The reactions of dialkyl and diarylethoxysilanes with T6 silsesquioxane cages. X-ray crystallographic studies of the mono-T6D1 and bis-T6D2 insertion ring expansion products

Article abstract of DOI:10.1016/S0022-328X(03)00622-3

Successful ring-expanding insertion reactions of T₆ silsesquioxane cages using dialkyl and diarylethoxysilanes have been performed to give the first reported mixed T₆D₁ and T₆D₂ silsesquioxane cages.

Full text of DOI:10.1016/S0022-328X(03)00622-3

Journal of Organometallic Chemistry 687 (2003) 1ꢀ11
/
www.elsevier.com/locate/jorganchem
The reactions of dialkyl and diarylethoxysilanes with T6
silsesquioxane cages
X-ray crystallographic studies of the mono-T6D1 and bis-T6D2
insertion ring expansion products
Alan R. Bassindale a,*, Zhihua Liu a, David J. Parker a, Peter G. Taylor a,*,
Peter N. Horton b, Michael B. Hursthouse b, Mark E. Light b
a Department of Chemistry, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
b Department of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
Received 1 May 2003; accepted 17 June 2003
Abstract
Successful ring-expanding insertion reactions of T6 silsesquioxane cages using dialkyl and diarylethoxysilanes have been
performed to give the first reported mixed T6D1 and T6D2 silsesquioxane cages. The reactions of hexacyclohexylsilsesquioxane (T6)
with dialkyl and diaryldiethoxysilanes give predominantly T6D2 bis-insertion compounds while the reaction of T6 with
dimethylethoxysilane gives one T6D1 mono-insertion product and various T6D2 bis-insertion products as isolable components.
Three of the ring-expanded products are chiral and it has been shown from their X-ray crystal structures that the pairs of
enantiomers, formed as racemic mixtures, co-crystallise together. As well as comparing these structures with related ones in the
literature, the possible mechanism of their formation is discussed.
# 2003 Elsevier B.V. All rights reserved.
Keywords: T6 silsesquioxane cage; Alkoxysilane; Insertion reaction; Ring opening; Cage expansion; X-ray study
1. Introduction
hexasilsesquioxanes 4 (known as T6’s) that has under-
gone a ring expansion to date is 5, which was formed as
a by-product in Feher’s synthesis of 1. Its structure was
confirmed from the X-ray crystal structure of its bis-
triphenyltin analogue 6 [6]. Compound 5 itself has been
found to be a useful reagent for complexing with
aluminium or titanium to give heterogeneous catalysts
and for reacting with siloxanes to form novel
Silsesquioxanes have long been of importance to those
interested in modelling the chemical environment of
silica surfaces on a molecular level leading to applica-
tions in catalysis, materials and surface chemistry. The
challenge of developing synthetic routes to complex
cages from simpler, more easily prepared ones is to
develop methods of adding individual siloxane units to
cages in a controlled fashion.
silsesquioxaneꢀ
/
siloxane co-polymers [7ꢀ10].
/
While centrosymmetric T8’s 2 (where Rꢁ
/
R?) [11ꢀ16]
/
For example, various groups have taken trisilanol 1
(Scheme 1) and reacted it with trichlorosilanes or
functionalised metal complexes to form octasilsesquiox-
and to a lesser extent T6’s 4 [12,17] are well-established
structural types in the literature, ring expansion reac-
tions that allow them to be used directly as precursors to
larger, more complex silsesquioxanes such as 5 have
remained unreported until now. In this paper, we report
the aqueous tetrabutylammonium fluoride (TBAF)-
catalysed insertion reactions of dimethylethoxysilane
or dialkyl and diaryldiethoxysilanes with hexacyclohex-
ylsilsesquioxane (CyT6) 7. We have also examined the
anes (known as T8’s) 2 [1ꢀ/3] and metallasilsesquioxanes
3 [4,5], respectively. The only structural analogue of
* Corresponding author. Tel.: ꢂ
858327.
E-mail address: p.g.taylor@open.ac.uk (P.G. Taylor).
/
44-1908-652512; fax: ꢂ44-1908-
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00622-3

2
A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ
/
11
Scheme 1.
crystal structures of the compounds isolated and sug-
gested the mechanism of their formation.
The formation of 11 is thought to be due to TBAF-
initiated rearrangement of 7 which will be discussed in a
future paper [18]. Whilst the isolated yields of major
products 8, 9 and 10 are relatively low in a purely
preparative sense, they are very acceptable in compar-
ison with the typical yields reported for other silses-
quioxane compounds prepared by similarly non-
regioselective routes. The appearance of one D-silicon
and three T-silicon peaks in the 29Si-NMR spectra with
an intensity ratio 1:1:1:1 provided characteristic evi-
dence that the bis-insertion product had been formed in
each reaction. This was confirmed by obtaining single
crystal X-ray structures as shown in Figs. 1 and 2
2. Results and discussion
The reaction of 7 with dialkyl or diaryldiethoxysilanes
is described in Scheme 2. In each case, a 4:2:1 ratio of
dialkoxysilane, 7 and TBAF was used, and the major
products were the corresponding bis-insertion, ring-
expanded T6D2 cages 8, 9 or 10 along with a small
quantity of octacyclohexylsilsesquioxane (CyT8) (B
/1%)
11 in each case.
Scheme 2.

A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ
/
11
3
˚
Fig. 1. ORTEP representation (left) of 8 with envelopes drawn at the 50% probability level. Selected bonding distances (A) and bond angles (8) are
given in Table 1. The simplified schematic structure (right) represents with dashed lines the edges of the former T6 cage that the dimethylsiloxy groups
have added across. The bridging siloxane O atoms are omitted for clarity with ‘‘SiÃ
/
Si’’ representing the SiÃ
/
OÃSi moiety.
