Hybrid organic-inorganic materials from di-(2-pyridyl)methylamine-palladium dichloride complex as recoverable catalysts for Suzuki, Heck and Sonogashira reactions

Article abstract of DOI:10.1002/adsc.200700489

Hybrid silica materials containing the di-(2-pyridyl)methylamine-palladium dichloride complex, prepared by sol-gel cogelification, are efficient recyclable catalysts for Suzuki (aryl bromides and chlorides), Heck (aryl bromides) and Sonogashira reactions (aryl iodides and bromides). Formation of palladium(0) nanoparticles is observed in the Suzuki and Heck reactions but not in the Sonogashira coupling.

Full text of DOI:10.1002/adsc.200700489

FULL PAPERS
DOI: 10.1002/adsc.200700489
Hybrid Organic-Inorganic Materials fromDi-(2-pyridyl)methyl-
A
for Suzuki, Heck and Sonogashira Reactions
Montserrat Trilla,a Roser Pleixats,a,* Michel Wong Chi Man,b,* Catherine Bied,b
and Jol J. E. Moreaub
a
Chemistry Department, Universitat Autònoma de Barcelona, Cerdanyola del Vall›s, 08193 Barcelona, Spain
Fax : (+34)-9-3581-1265; e-mail: roser.pleixats@uab.es
Institut Charles Gerhardt Montpellier (UMR 5253 CNRS-UM2-ENSCM-UM1), Architectures MolØculaires et MatØriaux
b
NanostructurØs, Ecole Nationale SupØrieure de Chimie de Montpellier, 8 rue de l’Øcole normale, 34296-Montpellier cØdex
5, France
Fax : (+33)-4-6714-7212; e-mail: michel.wong-chi-man@enscm.fr
Received: October 8, 2007; Revised: December 21, 2007; Published online: February 25, 2008
Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/.
Abstract: Hybrid silica materials containing the di- and Heck reactions but not in the Sonogashira cou-
(2-pyridyl)methylamine-palladium dichloride com- pling.
plex, prepared by sol-gel cogelification, are efficient
recyclable catalysts for Suzuki (aryl bromides and
chlorides), Heck (aryl bromides) and Sonogashira re- Keywords: catalyst immobilization; C C coupling;
actions (aryl iodides and bromides). Formation of organic-inorganic hybrid materials; palladium; sol-
palladium(0) nanoparticles is observed in the Suzuki gel process
À
Introduction
our heterogenized macrocyclic palladium(0) com-
plexes was that they were efficient in Suzuki cou-
Palladium-catalyzed carbon-carbon bond forming pro- plings with activated and deactivated aryl iodides but
cesses such as the Suzuki–Miyaura[1] cross-coupling, not for the more challenging aryl bromides and chlor-
Heck[2] and Sonogashira[3] reactions are key steps in ides, the ideal substrates for coupling reactions being
the synthesis of natural products and a great variety the more eco-friendly aryl chlorides.[9]
of complex organic molecules used in many fields,
Several phosphane-free palladium systems have
such as drugs, agrochemicals or in materials science. been reported as robust and efficient catalysts or pre-
On the other hand, the heterogenization of homoge- catalysts (high TON and TOF)[10] for the coupling re-
neous catalysts by their immobilization on polymeric actions with aryl chlorides (palladacycles, N-heterocy-
organic[4] or inorganic[5] supports offers the advantag- clic carbenes and bipyridine-based systems). We fo-
es of easy product separation and catalyst recycling. cused our attention on bipyridin-2-ylmethane-type li-
Phosphanes are common ligands used in palladium- gands to prepare immobilized palladium catalysts
catalyzed processes, but they are readily oxidized to onto a silica matrix. Such inorganic supports consti-
their corresponding phosphane oxides, which can pre- tute an interesting alternative for the preparation of
vent the easy recovery and reuse of the catalytic sys- heterogeneous catalysts because of their mechanical
tems. Thus, phosphane-free palladium catalysts have and thermal stability and chemical inertia.[11] The for-
superior stability.
mation of organic-inorganic hybrids by sol-gel chemis-
Some of us discovered[6] air- and moisture-stable try[12] is a convenient route to solid materials with cat-
phosphane-free macrocyclic triolefinic palladium(0) alytic properties.[5,13]
complexes. We have described their immobilization
Palladium(II) complexes of di-2-pyridylamine-de-
onto cross-linked polystyrene,[7] and onto a silica rived ligands 1 (Figure 1) have been developed by
matrix,[8] and the activity of these supported versions Buchmeiser[14] as catalysts for C C and C N bond
as recyclable catalysts in Suzuki cross-couplings and formation and they have been covalently grafted to a
À
À
telomerization reactions. However, the drawback of matrix resulting from
a
ROMP polymerization.
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Montserrat Trilla et al.
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prepared as summarized in Scheme 1. Zinc reduc-
tion[18] of the oxime 4 derived from commercial di-(2-
pyridyl)methanone (3) gave di-(2-pyridyl)methyl-
amine (5) which was immediately reacted overnight
under stirring with freshly distilled 3-(triethoxysilyl)-
propyl isocyanate in anhydrous dichloromethane at
room temperature. The resulting silylated urea 6 was
treated overnight with PdCl2(CH3CN)2 in anhydrous
E
toluene at 80–908C to furnish complex 2a. Palladium-
containing hybrid silica materials 7a–c were obtained
by standard co-gelification of monomer 2a with differ-
ent amounts of tetraethyl orthosilicate (TEOS) (1:10,
1:20, 1:40) in dimethylformamide, using the stoichio-
Figure 1. Palladium dichloride complexes of di-2-pyridyl-
amine and di-(2-pyridyl)methylamine ligands.
Nµjera[15] has described related palladium(II) com- metric amount of water and ammonium fluoride as
plexes 2 (Figure 1) as efficient catalysts for Heck, catalyst. A standard nucleophilic fluoride catalysis
Suzuki and Sonogashira reactions in organic and was considered appropriate for the sol-gel co-gelifica-
aqueous solvents under homogeneous conditions. The tion of TEOS with the complex 2a, it has been widely
same group has covalently anchored this type of com- used by many authors and avoids the acidic or basic
plexes 2 to a styrene-maleic anhydride copolymer medium involved in alternative acid or basic catalysis.
providing a recyclable catalyst for those reactions.[16] The materials were characterized by solid-state
Prompted by the publication of this report we have 29Si NMR and 13C NMR, surface area BET measure-
presented our preliminary results on the preparation ments, IR and elemental analysis, the amount of pal-
of hybrid silica materials from the silylated monomer ladium being determined by inductively coupled
2a (Figure 1) and their activity and recyclability in plasma (ICP) (Table 1). From analytical data we ob-
Suzuki cross-couplings.[17] We describe here the full tained a molar ratio Pd/N of about 1/4 for complex 2a
details of our work and its extension to Heck and So- as expected. As for the materials 7a–c the experimen-
nogashira reactions.
tal molar ratios Pd/N were found to be about 1/7, par-
tial decomplexation has occurred in the formation of
materials by the sol-gel process. Large amounts of
TEOS were used (10, 20 and 40 molar equivalents
with respect to 2a) in order to favour solid formation
with high BET surface areas, because heterogeneous
catalysts with higher specific surface areas are usually
Results and Discussion
Monomer Synthesis and Catalysts Preparation
The monosilylated palladium(II) complex 2a and the more efficient. Similar surface areas ranging from 165
hybrid silica catalytic materials derived thereof were to 176 m2 gÀ1 were obtained for all three materials ac-
Scheme 1. Preparation of hybrid silica materials 7a–c.
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Hybrid Organic-Inorganic Materials from Di-(2-pyridyl)methylamine-Palladium Dichloride
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Table 1. Some analytical and textural data of hybrid materials 7a–c.
´
7
29Si CP MAS NMR
SBET [m2 gÀ1]
Pore Diameter[a] [Š]
Pore Volume[b] [cm3 gÀ1]
% Pd
mmol Pd/g
T3
Q3
Q4
7a
7b
7c
À65.4
À65.7
À64.6
À101.9
À102.2
À100.8
À109.4
À110.6
À109.4
165
171
176
61
99
97
0.274
0.454
0.464
6.05
3.88
2.63
0.569
0.365
0.247
[a]
[b]
Adsorption average pore diameter.
