‘‘DURSI-Generalitat de Catalunya (Project SGR 2001-00181
and 2001SGR00335)’’ is gratefully acknowledged. M. P. and
C. L. C. acknowledge the EU Marie Curie Training Site Grant
number: HPMT-CT-2000-0006 during their stage at the
ICMAB.
References
1
(a) A. C. Pierre and G. M. Pajonk, Chem. Rev., 2002, 102, 4243;
(b) N. Husing and U. Schubert, Angew. Chem. Int. Ed., 1998, 37,
22.
¨
Scheme 1 Mizoroki–Heck reactions tested.
2
3
S. A. Al-Mutaseb and J. A. Ritter, Adv. Mater., 2003, 15, 101.
S. Krompiec, J. Mroviec-Bialon, K. Skutil, A. Dukowicz, L. Pajak
and A. B. Jarzebski, J. Non-Cryst. Solids, 2003, 315, 297.
S. H. Lee, D. J. Suh, T. J. Park and K. L. Kim, Catal. Commun.,
2002, 3, 441.
Table 3 Results for Heck reactions shown in Scheme 1
4
5
6
Catalyst
Olefin Time (hours)
Product Yielda (%)
A. Ueno, H. Suzuki and Y. Kotera, J. Chem. Soc., Faraday Trans.
1, 1983, 79(1), 127–136.
Pd–SiO2 (1)
Pd–carbon (1)
Pd–carbon (2)
Pd–organic (3)
Pd–carbon (1)
Pd–carbon (2)
Pd–organic (3)
Pd–carbon (2)
Pd–organic (3)
a
2
2
2
2
3
3
3
4
4
5/4 days
47/41/44/18/120
24/24/25/25/24
5
5
5
5
6
6
6
7
7
70/64
90/81/70/99/12
S. Martı
Moreno-Manas, A. Roig, R. M. Sebastia
Tetrahedron, 2003, 59, 1553.
C. Moreno-Castilla and F. J. Maldonado-Ho
43, 455.
´
nez, M. Meseguer, L. Casas, E. Rodriguez, E. Molins, M.
a
´
n and A. Vallribera,
9/15/23
7 days
3
a
79
70
a
7
8
´
dar, Carbon, 2005,
(a) T. F. Baumann and J. H. Satcher Jr., Chem. Mater., 2003, 15,
3745; (b) T. F. Baumman, G. A. Fox and J. H. Satcher Jr.,
Langmuir, 2002, 18, 7073.
´ ´
F. J. Maldonado-Hodar, C. Moreno-Castilla and A. F. Perez-
Cadenas, Microporous Mesoporous Mater., 2004, 69, 119.
15
30
90
a
50
9
Quantitative conversion by CLC chromatography.
10 L. C. Cotet, M. Gich, A. Roig, I. C. Popescu, V. Cosoveanu, E.
Molins and V. Danciu, unpublished results.
activity in the second cycle (Table 3). Analysis of the crude
reaction mixture for the first reaction indicates a leaching
of 2% and 3% of the palladium present in Pd–organic (3)
and Pd–carbon (2) aerogels, respectively. The Pd–SiO2 aerogel
was less active and the analysis of the crude reaction mixture
showed a leaching of 11% of the metal. As we have mentioned,
the synthesis of the organic and carbon aerogels was based on
the use of a resorcinol derivative containing an ion exchange
moiety that could be polymerized using sol-gel techniques. As a
result, each repeating unit of the organic polymer contains a
binding site for the metal ions, securing a uniform dispersion of
the dopant metal. A high dispersion of the active sites max-
imizes the contact of the catalyst with the reactants and can ex-
plain the difference in catalytic activity found between organic
and inorganic Pd aerogels. In the cases of the Mizoroki–
Heck reactions of iodobenzene with styrene and with 3-bu-
ten-2-one good results were obtained (Table 3) although the
catalysts cannot be reused without decrease of activity. Poly-
merization of the styrene and 3-buten-2-one inside the active
sites of the aerogel could be an explanation for the decreased
activity.
11 R. Monaci, A. Musinu, G. Piccaluga and G. Pinna, Mater. Sci.
Forum, 1995, 195, 1–6.
12 G. Ennas, A. Mei, A. Musinu, G. Piccaluga, G. Pinna and S.
Solinas, J. Non-Cryst. Solids, 1998, 232–234, 587.
13 T. Ueckert, R. Lamber, N. I. Jaeger and U. Schubert, Appl. Catal.,
A, 1997, 155, 75.
