Immobilized copper catalyst for atom transfer radical addition and polymerization

Article abstract of DOI:10.1002/aoc.1739

A novel multidentate amine grafted on silica gel and magnetic microsphere was prepared. Its chemical structure was confirmed by C¹³ NMR, XPS and FTIR, and the nitrogen content was determined by elemental analysis. It was also used as a ligand f

Full text of DOI:10.1002/aoc.1739

Full Paper
Received: 17 May 2010
Revised: 10 September 2010
Accepted: 10 September 2010
Published online in Wiley Online Library: 23 November 2010
(wileyonlinelibrary.com) DOI 10.1002/aoc.1739
Immobilized copper catalyst for atom transfer
radical addition and polymerization
Lin Wanga,b, Xinhua Yana, Zhifeng Fua, Yun Daib and Yan Shia∗
A novel multidentate amine grafted on silica gel and magnetic microsphere was prepared. Its chemical structure was confirmed
by C13 NMR, XPS and FTIR, and the nitrogen content was determined by elemental analysis. It was also used as a ligand for
CuCl and successfully catalyzed the atom transfer radical addition of both carbon tetrachloride (CCl4) to methyl methacrylate
and methyl trichloroacetate to styrene, repeatedly. The conversion and purity of the product were determined through gas
chromatography and 1H NMR, respectively. The immobilized copper catalyst complex was also used in atom transfer radical
polymerization of styrene initiated by 1,1,1,3-tetrachloro-3-phenylpropane and methyl methacrylate initiated by methyl 2-
methyl-2,4,4,4-tetrachlorobutyrate, respectively. Although the polymerization took place successfully, it did not proceed in a
c
controlled fashion. Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Keywords: ATRA; ATRP; copper catalysts; immobilization
Introduction
was achieved with a predetermined molecular weight and narrow
molecular weight distribution (Mw/Mn 1.1–1.3) in the ATRP of
MMA and MA.
In recent years, transition-metal-catalyzed Kharasch addition re-
action (atom transfer radical addition, ATRA) has been extensively
investigated, especially since ATRA was successfully extended to
a controlled radical polymerization, atom transfer radical poly-
merization (ATRP), in 1995.[1,2] A wide range of metal catalysts
have been reported in ATRA, such as copper,[3,4] nickel,[5] iron[6,7]
and ruthenium[8–10] complexes. Verpoort et al.[11] reported an
immobilized multifunctional Schiff bases containing ruthenium
complexes on MCM-41 and used them for ATRA. Compared with
the homogeneous catalysts, the use of heterogeneous catalysts
offers several advantages such as simplification of reaction proce-
dures,easyseparationofproducts,repeateduseandthepossibility
of designing continuous flow processes.[12–15] Recently, Clark
et al.[16] used solid-supported copper catalyst for atom transfer
radical cyclizations. Solid-supported copper catalysts for ATRP
were also reported. Haddleton and co-workers showed that ATRP
of methyl methacrylate (MMA) and styrene (St) were feasible by
supporting cuprous bromide (CuBr) using a Schiff base ligand
to amino-functionalized silica gel and crosslinked polystyrene.[17]
However, the polymerizations by these catalysts showed poor
living characteristics. The molecular weights were significantly
higher than those predicted, and the polydispersities were high.
Matyjaszewski et al.[18] reported the use of surface-modified silica
gel particles with immobilized multidentate amine donor lig-
ands for copper-mediated ATRP, but the catalyst immobilized
by multidentate amine-functionalized silica gel did not mediate
a living polymerization of MMA, methyl acrylate (MA) and St.
Zhu et al.[19] investigated the spacer effect by using silica gels
grafted with tetraethyldiethylenetriamine or di(2-picolyl)amine
via poly(ethylene glycol) spacers of different lengths for MMA
polymerizations. In the recent literature[20–22] there are also some
examples of successful immobilization of catalysts that maintain
their activity on a solid support. Matyjaszewski et al.[23] reported a
new two-component catalyst system consisting of an immobilized
catalyst and a soluble catalyst in ppm quantities and applied this
system in ATRP successfully. A high monomer conversion (>90%)
In this study, we first prepared a novel multidentate amine-
modified silica gel, then used it as a ligand for CuCl in ATRA
of CCl4 with MMA and methyl trichloroacetate (MTCA) with St,
and finally used it in ATRP of St initiated by 1,1,1,3-tetrachloro-
3-phenylpropane (TCPP) and MMA initiated by methyl 2-methyl-
2,4,4,4-tetrachlorobutyrate (MMTCB).
We also prepared a multidentate amine-modified magnetic
microsphere and evaluated its efficiency as a ligand for CuCl
in ATRA and ATRP. Multidentate amine-modified magnetic
microspheres not only had the same advantages as multidentate
amine-modified silica gel, but also could be separated very fast
and easily by the use of a magnet.