Adsorption cumulative volume of pores.
cordingly to the BET adsorption-desorption measure-
ments. The presence of the organic ligand in the
hybrid materials was ensured by the solid-state NMR
spectra (29Si and 13C). The 29Si spectra of 7a–c show
two groups of chemical shifts: T units at around À55
to À75 ppm, resulting from the hydrolysis-condensa-
tion of 2a, and Q units ranging from À100 to
À120 ppm, formed from TEOS as exemplified by the
29Si solid-state NMR of 7a (Figure 2, a). The T:Q in-
tensities diminish from 7a to 7c with decreasing
amount of 2a to TEOS (not shown). Only the solid-
state 13C NMR of 7a was performed, the organics in
7b and 7c being of too little intensity in the corre-
sponding hybrids to be measured in a reasonable
time. The spectrum of 7a exhibits an absorption at
À
8.7 ppm (CH2 Si) which confirms the covalently
bonded ligand to silica. Other signals attributable to
the chemical shifts of the organic part of 7 appear at
À
16.6 (CH3 from residual ethoxy groups), 23.0 (CH2
À
À
CH2 Si), 42.6 (CH2 N), 58.1 (CH2 from residual
À
ethoxy groups), 74.3 (CH N), 126.8, 141.7, 154.5 (3 C
from pyridine rings) and 158 (C=O) ppm (Figure 2,
b).
Assay of Supported Catalysts 7a–c in Suzuki, Heck
and Sonogashira Reactions
The activity and recyclability of catalysts 7a–c was as-
sayed in the Suzuki cross-coupling of phenylboronic
acid (8) with p-bromoacetophenone (9a), and with
the aryl chlorides m-chlorobenzonitrile (11a) and
chlorobenzene (11b) (Scheme 2, Table 2 and Table 3).
Three different sets of conditions were tested for aryl
bromide 9a with material 7b (Table 2): A) KOH,
MeOH/H2O (3:1), 608C; B) K2CO3, toluene, 1108C;
C) K2CO3, DMF/H2O (95:5), 1108C. The faster reac- Figure 2. Solid state CP-MAS 29Si (a) and 13C NMR (b)
spectra for 7a.
tion (0.75 h for full conversion) and the best recycling
in up to five consecutive runs was achieved with con-
ditions C (96% isolated yield in the fifth run). Thus,
they were also adopted for the other two catalytic ma- No significant differences were found within the ma-
terials 7a and 7c. Ten consecutive cycles with the terials with respect to their recyclability, which was
same batch of catalyst were performed for every cata- excellent in all cases, but the reaction time required
lyst, maintaining the same reaction time in every run. to achieve complete conversion of the aryl bromide
The isolated yields of 4-phenylacetophenone (10) for was longer with 7c containing a lower percentage of
every catalytic material are summarized in Table 2. palladium. This Suzuki cross-coupling was also as-
Adv. Synth. Catal. 2008, 350, 577 – 590
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Scheme 2. Suzuki cross-couplings tested with catalysts 7a–c.
Table 2. Suzuki couplings between 8 and 9a with catalysts 7a–c giving rise to 10 (Scheme 2).
Run
Conditions A[a] 7b
Conditions B[b] 7b
Conditions C[c] 7a
Conditions C[c] 7b
Conditions C[c] 7c
t [h] Conversion [%][d] t [h] Conversion [%][d] t [h] Yield [%][e] t [h] Yield [%][e] t [h] Yield [%][e]
1
2
3
4
5
6
7
8
9
10
0.75 100
0.75 78
0.75 74
0.75 73
3
3
3
3
98
94
89
91
0.75 100
0.75 100
0.75 96
0.75 97
0.75 96
0.75 95
0.75 97
0.75 98
0.75 97
0.75 94
0.75 100
0.75 100
0.75 99
0.75 96
0.75 96
0.75 94
0.75 96
0.75 96
0.75 97
0.75 96
1
1
1
1
1
1
1
1
1
1
100
99
98
98
97
98
96
97
95
95
[a]
0.2% molar of Pd, [ArX]=0.5M, PhB(OH)2 (1.5 equiv.), KOH (2 equiv.), MeOH/H2O (3:1), 608C.
0.2% molar of Pd, [ArX]=0.5M, PhB(OH)2 (1.5 equiv.), K2CO3 (2 equiv.), toluene, 1108C.
0.2% molar of Pd, [ArX]=0.5M, PhB(OH)2 (1.5 equiv.), K2CO3 (2 equiv.), DMF/H2O (95:5), 1108C.
GLC conversions (undecane as internal standard).
[b]
[c]
[d]
[e]
Isolated yield.
Table 3. Suzuki couplings between 8 and 11a with catalyst
7b giving rise to 12a (Scheme 2).
thylamine complex anchored to organic polymer, in-
creasing reaction times being described for successive
cycles. In our case, the use of a lower amount of
water, dimethylformamide instead of methanol and
potassium carbonate as base instead of KOH im-
proved the recyclability (conditions C are better than
conditions A).
It must be mentioned that the initial pale yellow
solids 7a–c turned grey after the first run and dark-
ened progressively to black after several runs which is
possibly due to the formation of metallic particles. In
order to confirm this we studied the recycled materi-
als through electron microscopic techniques. Indeed
high-resolution transmission electron microscopy
Run
Conditions C[a] 7b
t [h] Conversion [%][b] t [h] Conversion [%][b]
1
2
3
4
5
7
7
7
7
7
61
44
34
31
25
24
24
24
24
24
82
59
38
34
26
[a]
0.2% molar of Pd, [ArX]=0.5M, PhB(OH)2 (1.5 equiv.),
K2CO3 (2 equiv.), DMF/H2O (95:5), 1108C.
GLC conversions (undecane as internal standard).
[b]
sayed under the same conditions C with the material (HR-TEM) showed the formation of metal nanoparti-
7bSi, obtained by refluxing 7b with excess of bis(tri- cles in the materials (diameter around 5 nm). Elec-
methylsilyl)amine for capping surface silanol groups, tron diffraction (ED) of the sample exhibited the
but the reaction was slower, four hours being required characteristic pattern of face-centered cube (fcc) pal-
to afford a 97% isolated yield of 10. Nµjera[16] has ladium(0). Both the inorganic matrix and the organic
used water or methanol-water as solvent systems in ligand of the hybrids can have a contribution to the
their recycling experiments with the di-(2-pyridyl)me- nanoparticle stabilization.[19] To ensure that the nano-
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Hybrid Organic-Inorganic Materials from Di-(2-pyridyl)methylamine-Palladium Dichloride
FULL PAPERS
particles were inside the silica material and not only
The amounts of Pd determined by ICP-MS in the
adsorbed on the external surface, a sample for TEM product 10 isolated from the first cycle performed
measurement was also prepared by using ultramicro- with catalyst 7a under conditions C and in the solid
tomy techniques instead of only depositing a drop of mixture obtained in this cycle by evaporation of the
a suspension of the solid onto the copper grid. In filtrate were found to be 12 and 80 ppm, respectively.
Figure 3 we show an example of HR-TEM micro- Some authors have pointed out[20] that released Pd
graphs of one of the samples (material 7c after the under reaction conditions acts as the true catalyst in
fourth cycle, conditions C of Table 2), a TEM obser- immobilized palladium systems and redeposition of
vation using ultramicrotomy techniques and the size the metal after completion of the reaction is claimed.
distribution of the particles. The nanoparticles were When the catalyst 7b was filtered off from the hot re-
not observed by TEM in the materials before the cat- action mixture under conditions C after 15 min (47%
alysis, but darkening of the recovered catalytic mate- GLC conversion of 9a) and the remaining filtrate was
rials in successive runs took place under any condi- made to react at the same temperature, the conver-
tions used for the Suzuki couplings. Palladium nano- sion raised to 80% (GLC) after 6 h. Thus, a homoge-
particles observed by TEM in supported bipyridyl neous pathway due to metal release in the reaction
complexes have also been described by Nµjera.[16]
conditions is, in part, responsible for the catalysis, but
as the reaction is much slower, the heterogeneous
pathway plays a significant role.
