Synthesis of α,ω-dichloropermethyloligosilanes by reactions of polydimethylsilane with metal chlorides

Article abstract of DOI:10.1023/A:1021376210839

The reactions of high-molecular-weight polydimethylsilane with metal chlorides in variable oxidation states at high temperature in the absence of a solvent afford mixtures of α,ω-dichloropermethyloligosilanes Cl(Me2Si)mCl (m = 2-9). The influence of the reaction conditions (temperature, reaction time, and the reagent ratio) on the composition and yields of the reaction products was examined.

Full text of DOI:10.1023/A:1021376210839

Russian Chemical Bulletin, International Edition, Vol. 51, No. 9, pp. 1751—1753, September, 2002
1751
Synthesis of α,ωꢀdichloropermethyloligosilanes by reactions
of polydimethylsilane with metal chlorides
ꢀ
A. I. Chernyavskii and N. A. Chernyavskaya
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5085. Eꢀmail: chern@ineos.ac.ru
The reactions of highꢀmolecularꢀweight polydimethylsilane with metal chlorides in variꢀ
able oxidation states at high temperature in the absence of a solvent afford mixtures of
α,ωꢀdichloropermethyloligosilanes Cl(Me2Si)mCl (m = 2—9). The influence of the reaction
conditions (temperature, reaction time, and the reagent ratio) on the composition and yields
of the reaction products was examined.
Key words: polydimethylsilane, metal chlorides, α,ωꢀdichloropermethyloligosilanes.
Dichloro substituted linear permethyloligosilanes
Cl(Me2Si)mCl (1) are used as the starting compounds for
the synthesis of various derivatives and copolymers conꢀ
taining oligosilane fragments in a polymeric chain.
α,ωꢀDichlorooligosilanes 1 have been prepared previꢀ
ously by chlorodemethylation of hexamethyldisilane
Me(SiMe2)2Me (dichlorodisilane 1a) and octamethylꢀ
trisilane Me(SiMe2)3Me (dichlorotrisilane 1b),1—4 chloroꢀ
dephenylation of 1,4ꢀdiphenyloctamethyltetrasilane
Ph(Me2Si)4Ph (dichlorotetrasilane 1c)5 and 1,5ꢀdiphenylꢀ
decamethylpentasilane Ph(Me2Si)5Ph (dichloropentaꢀ
silane 1d),6 reductive coupling of Me2SiCl2 with SmI2 (a
mixture of dichlorosilanes 1a—c),7 and the reactions of
permethylcyclosilanes (Me2Si)n (n = 5 or 6) with differꢀ
ent chlorinating agents.8—13
Results and Discussion
The reactions of polysilane 2 with the aboveꢀmenꢀ
tioned metal chlorides in the absence of solvents at high
temperature proceeded with the cleavage of the polysilane
chain to form mixtures of homologs, viz., α,ωꢀdichloroꢀ
oligosilanes 1 (Scheme 1).
Scheme 1
The conversion of polysilane 2 was rather high
(80—100%) in virtually all reactions. However, the reacꢀ
tions of polysilane 2 with transition metal chlorides (exꢀ
cept for HgCl2) afforded oligosilanes 1 in lower total
yields (no higher than 55%, see Table 1) as compared to
those obtained in the reactions of main group metal
chlorides (except for SbCl5). Apparently, the relatively
low yields of oligosilanes 1 obtained in the reactions of
transition metal chlorides with polysilane 2 are attributꢀ
able to the fact that these reactions, like those with
cyclohexasilane (Me2Si)6 (3),13 led not only to the cleavꢀ
age of the Si—Si bonds in the starting polysilane 2 but
also to the partial replacement of the Me groups by the
Cl atoms both in polysilane 2 and the resulting oligoꢀ
silanes 1. As a result, the reaction mixtures contained
large amounts of byꢀproducts with a consequent decrease
in the yield of the target products.
Highꢀmolecularꢀweight
polydimethylsilane
—(Me2Si)n— (2) is a convenient starting compound for
the synthesis of dichlorooligosilanes 1. However, the data
on the synthesis of α,ωꢀdichlorooligosilanes 1 by the
reactions of polysilane 2 with chlorinating agents are
scarce. Dichlorodisilane 1a was prepared in 42.7% yield
by passing Cl2 through a suspension of polysilane 2 in
CCl4 at –20 °C.8 A mixture of dichlorooligosilanes 1 was
prepared12 by the reaction of polysilane 2 with SnCl4 at
high temperature. However, the data on the composiꢀ
tions of the reaction products and the ratios between
these products are lacking.