Experimental
Materials
γ -Aminopropyl trimethoxy silane (γ -APS, Zhangjiagang Guotai-
Huarong Chemical New Materials Co.) and trihydroxymethyl
propyl triacrylate (TMPTA, Tianjinshi Tianjiao Chemical Co.) were
used without further purification. St (Polymerization grade,
Yanshan Petrochemical Co.), MMA (99%, Beijing Chemical Reagent
Company) and butyl acrylate (BA, Analytical grade, Beijing
Chemical Plant) were dried over anhydrous MgSO4, then distilled
under reduced pressure, and stored at −15 ◦C in a freezer.
∗
Correspondence to: Yan Shi, State Key Laboratory of Chemical Resource
Engineering, Beijing University of Chemical Technology, Hepingxiqiao, Beijing
100029, People’s Republic of China. E-mail: shiyan@mail.buct.edu.cn
a
State Key Laboratory of Chemical Resource Engineering, Beijing University of
ChemicalTechnology,Hepingxiqiao,Beijing100029,People’sRepublicofChina
b
School of Chemistry andBiotechnology, Yunnan NationalitiesUniversity, street
121, Kunming 650031, People’s Republic of China
c
Appl. Organometal. Chem. 2011, 25, 190–197
Copyright ꢀ 2010 John Wiley & Sons, Ltd.

Immobilized copper catalyst
O
Diethylenetriamine (DETA) was obtained from Beijing Chemical
Reagent Company. TCPP and MMTCB were synthesized in our
laboratory. Toluene and tetrahydrofuran (THF) were redistilled
under normal pressure before use. Silica gel (chromatographic
grade, Qingdao Haiyang Chemical Plant) was treated with nitric
acid (HNO3 : H2O = 1 : 1) at refluxing temperature for 3 h, 18%
hydrochloric acid at room temperature for 6 h, and then calcined
in a muffle at 200 ◦C for 10 h, finally being dried in vacuum at
110 ◦C for 48 h before use. All other chemicals were analytical
reagents and were used as received. All water was doubly distilled.
O
C
O
O
O
O
OH
OH
OH
HO
HO
APS
TMPTA
O
Si
NH2
Si
N
OH
O
H2N
O
O
NH2
C
N
O
O
NH2
Preparation of Multidentate Amine-modified Silica Gel
C
A
O
T
E
O
O
N
N
Si
D
Multidentate amine-modified silica gel was synthesized through
the following steps as shown in Scheme 1. Firstly, the introduction
of amino groups onto the silica surface was achieved by treating
the surface silanol groups with γ -APS. A suspension of 50.0 g of
silicageland50 mlofγ -APSwasstirredat70◦Cin150 mloftoluene
solution for 6 h. The product was then filtered and transferred to
a Soxhlet extraction apparatus for refluxing extraction in toluene
and methanol for 10 h, respectively. The product was dried under
vacuum at 50 ◦C over 48 h. Secondly, a mixture of 35 g of γ -APS-
modified silica gel (52 mmol amino groups) and 46.2g (156 mmol)
of TMPTA was added to a 500 ml flask with 250 ml of methanol as
solvent. The mixture was stirred at 25 ◦C for 4 days in order to react
sufficiently. The solid product was then filtered and transferred to
a Soxhlet extraction apparatus for refluxing extraction in methanol
and tetrahydrofuran for 24 h. After extracting, it was dried under
vacuum at 50 ◦C over 48 h, and TMPTA-modified silica gel was
obtained. Thirdly, a suspension of 30.0 g of TMPTA-modified silica
gel (about 90 mmol of double bonds) and 27.8 g (270 mmol) of
DETA was stirred at 25 ◦C in a flask with 250 ml of methanol as
solvent for 4 days. The obtained DETA-modified silica gel was
purified in the same way as γ -APS-modified silica gel. Finally,
30.0 g of DETA-modified silica gels (about 360.0 mmol of amino
groups) was treated with 83.2 g (720 mmol) of BA in 250 ml of
methanol for 6 days at 25 ◦C, and multidentate amine-modified
silica gel was obtained. It was also purified in the same way as
γ -APS-modified silica gel. All the above reactions were carried out
under nitrogen atmosphere.