Material 7b was also tested in the more challenging
Suzuki coupling with aryl chlorides (Scheme 2). Treat-
ment of phenylboronic acid (8) with m-chlorobenzo-
nitrile (11a) under conditions C (Table 3) afforded 3-
cyanobiphenyl (12a)[21] but a complete conversion
could not be achieved after one day. Conversions of
11a were determined by GLC at two reaction times
(7 and 24 h) for each of the five consecutive runs. In
this case, a significant decrease of conversion upon re-
cycling was observed, prolonged reaction times being
not useful. When conditions C were adopted with cat-
alyst 7a for the reaction of phenylboronic acid (8)
with chlorobenzene (11b) to yield 12b, a modest con-
version of 36% (GLC) was obtained after 6 h. Heat-
ing at higher temperature (1508C) with the same base
and solvent system did not improve very much the
result (42% conversion after 6 h). However, our re-
sults are even better than those previously report-
ed,[16] where the recycling was performed with an acti-
vated aryl chloride, p-chloroacetophenone, at higher
temperature (1308C) and higher amount of Pd (4.4%)
in H2O and K2CO3 as base, with decreasing activities
of the recovered catalyst, as only modest yields were
obtained from the second run even on increasing the
reaction times from 3 to 14 h.
Next we performed the Heck reaction between p-
bromoacetophenone (9a) and n-butyl acrylate (13) to
give 4-acetyl-trans-cinnamic acid butyl ester (14)
(Scheme 3). Three different bases (tributylamine,
sodium acetate and potassium carbonate) were tested
Figure 3. a) and b) HR-TEM micrographs of Pd nanoparti-
cles formed in the Suzuki reaction; c) TEM observation by
using ultramicrotomy techniques; d) particle size distribu-
tion (104 particles; mean particle size: 5.1Æ0.9 nm).
Scheme 3. Heck reactions tested with catalysts 7a–c.
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Table 4. Heck reactions between 9a and 13 with catalysts 7a–c giving rise to 14 (Scheme 3).
Run
Conditions A[a] 7b
Conversion [%][d]
Conditions B[b] 7b
Conversion [%][e]
Conditions C[c] 7a
t [h]
t [h]
t [h]
Conversion [%][e]
1
2
3
4
5
1
1
1
1
100
49
48
47
50 (95)
1
1
1
1
1
100
16
12
8
1
1
1
1
1
100
16
10
5
1 (7)
0
0
[a]
[b]
[c]
[d]
0.2% molar of Pd, [ArX]=0.5M, n-butyl acrylate (1.5 equiv.), NBu3 ( 1.5 equiv.), DMF, 1508C.
0.2% molar of Pd, [ArX]=0.5M, n-butyl acrylate (1.5 equiv.), NaOAc (1.5 equiv.), DMF, 1508C.
0.2% molar of Pd, [ArX]=0.5M, n-butyl acrylate (1.5 equiv.), K2CO3 (1.5 equiv.), DMF, 1508C.
GLC conversions (undecane as internal standard).
[e] 1H NMR conversions.
in dimethylformamide at 1508C (conditions A, B and
C in Table 4). In all cases a fast reaction took place
on the first cycle (complete conversion of 9a after one
hour), but very significant differences were observed
on subsequent runs with the same batch of material.
When the organic base tributylamine was used, the
conversion is maintained around 50% in cycles 2 to 5
for the same reaction time (1 h). Thus, it seems that
another catalytic species is formed after the first
cycle, which would react slower while maintaining the
recyclability properties. Upon prolonged reactions
times (7 h), an almost complete conversion is ach-
ieved on the fifth cycle (95%). On the contrary, the
recovered material after the first cycle under condi-
tions B and C exhibits a poor recyclability, a fast de-
crease in conversion being obtained from runs 2 to 5.
We made another important observation that can ex-
plain these differences on the catalyst behaviour. The
solid recovered under conditions A was grey-black
and contained palladium nanoparticles (15.1Æ
2.6 nm), whereas the material recovered under condi-
tions B and C maintained the pale yellow initial
colour and nanoparticles were not observed. In
Figure 4 we show an example of HR-TEM micro-
graphs of one of the samples (material 7b after the
first cycle, conditions A of Table 4), the EDimage ( d-
spacings=0.226, 0.197, 0.139, 0.119 nm) and the size
Figure 4. a) and b) HR-TEM micrographs of Pd nanoparti-
cles formed in the Heck reaction (conditions A of Table 4);
c) EDimage; d) particle size distribution (158 particles;
mean particle size: 15.1Æ2.6 nm).
distribution of the particles. From the HR-TEM mi- By filtration of the hot mixture after 20 min of reac-
crographs we could clearly see that the nanoparticles tion (26% GLC conversion) and heating again the fil-
were not well spread inside the silica matrix but ag- trate at 1508C for 15 h a 100% conversion of 9a was
glomerated on the external surface of the material. achieved, showing that an homogeneous pathway is,
The stabilizer must be in this case the tributylammo- in part, responsible of the reaction. The correspond-
nium bromide formed in the Heck reaction. Indeed, ing aryl chloride 9b failed to react with 13 under con-
the stabilization of palladium nanoparticles by ammo- ditions A.
nium salts is well documented in the literature.[22] As
Nµjera[16] used water as solvent at 1008C in the
this salt is not formed when sodium acetate and po- presence of diisopropylamine as base and added
tassium carbonate are used as bases, this can explain TBAB for Heck recycling with the organic polymeric
the unsuccessful recycling found for conditions B and version of the palladium catalyst and increasing reac-
C. Probably most of the palladium is not retained tion times were required in successive cycles for full
onto the silica material after the first cycle. A test for conversion (6 h in first cycle, 22 h from the second
Pd leaching was also performed under conditions A. cycle). With our silica-anchored palladium complex
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Hybrid Organic-Inorganic Materials from Di-(2-pyridyl)methylamine-Palladium Dichloride
FULL PAPERS
Table 5. Sonogashira reactions between 15 and the aryl hal-
ides 9a and 17 with catalyst 7b giving rise to 16 and 18
(Scheme 4).
the use of organic solvent at higher temperature in-
stead of water was advantageous, but in our hands, an
organic base was also the best choice for good recy-
clability and the activity of the catalyst decreased also
from the first to the second cycle and it was main-
tained in successive runs.
Run
Conditions A[a] 17 to 18
Conditions A[a] 9a to 16
t [h] Conversion [%][b] t [h] Conversion [%][b]
1
2
3
4
5
0.5
0.5
0.5
0.5
0.5
100
68
50
48
43
1.5
1.5
1.5
1.5
1.5
100
96
92
92
85
The hybrid material 7b was assayed as catalyst in
the Sonogashira reaction between phenylacetylene
(15) and aryl halides 9a, b and 17 to afford disubsti-
tuted acetylenes 16 and 18 (Scheme 4). After a
screening of some bases and solvents (pyrrolidine,
NMP, 1108C, 4 h, 50% conversion; Bu4NOAc, NMP,
1108C, 1 h, 93% conversion on the first run and 86%
on the second run; K2CO3, DMF/H2O 95:5, 1108C,
5 h, 74%; Bu4NOAc, EtOH, 1008C, 6 h, 25%; K2CO3,
Bu4NBr, DMF, 1108C, 5 h, 77%; Bu4NOAc, CH3CN,
[a]
0.2% molar of Pd, [ArX]=0.5M, 15 (1.5 equiv.),
Bu4NOAc (1.5 equiv.), DMF, 1108C.
GLC conversions (undecane as internal standard).
[b]
1008C, 1.5 h, 89%; NaOAc, DMF, 1108C, 1 h, 70%; contain nanoparticles and it did not darken on succes-
KF, DMF, 1108C, 3 h, 70%) on the reaction with the sive cycles. In this case, contrary to what we have pre-
bromide 9a, the conditions A of Table 5 were adopted viously observed in Suzuki and Heck reactions, the
(tetrabutylammonium acetate as base, dimethylform- formation of nanoparticles is not required for good
amide, 1108C). Under these conditions p-bromoaceto- recycling. As a consequence, the real catalytic species
phenone (9a) and p-iodoanisole (17) underwent a fast formed from the bipyridyl-type palladium complex
reaction to give full conversion to 1-(4-acetylphenyl)- and which are responsible for the catalysis should be
2-phenylacetylene (16) and 1-(4-methoxyphenyl)-2- different in every reaction studied. The infrared spec-
phenylacetylene (18) in 1.5 and 0.5 h, respectively. tra on the region of 30–700 cmÀ1 of the silylated mo-
However, the recycling was best accomplished with nomer 2a, the material 7a before the catalysis and the
the bromide 9a as shown in Table 5. The iodide 17 same material after Sonogashira and Suzuki reactions
seemed to have some deleterious effect on the activity are summarized in Figure 5. The infrared vibrations
[23]
À
of the recovered catalyst and a significant decrease of for the Pd Cl bond appear
in the range 350–
conversion was observed in successive runs. Nonethe- 330 cmÀ1 and the less intense vibrations for the Pd N
less, the p-chloroacetophenone (9b) did not react with bond are in the range 530–430 cmÀ1. The absorptions
15 in an appreciable extent under prolonged heating at ca. 336 cmÀ1 of complex 2a and at ca. 338 cmÀ1 of
À
in analogous conditions. The Nµjera groupꢁs[16] choice material 7a should be attributed to vibrations of Pd
À
for the Sonogashira coupling with the supported cata- Cl bond (Figure 5, a). The IR spectrum of recovered
lyst was again refluxing water, with an organic base material 7a after Sonogashira reaction is more similar
such as pyrrolidine and the addition of TBAB. In our to that of the original 7a before catalysis (Figure 5, b)
hands, an organic solvent such as DMF was superior than to the IR spectrum of recovered 7a after Suzuki
for the silica anchored complex and our results are reaction (Figure 5, c), in accordance with the fact that
comparable with theirs, if we take into account that palladium(0) nanoparticles are formed in the Suzuki
they described increasing reaction times in successive process but not in the Sonogashira reaction.
cycles to maintain the conversion.
