Preparation of vinylsilane from monosilane and vinyl chloride

Article abstract of DOI:10.1016/S0022-328X(99)00410-6

Vinylsilane (CH₂=CH-SiH₃) was prepared by the dehydrochlorination reaction between SiH₄ and vinyl chloride. The reactions were carried out in the gas phase at 450-500°C using a tube reactor, and the maximum yield of vinylsilane was 21% when the conversion of SiH₄ was 32%. A small amount of CCl₄ and CH₃NO₂ accelerated the reaction. A reaction mechanism involving :SiH₂, which was generated by the thermal decomposition of SiH₄, was proposed.

Full text of DOI:10.1016/S0022-328X(99)00410-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 590 (1999) 36–41
Preparation of vinylsilane from monosilane and vinyl chloride
Masayoshi Itoh *, Kenji Iwata, Mineo Kobayashi
Material Science Laboratory, Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura-city, Chiba 299-0265, Japan
Received 27 April 1999; received in revised form 23 July 1999
Abstract
Vinylsilane (CH2ꢀCHꢁSiH3) was prepared by the dehydrochlorination reaction between SiH4 and vinyl chloride. The reactions
were carried out in the gas phase at 450–500°C using a tube reactor, and the maximum yield of vinylsilane was 21% when the
conversion of SiH4 was 32%. A small amount of CCl4 and CH3NO2 accelerated the reaction. A reaction mechanism involving
:SiH2, which was generated by the thermal decomposition of SiH4, was proposed. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Vinylsilane; Dehydrochlorination; Monosilane; Vinyl chloride; Thermal reaction
at elevated temperature in the gas phase with very low
1. Introduction
yields and selectivities [1].
We have recently reported the hydrosilylation reac-
tions of olefins with SiH4 and Si2H6 in the presence of
transition metal complexes [2,3], metal hydrides [3,4],
and radical initiators [3] to give the hydrosilylated
compounds with high yields. Moreover, we have
found that the dehydrogenative coupling reactions be-
tween SiH4 and monosubstituted alkynes under metal
hydride give the alkynylsilanes with high yield and
selectivity [5].
Vinylsilane (CH2ꢀCHꢁSiH3, b.p. −22.8°C, abbrevi-
ated VS) is an interesting and useful compound as a
monomer for the polymerization reaction to yield
poly(vinylsilane), which is a ceramic precursor [6–8],
and as a monomer for the copolymerization reaction
with propylene [9]. VS has usually been prepared by
reaction (2).
Regarding organic silicon compounds, the chemical
industry has been making amazing strides, as typified
by silicones (polyorganosiloxanes). In most cases, the
starting materials of the organic silicon compounds
are alkylchlorosilanes obtained by Rochow’s direct
process, which can be exhibited by the following for-
mula:
Si+R1Cl“R12SiCl2, R31SiCl, R1SiHCl2, HSiCl3
(1)
wherein R1 is industrially limited to a methyl group or
a phenyl group.
On the other hand, the current mass production of
monosilane (SiH4) and disilane (Si2H6) (hereinafter re-
ferred to simply as ‘silanes’) has become possible along
with the development of the semiconductor industry,
and so these silanes are inexpensive and easily avail-
able. In connection with techniques for manufacturing
organic silicon compounds by the use of these silanes,
research has scarcely been conducted. Pyrolytic reac-
tions and photochemical reactions have been carried
out between SiH4 or Si2H6 and ethylene or acetylene
(2)
This report concerns a new preparation method of
VS using a dehydrochlorination reaction between
SiH4 and vinyl chloride to give vinylsilane (reaction
(3)).
(3)
* Corresponding author.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00410-6

M. Itoh et al. / Journal of Organometallic Chemistry 590 (1999) 36–41
37
Fig. 1. Reaction equipment: Fl, gas flow meter; V, valve; R, reactor;
F, electric furnace; P, gas filter; C, condenser; T, trap containing etha-
nol solution of LiOEt, or condenser; E, exclusion apparatus of VC.