/
(Tables 1 and 2). Whilst the structural connectivity of 9
was confirmed by X-ray crystallography, it was not
possible to obtain data of a sufficient quality for a full
structural refinement of this compound.
control both enantiomers 12 and 13 will be formed as a
racemic mixture. For example, the X-ray crystal struc-
tures of the two enantiomers of compound 8 are shown
in Fig. 3 (Scheme 3).
Close inspection of the related structures 8, 9 and 10
reveals that each is enantiomeric and that under our
reaction conditions where there is no stereochemical
The packing of molecules in each of the crystals
reveals that the enantiomers co-crystallise in a 1:1
intimate array throughout the lattice. The packing of
˚
Fig. 2. ORTEP representation (left) of 10 with envelopes drawn at the 50% probability level. Selected bonding distances (A) and bond angles (8) are
given in Table 2. The simplified schematic structure (right) represents with dashed lines the edges of the former T6 cage that the diphenylsiloxy groups
have added across. The bridging siloxane O atoms are omitted for clarity with ‘‘SiÃ
/
Si’’ representing the SiÃ
/
OÃSi moiety.
/

4
A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ11
/
Table 1
Table 2
Selected bond lengths (A) and bond angles (8) in the crystal of 10
˚
˚
Selected bond lengths (A) and bond angles (8) in the crystal of 8
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si2Ã
Si2Ã
Si2Ã
Si2Ã
Si5Ã
Si5Ã
Si5Ã
Si5Ã
Si6Ã
Si6Ã
Si6Ã
Si6Ã
/
O4
O5
O1
C1
1.610(5)
1.615(4)
1.624(5)
1.839(5)
1.609(5)
1.625(5)
1.635(5)
1.861(4)
1.606(5)
1.610(5)
1.631(5)
1.847(5)
1.626(5)
1.629(5)
1.824(8)
1.853(8)
O1Ã
O1Ã
O2Ã
O2Ã
O3Ã
O3Ã
O4Ã
O4Ã
O5Ã
O5Ã
O6Ã
O6Ã
Si1Ã
Si2Ã
Si2Ã
Si3Ã
Si4Ã
Si4Ã
Si4Ã
/
Si1
Si2i
Si1
Si4i
Si1
Si2
Si3
Si2
Si3i
Si3
Si4
Si3
1.618(2)
1.618(2)
1.622(2)
1.632(2)
1.619(2)
1.620(2)
1.616(2)
1.621(2)
1.609(2)
1.609(2)
1.620(2)
1.623(2)
1.844(2)
1.618(2)
1.830(2)
1.834(2)
1.632(2)
1.850(2)
1.853(2)
/
/
/
/
/
/
/
O2
O1
O6
C7
/
/
/
/
/
/
/
/
O10
O9
O5
C25
O9
O6
C38
C37
/
/
/
/
/
/
/
/
/
C1
/
/
O1i
C7
/
/
/
/
C13
O2i
C19
C25
/
O4Ã
O4Ã
O5Ã
O4Ã
O5Ã
O1Ã
O2Ã
O2Ã
O1Ã
O10Ã
O10Ã
O9ÃSi5Ã
O10ÃSi5Ã
O9ÃSi5Ã
O5ÃSi5Ã
Si1ÃO1Ã
Si2ÃO2Ã
Si5ÃO9Ã
Si5Ã
O2Ã
O1Ã
O6Ã
O7Ã
O7Ã
O3Ã
O7Ã
O3Ã
O2Ã
O9Ã
O9Ã
O6Ã
O9Ã
O6Ã
C38Ã
Si1ÃO4Ã
Si1ÃO5Ã
Si6ÃO6Ã
Si1ÃO1Ã
Si2ÃO2Ã
/
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si2Ã
Si2Ã
Si2Ã
Si5Ã
Si5Ã
/
O5
O1
O1
C1
C1
C1
O1
O6
O6
108.4(2)
110.6(2)
108.8(2)
111.6(3)
107.9(3)
109.5(2)
110.1(3)
109.7(3)
107.8(2)
108.4(3)
108.9(3)
109.9(2)
109.9(3)
110.5(3)
109.2(3)
152.8(3)
143.1(3)
152.8(3)
145.1(3)
110.0(2)
107.6(2)
111.6(2)
109.0(3)
108.1(3)
109.1(3)
113.3(2)
108.0(3)
109.2(3)
109.4(3)
108.5(3)
109.5(3)
108.3(3)
108.8(3)
112.4(4)
148.2(3)
150.7(3)
138.1(3)
152.8(3)
143.1(3)
/
/
/
/
/
/
/
/
Si1Ã
Si1Ã
Si1Ã
Si3Ã
Si3iÃ
Si4ÃO6Ã
O1ÃSi1Ã
O1ÃSi1Ã
O3ÃSi1Ã
O1ÃSi1Ã
O3ÃSi1Ã
O2ÃSi1Ã
O1iÃ
Si2Ã
O1iÃ
Si2Ã
O3ÃSi2Ã
O1iÃ
Si2Ã
O3ÃSi2Ã
O4ÃSi2Ã
O5ÃSi3Ã
O5ÃSi3Ã
O4ÃSi3Ã
O5ÃSi3Ã
O4ÃSi3Ã
O6ÃSi3Ã
O6ÃSi4Ã
O6ÃSi4Ã
O2iÃ
Si4Ã
O6ÃSi4ÃC25
O2iÃ
Si4ÃC25
C19ÃSi4ÃC25
/
O1Ã
O2Ã
O3Ã
O4Ã
O5Ã
/
Si2i
Si4i
Si2
Si2
157.53(11)
142.28(11)
144.39(10)
144.61(10)
156.79(15)
147.70(10)
109.89(8)
108.98(8)
108.40(8)
109.41(9)
108.01(10)
112.13(10)
108.81(8)
109.87(8)
108.05(8)
110.16(10)
110.28(10)
109.64(9)
109.24(9)
109.21(6)
108.02(8)
108.21(10)
111.84(9)
110.29(10)
110.64(8)
105.90(9)
109.77(10)
110.40(10)
108.76(9)
111.38(10)
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
Si3
/
/
/
/
Si3
O3
O2
O2
C1
C1
C1
/
/
O9
/
/
/
/O5
/
/
/
/O5
/
/
/
/C25
/
/
/
/
C25
C25
Si2
/
/
/
/
/
/
/
/
/
/
O3
O4
/
/Si3
/
/
/
/Si6
/
/O4
/
O10Ã
/Si7
/
/
C7
/
Si2Ã
Si2Ã
Si2Ã
Si3Ã
Si3Ã
Si3Ã
Si3Ã
Si3Ã
Si3Ã
Si6Ã
Si6Ã
Si6Ã
Si6Ã
Si6Ã
/C7
/
/C7
/
/C7
/
/C7
/
/C7
/
/O4
/
/O3
/
/O6
/
/O2
/
/O6
/
/O2
/
/
C13
C13
C13
O2i
C19
/
/
C13
C13
C13
O6
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
C38
C38
C37
C37
/
/
C19
/
/
/
/
/
/
/
/
/
/
/
/
/
Si6Ã
/
C37
/
/
Si4
Si5
Si2
Si2
Si3
A similar reaction with dimethylethoxysilane, 7 and
TBAF in an 8:2:1 molar ratio gave a more complex
mixture of compounds that could be separated and
characterised by column chromatography (Scheme 4).
As well as 11, which was again isolated in less than 1%
