1,1,2,2-Tetramethyl-3-trimethylsilyl-1,2-disilacyclobutane: Synthesis and spontaneous polymerization

Article abstract of DOI:10.1007/s11172-013-0211-1

Gas-phase dehalogenation of 1,2-bis[chloro(dimethyl)silyl]-2- trimethylsilylethane with alkali metals gave 1,1,2,2-tetramethyl-3- trimethylsilyl-1,2-disilacyclobutane (3). Its spontane- ous ring-opening polymerization at room temperature afforded an amorp

Full text of DOI:10.1007/s11172-013-0211-1

1
462
Russian Chemical Bulletin, International Edition, Vol. 62, No. 6, pp. 1462—1464, June, 2013
1
,1,2,2ꢀTetramethylꢀ3ꢀtrimethylsilylꢀ1,2ꢀdisilacyclobutane:
synthesis and spontaneous polymerization
L. E. Gusel´nikov,a† V. V. Volkova, E. N. Buravtseva, N. V. Ushakov,
a†
a
a
b
b
b
V. G. Lakhtin, L. A. Parshkova, and E. A. Chernyshev
aA. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences,
2
9 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 633 8520. Eꢀmail: ushakov@ips.ac.ru
b
State Research Institute of Chemical Technology of Organoelement Compounds,
3
8 sh. Entuziastov, 111123 Moscow, Russian Federation.
Eꢀmail: chteos@yandex.ru
Gasꢀphase dehalogenation of 1,2ꢀbis[chloro(dimethyl)silyl]ꢀ2ꢀtrimethylsilylethane with
alkali metals gave 1,1,2,2ꢀtetramethylꢀ3ꢀtrimethylsilylꢀ1,2ꢀdisilacyclobutane (3). Its spontaneꢀ
ous ringꢀopening polymerization at room temperature afforded an amorphous linear polymer
5
5
with T = –8.9 C, M = 3.47•10 —3.85•10 , and M /M = 2.43—2.86. According to spectroꢀ
g
w
w
n
1
13
29
scopic data (IR and H, C, and Si NMR), the backbone of the polymer consists of alternatꢀ
ing monomer units joined in the "headꢀtoꢀtail" ([Me SiCH(SiMe )CH SiMe SiMe CHꢀ
2
3
2
2
2
(
(
SiMe )CH SiMe ]) and "headꢀtoꢀhead" ways ([Me SiCH CH(SiMe )SiMe SiMe CHꢀ
3 2 2 2 2 3 2 2
SiMe )CH SiMe ]).
3
2
2
Key words: 1,1,2,2ꢀtetramethylꢀ3ꢀtrimethylsilylꢀ1,2ꢀdisilacyclobutane, spontaneous polyꢀ
merization, organosilicon compounds.
The lower homologs of the 1,2ꢀdisilacyclobutane
1,2ꢀDSCB) series are highly reactive and not easily acꢀ
merty effect due to the presence of the Me Si group in the
3
(
monomer unit on the properties of the resulting polymer,
here we synthesized 1,1,2,2ꢀtetramethylꢀ3ꢀtrimethylsilylꢀ
1,2ꢀdisilacyclobutane (3) and examined its spontaneous
polymerization.
cessible. The synthesis and study of these monomers were
made possible by development of gasꢀphase dehalogenaꢀ
tion of 1,2ꢀbis[chloro(dimethyl)silyl]ethane with the alꢀ
kali metal vapors, which allows stabilization of the resultꢀ
ing 1,1,2,2ꢀtetramethylꢀ1,2ꢀdisilacyclobutane (1) in a trap
cooled to 77 K. When kept at room temperature, comꢀ
pound 1 undergoes spontaneous exothermic ring opening
via homolytic cleavage of the Si—Si bond followed by
spontaneous polymerization.1—4 A reaction of styrene with
compound 1 yields a copolymer by the free radical mechꢀ
Results and Discussion
Compound 3 was obtained in three steps (Scheme 1).
Scheme 1
4
1—4
anism. Continuing our investigations,
nearest higher homolog of compound 1, viz., 1ꢀethylꢀ
,2,2ꢀtrimethylꢀ1,2ꢀdisilacyclobutane (2), and studied its
we obtained the
1
spontaneous polymerization and copolymerization with
5
monomer 1. It turned out that such a configuration of
substituents at the Si atoms (one ethyl and three methyl
groups) makes compound 2 substantially less reactive in
spontaneous roomꢀtemperature polymerization compared
to tetramethyl derivative 1: the time required for complete
conversion into the polymer increases from a few minutes
to a week. To study the effect of the Me Si group at an
3
endocyclic C atom on the reactivity of 1,2ꢀDSCB in sponꢀ
taneous polymerization as well as to estimate the asymꢀ
The first two steps were implemented as described earꢀ
lier.6,7 The last step presented few problems when the reacꢀ
†
Deceased.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1462—1464, June, 2013.
066ꢀ5285/13/6206ꢀ1462 © 2013 Springer Science+Business Media, Inc.
1