NH2
NH2
N
O
O
NH2
C
O
O
BA
N
NH2
H2N
o
o
o
N
o
O
O
N
O
N
O
O
C
O
O
o
o
Si
O
O
O
O
N
O
O
O
N
O
O
N
O
N
O
N
O
O
O
N
O
O
O
C
O
O
N
O
O
Preparation Fe3O4 Ferrofluid and its Surface Modification
O
O
O
N
O
O
A 150 ml aliquot of FeCl3· 6H2O aqueous solution (0.5 M) and 75 ml
of FeSO4 aqueous solution (0.5 M) were put into a 250 ml four-
necked flask equipped with a stirrer, a condenser, a thermometer
andanN2 inlet.A20 mlaliquotof25%NH3·H2Osolutionwasadded
under stirring at 30 ◦C until pH reached 9.0, and the reaction was
allowed to proceed for 30 min. The resulting colloidal particles
were washed with water until neutrality was achieved. Finally, the
magnetite content was adjusted to 10% (w/v) using the mixture
of ethanol and water (volume ratio 1 : 5). The dispersed Fe3O4 was
stirred at 60 ◦C under an atmosphere of N2 and 3.0 ml of oleic
acid was added dropwise. The temperature was raised to 85 ◦C,
and the reaction was allowed to proceed for 30 min and then was
cooled. Finally, 1.0 g of sodium dodecyl sulfonate (SAS) was added
and stirred for 30 min and obtained the magnetic fluid with good
dispersivity and stability.
N
N
O
O
O
O
O
Scheme 1. The synthetic route of immobilized multidentate amine ligand
on silica gel.
stirrer, a condenser, a thermometer and an N2 inlet. After pre-
emulsion treatment by sonicating for 30 min, the temperature
was raised to 70 ◦C, and a mixture of 8 ml of MMA and 0.8 ml
of TMPTA was added dropwise in 30 min. The polymerization
was allowed to proceed for 8 h. The obtained brown magnetic
polymer microspheres were collected by putting a magnet under
a beaker bottom, then washed with deionized water and ethanol
repeatedly, and finally dried under vacuum at 50 ◦C.
A 10 ml aliquot of dispersed Fe3O4 obtained above 0.1 g of
SAS, 0.04 g of potassium persulfate, 2 ml of MMA, 0.2 ml of TMPTA
and 140 ml of mixed solvent of ethanol and water (volume ratio
1 : 5) was added to a 250 ml four-necked flask equipped with a
c
Appl. Organometal. Chem. 2011, 25, 190–197
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
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L. Wang et al.
O
O
O
O
O
DETA
NH2
Fe
O
4
3
N
NH2
O
N
O
O
BA
O
N
O
Figure 1. FTIR spectra of silica gel and modified silica gel obtained at
different steps. (a) Silica gel; (b) γ -APS-modified silica gel; (c) TMPTA-
modified silica gel; (d) DETA-modified silica gel; (e) multidentate amine-
modified silica gel.
N
O
O
O
O
of xylene were added to a 100 ml dried round-bottom flask
equipped with a magnetic stirrer. After the flask was sealed with
a rubber septum, it was degassed by three freeze–pump–thaw
cycles and subsequently purged under argon atmosphere, and
then immersed in an oil bath thermostated at 110 ◦C. At definite
time intervals, portions of the sample were withdrawn from the
flask using argon-filled gas-tight syringes to determine monomer
conversions and molecular weights.
Scheme 2. The preparation route of immobilized multidentate amine
ligand on magnetic microspheres.
Preparation of Multidentate Amine-modified Magnetic
Microspheres
Multidentate amine-modified magnetic microspheres were pre-
pared through the following steps, as shown in Scheme 2. Firstly,
a suspension of 2.0 g of magnetic microspheres with the double
bonds on the surface obtained above and excess DETA was stirred
at 25 ◦C for 4 days with 250 ml of methanol as solvent. DETA-
modified magnetic microspheres with the amino groups on the
surface were collected using a magnet and washed with methanol
repeatedlyandfinallydriedat50 ◦Cundervacuum. Secondly, 2.0 g
of DETA-modified magnetic microspheres reacted with excess BA
in 250 ml of methanol. The mixture was stirred at 25 ◦C for 6 days,
and multidentate amine-modified magnetic microspheres were
collected using a magnet and washed with methanol repeatedly
and finally dried 50 ◦C under vacuum.
Characterization
FTIR spectra were recorded at room temperature on a Nicolet
Nexus-670 spectrometer using KBr tablets. 1H NMR spectra were
recorded on a Bruker AV 600 MHz spectrometer with CDCl3 as
solvent at room temperature. The yields were determined by 1H
NMR spectroscopy. 13C NMR spectra were recorded on a Bruker AV
300 MHz spectrometer. The nitrogen content was measured by an
HP-MOD/106 elemental analysis instrument. Conversion in ATRA
was determined using a GC-7800-A gas chromatograph equipped
with a FID detector and an PEG-20M column (30 m × 0.25 mm).