yield and the expected T6D2 insertion product 8 (26%),
T6D1 mono-insertion product 14 (11%) and T6D2 ortho-
bis-insertion product 15 (2%) were also obtained and
structurally characterised by their single crystal X-ray
structures and 29Si-NMR spectra. Structure 14 contains
five silicon environments and the 1:1:1:2:2 peak intensity
/
/
/
/
/
/
/
/
molecules within their lattices results in each containing
a considerable number of intermolecular HÃH and CÃ
H close contacts between various positions on the alkyl
and aryl substituents of less than the sum of the
respective pairs of van der Waals radii.
/
/

A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ
/
11
5
Fig. 3. The X-ray crystal structures of the enantiomers of compound 8 which correspond to the structure types 12 (left) and 13 (right), respectively.
The hydrogen atoms are not shown for clarity.
T8, 17 cages (Scheme 5 and Table 5) from the literature
[12]. By studying the mean SiÃ
/
OÃ
/
Si and OÃ
/
SiÃ
/
O bond
angles in the different sized rings that comprise each
cage structure a number of patterns in the data are
revealed. For our purposes, we have defined an n-
membered ring within a silsesquioxane cage as one
which comprises n (SiÃ
mean OÃSiÃO bond angle is largely unaffected by
/
O) units. Most noticeably the
/
/
changes in structure, substituents at silicon and ring
size and maintains a value close to 1098, typical of a
tetrahedral silicon environment. The only exception is
for three-membered siloxane rings within cages, where
Scheme 3.
ring strain causes a slight mean OÃ
reduction. Ring strain also explains the smaller mean
Si bond angles in the three-membered siloxane
/
SiÃ
/
O bond angle
SiÃ
/
OÃ
/
rings compared with the four-membered siloxane rings
in various cages.
With the mean OÃ
largely constant, we conclude that it is the flexibility of
the SiÃOÃSi siloxane unit that allows different sized
siloxane rings and cages to be readily formed. In Table
5, the mean SiÃOÃSi bond angles that have been
/
SiÃ
/
O bond angles remaining
/
/
Scheme 4.
/
/
measured vary by over 248. For compounds 6, 8, 10
and 14 which contain both four- and five-membered
ratio in the 29Si-NMR spectrum obtained was in
agreement with the X-ray structure (Fig. 4 and Table
3). The 29Si-NMR spectrum of 15 showed three peaks
corresponding to each of the silicon environments with
an intensity ratio 1:1:2 corresponding to the relative
numbers of silicons of each type and environment. These
data complement the X-ray structure for the compound
siloxane rings, both the mean SiÃ
/
OÃ
/
Si and OÃ
/
SiÃ/O
bond angles are unexpectedly slightly smaller in the five-
membered ring than the four-membered ring when
larger angles might be predicted. This may be a result
of the greater conformational restrictions inherent in
larger five-membered rings that reduces its degrees of
freedom and constrains its geometry. Within these four
(Fig. 5 and Table 4). Unlike 8ꢀ
are achiral. However, each crystal lattice still contains
many intermolecular HÃH and CÃH close contact
/10, compounds 14 and 15
compounds, increases in the mean SiÃ
/
OÃ/Si bond angles
of the four-membered rings are also reflected in the
conjoined five-membered rings as shown in Table 5.
While compounds 6, 8 and 10 are structurally compar-
able with each other, 6 has a noticeably larger average
/
/
distances between the methyl and/or cyclohexyl sub-
stituents.
As compounds 8 and 10 are structurally analogous to
6, we can compare data from their crystal structures
along with those of 14, 15 and examples of T6, 16 and
SiÃ
/
OÃ
/
Si bond length than 8 or 10. This may be due to
the influence of the sterically bulky triphenyltin groups

6
A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ11
/
˚
Fig. 4. ORTEP representation (left) of 14 with envelopes drawn at the 50% probability level. Selected bonding distances (A) and bond angles (8) are
given in Table 3. The simplified schematic structure (right) represents with a dashed line the edge of the former T6 cage that the dimethylsiloxy group
has added across. The bridging siloxane O atoms are omitted for clarity with ‘‘SiÃ
/
Si’’ representing the SiÃ
/
OÃSi moiety.
