Novel 3D coordination palladium-network complex: A recyclable catalyst for Suzuki-Miyaura reaction

Article abstract of DOI:10.1021/ol0615026

(Chemical Equation Presented) A novel solid-phase 3D metal-organic coordination network catalyst was prepared via self-assembly from PdCl ₂(CH₃CN)₂ and a trisphosphine hub with three flexible alkyl-chain linkers. This insoluble network complex efficiently catalyzed the Suzuki-Miyaura reaction under atmospheric conditions in water. This catalyst was reused without loss of catalytic activity.

Full text of DOI:10.1021/ol0615026

ORGANIC
LETTERS
2006
Vol. 8, No. 19
4259-4262
Novel 3D Coordination
Palladium Network Complex: A
−
Recyclable Catalyst for Suzuki
−Miyaura
Reaction†
Yoichi M. A. Yamada, Yasunari Maeda, and Yasuhiro Uozumi*
Institute for Molecular Science, Myodaiji, Okazaki, Aichi 444-8787, Japan
uo@ims.ac.jp
Received June 19, 2006
ABSTRACT
A novel solid-phase 3D metal−organic coordination network catalyst was prepared via self-assembly from PdCl2(CH3CN)2 and a trisphosphine
hub with three flexible alkyl-chain linkers. This insoluble network complex efficiently catalyzed the Suzuki
conditions in water. This catalyst was reused without loss of catalytic activity.
−Miyaura reaction under atmospheric
The development of metal-organic 3D coordination network
complexes is an important topic for supramolecular chem-
istry. Their use in storage, channels, and catalysts already
has attracted much attention.1 However, the construction of
recyclable catalytic systems using insoluble metal-organic
3D coordination network complexes has yet to be addressed.2
Although complexes with a rigid linkage between metals and
nonflexible organic ligands have been applied to heteroge-
neous catalysis and have been acknowledged as pioneering
work in this field,3 we believe that the development of novel
3D network catalyst systems with high activity and re-
usability still remains a major challenge. Having previously
developed metal-cross-linked polymeric complexes via self-
assembly of metal species with non-cross-linked polymer
ligands (Scheme 1, top) that catalyze various organic
transformations with high activity and reusability under
heterogeneous conditions,4 we then envisioned a self-
assembling strategy for the preparation of metal-cross-linked
polymeric complexes that could be applied to the construc-
tion of novel 3D coordination metal-network complexes
† Y.M.A.Y. sincerely dedicates this manuscript to Prof. K. C. Nicolaou
on the occasion of his 60th birthday.
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10.1021/ol0615026 CCC: $33.50
© 2006 American Chemical Society
Published on Web 08/17/2006

