New approach for size- and shape-controlled preparation of Pd nanoparticles with organic ligands. Synthesis and application in catalysis

Article abstract of DOI:10.1021/ja071727r

A novel approach was developed to prepare Pd nanoparticles with organic ligands in high yields. The structural unit of the Pd species was constructed involving Pd-S bonds. The synthesized Pd particles were highly selective catalysts of S-H bond addition to alkynes under microwave heating. An X-ray diffraction study of one of the products of the addition reaction revealed unusual supramolecular organization of cation/anion layers. Copyright

Full text of DOI:10.1021/ja071727r

Published on Web 05/19/2007
New Approach for Size- and Shape-Controlled Preparation of Pd
Nanoparticles with Organic Ligands. Synthesis and Application in Catalysis
Valentine P. Ananikov,*,† Nikolay V. Orlov,† Irina P. Beletskaya,*,‡ Victor N. Khrustalev,§
Mikhail Yu. Antipin,§ and Tatiana V. Timofeeva#
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Pr. 47, Moscow, 119991, Russia,
Chemistry Department, LomonosoV Moscow State UniVersity, Vorob’eVy gory, Moscow, 119899, Russia,
NesmeyanoV Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, Russia, and
Department of Natural Sciences, New Mexico Highlands UniVersity, Las Vegas, New Mexico 87701
Received March 21, 2007; E-mail: val@ioc.ac.ru; beletska@org.chem.msu.ru
One-dimensional (1D) nanostructures have attracted much at-
tention because of their potential application in numerous fields of
science and engineering. Presently, a tremendous amount of research
activity is under way for the use of 1D nanostructures (such as
nanowires, nanotubes, nanobelts, and nanofibers) as well-defined
building units for the fabrication of various nanoscale devices.1 In
addition to the field of nanoscale devices precursors, 1D nano-
structures with organic ligands could be of great importance for
carrying out highly selective chemical transformations in a catalytic
manner.1d,p Special procedures have been developed for the
preparation of inorganic (1D) nanostructures based on metal
Figure 1. Low magnification (A, 1000×) and high magnification (B,
8000×, C, 16000×) SEM images of [Pd(SCy)2]n (4a).
chalcogenides MxZy (M ) Zn, Sn, In, Cd, Ga, Pb, Pd; Z ) O, S,
Scheme 1. Reaction of PdX2 with Thiols in the Presence of
Alkyne (1)
Se).2,3 However, these methods involve harsh reaction conditions,
and they are unsuitable for the preparation of nanostructures with
organic ligands. Not surprisingly, the application of 1D nanostruc-
tures with organic ligands remains unexplored.3
Out recent report on the preparation of Ni particles of 300 ( 90
nm size range (nearly spherical shape; SAr and SeAr organic
ligands) provided an important evidence for their potential utiliza-
tion in catalysis.4 High selectivity and yields have been achieved
in ArEH (E ) S, Se) addition to the triple bond of alkynes under
mild conditions.4
Here we report a novel approach for the preparation of 1D Pd
nanoparticles with organic ligands using size- and shape-controlled
chemical synthesis from easily available reagents under mild
reaction conditions. An even more complicated problem, selective
addition of AlkSH to alkynes,5,6 has been solved utilizing these
nanoparticles as catalysts.
Pd(OAc)2 dissolved in alkyne (2) reacted with cyclohexylthiol
(X ) OAc, R ) Cy; Scheme 1) and led to the formation of
nanostructured Pd species 4a with 85% yield. We have observed
that interaction of Pd(OAc)2 with 1 is a flexible size-controlling
tool: either nm- or µm-scale Pd species have been prepared
depending on the reaction conditions.7 Utilizing insoluble PdCl2
(X ) Cl) in the reaction has resulted only in a µm-scale species
(X ) Cl, R ) Cy; Scheme 1).
Scanning electron microscopy (SEM) study revealed a network
of 1D nanobelts with 1-2 µm length, 100-200 nm width, and
40-80 nm thickness (Figure 1). A high degree of three-dimensional
(3D) networking with certain void spaces (Figure 1) makes the
nanobelts sites easily accessible by other molecules, thus worth
trying in catalysis.
We have found that nanobelts 4a prepared in situ do catalyze
the addition of CySH to 1 leading to Markovnikov-type product 5
with excellent selectivity and yields (Table 1). It is important to
note that the catalyst particles size and shape do not change in a
noticeable manner after completing the reaction. Nanostructured
organization of the catalyst (Figure 1) was the key factor of high-
catalytic activity. The particles of µm-size range with the same
chemical composition [Pd(SCy)2]n have been dramatically less
active compared to 4a.8
The catalyst was tolerant to typical organic functional groups in
alkynes (entries 1-4; Table 1); even the activated alkyne 1e (known
to undergo a rapid side-reaction leading to 6 and 7) reacted with
good selectivity in the developed nanocatalytic system (entry 5,
Table 1). The catalytic reaction has been successfully performed
under conventional and microwave heating, the latter conditions
provided better yields (Table 1).9
Varying the nature of R we have found that benzylthiol (BnSH)
have reacted with lower yields. SEM study of the catalyst [Pd-
(SBn)2]n 4b prepared in this case detected the formation of a 3D
structure consisting of nanosized particles of 0.7-2 µm length and
200-400 nm diameter (mostly rod-shaped).7 This observation
confirms the key role of the nanostructured catalyst organization.
Despite slightly lower catalyst activity, the products 5f and 5g have
been synthesized with good yields and excellent selectivity (entries
6, 7; Table 1).
X-ray structure of oxalic salt of 5d revealed unusual crystal
packing which is built up by the alternate pairs of anion and cation
layers (Figure 2). The anions bound in the chains along b-axis by
the O-H‚‚‚O hydrogen bonds form sheets parallel to (100).8 Such
† Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences.
‡ Lomonosov Moscow State University.
§ Nesmeyanov Institute of Organoelement Compounds, Russian Academy of
Sciences.
# New Mexico Highlands University.
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J. AM. CHEM. SOC. 2007, 129, 7252-7253
10.1021/ja071727r CCC: $37.00 © 2007 American Chemical Society

