On some reactions of undecamethylcyclohexasilanyl-substituted silanes

Article abstract of DOI:10.1016/S0022-328X(99)00702-0

A number of undecamethylcyclohexasilanyl-substituted silanes have been prepared employing a salt elimination reaction between undecamethylcyclohexasilanyl potassium and several silyl halides or triflates. This method provides access to compounds with one or two undecamethylcyclohexasilanyl units attached to one silicon atom. Several attempts to introduce a third ring failed, resulting in formation of bis(undecamethylcyclohexasilanyl). An alternative approach to the substance class using silyl anions and undecamethylcyclohexasilanyl bromide was also developed. The molecular structure of bis(undecamethylcyclohexasilanyl)methylsilane was determined by X-ray crystallography.

Full text of DOI:10.1016/S0022-328X(99)00702-0

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 598 (2000) 202–210
On some reactions of undecamethylcyclohexasilanyl-substituted
silanes
Ulrich Englich c, Susanne Graschy a, Edwin Hengge a, Uwe Hermann b,
Christoph Marschner a,*, Christian Mechtler a, Erich Pinter a, Karin Ruhlandt-Senge c,
Frank Uhlig b
a Technische Uni6ersita¨t Graz, Institut fu¨r Anorganische Chemie, Stremayrgasse 16, A-8010 Graz, Austria
b Uni6ersita¨t Dortmund, Anorganische Chemie II, Otto-Hahn-Strasse 6, D-44221 Dortmund, Germany
c Department of Chemistry, Syracuse Uni6ersity, 1-014 Center of Science and Technology, Syracuse, NY, USA
Received 30 June 1999; accepted 10 November 1999
Dedicated to Professor Gerhard Roewer on the occasion of his 60th birthday.
Abstract
A number of undecamethylcyclohexasilanyl-substituted silanes have been prepared employing a salt elimination reaction
between undecamethylcyclohexasilanyl potassium and several silyl halides or triflates. This method provides access to compounds
with one or two undecamethylcyclohexasilanyl units attached to one silicon atom. Several attempts to introduce a third ring failed,
resulting in formation of bis(undecamethylcyclohexasilanyl). An alternative approach to the substance class using silyl anions and
undecamethylcyclohexasilanyl bromide was also developed. The molecular structure of bis(undecamethylcyclohexasi-
lanyl)methylsilane was determined by X-ray crystallography. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Cyclosilanes; NMR; X-ray structure
camethylcyclohexasilane with antimony pentachloride
[2]. Recently, we also found an easy access to alkali
cyclosilanyl derivatives, which were previously only ac-
cessible by a difficult and low-yielding route involving
mercury silanyl compounds [3].
1. Introduction
Since the first synthesis of bis(undecamethylcyclohexa-
silanyl)dimethylsilane in our laboratory we have been
interested in the chemistry of cyclosilanyl-substituted
silanes [1].
The first synthetic attempts focused on the restricted
availability of defined monosubstituted cyclohexasilanes
in reasonable quantities. Initially, treatment of dode-
camethylcyclohexasilane with HCl–AlCl3, which is not
a very selective process, was employed. Good results
were obtained only if the crude product of this reaction
was derivatized as phenylundecamethylcyclohexasilane,
which was converted in a second step into the chlorosi-
lane by means of reaction with hydrogen chloride [1].
Later, we reported on an improved synthesis of chloro-
undecamethylcyclohexasilane by treatment of dode-
2. Results and discussion
Undecamethylcyclohexasilanyl potassium (Si6Me11-
K), a highly suitable precursor for monosubstituted
cyclohexasilanes, can now be prepared by an effective
and high-yielding one-step procedure [3]. Treatment
with aqueous sulfuric acid gives the respective hydrosi-
lane (Si6Me11H) in almost quantitative yield [4]. This
compound can be converted into the corresponding
chloride or bromide by treatment with carbon tetra-
chloride or bromoform, avoiding the inconvenient use
of gaseous hydrogen halides. In addition, Si6Me11H
also provides access to the bis(cyclohexasilanyl)mercury
derivative, a versatile starting material for the forma-
* Corresponding author. Tel.: +43-316-873-8201; fax: +43-316-
873-8701.
E-mail address: marschner@anorg.tu-graz.ac.at (C. Marschner)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00702-0

U. Englich et al. / Journal of Organometallic Chemistry 598 (2000) 202–210
203
tion of the base-free undecamethylcyclohexasilanyl
potassium salt (Scheme 1).
At this point it was planned to utilize the remaining
phenyl groups of 3a and 3b in order to introduce addi-
tional functionality by replacing the phenyl substituents
with trifluoromethanesulfonyl groups. However, treat-
ment of both the methyl phenyl-substituted 3a and the
diphenyl derivative 3b with triflic acid did not result in a
reaction even when excess triflic acid or heating was ap-
plied. An alternative route utilizing HCl–AlCl3 instead
of triflic acid was also not successful. It is assumed that
the steric shielding of the central silicon atom prevents a
reaction.