3
ꢀTrimethylsilylꢀ1,2ꢀdisilacyclobutane
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 6, June, 2013
1463
tion conditions were similar to those used previously for
the synthesis of compound 2. We found nearly optimum
conditions for gasꢀphase dehalogenation of 1,2ꢀbis[chloroꢀ
an elastomer with the glass transition temperature T =
g
= –8.9 C (DSC data). The amorphism of polymer 5 is
obviously due to the structural asymmetry of monomer 3.
Its polymerization produces a macromolecule containing
blocks formed by two types of linkage between monomer
units: "headꢀtoꢀtail" (A) and "headꢀtoꢀhead" (B). This in
turn ensures the diastereomerism of the units in the blocks,
(
dimethyl)silyl]ꢀ2ꢀtrimethylsilylethane (4) in a vacuum
4
,5
system. Slow supply of the vapor of compound 4 to
a reaction tube is crucial for the success of this synthesis
because a constant low pressure (0.1—0.5 Torr) and a conꢀ
stant temperature (270±5 C) in the reaction zone are
thus ensured. When these conditions are met, the dehaloꢀ
genated product collected in cooled tubes is virtually indiꢀ
vidual compound 3 obtained in 45—52% yield. Strict obꢀ
servation of the above conditions for gasꢀphase dehalogeꢀ
nation is dictated by the fact that compound 3 cannot be
purified by additional distillation (its boiling and melting
points are substantially higher than those of disilacycloꢀ
butanes 1 and 2): even when flowing down into a cooled
tube upon thawing, compound 3 already undergoes partial
polymerization. Furthermore, this precluded us from reꢀ
cording its NMR spectrum. Sealed tubes with compound 3
were kept in liquid nitrogen before use. The mass specꢀ
trum of monomer 3 contains a considerable molecular ion
peak with m/z 216 (33.5%), the most intense peak with
depending on whether two neighboring Me Si groups are
3
on the same side or on opposite sides of the polymer backꢀ
bone (see Scheme 2).
The structure of polymer 5 was determined by IR specꢀ
1
13
29
troscopy and H, C, and Si NMR spectroscopy. The
–
1
IR spectrum shows intense bands at 1130 and 1017 cm
(SiCHCH Si), a band at 1252 cm with a shoulder at
1258 cm and a band at 834 cm with a shoulder at
815 cm (SiMe and SiMe ), bands at 725 and 608 cm
–
1
2
1
–
–1
–1
–1
2
3
(Si—C bending vibrations), and very weak (though beꢀ
coming pronounced upon magnification) bands at 433,
–
1
418, and 409 cm (Si—Si stretching vibrations).
Because each monomer unit in polymer 5 contains
four types of protons (SiMe , SiMe , CH , and CH), we
3
2
2
1
would expect four resonance lines in its H NMR specꢀ
trum, with an integral intensity ratio of 9 : 12 : 2 : 1, reꢀ
spectively. In fact, the H NMR spectrum of polymer 5
+
m/z 201 (100%, [M – Me] ), and intense peaks with m/z
+
1
1
[
42 (89.5%), 141 (62.3%), and 127 (93.6%): [M – HSiMe ] ,
3
+
+
M – HSiMe – H] , and [M – Me – HSiMe ] , resꢀ
shows two intense signals at  0.20 and 0.28 (SiMe) and
3
3
pectively. The intensity of the peak with m/z 73 (Me Si) is
a signal at  1.01 (CH ); the integral intensity ratio of the
3
2
9
0.2%.
After warming of the tube with monomer 3 to room
temperature, a noticeable exothermic process began. After
40—45 min, immobile polymer 5 was obtained in 83—92%
first two signals to the last one is 11 : 1. Obviously, the line
due to the CH proton is masked by the intense signals for
the protons of the SiMe groups.
~
The quantitative 13C NMR spectrum contains a group
5
5
yield (M = 3.47•10 —3.85•10 , M /M = 2.43—2.86)
of lines at  9.04 (CH Si), a group of lines at  3.52 (CH),
w
w
n
2
(
Scheme 2). Therefore, the presence of such a bulky group
an intense signal at  –0.13 (Me Si), and five signals at
3
as Me Si at a carbon atom of the 1,2ꢀDSCB ring decreasꢀ
 0.14, –1.52, –2.60, –2.72, and –3.65 (Me Si). This
3
2
es polymerization reactivity to a lesser extent than does
the presence of a bulkier substituent at a silicon atom. As
a result, the tendency of compound 3 toward spontaneous
polymerization is much closer to that of compound 1 rather
than 2. This agrees with the fact that spontaneous polyꢀ
merization of lower 1,2ꢀDSCB homologs follows the freeꢀ
radical mechanism involving cleavage of the Si—Si bond.
Polymer 5 is well soluble in common organic solvents.
Its backbone consists of alternating dimethylsilylꢀ
ene (Me Si—SiMe ) and trimethylsilylethylene units
magnetic nonequivalence of the Me Si groups suggests
2
that the backbone of polymer 5 consists of a random seꢀ
quence of segments of different lengths that follow the
"headꢀtoꢀtail" (A) and "headꢀtoꢀhead" (B) linkage patꢀ
terns (see Scheme 2). The presence of three silicon atoms
in each monomer unit of polymer 5 is confirmed by its
29
quantitative Si NMR spectrum (short pulse (30%), a long
relaxation delay, and proton decoupling) containing three
lines of equal intensity at  2.97 (SiMe ), –13.80, and
3
–16.46 (SiMe ). The spectra of polymer 5 exhibit no signals
2
2
2
(
CH CHSiMe ); i.e., it is formally an alternating copolyꢀ
unique to the nuclei in either the block A or B, which
2
3
mer of tetramethyldisilylene and trimethyl(vinyl)silane and
precludes determination of a precise ratio of these blocks.
Scheme 2