Although this type of flexible alkyl-chain tether has not been
used for the preparation of insoluble 3D metal-network
complexes, hydrophobic alkyl-chain tethers would be critical
in forming a pliable network to capture organic substrates
efficiently in the matrix of a 3D palladium complex promot-
ing a given catalytic reaction. In this communication, we
would like to present the successful preparation of a 3D
coordination metal-network complex of palladium, which
showed high catalytic activity and recyclability in the
Suzuki-Miyaura reaction in water under heterogeneous
conditions.4d,g,6,7 In the catalytic system, both the reaction
and the workup were carried out only with water in the
absence of organic solvents.
Scheme 1
A novel 3D palladium-network complex A was obtained
by self-assembly of the PdCl2 and C3-trisphosphine 4, which
was prepared from the commercially available 2,4,6-tris-
(bromomethyl)mesitylene (1) in four steps (Scheme 2). Thus,
etherification of the tribromide 1 with THPO(CH2)6OH, a
component of the alkyl-chain tether, followed by removal
of the tetrahydropyranyl groups gave the triol 2. After
mesylation of the triol 2, the triarylphosphine groups were
introduced by etherification of the resulting trimesylate 3
with 4-(diphenylphosphino)phenol to give the C3-triphos-
phine 4 in 30% overall yield (four steps from 1). A 3D
coordination palladium-network complex was prepared by
mixing PdCl2(CH3CN)2 and 0.67 mol equiv of 4 (2 mol equiv
of phosphine) in toluene at 100 °C for 24 h, during which
complex A formed as a yellow gel from the reaction mixture.
Complex A is insoluble in dichloromethane, chloroform,
toluene, methanol, and water. To elucidate the structure of
using a metal species and a multicoordinating ligand
monomer as the connecter and the hub of the molecular
network, respectively. With catalytic utility in mind, we
designed a metal-network complex of a C3-trisphosphine
with flexible alkyl-chain tethers and a palladium species
through Pd-P coordination (Schemes 1 (bottom) and 2),
Scheme 2
(4) For a review, see: (a) Yamada, Y. M. A. Chem. Pharm. Bull. 2005,
53, 723. For recent examples, see: (b) Yamada, Y. M. A.; Ichinohe, M.;
Takahashi, H.; Ikegami, S. Org. Lett. 2001, 3, 1837. (c) Yamada, Y. M.
A.; Ichinohe, M.; Takahashi, H.; Ikegami, S. Tetrahedron Lett. 2002, 43,
3431. (d) Yamada, Y. M. A.; Takeda, K.; Takahashi, H.; Ikegami, S. Org.
Lett. 2002, 4, 3371. (e) Yamada, Y. M. A.; Tabata, H.; Takahashi, H.;
Ikegami, S. Synlett 2002, 2031. (f) Yamada, Y. M. A.; Takeda, K.;
Takahashi, H.; Ikegami, S. Tetrahedron Lett. 2003, 44, 2379. (g) Yamada,
Y. M. A.; Takeda, K.; Takahashi, H.; Ikegami, S. J. Org. Chem. 2003, 68,
7733. (h) Yamada, Y. M. A.; Tabata, H.; Ichinohe, M.; Takahashi, H.;
Ikegami, S. Tetrahedron 2004, 60, 4087. (i) Yamada, Y. M. A.; Takeda,
K.; Takahashi, H.; Ikegami, S. Tetrahedron 2004, 60, 4097. (j) Hamamoto,
H.; Suzuki, Y.; Yamada, Y. M. A.; Tabata, H.; Takahashi, H.; Ikegami, S.
Angew. Chem., Int. Ed. 2005, 44, 4536. (k) Yamada, Y. M. A.; Uozumi,
Y. Org. Lett. 2006, 8, 1375.
(5) Cage-structured platinum complexes with trisphosphines have been
reported. (a) Lindner, E.; Hermann, C.; Baum, G.; Fenske, D. Eur. J. Org.
Chem. 1999, 679. (b) Lindner, E.; Khanfar, M.; Steimann, M. Eur. J. Org.
Chem. 2001, 2411.
(6) We have already reported PS-PEG resin-supported Pd catalysts for
the Suzuki-Miyaura reaction in water; see: (a) Uozumi, Y.; Danjo, H.;
Hayashi, T. J. Org. Chem. 1999, 64, 3384. (b) Uozumi, Y.; Nakai, Y. Org.
Lett. 2002, 4, 2997. (c) Uozumi, Y.; Kikuchi, M. Synlett 2005, 1775.
(7) For reviews, see: (a) Uozumi, Y. Top. Curr. Chem. 2004, 242, 77.
(b) Frenzel, T.; Solodenko, W.; Kirschning, A. In Polymeric Materials in
Organic Synthesis and Catalysis; Buchmeiser, M. R., Ed.; Wiley-VCH:
Weinheim, 2003; p 201. (c) Leadbeater, N. E. Chem. Commun. 2005, 2881.
(d) Bai, L.; Wang, J.-X. Curr. Org. Chem. 2005, 9, 535. (e) Nicolaou, K.
C.; Bulger, P. G.; Sarlah, D. Angew. Chem., Int. Ed. 2005, 44, 4442 and
references therein. For selected recent examples, see: (f) Thiot, C.; Schmutz,
M.; Wagner, A.; Mioskowski, C. Angew. Chem., Int. Ed. 2006, 45, 2868.
(g) Nishio, R.; Sugiura, M.; Kobayashi, S. Org. Lett. 2005, 7, 4831. (h)
Solodenko, W.; Scho¨n, U.; Messinger, J.; Glinschert, A.; Kirschning, A.
Synlett 2004, 1699. (i) Baleiza˜o, C.; Corma, A.; Garc´ıa, H.; Leyva, A. J.
Org. Chem. 2004, 69, 439. (j) Tzchucke, C. C.; Bannwarth, W. HelV. Chim.
Acta 2004, 87, 2882. (k) Mori, K.; Yamaguchi, K.; Hara, T.; Mizugaki, T.;
Ebitani, K.; Kaneda, K. J. Am. Chem. Soc. 2002, 124, 11572. (l) Kim, S.-
W.; Kim, M.; Lee, W. Y.; Hyeon, T. J. Am. Chem. Soc. 2002, 124, 7642.
(m) Gordon, R. S.; Holmes, A. B. Chem. Commun. 2002, 640.
where a palladium species serves as a connecter of the C3-
trisphosphine hub and as a catalytically active center.5
4260
Org. Lett., Vol. 8, No. 19, 2006

