New mono- and diethynylsiloxysilsesquioxanes-efficient procedures for their synthesis

Article abstract of DOI:10.1039/c4dt01950d

Ethynyl-substituted siloxysilsesquioxanes are promising building blocks for a wide range of substances based on a POSS/DDSQ core, especially for (oligo-)polymer syntheses and modifications (the formation of hybrid materials with interesting photophysical and mechanical properties). In this study, we report on a series of new mono- and diethynylsiloxysilsesquioxanes formed via an efficient and highly selective one-pot process from silsesquioxanes with reactive Si-OH groups based on sequential condensation, hydrolysis, chlorination and substitution reactions. All newly synthesized compounds were isolated and characterized by spectroscopic methods.

Full text of DOI:10.1039/c4dt01950d

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New mono- and diethynylsiloxysilsesquioxanes –
efficient procedures for their synthesis†
Cite this: Dalton Trans., 2014, 43,
13201
Beata Dudziec,*a Monika Rzonsowska,a Bogdan Marciniec,b Dariusz Brząkalskia and
Bartosz Woźniaka
Ethynyl-substituted siloxysilsesquioxanes are promising building blocks for a wide range of substances
based on a POSS/DDSQ core, especially for (oligo-)polymer syntheses and modifications (the formation
of hybrid materials with interesting photophysical and mechanical properties). In this study, we report on
a series of new mono- and diethynylsiloxysilsesquioxanes formed via an efficient and highly selective
one-pot process from silsesquioxanes with reactive Si–OH groups based on sequential condensation,
hydrolysis, chlorination and substitution reactions. All newly synthesized compounds were isolated and
characterized by spectroscopic methods.
Received 27th June 2014,
Accepted 6th July 2014
DOI: 10.1039/c4dt01950d
www.rsc.org/dalton
groups.6c–g To these derivatives one should also add silses-
quioxanes bearing very reactive ethynyl functionalities.7
Introduction
Polyhedral silsesquioxanes (POSS) of the general formula
Ethynyl- or alkynyl-substituted silsesquioxanes (title com-
(RSiO3/2)n, containing a well-defined nanosized, three dimen- pounds) seem to be promising reagents for further modifi-
sional inorganic cubic core of Si–O–Si moieties, constitute a cations because of their interesting electronic properties.
broad class of organic–inorganic hybrid compounds. The There are few examples of one –CC– triple bond in a functional
most important POSS materials are the cube-like T8 derivatives chain of the POSS or DDSQ core. These are based on the intro-
(RSiO3/2)8, which have found a wide range of technological duction of one or two alkynyl- or ethynyl functionalities in
applications and can be easily functionalized with one or eight stages, e.g. via subsequent catalytic reactions, i.e. metathesis
reactive groups. These systems are of particular strong interest and Sonogashira coupling8 or via hydrolytic condensation and
to scientists not only because of their construction, but also consecutive alkynyl–imide or alkynyl–alkyl formation (used for
mainly because of their unique chemical and physical pro- rare examples of DDSQ functionalization with two alkynyl
perties (solubility, non-flammability, oxidation resistance, and groups).9 There are some examples of compounds with eight
very good dielectric properties). Organo-functionalized silses- alkynyl groups introduced into the POSS core.10 Yet, all these
quioxanes have been proven to constitute an excellent new methods are based on functionalization with alkynyl- or
class of nanofillers and modifiers used for the preparation of ethynyl-substituted reagents, although Csp–Csp triple bond
nanostructured composites with a unique set of attributes.1 moieties are usually located at some distance (separated by an
They are also widely used as silica-supported catalysts,1,2 den- organic group, e.g. phenyl, alkyl, etc.) from the Si–O–Si core.
drimers,3 in optoelectronics4 (e.g. OLEDs5) and as biocompati- Attempts at introducing the ethynyl group in the vicinity of the