/
causing distortion to otherwise preferred cage config-
uration in the crystal.
3. Conclusions
We have successfully performed ring-expanding in-
sertion reactions of T6 silsesquioxane cages using dialkyl
and diarylethoxysilanes to give the first reported mixed
T6D1 and T6D2 silsesquioxane cages. While these
reactions often lead to mixed product formation, the
various components could be separated by column
chromatography and characterised by multinuclear
NMR spectroscopy, matrix-assisted laser desorption/
ionisation (MALDI) mass spectroscopy and single
crystal X-ray diffraction. The reaction of T6 with dialkyl
and diaryldiethoxysilanes gives predominantly a T6D2
bis-insertion compound while the reaction of T6 with
dimethylethoxysilane gives one T6D1 mono- and various
T6D2 bis-insertion compounds as isolable components.
We have postulated that the reaction’s mechanism is
catalysed by aqueous fluoride ion and that it is the
trajectory and position of attack of the second alkox-
ysilane molecule on this T6D1 intermediate cage that
determines which T6D2 bis-insertion compound is
formed on a single molecule level.
Whilst we have not studied the mechanism of these
insertion reactions in detail, we envisage that the
insertion occurs due to the presence of trace water via
a fluoride ion-catalysed nucleophilic attack of water on
the alkoxysilane on one corner silicon of the T6 cage
leading to an edge-opened intermediate (Fig. 6). This
intermediate would then intramolecularly ring close by
nucleophilic attack with loss of the alkoxide group
resulting in the silane group having effectively been
inserted across one T6 cage edge to give a new T6D1
ring-expanded cage. The T6D2 bis- and ortho-bis-inser-
tion products could then be formed by a further
insertion reaction taking place across one of the edges
of the remaining three-membered ring in the newly
formed T6D1 cage by the attack of a further alkoxysi-
lane molecule in a similar way. In Fig. 7, insertion of a
second silane group across edge 1 would lead to the
ortho-bis product, 15, while insertion across edge 2 or 3
would lead to enantiomer structures 12 and 13, respec-
tively, in compounds 8ꢀ10. In the absence of regiocon-
/
Three of our ring-expanded products are chiral and
we have shown from their crystal structures that the
pairs of enantiomers formed as racemic mixtures co-
crystallise together. A comparison of our crystal struc-
ture data with comparable literature compounds reveals
strong similarities. In particular, we have observed that
trol, edges 2 and 3 are equivalent and a racemic mixture
would be obtained.
These novel T6D2 cages have a total of 10 arms, six
with one functionality (based on T6) and four with
alternative functionalities (based on dialkoxysilane).
Thus, these insertions provide a route to multifunctional
cages with specific geometries that we can use to
examine the interactions of arms around the cage and
use as a scaffold for developing multifunctional catalysts
or dendrimers.
while the mean OÃ
essentially constant from structure to structure, the
Si siloxane bond angle varies considerably.
/
SiÃ/O cage bond angle remains
mean SiÃ
/
OÃ
/
This is probably an important factor in explaining the
variety of stable ring, ladder and cage sizes and

A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ
/
11
7
Table 3
Selected bond lengths (A) and bond angles (8) in the crystal of 14
insertion reactions of T6 cages involving dialkyl or
diarylethoxysilanes with different alkyl and/or aryl
groups.
˚
C1Ã
C7Ã
C8Ã
/
Si1
Si2
Si2
1.842(3)
1.845(3)
1.841(3)
1.844(3)
1.843(3)
1.835(3)
1.612(2)
1.629(2)
1.623(2)
1.623(2)
1.618(2)
1.625(2)
1.638(2)
1.636(2)
1.636(2)
1.638(2)
1.625(2)
1.638(2)
1.636(2)
1.636(2)
/
/
C15Ã
C21Ã
C33Ã
O1Ã
O1Ã
O2Ã
O3Ã
O4Ã
O4Ã
O5Ã
O6Ã
O7Ã
O7Ã
O4Ã
O5Ã
O6Ã
O7Ã
/
Si4
Si5
Si7
4. Experimental
/
/
4.1. General
/
Si1
Si2
Si2
Si4
Si1
Si4
Si5
Si7
Si5
Si7
Si4
Si5
Si7
Si5
/
The TBAF solution in THF used contained 5% of
time
/
/
water. Matrix-assisted laser desorption/ionisationꢀ
/
/
of flight (MALDIꢀTOF) mass spectrometry studies
/
/
were carried out by the University of Southampton
using DBH as the matrix and dichloromethane as
solvent. All NMR measurements were made on JEOL
EX300 or EX400 FT instruments fitted with multi-
nuclear probes. Spectra were recorded at 20 8C using
/
/
/
/
/
/
˚
CDCl3 dried over 4 A molecular sieves as solvent and an
/
external reference of tetramethylsilane. Details of the X-
ray crystal structure studies also undertaken by the
University of Southampton can be found separately in
Section 4.2.
