PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
5
carbon-carbon double bonds (Table 2, entry 1–5) were com- 4.2. Instruments
monly over 99%, and it implies that the catalyst is efficient
toward hydrosilylation reactions. According to the results in
Table 2 (entries 6–10), when other functional groups were
introduced into olefins, moderate to excellent conversion%
could still be achieved. Specifically, when styrene was used
as the substrate, the conversion% could reach 99%, which
NMR spectra of the hydrosilylation adducts were recorded
1
3
using a Bruker 400 MHz spectrometer. Solid-state C spec-
tra were recorded using a Bruker 600 MHz spectrometer.
Fourier-transform infrared spectra were recorded with a
Nicolet 6700 spectrophotometer. A Thermo Scientific K-
Alpha instrument was used to record the X-ray photoelec-
tron spectra (XPS) of the catalyst. Scanning electron micros-
copy (SEM) and energy dispersive spectroscopy (EDS) data
were collected with a Hitachi SU8010 system that was
equipped with a HORIBA EMAX ENERGY module.
[
41]
was much better than most catalysts in the literature.
However, the selectivity was mediocre, as the b-/a- adduct
1
ratio was ꢁ 7:3, according to the H NMR data. As can be
seen in Table 2 (entry 8 and 9), the conversion% of sub-
strates bearing unconjugated aryl group and the C¼C dou-
ble bond decreased slightly, indicating that a conjugated p
Meanwhile, N adsorption/desorption experiments were con-
2
ducted using a Micromeritics TriStar II 3flex Surface Area
and Porosity Instrument. TEM images were obtained with a
JEM-2100F system. The exact platinum content in the cata-
lyst was analyzed with an ICP spectrometer HK-9600. The
system favors the hydrosilylation mediated by SiO -Py-Pt.
2
Finally, it seemed that hetero atoms at the c-C certainly
have an effect on the hydrosilylation process, as the substitu-
tion of OH group showed no negative influence (Table 2
entry 7 and 10) while the introduction of chlorine totally
blocked the process of hydrosilylation reaction.
1
Supplemental Materials contains sample H NMR spectra of
the products.
Finally, the recyclability of SiO -Py-Pt was also examined.
2
4
.3. Preparation of SiO -Py-Pt
2
As shown in Figure S5 (Supplemental Materials), the catalyst
can be used for five consecutive runs with few losses in
activity. This may be due to low leaching of platinum during
the recycling tests, as there was still 3.11% of platinum
remaining in the catalyst after 5 runs.
c-aminopropyl triethoxysilane (2.21 g) was added into a dis-
persion containing silica gel (3.02 g) and anhydrous ethanol
(100 mL), and the mixture was stirred under refluxing for
8
h. Later, anhydrous ethanol solution (10 mL) containing
pyridine-2,6-diformaldehyde (0.661 g) was then added drop-
wise into the mixture, and the mixture was magnetically
stirred for 6 h until the completion of the reaction. Then the
resulting solution was filtrated and washed with ethanol.
3
. Conclusion
ꢃ
The solid was dried under vacuum at 50 C for 6 h, giving
In conclusion, we have prepared a low-cost novel heteroge-
neous platinum catalyst which is based on pyridine bis-
imine Schiff base modified silica gel through a simple
procedure. The resulting catalyst can efficiently mediate
hydrosilylation reactions between hydrosilanes and olefins
with various structure features. Furthermore, it can be
reused for at least five cycles without loss in activity. Further
study on its application in batch reactions is underway and
its potential in real industry usage is under evaluation.
pale pink power (3.25 g). Next, the pale pink powder
(0.711 g) was dispersed in 50 mL anhydrous ethanol, and
Pt(COD)Cl (0.212 g) was added under stirring. The reaction
2
proceeded for 10 h under refluxing, and then the mixture
was filtrated after cooling down to room temperature. The
solid was washed with ethanol 3 times and dried under vac-
ꢃ
uum at 50 C for 6 h, giving SiO -Py-Pt (0.782 g).
2
4
.4. Hydrosilylation reactions
The catalytic activity of SiO -Py-Pt was evaluated based on
2
its ability to catalyze a model hydrosilylation reaction
between 1-octene and triethoxylsilane. The reaction was per-
formed in a 25 mL round-bottom flask with a magnetic stir-
4
. Experimental
4.1. Reagents and chemicals
rer. Most commonly, 1-octene (780 mL, 5.00 mmol) and
All of the reagents which were used in this research were of
analytical grade or better, unless stated otherwise. Styrene,
triethoxy(vinyl)silane, 1-octadecene, 1-cyclohexene, allylben-
zene, allyl phenyl ether, methyl dimethoxy vinyl silane,
methyl diethoxy vinyl silane, methallyl alcohol, oct-1-en-3-
ol, c-aminopropyl triethoxysilane, triethoxysilane, Silica gel
and pyridine-2,6-diformaldehyde were purchased from
Aladdin Industrial Corporation (Shanghai, China). Ethanol
ꢃ
SiO -Py-Pt were added into the flask and stirred at 90 C for
2
0
.5 h, and then triethoxylsilane (925 mL, 5.00 mmol) was
added and the mixture was subsequently stirred for 2–6 h.
1
The resulting mixture was analyzed via H NMR spectros-
1
copy without further purification. H NMR of triethoxy
octyl silane d (CDCl3, ppm): 0.54 (2H), 0.80 (3H), 1.17
(18H), 1.32 (2H), 3.73 (6H).
The recyclability of SiO -Py-Pt was evaluated in terms of
2
was purchased from Tianjin Fuyu Fine Chemical Co., Ltd. the conversion performance obtained after repeated use for
Tianjin, China). Lastly, CD OD and chloroform-d (CDCl ) several cycles. Briefly, the catalyst (30.5 mg) was suspended
(
3
3
with TMS as an internal standard were purchased from J & in 1-octene (0.780 mL, 5.0 mmol) and then the mixture was
ꢃ
K Co., Ltd. (Beijing, China).
preheated at 90 C for 30 min, and then triethoxylsilane