C O M M U N I C A T I O N S
Scheme 2. Plausible Mechanism of the Catalytic Reaction
Table 1. Pd-Nanoparticles Catalyzed Regioselective RSH
Addition to Alkynes under Microwave Heatinga
alkanethiol, respectively. Synthesized Pd nanoparticles with organic
ligands showed promising results for the application in catalysis.
Supporting Information Available: Experimental procedures,
compounds characterization data, details of SEM and X-ray studies.
References
(1) For representative examples, see: (a) Law, M.; Greene, L. E.; Johnson,
J. C.; Saykally, R.; Yang, P. D. Nat. Mater. 2005, 4, 455. (b) Baker, G.
A. AdV. Mater. 2005, 17, 639. (c) Gao, P. X.; Ding, Y.; Mai, W. J.;
Hughes, W. L.; Lao, C. S.; Wang, Z. L. Science 2005, 309, 1700. (d)
Kolmakov, A.; Moskovits, M. Annu. ReV. Mater. Res. 2004, 34, 151. (e)
Wang, Z. L. Annu. ReV. Phys. Chem. 2004, 55, 159. (f) Law, M.; Sirbuly,
D. J.; Johnson, J. C.; Goldberg, J.; Saykally, R. J.; Yang, P. D. Science
2004, 305, 1269. (g) Li, Q.; Gong, X.; Wang, C.; Wang, J.; Ip, K.; Hark,
S. AdV. Mater. 2004, 16, 1436. (h) Yan, H. Q.; Johnson, J.; Law, M.; He,
R.; Knutsen, K.; McKinney, J. R.; Pham, J.; Saykally, R.; Yang, P. D.
AdV. Mater. 2003, 15, 1907. (i) Xia, Y.; Yang, P.; Sun, Y.; Wu, Y.;
Mayers, B.; Gates, B.; Yin, Y.; Kim, F.; Yan, H. AdV. Mater. 2003, 15,
353. (j) Duan, X.; Huang, Y.; Agarwal, R.; Lieber, C. M. Nature (London)
2003, 421, 241. (k) Wang, Z. L. AdV. Mater. 2003, 15, 432. (l) Gudiksen,
M. S.; Lauhon, L. J.; Wang, J.; Smith, D. C.; Lieber, C. M. Nature
(London) 2002, 415, 617. (m) Pan, Z. W.; Dai, Z. R.; Wang, Z. L. Science
2001, 291, 1947. (n) Wang, Z. L.; Gao, R. P.; Pan, Z. W.; Dai, Z. R.
AdV. Eng. Mater. 2001, 3, 657. (o) Hu, J.; Odom, T. W.; Lieber, C. M.
Acc. Chem. Res. 1999, 32, 435. (p) Astruc, D. Inorg. Chem. 2007, 46,
1884.
(2) (a) Nanoparticles and Nanostructured Films. Preparation, Characteriza-
tion and Applications; Fendler, J. H., Ed.; Wiley-VCH, Weinheim,
Germany, 1998. (b) Nanoparticles: From Theory to Application; Schmid,
G., Ed.; Wiley-VCH, Weinheim, Germany, 2004.
a RSH (1.1 mmol), alkyne (1 mmol), γ-terpinene (1 mmol), Pd(OAc)2
(5 mol %) under microwave heating. b Alkyne conversion determined by
NMR and isolated yield of 5 (in parenthesis). c The 5/(6 +7) ratio.
(3) (a) Astruc, D.; Lu, F.; Aranzaes, J. R. Angew. Chem., Int. Ed. 2005, 44,
7852. (b) Burda, C.; Chen, X.; Narayanan, R.; El-Sayed, M. A. Chem.
ReV. 2005, 105, 1025. (c) Grunes, J.; Zhu, J.; Somorjai, G.A. Chem.
Commun. 2003, 2257. (d) Bell, A. T. Science 2003, 299, 1688. (e) Johnson,
B. F. G. Top. Catal. 2003, 24, 147. (f) Moreno-Manas, M.; Pleixats, R.
Acc. Chem. Res. 2003, 36, 638. (g) Buchachenko, A. L. Russ. Chem. ReV.
2003, 72, 375. (h) Roucoux, A.; Schulz, J.; Patin, H. Chem. ReV. 2002,
102, 3757. (i) Moiseev, I. I.; Vargaftik, M. N. Russ. J. Gen. Chem. 2002,
72, 512. (j) El-Sayed, M. A. Acc. Chem. Res. 2001, 34, 257. (k) Crooks,