A test for Pd leaching was also performed for the
It is worthwhile to notice that the recovered cata- Sonogashira reaction between 9a and 15 (conditions
lytic material 7b of the Sonogashira reactions did not A of Table 5). By filtration of the hot mixture after
Scheme 4. Sonogashira reactions tested with catalysts 7a–c.
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Figure 5. a) IR spectra (30–700 cmÀ1) of monomeric complex 2a (upper trace) and polymeric complex 7a (lower trace). b)
IR spectra (30–700 cmÀ1) of recovered material 7a after Sonogashira reaction (upper trace) and 7a before catalysis (lower
trace). c) IR spectra (30–700 cmÀ1) of recovered material 7a after Suzuki reaction (upper trace) and 7a before catalysis
(lower trace).
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Hybrid Organic-Inorganic Materials from Di-(2-pyridyl)methylamine-Palladium Dichloride
FULL PAPERS
20 min of reaction (49% GLC conversion) and heat- rities by GC: 100% for compound 10, 97% for com-
ing again the filtrate at 1108C a 95% GC conversion pound 14, 97% for compound 16, 96% for compound
of 9a was obtained after 6 h, showing that a homoge- 18 and 94% for compound 20). The analytical or spec-
neous pathway is, in part, responsible of the reaction. troscopic data were coincident with that reported in
Some soluble catalytic palladium species should have the literature (see supporting information for NMR
been formed, but as the reaction was slower, a hetero- spectra of 10, 14, 16, 18 and 20).
geneous pathway should also participate in the cata-
lytic process.
Some reports are available in the recent literature
about the use of silica anchored palladium(II) or
Finally, a two-step tandem Suzuki–Heck process Pd(0) complexes in Suzuki,[8,17,24] Heck[24b,f,k,i,o,r,s,25] and
was also undertaken with catalyst 7b on p-dibromo- Sonogashira[25w,26] coupling reactions. Many of these
benzene (19) by sequential treatment with phenylbor- works deal with the use of aryl iodides as substrates
onic acid (8) and n-butyl acrylate (13) in dimethylform- and do not report the recycling in Sonogashira reac-
amide at 1408C in the presence of potassium carbon- tions with aryl bromides. Wang[26c] had described the
ate as base (Scheme 5). The 4-phenyl-trans-cinnamic Sonogashira coupling of terminal alkynes with aryl io-
acid n-butyl ester (20) was obtained in a clean and ef- dides and bromides in the presence of a recoverable
ficient one-pot process in 97% isolated yield.
3-(2-aminoethylamino)propyl-functionalized silica-gel
The products resulting from the catalytic processes immobilized palladium(II) catalyst. They claim a very
were checked by GC and characterized by NMR (pu- efficient recycling of the silica-supported palladium,
Scheme 5. Tandem Suzuki–Heck coupling process with catalyst 7b.
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but the text is general and ambiguous and it is not palladium. Formation of fcc Pd(0) nanoparticles
clear if it refers to aryl iodides or also to aryl bro- during the Suzuki and Heck reactions has been shown
mides. Efficient recovery and reuse with aryl chlorides by HR-TEM and ED. In the Sonogashira coupling
in Suzuki coupling has only been achieved in few the formation of nanoparticles was not observed.
cases[24d,e,l] for oxime palladacycles and N-heterocyclic
carbenes anchored to the silica matrix. In the case of
Heck reactions, although some examples involving Experimental Section
aryl iodides and bromides have been found, only few
of them report the recycling with the more challeng- General Remarks
ing aryl bromides.[24f,s,25e,j,m,r,t] Even if phosphane li-
When required, experiments were carried out with standard
gands are more prone to oxidation, there are some
high vacuum and Schlenk techniques. Solvents were dried
examples of heterogeneous phosphane-containing cat-
alysts. Thus, silica sol-gel entrapped dichlorobis(tri-
phenylphosphane)palladium worked out[27] as an effi-
cient recyclable catalyst in Heck reactions[27a] and
and distilled just before use. Ammonium fluoride was pur-
chased from Aldrich, 3-(triethoxysilyl)propyl isocyanate was
purchased from Lancaster, tetraethyl orthosilicate, was pur-
chased from Acros. IR data were obtained in the following
spectrophotometers: Bruker Tensor 27 with ATR Golden
Gate and Perkin–Elmer (System 2000 FT-IR). The CP-MAS
29Si solid state NMR spectra were recorded on a Bruker FT-
AM 400. The repetition time was 5 seconds with contact
times of 5 milliseconds. Surface areas were determined by
the Brunauer-Emmett-Teller (BET) method on a Micromer-
itics Tristar 3000 analyzer, and the average pore diameter
was calculated by the BJH method. Elemental analysis have
been performed at the Serveis Científico-T›cnics of the Uni-
versitat de Barcelona. The content of palladium was deter-
mined at the Serveis Científico-T›cnics of the Universitat de
Barcelona by inductively coupled plasma (ICP). Transmis-
sion electron microscopy (TEM) observations by using ul-
tramicrotomy techniques were carried out in Montpellier
with a JEOL 1200 EXII (100 kV). High resolution transmis-
sion electron microscopy (HR-TEM) observations were car-
ried out at “Servei de Microscòpia de la UAB” with a
JEOL JEM 2010 (200 kV).
Suzuki cross-couplings[27b]
. However, this system
failed with aryl chlorides in the Suzuki coupling and
low conversions were attained with aryl bromides in
the Heck reaction. Our heterogeneous catalysts 7a–c
are competitive compared with the other silica-anch-
ored systems in terms of performance and reusability,
giving faster reactions, and only oxime palladacy-
cles[24d,e] and N-heterocyclic carbenes[24l] remain supe-
rior.
Conclusions
In summary, we have described the synthesis of
hybrid silica materials with covalently attached di-(2-
pyridyl)methylamine-palladium dichloride complex
by sol-gel methodology and their use as efficient and
recoverable catalysts for carbon-carbon bond forma-
tion reactions. They were very active in the Suzuki
cross-coupling of phenylboronic acid with p-bromoa-
cetophenone, being efficiently reused for up to ten
cycles with no decrease of activity. The reaction has
also been performed with m-chlorobenzonitrile, al-
though the activity and recyclability were lower, five
consecutive runs with decreasing activities being
Oxime 4[18,28] and amine 5[18] were prepared as previously
described.[18]
Synthesis of N-(Di-2-pyridylmethyl)-N’-(3-
(triethoxysilyl)propyl)urea (6)
Freshly distilled (3-triethoxysilyl)propyl isocyanate (565 mL,
0.559 g, 2.26 mmol) was added at room temperature under
an argon atmosphere to a stirred solution of freshly pre-
pared amine 5 (0.419 g, 2.26 mmol) in anhydrous dichloro-
methane (2 mL). The reaction mixture was stirred at room
temperature overnight, the solvent was evaporated and the
white solid residue was thoroughly washed with anhydrous
pentane and dried under vacuum to afford pure 6;[17] yield:
achieved. The Heck reaction between p-bromoaceto-
phenone and n-butyl acrylate was very effective with
these supported catalysts. The catalytic system was re-
cyclable (five runs) when tributylamine was used as
base. Suitable conditions were found for very fast
copper- and phosphine-free Sonogashira couplings be-
tween phenylacetylene and aryl bromides and iodides.
