Unexpected reactions of dichloro(ethyl)silane with DMSO in organic solvents

Article abstract of DOI:10.1007/s11172-017-1827-3

The effect of the solvent nature on the composition of the products formed upon the reaction between EtSi(H)Cl₂ and DMSO (molar ratio 1: 1, 0 °C) was revealed. This reaction in non-polar and low polar solvents (toluene, chloroform) gives oligoethyl(hydro)cyclo-siloxanes ((EtSi(H)O)_n, n = 3—8) as the major products in the yields up to 77%. In MeCN, oligoethyl(hydro)cyclosiloxanes are formed along with cyclic monochlorinated siloxanes ((EtSi(H)O)_n(EtSi(Cl)O), n = 2—7) in a ratio of ~7: 3 (68: 29 wt.%). In excess diethyl ether, the overall yield of oligoethyl(hydro)cyclosiloxanes does not exceed 25% and the major products are linear α,ω-diethoxyoligoethyl(hydro)siloxanes (EtO(EtSi(H)O)_nEt, n = 2—7) formed in 70—75% yields. A plausible reaction mechanism leading to the final products was suggested. Apparently, the reaction proceeds via ethyl(hydro)-and chloro(ethyl)silanones as intermediates.

Full text of DOI:10.1007/s11172-017-1827-3

Russian Chemical Bulletin, International Edition, Vol. 66, No. 5, pp. 903—907, May, 2017
903
Unexpected reactions of dichloro(ethyl)silane with DMSO in organic solvents
S. V. Basenko and A. A. Maylyan
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences,
1 ul. Favorskogo, 664033 Irkutsk, Russian Federation.
Eꢀmail: sv_basenko@irioch.irk.ru
The effect of the solvent nature on the composition of the products formed upon the
reaction between EtSi(H)Cl2 and DMSO (molar ratio 1 : 1, 0 οC) was revealed. This reaction
in nonꢀpolar and low polar solvents (toluene, chloroform) gives oligoethyl(hydro)cycloꢀ
siloxanes ((EtSi(H)O)n, n = 3—8) as the major products in the yields up to 77%. In MeCN,
oligoethyl(hydro)cyclosiloxanes are formed along with cyclic monochlorinated siloxanes
((EtSi(H)O)n(EtSi(Cl)O), n = 2—7) in a ratio of ~7 : 3 (68 : 29 wt.%). In excess diethyl ether,
the overall yield of oligoethyl(hydro)cyclosiloxanes does not exceed 25% and the major
products are linear α,ωꢀdiethoxyoligoethyl(hydro)siloxanes (EtO(EtSi(H)O)nEt, n = 2—7)
formed in 70—75% yields. A plausible reaction mechanism leading to the final products was
suggested. Apparently, the reaction proceeds via ethyl(hydro)ꢀ and chloro(ethyl)silanones as
intermediates.
Key words: dichloro(ethyl)silane, dimethyl sulfoxide, ethyl(hydro)silanone, chloroꢀ
(ethyl)silanone, oligoethyl(hydro)cyclosiloxanes, diethoxyoligoethyl(hydro)siloxanes.
Oligoorganyl(hydro)cyclosiloxanes, for instance,
1,3,5,7ꢀtetraethylcyclotetrasiloxane, were tested as the
precursors for plasmaꢀenhanced chemical vapor deposition
of the silica layers in microelectronic device fabrication,1
for manufacturing of nanosized hybrid materials possessing
unique properties,2 and for chemical finishing of textiles.3
The conventional synthetic approach towards oligoꢀ
organyl(hydro)cyclosiloxanes is hydrolysis of organylꢀ
(hydro)dichlorosilanes in diethyl ether4 or ethanol.5 The
patent6 describes the use of the crown ethers (15ꢀcrownꢀ
5, 18ꢀcrownꢀ6, etc.) as the solvents. The authors believed6
that the high boiling points of the crown ethers facilitate
the production of highꢀpurity lowꢀboiling cyclosiloxanes.
Reaction of EtSi(H)Cl2 with excess THF and lithium
However, the products of these reactions have not been
studied in detail.