/
Si1Ã
Si3Ã
Si4Ã
Si1Ã
Si5Ã
Si6Ã
Si5Ã
Si5Ã
Si7Ã
O1Ã
O1Ã
O4Ã
O1Ã
O4Ã
O8Ã
O2Ã
O2Ã
O1Ã
O2Ã
O1Ã
C8Ã
O3Ã
O3Ã
O4Ã
O3Ã
O4Ã
O10Ã
O8ÃSi5Ã
O8ÃSi5Ã
O7ÃSi5Ã
O8ÃSi5Ã
O7ÃSi5Ã
O5ÃSi5Ã
O10Ã
O10Ã
O6ÃSi7Ã
O10ÃSi7Ã
O6ÃSi7Ã
O7ÃSi7Ã
/
O1Ã
O2Ã
O3Ã
O4Ã
O5Ã
O6Ã
O7Ã
O8Ã
O10Ã
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si2Ã
Si2Ã
Si2Ã
Si2Ã
Si2Ã
Si2Ã
Si4Ã
Si4Ã
Si4Ã
Si4Ã
Si4Ã
Si4Ã
/
Si2
Si2
Si3
Si4
Si6
Si7
Si7
Si1
148.70(13)
156.77(14)
145.05(13)
158.50(13)
133.29(13)
128.24(12)
129.29(12)
139.09(12)
140.63(13)
109.04(10)
108.48(11)
109.04(10)
109.63(12)
110.56(11)
110.06(11)
110.36(11)
108.32(13)
107.83(13)
108.28(14)
107.49(13)
114.55(15)
108.59(10)
109.75(10)
109.13(10)
109.61(12)
110.06(11)
109.68(12)
109.01(10)
109.71(10)
106.50(10)
108.64(12)
110.23(12)
112.69(11)
108.60(10)
108.85(10)
106.53(10)
111.13(12)
111.30(11)
110.28(12)
/
/
/
/
/
/
/
/
4.1.1. Synthesis of bis-insertion compounds 8ꢀ10 of
/
/
/
hexacyclohexylsilsequioxane 7 from dialkyl and
diaryldiethoxysilanes
/
/
/
/
In a typical reaction, 7 (0.255 g, 0.314 mmol), dialkyl
or diaryldiethoxysilane (0.629 mmol) and TBAF (0.157
mmol) (0.157 cm3 of a 1 M THF solution) were
dissolved in dichloromethane (50 cm3) and stirred at
room temperature (r.t.) for 16 h. The solution was then
extracted with distilled water (20 cm3) and further with
dichloromethane (200 cm3). The organic layer was dried
over anhydrous magnesium sulfate and the solvent
removed under vacuum. The resulting white residue
was washed with acetone (20 cm3) and purified by
column chromatography (SiO2/hexane) to give a crystal-
line product 8, 9 or 10. Colourless crystals suitable for
X-ray structure analysis were obtained by recrystallisa-
/
/Si4
/
/
O4
O8
O8
C1
C1
C1
O1
C8
C8
C7
C7
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
C7
/
/O4
/
/
O10
O10
C15
C15
/
/
tion from a 1:1 dichloromethaneꢀ
/
acetone solvent mix-
/
/
ture.
/
/
/
/C15
/
/O7
4.1.1.1. Bis-dimethylsilyl-hexacyclohexylsilsequioxane
T6D2 insertion compound 8. Yield: 0.096 g (32%); dH (300
MHz, CDCl3): 0.07 (6H, s, CH3), 0.09 (6H, s, CH3), 0.69
(6H, m, CH(CH2)2), 1.21 (30H, m, CH2) and 1.69 (30H,
m, CH2); dC (300 MHz, CDCl3): 0.00 (SiCH3), 0.23
(SiCH3), 23.10 (CH(CH2)2), 23.19 (CH(CH2)2), 23.43
(CH(CH2)2), 26.25 (CH2), 26.31 (CH2), 26.43 (CH2),
26.61 (CH2), 27.23 (CH2) and 27.28 (CH2); dSi (400
/
/O5
/
/O5
/
/
C21
C21
C21
/
/
/
/
/
Si7Ã
Si7Ã
/O6
/
/O7
/
/O7
/
/C33
MHz, CDCl3): ꢃ
67.85 (SiCy) and ꢃ
DIꢀ
TOF): 959.52 [MHꢂ], 960.50, 961.48 and 962.46.
/
17.73 (SiMe2), ꢃ
/
65.95 (SiCy), ꢃ
/
/
/C33
/
68.24 (SiCy) (1:1:1:1); m/z (MAL-
/
/C33
/
structures that are known in the silsesquioxane chem-
istry. We are currently undertaking work on similar
4.1.1.2. Bis-diethylsilyl-hexacyclohexylsilsequioxane
T6D2 insertion compound 9. Yield: 0.043 g (17%); dH (300

8
A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ11
/
˚
Fig. 5. ORTEP representation (left) of 15 with envelopes drawn at the 50% probability level. Selected bonding distances (A) and bond angles (8) are
given in Table 4. The simplified schematic structure (right) represents with dashed lines the edges of the former T6 cage that the dimethylsiloxy groups
have added across. The bridging siloxane O atoms are omitted for clarity with ‘‘SiÃ
/
Si’’ representing the SiÃ
/
OÃSi moiety.
/
MHz, CDCl3): 0.51 (8H, m, SiCH2), 0.70 (6H, m,
CH(CH2)2), 0.95 (12H, m, CH3), 1.22 (30H, m, CH2
of Cy) and 1.70 (30H, m, CH2 of Cy); dC (300 MHz,
CDCl3): 6.30 (SiCH2), 6.75 (SiCH2), 23.41 (CH(CH2)2),
23.47 (CH(CH2)2), 23.89 (CH(CH2)2), 26.54 (CH2),
26.80 (CH2), 26.85 (CH2), 27.48 (CH2), 27.60 (CH2)
cm3) and further with dichloromethane (200 cm3). The
organic layer was dried over anhydrous magnesium
sulfate and the solvent removed under vacuum. The
resulting white residue was washed with acetone (20
cm3) and purified by column chromatography (SiO2/
hexane) to give three fractions 8, 14 and 15 as white
crystalline solids. Colourless crystals of each material
suitable for X-ray structure analysis were obtained by
and 30.91 (CH3); dSi (400 MHz, CDCl3): ꢃ
/
18.10
68.74
(SiEt2), ꢃ66.00 (SiCy), ꢃ68.03 (SiCy) and ꢃ
/
/
/
(SiCy) (1:1:1:1); m/z (MALDIꢀ
/
TOF): 1036.99 [Mꢂ
/
recrystallisation from a 1:1 dichloromethaneꢀ
solvent mixture.