complex A, several micro- and spectroscopic measurements
were carried out. The morphology of A was evaluated by
optical- and scanning electron-microscopic (SEM) observa-
tions, which confirmed A to be blocklike and 50-500 µm
wide (Figure 1A). An energy dispersive spectrum (EDS)
with 0.05 mol % of Pd of complex A in an aqueous solution
of Na2CO3 (3 mol equiv) at 100 °C for 3 h under atmospheric
conditions to give the 4-methyl biphenyl (8aA) in quantitative
yield. After the first reaction, the recovered catalyst was
successively subjected to a second, third, and fourth series
of the reaction under similar conditions to afford 91%, 95%,
and 90% yield of 8aA, respectively. In the fourth run, the
product was isolated using hot water without use of organic
solvents.4g,9 Thus, after completion of the reaction, the
reaction mixture was filtered with boiling water to recover
the insoluble complex A. The aqueous filtrate was cooled
to 25 °C to give 8aA as colorless crystals (Scheme 3).
Scheme 3
With a practical and green catalytic protocol for the
Suzuki-Miyaura reaction in hand, we next examined the
coupling of a variety of aryl halides and arylboronic acids
in water (Scheme 4 and Table 1). Twenty-seven combina-
Figure 1. Microscopic and spectroscopic data of complex A. (A)
SEM image; (B) 31P{1H} NMR spectrum; (C) EDS spectrum.
Scheme 4
collected in the SEM exhibited the presence of Pd, Cl, and
P in the complex (Figure 1C). In the gel-phase 31P{1H} MAS
NMR study of complex A, the narrow singlet at δ -7.1 ppm
observed for the starting triphosphine 4 disappeared and was
replaced by a new resonance at δ +20 ppm (Figure 1B).
The remarkable low-field shift demonstrates that the tri-
arylphosphino unit of 4 coordinates to the palladium forming
a PdCl2(PAr3)2 complex (connecter-hub complex) in the gel
matrix.
To explore the catalytic potential of the palladium-
network complex A, we elected to study the Suzuki-Miyaura
reaction, the palladium-catalyzed cross-coupling of aryl
halides with arylboronic acids, which is recognized as one
of the most powerful carbon-carbon bond-forming reac-
tions.8 We were pleased to find that the network complex
catalyzed the coupling reaction under atmospheric conditions
in water without organic solvents to achieve a high level of
chemical greenness. The reaction of iodobenzene (5a) with
p-tolylboronic acid (7A) (1.5 mol equiv) took place smoothly
tions of six varieties of aromatic halides and six varieties of
arylboronic acids were subjected to the coupling in aqueous
Na2CO3 at 100 °C for 3 h using 0.05 mol % of palladium of
complex A. Electron-deficient as well as electron-rich aryl
halides readily coupled with arylboron reagents bearing
para-, meta-, and ortho-EWG and EDG substituents to give
the corresponding biaryls in 80 f 99% yields.
(9) After completion of the reaction, the reaction mixture (100 °C) was
filtered through a glass filter at 100 °C, and the collected polymeric catalyst
was rinsed with hot water. The filtrate was cooled to 25 °C to precipitate
colorless crystals of 8aA at the top of the water phase. They were collected
by filtration, washed with water, and dried in vacuo.
(10) These products were isolated via chromatographic purification of
the samples that were used for GC analysis.
(8) (a) Miyaura, N.; Suzuki, A. Chem. ReV. 1995, 95, 2457. (b) Suzuki,
A.; Brown, H. C. Organic Synthesis via Boranes. Suzuki Coupling;
Aldrich: Milwaukee, 2003; Vol. 3. (c) Frisch, A. C.; Beller, M. Angew.
Chem., Int. Ed. 2005, 44, 674. (d) Barder, T. E.; Walker, S. D.; Martinelli,
J. R.; Buchwald, S. L. J. Am. Chem. Soc. 2005, 127, 4685. (e) Gonzalez-
Bobes, F.; Fu, G. C. J. Am. Chem. Soc. 2006, 128, 5360.
Org. Lett., Vol. 8, No. 19, 2006
4261