2. Experimental
2.1. Reaction procedures
The reaction equipment is shown in Fig. 1. SiH4 of
99.999% purity and vinyl chloride (VC) of 99.5% purity
were fed at constant flow rates (30–170 N ml min−1) to
a reaction tube having an inner diameter of 16 mm and
a height of 90 mm (Table 1) or 60 mm (Tables 2 and 3,
Figs. 2–4) that had been set to reaction temperatures
(350–500°C), and the reaction was then carried out for
5 h under atmospheric pressure. The gaseous products
were analyzed by GC and then poured into an ethanol
solution of LiOEt (Li 0.5 wt.%). In some experiments,
the reactants were accompanied by a small amount of
CCl4, CH3NO2, CBrCl3 or CCl2BrCH2Br. BCl3, AlCl3,
CuCl, CoCl2 or NiCl2 were packed in the reaction tube
Fig. 2. Changes in the reaction results vs. the total gas flow rate of SiH4
and VC. Reaction conditions: reactor, inner diameter of 16 mm and
height of 60 mm; reaction temperature, 475°C; mole ratio of VC/SiH4
(1.1/1), 100 N ml min−1 corresponds to a residence time of 4.0 min.
(ꢀ) Conversion of SiH4, (ꢁ) yield of VS, (ꢂ) selectivity for VS.

38
M. Itoh et al. / Journal of Organometallic Chemistry 590 (1999) 36–41
Table 2
Thermal reaction of several compounds a
b
Run no. Reactant
(volume %)
Conversion
Main product
(%)
1
2
SiH4
VC
(57)
(67)
8.9
0.2
H2, Si2H6
CH2ꢀCH2,
CHꢀCH
3
4
VS
(10)
8.9
poly(vinylsilane)
\SiH4, DVS
H2, Si2H6\
EtSiH3, DVS
SiH4
VS
(54)
(10)
4.3
21.0
5
6
SiH4
HCl
(49)
(15)
8.2
15.1
H2, Si2H6\
chlorosilanes
VC
VS
(54)
(10)
2.6
8.2
CH2ꢀCH2\SiH4,
DVS
7
8
VC
HCl
VS
(56)
(13)
(10)
(16)
0.1
0
17.7
13.0
Fig. 3. Effects of additions of CCl4 and CH3NO2. Reaction condi-
tions: reactor, inner diameter of 16 mm and height of 60 mm; total
gas flow rate of SiH4 and VC, 100 N ml min−1; mole ratio of CCl4
or CH3NO2/VC/SiH4 (0.02/1.1/1). (ꢀ,ꢁ,ꢂ) VC/SiH4 (1.1/1.0),
(ꢀ,ꢁ,ꢂ) VC/SiH4/CCl4 (1.1/1.0/0.02), (ꢃ, ,ꢄ) VC/SiH4/CH3NO2
(1.1/1.0/0.02). (ꢀ,ꢀ) Conversion, (ꢁ,ꢁ) yield of VS, (ꢂ,ꢂ) selectiv-
ity for VS.
SiH4\CH2ꢀCH2,
HCl
DVS
a Reactor was a tube having an inner diameter of 16 mm and a
height of 60 mm. The total amount of the charged gases is 100 N ml
(residence time, 2.7 s), and the reactions were carried out at 475°C.
b Accompanied by argon. The volume % of the reactants was
determined by considering the concentrations of the reactants and
products in the reaction of SiH4 with VC.
determined by GC measurement, the amounts of
Si(OEt)4 (calculated as SiH4 and chlorosilane) and
CH2ꢀCHSi(OEt)3 (calculated as VS and vinyl-
chlorosilane) in the ethanol solution of LiOEt, which
were obtained by chemical analysis and GC, and the
weight of the liquid polymer in the reactor and the gas
filter. The results in Table 1 were obtained using these
and used as catalysts. CH2ꢀCHCH2Cl, CH3CH2Cl,
C6H5Cl, CH2ꢀCHBr and CH2ꢀCHF were also used
instead of VC.
The reaction results were obtained using the follow-
ing data. (1) The composition of gaseous products
Table 3
Dehydrochlorination reactions between SiH4 and vinyl compounds a
Run
no.