The recyclability of the catalyst (five runs) was much
better for p-bromoacetophenone than for p-iodoani-
sole. A clean one-pot two-step Suzuki–Heck process
between p-dibromobenzene, phenylboronic acid and
n-butyl acrylate has been successfully carried out. Hot
filtration tests performed with all these coupling reac-
tions showed that both homogeneous and heterogene-
ous pathways participate in the catalysis. Nonetheless,
our systems show excellent performance and good re-
usability, giving fast reactions with low amounts of
1
0.829 g (85%); mp 113–1148C; H NMR (CDCl3, 250 MHz):
d=0.52–0.59 (m, 2H), 1.18 (t, J=7.0 Hz, 9H), 1.54 (m, 2H),
3.14 (m, 2H), 3.76 (q, J=7.0 Hz, 6H), 5.11 (br t, J=5.6 Hz,
1H), 6.07 (d, J=6.6 Hz, 1H), 6.91 (d, J=6.6 Hz, 1H), 7.10
(ddd, J=7.5, 4.9 and 1.1 Hz, 2H), 7.40 (d, J=7.9 Hz, 2H),
7.58 (td, J=7.7 and 1.8 Hz, 2H), 8.46 (d, J=4.9 Hz, 2H);
13C NMR (CDCl3), 62.5 MHz): d=7.9, 18.6, 23.8, 43.3, 58.6,
60.4, 122.5, 122.6, 137.1, 149.2, 157.9, 160.2; IR (ATR): n=
3353, 3281, 2973, 2875, 1626, 1561, 1076, 950, 758 cmÀ1; anal.
calcd. (%) for C21H32N4SiO4: C 58.31, H 7.46, N 12.95, Si
6.49; found: C 57.43, H 8.52, N 12.93, Si 6.43.
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FULL PAPERS
Synthesis of the Palladium(II) Complex 2a
Synthesis of 14 by Heck Reaction between 9a and 13
with Catalyst 7b under Conditions A of Table 4;
Typical Procedure
A stirred mixture of 6 (0.199 g, 0.46 mmol), PdCl2(CH3CN)2
G
(0.119 g, 0.46 mmol) and anhydrous toluene (5 mL) was
heated at 80–908C under argon overnight. The solvent was
evaporated affording 2a[17] as a pale yellow solid; yield:
Tributylamine (1075 mL, 0.776 gmLÀ1, 4.5 mmol) was added
to a stirred mixture of 7b (0.0164 g, 0.006 mmols Pd), 4-bro-
moacetophenone 9a (0.6093 g, 3 mmol) and n-butyl acrylate
13 (655 mL, 0.890 gmLÀ1, 4.5 mmol) in DMF (6 mL) and it
was heated at 1508C for 60 min (GLC monitoring). Insolu-
ble 7b was filtered, washed with water, ethanol and diethyl
ether, it was dried under vacuum (2 mm Hg) and reused in
the next run (0.0160 g of recovered catalyst). The product
was extracted from the filtrate with ethyl acetate, and the
organic phase was washed with water. The organic layer was
dried with anhydrous Na2SO4 and the solvent was evaporat-
ed to give pure (97% by GC) 4-acetyl-trans-cinnamic acid n-
1
0.230 g (82%); H NMR (CD3SOCD3, 250 MHz, 329 K): d=
0.52–0.70 (m, 2H), 1.17 (t, J=7.0 Hz, 9H), 1.43–1.67 (m,
2H), 3.12–3.24 (m, 2H), 3.77 (q, J=7.0 Hz, 6H), 6.30–6.52
(m, 1H), 7.09–7.28 (m, 1H), 7.55 (t, J=6.5 Hz, 2H), 7.66–
7.96 (m, 3H), 8.03–8.24 (m, 2H), 8.83–9.00 (m, 2H); IR
(ATR): n=3331, 3109, 2973, 2882, 1630, 1563, 1471, 1070,
953, 764 cmÀ1; anal. calcd. (%) for C21H32N4SiCl2O4Pd: C
41.35, H 5.29, N 9.19, Si 4.60, Pd 17.45; found: C 41.25, H
5.43, N 9.10, Si 4.46, Pd (ICP) 16.52.
1
butyl ester 14[30] as an oil; yield: 0.736 g (100%). H NMR
(CDCl3, 250 MHz): d=0.96 (t, 3H, J=7.3 Hz), 1.36–1.51
(m, 2H), 1.63–1.74 (m, 2H), 2.61 (s, 3H), 4.22 (t, 2H, J=
6.6 Hz), 6.52 (d, 1H, J=16.0 Hz), 7.60 (d, 2H, J=8.3 Hz),
7.68 (d, 1H, J=16.0 Hz), 7.96 (d, 2H, J=8.3 Hz); 13C NMR
(CDCl3, 62.5 MHz): d=13.9, 19.4, 26.8, 30.9, 64.8, 121.0,
128.3, 129.0, 138.2, 139.0, 143.1, 166.7, 197.4.
Synthesis of Materials 7a, 7b and 7c; Typical
Procedure
A solution of ammonium fluoride (168 mL of a 1M solution,
0.168 mmol of fluoride, 9.33 mmol of water), anhydrous
DMF (6.8 mL) and distilled and deionized water (1035 mL,
57.5 mmol) were added to
a solution of 2a (0.252 g,
0.413 mmol) and TEOS (3.489 g, 16.4 mmol) in anhydrous
DMF (10 mL). The mixture was stirred manually for a
minute to get an homogeneous solution and was left at
room temperature without stirring. Gelation occurred after
2 h and the gel was allowed to age for 3 days, after which it
was powdered and washed successively twice with water and
3 times with ethanol. The solid was dried under vacuum
overnight (2 mm Hg, 608C), affording 7c as a yellow
powder; yield: 1.274 g; IR (KBr): n=3447, 1655, 1564, 1079,
959, 799, 459 cmÀ1; anal. (%) found: C 8.38, H 1.24, N 1.86,
Si 35.00, Pd (ICP) 2.63.
Synthesis of 16 by Sonogashira Reaction between 9a
and 15 with Catalyst 7b under Conditions A of Table
5
Phenylacetylene 15 (505 mL, 0.930 gmLÀ1, 4.5 mmol) was
added to a stirred mixture of 7b (0.0164 g, 0.006 mmol Pd),
4-bromoacetophenone 9a (0.6093 g, 3 mmol) and Bu4NOAc
(1.398 g, 4.5 mmol) in DMF (6 mL) and heated at 1108C for
90 min (GLC monitoring). Insoluble 7b was filtered, washed
with water, ethanol and diethyl ether, it was dried under
vacuum (2 mm Hg) and reused in the next run (0.0156 g of
recovered catalyst). The product was extracted from the fil-
trate with ethyl acetate, and the organic phase was washed
with water. The organic layer was dried with anhydrous
Na2SO4 and the solvent was evaporated to give pure (97%
by GC) 1-(4-acetylphenyl)-2-phenylacetylene 16;[31] yield:
Materials 7a and b were obtained in a similar manner
except for the molar ratio 2a:TEOS. Material 7a: Anal. (%)
found: C 11.77, H 1.90, N 4.43, Si 26.82, Pd(ICP) 6.05. Mate-
G
rial 7b: Anal. (%) found: C 10.32, H 1.24, N 2.66, Si 29.51,
Pd (ICP) 3.88.
1
0.6463 g (98%); mp 94–968C (lit.[31b] mp 94–968C); H NMR
(CDCl3, 250 MHz): d=2.61 (s, 3H), 7.34–7.38 (m, 3H),
7.53–7.56 (m, 2H), 7.60 (d, 2H, J=8.6 Hz), 7.94 (d, 2H, J=
8.6 Hz); 13C NMR (CDCl3, 62.5 MHz): d=26.9, 88.9, 93.0,
123.0, 128.5, 128.6, 128.7, 129.1, 131.99, 132.04, 136.5, 197.6.