1
1
464
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 6, June, 2013
Gusel´nikov et al.
To sum up, like 1,1,2,2ꢀtetramethylꢀ and 2ꢀethylꢀ
,1,2ꢀtrimethylꢀ1,2ꢀdisilacyclobutanes, 1,1,2,2ꢀtetrameꢀ
highly exothermic polymerization began after thawing of the
monomer at room temperature. The mobile liquid became thickꢀ
er to give, in a period of 45 min, a clear rubbery mass. The tube
was opened, and its contents was dissolved in toluene. Polymer 5
was precipitated with ethanol. The resulting precipitate was disꢀ
solved again, reprecipitated, washed with ethanol, and dried in a
vacuum desiccator at 50 C to a constant weight. Yield 0.64 g
thylꢀ3ꢀtrimethylsilylꢀ1,2ꢀdisilacyclobutane is highly reacꢀ
tive in spontaneous polymerization which involves ringꢀ
opening cleavage of the Si—Si bond to give an amorphous
highꢀmolecularꢀweight polymer.
(
89%). Found (%): C, 50.11; H, 10.98; Si, 39.17. (C H Si ) .
9 24 3 x
1
Experimental
Calculated (%): C, 49.92; H, 11.17; Si, 38.91. H NMR (CD3C6D5),
: 0.20 and 0.28 (both w, SiMe , SiMe , and SiCHSi); 1.01