Results and Discussion
Use of Multidentate Amine-modified Silica Gel or Magnetic
Microspheres as Ligand for CuCl in ATRA
Preparation of Multidentate Amine-modified Silica Gel
Inatypicalexperiment, 30 mmolofMMA, 50 mmolofCCl4, 1 mmol
of CuCl, 0.4 g of multidentate amine-modified silica gel and 30 ml
of toluene were added to a 100 ml dried round-bottom flask
equipped with a magnetic stirrer. After the flask was sealed with
a rubber septum, it was degassed by three freeze–pump–thaw
cycles and subsequently purged under argon atmosphere, and
then immersed in an oil bath thermostated at 85 ◦C. At definite
time intervals, portions of the sample were withdrawn from the
flask using argon-filled gas-tight syringes to determine monomer
conversions by GC and yields by 1H NMR. The final crude product
was distilled at 30 ◦C under reduced pressure to remove toluene
and unreacted CCl4.
The attachment of amino groups onto silica gel was based on the
reaction of silicon alkoxides of γ -APS with silanol groups on the
particle surface. Therefore, the content of silanol groups would
affect the content of amino groups introduced onto the particle
surface. For this purpose, the silica gel was treated with 32% (wt)
nitric acid at refluxing temperature for 3 h, 18% (wt) hydrochloric
acid at room temperature for 6 h, calcined in muffle at 200 ◦C for
10 h, and finally dried in vacuum at 110 ◦C for 48 h before use. The
strong absorption peak appeared at about 3437 cm−1 in Figure 1a
demonstrated that the treatment was successful. Furthermore,
it should be noted that silica gel untreated by nitric acid had
pale yellow color after calcined in muffle, while that treated with
nitric acid had a white color. This phenomenon indicated that
nitric acid not only activated the silanol group, but also removed
the impurities adsorbed on the silica gel surface. The amount of
γ -APS grafted onto silica gel was determined by HP-MOD/106
elemental analysis apparatus. The calculated amount of γ -APS
Use of Multidentate Amine-modified Silica Gel or Magnetic
Microspheres as Ligand for CuCl in ATRP
In a typical experiment, 96 mmol of St, 1 mmol of TCPP, 1 mmol
of CuCl, 0.4 g multidentate amine-modified silica gel and 10 g
c
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Appl. Organometal. Chem. 2011, 25, 190–197

Immobilized copper catalyst
Figure 3. FTIR spectra of unmodified Fe3O4 and modified Fe3O4 obtained
at different steps. (a) Fe3O4; (b) Fe3O4 nanoparticles modified with oleic
acid and sodium dodecyl sulfonate; (c) magnetic microspheres; (d) DETA-
modified magnetic microspheres; (e) multidentate amine-modified mag-
netic microspheres.
1637 cm−1 was ascribed to the characteristic absorption of amino
groups and it was overlapped with the absorption of double
bond of TMPTA. Figure 2(b) is the 13C NMR spectrum of TMPTA-
modified silica gel. The carbon atom of carbonyl group resonated
at 172 ppm, and the carbon atoms of double bond resonated at
105.9 and 128.4 ppm.
The DETA-modified silica gel was obtained by the reaction of
TMPTA-modified silica gel with a great excess of DETA. Figure 2(c)
shows its 13C NMR spectrum. Comparing Fig. 2(b) with the 13C
NMR spectrum of TMPTA-modified silica gel, the resonances at
105.9 and 128.4 ppm due to the two carbon atoms of the double
bond disappeared completely, indicating the formation of DETA-
modified silica gel.
Figure 2. 13C NMRspectra of modified silica gelobtained at different steps.
(A) γ -APS-modified silica gel; (B) TMPTA-modified silica gel; (C) DETA-
modified silica gel; (D) multidentate amine-modified silica gel.
The multidentate amine-modified silica gel was finally obtained
by the reaction of amino groups on the surface of DETA-modified
silica gel with double bond of BA. Figure 2(d) shows its 13C NMR
spectrum. The change in absorption was less compared with
Fig. 2(c). The absorptions of all the carbon atoms overlapped
each other at 5.2–74.3 and at 172 ppm. However, comparing the
relative contents of carbonyl group at 1740 cm−1 with that of
amino groups at 1637 cm−1 from Fig. 1(d,e), it was observed that
the relative proportion of the C O carbonyl group increased. The
nitrogen content of the multidentate amine-modified silica gel
was 1.486 mmol g−1 of silica gel. Comparing the FTIR spectrum
(Fig. 1b) of γ -APS-modified silica gel with that of silica gel (Fig. 1a),
the absorption at 1630 cm−1 shifted to 1637 cm−1, which was the
characteristic absorption of amino groups, and a new absorption
appeared at 2931 cm−1, which was the characteristic absorption
of the asymmetric stretching vibration of CH2 bands. Figure 2(a)
shows the 13C NMR spectrum of γ -APS-modified silica gel. We
can observe that the methylene carbon atom adjacent to Si
atom resonated at 9.8 ppm, the middle methylene carbon atom
resonated in the region of 18.7–22.1 ppm, and the methylene
carbon atom adjacent to amino groups resonated at 42.5 ppm.