Synthesis of 10 by Suzuki Reaction between 8 and 9a
with Catalyst 7b under Conditions C of Table 2;
Typical Procedure
Potassium carbonate (1.935 g, 14 mmol) was added to a
stirred mixture of 7b (0.0384 g, 0.014 mmol of Pd), 4-bro-
moacetophenone 9a (1.422 g, 7 mmol), and phenylboronic
acid 8 (1.306 g, 10.5 mmol) in DMF/H2O (95:5) (14 mL) and
heated at 1108C for 45 min (GLC monitoring). Product 10
precipitated by addition of water to the crude mixture. The
filtered solid was washed with water and then it was taken
in ethyl acetate. Insoluble 7b was filtered. The filtrate was
dried with anhydrous sodium sulphate and the solvent was
evaporated to give pure 10 (100% by GC); yield: 1.374 g
(100%); mp 120–1218C (lit.[29] mp 120.58C); 1H NMR
(CDCl3, 250 MHz): d=2.65 (s, 3H), 7.40–7.51 (m, 3H), 7.63
(d, 2H, J=6.7 Hz), 7.69 (d, 2H, J=8.4 Hz), 8.04 (d, 2H, J=
8.4 Hz); IR (ATR): n=3067, 2994, 1674, 1594, 1357, 1257,
955, 835, 761 cmÀ1. The catalyst 7b was washed successively
with water, ethanol and diethyl ether, it was dried under
vacuum (2 mm Hg) and reused in the next run.
Synthesis of 18 by Sonogashira Reaction between 17
and 15 with Catalyst 7b under Conditions A of Table
5
Phenylacetylene 15 (505 mL, 0.930 gmLÀ1, 4.5 mmol) was
added to a stirred mixture of 7b (0.0164 g, 0.006 mmols Pd),
4-iodoanisole 17 (0.7092 g, 3 mmols) and Bu4NOAc (1.398 g,
4.5 mmols) in DMF (6 mL) and it was heated at 1108C for
30 min (GLC monitoring). Insoluble 7b was filtered, washed
with water, ethanol and diethyl ether, it was dried under
vacuum (2 mm Hg) and reused in the next run (0.0149 g of
recovered catalyst). The product was extracted from the fil-
trate with ethyl acetate, and the organic phase was washed
with water. The organic layer was dried with anhydrous
Na2SO4 and the solvent was evaporated to give pure (96%
by GC) 1-(4-methoxyphenyl)-2-phenylacetylene 18;[15a]
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yield: 0.605 g (97%); mp 50–538C (lit.[15a] mp 51–538C);
1H NMR (CDCl3, 250 MHz): d=3.82 (s, 3H), 6.87 (d, 2H,
J=9 Hz), 7.32–7.35 (m, 3H), 7.45–7.52 (m, 4H); 13C NMR
(CDCl3, 62.5 MHz): d=55.6, 88.4, 89.7, 114.3, 115.7, 123.9,
128.2, 128.6, 131.8, 133.4, 159.9.
Angew. Chem. 1994, 106, 2473; Angew. Chem. Int. Ed.
Engl. 1994, 33, 2379; b) W. Cabri, I. Candiani, Acc.
Chem. Res. 1995, 28, 2; c) T. Jeffery, Adv. Metal-Organ-
ic. Chem. 1996, 5, 153; d) M. M. Beller, T. H. Riermei-
er, G. Stark, Trans. Met. For Org. Synth. 1998, 1, 208;
e) G. T. Crisp, Chem. Soc. Rev. 1998, 27, 427; f) I. P. Be-
letskaya, A. V. Cheprakov, Chem. Rev. 2000, 100, 3009;
g) A. Biffis, M. Zecca, M. Basato, J. Mol. Cat. A:
Chem. 2001, 173, 249; h) N. J. Whitcombe, K. K. Hii,
S. E. Gibson, Tetrahedron 2001, 57, 7449; i) J. G. de V-
ries, Can. J. Chem. 2001, 79, 1086; j) J. T. Link, Org.
React. 2002, 60, 157; k) A. B. Dounay, L. E. Overman,
Chem. Rev. 2003, 103, 2945; l) P. J. Guiry, D. Kiely, Cur-
rent Org. Chem. 2004, 8, 781; m) M. Prashad, Top. Or-
ganomet. Chem. 2004, 6, 181; n) N. Miyaura, Adv.
Synth. Catal. 2004, 346, 1522; o) M. Shibasaki, E. M.
Vogl, T. Ohshima, Adv. Synth. Catal. 2004, 346, 1533;
p) V. Farina, Adv. Synth. Catal. 2004, 346, 1553;
q) A. M. Trzeciak, J. J. Ziolkowski, Coord. Chem. Rev.
2005, 249, 2308; r) F. Alonso, I. P. Beletskaya, M. Yus,
Tetrahedron 2005, 61, 11771.
Synthesis of 20 by a TandemSuzuki–Heck Process
from p-Dibromobenzene (19)
A stirred mixture of 1,4-dibromobenzene 19 (0.9629 g,
4 mmol), phenylboronic acid 8 (0.4977 g, 4 mmol), K2CO3
(1.658 g, 12 mmol) and 7b (0.0141 g, 0.008 mmol Pd) in
DMF (8 mL) was heated at 1408C for one day (GLC moni-
toring). n-Butyl acrylate 13 (875 mL, 0.890 gmLÀ1, 6 mmol)
was added. After one more day of heating at the same tem-
perature, 7b was filtered off and washed with water, ethanol
and chloroform. The product was extracted from the filtrate
with ethyl acetate, and the organic phase was washed with
water. The organic layer was dried with anhydrous Na2SO4
and the solvent was evaporated to give 4-phenyl-trans-cin-
namic acid n-butyl ester 20;[30a] yield: 1.0845 g (97%) (94%
by GC); 1H NMR (CDCl3, 250 MHz): d=0.98 (t, 3H, J=
7.3 Hz), 1.38–1.53 (m, 2H), 1.65–1.76 (m, 2H), 4.23 (t, 2H,
J=6.6 Hz), 6.48 (d, 1H, J=16.0 Hz), 7.34–7.40 (m, 1H),
7.43–7.49 (m, 2H), 7.60–7.63 (m, 6H), 7.72 (d, 1H, J=
16.0 Hz); 13C NMR (CDCl3, 62.5 MHz): d=14.1, 19.5, 31.1,
64.8, 118.5, 127.3, 127.8, 128.2, 128.9, 129.2, 133.8, 140.5,
143.3, 144.4, 167.5.
[3] For some reviews dealing with the Sonogashira reaction
and its applications, see: a) K. Sonogashira, in: Hand-
bock of Organopalladium Chemistry for Organic Syn-
thesis, (Eds.: E. Negishi, A. De Meijere), Wiley-Inter-
science, New York, 2002, Vol 1, pp 493–529; b) K. So-
nogashira, J. Organomet. Chem. 2002, 653, 46; c) R. R.
Tykwinski, Angew. Chem. 2003, 115, 1604; Angew.
Chem. Int. Ed. 2003, 42, 1566; d) E. Negishi, L. Anasta-
sia, Chem. Rev. 2003, 103, 1979; e) R. Chinchilla, C.
Nµjera, Chem. Rev. 2007, 107, 874.
[4] a) Y. De Miguel, E. BrulØ, R. G. Margue, J. Chem.
Soc., Perkin Trans. 1 2001, 3085; b) B. Clapham, T. S.
Reger, K. J. Janda, Tetrahedron 2001, 57, 4637; c) C. A.
McNamara, M. J. Dixon, M. Bradley, Chem. Rev. 2002,
102, 3275; d) N. E. Leadbeater, M. Marco, Chem. Rev.
2002, 102, 3217.
[5] a) A. Adima, J. J. E. Moreau, M. Wong Chi Man, J.
Mater. Chem. 1997, 7, 2331; b) J. Y. Ying, C. P. Mehnert,
M. S. Wong, Angew. Chem. 1999, 111, 58; Angew.
Chem. Int. Ed. 1999, 38, 56; c) E. Lindner, T. Schneller,
F. Auer, H. A. Mayer, Angew. Chem. 1999, 111, 2288;
Angew. Chem. Int. Ed. 1999, 38, 2154; d) D. E. De Vos,
M. Dams, B. F. Sels, P. A. Jacobs, Chem. Rev. 2002, 102,
3615; e) A. P. Wight, M. E. Davis, Chem. Rev. 2002,
102, 3589; f) Z. Lu, E. Lindner, H. A. Mayer, Chem.
Rev. 2002, 102, 3543; g) G. Kickelbick, Angew. Chem.
2004, 116, 3164; Angew. Chem. Int. Ed. 2004, 43, 3102;
h) F. Hoffmann, M. Corneliu, J. Morell, M. Frçba,
Angew. Chem. 2006, 118, 3290; Angew. Chem. Int. Ed.
2006, 45, 3216; i) A. Corma, H. Garcia, Adv. Synth.
