed to triphenylphosphine ligands coordinated to
the palladium(0) nanoparticles and the weak shoulder
at À3.1 ppm arises for palladium-free phosphine li-
gands. However, the triphenylphosphine ligand as
well as phosphine oxide developed during the reac-
[a]
Reaction conditions: PhBr (1 mmol), PhB(OH)2
(1.5 mmol), Cs2CO3 (1.2 mmol), Pd (1 mol%), solvent
(5 mL), 808C, 15 h.
Figure 3. TEM image of heterogenized palladium nanoparti-
cles after a third recycling.
Adv. Synth. Catal. 2010, 352, 425 – 432
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
429

Sankaranarayanapillai Shylesh et al.
FULL PAPERS
tion are able to assist in the stabilization of palladium Conclusions
nanoparticles which, in turn, explains the good reusa-
bility of this catalyst system.
To summarize, it could be shown that Pd@SMP ob-
Furthermore, it has been reported that metal nano- tained by grafting of the palladium(II)-phosphine
particles aggregate into large clusters in the absence complex 3 on magnetic silica nanoparticles is an effi-
of stabilizing agents, resulting in a decrease of their cient and simply recoverable catalyst for the Suzuki–
specific surface area, which is equivalent to a loss of Miyaura cross-coupling reaction. The synthesis of the
active sites and thus one main reason for catalyst de- nanocomposite is straightforward and there is no deg-
activation. The consistent catalytic performance of radation of activity during multiple reuse. We antici-
Pd@SMP again proves the stabilization of the palla- pate that this synthesis strategy can now be extended
ACHTUNGTRENNUNGdium nanoparticles and explains the excellent reusa- for the heterogenization of other homogenous li-
bility of this catalyst system. The amount of palladium gands/catalysts, which we are presently investigating.
and ligand on the reused catalyst is identical to that
of the fresh catalyst. AAS analysis only showed
<0.5% of leached palladium in the reaction filtrate Experimental Section
and elemental analysis data confirmed the retention
of the phosphine/phosphine oxide ligands on the sur- Synthesis of the Magnetic Nanoparticles (MNP)
face after catalyst recycling. On the other hand, a
Ferrous chloride (0.25 g) and ferric chloride (0.5 g) were
direct grafting of palladium species on the magnetic
added under stirring to 20 mL of a nitrogen purged 2-propa-
silica nanoparticles by application of PdCl2ACTHNUTRGNEN(UG PhCN)2
nol solution resulting in a yellowish orange reaction mixture.
After 15 min of stirring, the temperature of the solution was
raised to 808C and 10 mL of aqueous NH3 were slowly
added. The colour of the solution turned to dark brown and
the stirring was continued for another 2 h. The magnetic
nanoparticles formed were protected by the addition of
10 mM of oleic acid in 30 mL methanol, removed from the
solution by magnetic separation, washed with methanol and
then redispersed in ethanol.
leads to severe leaching of active sites during the re-
cycling (a 50% conversion in first run changed to zero
activity for the second run) which additionally con-
firms the stabilizing role of the phosphine ligands.
To compare the activity and stability of Pd@SMP,
the palladium(II)-phosphine precursor (3) was hetero-
genized on two further supports: a commercially
available silica gel (Pd@SG) and a mesoporous
MCM-41 sample (Pd@MCM-41). It could be shown
that activity and stability of the three catalysts follows
Synthesis of the Silica-Coated Magnetic
NanoACTHUNRTGNEUNGparticles (SMP)
the
order
Pd@SMP>Pd@MCM-41>Pd@SG
(Table 5). Obviously the high catalytic activity of
Pd@SMP arises from its unique quasi-homogeneous
nature due to its nanoscale particle size and the loca-
tion of the active sites on the surface of a dense and
almost non-porous silica shell, which prevents limitat-
ing effects of diffusion. Alternatively, we tried to com-
pare the results obtained from a magnetic nanoparti-
cle-supported NHC-Pd(II) complex with our
Pd@SMP catalyst under similar experimental condi-
tions.[15a] The Pd@SMP shows an only slightly reduced
performance compared to heterogenized NHC-Pd(II)
catalyst (see Supporting Information).
2 g of a suspension of MNP in ethanol were diluted with
4 mL of deionized water and 20 mL of 2-propanol and the
mixture was sonicated for approximately 5 min. To this well
dispersed MNP solution, 1 mL of NH4OH followed by 1 g
of tetraethoxysilane was slowly added and stirred for further
4 h at room temperature. The material was then separated
by centrifugation and redispersed in deionized water.