As an alternative route we decided to substitute the
phenyl with triflate groups before reacting the unde-
camethylcyclohexasilanylsilane compound with a second
equivalent of the potassium salt. This can easily be ac-
complished by treatment of compound 1a with two
equivalents of triflic acid (4a, Scheme 3). Reaction of
With this convenient route to undecamethylcyclohexa-
silanyl potassium at hand, we decided to revisit the
chemistry of the bis(undecamethylcyclohexasilanyl)silyl
compounds. Analogously to the synthesis of bis(unde-
camethylcyclohexasilanyl)dimethylsilane, we employed
a salt elimination strategy involving substituted mono-
silyl electrophiles and the undecamethylcyclohexa-
silanyl potassium derivative.
Treatment of undecamethylcyclohexasilanyl potas-
sium with phenylated chlorosilanes yielding the cyclohex-
asilanylsilanes (1) was followed by a protodesilylation
reaction with triflic acid [5], which proceeded smoothly as
described recently [6]. Subsequent conversion with a
second equivalent of undecamethylcyclohexasilanyl
potassium resulted in the formation of the desired bis(un-
decamethylcyclohexasilanyl)silanes 3 (Scheme 2).
Scheme 1. A general entry into the chemistry of monofunctionalized undecamethylcyclohexasilanes.
Scheme 2. Synthesis of phenylated bis(cyclohexasilanyl)silanes.

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U. Englich et al. / Journal of Organometallic Chemistry 598 (2000) 202–210
Scheme 3. Synthesis of functional bis(cyclohexasilanyl)silanes.
In order to obtain the corresponding monofluoride
5d, we reacted bromide 5b with zinc fluoride in ether.
The reaction proceeded as hoped, but required 30 days
in refluxing diethyl ether to proceed to completion. An
improvement of this time-consuming route is the use of
tetrabutylammonium triphenyldifluorostannate [7] as
the fluorinating agent, resulting in the complete conver-
sion of the bromide precursor after 2 days at room
temperature (Scheme 3).
Reaction of the monohalides 5b and 5c with lithium
aluminum hydride gave the expected hydrosilane 6 in
an almost quantitative reaction. Chlorination of hy-
drosilane 6 was attempted to obtain additional infor-
mation with respect to the steric accessibility of the
bis(undecamethylcyclohexasilanyl)silyl fragment. The
chlorination of the secondary hydrosilane, a usually
quite feasible reaction, required several days in reflux-
ing CCl4 (Scheme 4) and was accompanied by the
formation of undecamethylcyclohexasilanyl chloride
and (undecamethylcyclohexasilanyl)methylsilyl dichlo-
ride, indicating SiꢀSi bond cleavage.
Since we were unable to attach a third undecamethyl-
cyclohexasilanyl unit to the central silicon atom, we
decided to attempt a Wurtz-type coupling reaction of
bromide 5b to see whether we could obtain a disilane
with four undecamethylcyclohexasilanyl substituents.
However, treatment of 5b with sodium in refluxing
toluene did not yield the expected disilane, but a mix-
ture of two products in an approximate ratio of 1:1.
One of the compounds was the already mentioned
hydrosilane 6, the other being the benzyl-substituted
derivative 7 (Scheme 5).
the ditriflate derivative with one equivalent of unde-
camethylcyclohexasilanyl potassium yielded the methyl-
bis(undecamethylcyclohexasilanyl)silyl
triflate
5a
(Scheme 3). The addition of a third equivalent of the
potassium salt to form the tris(undecamethylcyclohex-
asilanyl)silyl compound mainly results in the formation
of bis(undecamethylcyclohexasilanyl), possibly caused
by transmetallation with an undecamethylcyclohexasi-
lanyl triflate intermediate accepting another equivalent
of undecamethylcyclohexasilanyl potassium.
The formation of methylbis(undecamethylcyclohexa-
1
silanyl)silyl triflate 5a was confirmed by 29Si- and H-
NMR spectroscopy, although we were unable to isolate
a clean compound or to purify the crude mixture by
crystallization. Accordingly, we decided to investigate
the use of halide instead of triflate derivatives. Both the
(cyclohexasilanyl)methylsilyldibromide 4b and the cor-
responding dichloride 4c are easily accessible by reac-
tion of ditriflate 4a with the respective lithium halide in
diethyl ether. Alternatively, the dibromide 4b can be
obtained in a very clean reaction by treatment of the
diphenyl compound 1a with neat liquid hydrogen bro-
mide at −78°C (Scheme 3).
