, 2001, 11(5), 195–196
Molecular structure of 1,3-dihydroxydecamethylcyclohexasilane
Alexander A. Korlyukov, Denis Yu. Larkin, Nina A. Chernyavskaya,* Mikhail Yu. Antipin and
Alexey I. Chernyavskii
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow, Russian Federation.
Fax: +7 095 135 5085; e-mail: chern@ineos.ac.ru
10.1070/MC2001v011n05ABEH001484
As found by X-ray diffraction analysis, oxygen atoms in the molecule of 1,3-dihydroxydecamethylcyclohexasilane occupy axial
positions.
C(9)
Bifunctional cyclosilanes are valuable starting compounds for the
synthesis of polycyclic silanes and cyclolinear copolymers con-
C(5)
taining cyclosilane units. It was found earlier1,2 that the interac-
C(8)
C(2)
tion of dodecamethylcyclohexasilane (Me2Si)6 with SbCl5 in a
CCl4 solution yields dichloro-substituted cyclohexasilanes, which
are a mixture (in a ratio of ~1:1) of structural isomers, 1,3-di-
chlorocyclohexasilane 1 and 1,4-dichlorocyclohexasilane 2. These
isomers should be separated for their use as starting compounds
for the synthesis of polymers or copolymers. Structural isomers
1 and 2 have similar physico-chemical properties; therefore, they
can be separated by only chemical methods.2–4 The simplest
method is the hydrolysis of an isomeric mixture of 1 and 2
followed by the separation of reaction products 3 and 4 by
vacuum distillation (Scheme 1).4 The treatment of hydrolysis
products 3 and 4 with acetyl chloride leads to dichloro-substi-
tuted cyclosilanes 1 and 2 in quantitative yields. The X-ray dif-
fraction analysis of the hydrolysis products of compound 2
demonstrated4 that a unit cell contains both bridged compound
4 and 1,4-dihydroxycyclosilane 5 in a ratio of 2:1. The X-ray
data for compound 3 were not reported.
Si(6)
Si(5)
Si(4)
C(6)
C(10)
C(4)
C(1)
Si(1)
Si(2)
Si(3)
C(7)
C(3)
O(1)
O(2)
Figure 1 Molecular structure of 3. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å): Si(1)–O(1) 1.671(3), Si(1)–Si(6) 2.346(3),
Si(1)–Si(2) 2.350(2), Si(2)–Si(3) 2.353(3), Si(3)–O(2) 1.663(3), Si(3)–Si(4)
2.349(2), Si(4)–Si(5) 2.334(2), Si(5)–Si(6) 2.334(2), Si–C 1.872–1.897;
selected bond angles (°): O(1)–Si(1)–C(1) 106.7(1), O(1)–Si(1)–Si(6) 107.6(1),
C(1)–Si(1)–Si(6) 111.8(1), O(1)–Si(1)–Si(2) 111.04(7), O(2)–Si(3)–C(4)
107.0(1), O(2)–Si(3)–Si(4) 110.42(6), O(2)–Si(3)–Si(2) 109.59(6), Si(1)–
Si(2)–Si(3) 115.47(3), Si(4)–Si(3)–Si(2) 111.63(3), Si(5)–Si(4)–Si(3) 112.73(3),
Si(6)–Si(1)–Si(2) 111.35(3), Si(5)–Si(6)–Si(1) 108.5(1); torsion angles (°):
Si(1)–Si(2)–Si(3)–Si(4) 45.33(2), Si(2)–Si(3)–Si(4)–Si(5) –46.18(4), Si(3)–
Si(4)–Si(5)–Si(6) 55.35(2), Si(4)–Si(5)–Si(6)–Si(1) –59.68(4), Si(2)–Si(1)–
Si(6)–Si(5) 56.42(4), Si(6)–Si(1)–Si(2)–Si(3) –51.52(4).