The two methyl carbon atoms of the methoxy group resonated at
63.0 ppm. The above results show that γ -APS-modified silica gel
was obtained.
The γ -APS-modified silica gel then reacted with excess TMPTA
via the Michael addition reaction. Figure 1(c) shows the FTIR
spectrum of TMPTA-modified silica gel. The new absorption at
1740 cm−1 was ascribed to the stretching vibration of ester bond.
The absorptions at 2965 and 2931 cm−1 were the characteristic
absorption of the asymmetric stretching vibration of CH3 and CH2
bonds. The absorptions at 1412, 1467 and 1398 cm−1 were the
characteristic absorptions of the bending vibration of CH3 and CH2
bonds, and the absorption at 1412 cm−1 was ascribed to the CH2
bond adjacent to ester group. The stretching vibration of C–O–C
and Si–O–Si was overlapped at 1102 cm−1. The absorption at
was 2.5 mmol g−1
.
Preparation of Multidentate Amine-modified Magnetic
Microspheres
Fe3O4 magnetic nanoparticles were prepared by the classical
chemical co-precipitation procedure. The diameter of Fe3O4
particles was about 15 nm. Figure 3(a) shows the FTIR spectrum
of unmodified Fe3O4 nanoparticles. The characteristic absorption
bandofFe3O4 appearedat585 cm−1.Theabsorptionat3430 cm−1
was ascribed to the characteristic absorption of surface hydroxyl
group of Fe(OH)2 or Fe(OH)3. The absorptions at 1450–1650 cm−1
were the characteristic absorptions of the symmetrical stretching
vibrationofCO32−, whichformedduetothecombinationofFe3O4
and CO2 absorbed from air.
The Fe3O4 magnetic nanoparticles were modified by oleic acid
and sodium dodecyl sulfonate bilayer surfactants. The stability of
the magnetic fluid was very good and could be dispersed well
in polar solvent. Figure 3(b) shows the FTIR spectrum of modified
c
Appl. Organometal. Chem. 2011, 25, 190–197
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L. Wang et al.
Figure 4. XPS of magnetic microspheres and DETA modified magnetic microspheres: (a) C1s core-level spectrum of the magnetic microspheres; (b) O1s
core-level spectrum of the magnetic microspheres; (c) Fe 2p core-level spectrum of the magnetic microspheres; (d) N1s core-level spectrum of the DETA
modified magnetic microspheres.
Fe3O4 nanoparticles with oleic acid and sodium dodecyl sulfonate.
The absorptions at 1710, 1600–1560 and 1420–1300 cm−1 were
the characteristic absorptions of COO−; the absorptions at 3007,
1700–1600 and 970 cm−1 were ascribed to the –C C- bond of
oleicacid.Thecharacteristicabsorptionsofthesulfonicgroupwere
observed at 1203, 1172, 1086 and 1065 cm−1; the absorptions
at 2920, 2851, 1380 and 1465 cm−1 were the characteristic
absorptions of -CH3 and -CH2-; and the characteristic absorptions
band of Fe3O4 appeared at 585 and 3439 cm−1. The above results
showed that modified Fe3O4 was obtained by oleic acid and
sodium dodecyl sulfonate.
energies (BEs) of about 285.04 and 288.7 eV attributable to
the overlapped C–H/C–C/C–O and O C–O species, respec-
tively. The corresponding O1s (at a BE of about 532.23 eV)
core-level spectrum is shown in Fig. 4(b). Fe2p (at a BE of
about 712.23 eV) signals appeared on the magnetic micro-
spheres surfaces. The corresponding Fe2p core-level spectrum
is shown in Fig. 4(c). When the magnetic microspheres were
treated with HCl (1 mmol l−1), the characteristic peak of Fe2p
disappeared, suggesting that the characteristic peak of Fe2p
was caused by incompletely wraped Fe3O4. The above results
showed that magnetic poly(MMA-co-TMPTA) microspheres were
obtained.