Charged gas
(N ml min−1
Reaction temperature
(°C)
Conversion of SiH4
(%)
Yield of RSiH3
(%) b
Selectivity for RSiH3
(%) c
)
1
2
3
CH2ꢀCHCl 48
SiH4 52
SiH4 54
SiH4 58
450
475
450
475
450
475
500
425
450
475
450
475
500
6.5
5.0
11.7
5.7
11.8
0
77.4
64.1
45.5
41.3
0
0
1.0
36.1
25.1
11.9
2.5
18.2
12.5
28.6
8.0
32.7
20.0
21.1
41.6
50.3
3.7
CH2ꢀCHCH2Cl d 54
CH3CH2Cl 58
He 8
0
4
5
C6H5Cl d 58
SiH4 47
SiH4 41
0.2
7.6
10.4
6.0
0.1
0.1
0.3
CH2ꢀCHBr e 41
He 33
6
CH2ꢀCHF 58
SiH4 58
9.2
28.6
1.0
0.9
a Reactor was a tube having an inner diameter of 16 mm and a height of 60 mm. Residence time is 2.7 s at 475°C when the total amount of
the charged gases is 100 N ml.
b Based on the charged SiH4.
c % ratio of RSiH3 versus the reacted SiH4.
d Charged using a liquid feed pump.
e Accompanied by helium.

M. Itoh et al. / Journal of Organometallic Chemistry 590 (1999) 36–41
39
data. (2) The amounts of gaseous products determined
by GC using a small amount of argon as an internal
standard. The results in Table 3 and Figs. 2–4 were
obtained by using these data.
2.2. Product assignment
The gaseous and liquid products were collected in a
trap cooled to −100°C or less, and after completion of
the reaction, the products were identified by means of
mass spectroscopy, IR and GC.
VS; IR (gas): w(CH2) 3050, 2951, w(SiꢁH) 2154,
w(CꢀC) 1598, l(CH2) 1398, l(SiH3) ca. 910, w(SiC) ca.
700 cm−1. MS (m/z): (EI mode) 58 (M+), 57, 56, 55,
43 (base peak). Si2H6; MS (m/z): (EI mode) 62 (M+),
61, 60 (base peak), 58, 57. CH2ꢀCH2; MS (m/z): (EI
mode) 28 (M+, base peak), 27, 26, 25. EtSiH3; MS
(m/z): (EI mode) 60 (M+), 59, 58 (base peak), 43, 31.
(CH2ꢀCH)2SiH2; MS (m/z): (EI mode) 84 (M+), 83
(base peak), 58, 56, 55. CH2ꢀCHCHꢀCHSiH3; MS
(m/z): (EI mode) 84 (M+), 83, 57, 56 (base peak), 55,
53. Polymer (I); IR (neat): w(CH2) 2930 cm−1, w(SiꢁH)
2160, l(CH2) 1450, 1410, l(CꢁH in CHCl) 1260,
Fig. 4. Correlations of the yield of VS and the selectivity for VS with
the conversions of SiH4. All the data in Figs. 2 and 3, and two data
(*, 2*) are plotted. *, 2*: total gas flow rate of SiH4 and VC, 100 N
ml min−1; reaction temperature, 475°C; mole ratio of VC/SiH4,
18/82 (*) and 86/16 (2*). (ꢁ) Yield of VS, (ꢂ) selectivity for VS,
yield of VS and selectivity for VS when (ꢁ,ꢂ) CCl4 and ( ,ꢄ)
CH3NO2 were added.
w(SiHn) 920, l(CꢁCl) 715 cm−1
.
The spectral data for VS [10], Si2H6 [11], CH2ꢀCH2
[12] and EtSiH3 [12] coincided with those in the
literature. Polymer (I) was assigned to be
poly(vinylsilane) [6] ([ꢁCH2CH(SiH3)ꢁ]x[ꢁCH2CH2Si-
H2ꢁ]y, IR adsorption bands 2930, 2160, 1450, 920
cm−1), which included some poly(vinylchloride) (very
weak adsorption bands 1410, 1260, 715 cm−1).
(VC/SiH4=18/82) was used. From these results, the
best reaction condition to obtain VS using the reaction
apparatus in Fig. 1 would be as follows: gas flow rate,
100–170 N ml min−1; reaction temperature, 475°C;
and the mole ratio of VC/SiH4=4/1. A small volume
reaction tube having an inner diameter of 2 or 10 mm
and that having a diameter of 16 mm which was packed
with glassy or stainless steel wool were used. All of the
yields, conversions and selectivities are on the curves in
Fig. 4.