/
acetone
Naꢂ], 1038.01, 1039.03, 1040.05, 1041.07 and 1042.09.
4.1.1.3. Bis-diphenylsilyl-hexacyclohexylsilsequioxane
4.1.2.1. Fraction 1*
silsequioxane T6D2 insertion compound 8. See Section
4.1.1.1 above.
/
bis-dimethylsilyl-hexacyclohexyl-
T6D2 insertion compound 10. Yield: 0.075 g (23%); dH
(300 MHz, CDCl3): 0.38 (6H, m, CH(CH2)2), 1.22 (30H,
m, CH2), 1.68 (30H, m, CH2), 7.33 (12H, m, CH of Ph)
and 7.59 (8H, m, CH of Ph); dC (300 MHz, CDCl3):
23.33 (CH(CH2)2), 26.47 (CH2), 27.42 (CH2), 127.48
(CSi of Ph), 127.58 (CH of Ph), 134.02 (CH of Ph) and
4.1.2.2. Fraction 2*mono-dimethylsilyl-hexacyclohexyl-
/
silsequioxane T6D1 insertion compound 14. Yield: 0.026 g
(11%); dH (300 MHz, CDCl3): 0.08 (3H, s, CH3), 0.11
(3H, s, CH3), 0.76 (6H, m, CH(CH2)2), 1.22 (30H, m,
CH2) and 1.71 (30H, m, CH2); dC (300 MHz, CDCl3):
0.00 (SiCH3), 0.46 (SiCH3), 22.55 (CH(CH2)2), 23.08
(CH(CH2)2), 23.33 (CH(CH2)2), 26.20 (CH2), 26.31
(CH2), 26.36 (CH2), 26.46 (CH2), 26.68 (CH2), 26.73
(CH2), 26.85 (CH2), 27.34 (CH2), 27.38 (CH2), 27.47
(CH2), 27.49 (CH2) and 27.58 (CH2); dSi (400 MHz,
134.35 (CH of Ph); dSi (400 MHz, CDCl3): ꢃ
(SiPh2), ꢃ65.71 (SiCy), ꢃ67.70 (SiCy) and ꢃ
(SiCy) (1:1:1:1); m/z (MALDIꢀ
Naꢂ].
/
46.03
68.00
/
/
/
/
TOF): 1230.78 [Mꢂ
/
4.1.2. Synthesis of mono- and bis-insertion compounds
(8, 14 and 15) of hexacyclohexylsilsequioxane 7 from
dimethylethoxysilane
Compound 7 (0.217 g, 0.268 mmol), dimethylethox-
ysilane (0.112 g, 1.070 mmol) and TBAF (0.134 mmol)
(0.134 cm3 of a 1 M THF solution) were dissolved in
dichloromethane (50 cm3) and stirred at r.t. for 16 h.
The solution was then extracted with distilled water (20
CDCl3): ꢃ
membered ring), ꢃ
ring), ꢃ66.76 (CySi of four-membered ring) and ꢃ
67.30 (CySi of four-membered ring) (1:1:2:1:2); m/z
(MALDIꢀTOF): 907.45 [Mꢂ
Naꢂ].
/
17.84 (Me2Si), ꢃ
/
56.18 (CySi of three-
/58.65 (CySi of three-membered
/
/
/
/

A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ
/
11
9
Table 4
Selected bond lengths (A) and bond angles (8) in the crystal of 15
˚
Molecule 1
Molecule 2
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si4Ã
Si4Ã
Si4Ã
Si4Ã
Si5Ã
Si5Ã
Si5Ã
Si5Ã
Si8Ã
Si8Ã
Si8Ã
Si8Ã
O5Ã
O5Ã
O1Ã
O5Ã
O1Ã
O4Ã
O8Ã
O8Ã
O4Ã
O8Ã
O4Ã
O3Ã
O5Ã
O5Ã
O11Ã
O5ÃSi5Ã
O11ÃSi5Ã
C25ÃSi5Ã
O11ÃSi8Ã
O11ÃSi8Ã
O8ÃSi8Ã
O11ÃSi8Ã
O8ÃSi8ÃC35
O10ÃSi8ÃC35
Si1ÃO1Ã
Si3ÃO3Ã
Si1ÃO4Ã
Si1ÃO5Ã
Si4ÃO8Ã
Si7Ã
Si8Ã
/
O5
1.611(2)
1.616(2)
1.621(2)
Si9Ã
Si9Ã
Si9Ã
Si9Ã
Si12Ã
Si12Ã
Si12Ã
Si12Ã
Si13Ã
Si13Ã
Si13Ã
Si13Ã
Si16Ã
Si16Ã
Si16Ã
Si16Ã
O12Ã
O12Ã
O16Ã
O12Ã
O16Ã
O15Ã
O14Ã
O14Ã
O15Ã
O14Ã
O15Ã
O19Ã
O16Ã
O16Ã
O22Ã
O16Ã
O22Ã
C65Ã
O21Ã
O21Ã
O22Ã
O21Ã
O22Ã
O19Ã
Si9ÃO12Ã
Si12ÃO14Ã
Si12ÃO15Ã
Si9ÃO16ÃSi13
Si12ÃO19ÃSi16
Si16ÃO21Ã
Si16ÃO22Ã
/
O12
O16
O15
C41
1.609(2)
1.615(2)
1.627(2)
/O1
/
/O4
/
/C1
1.847(3)
/
1.848(3)
/O8
1.621(2)
1.622(2)
1.630(2)
/
O14
O15
O19
C59
O16
O22
C65
C66
O21
O22
O19
C75
1.619(2)
1.620(2)
1.621(2)
/O4
/
/O3
/
Scheme 5.