14 A. Corrias, G. Ennas, A. Musini, G. Paschina and D. Zedda,
J. Mater. Res., 1997, 2, 2767.
15 A. Bhattacharyya, P. C. Chakraborti, S. Mukherjee, M. K. Mitra
and G. C. Das, Sci. Technol. Adv. Mater., 2001, 2, 449.
16 G. E. E. Gardes, G. Pajonk and S. J. Teichner, Bull. Soc. Chim.
Fr., 1976, 1327–1332.
17 B. Heinrichs, F. Noville and J.-P. Pirard, J. Catal., 1997, 170,
366.
18 K. S. Morley, P. Licence, P. C. Marr, J. R. Hyde, P. D. Brown, R.
Mokaya, Y. Xia and S. M. Howdle, J. Mater. Chem., 2004, 14,
1212.
19 M. Popovici, M. Gich, A. Roig, L. Casas, E. Molins, C. Savii, D.
´
Becherescu, J. Sort, S. Surinach, J. S. Munoz, M. D. Baro and J.
Nogues, Langmuir, 2004, 20, 1425.
´
20 C. J. Brinker and G. W. Scherrer, Sol-Gel Science: The Physics and
Chemistry of Sol-Gel Processing, Academic Press, San Diego,
1990.
21 For an excellent review on the Mizoroki–Heck reaction catalyzed
by supported palladium see: A. Biffis, M. Zecca and M. Basato, J.
Mol. Catal. A: Chem., 2001, 173, 249.
22 For silica featuring coordinating groups see: (a) Q. Hu, J. E.
Hampsey, N. Jiang, C. Li and Y. Lu, Chem. Mater., 2005, 17,
1561; (b) K. Shimizu, S. Koizumi, T. Hatamachi, H. Yoshida, S.
Komai, T. Kodama and Y. Kitayama, J. Catal., 2004, 228, 141; (c)
for Pd directly supported on silica see: N. Kim, M. S. Kwon, C. M.
Park and J. Park, Tetrahedron Lett., 2004, 45, 7057.
23 For catalysis by palladium on carbon nanotubes see: A. Corma,
´
H. Garcıa and A. Leyva, J. Mol. Catal. A: Chem., 2005, 230, 97.
24 For catalysis by palladium on mesoporous carbon obtained by a
sol-gel technique see: Q. Hu, J. Pang, N. Jiang, J. E. Hampsey and
Y. Lu, Microporous Mesoporous Mater., 2005, 81, 149.
25 For catalysis by Pd–C see: (a) M. Gruber, S. Chouzier, K. Koehler
and L. Djakovitch, Appl. Catal., A, 2004, 265, 161; (b) ref. 22b; (c)
A. Perosa, P. Tundo, M. Selva, S. Zinovyev and A. Testa, Org.
Biomol. Chem., 2004, 2, 2249; (d) F. Zhao and M. Arai, React.
The Mizoroki–Heck reaction catalyzed by palladium on solid
support has recently attracted a great deal of attention.21 More
recently some silica gels have been prepared as supports for
catalysts of the Mizoroki–Heck reaction.22 However, in general
carbon supports seem to give better results than silica.23–25
Conclusion
Different organic and inorganic aerogels containing Ni and Pd
nanoparticles have been prepared through sol-gel processes.
The materials were fully characterized. Nanosized metallic Pd
nanoparticles were formed even in precarbonized Pd–organic
aerogels. In no case were deliberate reduction steps necessary.
We have also demonstrated that organic and carbon aerogels
doped with Pd are good catalysts for the Mizoroki–Heck
reaction. Carbon aerogels can be reutilized several times. Our
results hold promise although require further development.
Kinet. Catal. Lett., 2004, 81, 281; (e) K. Kohler, R. G. Heiden-
¨
reich, J. G. E. Krauter and J. Pietsch, Chem. Eur. J., 2002, 8, 622;
(f) R. G. Heidenreich, J. G. E. Krauter, J. Pietsch and K. Kohler,
¨
J. Mol. Catal. A: Chem., 2002, 182–183, 499; (g) F.-Y. Zhao, M.
Shirai, Y. Ikushima and M. Arai, J. Mol. Catal. A: Chem., 2002,
180, 211; (h) R. G. Heidenreich, K. Kohler, J. G. E. Krauter and J.
¨
Pietsch, Synlett, 2002, 1118; (i) K. Kohler, M. Wagner and L.
¨
Djakovitch, Catal. Today, 2001, 66, 105.
Acknowledgements
´
Financial support from ‘‘Ministerio de Educacion y Ciencia of
Spain’’ (Project BQU 2002-04002 and MAT2003-01052) and
N e w J . C h e m . , 2 0 0 5 , 2 9 , 1 3 4 2 – 1 3 4 5
1345