4-Diphenylphosphinylbenzenecarboxylic Acid 4-[N-
(3-Trimethoxysilypropyl)amide] (2)
1.27 g (3.97 mmol) of 1 and 0.021 g (0.397 mmol) of NaOMe
were mixed with 0.71 g (3.97 mmol) of 3-trimethoxysilylpro-
pylamine and heated to 1708C for 4 h. After cooling to
room temperature, all volatiles were removed under vacuum
and the residue was dissolved in CH2Cl2. After removing
the solvent, 1.67 g of 2 were obtained as a yellow oily resi-
due. The spectroscopic data were in accordance with the
published data.[20a]
Table 5. Suzuki–Miyaura coupling of phenyl bromide and
phenylboronic acid using different supports.[a]
Entry
Sample
Yield [%]
1st run
4th run
Dichloridobis{(4-diphenylphosphinylbenzene-
carboxylic Acid 4-[N-(3-
Trimethoxysilypropyl)amide]}palladium(II) (3)
1
2
3
Pd@SMP
>99
88
85
94
78
73
Pd@MCM-41
Pd@SG[b]
[a]
Reaction conditions: PhBr (1 mmol), PhB(OH)2
(1.5 mmol), Cs2CO3 (1.2 mmol), Pd (1 mol%), solvent
(5 mL), 808C, 15 h.
178 mg (0.46 mmol) of di(benzonitrile)dichloropalladium(II)
dissolved in 30 mL of dry CH2Cl2 were added to a solution
of 430 mg (0.92 mmol) of 2 in 10 mL of CH2Cl2. The reac-
tion mixture was stirred for 4 h at room temperature and
[b]
From ref.[20a]
430
asc.wiley-vch.de
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 425 – 432

Palladium(II)-Phosphine Complexes Supported on Magnetic Nanoparticles
the filtrate was evaporated to dryness under reduced pres-
sure. The residue was washed with ether to obtain a pale
yellow solid. The spectroscopic data were in accordance
with the published data.[20a]
deVries, Chem. Commun. 2004, 1559; f) A. F. Schmidt,
V. V. Smirnov, Top. Catal. 2005, 32, 71; g) M. Choi,
D-H. Lee, K. Na, B.-W. Yu, R. Ryoo, Angew. Chem.
2009, 121, 3727; Angew. Chem. Int. Ed. 2009, 48, 3673.
[5] a) N. E. Leadbeater, M. Marco, Chem. Rev. 2002, 102,
3217; b) C. A. McNamara, M. J. Dixon, M. Bradley,
Chem. Rev. 2002, 102, 3275.
Synthesis of Pd@SMP, Pd@MCM-41 and Pd@SG
0.15 g of 3 dissolved in 5 mL of dry CH2Cl2 were added to a
suspension of 0.3 g of SMP in 30 mL of dry toluene. The
mixture was then stirred at 908C under an atmosphere of ni-
trogen for 12 h. The solid material obtained was magnetical-
ly separated, washed repeatedly with toluene and CH2Cl2 to
remove any unanchored species and then dried under
vacuum.
A similar procedure was adopted for the grafting of 3 on
MCM-41 and silica gel giving 0.22 mmolgÀ1 and
0.20 mmolgÀ1 loading of the palladium(II)-phosphine com-
plex, respectively. The catalyst loadings were determined by
elemental analysis.
[6] a) V. Polshettiwar, M. N. Nadagouda, R. S. Varma,
Chem. Commun. 2008, 6318; b) B. Baruwati, D. Guin,
S. V. Manorama, Org. Lett. 2007, 9, 5377.
[7] a) J. Schwarz, V. P. W. Bçhm, M. G. Gardiner, M. Gro-
sche, W. A. Herrmann, W. Hieringer, G. Raudaschl-
Sieber, Chem. Eur. J. 2000, 6, 1773.
[8] a) K.-I. Shimizu, S. Koizumi, T. Hatamachi, H. Yoshida,
S. Komai, T. Kodama, Y. Kitayama, J. Catal. 2004, 228,
141; b) C. M. Crudden, M. Sateesh, R. Lewis, J. Am.
Chem. Soc. 2005, 127, 10045.
[9] W. A. Herrmann, C. Brossmer, K. Oefele, C.-P. Rei-
singer, T. Priermeier, M. Beller, H. Fischer, Angew.
Chem. 1995, 107, 1989; Angew. Chem. Int. Ed. Engl.
1995, 34, 1844.
[10] a) C. Baleizao, A. Corma, H. Garcia, A. Leyva, Chem.
Commun. 2003, 606; b) C. Baleizao, A. Corma, H.