/C19
1.844(3)
/
1.842(3)
/O5
1.633(2)
/
1.618(2)
/
O11
C25
C26
O11
O8
1.638(2)
1.834(3)
1.838(3)
/
1.627(2)
1.835(4)
1.841(4)
Table 5
A summary of mean SiÃ
arranged by ring size for various silsesquioxane cage compounds
/
/
/
OÃ
/
Si and OÃ
/
SiÃ
/
O bond angle data (8)
/
/
/
1.623(2)
/
1.617(2)
characterised by X-ray crystallography (one memberꢁ1 SiÃO unit)
/
/
/
1.626(2)
/
1.620(2)
/O10
1.627(2)
/
1.623(2)
Compound Bond angle Ring size
type
/C35
1.843(3)
/
1.854(3)
/
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si1Ã
Si4Ã
Si4Ã
Si4Ã
Si4Ã
Si4Ã
Si4Ã
Si5Ã
Si5Ã
Si5Ã
C26
C26
C26
/
O1
107.09(11)
110.02(10)
109.41(10)
110.89(13)
110.55(12)
108.87(12)
108.85(10)
108.74(11)
109.37(10)
110.29(12)
109.42(12)
110.14(12)
108.89(10)
108.85(14)
109.50(12)
109.33(13)
108.87(14)
111.36(16)
109.57(11)
108.31(10)
109.13(11)
109.19(12)
108.43(12)
112.19(13)
155.91(14)
136.14(13)
152.62(14)
148.56(13)
142.46(12)
144.65(13)
139.99(13)
/
Si9Ã
Si9Ã
Si9Ã
Si9Ã
Si9Ã
Si9Ã
Si12Ã
Si12Ã
Si12Ã
Si12Ã
Si12Ã
Si12Ã
Si13Ã
Si13Ã
Si13Ã
Si13Ã
Si13Ã
Si13Ã
Si16Ã
Si16Ã
Si16Ã
Si16Ã
Si16Ã
Si16Ã
/
O16
O15
O15
C41
C41
C41
108.21(12)
108.69(11)
109.57(11)
110.52(12)
109.80(13)
110.00(12)
109.84(10)
108.85(11)
108.89(11)
110.31(12)
107.80(12)
111.13(12)
109.96(11)
108.41(16)
108.79(16)
107.68(16)
109.04(14)
112.91(15)
107.12(11)
110.00(11)
109.89(11)
110.63(13)
110.93(12)
108.27(12)
160.49(14)
146.63(13)
143.24(14)
146.50(14)
149.44(13)
153.97(14)
149.42(15)
Three-mem- Four-mem-
bered
Five-mem-
bered
/
/O4
/
/
bered
/
/O4
/
/
/
/C1
/
/
16
14
15
10
17
8
SiÃ
OÃ
SiÃ
OÃ
SiÃ
OÃ
SiÃ
OÃ
SiÃ
OÃ
SiÃ
OÃ
SiÃ
OÃ
/
OÃ
SiÃ
OÃ
SiÃ
OÃ
SiÃ
OÃ
SiÃ
OÃ
SiÃ
OÃ
SiÃ
OÃ
SiÃ
/
Si
O
Si
O
Si
O
Si
O
Si
O
Si
O
Si
O
130.4
106.4
130.3
106.5
134.7
108.8
144.6
109.3
147.4
109.3
149.0
109.4
149.5
108.9
149.8
109.3
154.8
109.1
ꢀ/
ꢀ/
/
/C1
/
/
/
/
/
/C1
/
/
/
/
144.5
/
/O4
/
/
O15
O19
O19
C59
C59
C59
O22
C65
C65
C66
C66
/
/
109.2
/
/O3
/
/
/
/
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
/
ꢀ/
ꢀ/
147.2
109.1
/
/O3
/
/
/
/
/
/
/
C19
C19
C19
O11
C25
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
ꢀ/
ꢀ/
149.6
108.8
151.5
109.0
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/C25
/
/
/
/
/
/
/
/
/
6
/
/
ꢀ
ꢀ
/
/
/
/
/
/
/
/
/
/
/
/C66
/
/O8
/
/
O22
O19
O19
C75
C75
C75
/
/O10
/
/
ꢃ
/
18.25 (Me2Si), ꢃ
/
67.50 (CySi) and ꢃ
TOF): 981.7 [Mꢂ
/
68.94 (CySi)
Naꢂ].
/
/O10
/
/
(1:1:2); m/z (MALDIꢀ
/
/
/
/C35
/
/
/
/
/
/
/
/
/
/
4.2. X-ray crystallography
/
/
Si2
Si4
Si4
Si5
Si8
/
/
Si10
Si11
Si9
/
/
/
/
/
/
/
/
All structures were measured on a Nonius Kappa
CCD diffractometer (f scans and v scans to fill
/
/
/
/
/
/
/
/
asymmetric unit or Ewald sphere) using graphite
˚
/
O10Ã
/Si8
/
/Si15
monochromated Moꢀ
/
Ka radiation (lꢁ0.71073 A).