In the present study, with the aim of synthesizing
dichlorooligosilanes 1, we examined the reactions of highꢀ
molecularꢀweight polydimethylsilane 2 with chlorides of
main group metals (SnIV, SbV) and transition metals (HgII,
CuII, CrIII, FeIII, TiIV, MoV, WVI) in variable oxidation
states (MClk) and investigated the influence of the reacꢀ
tion conditions on the conversion of polysilane 2, the
compositions of the reaction products, and their yields.
It should be noted that, as in our previous study,13 we
found that SbCl5 exhibits higher chemical activity as
compared to HgCl2 and SnCl4. In the reactions with
polysilane 2 and cyclosilane 3,13 antimony pentachloride
behaved analogously to transition metal chlorides. In the
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1607—1609, September, 2002.
1066ꢀ5285/02/5109ꢀ1751 $27.00 © 2002 Plenum Publishing Corporation

1752
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 9, September, 2002
Chernyavskii and Chernyavskaya
Table 1. Reactions conditions and compositions of the products prepared from polysilane 2 and metal chlorides MClk
Run
MClk
MClk : 2
T/°C Time/h
Cl(Me2Si)mCl/
Cl(Me2Si)mCl (%)
Converꢀ Yieldsa
ratiob
sion of 2 of 1a—g
at different m
2
3
4
5
6
7
8
%
1
2
3
4
5
6
7
8
HgCl2
HgCl2
HgCl2
HgCl2
HgCl2
HgCl2
HgCl2
HgCl2
SnCl4
SnCl4
SnCl4
SnCl4
SnCl4
SnCl4
SnCl4
SnCl4
SbCl5
CuCl2
CrCl3
FeCl3
TiCl4
1 : 2
1 : 2
1 : 2
1 : 1
1 : 1
2 : 1
2 : 1
2 : 1
1 : 4
1 : 2
1 : 2
1 : 2
1 : 2
1 : 2
1 : 1
1 : 1
1 : 2
1 : 1
1 : 2
1 : 1
1 : 2
1 : 2
1 : 2
180
230
230
180
180
180
230
230
180
125
180
180
180
210
180
180
20
2
0.5
2
0.5
2
2
0.5
2
3
3
1
2
3
0.5
1
3
6.5 47.6 27.6 12.4
16.4 47.3 23.4 10.9
4.9
2.0
Traces
0.3
—
—
—
—
7.4
8.8
3.3
0.8
0.4
2.2
0.2
—
2.4
1.7
11.7
1.1
5.1
—
1.0
Traces
—
Traces
—
—
—
—
2.7
6.7
Traces
—
—
—
—
—
1.3
1.2
9.3
—
Traces
—
—
—
—
94.3
97.2
100
96.1
100
100
100
100
87.2
56.6
100
100
100
100
100
100
100
97.3
38.3
100
100
100
77.9
91.9
93.4
92.9
94.6
92.3
90.5
82.5
85.9
95.5
80.8
87.3
88.3
90.5
82.4
87.1
89.9
54.2
46.2
53.9
51.0
55.5
24.5
55.4
28.8 53.2 17.3
25.7 54.7 16.9
0.7
2.4
37.9 53.3
42.8 51.2
43.6 51.8
45.0 52.6
8.8
6.0
4.6
2.4
—
—
—
—
—
—
—
c
9
13.2 31.1 26.4 18.0
13.7 30.4 20.7 14.3
22.1 41.3 20.9 12.4
1.2
5.4 c
—
10
11
12
13
14
15
16
17
18
19
20
21
22
23
26.4 44.3 21.9
27.3 45.3 23.3
34.8 37.6 16.3
11.0 46.1 35.3
15.0 49.7 29.5
6.6
3.7
9.1
7.4
5.8
7.3
6.9
—
—
—
—
—
—
0.6c
7.4c
—
0.003 49.4 22.0 17.6
180
210
180
180
200
200
1
2
1
3
1
1
46.2 30.0 13.4
3.9 29.5 20.8 17.4
52.0 30.2 12.2 4.5
35.6 22.0 20.4 16.9
—
—
—
—
—
—
MoCl5
WCl6
54.5 30.6 14.9
75.9 16.1 8.0
—
—
—
a With respect to consumed polysilane 2.
b With respect to the —SiMe2— unit.
c Traces (<0.1%) of dichlorononasilane 1h (m = 9).
reactions with SbCl5, the conversion of polysilane 2 was
100%, whereas the yield of oligosilanes 1 was only 54%.