We determined the molecular and crystal structure of 3 by
X-ray diffraction analysis.‡ The six-membered cyclosilane ring
exhibits a chair conformation (Figure 1). The oxygen atoms O(1)
and O(2) occupy axial positions. The positions of the oxygen
atoms O(1) and O(2) may be described as cis; the correspond-
ing pseudotorsion angle O(1)Si(1)Si(3)O(2) is equal to –8.0°. It
is noteworthy that, in the molecule of 5, similar oxygen atoms
occupied the trans positions.4 The bond lengths and bond angles
are close to those in the majority of similar compounds.5 The
Si(4)–Si(5) and Si(5)–Si(6) bonds in 3 are shorter than others.
The elongation of the other Si–Si bonds may be explained by
an anomeric effect (n–σ * interaction between oxygen lone pairs
and vacant orbitals of the Si–Si bonds). The disordering of the
‡
Crystallographic data for 3: C10H32O2Si6, M = 352.90, F(000) = 1536,
monoclinic crystals, space group C2/c, a = 17.662(4) Å, b = 10.066(2) Å,
c = 26.040(5) Å, b = 107.09(3)°, V = 4425(2) Å3, Z = 8, dcalc = 1.059 g cm–3,
m(MoKα ) = 0.372 mm–1. Intensities of 5460 reflections were measured
with a Siemens P3/PC diffractometer at ambient temperature [l(MoKα ) =
Scheme 1
We reproduced the method4 of separation of hydrolysis pro-
ducts by vacuum distillation, but dihydroxy derivative 3 was
obtained in a low yield (< 10%), probably, due to its condensa-
tion during distillation. We obtained compound 3 in 48% yield
by partial crystallization of hydrolysis products.†
= 0.71072 Å, q/2q scan, 2q < 56°], and 5285 independent reflections (Rint
=
= 0.0277) were used in a further refinement. The structure was solved by
a direct method and refined by the full-matrix least-squares technique
against F2 in the anisotropic–isotropic approximation. Hydrogen atoms
were located from the Fourier synthesis and refined in the isotropic
approximation. An analysis of the Fourier electron density synthesis
revealed additional maxima in the regions of shortest intermolecular
O···O contacts, which were interpreted as a disorder of hydroxyl groups
[H(1), H(1') and H(2), H(2')]. The refinement converged to wR2 =
= 0.1038 and GOF = 0.938 for all independent reflections [R1 = 0.0315
was calculated against F for 4512 observed reflections with I > 2s(I)].
All calculations were performed using SHELXTL-97 V5.106 on an IBM
PC. Atomic coordinates, bond lengths, bond angles and thermal param-
eters have been deposited at the Cambridge Crystallographic Data
Centre (CCDC). For details, see ‘Notice to Authors’, Mendeleev Commun.,
Issue 1, 2001. Any request to the CCDC for data should quote the full
literature citation and the reference number 1135/97.
†
12.0 g (0.034 mol) of an isomeric mixture of 1 and 2 in 100 ml of
pentane, which was obtained by the interaction of 20.0 g (0.052 mol) of
(Me2Si)6 with 23.6 g (0.079 mol) SbCl5, was added dropwise to a mix-
ture of 40 ml (0.45 mol) of H2O and 15.8 g (0.157 mol) Et3N in 100 ml
of pentane. The precipitate of Et3N·HCl was filtered off. The organic
solvent and an excess of Et3N and H2O were removed in vacuo at room
temperature. Compound 3 was obtained by partial crystallization of the
residue from pentane. Yield 2.6 g (48% on a 1 basis), mp 124–126 °C.
MS, m/z (%): 334 (11.9) [M – H2O]+, 319 (4.2) [M – H2O – Me]+, 293
(13.0), 259 (18.5), 245 (12.8), 217 (13.5), 189 (13.0), 175 (18.1), 147
(14.4), 117 (40.6), 73 (100) [SiMe3]+.
– 195 –