Paper
NJC
prepared a novel catalyst Fe3O4@PUVS-Pd from readily avail- followed by the addition of 5 mL of ammonium hydroxide
able monomers. This catalyst exhibits high activity for the Heck (25 wt%). Another 1.0 g of undecylenic acid was added into the
and Suzuki reactions in water, and can be used for six runs thus formed suspension in batches (5 ꢁ 0.2 g). The mixture was
without significant loss of catalytic activity. Herein we wish to kept at 80 1C for 30 min, and then allowed to cool to ambient
report this new work in detail.
temperature. After using the mixed solvent of acetone and MeOH
(volume ratio of 1 : 1) to precipitate the suspension, the black
precipitate (Fe3O4@UA) was separated using a permanent magnet
and washed repeatedly with the same mixed solvent, and then
dried under vacuum overnight.
2 Experimental
2.1 Materials
4-Vinyl pyridine (4-VP, Z95%) was purchased from ACROS and
was distilled under vacuum. Acrylic acid (AA, Z99.5%) was
provided by Tianjin Guangfu Fine Chemicals and purified by
vacuum distillation. N,N0-Methylenebisacrylamide (BIS, Z98%)
was purchased from Sinopharm Chemical Reagent Co., Ltd and
used as received. Azodiisobutyronitrile (AIBN, Z99%) was obtained
from Xi’an Chemical Reagent Factory and was purified by recrys-
tallization from ethanol. Palladium(II) chloride (PdCl2, Z59.5%)
was purchased from Shenyang Keda Reagents Company. Unde-
cylenic acid (UA, Z96%) was obtained from Beijing Reagents
Company. Ferric chloride hexahydrate (FeCl3ꢀ6H2O, Z99.5%),
iron chloride tetrahydrate (FeCl2ꢀ4H2O, Z99%) and tetrabutyl
ammonium bromide (TBAB, Z99%) were purchased from
Tianjin Guangfu Fine Chemicals and used as received. Other
reagents were of analytical grade and used as received. Deionized
water was used in the present experiments.
2.4 Synthesis of Fe3O4@PUVS magnetic nanoparticles
Fe3O4@poly(undecylenic acid-co-4-vinyl pyridine-co-sodium
acrylate) (Fe3O4@PUVS) magnetic nanoparticles were synthe-
sized using the following free radical polymerization method:
40 mg of Fe3O4@UA was dispersed in 30 mL of ethanol. After
intense sonication for 30 min, 2.50 mL of sodium acrylate (SAA,
2 mol Lꢂ1), 0.54 mL of 4-VP and 154 mg of BIS were added into
the above mixture. After bubbling with argon gas for 30 min,
the solution was heated to 70 1C under vigorous stirring, and
then 16 mg of AIBN was added into it. The polymerization
process was maintained for 8 hours. The product was collected
by magnetic separation and washed with ethanol five times and
dried under vacuum overnight.
2.5 Preparation of the Fe3O4@PUVS-Pd catalyst
4 mg of Fe3O4@PUVS was dispersed in 2.0 mL of aqueous
solution of PdCl2 (0.05 mM), and the mixture was stirred for
12 hours at room temperature. The Fe3O4@PUVS-Pd catalyst
was isolated by applying a permanent magnet and was washed
with deionized water three times. Then it was directly used as
catalyst without further treatment.
2.2 Characterization
The FT-IR spectra were collected on a NEXUS670 (Nicolet, USA)
spectrophotometer using KBr pellets of samples. TEM micro-
graphs were taken using a Tecnai-G2-F30 (FEI, USA) transmission
electron microscope operating at 300 kV to obtain morphology
and size of the nanoparticles. The palladium contents were
determined by using an AA240 (Varian Corporation, USA) atomic
absorption spectrometer (AAS). The magnetic properties of nano-
particles were recorded on a Model 7304 (Lake Shore, USA)
vibrating sample magnetometer (VSM) at room temperature.
X-ray diffraction (XRD) patterns of the samples were obtained
with a Shimadzu XRD-6000 spectrometer using nickel-filter Cu
Ka radiation (l = 0.15418 nm). X-ray photo-electron spectro-
scopy (XPS) measurements were recorded by using an Axis Ultra
DLD electron spectrometer (Kratos, UK) with contaminated C
as the internal standard (C1s = 284.8 eV). The surface area was
calculated using the Brunauer–Emmett–Teller (BET) method.
The 1H NMR (400 MHz) and 13C NMR (100 MHz) spectra were
obtained in CDCl3 or DMSO-d6 on an AVANCE III 400 NMR spectro-
meter (Bruker, Germany) with TMS as the internal standard.
2.6 General procedure for the Heck reactions in water
A 5 mL screw-capped tube was charged with aryl halides
(1.0 mmol), acrylic acid (1.5 mmol), K2CO3 (3.0 mmol), Fe3O4@
PUSA-Pd catalyst (0.09 mol% Pd based on aryl halide) and
deionized water (2.0 mL). After the mixture was degassed under
argon purge for 10 min, it was stirred vigorously at reflux tempera-
ture for a given time. Then the reaction mixture was cooled to room
temperature, and the catalyst was separated by using a permanent
magnet and washed with deionized water (3 ꢁ 2.0 mL). The
aqueous phase was combined and acidified by the addition of
HCl (1 mol Lꢂ1) to reach a pH of 1–2. The products were filtered
and purified by recrystallization. The obtained products were
1
analyzed by H NMR and 13C NMR.
2.7 General procedure for the Suzuki reactions in water
A 5 mL screw-capped tube was charged with aryl halides
(1.0 mmol), phenylboronic acid (1.5 mmol), K2CO3 (3.0 mmol),
2.3 Synthesis of Fe3O4@UA magnetic nanoparticles
Undecylenic acid-coated magnetic nanoparticles (Fe3O4@UA) Fe3O4@PUVS-Pd catalyst (0.09 mol% Pd) and deionized water
were prepared according to the literature method:23 2.35 g of (2.0 mL). After the mixture was degassed under argon purge for
FeCl3ꢀ6H2O and 0.86 g of FeCl2ꢀ4H2O were dissolved in 40 mL 10 min, it was stirred vigorously at 90 1C for a given time. Then
of deionized water under vigorous stirring. The solution was the reaction mixture was allowed to cool to room temperature.
purged with argon gas for 30 min, and then the temperature The catalyst was separated by using a permanent magnet and the
was raised to 80 1C. A solution of undecylenic acid (0.1 g) in reaction mixture was extracted with ethyl acetate (3 ꢁ 10 mL).
5 mL of acetone was then added into the above solution, The organic phase was dried over MgSO4, filtered, concentrated,
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New J. Chem., 2015, 39, 2052--2059 | 2053