Garcia, A. Leyva, J. Org. Chem. 2004, 69, 439.
Acknowledgements
[11] a) B. M. Trost, E. Keinan, J. Am. Chem. Soc. 1978, 100,
7779; b) K. Hamza, R. Abu-Reziq, D. Avnir, J. Blum,
Org. Lett. 2004, 6, 925; c) A. Talhami, L. Penn, N.
Jaber, K. Hamza, J. Blum, Appl. Catal. A: Gen. 2006,
312, 115.
[12] a) R. Akiyama, S. Kobayashi, J. Am. Chem. Soc. 2003,
125, 3412.
[13] a) C. M. Andersson, K. Karabelas, A. Hallberg, C. An-
dersson J. Org. Chem. 1985, 50, 3891; b) K. Inada, N.
Miyaura, Tetrahedron 2000, 56, 8661; c) Y. Uozumi, Y.
Nakai, Org. Lett. 2002, 4, 2997.
The Alexander von Humboldt-Foundation is gratefully ac-
knowledged for a research grant to S.S. This work was further
supported by the joint research project “NanoKat” at the TU
Kaiserslautern. We thank A. Wagener and Prof. S. Ernst,
Fachbereich Chemie, TU Kaiserslautern, Prof. V. Schꢀne-
mann, Fachbereich Physik, TU Kaiserslautern and Dr. S. De-
meshko, Anorganisch-chemisches Institut, Georg-August-
Universitꢁt, Gçttingen for XRD, Mçssbauer and SQUID
measurements.
[14] a) I. J. Bruce, J. Taylor, M. Todd, M. J. Davies, E. Bori-
oni, C. Sangregorio, T. Sen, J. Magn. Magn. Mater.
2004, 284, 145; b) P. J. Robinson, P. Dunnill, M. D.
Lilly, Biotechnol. Bioeng. 1973, 15, 603; c) G. M. White-
sides, R. J. Kazlauskas, I. Josephson, Trends Biotechnol.
1983, 1, 144; d) A. K. Gupta, M. Gupta, Biomaterials
2005, 26, 3995.
[15] a) P. D. Stevens, G. Li, J. Fan, M. Yen, Y. Gao, Chem.
Commun. 2005, 4435; <lit b>P. D. Stevens, J. Fan,
H. M. R. Gardimalla, M. Yen, Y. Gao, Org. Lett. 2005,
7, 2085; c) Y. Zheng, P. D. Stevens, Y. Gao, J. Org.
Chem. 2006, 71, 537; d) H. Yoon, S. Ko, J. Jang, Chem.
Commun. 2007, 1468; e) G. Chouhan, D. Wang, H.
Alper, Chem. Commun. 2007, 4809.
[16] a) C.-H. Jun, Y. J. Park, Y.-R. Yeon, J.-R. Choi, W.-R.
Lee, S.-J. Ko, J. Cheon, Chem. Commun. 2006, 1619;
b) D. K. Yi, S. S. Lee, J. Y. Ying, Chem. Mater. 2006, 18,
2459; c) L. M. Rossi, F. P. Silva, L. L. R. Vono, P. K.
Kiyohara, E. L. Duarte, R. Itri, R. Landers, G. Macha-
do, Green Chem. 2007, 9, 379.
[17] a) T.-J. Yoon, W. Lee, Y.-S. Oh, J.-K. Lee, New J.
Chem. 2003, 27, 227; b) R. Abu-Reziq, H. Alper, D.
Wang, M. L. Post, J. Am. Chem. Soc. 2006, 128, 5279.
[18] a) F. Shi, M. K. Tse, M. M. Pohl, A. Brꢂckner, S.
Zhang, M. Beller, Angew. Chem. 2007, 119, 9022;
Angew. Chem. Int. Ed. 2007, 46, 8866; b) M. Kotani, T.
Koike, K. Yamaguchi, N. Mizuno, Green Chem. 2006, 8,
References
[1] a) N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457;
b) A. Suzuki, J. Organomet. Chem. 1999, 576, 147; c) A.
Suzuki, Chem. Commun. 2005, 4759; d) L. Yin, J.
Liebscher, Chem. Rev. 2007, 107, 133; e) M. Moreno-
Manas, R. Pleixats, Acc. Chem. Res. 2003, 36, 638.
[2] a) C. E. Garrett, K. Prasad, Adv. Synth. Catal. 2004,
346, 889; b) J. Le Bars, U. Specht, J. S. Bradley, D. G.
Blackmond, Langmuir 1999, 15, 7621.
[3] a) N. T. S. Phan, M. Van der Sluys, C. W. Jones, Adv.