Reaction of the dihalides 4b,c with one equivalent of
undecamethylcyclohexasilanyl potassium resulted in
substitution and formation of the respective mono-
halides, which were purified by crystallization from
pentane (Scheme 3). Again, attempts to treat the mono-
halides 5b,c with another equivalent of undecamethyl-
cyclohexasilanyl potassium led mainly to the formation
of bis(undecamethylcyclohexasilanyl).

U. Englich et al. / Journal of Organometallic Chemistry 598 (2000) 202–210
205
Scheme 4. Hydrogenation and halogenation of the bis(undecamethylcyclohexasilanyl) fragment.
Scheme 5. Attempted Wurtz-type coupling of bromosilane 5b.
but as an electrophile. In the first step we reacted
undecamethylcyclohexasilanyl bromide with tris(tri-
methylsilyl)silyl potassium. The reaction proceeded
cleanly yielding tris(trimethylsilyl)(undecamethylcyclo-
hexasilanyl)silane 8, which was transformed by treat-
ment with one equivalent of potassium tert-butoxide
into bis(trimethylsilyl)(undecamethylcyclohexasilanyl)-
silyl potassium 9. Reaction with a second equivalent of
undecamethylcyclohexasilanyl bromide resulted into the
formation of bis(trimethylsilyl)bis(undecamethylcyclo-
hexasilanyl)silane 10 (Scheme 6).
We assume that this reaction involves the formation
of the expected silyl sodium species in a first step.
However, the bulky silyl sodium derivative does not
react with the sterically hindered silyl bromide 5b at all,
but rather effects the deprotonation of toluene, result-
ing in the formation of hydrosilane 6 and benzyl
sodium. The latter, being sterically less encumbered
than the silyl sodium compound, reacts with 5b to form
benzylsilane 7.
Compound 6 was investigated by single-crystal X-ray
analysis (Fig. 1). Comparison with bis(undecamethylcy-
clohexasilanyl)dimethylsilane [1b] showed the structures
to be quite similar (Table 1). As expected, the dihedral
angle between the bridgehead and the central silicon
atom is slightly larger for the case of the hydrosilane
(6). (116 vs. 113°). All other dihedral angles around the
central silicon atom indicate an almost perfect tetrahe-
dral environment.
An alternative attempt to the bis(undecamethylcyclo-
hexasilanyl)silyl moiety involved some other recently
developed silyl potassium chemistry from our laborato-
ries [8]. In this case we decided to use the unde-
camethylcyclohexasilanyl moiety not as a nucleophile
Fig. 1. Crystal structure of methylbis(undecamethylcyclohexasi-
lanyl)silane (6).

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U. Englich et al. / Journal of Organometallic Chemistry 598 (2000) 202–210
Table 1
Schlenk techniques. All solvents were dried over a
sodium–potassium alloy under nitrogen and distilled
prior to use. Undecamethylcyclohexasilanyl potassium
[3], undecamethylcyclohexasilanyl-dimethylsilylbromide
[6] and tris(trimethylsilyl)silyl potassium [8] were
prepared according to published procedures. All
NMR spectra were recorded on a Bruker MSL 300
spectrometer (1H, 300.13 MHz; 13C, 75.47 MHz; 29Si,
59.627 MHz, 19F, 282.23 MHz). Samples were dissolved
in CDCl3, C6D6, or toluene using a capillary filled
with D2O as external standard. Shifts are reported in
ppm downfield from TMS (tetramethylsilane). GC
analyses were carried out on an HP 5890 series
II (capillary column DB-1HT; 15 m×0.251 mm, 0.1
mm; flame ionization detector). Mass spectra were ob-
tained either with a HP 5971 or a Kratos profile
spectrometer.
Selected bond lengths (pm) and bond angles (°) of methylbis(un-
decamethylcyclohexasilanyl)silane (6) and dimethylbis(undecamethyl-
cyclohexasilanyl)silane [1b]
(Si6Me11)2Si(H)Me
(6)
(Si6Me11)2SiMe2
Bond lengths
Si(1)ꢀSi(2), Si(1)ꢀSi(8)
235.4(2), 234.9(2)
236.8, 235.6
Bond angles
Si(1)ꢀC(1), Si(1)ꢀC(1%)
Si(2)ꢀSi(1)ꢀSi(8)
Si(2)ꢀSi(1)ꢀC(1)
Si(8)ꢀSi(1)ꢀC(1)
Si(2)ꢀSi(1)ꢀC(1%)
Si(8)ꢀSi(1)ꢀC(1%)
186.3(7)
116.08(9)
112.4(2)
111.2(2)
190.3, 189.7
112.89
110.22
107.55
109.23
111.17
3. Conclusions
4.2. Synthesis of undecamethylcyclohexasilane
The substitution chemistry of the bis(undecamethyl-
cyclohexasilanyl)silyl fragment was only partially suc-
cessful. Neither was protodesilylation of the phenylated
compounds possible nor was the nucleophilic substitu-
tion of the corresponding halides a facile process. We
believe that steric arguments are mainly responsible for
this, since small nucleophiles such as the benzyl anion or
reagents such as lithium aluminum hydride undergo the
desired reaction, while the sterically demanding unde-
camethylcyclohexasilanyl potassium fails. Another hint
leading to this conclusion was the ease of the metal–
halogen exchange reaction.