According to our data, performing the reaction of diꢀ
organyldichlorosilanes with DMSO in excess chlorosilane
significantly lowered the yields of cyclic compounds (up
to 7—11%) and linear disiloxanes were the major prodꢀ
ucts in this case.17
The present work is devoted to the study of the prodꢀ
ucts formed in the reaction of EtSi(H)Cl2 with DMSO in
different organic solvent (toluene, chloroform, acetoꢀ
nitrile, and diethyl ether).
Results and Discussion
ο
metal in a molar ratio of 1 : 4 : 2 at 35—45 C also gives
Reactions of EtSi(H)Cl2 with DMSO were carried
out at a 1 : 1 reagent ratio at 0 °C until 95% conversion of
the starting reagents was achieved. Composition of the
reaction mixture and contents of the products were deterꢀ
mined by gas chromatography and gas chromatography—
mass spectrometry (Tables 1—3).
Table 1 shows that in toluene and CHCl3 the yields of
OEHCSs D3—D7 reached 73—77% with content of D3
being 33—36%.
It is of note that hydrolysis of EtSi(H)Cl2 in ethanol5
gives cyclic products in 41% overall yield. Out of this
amount, 48% is 1,3,5ꢀtriethylcyclotrisiloxane (D3), i.e.,
its yield is actually equal to ~20%. Yields of 1,3,5,7ꢀtetraꢀ
ethylcyclotetrasiloxane (D4) and 1,3,5,7,9ꢀpentaethylꢀ
cyclopentasiloxane (D5) are 33% and 11% of total quanꢀ
tity of the cyclic products formed, respectively.
oligoethyl(hydro)cyclosiloxanes7 (OEHCSs), namely, the
corresponding cyclotetrasiloxane (D4, 12%), cyclotriꢀ
siloxane (D3, 35%), and cyclopentasiloxane (D5, 15%).
The gas chromatography—mass spectrometry analyꢀ
sis of the products of hydrolysis of EtSi(H)Cl2 in benzene
and butanol showed formation of 18 and 39 compounds,
respectively.8
Earlier, we9—11 and other researches12—14 have found
that the reaction of diorganyldichlorosilanes with DMSO
is a convenient synthetic route to perorganylcyclotrisilꢀ
oxanes. Chan and coꢀworkers15 have noted that this reꢀ
action is accompanied with the reduction of DMSO to
dimethyl sulfide and Ph2SO to Ph2S. Benkeser16 has deꢀ
scribed the explosive reaction between the compounds
bearing the Si—H bond (for instance, HSiCl3) and Ph2SO.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 0903—0907, May, 2017.
1066ꢀ5285/17/6605ꢀ0903 © 2017 Springer Science+Business Media, Inc.

904
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 5, May, 2017
Basenko and Maylyan
Table 1. Main characteristic ions in mass spectra of ethylcyclosiloxanes (EtSiHO)n (n = 3—8) synthesized in toluene, CHCl3,
MeCN, and Et2O
Ion
m/z (Irel (%))
n = 5
n = 3
n = 4
n = 6
n = 7
n = 8
(M – H)+
221 (42)
11—
193 (100)
165 (87)
163 (14)
11—
137 (67)
135 (33)
133 (10)
119 (2)
11—
11—
191 (7)
11—
11—
11—
295 (2)
281 (1)
267 (100)
239 (21)
237 (5)
11—
211 (12)
209 (6)
207 (2)
193 (2)
181 (5)
179 (2)
165 (5)
11—
369 (1)
355 (1)
341 (100)
11—
311 (5)
11—
443 (1)
429 (6)
415 (30)
11—
517 (1)
503 (3)
489 (31)
471 (2)
11—
443 (8)
11—
11—
429 (50)
415 (4)
11—
401 (8)
11—
369 (84)
355 (82)
341 (100)
295 (20)
267 (11)
591 (—)
577 (11)
11—
545 (3)
11—
(M – Me)+
(M – Et)+
(M – Et – C2H4)+
(M – Et – C2H6)+
11—
(M – H – EtHSiO)+
(M – Et – 2 C2H4)+
(M – Et – C2H4 – C2H6)+
(M – Et – 2 C2H6)+
(M – Et – EtHSiO)+
(M – Et – 2 C2H4 – C2H6)+
(M – Et – C2H4 – 2 C2H6)+
(M – H – 2 C2H4 – EtHSiO)+
(M – Et – 4 C2H4)+
(M – Et – 2 C2H6 – EtHSiO)+
(M – Et – 2 EtHSiO)+
(M – H – 3 EtHSiO)+
(M – Et – 3 EtHSiO)+
369 (4)
359 (2)
357 (26)
355 (100)
341 (6)
329 (9)
327 (34)
313 (1)
295 (1)
281 (4)
267 (3)
221 (2)
193 (2)
517 (49)
11—
11—
11—
505 (4)
503 (7)
489 (11)
477 (8)
11—
461 (6)
443 (73)
429 (20)
415 (18)
369 (66)
341 (100)
281 (37)
267 (3)
255 (10)
253 (35)
239 (2)
221 (1)
207 (2)
11—
133 (2)
119 (4)*
11—
11—
11—
11—
11—
11—
* 119 (4) (M – 2 Et)++
.