Synth. Catal. 2006, 348, 609; b) H.-U. Blaser, A. Indo-
lese, A. Schnyder, H. Steiner, M. Studer, J. Mol. Catal.
A: Chem. 2001, 173, 3; c) C. Rocaboy, J. A. Gladysz,
New J. Chem. 2003, 27, 39; d) C. Rocaboy, J. A. Gla-
dysz, Org. Lett. 2002, 4, 1993; e) K. Yu, W. Sommer,
J. M. Richardson, M. Weck, C. W. Jones, Adv. Synth.
Catal. 2005, 347, 161; f) T. Rosner, A. Pfaltz, D. G.
Blackmond, J. Am. Chem. Soc. 2001, 123, 4621; g) S.
Paul, J. H. Clark, J. Mol. Catal. A: Chem. 2004, 215,
107.
[4] a) L. Djakovitch, K. Kçhler, J. Am. Chem. Soc. 2001,
123, 5990; b) A. Corma, H. Garcia, A. Leyva, A.
Primo, Appl. Catal. A: Gen. 2003, 247, 41; c) C. P. Meh-
nert, D. W. Weaver, J. Y. Ying, J. Am. Chem. Soc. 1998,
120, 12289; d) K. Kçhler, M. Wagner, L. Djakovitch,
Catal. Today 2001, 66, 105; e) M. T. Reetz, J. G.
Adv. Synth. Catal. 2010, 352, 425 – 432
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
431

Sankaranarayanapillai Shylesh et al.
FULL PAPERS
735; c) M. Shokouhimehr, Y. Piao, J. Kim, Y. Jang, T.
Hyeon, Angew. Chem. 2007, 119, 7169; Angew. Chem.
Int. Ed. 2007, 46, 7039; d) K. Mori, S. Kanai, T. Hara,
T. Mizugaki, K. Ebitani, K. Jitsukawa, K. Kaneda,
Chem. Mater. 2007, 19, 1249.
lesh, J. Schweizer, S. Demeshko, V. Schꢂnemann, S.
Ernst, W. R. Thiel, Adv. Synth. Catal. 2009, 351, 1789.
[21] a) M. C. Burleigh, M. A. Markowitz, M. S. Spector,
B. P. Gaber, J. Phys. Chem. B: 2001, 105, 9935; b) Z.
Zhou, A. W. Franz, M. Hartmann, A. Seifert, T. J. J.
Mꢂller, W. R. Thiel, Chem. Mater. 2008, 20, 4986.
[22] a) K. Glegola, E. Framery, K. M. Pietrusiewicz, D.
Sinou, Adv. Synth. Catal. 2006, 348, 1728; b) R. B. Bed-
ford, S. J. Coles, M. B. Hursthouse, V. J. M. Scordia,
Dalton Trans. 2005, 991; c) F. Zhao, B. M. Bhanage, M.
Shirai, M. Arai, Chem. Eur. J. 2000, 6, 843; d) A. F.
Littke, G. C. Fu, Angew. Chem. 2002, 114, 4350;
Angew. Chem. Int. Ed. 2002, 41, 4176.
[19] a) V. Polshettiwar, B. Baruwati, R. S. Varma, Chem.
Commun. 2009, 1837; b) M. Kawamura, K. Sato, Chem.
Commun. 2007, 3404; c) C. S. Gill, B. A. Price, C. W.
Jones, J. Catal. 2007, 251, 145; d) C. O. ꢃ Dꢄlaigh, S. A.
Corr, Y. Gun’ko, S. J. Connon, Angew. Chem. 2007,
119, 4407; Angew. Chem. Int. Ed. 2007, 46, 4329.
[20] a) L. Wang, A. Reis, A. Seifert, T. Philippi, S. Ernst, M.
Jia, W. R. Thiel, Dalton Trans. 2009, 3315; b) S. Shy-
lesh, A. Wagener, A. Seifert, S. Ernst, W. R. Thiel,
Chem. Eur. J. 2009, 15, 7052; c) Z. Zhou, Q. Meng, A.
Seifert, A. Wagener, Y. Sun, S. Ernst, W. R. Thiel, Mi-
croporous Mesoporous Mater. 2009, 121, 145; d) S. Shy-
[23] a) M. Trilla, R. Pleixats, M. Wong Chi Man, C. Bied,
J. J. E. Moreau, Adv. Synth. Catal. 2008, 350, 577; b) J.
Gil-Molto, S. Karlstrom, C. Najera, Tetrahedron 2005,
61, 12168.
432
asc.wiley-vch.de
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 425 – 432