Catal. 2006, 348, 1391; j) L. Yin, J. Liebscher, Chem.
Rev. 2007, 107, 133.
Acknowledgements
Financial support from the MEC of Spain (Project
CTQ2006–04204/BQU), Consolider Ingenio 2010 (Project
CSD2007–00006), Generalitat de Catalunya (Project
SGR2005–00305) and Universitat Autònoma de Barcelona
(Project PNL2005–10), from the French Ministry of Research
and Technology, from the CNANO and from the CNRS is
gratefully acknowledged. We thank Y. Guari for TEM obser-
vations using ultramicrotomy techniques and the Servei de
Microscòpia de la UAB for HR-TEM observations.
References
[1] For some reviews dealing with the Suzuki cross-cou-
pling and its applications, see: a) A. R. Martin, Y.
Yang, Acta Chem. Scand. 1993, 47, 221; b) A. Suzuki,
Pure Appl. Chem. 1994, 66, 213; c) A. Suzuki, N.
Miyaura, Chem. Rev. 1995, 95, 2457; d) A. Suzuki, J.
Organomet. Chem. 1999, 576, 147; e) S. R. Chemler, D.
Trauner, S. J. Danishefsky, Angew. Chem. 2001, 113,
4676; Angew. Chem. Int. Ed. 2001, 40, 4544; f) S.
Kotha, K. Lahiri, D. Kashinath, Tetrahedron 2002, 58,
9633; g) A. Suzuki, J. Organomet. Chem. 2002, 653, 83;
h) F. Bellina, A. Carpita, R. Rossi, Synthesis 2004,
2419; i) A. Suzuki, Chem. Commun. 2005, 4759;
j) N. T. S. Phan, M. van der Sluys, C. W. Jones, Adv.
Synth. Catal. 2006, 348, 609.
[6] S. Cerezo, J. CortØs, J. M. López-Romero, M. Moreno-
MaÇas, T. Parella, R. Pleixats, A. Roglans, Tetrahedron
1998, 54, 14885.
[7] J. CortØs, M. Moreno-MaÇas, R. Pleixats, Eur. J. Org.
Chem. 2000, 239.
[8] a) B. Blanco, A. Mehdi, M. Moreno-MaÇas, R. Pleixats,
C. ReyØ, Tetrahedron Lett. 2004, 45, 8789; b) B. Blanco,
M. Brissart, M. Moreno-MaÇas, R. Pleixats, A. Mehdi,
C. ReyØ, S. Bouquillon, F. HØnin, J. Muzart, Appl. Cat.
[2] For some reviews dealing with the Heck reaction and
its applications, see: a) A. De Meijere, F. E. Meyer,
588
asc.wiley-vch.de
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Hybrid Organic-Inorganic Materials from Di-(2-pyridyl)methylamine-Palladium Dichloride
FULL PAPERS
A : General 2006, 297, 117; c) B. Blanco, M. Moreno-
MaÇas, R. Pleixats, A. Mehdi, C. ReyØ, J. Mol. Catal.
A: Chem. 2007, 269, 204.
Rothenberg, D. Gitis, D. Sasson, J. Org. Chem. 2000,
65, 3107; f) M. T. Reetz, M. Winter, R. Breinbauer, T.
Thurn-Albrecht, W. Vogel, Chem. Eur. J. 2001, 7, 1084;
g) N. Arul Dhas, A. Gedanken, J. Mater. Chem. 1998, 8,
445; h) M. T. Reetz, M. Maase, Adv. Mater. 1999, 11,
773; i) M. T. Reetz, E. Westermann, Angew. Chem.
2000, 112, 170; Angew. Chem. Int. Ed. 2000, 39, 165;
j) V. Calo, A. Nacci, A. Monopoli, S. Laera, N. Cioffi,
J. Org. Chem. 2003, 68, 2929; k) M. T. Reetz, J. G.
Vries, Chem. Commun. 2004, 1559; l) J. Le Bras, D. K.
Mukherjee, S. Gonzµlez, M. Tristany, B. Ganchegui, M.
Moreno-MaÇas, R. Pleixats, F. HØnin, J. Muzart, New J.
Chem. 2004, 28, 1550.
[9] For some reviews on the use of aryl chlorides in cross-
coupling and Heck reactions, see: a) A. F. Littke, G. C.
Fu, Angew. Chem. 2002, 114, 4350; Angew. Chem. Int.
Ed. 2002, 41, 4176; b) R. B. Bedford, C. S. J. Cazin, D.
Holder, Coord. Chem. Rev. 2004, 248, 2283.
[10] V. Farina, Adv. Synth. Catal. 2004, 346, 1553.
[11] J. A. Gladysz, Chem. Rev. 2002, 102, 3215.
[12] a) C. J. Brinker, G. W. Scherer, Sol-Gel Science, Aca-
demic Press, London, 1990; b) C. Sanchez, F. Ribot,
New J. Chem. 1994, 18, 1007; c) K. J. Shea, J. J. E.
Moreau, D. A. Loy, R. J. P. Corriu, B. Boury, in: Func-
tional Hybrid Materials, (Eds. P. Gómez-Romero, C.
Sanchez), Wiley-VCH, Weinheim, 2004, p 50.
[23] K. Nakamoto, Infrared and Raman Spectra of Inorganic
and Coordination Compounds, 4th edn., John Wiley
and Sons, Chichester 1986.
[13] a) U. Schubert, New J. Chem. 1994, 18, 1048; b) C.
Bied, D. Gauthier, J. J. E. Moreau, M. Wong Chi Man,
J. Sol-Gel Sci. Technol. 2001, 20, 313; c) R. Abu-Reziq,
D. Avnir, J. Blum, Angew. Chem. 2002, 114, 4306;
Angew. Chem. Int. Ed. 2002, 41, 4132; d) A. Brethon,
J. J. E. Moreau, M. Wong Chi Man, J. Sol-Gel Sci. Tech-
nol. 2004, 15, 495–502.
[14] a) M. R. Buchmeiser, K. Wurst, J. Am. Chem. Soc.
1999, 121, 11101; b) J. Silberg, T. Schareina, R. Kempe,
K. Wurst, M. R. Buchmeiser, J. Organomet. Chem.
2001, 622, 6.
[15] a) C. Nµjera, J. Gil-Moltó, S. Karlstrçm, L. Falvello,
Org. Lett. 2003, 5, 1451; b) C. Nµjera, J. Gil-Moltó, S.
Karslstrçm, Adv. Synth. Catal. 2004, 346, 1798; c) C.
Nµjera, J. Gil-Moltó, Eur. J. Org. Chem. 2005, 4073;
d) J. Gil-Moltó, C. Nµjera, Adv. Synth. Catal. 2006, 348,
1874.
[24] a) E. B. Mubofu, J. H. Clark, D. J. Macquarrie, Green
Chem. 2001, 3, 23; b) B. Gotov, D. J. Macquarrie, S.
Toma, Platinum Met. Rev. 2001, 45, 102; c) H. Kosslick,
I. Mçnnich, E. Paetzold, H. Fuhrmann, R. Fricke, D.
Müller, G. Oehme, Microporous Mesoporous Mater.
2001, 44–45, 537; d) C. Baleizao, A. Corma, H. García,
A. Leyva, Chem. Commun. 2003, 606; e) C. Baleizao,
A. Corma, H. García, A. Leyva, J. Org. Chem. 2004,
69, 439; f) N. Gurbuz, I. Ozdemir, B. Cetinkaya, T.
Seckin, Appl. Organomet. Chem. 2003, 17, 776; g) R. B.
Bedford, C. S. J. Cazin, M. B. Hursthouse, M. E. Light,
K. J. Pike, S. Wimperis, J. Organomet. Chem. 2001, 633,
173; h) P. Satya, J. H. Clark, J. Mol. Catal. A: Chem.
2004, 215, 107; i) K. Shimizu, S. Koizumi, T. Hatamachi,
H. Yoshida, S. Komai, T. Kodama, Y. Kitayama, J.
Catal. 2004, 228, 141; j) C. Gonzµlez-Arellano, A.
Corma, M. Iglesias, F. Sµnchez, Adv. Synth. Catal. 2004,
346, 1758; k) J. Horniakova, T. Raja, Y. Kubota, Y.
Sugi, J. Mol. Catal. A: Chem. 2004, 217, 73; l) N.
Gurbuz, I. Ozdemir, T. Seckin, B. Cetinkaya, J. Inorg.
Organomet. Polym. 2004, 14, 149; m) A. Corma, D.
