L. Liu et al. / Journal of Organometallic Chemistry 745-746 (2013) 454e459
455
Scheme 1. Synthesis of ethyltriethoxysilane by Rh-catalyzed hydrogenation reaction.
and ferrous chloride tetrahydrate were obtained from Hangzhou
Bond Easy Chemical Co. Ltd. Triethoxysilane was industrial grade
material with mass fraction higher than 0.99, which was purchased
from commercial sources. High purity ethylene gas with mass
fraction higher than 99.99% was obtained from Hangzhou South-
east Gases Co., Ltd. (China). All the chemicals were used directly
without further purification.
beginning of hydrosilylation. The course of each reaction was
monitored by quantitative GC utilizing the procedure above
mentioned. At specified time intervals, 0.5 mL of the reaction mix-
tures were sampled via syringe. When the concentration of ETES
was not increased any more, the reaction was stopped. After cooling
to room temperature, the product was recovered and analyzed. The
synthetic yield, selectivity, and conversion data were calculated on
the basis of GC analysis results.
2.2. Sample analysis
In a typical catalytic run, 0.0417 g (159.5
mmol) RuCl3$3H2O,
0.1442 g (1449.2 mol) CuCl and 382.2 g (2.330 mol) triethox-
m
The structure of each component in hydrosilylation product was
qualitatively characterized on a GCeMS TRANCE DSQ (Thermo
Finnigan, USA) and their contents were determined by means of a
SP6890 gas chromatograph (Shandong Lunan Ruihong Chemical
Instrument, China) equipped with an Agilent HP-5 column
ysilane [HSi(OEt)3] were added into the dried autoclave
mentioned above (Entry 16 in Table 2). The mixture was stirred at
a rate of 300 rpm. When the reaction temperature was raised to
50 ꢀC, ethylene gas at a constant pressure of 0.35 MPa was
continuously fed into the autoclave. After then, 0.5 mL of the re-
(
F
0.32 mm ꢁ 30 m) and an FID detector. The chromatography
action mixtures were sampled periodically and analyzed by GC.
After 6 h, since the concentration of ETES was not increased any
more, the reaction was stopped. The final reaction products were
collected, weighed, and analyzed by GC after cooling to room
temperature. The obtained yield and selectivity were determined
on the basis of the GC analysis with results of 97% and 97%,
respectively.
conditions used were as follows: (1) the initial column temperature
was set to 60 ꢀC and held for 2 min at this temperature, after then, it
was raised to 100 ꢀC at a heating rate of 20 ꢀC minꢂ1, subsequently it
was further raised to 200 ꢀC at a heating rate of 30 ꢀC minꢂ1; (2)
vaporization chamber ¼ 200 ꢀC; (3) sample chamber ¼ 200 ꢀC.
2.3. Hydrosilylation reaction
3. Results and discussions
All experiments were performed in a 2 L cylindrical, round-
bottomed autoclave (Weihai automatically-controlled reaction
kettle Co. Ltd., China) equipped with an inserted gas feeding pipe, a
pusher-type propeller driven by magnetic force, a snake-type wa-
ter-cooled condenser and a vertical thermometer. Before each
experiment, the autoclave was firstly heated to above 100 ꢀC under
the protection of a dried nitrogen flow and dried for about 0.5 h to
ensure that it was free from moisture. After cooling to room tem-
perature, the requisite amounts of triethoxysilane and catalyst as
well as promoters were fed into the autoclave and gas-tightness
examination was subsequently conducted with 0.5 MPa nitrogen
gas. When the nitrogen gas had been completely discharged, the
rate of the stirrer was set to a certain value and the mixture was
stirred for half an hour. Meanwhile, the temperature was raised to a
certain value. Subsequently, ethylene gas at a constant pressure of
0.35 MPa was continuously fed into the autoclave through the
inserted gas pipe line, and this moment was marked as the
3.1. Effect of iodine on hydrosilylation reaction
In order to investigate the influence of iodine on the hydro-
silylation of ethylene in more detail, we designed the reaction in
the presence of RuCl3$3H2O/I2, RuCl3$3H2O and RuI3, respectively
(Entries 1e3, Table 2). When molecular iodine was used (Entry 1,
Table 2), the reaction was conducted effectively and quickly, and
93% yield of ETES in 16 h was obtained. However, when no iodine or
RuI3 was added, the reaction rate was very slow, and only 24% or 6%
yield of ETES, respectively (Entries 2 and 3, Table 2) was obtained
within the same period. The results showed that iodine as promoter
played an important role in speeding up the reaction and it could
greatly increase the reaction yield when it is existed in a form of
molecular state.
Various factors affected on the selectivity and yield of the objec-
tive product were examined and presented in Table 2 (Scheme 4).
Table 1
Synthesis methods for ethyltriethoxysilane.
Entry
Raw material
Catalyst
Promoter
RTd (ꢀC)
Product
YieldETES (%)
1a
2b
3c
4
5
6
C2H3Si(OEt)3 [1]
HSi(OEt)3 [2]
HSi(OEt)3 [3]
HSi(OEt)3 [4]
Si(OEt)4 [5]
H2
RhCl(PPh3)3
Ru3(CO)12
11057-89-9(Pt)
H2PtCl6
NaH
NaH
56592-21-3
e
60e160
25e80
15e70
25e65
275
ETESe
CH2]CHSi(OEt)3 ETES
ETES
ETES
ETES
ETES
CH2]CH2
CH2]CH2
CH2]CH2
e
e
e
>91
90
6
30110-75-9 Me2CHOH
e
Si(OEt)4 [6]
e
KF
400
e
a
The reaction was run in a gas phase, on line, in a column connected to the mass spectrometer.
The solvent was benzene.
The reaction result showed that the Pt (0) catalysts are considerably more active in ethylene hydrosilylation than Pt (II) catalysts.
The abbreviation of reaction temperature.
b
c
d
e
The abbreviation of ethyltriethoxysilane;
, not mentioned in the literature.