Fe3O4 magnetic nanoparticles were covered with polyacrylate
polymer via emulsion copolymerization of MMA and TMPTA in
order to introduce a double bond on the surface. Figure 3(c)
shows the FTIR spectrum of magnetic poly(MMA-co-TMPTA)
microspheres. The strong absorption peak at 1731 cm−1 was
ascribed to the stretching vibration of the carbonyl group. The
absorption at 1636 cm−1 was the characteristic absorption of the
stretching vibration of unreacted double bonds of TMPTA on the
surface, and the absorptions at 1408 and 900–750 cm−1 were the
characteristic absorptions of the bending vibration of unreacted
double bonds. The stretching vibration of C–O–C was at 1268,
1240, 1192, 1150, 1063 and 988 cm−1, and the absorptions at
2993, 2951 and 2856 cm−1 were the characteristic absorptions of
-CH3 and -CH2-. The absorptions at 1450 and 1388 cm−1 were
the characteristic absorptions of the bending vibration of -CH3
and -CH2- bonds. The absorption peak at 3439 cm−1 was the
characteristic absorption of surface hydroxyl group of Fe3O4,
which was not wrapped completely.
The DETA-modified magnetic microspheres were obtained by
reacting double bonds on the surface of magnetic microspheres
with a great excess of DETA via the Michael addition reaction.
Figure 3(d) shows FTIR spectrum of DETA-modified magnetic mi-
crospheres. The absorptions of bending vibration of double bonds
on magnetic microspheres surface at 1408 cm−1 disappeared, and
a new absorption at 1637 cm−1 appeared, which was ascribed to
the characteristic absorption of amino groups of DETA-modified
magnetic microspheres. The absorption peak at 3439 cm−1 was
the overlapped characteristic absorption of amino groups and sur-
face hydroxyl group on Fe3O4 which was not wrapped completely.
Figure 4(d) shows the X-ray photoelectron spectroscopy N1s core-
level spectrum of the magnetic microspheres surfaces. Besides
the characteristic peaks of C1s (C–H/C–C/C–O and O C–O) and
O1s at BE 285.04 and BE 532.23 eV in Fig. 4(a,b), new N1s (at a
BE of about 399.70 eV) signals, a characteristic peak of covalently
bonded nitrogen, appeared on the surface of magnetic micro-
spheres. This shows that DETA-modified magnetic microspheres
were obtained.
Figure 4(a) shows the X-ray photoelectron spectroscopy (XPS)
C1s core-level spectrum of the magnetic microspheres surfaces.
The C1s core-level spectrum of the magnetic microspheres surface
can be curve fitted into two peak components with binding
The multidentate amine-modified magnetic microspheres were
finally obtained by the reaction of amino groups on the surface
c
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Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 190–197

Immobilized copper catalyst
Table 1. Results for ATRA of CCl4 to MMA and MTCA to St catalyzed by CuCl and CuCl/multidentate amine modified silica gel respectively
(a) CCl4 to MMA
Conversion
(b) MTCA to St
Conversion
Run(s)
1
Time (h)
(%)
Yield (%)
(%)
Yield (%)
CuCl/multidentate amine modified silica gel
20
40
60
55
80
87
–
–
77
80
82
–
–
85
81
2
3
4
5
6
7
1
20
40
60
52
62
75
–
–
62
65
68
–
–
73
66
20
40
60
47
55
65
–
–
–
55
58
65
–
–
–
20
40
60
43
51
59
–
–
–
43
50
62
–
–
–
20
40
60
40
46
53
–
–
–
37
40
46
–
–
–
20
40
60
33
42
48
–
–
–
33
37
41
–
–
–
20
40
60
21
29
38
–
–
22
23
25
–
–
35
22
CuCl
20
40
60
0
0
0
0
0
0
0
0
0
0
0
0
Conditions: (a) 30 mmol (3.0 g) of MMA, 50 mmol (7.7 g) of CCl4, 1 mmol (0.0989 g) of CuCl, 0.4 g of multidentate amine modified silica gel and 30 ml of
toluene were added to a 100 ml round-bottom flask equipped with a magnetic stirrer. The reaction was carried out at 85 ◦C under argon atmosphere.
(b) 30 mmol (3.1 g) of St, 40 mmol (7.1 g) of MTCA, 1 mmol (0.0989 g)of CuCl, 0.4 g of multidentate amine modified silica gel and 30 ml of toluene
were added to a 100 ml round-bottom flask equipped with a magnetic stirrer. The reaction was carried out at 80 ◦C under argon atmosphere.
of DETA-modified magnetic microspheres with the double bond
of BA. Figure 3(e) shows FTIR spectrum of BA-modified magnetic
microspheres. The absorption at 1637 cm−1 was ascribed to the
characteristic absorption of unreacted amino groups. By compar-
ing the relative contents of the carbonyl group at 1731 cm−1 with
that of amino groups at 1637 cm−1 from Fig. 3(d,e), we observed
that relative proportion of carbonyl group increased. The nitrogen
content of the multidentate amine-modified magnetic micro-
modified silica gel or magnetic particles were added to the
CuCl, MMA/St, toluene solution, it immediately became blue.