Table 2. Main characteristic ions in mass spectra of chloro(ethyl)cyclosiloxanes (EtSiHO)n(EtSiClO) (n = 2—7) synthesized
in MeCN
Ion
m/z* (Irel (%))
n = 2
n = 3
n = 4
n = 5
n = 6
n = 7
(M – H)+
255 (30)
227 (100)
199 (70)
171 (63)
169 (17)
11—
11—
11—
11—
135 (10)
133 (9)
125 (7)
11—
11—
193 (28)
11—
11—
11—
173 (10)
11—
11—
329 (2)
301 (100)
273 (21)
245 (14)
243 (7)
11—
403 (1)
375 (100)
11—
11—
11—
315 (26)
309 (7)
301 (2)
287 (21)
11—
281 (45)
273 (3)
259 (8)
253 (37)
241 (2)
11—
477 (1)
449 (34)
11—
11—
11—
389 (100)
383 (12)
375 (2)
361 (35)
11—
551 (—)
523 (10)
11—
11—
11—
463 (36)
457 (4)
449 (4)
435 (7)
11—
625 (—)
597 (2)
11—
11—
11—
537 (4)
531 (3)
11—
(M – Et)+
(M – Et – C2H4)+
(M – Et – 2 C2H4)+
(M – Et – C2H4 – C2H6)+
(M – Et – 2 C2H6)+
(M – Et – HCl – C2H6)+
(M – Et – EtHSiO)+
11—
227 (2)
213 (2)
209 (1)
207 (2)
199 (4)
185 (2)
11—
11—
11—
11—
151 (3)
11—
(M – Et – C2H4 – 2 C2H6)+
(M – Et – HCl – 2 C2H4)+
(M – Et – HCl – C2H4 – C2H6)+
(M – Et – C2H4 – EtHSiO)+
(M – Et – 2 C2H4 – 2 C2H6)+
(M – Et – HCl – 2 C2H4 – C2H6)+
(M – Et – 2 C2H6 – EtHSiO)+
(M – H – 2 C2H6 – EtClSiO)+
(M – Et – 2 EtHSiO)+
11—
505 (4)
503 (10)
11—
11—
11—
463 (12)
457 (4)
449 (19)
11—
443 (100)
429 (17)
415 (43)
403 (17)
393 (4)
355 (89)
11—
429 (62)
11—
333 (9)
327 (31)
315 (2)
309 (3)
11—
299 (8)
295 (1)
281 (5)
267 (3)
255 (4)
245 (4)
407 (4)
401 (5)
389 (30)
383 (17)
375 (15)
11—
369 (84)
355 (56)
341 (100)
329 (4)
319 (4)
11—
(M – Et – HCl – 3 C2H4 – C2H6)+
(M – Et – HCl – 2 C2H4 – 2 C2H6)+
(M – Et – 2 C2H6 – EtClSiO)+
(M – Et – EtHSiO – EtClSiO)+
(M – H – 3 EtHSiO)+
225 (17)
221 (2)
207 (2)
193 (2)
181 (3)
171 (6)
123 (3)
11—
107 (2)
11—
11—
11—
(M – Et – 2 C2H4 – 2 EtHSiO)+
* Based on isotope 35Cl. The ratio of the peak intensities agrees with the calculations.

