Surfactant-Encapsulated Polyoxometalate Catalysts
FULL PAPER
dissolved in water and the pH of the solution was adjusted to 9.0 using
Na2CO3. The solution was extracted with CHCl3 (3ꢁ50 mL), and the or-
ganic layers were combined, dried (MgSO4), and concentrated. The re-
sulting white pure product was dimethyl(11-hydroxydecyl)amine (0.78 g,
90%). 1H NMR (500 MHz, CDCl3, 258C, TMS): d=1.28 (m, 14H), 1.47
(m, 2H), 1.56 (m, 2H), 2.25 (s, 6H), 2.28 (t, 2H), 3.64 ppm (t, 2H). A
portion of the resulting dimethyl(11-hydroxydecyl)amine (1.0 g,
about 100–200 mm in diameter was then added. The mol ratio of cyclo-
hexene, H2O2, and polyoxometalate was kept at 1:1:0.001, which was cal-
culated on the basis of the loading values of SEP-1 in the hybrid catalyst.
The reaction mixture was stirred at 300 rpm at 258C and the progress of
the reaction was monitored by TLC and 1H NMR. When the reaction
was complete (120 min in this case), the solid hybrid catalyst was filtered
off, washed with acetonitrile, and recovered.
4.64 mmol) and BrACHTUNGTRENNUNG(CH2)11OH (1.44 g, 5.73 mmol) were dissolved in etha-
Reaction procedure for the catalytic oxidation of cyclohexanol: Cyclo-
hexanol (0.1 g) and 30% H2O2 (0.11 g) were dissolved in acetonitrile
(10 mL) in a round-bottomed flask. SHC-1 (0.013 g) that had been tritu-
rated to about 100–200 mm in diameter was then added. The initial mol
ratio of cyclohexanol, H2O2, and polyoxometalate was kept at 1:1:0.001
based on the loading value of SEP-1 in the hybrid catalyst. The reaction
mixture was stirred at 300 rpm at 408C and the progress of the reaction
was monitored by TLC and 1H NMR. When the reaction was complete
(300 min in this case), the solid hybrid catalyst was filtered off, washed
with acetonitrile, and recovered.
nol (50 mL) and the solution was heated at reflux with stirring for 48 h.
After cooling to room temperature, the mixture was concentrated to 3–
5 mL by removing excess solvent under reduced pressure. Cold diethyl
ether (30 mL) was then added to the residue. The white precipitate
formed was collected by filtration and washed several times with cold di-
ethyl ether to give white pure DOHDA (1.84 g, 85%). 1H NMR
(500 MHz, [D6]DMSO, 258C, TMS): d=1.24 (m, 28H), 1.38 (m, 4H),
1.61 (m, 4H), 2.96 (s, 6H), 3.19 (m, 4H), 3.35 (m, 4H), 4.29 ppm (t, 2H).
Preparation of SEPs: SEP-1 was prepared as follows. An aqueous solu-
tion of POM-1 (3 molLꢀ1, 20 mL, 0.06 mol) was added to an aqueous so-
lution of DOHDA (6 molLꢀ1, 30 mL, 0.18 mol). After stirring for 30 min,
the precipitate formed was collected by filtration and washed several
times with deionized water. It was dried in vacuo for 5 h to give white
pure SEP-1. The preparation of surfactant DOHDA encapsulated POM-
2 (designated as SEP-2) was similar to that of SEP-1, except that the mol
ratio of surfactant to POM-2 was adjusted to 12:1 for charge balance.
Characterization of catalytic activity: Aliquots (1 mL) of the reaction
mixture were withdrawn and filtered at certain times. The filtrates were
carefully collected and concentrated to dryness. The compositions and
contents of the mixtures were determined by IR, NMR, MS, and HPLC.
The HPLC analysis was performed on an Agilent 1100 system with a
ZORBAX Eclipse XDB-C8 column (d=5 mm, l=150 mm). The eluent
was acetonitrile/H2O (90:10), and a diode-array multiple-wavelength de-
tector was used.