Currently we are studying the chemistry of the
(trimethylsilyl)bis(undecamethylcyclohexasilanyl)silyl
potassium, which may be a useful precursor for the
introduction of a variety of other substituents into the
bis(undecamethylcyclohexasilanyl)silyl system.
A solution of undecamethylcyclohexasilanyl potas-
sium (22.9 mmol) in dimethoxyethane (DME) was
added dropwise to a diethyl ether–aqueous H2SO4
mixture. After complete addition the aqueous layer was
saturated with sodium chloride and extracted twice with
ether. The combined etheral solutions were dried over
sodium sulfate and the solvent was removed in vacuo.
The remaining residue (7.13 g, 21.3 mmol, 93%) was
found to be undecamethylcyclohexasilane contaminated
with approximately 4% nonamethylcyclopentasilane as
1
judged by GC and H-NMR.
4.3. Synthesis of bromoundecamethylcyclohexasilane
Undecamethylcyclohexasilane (2.0 g, 5.97 mmol) was
dissolved in bromoform (15 ml) and stirred for 4
days at room temperature (r.t.) After complete conver-
sion the solvent was removed in vacuo and the remain-
ing orange residue was dissolved in pentane and
crystallized at −78°C. Colourless crystals (2.21 g,
5.34 mmol, 89%) were obtained. Spectral properties of
the compound were in agreement with literature data
[1].
4. Experimental
4.1. General data
All manipulations involving air-sensitive materials
were performed under nitrogen or argon using standard
Scheme 6. The ‘inverse’ approach to the bis(undecamethylcyclohexasilanyl)silyl fragment.

U. Englich et al. / Journal of Organometallic Chemistry 598 (2000) 202–210
207
4.4. Synthesis of methyldiphenyl(undecamethylcyclo-
hexasilanyl)silane (1a)
acid (1 M, 200 ml). The aqueous layer was washed with
three portions of toluene and the combined toluene
solutions were evaporated to dryness. The brown oily
residue was recrystallized twice from isopropanol to
give fine colourless crystals (5.9 g, 7.5 mmol, 27.8%).
Undecamethylcyclohexasilanyl
potassium
(54.4
mmol) dissolved in DME (200 ml) was added dropwise
to a stirred solution of chloromethyldiphenylsilane
(12.7 g, 54.4 mmol) in toluene (120 ml) at 0°C. After
stirring the mixture for an additional hour, the solution
was poured onto ice-cooled hydrochloric acid (1 M, 200
ml). The aqueous layer was extracted with toluene and
the combined organic layers were dried over Na2SO4.
After evaporation of the solvents a brownish residue
was obtained, which was recrystallized from isopro-
panol yielding colourless crystals (15.3 g, 28.8 mmol,
1
M.p.: 122°C. H-NMR (TMS): l 7.26 (m, 5H), 0.69 to
−0.11 (m, 69H). 13C-NMR (TMS): l 134.97, 127.96,
−3.16 to −7.89 (several signals) 29Si-NMR (TMS): l
−29.23, −36.47/−36.56, −40.41/−40.45, −42.93,
−74.73. MS (70 eV): m/z (%): 786 (M+, 26%), 728,
13%), 453 (17%), 318 ( 100%). Anal. Found: C, 44.20;
H, 9.46. Calc.: C, 44.35; H, 9.49%.
4.8. Synthesis of diphenylbis(undecamethylcyclo-
hexasilanyl)silane (3b)
1
53%) of 1b. M.p.: 187–190°C. H-NMR (TMS): l 7.58
(5H), 7.37 (5H), 0.33 (s, 3H) 0.19–0.00 (m, 33H).
13C-NMR (TMS): l 138.81, 135.09, 128.61, 127.96,
−1.53, −3.14, −4.70, −5.16, −6.55, −9.53. 29Si-
NMR (TMS): l −15.41, −38.12, −40.44, −42.40,
−81.35. MS (70 eV): m/z (%): 530 [M+, 25%], 333
(Si6Me11, 2%), 318 (Si6Me10, 23%), 73 (SiMe3, 100%).
Anal. Found: C, 54.26; H, 8.73. Calc.: C, 54.44; H,
8.82%.
The synthesis of 3b was accomplished by dissolving
2b (21.6 mmol) in toluene (150 ml) and adding un-
decamethylcyclohexasilanyl potassium (26.9 mmol)
in DME as described for 3a. After recrystallization
from isopropanol, the product was obtained as colour-
less crystals (6.9 g, 8.1 mmol, 37.6%). M.p.: 110°C.