/
/
O11Ã
/Si5
/
/Si13
The data collection was performed in a c rotation
mode. A list of crystal data, data collection, structure
solution and refinement parameters is provided in Table
6. The raw intensity data were corrected for Lorentz and
polarisation effects as well as absorption correction
(SORTAV) [19]. Structure solutions were searched and
refined by direct methods (SHELXS 97) [20] and differ-
ence Fourier analyses (SHELXL 97) [21], respectively,
based on F2. Atom form factors for neutral atoms were
taken from the literature [22]. Second and third row
elements were allowed to refine anisotropically with
hydrogen atoms assumed in idealised positions riding on
their pivot atoms.
4.1.2.3. Fraction 3*ortho-bis-dimethylsilyl-hexacyclo-
/
hexylsilsequioxane T6D2 insertion compound 15. Yield:
0.005 g (2%); dH (300 MHz, CDCl3): 0.10 (12H, s, CH3),
0.68 (6H, m, CH(CH2)2), 1.20 (30H, m, CH2) and 1.70
(30H, m, CH2); dC (300 MHz, CDCl3): 0.00 (SiCH3),
0.72 (SiCH3), 23.03 (CH(CH2)2), 23.77 (CH(CH2)2),
26.47 (CH2), 26.63 (CH2), 26.76 (CH2), 27.38 (CH2),
27.45 (CH2) and 29.58 (CH2); dSi (400 MHz, CDCl3):

10
A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ11
/
Fig. 6. A possible mechanism for silane insertion reactions into T6 silsesquioxane cages catalysed by aqueous fluoride ion.
5. Supplementary material
Crystallographic data for the structures reported in
this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary pub-
lication Nos. CCDC 209191ꢀ
can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge, CB2 1EZ, UK (Fax: ꢂ44-
/
209194. Copies of the data
/
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
Acknowledgements
We would like to thank Dow Corning for their
support of this work.
References
[1] F.J. Feher, K.J. Weller, Organometallics 9 (1990) 2638.
[2] E.G. Shockey, A.G. Bolf, P.F. Jones, J.J. Schwab, K.P. Chaffee,
T.S. Haddad, J.D. Lichtenhan, Appl. Organomet. Chem. 13
(1999) 311.
Fig. 7. The regiochemical outcomes of a second edge insertion
reaction into T6D1 mono-insertion silsesquioxane cage compounds.
[3] F.J. Feher, K.J. Weller, J.J. Schwab, Organometallics 14 (1995)
2009.

A.R. Bassindale et al. / Journal of Organometallic Chemistry 687 (2003) 1ꢀ
/
11
11
Table 6
Crystal data, data collection and refinement parameters for compounds 8, 10, 14 and 15
8
10
14
15
Formula
C40H78O11Si8
959.74
C60H86O11Si8
1208.01
C38H70O10Si7
883.57
C40H78O11Si8
959.74
Molecular weight
Colour
Morphology
Colourless
Plate
Colourless
Block
Colourless
Block
Colourless
Tablet
Crystal size (mm)
Crystal system
Space group
0.20ꢄ
Triclinic
¯
P1
/
0.20ꢄ
/
0.05
0.20ꢄ
Monoclinic
C2/c
/
0.10ꢄ
/0.10
0.20ꢄ
Monoclinic
P21/n
/
0.10ꢄ
/0.10
0.30ꢄ
Triclinic
¯
P1
/
0.20ꢄ0.05
/
/
/
Unit cell dimensions
˚
a (A)
˚
10.1268(5)
11.4163(5)
22.2125(13)
84.476(2)
88.585(2)
88.878(2)
2554.9(2)
2
19.4021(5)
14.5900(5)
24.6258(8)
90
15.8472(4)
15.9765(4)
19.6690(5)
90
11.203(5)
21.240(5)
23.033(5)
96.415(5)
97.912(5)
101.753(5)
5259.0(3)
4
b (A)
˚
c (A)
a (8)
b (8)
112.995(2)
90
107.0180(10)
90
g (8)
3
V (A )
˚
6417.1(3)
4
1.250
4761.8(2)
4
1.232
Z
Dcalc (g cmꢃ3
F(0 0 0)
)
1.248
1036
1.212
2072
2584
1904
Temperature (K)
Reflections collected
Independent reflections
Rint
120(2)
18225
120(2)
17492
5544
293(2)
24947
8329
120(2)
58806
8597
0.1215
18125
0.0635
0.0614
0.0793
u Range (8)
h range
2.91ꢀ
/
25.03
2.93ꢀ
/
25.03
2.92ꢀ
/
25.03
2.97ꢀ25.03
/
ꢃ
/
12, 12
13, 13
26, 26
ꢃ
/
23, 21
17, 17
29, 29
ꢃ
/
18, 18
18, 19
23, 22
ꢃ
/
13, 12
25, 25
27, 27
k range
l range
Final R indices [F2ꢀ
R indices (all data)
S (goodness-of-fit on F2)
Nref
ꢃ
/
ꢃ
/
ꢃ
/
ꢃ
/
ꢃ/
ꢃ/
ꢃ/
ꢃ/
/
2s(F2)] R1ꢁ
R1ꢁ
/
0.0892, wR2ꢁ
0.2120, wR2ꢁ
/
0.2068 R1ꢁ/0.0399, wR2ꢁ
/
0.0921 R1ꢁ
/
0.0462, wR2ꢁ
/
0.1054 R1ꢁ
0.1189 R1ꢁ
1.008
/
0.0491, wR2ꢁ
/
0.1018
0.1163
/
/
0.2547 R1ꢁ/0.0712, wR2ꢁ
/
0.1038 R1ꢁ
/
0.0856, wR2ꢁ
/
/0.0925, wR2ꢁ
/
1.017
8597
532
1.037
5544
357
0.998
8329
498
18125
1071
Npar
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