D. Yuan, H. Zhang / Applied Catalysis A: General 475 (2014) 249–255
251
O
over Na2SO4, and evaporated. The crude products obtained were
purified by flash chromatography with n-hexane/EtOAc as the elu-
ent affording the corresponding products. All products were known
compounds and were identified by comparison of their physical and
spectra data with those of authentic samples.
H
N
H
H
Water
8h 80
O
+
N
N
O
H
H
Fe O / P (GMA-AA-MMA)
3
4
O
H
N
The recycling test for the Suzuki coupling was carried out as fol-
lows. For each run, a mixture of 4-bromobenzeonitrile (1.0 mmol),
phenylboronic acid (1.5 mmol), K CO3 (2.0 mmol), Fe O /P(GMA-
Pd (OAc)2
H
H
O
N
H
N
Ethanol 24h rt
2
3
4
OH
AA-MMA)–Pd(0) (0.2 mol% with respect to 4-bromobenzeonitrile)
◦
and EtOH/H O (1:1) (5 ml) were stirred at 80 C under air atmo-
O
2
H
N
H
H
sphere. After the reaction mixture was cooled to room temperature,
water (10.0 ml) and ether (20.0 ml) were added. The catalyst was
magnetically separated and used for the next cycle without further
treatment. The fresh solvent and substrates were added, but the
molar ratio of substrate to Pd remained the same as that in the first
run.
O
N
N
Pd
H
OH
Fe O / P (GMA-AA-MMA) - Pd
3
4
Scheme 2. Synthesis of Fe3O4/P(GMA-AA-MMA)–Pd.
2.6. Characterization
2
.3. Amination of Fe O /P(GMA-MMA-AA) microspheres
3 4
The X-ray diffraction (XRD) patterns were collected on a Bruker
To
a round bottom flask, Fe O /P(GMA-MMA-AA) (2.0 g)
3 4
D8 ADVANCE instrument using Cu K␣ radiation (ꢀ = 1.5418 A)
at 40 kV and 40 mA. The elemental contents of palladium in
the supported catalyst were determined by Z-8000 atomic
absorbance spectroscopy (AAS). The microscopic morphologies
of Fe O /P(GMA-MMA-AA) and Fe O /P(GMA-MMA-A)–Pd were
˚
was added to the solution of diethylenetriamine (10.0 g) in
water (100.0 g). The mixture was warmed to 75 C and stirred
in the air for 8 h. Then cooled to room temperature, the
amino-functionalized microspheres were separated in an exter-
nal magnetic field, washed with plenty of ethanol, acetone
◦
3
4
3
4
observed in a transmission Electron Microscope (TEM, JEOL JEM-
010). X-ray photoelectron spectra (XPS) were recorded on a kratos
◦
and water, dried at 45 C under vacuum for 24 h, got yellow
3
Fe O /P(GMA-MMA-AA) supported diethylenetriamine (abbrevi-
3
4
Axis Ultra DLD, and the C1s line at 284.8 eV was used as a reference.
Magnetic measurements were investigated with a Quantum Design
vibrating sample magnetometer (VSM) at room temperature in an
applied magnetic field sweeping from −15 to 15 kOe. A Netzsch
Thermoanalyzer STA 409 was used for thermogravimetric analysis
ated as Fe O /P(GMA-MMA-AA)–NH ). The amino group content
on the surface of Fe O /P(GMA-MMA-AA) was 2.50 mmol g using
volumetric method [29].
3
4
2
−
1
3
4
2
.4. Preparation of Fe O /P(GMA-MMA-AA)–Pd
◦
3
4
(TGA) with a heating rate of 10 C/min in air.
Fe O /P(GMA-MMA-AA)–NH (2 g) was added to the solution
3
4
2
3. Results and discussion
of Pd(OAc)2 (0.1 g) in ethanol (100 ml). The mixture was stirred at
room temperature in the air for 24 h. Then the reaction mixture was
separated by an external magnetic field and washed with ethanol
3.1. Synthesis and characterization of
Fe O /P(GMA-MMA-AA)–Pd
3
4
(
3 × 50 ml) and H O (3 × 50 ml), respectively, until no palladium
2
in the filtrate could be detected by atomic absorption spectroscopy
In the present work, superparamagnetic polymer composite
◦
(
AAS). Then the separated product was dried under vacuum at 45 C
microspheres were synthesized by an emulsifier free emulsion
polymerization using 1,1-diphenylethylene (DPE) as free radi-
cal control agent (Scheme 1). As shown in Scheme 1, the DPE
method used to prepare superparamagnetic polymer composite
microspheres included a two-step procedure. Firstly, acrylic acid
for 24 h to give black magnetic composite microspheres supported
palladium complex (abbreviated as Fe O /P(GMA-AA-MMA)–Pd)
3
4
(
Scheme 2). The palladium content in Fe O /P(GMA-AA-MMA)–Pd
3 4
catalyst was determined to be 5.0 wt% by AAS.
(AA), methyl methacrylate (MMA) and 1,1-diphenylethylene (DPE)
2
.5. Typical procedure used to separate and purified the
chosen as monomers were added into the reactor to form DPE-
containing precursor polymer P(AA-MMA) 1. Secondly, Due to
the amphiphilic property of the DPE-containing precursor, it not
corresponding compounds for Suzuki reaction
The novel magnetic supported catalyst (0.2 mol%), aryl halides
only was absorbed on the surface of Fe O4 nanoparticles to stabi-
3
(
1.0 mmol), phenylboronic acid (1.5 mmol), K CO3 (2.0 mmol) and
lize Fe O4 nanoparticles consequently, but also initiated the third
2
3
EtOH/H O (1:1) (5 ml) were added into a round bottomed flask
and stirred at 80 C under air atmosphere for 2–12 h (Scheme 3).
monomer to polymerize on the surface of the Fe O4 nanoparti-
2
3
◦
cles. Fe O /P(GMA-AA-MMA)) with high saturation magnetization
3
4
After the reaction mixture was cooled to room temperature, water
value then formed, consequently, resulting in the supported
catalyst with high saturation magnetization value. In order to
confirm whether Fe O /P(GMA-AA-MMA)) with high saturation
(
10.0 ml) and ether (20.0 ml) were added. The catalyst was mag-
netically separated and used for the next cycle without further
treatment. The organic phase of the filtrate was separated, dried
3
4
magnetization value was obtanied, TEM, XRD and VSM methods
K CO , H O/EtOH
2
3
2
X
B(OH)2
+
Fe O / P (GMA-AA-MMA) - Pd
3
4
R1
R2
R1
R2
X=Br, Cl
Scheme 3. Suzuki reaction catalyzed by the magnetic catalyst.