Halogenated hydrocarbons and metal chlorides
(Lewis acid) that catalyze the dehydrochlorinative cou-
pling reaction between HSiCl3 and C6H5Cl to give
C6H5SiCl3 [13,14] were used in order to accelerate the
reaction. Only CCl4 and CH3NO2 had effects on the
reaction as shown in Figs. 3 and 4, that is, the reaction
occurred at lower temperature when CCl4 or CH3NO2
was present.
3. Results
The reaction of SiH4 with VC proceeded above
420°C in the reaction equipment shown in Fig. 1 to
yield VS and a small amount of other silicon-containing
compounds such as Si2H6, divinylsilane, vinylchlorosi-
lane, 1,3-butadienyl silane and some chlorosilanes, as
shown in Table 1. Considerable amounts of ethylene
and polymer (I), which is almost poly(vinylsilane), were
also produced. The results indicate that the dehy-
drochlorination reaction occurred between SiH4 and
VC.
The mole ratio of VC/SiH4, the gas flow rate and the
reaction temperature affected the reaction results
greatly as shown in Table 1 and Figs. 2 and 3, respec-
tively. The correlations between the yield of VS, the
selectivity for VS and the conversion of SiH4 are plot-
ted in Fig. 4 using the data obtained from the experi-
ments at various reaction temperatures, mole ratios of
VC/SiH4, and gas flow rates. The high conversion
produced a high yield of VS but low selectivity for VS
except for one experimental result, in which much SiH4
Fig. 5. Postulated mechanism of the reaction of SiH4 with VC.

40
M. Itoh et al. / Journal of Organometallic Chemistry 590 (1999) 36–41
The thermal reactions of SiH4, VC, VS, SiH4ꢁVS,
reaction between :SiH2 and VC would be high, which
would result in a high selectivity for VS. On the other
hand, a low ratio of VC/SiH4 causes low selectivity and
yield even at low conversion, because the side reactions
involving SiH4 would proceed considerably (see Fig. 4).
A part of the produced VS was converted to poly(vinyl-
silane) ([ꢁCH2CH(SiH3)ꢁ]x[ꢁCH2CH2SiH2ꢁ]y) in the re-
actor by radical polymerization reaction [6]. Ethylene
would be produced by the reactions of VS with HCl
and VC (see run nos. 6 and 8 in Table 2).
SiH4ꢁHCl, VCꢁVS, VCꢁHCl and VSꢁHCl were carried
out in order to investigate the reaction mechanism
using the same reaction apparatus. The conversions and
the main products are shown in Table 2.
Several kinds of halogenated hydrocarbons were re-
acted with SiH4 (Table 3). CH2ꢀCHCH2Cl and
CH2ꢀCHBr reacted like VC and gave the silyl com-
pounds (RSiH3). In the case of CH3CH2Cl, C6H5Cl and
CH2ꢀCHF, the silyl compounds were not obtained.
When CCl4 or CH3NO2 was poured with SiH4 and
VC, a radical (·CCl3 or ·CH3) would be produced at a
temperature lower than 450°C, and a silyl radical
(·SiH3) would be produced by the reaction of ·CCl3 or
·CH3 with SiH4, followed by other reactions. The low
yield of silyl compound in the reactions of SiH4 with
CH3CH2Cl, C6H5Cl and CH2ꢀCHF suggests that the
species (:SiR2) formed by the reaction between :SiH2
and hydrocarbon would not be obtained, but the exact
reason for this result is not obvious. The correlation
curves of yield, conversion and selectivity were quite the
same in any reactor. The reaction results depended on
the volume of the reactor, so most of the reaction
would occur in the gas phase, not on the surface of the
reactor.
4. Discussion
There have been many reports about the dehydro-
halogenation reaction between hydrosilanes (HnSiY4−n
,
wherein Y=Cl, phenyl or alkyl) and halogenated hy-
drocarbons (RX, wherein X=Cl [13], Br [14,15] or I
[16]). With regard to the reaction between SiH4 and
halogenated hydrocarbons concerning the present re-
port, only a thermal reaction between SiH4 and VC has
been reported [17], but the production of organic silicon
compounds (in this case, VS, divinylsilane and similar
compounds), which the present report discusses, is not
found at all in the above-mentioned report. Perhaps,
the results would be caused by failure in trapping the
compounds of low boiling point. In our experiment, VS
which was identified by IR and GC–MS was the main
product.