(
0
3
2
13
w, CH2). C NMR (CD C D ), : –3.65, –2.72, –2.60, –1.52,
1H, 13C, and 29Si NMR spectra were recorded on a Bruker
DPXꢀ400 spectrometer (400, 100.6, and 79.5 MHz, respectiveꢀ
3 6 5
2
9
.14 (Me Si); –0.13 (SiMe ); 3.52 (CH); 9.04 (CH ). Si NMR
2 3 2
(
CD C D ), : –16.46 (SiMe ); –13.80 (SiMe ); 2.97 (SiMe ).
3 6 5 2 2 3
ly) at 50—60 C for saturated solutions of polymer 5 in deuteratꢀ
–
1
as
as
s
IR, /cm : 2936 ( (Me)); 2883 (sh 2854) ( CH ;  Me);
2
(
7
5
ed toluene (C = 0.5—0.6 mol L–1). Mass spectrum (EI) was
2
s
s
808 ( CH ); 1252 (sh 1258) ( MeSi); 1190; 1130, 1017
2
measured on a Finnigan 4021 GC/MS instrument. IR spectra
were recorded on Specord Mꢀ80 and SPꢀ1200 instruments in the
SiCH CHSi); 965; 936; 858; 834 (sh 815) (SiMe and SiMe );
2
2
3
80; 740; 725 (Si—C)); 699; 680; 660; 644; 608 ((Si—C));
70; 433, 418, 409 ((Si—Si)).
–
1
4
00—3600 cm range. The molecular mass distribution of the
polymer was determined by gel permeation chromatography on
a Watersꢀ200 instrument in toluene at 25 C (flow rate 1.0 mL
min , three ultrastyragel columns with sorbent pore sizes of
–
1
References
1
00, 500, and 1000 Å). The instrument was calibrated against
polystyrene standards. The glass transition temperature was meaꢀ
sured on a Mettler TAꢀ4000 differential scanning calorimeter
with a DSCꢀ30 heating cell (heating rate 20 deg min– , argon).
Freshly distilled toluene and ethanol were used for dissoluꢀ
tion, precipitation, and washing of samples of the polymer.
1
. L. E. Gusel´nikov, Yu. P. Polyakov, N. S. Nametkin, Dokl.
Akad. Nauk SSSR, 1980, 253, 1133 [Dokl. Chem. (Engl. Transl.),
1
1
980, 253, No. 5].
2
3
. USSR Inventor´s Certificate 810701; Byull. Izobret., 1981, 9;
Chem. Abstr., 1980, 93, 150372g.
. Yu. P. Polyakov, L. E. Gusel´nikov, T. S. Yadritseva, S. S.
Bukalov, L. A. Leites, Vysokomol. Soedin., Ser. A, 1995, 17,
1
,1,2,2ꢀTetramethylꢀ3ꢀtrimethylsilylꢀ1,2ꢀdisilacyclobutane
(
3). Dehalogenation of compound 4 (preꢀdegassed in vacuo) with
the alkali metal vapors was carried out in a flow vacuum system
9
55 [Polym. Sci., Ser. A (Engl. Transl.), 1995, 17].
4
according to a known procedure. A tube with compound 4 was
4
5
. L. E. Gusel´nikov, V. V. Volkova, E. A. Volnina, N. K. Gladꢀ
kova, V. V. Negrebetsky, M. Blazso, J. Inorg. Organomet.
Polym., 1998, 8, 89.
. L. E. Gusel´nikov, E. N. Buravtseva, N. V. Ushakov, V. G.
Lakhtin, L. A. Parshkova, N. A. Kuyantseva, E. A. Chernyꢀ
shev, Russ. Chem. Bull. (Int. Ed.), 59, 1376 [Izv. Akad. Nauk,
Ser. Khim., 2010, 1347].
heated in such a way that its vapor was supplied to the reaction
tube over a K/Na melt (270 C, 0.1 Torr). The supply rate was
regulated so that the reaction temperature was no higher than
275 C and the pressure was no higher than 0.5 Torr. The dechlorꢀ
ination product (individual monomer 3) was collected in a flow
trap cooled with liquid nitrogen. Careful heating of the trap
allowed the monomer to flow down into calibrated tubes, which
were sealed and kept in liquid nitrogen before use. In a typical
experiment, the yield of individual disilacyclobutane 3 from
dichloride 4 (4.62 g) was 1.62 g (48.7%). Found (%): C, 49.80;
6
7
. V. D. Sheludyakov, V. G. Lakhtin, V. I. Zhun´, V. V. Shcherꢀ
binin, E. A. Chernyshev, Zh. Obshch. Khim., 1981, 51, 1829
[
J. Gen. Chem. USSR (Engl. Transl.), 1981, 51, No. 8].
. V. D. Sheludyakov, A. I. Korshunov, V. G. Lakhtin, V. S.
Timofeev, T. F. Slyusarenko, V. M. Nosova, E. V. Gradova,
Zh. Obshch. Khim., 1986, 56, 2743 [J. Gen. Chem. USSR
H, 10.95; Si, 39.23. C H Si . Calculated (%): C, 49.92; H, 11.17;
9
24
3
+
Si, 38.91. MS (EI, 70 eV), m/z (Irel (%)): 216/217/218 [M]
33.5/7.8/3.9), 201/202/203 [M – Me]+ (100/23.1/12.2),
73 (15.3), 145 (7.2), 144 (11.3), 143 [M – SiMe ] (37.7), 142
M – HSiMe3] (89.5), 141 [M – HSiMe – H] (62.3), 127
(
1
[
[
[
(
Engl. Transl.), 1986, 56, No. 12].
+
3
+
+
3
+
M – Me – HSiMe ] (93.6), 115 (10.1), 85 (5.8), 73/74/75
3
+
SiMe ] (90.2), 59 (31.6), 45 (10.1), 43 (8.0).
3
Polymer 5. A sealed tube containing compound 3 (0.72 g,
.3 mmol) was withdrawn from liquid nitrogen. Spontaneous,
Received July 17, 2012;
in revised form March 1, 2013
3