1H-NMR (TMS): l 7.31 (m, 10H), 0.45 to −0.12
(m, 66H). 13C-NMR (TMS):
128.53, 127.76, −3.00, −3.99, −4.73, −5.39, −6.14,
−6.37. 29Si-NMR (TMS):
−23.99, −36.27,
l
137.70, 136.91,
4.5. Synthesis of methylphenyl(trifluoromethane-
sulfonyloxy)(undecamethylcyclohexasilanyl)silane (2a)
l
−40.65, −43.72, −73.22. MS (70 eV): m/z (%):
849 [M+, 14%], 819, 3%), 790 (8%), 761 (4%), 73
(100%). Anal. Found: C, 48.04; H, 9.01. Calc.: C,
48.28; H, 9.08%.
Methyldiphenyl(undecamethylcyclohexasilanyl)silane
(1a) (14.3 g, 26.9 mmol) was dissolved in toluene (150
ml) and cooled to −20°C. After the dropwise addition
of triflic acid (2.36 ml, 26.9 mmol) the mixture was
allowed to warm up and stirred for an additional 2 h at
r.t. Complete conversion was detected both by GC–MS
of a derivatized sample (LiAlH4 quench) and by 29Si-
NMR. The obtained solution was used without further
purification. 29Si-NMR (TMS): l 37.61, −38.87/
−39.11, −40.18, −42.14, −79.63.
4.9. Synthesis of methylbis(trifluoromethane-
sulfonyloxy)(undecamethylcyclohexasilanyl)silane (4a)
Si6Me11SiMePh2 (1b) (15.3 g, 28.8 mmol) was dis-
solved in toluene (150 ml) and cooled to −20°C.
Within 30 min neat triflic acid (5.06 ml, 57.6 mmol) was
added dropwise. Subsequently, the cooling bath was
removed and the reaction mixture was stirred overnight
at r.t. The resulting solution was used without further
purification for the synthesis of 4b. 29Si-NMR (TMS): l
33.72, −39.86, −40.41, −42.21, −77.66.
4.6. Synthesis of diphenyl(trifluoromethane-
sulfonyloxy)(undecamethylcyclohexasilanyl)silane (2b)
The synthesis of 2b was accomplished by the reaction
of triphenyl(undecamethylcyclohexasilanyl)silane (12.8
g, 21.6 mmol) with triflic acid (1.89 ml, 21.6 mmol),
analogous to 2a. The toluene solution was used without
4.10. Syntheses of dibromomethyl(undecamethylcyclo-
hexasilanyl)silane (4b)
further purification. 29Si-NMR (TMS):
l
25.16,
(a) After adding diethyl ether (100 ml) to the solution
of silyl triflate 4a in toluene, lithium bromide (5.0 g,
57.6 mmol) was added at 0°C. The reaction mixture
was stirred overnight. Subsequently, the solvents were
removed under reduced pressure and the resulting solid
residue was dispersed in pentane. Filtration and evapo-
ration of the filtrate resulted in a colourless solid
residue of 4b. Yield: 15.2 g (28.3 mmol, 98.3%).
−38.30, −40.16, −42.49, −79.77.
4.7. Synthesis of methylphenylbis(undecamethylcyclo-
hexasilanyl)silane (3a)
A solution of 2a (26.9 mmol) in toluene (150 ml) was
cooled to 0°C and undecamethylcyclohexasilanyl potas-
sium (26.9 mmol) in DME was added dropwise. After
complete conversion, as monitored by GC, the reaction
mixture was added to ice-cooled aqueous hydrochloric
(b) A flask equipped with a reflux condenser cooled
to −80°C and charged with methyldiphenyl(unde-
camethylcyclohexasilanyl)silane (1a) (2.70 g, 5.08

208
U. Englich et al. / Journal of Organometallic Chemistry 598 (2000) 202–210
mmol) was cooled to −80°C and approximately 15 ml
of hydrogen bromide was condensed into the reaction
vessel. After 1 h the cooling bath was removed and the
solution was refluxed for 2 h, followed by evaporation
of excess hydrogen bromide and benzene. GC analysis
of the remaining colourless solid showed pure 4b (2.73
g, 100%). M.p.: 161–163°C. 1H-NMR (TMS): l 1.12 (s,
3H), 0.36–0.14 (m, 33H). 13C-NMR (TMS): l 12.64,
−3.13, −4.58, −4.85, −6.27, −9.52. 29Si-NMR
(TMS): l 25.63, −38.18, −39.84, −41.74, −67.61.
MS (70 eV): m/z (%): 536 [M+, 2%], 463 (Si6Me9Br2,
3%), 399 (Si6Me10Br, 23%), 333 (Si6Me11, 4%), 259
(Si6Me6, 18%), 73 (SiMe3, 100%). Anal. Found: C,
26.85; H, 6.76. Calc.: C, 27.13; H, 6.67%.