Preparation of SHCs: SHC-1 was prepared as follows. As a typical proce-
dure, SEP-1 (0.1 g) was dissolved in a mixture of ethanol (1 mL) and
water (0.33 mL). The solution was stirred vigorously, and then TEOS
(0.9 g) was added. When the mixture was visibly homogeneous, the stir-
ring was stopped and the resulting sol-gel was aged for two weeks. A
transparent gel hybrid catalyst was obtained, which was ready for further
structural measurement and subsequent catalytic oxidation of sulfide
after drying in vacuo for 1 day. Supramolecular hybrid catalyst containing
SEP-2 (SHC-2) was prepared according to the same procedure.
Other fundamental characterization data of all of the samples and details
of the monitoring the catalytic reactions can be found in the Supporting
Information.
Acknowledgements
Characterization of SHCs: The compositions of the surfactant DOHDA,
SEP-1, SEP-2, SHC-1, and SHC-2 were determined by 1H NMR, FTIR,
EA, inductively coupled plasma atomic emission spectroscopy
(ICPAES), and thermal gravimetric analysis (TGA) measurements.
1H NMR spectra were recorded on a Bruker Ultra-Shield TM 500 MHz
spectrometer using tetramethylsilane (TMS) as a standard. FTIR spectra
were collected on a Bruker IFS66V FTIR spectrometer equipped with a
deuterated triglycine sulfate detector (32 scans). The spectra were record-
ed with a resolution of 4 cmꢀ1. The organic element content was mea-
sured by EA, which was carried out on a Flash EA1112 from Thermo-
Quest Italia S.p.A. The inorganic element content was determined by
ICPAES. TGA was carried out on a Perkin–Elmer 7 series thermal analy-
sis system. The hydrophobicity of SHC-1 was assessed by measurements
of static water contact angle, which were performed at room temperature
using a drop-shape analysis system (DSA 10MK2 KRUSS).
The authors acknowledge financial support from the National Basic Re-
search Program (2007CB808003), the National Natural Science Founda-
tion of China (20703019, 20731160002, 20973082, 20921003), the 111 proj-
ect (B06009) for the supporting of fruitful discussion with Prof. I. Kim at
the Pusan National University of Korea, and the Open Project of the
State Key Laboratory of Polymer Physics and Chemistry, Chinese Acade-
my of Sciences. The authors also appreciate the kind help from Engineer
Y. C. Zou at the State Key Laboratory of Inorganic Synthesis and Prepa-
rative Chemistry for the measurement and analysis of standard nitrogen-
sorption isotherms of the catalyst.
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Reaction procedure for the catalytic oxidation of sulfides: The catalytic
oxidation of sulfides to sulfones was typically performed as follows.
Taking the oxidation of DBT as an example: DBT (0.1 g) and 30% H2O2
(0.15 g) were dissolved in acetonitrile (100 mL) in a round-bottomed
flask. SHC-1 (0.020 g) that had been triturated to about 100–200 mm in
diameter was then added. The mol ratio of DBT, H2O2, and polyoxo-
metalate was 1:2.5:0.0025, which was calculated on the basis of the load-
ing values of SEP-1 in the hybrid catalyst. The reaction mixture was
stirred at 300 rpm at 408C and the progress of the reaction was moni-
tored by TLC and HPLC. When the reaction was complete (42 min in
this case), the solid hybrid catalyst was filtered off, washed with acetoni-
trile, and recovered. The procedure for the catalytic oxidation of sulfide
to sulfoxide was similar to that described above, but the mol ratio of
DBT, H2O2, and polyoxometalate was adjusted to 1:1:0.001.
The same methodology was followed in other solvents, for catalytic oxi-
dations of different sulfides, or with SHC-2, except that the amounts of
the oxidant H2O2 and the catalyst were varied.
Reaction procedure for the catalytic oxidation of cyclohexene: Cyclohex-
ene (0.1 g) and 30% H2O2 (0.14 g) were dissolved in acetonitrile (10 mL)
in a round-bottomed flask. SHC-1 (0.016 g) that had been triturated to
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Chem. Eur. J. 2010, 16, 1068 – 1078
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