DOI: 10.1002/cssc.201100418
Development of Polymeric Palladium-Nanoparticle
Membrane-Installed Microflow Devices and their
Application in Hydrodehalogenation
Yoichi M. A. Yamada,[a] Toshihiro Watanabe,[a, b] Aya Ohno,[a] and Yasuhiro Uozumi*[a, b]
We have developed a variety of polymeric palladium-nanopar-
ticle membrane-installed microflow devices. Three types of
polymers were convoluted with palladium salts under laminar
flow conditions in a microflow reactor to form polymeric palla-
dium membranes at the laminar flow interface. These mem-
branes were reduced with aqueous sodium formate or heat to
create microflow devices that contain polymeric palladium-
nanoparticle membranes. These microflow devices achieved in-
stantaneous hydrodehalogenation of aryl chlorides, bromides,
iodides, and triflates by 10–1000 ppm within a residence time
of 2–8 s at 50–908C by using safe, nonexplosive, aqueous
sodium formate to quantitatively afford the corresponding hy-
drodehalogenated products. Polychlorinated biphenyl (10–
1000 ppm) and polybrominated biphenyl (1000 ppm) were
completely decomposed under similar conditions, yielding bi-
phenyl as a fungicidal compound.
Introduction
The further evolution of polymer-supported transition-metal
nanoparticle catalysts is an important objective for organic
synthetic chemistry and nanochemistry.[1,2] These catalysts are
expected to be highly active and more efficient than metal-
complex catalysts in facilitating reactions, including unantici-
pated reactions not possible with metal-complex catalysts. The
polymer support enables recovery and reuse of the metal
nanoparticles with no contamination of the products and sta-
bilizes the metal nanoparticles against aggregation and deacti-
vation. We previously reported the preparation of polystyrene–
polyethylene glycol resin (PS-PEG)-supported palladium and
platinum nanoparticles, which promoted the aerobic oxidation
of alcohols, hydrodechlorination of aryl chlorides, and hydroge-
nation of alkenes.[3] We also developed a polyviologen-convo-
luted palladium-nanoparticle catalyst for the a-alkylation of ke-
tones with alcohols and the ring-opening alkylation of dike-
tones with alcohols.[4] These reactions did not proceed effi-
ciently with our polymer-supported metal-complex catalysts.
Conversely, microflow reactor systems offer many fundamen-
tal as well as practical advantages and have been developed
as innovative devices for rapid organic transformations.[5] They
are not restricted to the microscale production of chemical
compounds, but sustainably provide closed chemical processes
for producing pharmaceutical and chemical compounds with
safety and continuation.[5g] Molecular transformation with a
catalyst-immobilized microflow reactor is a typical application
of these systems, in which the efficiency of various reactions
increases because of the vast interfacial area and the close dis-
tance of the molecular diffusion path in the narrow space of
the microflow reactor.[6] If a catalyst were installed as a mem-
branous composite at the center of the microchannel, two op-
positely introduced reactants could flow through the divided
channel, while remaining in contact with the vast interfacial
surface of the catalytic membrane from both the front and
back sides, thereby realizing an instantaneous chemical reac-
tion. We reported the formation of a variety of membranous
polymeric palladium complex catalysts inside a microchannel
reactor at the laminar flow interface of the channel by using
our molecular convolution methodology.[4a,7,8] The resulting mi-
croflow devices were applied to the Suzuki–Miyaura reaction
and allylic arylation under microflow conditions, for which the
instantaneous production of coupling compounds was quanti-
tatively achieved within a residence time of 1–5 s in the de-
fined channel region.
We envisaged the possibility of reducing the polymeric pal-
ladium complexes inside a microflow reactor and creating the
first polymeric palladium-nanoparticle membrane-installed mi-
croflow devices. Such devices should promote some organic
transformations that cannot proceed with metal-complex
counterparts, providing instantaneous completion of the reac-
tions. This sequential protocol is schematically depicted in
Figure 1.
Herein, we report the first development of a variety of poly-
meric palladium-nanoparticle membrane-installed microchan-
nel devices and their application in instantaneous, mild, safe,
and nonexplosive hydrodehalogenation. Six different new mi-
[a] Dr. Y. M. A. Yamada, Dr. T. Watanabe, A. Ohno, Prof. Dr. Y. Uozumi
RIKEN Advanced Science Institute
Wako, Saitama 351-0198 (Japan)
Fax: (+81)048-467-9599
[b] Dr. T. Watanabe, Prof. Dr. Y. Uozumi
Institute for Molecular Science
and the Graduate University for Advanced Studies
Okazaki, Aichi 444-8787 (Japan)
Fax: (+81)0564-59-5574
Supporting Information for this article is available on the WWW under
ChemSusChem 2012, 5, 293 – 299
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
293