Unexpected reactions ethyl(hydro)dichlorosilane
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 5, May, 2017
905
Table 3. Main characteristic ions in mass spectra of linear α,ωꢀdiethoxy(ethyl)siloxanes EtO(EtSiHO)nC2H5 (n = 2—7) synthesized
in Et2O
Ion
m/z (Irel (%))
n = 2
n = 3
n = 4
n = 5
n = 6
n = 7
(M – H)+
221 (100)
207 (83)
193 (38)
191 (10)
177 (7)
163 (2)
161 (2)
147 (5)
133 (15)
119 (8)
11—
103 (6)
11—
189 (21)
173 (39)
11—
295 (19)
281 (45)
11—
369 (37)
355 (100)
341 (1)
339 (2)
325 (4)
311 (2)
309 (6)
295 (20)
281 (43)
267 (26)
253 (18)
251 (2)
239 (14)
237 (6)
221 (1)
207 (3)
193 (4)
11—
443 (8)
429 (22)
11—
11—
399 (1)
11—
383 (19)
369 (32)
355 (100)
341 (29)
327 (15)
325 (5)
313 (5)
311 (5)
295 (4)
281 (4)
267 (3)
11—
517 (4)
503 (17)
11—
11—
11—
591 (1)
577 (6)
11—
11—
11—
(M – Me)+
(M – Et)+
(M – H – C2H6)+
265 (7)
251 (5)
237 (3)
235 (14)
221 (75)
207 (100)
193 (66)
179 (42)
177 (9)
165 (17)
163 (12)
11—
133 (11)
119 (7)
11—
11—
173 (67)
(M – EtO)+
(M – Et – C2H6)+
(M – H – 2 C2H6)+
(M – H – EtHSiO)+
(M – Me – EtHSiO)+
(M – Et – EtHSiO)+
(M – Me – C2H4 – EtHSiO)+
(M – EtO – EtHSiO)+
(M – Et – C2H4 – EtHSiO)+
(M – Et – C2H6 – EtHSiO)+
(M – H – 2 EtHSiO)+
(M – Me – 2 EtHSiO)+
(M – Et – 2 EtHSiO)+
(M – H – 3 EtHSiO)+
(M – Et – 3 EtHSiO)+
(C2H4SiHO)+
11—
11—
457 (8)
443 (14)
429 (98)
415 (7)
401 (4)
399 (11)
11—
531 (2)
517 (5)
503 (14)
489 (1)
11—
473 (7)
11—
11—
443 (100)
429 (53)
415 (37)
369 (34)
341 (20)
173 (35)
11—
369 (100)
355 (93)
341 (69)
295 (11)
267 (7)
73 (57)
11—
11—
11—
173 (39)
11—
173 (32)
11—
173 (23)
Unexpectedly, the reaction of EtSi(H)Cl2 with DMSO
at a 1 : 1 molar ratio in MeCN at 0 °C gives cyclic
monochlorinated siloxanes (CMCSs), which are formed
along with OEHCSs in a ratio of 3 : 7 (see Table 2). In
diethyl ether, the major products are linear α,ωꢀdiethꢀ
oxyoligoethyl(hydro)siloxanes (EtO(EtSiHO)nEt, n = 2—7)
formed in 70—75% yields (see Table 3). It should be emꢀ
phasized that compounds bearing one and three ethoxy
groups were not detected and the yields of OEHCSs did
not exceed 20—25%.
The major sulfurꢀcontaining products of the studied reacꢀ
tions are dimethyl sulfide and chloromethyl methyl sulfide.
A significant advantage of the described procedure to
access OEHCSs (Scheme 1) over hydrolytic methods
using aqueous alcoholic media, which produce a 1 : 1 mixꢀ
ture of cyclic and linear products,5 is a selective formaꢀ
tion of cyclic products (in toluene, CHCl3, and MeCN).