In addition, unlike all known reactions with metal chloꢀ
rides, the reaction of polysilane 2 with SbCl5 was comꢀ
pleted in several seconds at room temperature and was
accompanied by heat evolution.
troscopy, none of the reactions under study afforded
dichlorooligosilanes with m > 9. The optimum reaction
conditions, which allow one to attain a high conversion
of polysilane 2 and to obtain longꢀchain dichlorooligoꢀ
silanes 1d—h in high yields, are as follows: the reaction
temperature is 180 °C, the reaction time is 3 h, and the
SnCl4 to polysilane 2 ratio is 1 : 4 (for SnCl4); the correꢀ
sponding conditions for HgCl2 are 180 °C, 2 h, and 1 : 2.
The procedure for the synthesis of dichlorooligosilanes
1 based on the reactions of polysilane 2 with metal chloꢀ
rides has advantages over other known procedures. Thus,
this procedure makes it possible to prepare dichloroꢀ
oligosilanes 1 containing more than six Si atoms in the
oligomeric chain, dichloropentasilane 1d (which has been
previously prepared from difficultly accessible (Me2Si)5
or Ph(Me2Si)5Ph) is generated rather easily, and insoluble
infusible polysilane 2, which is formed as a byꢀproduct
in the synthesis of cyclosilanes,14 is utilized.
The highest yields of dichlorooligosilanes 1 were
achieved in the reactions with the use of HgII and SnIV
chlorides as chlorinating agents (see Table 1). It was found
that an increase in the metal chloride : polysilane 2 ratio
in the reactions performed at the same temperature over
the same period of time (cf. runs 1, 5, and 6 and also
runs 9, 13, and 16 in Table 1) led to an increase in the
conversion of polysilane 2, a rise in the amount of shortꢀ
chain oligosilanes 1a,b, and a decrease in the amount of
longꢀchain oligosilanes 1d—h. An analogous effect was
observed when the reaction temperature or the duration
of the process was increased. The highest yields of longꢀ
chain oligosilanes 1d—h were achieved when SnCl4 and
polysilane 2 were taken in a ratio of 1 : 2 and the reacꢀ
tions were carried out at 125 °C (run 10). However, the
conversion of polysilane 2 in the latter case was only 56%.
According to the data from GLC and 29Si NMR specꢀ
Experimental
The GLCꢀmass spectrometric analysis was performed on a
Kratos MSꢀ890 instrument (15 m × 0.32 mm capillary column,

Synthesis of α,ωꢀdichloropermethyloligosilanes
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 9, September, 2002
1753
SEꢀ30 liquid phase, helium as the carrier gas, ionizing voltage
was 70 eV, the temperature was increased from 30 to 250 °C
with a rate of 10 °C min–1). The GLC analysis was carried out
on an LKhMꢀ8MD chromatograph (0.3×100 cm stainless steel
column, 5% SEꢀ30 on Chromaton NꢀAWꢀDMCS; a thermal
conductivity detector, the temperature was increased from 30
to 300 °C with a rate of 12 °C min–1, helium as the carrier gas).
The 29Si NMR spectra were recorded on Bruker WPꢀ200 SY
(39.76 MHz) and Bruker WPꢀ400 SY (79.46 MHz) spectromꢀ
eters with Me4Si as the internal standard.
Polydimethylsilane 2 was prepared according to a modified
procedure.15 Chlorides TiCl4, SnCl4, and SbCl5 were distilled
in an N2 flow immediately before use. The remaining metal
chlorides were used without purification. Carbon tetrachloride
was dried by distillation in an N2 flow over P2O5.
(CCl4), δ: 26.43 (SiMe2Cl); –40.89 (SibMe2); –39.67
(SicMe2); –37.69 (SidMe2).
According to the GLC data, the residue was a mixture of
dichlorooctasilane 1g and dichlorooctadecamethylnonasilane (1h)
in a ratio of 1 : 1.4.
Runs 1—8 and 1—23* were carried out analogously (run 17
without heating) but the residues obtained after the removal of
CCl4 were analyzed by GLC rather than distilled (see Table 1).
We thank A. I. Belokon' for measuring the mass specꢀ
trum. We also acknowledge T. V. Strelkova and E. V.
Vorontsov for recording the NMR spectra.
This study was financially supported by the Russian
Foundation for Basic Research (Project No. 00ꢀ03ꢀ
33189).