Without stirring, the blue particles quickly settled to the bottom
of the flask, and the upper layer solution became colorless. This
indicated that the multidentate amine-modified silica gel (or
magnetic particles)–CuCl complex was formed. The blue particles
immediately turned green upon adding the initiator and the
solution gradually became a red/brown color throughout the
reaction. Onceagitationwasceased, thesupportedcatalystsettled
to the bottom of the flask, leaving a light red/brown-colored
solution which could be easily separated from the catalyst by
filtration, decanting, etc., in a glovebox.
ATRA of CCl4 to MMA and MTCA to St produced MMTCB and
methyl 2,2,4-trichloro-4-phenylbutyrate (MTCPB), respectively.
From Tables 1 and 2, it can be seen that, when the multidentate
amine immobilized on silica gel as the ligand of CuCl was used
for the first time, the conversion of MMA to MMTCB reached 55%
in 20 h, 80% in 40 h and 87% in 60 h, yielding 53% in 20 h, 78%
in 40 h and 85% in 60 h, respectively. When the multidentate
amine immobilized on magnetic microspheres was used as the
ligand of CuCl for the first time, the conversion of MMA to MMTCB
reached 60% in 20 h, 80% in 40 h and 90% in 60 h, yielding 60%
in 20 h, 79% in 40 h and 89% in 60 h, respectively. In a control
experiment, where no multidentate amine-modified silica gel or
spheres determined by elemental analysis was 1.0 mmol g−1
.
The BA-modified magnetic microspheres were measured using
XPS. Comparing the relative contents of C1s (C–H/C–C/C–O
and O C–O) at BE 285.04 eV and the N1s at 399.7 eV be-
tween DETA-modified magnetic microspheres and BA-modified
magneticmicrospheres,weknowthattherelativeproportionofni-
trogen content of BA-modified magnetic microspheres decreased.
The results show that BA-modified magnetic microspheres were
obtained.
ATRA of CCl4 to MMA and MTCA to St Using Multidentate
Amine-modifiedSilicaGelorMagneticMicrospheresasLigand
for CuCl
The multidentate amines immobilized on silica gel or magnetic
microspheres were used as ligands for CuCl in ATRA of both
CCl4 to MMA and MTCA to St. When multidentate amine-
c
Appl. Organometal. Chem. 2011, 25, 190–197
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

L. Wang et al.
Table 2. Results for ATRA of CCl4 to MMA and MTCA to St catalyzed by CuCl and CuCl/multidentate amine modified magnetic microspheres
respectively
(a) CCl4 to MMA
Conversion
(b) MTCA to St
Conversion
Run(s)
1
Time (h)
(%)
Yield (%)
(%)
Yield (%)
CuCl/multidentate amine modified magnetic microspheres
20
40
60
60
80
90
65
83
92
–
–
89
77
91
2
3
4
5
1
20
40
60
54
65
78
60
67
72
–
–
70
20
40
60
49
57
69
58
60
65
–
–
–
20
40
60
45
51
60
47
53
62
–
–
–
20
40
60
28
35
39
29
35
40
–
–
37
38
CuCl
20
40
60
0
0
0
0
0
0
0
0
0
0
0
0
Conditions: (a) 30 mmol (3.0 g) of MMA, 50 mmol (7.7 g) of CCl4, 1 mmol (0.0989 g) of CuCl, 1 g of multidentate amine modified magnetic microspheres
and 30 ml of toluene were added to a 100 ml round-bottom flask equipped with a magnetic stirrer. The reaction was carried out at 85 ◦C under argon
atmosphere. (b) 30 mmol (3.1 g) of St, 40 mmol (7.1 g) of MTCA, 1 mmol (0.0989 g)of CuCl, 1 g of multidentate amine modified magnetic microspheres
and 30 ml of toluene were added to a 100 ml round-bottom flask equipped with a magnetic stirrer. The reaction was carried out at 80 ◦C under argon
atmosphere.
magnetic microspheres were added to the reaction system, no
MMTCB could be detected in the mixture, even for a long enough
reaction time.
As for the ATRA of MTCA to St, similar results were obtained.
This is also shown in Tables 1 and 2. The reaction filtrates of
MMTCB and MTCPB were diluted in ether. The solutions were
successively washed with a 10 wt% HCl solution, a saturated
solution of sodium carbonate and neutral water. They were then
driedoverMgSO4 andfiltered. Theresidualmonomerandvolatiles
were then evaporated under vacuum. The products were then
purifiedbydistillationandwereisolated.Thechemicalstructuresof
MMTCB [CCl3CH2CCl(CH3)COOCH3] and MTCPB (CCl3CH2CHClPh)
were confirmed by 1H NMR and 13C NMR.