We assumed that the reaction proceeds via intermediꢀ
ate formation of ethyl(hydro)silanone, which further
underdoes cyclomerization to give ethyl(hydro)cycloꢀ
siloxanes (Scheme 2).
Scheme 1
n = 3—8
Scheme 2
n = 3—8

906
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 5, May, 2017
Basenko and Maylyan
In MeCN, cyclic D3 is the major product with the
In MeCN, formation of ethyl(hydro)silanone is apꢀ
parently accompanied with side reaction, namely, proꢀ
duction of chloro(ethyl)silanone inserted further into
D2—D7 (Scheme 4).
Formation of linear α,ωꢀdiethoxyoligoethyl(hydro)ꢀ
siloxanes (EtO(EtSiHO)nEt, n = 2—7) can apparently be
rationalized in terms of the insertion of ethyl(hydro)ꢀ
silanone into the C—O bond of the diethyl ether moleꢀ
cule (Scheme 5). This suggestion is also supported by the
absence of nonꢀsymmetrical compounds and products
heaving an odd number of the ethoxy groups.
The main peculiarities of the fragmentation patterns
of OEHCSs and CMCSs (see Tables 1 and 2) agree well with
those for the previously studied cyclosiloxanes.18,19 For
α,ωꢀdiethoxyoligoethyl(hydro)siloxanes (EtO(EtSiHO)nEt,
n = 2—7) (see Table 3), fragmentation also occurs with
either retention or cleavage of the siloxane skeleton. No
molecular ions were detected for all studied compounds.
Note that this is a characteristic feature of the fragmentaꢀ
tion pattern of siloxanes bearing the Si—H bonds.18
In summary, we found that the reaction of EtSi(H)Cl2
with DMSO can proceed unexpectedly and the reaction
pathway is predetermined by the nature of the organic
solvent used.
yield of ~27%; the yield of D4 does not exceed 18%. The
unexpected feature of this reaction is the formation of
CMCSs. It is of note that 1ꢀchloroꢀ1,3,5ꢀtriethylcycloꢀ
trisiloxane is formed in trace amounts, which is apparꢀ
ently due to small amount of 1,3ꢀdiethyldi(hydro)ꢀ
cyclodisiloxane present in the reaction mixture. Intermeꢀ
diate formation of the latter compound has been suggestꢀ
ed earlier by Le Roux et al.13 The ratio of 1ꢀchloroꢀ
1,3,5,7ꢀtetraethylcyclotrisiloxane to compound D4 in the
reaction mixture is 1 : 2. The ratio of the other cyclic
monochlorinated siloxanes to nonꢀchlorinated derivatives
(D5—D8) is ~1 : 1 (Scheme 3). The overall yield of
CMCSs is approximately 30%.
Scheme 3
n = 3—8
Earlier,17 gas chromatography—mass spectrometry
studies of the products of the hydrolysis of EtSi(H)Cl2 in
both benzene and butanol indicated the presence of trace
amounts of CMCSs. No formation of 1,3,5ꢀtriethylꢀ1ꢀ
chlorocyclotrisiloxane was detected.
Experimental
Electron impact (70 eV) mass spectrometry was carried out
with a Shimadzu GCMSꢀQP5050A quadrupole mass spectromꢀ
Scheme 4
n = 2—7
Scheme 5
n = 3—8, m = 2—7
n = 2—7

Unexpected reactions ethyl(hydro)dichlorosilane
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 5, May, 2017
907
eter using helium as carrier gas, the injector temperature was
200—250 °C, and the detector temperature was 200 °C. The
studied compounds were resolved by gas chromatography on
a capillary column SPBꢀ5 (60 m×0.25 mm×25 μm), carried gas
was helium, flow rate of the carrier gas was 0.7 mL min–1, the
evaporator temperature was 230 °C, the ion source temperature
was 200 °C, pressure was 280 kPa, temperature was programmed
3. M. G. Voronkov, V. M. Mararskaya, Appretirovanie tekꢀ
stil´nykh meterialov kremniiorganicheskimi monomerami i
oligomerami [Treatment of Fabrics with Organosilicon Monoꢀ
mers and Oligomers], Nauka, Novosibirsk, 1978, 78 pp.