29Si-NMR (TMS): l 33.02, −35.72/−37.42, −40.43/
−40.52, −42.75, −69.11. MS (70 eV): m/z (%): 746
[M+, 24%], 411 (Si7Me12Cl, 9%), 376 (Si7Me12, 46%),
73 (SiMe3, 100%). Anal. Found: C, 37.27; H, 9.44.
Calc.: C, 37.01; H, 9.32%.
4.13. Syntheses of bis(undecamethylcyclohexasilanyl)-
fluoromethylsilane (5d)
(a) (Si6Me11)2SiMeBr (5b) (0.60 g, 0.76 mmol) was
dissolved in diethyl ether (20 ml) and ZnF2 (0.80 g, 7.7
mmol) was added. The mixture was heated to reflux for
30 days after which GC analysis indicated quantitative
conversion. Filtration, evaporation of the solvent, and
recrystallization of the residue from n-pentane yielded
0.26 g (0.36 mmol, 47%) of colourless (Si6Me11)2SiMeF
(5d).
4.11. Synthesis of dichloromethyl(undecamethylcyclo-
hexasilanyl)silane (4c)
(b) (Si6Me11)2SiMeBr (5b) (0.60 g, 0.76 mmol) was
dissolved in diethyl ether (20 ml), tetrabutylammonium
difluorotriphenylstannate (0.23 g, 0.36 mmol) was
added and the reaction mixture was stirred for 2 days at
r.t., followed by the removal of the solvent under
reduced pressure and addition of n-pentane. The result-
ing suspension was filtered and the volatiles evaporated.
The colourless residue was recrystallized from n-pen-
tane yielding 0.38 g (0.52 mmol, 69%) of 5d. 29Si-NMR
Diethyl ether (100 ml) and lithium chloride (1.43 g,
33.7 mmol) were added to a solution of silyl triflate 4b
(16.8 mmol) and the reaction mixture was stirred for 10
h. After a work-up similar to the synthesis of the
bromo derivative (4b), 4c (7.10 g, 15.6 mmol, 94.4%)
was obtained as a colourless solid. M.p.: 155–157°C.
1H-NMR (TMS): l 0.77 (s, 3H), 0.33–0.14 (m, 33H).
29Si-NMR (TMS): l 40.96, −39.34, −40.40, −42.10,
−71.13. MS (70 eV): m/z (%): 446 [M+, 7%], 431
(Si7Me11Cl2, 1%), 353 (Si6Me10Cl, 11%), 73 (SiMe3,
100%). Anal. Found: C, 32.27; H, 8.14. Calc.: C, 32.18;
H, 8.10%.
1
(TMS): l 58.21 (d, JSiꢀF 335.6 Hz), −35.88/−37.57
3
2
(d, JSiꢀF 5.1 Hz), −39.67/−39.90, −73.85 (d, JSiꢀF
19.1 Hz). 19F-NMR: l −178.03 (q, JFꢀH 7.9 Hz).
3
4.14. Synthesis of bis(undecamethylcyclohexasilanyl)-
methylsilane (6)
4.12. Syntheses of the monohalogenated
bis(undecamethylcyclohexasilanyl)methylsilyl compounds
5b and 5c
A solution of 5b (2.51 g, 3.17 mmol) in diethyl ether
(30 ml) was cooled to 0°C and an etheral solution of
LiAlH4 (1.0 ml, 2.4 M, 2.4 mmol) was added dropwise.
The reaction mixture was allowed to warm to r.t. and
stirred for another 10 min. The solution was poured
into ice-cooled hydrochloric acid (1 M, 40 ml) and the
aqueous layer was extracted with three portions of
petroleum ether (30 ml each). The combined organic
layers were dried over Na2SO4 and the solvents evapo-
rated. Yield: 2.20 g (3.09 mmol, 97%) of 6. M.p.:
(Si6Me11)SiMeBr2 (4b) (12.7 g, 23.7 mmol) or
(Si6Me11)SiMeCl2 (4c) (7.45 g, 16.6 mmol), respectively,
were dissolved in n-pentane (120 ml) and cooled to 0°C.
An equimolar amount of a solution of undecamethylcy-
clohexasilanyl potassium in DME was slowly added
and the resulting mixture was stirred for 2 h at r.t. The
solvents were removed under reduced pressure and the
residue was dispersed in n-pentane. After filtration and
evaporation compounds 5b or 5c, respectively, were
crystallized from n-pentane yielding colourless solids.
5b: Yield 5.4 g (6.8 mmol, 28.9%), m.p.: 152–155°C.
