D.S. Fattakho6a et al. / Journal of Organometallic Chemistry 613 (2000) 170–176
175
R SiCl to R SiꢀO and then to stable products occurs
3.3. Chemicals
2
2
2
under very mild conditions and can be realized in both
divided and undivided cells. All this allows us to believe
this process to be a very promising method for the
generation of diorganylsilanones. Further study in this
direction is in progress.
Analytical grade THF was additionally purified by
passing through a column packed with activated neu-
tral Al O , twice distilled from Na and then stocked
2
3
under argon over 4A molecular sieves. The supporting
electrolyte (Bu NBF , Aldrich) was kept in a vacuum
4
4
desiccator over P O . Oxygen, dried by passing consec-
2
5
3. Experimental
utively through H SO (conc.), P O and Al O , was
2
4
2
5
2
3
bubbled into the solution through a porous glassy
sprayer. Before using, diorganyldichlorosilanes were
purified by distillation from Mg turnings, HMDS was
distilled from Na. Linear and cyclic permethy-
loligosiloxanes (standards) were synthesized according
to a described method [53].
3
.1. Instrumentation
Large-scale electrolyses were carried out using a po-
tentiostat P-5827M. The working electrode (cathode)
was a Pt gauze cylinder with an apparent area of 37 cm,
the auxiliary electrode (anode) was a Pt (in a divided
cell) or Al (in an undivided cell) wire. The reference
electrode was Ag/0.1 M AgNO in CH CN, separated
Hexamethylcyclotrisiloxane. NMR (CDCl , TMS):
3
+
0
.17 (s 18H). Mass, m/e: 207 (M −15, 100), 191 (15),
3
3
1
77 (5), 133 (10), 96 (15).
from the working solution by an electrolytic bridge
filled with 0.01 M Bu NBF solution in THF. A 30 ml
Octamethylcyclotetrasiloxane. NMR (CDCl , TMS):
3
4
4
+
0
2
.14 (s 24H). Mass, m/e: 281 (M −15, 100), 265 (10),
hermetic glass cell, equipped with a jacket for cooling
the electrolyte with flowing water, was used; the anodic
and the cathodic compartments of this cell were sepa-
rated by a sintered glass diaphragm with medium
porosity. Chromatographic analysis of the reaction
mixture was carried out using a chromatograph
Chrom-5 fitted with a thermo-conductivity detector and
a column of 240×0.3 cm, filled with SE-30 (5%) on
Inerton 0.125–0.160; the carrier gas was He. The sam-
pler temperature was set at 230°C, the thermostat at
49 (5), 207 (15), 191 (10), 133 (10), 73 (8).
Hexaethylcyclotrisiloxane. NMR (CDCl3, TMS):
+
0
2
1
.52 (quad 12H), 0.92 (t 18H). Mass, m/e: 277 (M −
9, 100), 249 (88), 221 (72), 193 (30), 163 (30), 165 (28),
37 (30), 110 (28), 96 (20).
Octamethyltrisiloxane. NMR (CCl , TMS): 0.15 (s
4
+
1
8H), 0.19 (s 6H). Mass, m/e: 221 (M −15, 58), 205
(
8), 147 (5), 133 (12), 103 (20), 73 (100), 59 (15).
Decamethyltetrasiloxane. NMR (CCl , TMS): 0.08 (s
4
+
1
8H), 0.03 (s 12H). Mass, m/e: 295 (M −15, 22), 221
9
5°C, and detector at 150°C. As an internal standard,
(
40), 147 (48), 73 (100).
either n-octane or n-nonane was used, depending on
the boiling points of the products of the electrolysis.
Mass spectra were obtained using a MC-2040 spec-
trometer with the ionization energy 70 eV. NMR spec-
tra were recorded using a Varian-100 or Bruker-250
spectrometer.
Hexaphenylcyclotrisiloxane. NMR (CDCl , TMS):
3
7
5
.58 (d 12H), 7.35 (m 18H). Mass, m/e: 594 (8, M+),
16 (15), 439 (100), 361 (30), 219 (45), 197 (30), 144
(
30), 131 (40), 77 (35).
3.2. General procedure
References
Prior to the main electrolysis (before bubbling oxy-
gen through the catholyte), pre-electrolysis of the solu-
tion of diorganyldichlorosilanes was carried out to
[
[
1] L.E. Gusel’nikov, N.S. Nametkin, V.M. Vdovin, Usp. Khim. 52
(1974) 1317.
2] L.E. Gusel’nikov, N.S. Nametkin, V.M. Vdovin, Acc. Chem.
Res. 8 (1975) 18.
3] L.E. Gusel’nikov, N.S. Nametkin, Chem. Rev. 79 (1979) 529.
4] J. Raabe, J. Michl, Chem. Rev. 85 (1985) 419.
5] A.K. Maltsev, V.N.Khabashesku, O.N. Nefedov, in: E.R. Corey,
J.Y.Corey, P.P. Gaspar (Eds.), Silicon Chemistry, Wiley, New
York, 1987, pp. 211–224.
6] V.N. Khhabashesku, Z.A. Kerzina, A.K. Maltsev, O.N. Nefe-
dov, J. Organomet. Chem. 364 (1989) 301.
7] V.A. Radtsig, I.V. Berestetskaya, S.N. Kostritsa, Kinetics Catal.
39 (1998) 863.
reduce protons resulting from the hydrolysis of R SiCl2
2
[
[
[
by traces of water. The pre-electrolysis was realized in a
constant-current mode (I=50 mA) until the evolution
of bubbles of hydrogen at the cathode stopped; average
duration of the pre-electrolysis was 1.5
approximately.
h
[
[
In a typical experiment, the catholyte contained 10
mmol of R SiCl , 0.65 g (4 mmol) HMDS, 0.5 g (4
2
2
mmol) of octane, used as an internal standard for
chromatography, and 2.64 g (7 mmol) Bu NBF in 20
ml of THF. The electrolyses were carried out in gal-
vanostatic mode maintaining the current at 20–50 mA
[8] V.N. Khabashesku, Z.A. Kerzina, K.N. Kudi, O.M. Nefedov, J.
Organomet. Chem. 566 (1998) 45.
4
4
[
9] M.G. Voronkov, J. Organomet. Chem. 557 (1998) 143.
[
[
10] M.G. Voronkov, Izv. Acad. Nauk Ser. Khim. (1998) 824.
11] E.A. Chernyshev, T.L. Krasnova, N.A. Mudrova, A.V.
Golovkin, M.G. Kuznetsova, Zh. Obshch. Khim. 57 (1987)
1725.
(
at the electrode given) and the flow of dry oxygen
−
1
through the solution at 10 ml min
.