(in Russian).
4. R. Okawara, E. Asada, T. Watase, Bull. Chem. Soc. Jpn.,
1953, 26, 141.
as follows: heating from 60 to 250 °C with rate of 10 deg min–1
.
5. N. N. Sokolov, S. M. Akimoova, Zh. Org. Khim., 1956, 26,
2276 [J. Org. Chem. USSR (Engl. Transl.), 1956, 26].
6. J. Li, F. Li, J. Li, CN Pat. 104292253; CAN 162:273038.
7. T. L. Krasnova, N. A. Mudrova, V. N. Bochkarev, A. V.
Kisin, Zh. Org. Khim., 1985, 55, 1528 [J. Org. Chem. USSR
(Engl. Transl.), 1985, 55].
Commercially available dichloro(ethyl)silane was distilled
prior to use. Dimethyl sulfoxide was dried over melted KOH,
decanted, freezeꢀdried, and distilled under vacuum. Physicoꢀ
chemical properties of dichloro(ethyl)silane and DMSO was in
agreement with those given in literature.
Reaction of dichloro(ethyl)silane with DMSO. The reaction
was carried out in a threeꢀneck flask equipped with a refluxing
condenser under an argon atmosphere. A solution of DMSO
(7.8 g, 0.1 mol) in chloroform (15 mL) was slowly (over 1 h)
added to a solution of dichloro(ethyl)silane (12.8 g, 0.1 mol) in
chloroform (15 mL) at 0 °C. The mixture was stirred for 4 h.
Distillation gave 8.5 g (86%) of chloromethyl methyl sulfide,
b.p. 110—111 °C (cf. Ref. 20: b.p. 110—112 °C). Conversion of
dichloro(ethyl)silane was 95%.
Distillation of the bottom fraction under vacuum gave 2.7 g
(36%) of 1,3,5ꢀtriethylcyclotrisiloxane, b.p. 69—70 °C (20 Torr)
(cf. Ref. 21: b.p. 67 °C (20 Torr)) and 3.0 g of a fraction with
b.p. 60—175 °C (2 Torr). The gas chromatography—mass
spectrometry analysis data for this fraction are given in Table 1.
Reactions of EtSi(H)Cl2 with DMSO (a molar ratio of 1 : 1)
in toluene, diethyl ether, and MeCN were carried out similarly.
The gas chromatography—mass spectrometry analysis data are
summarized in Tables 1—3.
8. V. I. Lavrent´ev, B. G. Kostrovskii, Izv. SO AN SSSR. Ser.
Khim. [Bull. Siberian Division of Akad. Sci. USSR, Div. Chem.
Sci.], 1979, 5, 134 (in Russian).
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500, 325.
11. M. G. Voronkov, S. V. Basenko, Silanons. Ot efemerov k
monomeram, oligomeram i polimeram [Silanones. From
Ephemera to Monomers, Oligomers, and Polymers], Geo,
Novosibirsk, 2014, 142 (in Russian).
12. J.ꢀC. Goossens, French Pat. 1456981; Chem. Abstrs, 1967,
67, 54259.
13. P. Lu, J. K. Paulasaari, W. P. Weber, Organometallics, 1996,
15, 4649.
14. C. Le Roux, H. Yang, S. Wenzel, S. Grigoras, M. A. Brook,
Organometallics, 1998, 17, 556.
15. T. H. Chan, A. Melnyk, D. H. Harpp, Tetrahedron Lett.,
1969, 10, 201.
The main experimental results were obtained on the
equipment of the Baikal Analytical Center for Collective
Use of the Siberian Branch of the Russian Academy of
Sciences.
The authors are grateful to V. P. Fedyanina for his
help in performing the experiments.
16. R. A. Benkeser, Chem. Eng. News, 1978, 56, 107.
17. S. V. Basenko, A. S. Soldatenko, M. G. Voronkov, Dokl.
Chem., 2013, 451, 203.
18. V. I. Lavrent´ev, V. G. Kostrovskii, Zh. Org. Khim., 1980,
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