1H-NMR (TMS): l 1.12 (s, 3H), 0.55 (s, 6H), 0.53 (s,
6H), 0.45 (s, 6H), 0.42 (s, 6H), 0.39 (s, 6H), 0.23 (m,
36H). 29Si-NMR (TMS): l 22.92, −34.97/−36.76,
−40.68/−40.75, −42.74, −68.83. MS (70 eV): m/z
(%): 788 [M+, 5%], 709 (Si13Me23, 25%), 376 (Si7Me12,
70%), 361 (Si7Me11, 10%), 333 (Si6Me11, 100%), 73
(SiMe3, 100%). Anal. Found: C, 35.69; H, 8.87. Calc.:
C, 34.93; H, 8.79%.
1
140°C. H-NMR (TMS): l 4.20 (q, 1H, J=5.3 Hz),
0.49 (d, 3H, J=5.3 Hz), 0.51–0.24 (m, 66H). 29Si-
NMR (TMS): l −36.88/−37.83, −40.25/−40.57,
−42.08, −65.65 (1JSiꢀH 160.4 Hz), −75.83. IR: 2073
(wSiꢀH) cm−1. MS (70 eV): m/z (%): 710 [M+, 43%], 505
(Si10Me15, 9%), 333 (Si6Me11, 15%), 303 (Si6Me9, 41), 73
(SiMe3, 100%). Anal. Found: C, 38.91; H, 9.99. Calc.:
C, 38.80; H, 9.91%.
Crystal data for 6: C23H70Si13, M=711.96, mono-
clinic, space group P21/c, a=9.8621(1), b=13.7906(1),
3
,
,
c=34.9563(3) A, i=96.500(1)°, V=4723.65(7) A , T
(K)=150, Z=4, v=0.367 mm−1 (Mo–Ka). Colour-
less plates of dimensions 0.22×0.08×0.05 mm3. 8144
5c: Yield 5.3 g (7.1 mmol, 42.7%), m.p.: 150°C.
1H-NMR (TMS): l 0.82 (s, 3H), 0.34–0.16 (m, 66H).

U. Englich et al. / Journal of Organometallic Chemistry 598 (2000) 202–210
209
independent reflections (2.452q550.00°). R1=0.0851
for 5049 data (I\2|(I) and wR2=0.1445 for all data.
The crystals were removed from the Schlenk flask un-
der a stream of N2 and immediately covered with a
layer of viscous hydrocarbon oil (Paratone N, Exxon).
A suitable crystal was selected under the microscope,
attached to a glass fibre, and immediately placed in the
low-temperature nitrogen stream of the diffractometer
[9]. The data set was collected using a Siemens SMART
system at −123°C (Oxford Instruments Cryojet low-
temperature device), complete with three-circle
goniometer and CCD detector operating at −54°C,
employing monochromated Mo–Ka radiation (u=
(Si6Me10, 44%), 73 (SiMe3, 100%). Anal. Found: C,
45.14; H, 9.60. Calc.: C, 44.93; H, 9.55%.
4.16. Synthesis of tris(trimethylsilyl)(undecamethyl-
cyclohexasilanyl)silane (8)
Tris(trimethylsilyl)silyl potassium (0.485 g, 1.69
mmol) in toluene (2 ml) was added dropwise to an
ice-cooled solution of bromoundecamethylcyclohexasi-
lane (0.934 g, 1.69 mmol) in toluene (10 ml) within 30
min. After stirring for further 2 h GC–MS analysis
showed complete conversion, hence, the suspension was
poured into 2 M aqueous H2SO4. The aqueous layer
was extracted with toluene, the combined organic layers
were dried with Na2SO4, followed by evaporation of
the solvents. Subsequent recrystallization of the colour-
less residue from n-pentane yielded 0.952 g (1.63 mmol,
,
0.71073 A). The data collections nominally covered a
hemisphere of reciprocal space utilizing a combination
of three sets of exposures, each with a different ƒ angle,
and each exposure covering 0.3° in ꢀ. Crystal decay
was monitored by repeating the initial frames at the end
of the data collection and analysing the duplicate reflec-
tions. In all cases, no decay was observed. An absorp-
tion correction was applied utilizing the program
SADABS [10]. The crystal structure was solved by direct
methods, as included in the SHELX program package
[11]. Missing atoms were located in subsequent differ-
ence Fourier maps and included in the refinement. The
structures of all compounds were refined by full-matrix
1
97%) of 8. M.p.: 117–121°C. H-NMR (TMS): l 2.18
(s, 3H), 0.31–0.16 (m, 57H). 13C-NMR (TMS): l 3.96,
−2.10 to −6.23 (several signals). 29Si-NMR (TMS): l
−9.61, −35.87, −39.22, −43.29, −70.20, −126.47.
MS (70 eV): m/z (%): 580 [M+, 0.3%], 333 (Si6Me11,
15%), 232 (Si4Me8, 51%) 73 (SiMe3, 100%).