Reaction of polysilane 2 with SnCl4 (see Table 1, run 9).
Polysilane 2 (40.0 g, 0.688 mol) was placed in an argonꢀfilled
tube equipped with an inlet pipe for the introduction of reꢀ
agents, a Teflon stopcock, and a magnetic stirrer. Then SnCl4
(44.8 g, 0.172 mol) was added. The tube was placed in an oil
bath preheated to 180 °C and kept for 3 h with intense stirring.
The reaction mixture was cooled and then anhydrous CCl4
(50 mL) was added. The precipitate of SnCl2 and unconsumed
polysilane 2 were filtered off and washed with anhydrous CCl4
(2×10 mL). The precipitate was treated with acetone to disꢀ
solve SnCl2. Polysilane 2 was filtered off and dried at 60 °C in
vacuo to a constant weight. Polysilane 2 was obtained in a yield
of 5.1 g (conversion was 87.2%). The solvent was distilled off
from the solution of dichlorooligosilanes 1 in CCl4 and the
residue was analyzed by GLC (see Table 1). Fractionation of
the residue afforded compounds 1a—g.
Dichlorodisilane (1a), the yield was 5.4 g (10.1% with reꢀ
spect to consumed polysilane 2), b.p. 147.5—148 °C. 29Si NMR
(CCl4), δ: 17.23.
Dichlorotrisilane (1b), the yield was 13.0 g (27.9%), b.p.
85—86 °C (10 Torr). 29Si NMR (CCl4), δ: 24.95 (SiMe2Cl);
–43.77 (SiMe2).
Dichlorotetrasilane (1c), the yield was 11.0 g (25.5%), b.p.
110—112 °C (5 Torr). 29Si NMR (CCl4), δ: 26.22 (SiMe2Cl);
–42.62 (SiMe2).
Dichloropentasilane (1d), the yield was 7.6 g (18.3%), b.p.
95—96 °C (0.5 Torr). 29Si NMR (CCl4), δ: 26.26 (SiMe2Cl);
–41.12 (SibMe2), –41.65 (SicMe2).
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Int. Ed., 2002, 51, 175].
Dichlorohexasilane (1e), the yield was 3.1 g (7.8%), b.p.
139—142 °C (0.5 Torr). 29Si NMR (CCl4), δ: 26.21 (SiMe2Cl);
–40.89 (SibMe2); –40.02 (SicMe2).
Dichlorotetradecamethylheptasilane (1f), the yield was 1.1 g
(2.9%), b.p. 178—181 °C (0.5 Torr). Found (%): C, 35.44;
H, 8.63; Cl, 14.27; Si, 40.78. C14H42Cl2Si7. Calculated (%):
C, 35.18; H, 8.86; Cl, 14.83; Si, 41.13. 29Si NMR (CCl4), δ:
26.37 (SiMe2Cl); –41.05 (SibMe2); –39.80 (SicMe2); –37.91
(SidMe2). MS, m/z (Irel (%)): 463 [M – Me]+ (0.8); 325
[Si5Me10Cl]+ (11.8); 267 [Si4Me8Cl]+ (100); 209 [Si3Me6Cl]+
(35.4); 174 [Si3Me6]+ (11.1); 173 [Si3Me5CH2]+ (13.5); 159
[Si3Me5]+ (11.5); 131 [Si2Me5]+ (28.2); 116 [Si2Me4]+ (9.2);
115 [Si2Me3CH2]+ (7.5); 73 [SiMe3]+ (55.6).
14. E. Carberry and R. West, J. Am. Chem. Soc., 1969, 91,
5440; R. West, L. Brough, and W. Wojnowski, Inorg. Synth.,
1979, 19, 265.
15. J. P. Wesson and T. C. Williams, J. Polym. Sci., Part A,
1979, 17, 2833.
* In all experiments, we used polysilane 2 from the same prepaꢀ
ration. Its conversion was determined after separation of the
precipitate and dissolution of the metal chloride salt in the
corresponding solvent.
Dichlorohexadecamethyloctasilane (1g), the yield was
0.5 g (1.3%), b.p. 185—187 °C (0.06 Torr). Found (%):
C, 35.41; H, 8.85; Cl, 12.98; Si, 41.43. C16H48Cl2Si8. Calcuꢀ
lated (%): C, 35.84; H, 9.02; Cl, 13.23; Si, 41.91. 29Si NMR
Received June 25, 2001;
in revised form 2 April, 2002