R. M.; Zhao, M.; Sun, L.; Chechik, V.; Yeung, L. K. Acc. Chem. Res.
2001, 34, 181. (l) Bukhtiyarov, V. I.; Slin’ko, M. G. Russ. Chem. ReV.
2001, 70, 147.
(4) (a) Ananikov, V. P.; Orlov, N. V.; Beletskaya, I. P.; Organometallics
2006, 25, 1970. (b) Ananikov, V. P.; Orlov, N. V.; Beletskaya, I. P.;
Organometallics 2007, 26, 740.
(5) In the reactions of interest alkanethiols are dramatically less reactive
compared to arylthiols because of stronger S-H bond and lower acidity
(see section 3 of the Supporting Information for BDE and pKa values).
At the moment only quite expensive homogeneous Rh systems were
reported to catalyze the transformations of that type involving AlkS groups,
see: (a) Arisawa, M.; Yamaguchi, M. Org. Lett. 2001, 3, 763. (b) Circu,
V.; Fernandes, M. A.; Carlton, L. Polyhedron 2003, 22, 3293. (c) Cao,
C.; Fraser, L. R.; Love, J. A. J. Am. Chem. Soc. 2005, 127, 17614. (d)
Misumi, Y.; Seino, H.; Mizobe, Y. J. Organomet. Chem. 2006, 691, 3157.
(6) For ArSH addition to alkynes see: (a) Malyshev, D. A.; Scott, N. M.;
Marion, N.; Stevens, E. D.; Ananikov, V. P.; Beletskaya, I. P.; Nolan, S.
P. Organometallics 2006, 25, 4462. (b) Ananikov, V. P.; Malyshev, D.
A.; Beletskaya, I. P.; Aleksandrov, G. G.; Eremenko, I. L. AdV. Synth.
Catal. 2005, 347, 1993. (c) Han, L.-B.; Zhang, C.; Yazawa, H.; Shimada,
S. J. Am. Chem. Soc. 2004, 126, 5080. (d) Ogawa, A. J. Organomet. Chem.
2000, 611, 463. (e) Ogawa, A.; Ikeda, T.; Kimura, K.; Hirao, T. J. Am.
Chem. Soc. 1999, 121, 5108. (f) Backvall, J.-E.; Ericsson, A. J. Org. Chem.
1994, 59, 5850. (g) Kuniyasu, H.; Ogawa, A.; Sato, K.; Ryu, I.; Kambe,
N.; Sonoda, N.; J. Am. Chem. Soc. 1992, 114, 5902. (h) See also refs 4a
and 5c.
Figure 2. Molecular structure (a) and crystal packing (b) of 5d‚HOOC-
COOH.
a supramolecular structure has never been observed in the case of
aryl derivatives studied earlier.6
The mechanism of the catalytic reaction (Scheme 2) involves
alkyne coordination to form 8 (step i), followed by alkyne insertion
into the Pd-S bond leading to vinylic derivative 9 (ii). The final
stage of the catalytic cycle is protonolysis by RSH, which releases
5 and regenerates the active form of the catalyst 4 (iii). The proposed
mechanism has been confirmed by a series of stoichiometric
reactions performed with the isolated catalysts 4a and 4b.10
To summarize, the developed system is suitable for size- and
shape-controlled synthesis of nanoparticles achieved via the usage
of a solution of Pd precursor in alkyne and varying the nature of
(7) See section 2 of the Supporting Information for experimental details.
(8) See the Supporting Information for detailed description.
(9) Description of both procedures is given in section 4 of the Supporting
Information.
(10) Mechanistic study is described in section 5 of the Supporting Information.
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