hub ligand was developed as an aqua-catalytic insoluble
composite. The Suzuki-Miyaura reaction of a variety of aryl
halides with arylboronic acids took place with the insoluble
network complex A to afford the desired products in high
yields. The catalyst A promoted the reaction under atmo-
spheric conditions in water with recyclability. Applications
of the metal-network complexation with other metal species
for various catalytic reaction systems are currently under
study in our labs.
Table 1. Suzuki-Miyaura Reaction of Aryl Halides with
Arylboronic Acids Catalyzed by Complex A in Watera
yield
yield
(%)b
entry 5 or 6
7
8
(%)b entry 5 or 6
7
8
1
2
3
4
5
6
7
8
9
10
11
12
13
14
5a
5a
5a
5a
5a
5a
5b
5b
5b
5b
5b
5b
5c
5c
7A 8aA >99
15
16
17
18
19
20
21
22
23
24
25
26
27
5c
5c
5c
6a
6a
6a
6a
6b
6b
6b
6b
6b
6c
7D 8cD 92
7E 8cE 85
7F 8cF
7B 8aB
7C 8aC
7D 8aD
7E 8aE
7F 8aF
7A 8bA
7B 8bB
7C 8bC
7D 8bD
91
99c
99c
91
98c
7A 8aA 80
7B 8aB 92
7C 8aC 98
7D 8aD 92
7A 8bA 85
7B 8bB 94
7C 8bC 96
7D 8bD 83
7E 8bE 99
7C 8cC 84
Acknowledgment. This work was supported by the
CREST program, sponsored by the JST. We also thank the
JSPS (Grant-in-Aid for Scientific Research, no. 15205015
and no. 16790025), the MEXT (Scientific Research on
Priority Areas, no. 420), and the Uehara Memorial Founda-
tion for partial financial support of this work. We are thankful
to Dr. Satoru Nakao for his help in measuring SEM, which
is supported by the Nanotechnology Support Project (MEXT)
and managed by the IMS.
92
94
99c
95
96c
7E 8bE >99
7F 8cF
7B 8cB
7C 8cC
91
82
91
a All the reactions were carried out in the presence of 0.05 mol % of
palladium of the catalyst and Na2CO3 (3 mol equiv) in water (1 mmol of
5/2 mL of H2O) at 100 °C for 3 h under atmospheric conditions. 5 or 6/7
) 1.0/1.5. b GC yield, unless otherwise noted. c Isolated yield.10
Supporting Information Available: Experimental pro-
1
cedures and characterization data, including H NMR, 13C
NMR, 31P NMR, and GC-MS spectra of ligand 4, complex
A, and the Suzuki-Miyaura coupling products. This material
is available free of charge via the Internet at http://pubs.acs.org.
In conclusion, a novel 3D coordination metal-network
complex A of the PdCl2 connector with a C3-trisphosphine
OL0615026
4262
Org. Lett., Vol. 8, No. 19, 2006