4.2. Process of synthesis of 6inylsilane
The following recycle process for synthesizing VS
can be considered. VS (b.p. −22.8°C) would be sepa-
rated by distillation. Unreacted VC (b.p. −13.9°C)
and the products of higher boiling point than VS, such
4.1. Mechanism of the dehydrochlorination reaction
as Si2H6 (b.p. −14.3°C), CH3CH2SiH3 (b.p.
−
CH2ꢀCHSiCl3 and PhSiCl3 were synthesized by the
dehydrochlorination reactions at high temperature
(500–720°C) through a hot tube between HSiCl3 and
CH2ꢀCHCl or C6H5Cl, respectively. The workers con-
cluded that the initial step is homolytic dissociation of
the SiꢁH bond of HSiCl3 to produce the ·SiCl3 radical
and that this is followed by the attack of the radical on
the halogenated hydrocarbon [13] (reaction (4)).
14.0°C), CH2ꢀCHSiH2Cl and (CH2ꢀCH)2SiH2, would
be washed with alkaline water, which results in the
hydration of the hydrosilanes to give the siloxane
polymers, and then VC would be dried through zeolite
and fed to the reactor again. Unreacted SiH4 (b.p.
−112°C), and the products of lower boiling point
than VS, such as H2, CH4, CH2ꢀCH2 (b.p.
−
103.9°C), HCl and H3SiCl (b.p. −30°C), would be
distilled, and SiH4 would be recycled to the reactor.
HCl and H3SiCl would be removed by the washing
with alkaline water, and H2 and CH4 of low boiling
point would be disposed of as industrial waste. A
considerable amount of CH2ꢀCH2 is produced, but it
(4)
Claassen, Bloem and Kuiper et al. reported that the
:SiH2 radical is generated by the thermal decomposition
of SiH4 in the gas phase based on kinetic studies of the
thermal reaction [18]. As shown in Table 2 (run nos. 1
and 2), SiH4 reacted at 475°C, but VC did not react.
Therefore, SiH4 would decompose thermally and would
generate a reactive species of :SiH2, and then it would
induce the next reactions as shown in Fig. 5. From
Table 2, the order of the reaction rates is roughly
VSꢁHCl\SiH4ꢁVS, SiH4, VS, SiH4ꢁHCl, VCꢁVS\
VCꢁHCl, VC. The side reactions involving SiH4 or VS
were fast. At a high ratio of VC/SiH4, the chance of the
,
could be removed by adsorption on 5 A molecular
sieves [19].
Alkynylsilanes having a reactive and useful silyl
group (ꢁSiH3) are usually prepared by the reduction of
the corresponding alkynylchlorosilane using an expen-
sive metal hydride [20]. We offer a new process for
synthesizing a silyl compound using SiH4. The selectiv-
ity for the silyl compound is not sufficient. Further
study is needed for the development of a more effec-
tive process.

M. Itoh et al. / Journal of Organometallic Chemistry 590 (1999) 36–41
41
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5. Conclusions
[4] M. Kobayashi, M. Itoh, Chem. Lett. (1996) 1013.
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[6] M. Itoh, K. Iwata, M. Kobayashi, R. Takeuchi, T. Kabeya,
Macromolecules 31 (1998) 5609.
Vinylsilane (CH2ꢀCHꢁSiH3) was prepared by the de-
hydrochlorination reaction between SiH4 and vinyl chlo-
ride. The reactions were carried out in the gas phase at
450–500°C using a tube reactor, and the maximum yield
of vinylsilane was 21% when the conversion of SiH4 was
32%. Divinylsilane, 1,3-butenylsilane, disilane, chlorosi-
lanes and poly(vinylsilane) were produced as by-prod-
ucts. A radical reaction mechanism involving :SiH2,
which was generated by the thermal decomposition of
SiH4, was proposed. A small amount of CCl4 and
CH3NO2 accelerated the reaction.
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Acknowledgements
Part of this work was performed by Mitsui Chemicals
Inc., under the management of the Japan Chemical
Innovation Institute as part of the Industrial Science and
Technology Frontier Program supported by the New
Energy and Industrial Technology Development Organi-
zation.
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