The reuse of the immobilized CuCl catalyst was examined.
After the first reaction, the reactor containing multidentate
amine-modified silica gel/CuCl was transferred into a glovebox
where the catalyst was recovered by filtration and washed with
a large amount of toluene. The reactor contained magnetic
microspheres/CuCl was transferred into a glovebox where the
catalyst was adsorpted by a magnetic separator and the upper
layer solution was decanted and washed with a large amount of
toluene. The catalysts were then dried under vacuum for 12 h and
stored under dry nitrogen for further use. As shown in Tables 1
and 2, the activity of the supported silica gel catalyst remained
about 90% relative to its initial activity in the second use, 85% in
the third use and even 40% in the seventh use. The activity of the
supported magnetic microspheres catalyst also remained about
90% in the second use, 80% in the third use and 30% in the fifth
use. The reduction in catalytic activity may be due to the oxidation
of part of Cu(I) to Cu(II) during the recycling and reaction; this
could be demonstrated by the phenomenon that, with increasing
frequency of reuse, the supported catalyst gradually became
more green. The Cu(II) is produced during the reaction process by
a side reaction of combination or disproportionation between two
radicals, which happens commonly in ATRA. These side reactions
not only decrease the yield in the desired addition products but
1
CCl3CH2CCl(CH3)COOCH3: H NMR (CDCl3, ppm) δ 2.00 (3H, s,
CH3), 3.45 (1H, d, CH2), 3.80 (3H, s), 4.00 (1H, d, CH2). 13C NMR
(CDCl3, ppm) δ 26.2 (1C, CH3), 53.6 (1C, OCH3), 62.2(1C, CH2), 64.6
(1C, CCl), 96.4 (1C, CCl3), 170.0 (1C, CO).
CCl3CH2CHClPh: 1H NMR (CDCl3, ppm) δ 3.10–3.40 (2H, m, CH2),
5.15 (1H, t, CH), 7.20–7.50 (5H, m, phenyl). 13C NMR (CDCl3, ppm)
δ 59.1 (1C, CH), 62.7 (1C, CH2), 97.0 (1C, CCl3), 128.1–141.0 (6C,
phenyl). TheresultshowsthatMMTCBandMTCPBwassynthesized
successfully.
ATRP of MMA was carried out with CuCl supported on
multidentate amine-modified silica gel as catalyst and MMTCB
as initiator. Figure 5 shows GPC traces of polymers obtained at
different monomer conversions. The number average molecular
weights were much higher than those predicted based on the
assumption that one initiator molecule generated one polymer
chain, for instance, at 8% conversion with 1% initiator, a PMMA Mn
of800isexpected,whileanMn of47,000wasmeasuredbyGPC.The
polydispersities (Mw/Mn) were low enough (Mw/Mn < 2). These
results indicated that ATRP of MMA catalyzed by CuCl supported
also induce the accumulation of Cu2+, affecting the Cu+/[Cu2+
]
ratio and finally causing the reduction of the catalytic activity of
the catalysts.[24]
c
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Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 190–197

Immobilized copper catalyst
In conclusion, a novel multidentate amine grafted on silica gel
or magnetic microsphere was prepared successfully. It could be
used as a ligand for CuCl in ATRA of both CCl4 to MMA and MTCA
to St. Furthermore, the immobilized CuCl catalyst could be reused
at least five times with 30% reactivity retained. These immobilized
copper catalysts could also be used in ATRP of St initiated by TCPP
and MMA initiated by MMTCB. Although the polymerization took
place successfully, it did not proceed in a controlled fashion.
Acknowledgments
ThisworkwassupportedbytheProgramforNewCenturyExcellent
Talents in Chinese Universities and Beijing Municipal Education
Commission.
Figure 5. GPC traces of PMMAs obtained at different monomer conver-
sions. Conditions: MMA 100 mmol (10 g), MMTCB 1 mmol (0.254 g), CuCl
1 mmol (0.0989 g), multidentate amine-modified silica gel 0.4 g (1 mmol
nitrogen atom), xylene 30 ml. Temperature 70 ◦C.
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on multidentate amine-modified silica gel did not proceed in a
controlled fashion. This may be due to the mobility of the catalyst
molecules being substantially reduced when they were bound to
the large (relative to small soluble molecules) insoluble particles,
and thus the deactivation reaction may become slower, resulting
in a less controlled ATRP. In a control experiment of ATRP, no
PMMA could be obtained with only CuCl as catalyst, even for a
long enough reaction time.
ATRP of styrene was also carried out with CuCl supported on
multidentate amine-modified silica gel as catalyst and TCPP as
initiator. Similar results, shown in Fig. 6, were obtained.
c
Appl. Organometal. Chem. 2011, 25, 190–197
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
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