Das, H. García, A. Leyva, J. Catal. 2005, 229, 322;
n) O. Vassylyev, J. Chen, A. P. Panarello, J. G. Khinast,
Tetrahedron Lett. 2005, 46, 6865; o) C. M. Crudden, M.
Sateesh, R. Lewis, J. Am. Chem. Soc. 2005, 127, 10045;
p) Q. Yang, S. Ma, J. Li, F. Xiao, H. Xiong, Chem.
Commun. 2006, 2495; q) R. B. Bedford, U. G. Singh,
R. I. Walton, R. T. Williams, S. A. Davis, Chem. Mater.
2005, 17, 701; r) S. Tandukar, A. Sen, J. Mol. Catal. A:
Chem. 2007, 268, 112; s) M. Al-Hashimi, A. C. Sullivan,
J. R. H. Wilson, J. Mol. Catal. A: Chem. 2007, 273, 298.
[25] a) J. H. Clark, D. J. Macquarrie, E. B. Mubofu, Green
Chem. 2000, 2, 53; b) M. Lagassi, P. Moggi, J. Mol.
Catal. A: Chem. 2002, 182–183, 61; c) B. M. Choudary,
N. S. Chowdari, K. Jyothi, N. S. Kumar, M. L. Kantam,
Chem. Commun. 2002, 586; d) S.-F. Zhao, R.-X. Zhou,
Y.-F. Yang, X.-M. Zheng, React. Kinet. Catal. Lett.
2003, 79, 333; e) R. Chanthateyanonth, H. Alper, J.
Mol. Catal. A: Chem. 2003, 201, 23; f) M. R. Buchmeis-
er, S. Lubbad, M. Mayr, K. Wurst, Inorg. Chim. Acta
2003, 345, 145; g) F.-Y. Tsai, Ch.-L. Wu, Ch-Y. Mou,
M.-C. Chao, H.-P. Lin, S.-T. Liu, Tetrahedron Lett.
2004, 45, 7503; h) S. F. Zhao, R. X. Zhou, X. M. Zheng,
J. Mol. Catal. A: Chem. 2004, 211, 139; i) M. Cai, Y.
Huang, H. Zhao, C. Song, React. Funct. Polym. 2004,
59, 81; j) N. T. S. Phan, D. H. Brown, H. Adams, S. E.
[16] J. Gil-Moltó, S. Karlstrçm, C. Nµjera, Tetrahedron
2005, 61, 12168.
[17] M. Trilla, R. Pleixats, M. Wong Chi Man, C. Bied,
J. J. E. Moreau, Tetrahedron Lett. 2006, 47, 2399.
[18] J. Chang, S. Plummer, E. S. F. Berman, D. Striplin, D.
Blauch, Inorg. Chem. 2004, 43, 1735.
À
[19] For the formation of C C bonds under catalysis by
transition metal nanoparticles see, for instance: a) M.
Moreno-MaÇas, R. Pleixats; Acc. Chem. Res. 2003, 36,
638; for adsorption of metal nanoparticles on supports
see, for instance: b) A. Roucoux, J. Schulz, H. Patin,
Chem. Rev. 2002, 102, 3757; for the stabilizing interac-
tion of bipyridyl ligands with Pd(0) nanoparticles see,
for instance: c) K. Naka, M. Yaguchi, Y. Chujo, Chem.
Mater. 1999, 11, 849.
[20] See, for instance: a) F. Zhao, B. M. Bhanage, M. Shirai,
M. Arai, Chem. Eur. J. 2000, 6, 843; b) A. Biffis, M.
Zecca, M. Basato, Eur. J. Inorg. Chem. 2001, 1131.
[21] a) B. Tao, D. W. Boykin, J. Org. Chem. 2004, 69, 4330;
b) M. Moreno-MaÇas, R. Pleixats, A. Serra-Muns, Syn-
lett 2006, 3001.
[22] a) H. Bçnnemann, W. Brijoux, R. Brinkmann, E.
Dinjus, T. Joussen, B. Korall, Angew. Chem. 1991, 103,
1344; Angew. Chem. Int. Ed. Engl. 1991, 30, 1312;
b) M. T. Reetz, W. Helbig, J. Am. Chem. Soc. 1994,
116, 7401; c) M. T. Reetz, W. Helbig, S. A. Quaiser, U.
Stimming, N. Breuer, R. Vogel, Science 1995, 267, 367;
d) Z. Kiraly, B. Veisz, A. Mastalir, Z. Razga, I. DØkany,
Chem. Commun. 1999, 1925; e) S. Mukhopadhyay, G.
Adv. Synth. Catal. 2008, 350, 577 – 590
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
589

Montserrat Trilla et al.
FULL PAPERS
Spey, P. Styring, Dalton Trans. 2004, 1348; k) C. Gon-
zµlez-Arellano, A. Corma, M. Iglesias, F. Sµnchez, Adv.
Synth. Catal. 2004, 346, 1758; l) K. Yu, W. Sommer, M.
Weck, C. W. Jones, J. Catal. 2004, 226, 101; m) C. Ven-
katesan, A. P. Singh, J. Catal. 2004, 227, 148; n) M. Cai,
G. Liu, J. Zhou, J. Mol. Catal. A: Chem. 2005, 227, 107;
o) K. Yu, W. Sommer, J. M. Richardson, M. Weck,
C. W. Jones, Adv. Synth. Catal. 2005, 347, 161; p) Q. Yu,
J. E. Hampsey, N. Jiang, Ch. Li, Y. Lu, Chem. Mater.
2005, 17, 1561; q) Y. Ji, S. Jain, R. J. Davis, J. Phys.
Chem. B 2005, 109, 17232; r) B. Karimi, D. Enders,
Org. Lett. 2006, 8, 1237; s) M. Cai, X. Tong, W. Hu, Y.
Huang, React. Funct. Polym. 2006, 66, 531; t) O. Aksin,
H. Türkmen, L. Artok, B. C¸ etinkaya, Ch. Ni, O.
Büyükgüngçr, E. Ozkal, J. Organomet. Chem. 2006,
691, 3027; u) H. Li, L. Wang, P. Li, Synthesis 2007,
1635; v) G. Singh, S. Bali, A. K. Singh, Polyhedron
2007, 26, 897; w) V. Polshettiwar, P. Hesemann, J. J. E.
Moreau, Tetrahedron 2007, 63, 6784; x) V. Polshettiwar,
P. Hesemann, J. J. E. Moreau, Tetrahedron Lett. 2007,
48, 5363.
[26] a) M. Cai, Q. Xu, J. Sha, J. Mol. Catal. A: Chem. 2007,
272, 293; b) M. Cai, J. Sha, Q. Xu, Tetrahedron 2007,
63, 4642; c) P.-H. Li, L. Wang, Adv. Synth. Catal. 2006,
348, 681; d) M. Cai, Q. Xu, P. Wang, J. Mol. Catal. A:
Chem. 2006, 250, 199; e) T. Posset, J. Blümel, J. Am.
Chem. Soc. 2006, 128, 8394; f) E. Tyrell, A. Al-Saardi,
J. Millet, Synlett 2005, 487; g) M. Bandini, R. Luque, V.
Budarin, D. J. Macquarrie, Tetrahedron 2005, 61, 9860.
[27] a) K. Hamza, R. Abu-Reziq, D. Avnir, J. Blum, Org.
Lett. 2004, 6, 925; b) A. Talhami, L. Penn, N. Jaber, K.
Hamza, J. Blum, App. Catal. A: General 2006, 312, 115.
[28] E. Niemers, R. Hiltmann, Synthesis 1976, 593.
[29] G. A. Olah, M. Arvanaghi, Y. D. Vankar, J. Org. Chem.
1980, 45, 3531.
[30] a) X. Cui, Z. Li, C.-Z. Tao, Y. Xu, J. Li, L. Liu, Q. X.
Guo, Org. Lett. 2006, 8, 2467; b) M. Dams, L. Drijko-
ningen, B. Panwels, G. V. Tendenloo, D. E. Vos, P. A.
Jacobs, J. Catal. 2002, 209, 225.
[31] a) P. Li, L. Wang, H. Li, Tetrahedron 2005, 61, 8633;
b) A. Arcadi, S. Cacchi, G. Fabrizi, F. Marinelli, P.
Pace, Eur. J. Org. Chem. 1999, 3305.
590
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Adv. Synth. Catal. 2008, 350, 577 – 590