4.17. Synthesis of bis(trimethylsilyl)(undecamethylcyclo-
hexasilanyl)silyl potassium (9)
least-squares refinement on F2
(SHELX-93) [12]. The
hydrogen at Si-1 was located in a difference Fourier
map and included in the refinement by using distance
restraints and Ueq of 1.2 of the carrier Si atom. All
other hydrogen atoms were placed geometrically and
refined using a riding model, including free rotation
about CꢀC bonds for methyl groups with Uiso con-
strained at 1.2 for non-methyl groups, and 1.5 for
methyl groups times Ueq of the carrier C atom. Scatter-
ing factors were those provided with the SHELX pro-
gram system.
Compound 8 (0.82 g, 1.41 mmol) and potassium
tert-butoxide (0.16 g, 1.41 mmol) were dissolved in 10
ml THF. The reaction mixture was stirred at r.t. and
after 4 h GC–MS analysis showed complete conver-
sion. The solvent was removed under reduced pressure
and 2 ml of toluene were condensed onto the residue.
The solution was used for the synthesis of 10 without
further purification. 29Si-NMR (TMS): l −5.39, −
38.37, −40.37, −42.21, −64.84, −184.54. MS (70
eV) (ethyl bromide quench): m/z (%): 536 [M+, 6%],
333 (Si6Me11, 30%), 73 (SiMe3, 100%).
4.15. Syntheses of bis(undecamethylcyclohexasilanyl)-
methylsilane (6) and benzylbis-(undecamethylcyclohexa-
silanyl)methylsilane (7)
4.18. Synthesis of bis(trimethylsilyl)bis(undecamethyl-
cyclohexasilanyl)silan (10)
Sodium (0.20 g, 8.7 mmol) was added to a solution of
(Si6Me11)2SiMeBr (5b) (2.00 g, 2.53 mmol) in toluene
(20 ml). The stirred mixture was refluxed for 48 h and
subsequently filtered. The volatiles were evaporated, the
residue purified chromatographically using silica gel 60
and n-heptane, resulting in 0.53 g (0.74 mmol, 58%) of
6 and 0.51 g (0.63 mmol, 50%) of 7.
Compound 9 (1.41 mmol) in toluene was added
dropwise to an ice-cooled solution of bromounde-
camethylcyclohexasilane (0.587 g, 1.41 mmol) in 5 ml of
toluene. The mixture was allowed to warm to r.t. and
stirred for 1 h. Work-up proceeded with pouring the
reaction mixture into 2 M H2SO4, followed by extrac-
tion with toluene, drying, and evaporation. The remain-
ing residue was sublimated (0.1 mbar, 125°C) yielding
0.81 g (0.96 mmol, 68%) of pure crystalline 10. 29Si-
NMR (TMS): l −9.39, −32.74, −37.45, −41.59,
−67.09, −109.74. MS (70 eV): m/z (%): 842 [M+,
1
7: H-NMR (TMS): l 7.18 (m, 5H), 2.73 (s, 2H),
0.54–0.19 (m, 69H). 13C-NMR (TMS): l 141.43,
129.77, 129.15, 125.41, 26.80, 0.61, −1.67 to −6.68
(several signals). 29Si-NMR (TMS): l −18.82, −35.73/
−36.75, −40.17/−40.28, −42.86, −73.05. MS (70
eV): m/z (%): 800 [M+, 15%], 467 (Si7Me12Bn, 9%), 319

210
U. Englich et al. / Journal of Organometallic Chemistry 598 (2000) 202–210
[2] F.K. Mitter, E. Hengge, J. Organomet. Chem. 332 (1987) 47.
[3] F. Uhlig, P. Gspaltl, M. Trabi, E. Hengge, J. Organomet. Chem.
493 (1995) 33.
1%], 492 (Si9Me16, 17%), 333 (Si6Me11, 14%), 131
(Si2Me5, 11%) 73 (SiMe3, 100%).
[4] E. Hengge, M. Eibl, F. Schrank, Spectrochim. Acta A 47 (1991)
721.
[5] W. Uhlig, Chem. Ber. 125 (1992) 47.
[6] E. Hengge, P. Gspaltl, E. Pinter, J. Organomet. Chem. 521
(1996) 145.
[7] R. Hummeltenberg, K. Jurkschat, F. Uhlig, Phosphorus Sulfur
Silicon 123 (1997) 255.
[8] Ch. Marschner, Eur. J. Inorg. Chem. (1998) 221.
[9] H. Hope, Progr. Inorg. Chem. 41 (1994) 1.
[10] G.M. Sheldrick, SADABS, Program for Absorption Correction
Using Area Detector Data, University of Go¨ttingen, Germany,
1996.
5. Supplementary material
Full details have been deposited with the Cambridge
Cystallographic Data Centre (CCDC 101461) and are
also available in CIF format from the authors.
References
[11] SHELXTL-Plus, Program Package for Structure Solution and
Refinement, Siemens, Madison, WI, 1996.
[12] G.M. Sheldrick, SHELXL-93, Program for Crystal Structure
Refinement, University of Go¨ttingen, Germany 1993.
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