ble materials or “scaffolds” for liquid crystals.6 The cubic core have been rare. There is a method based on the
development of new and effective methods for POSS synthesis hydrolytic condensation of a POSS (tri-)silanol form with
with various functional groups influences the number of their EtOSiMe2CCH, performed in toluene, followed by addition of
possible applications. This is particularly important in terms p-toluenesulfonic acid.7 Yet, the above mentioned method
of reactive functional groups attached to
a POSS core, entails certain difficulties, e.g. the necessity of p-toluenesulfonic
e.g. vinyl, amino, epoxy, methacryloxy, and chloropropyl acid addition means that it is of the utmost importance to
control the pH value to avoid POSS structural degradation or
rearrangements of other functional groups at POSS. There is
aDepartment of Organometallic Chemistry, Faculty of Chemistry, Adam Mickiewicz
University, Umultowska 89b, 61-614 Poznan, Poland.
growing interest in combining POSS/DDSQ units with organic
moieties, e.g. via copper-catalyzed Huisgen 1,3-dipolar cyclo-
addition producing an imidazole ring that is a spacer between
these two groups and also affects their physical properties.6c,11
The double-decker silsesquioxane methods of functionali-
zation include hydrolytic condensation reactions, hydrosily-
E-mail: beata.dudziec@gmail.com; Fax: (+48)61 8291508; Tel: (+48)61 8291366
bFaculty of Chemistry and Center for Advanced Technologies, Adam Mickiewicz
University, Grunwaldzka 6, 60-780 Poznan, Poland
†Electronic supplementary information (ESI) available. See DOI: 10.1039/
c4dt01950d
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lation, etc.11e–j Because of the considerable importance of and Synthesis of mono- and diethynylsiloxysilsesquioxanes in a
even greater prospect for the functionalized, DDSQ-based com- one-pot reaction using TCCA
pounds to become precursors for the synthesis of a wide range
of materials (also oligo- and polymeric), this new diethynyl-
derivative of silsesquioxane would be particularly interesting.
Trisilanolisobutyl POSS (1,3,5,7,9,11,14-heptaisobutyltricyclo-
[7.3.3.15,11]heptasiloxane-endo-3,7,14-triol) (1A-1) was chosen
as a model compound for monoethynylsiloxy POSS systems
In view of the unchanged reactivity of the spC–H bond at
(6A) (Scheme 1). The diethynylsiloxy DDSQ system (6B) was
the silsesquioxane core, we expect that these alternative
synthesized according to the procedure proposed for (6A)
(Scheme 2). 1A-1 was used as a starting material to be trans-
procedures for the synthesis of the title compounds
would enhance the availability of
silsesquioxanes.
a
new variety of
formed in a sequence of two hydrolytic condensations and
hydrolysis to hydrodimethylsiloxy(heptaisobutyl)silsesqui-
oxane (4A-1), according to known procedures13 (Scheme 1).
In the next step, the possibility of Cl-group substitution at
the Si atom in 4A-1 was tested and, to this end, an attempt was
made to transform the Si–H bond into Si–Cl. There are a few
known chlorinating agents that could be used to perform the
chlorination: Cl2, HCl, phosphorous trichloride, allyl chloride
Over the last few years, the scientific interest of the Prof.
Marciniec team has turned to polyhedral oligosilsesquioxanes
(POSS), and the T8 system in particular, as well as sphero-
silicates. The research conducted in this area has concerned,
among other aspects, the improvement of procedures for the
synthesis of functionalized mono- and octa-substituted silses-
quioxanes and spherosilicates via, e.g., hydrolytic conden-
sation and nucleophilic substitution.6e,f,12 This paper presents
the synthesis of new, mono- and diethynylsiloxy-functionalized
silsesquioxanes (also the double-decker type of silsesquioxane
(DDSQ)) utilizing easy to handle and commercially
available silanol precursors of silsesquioxanes (POSS and
DDSQ).
Results and discussion
A series of condensation reactions enabled us to obtain silses-
quioxanes with reactive Si–H bond(s). We wanted to combine
the properties of mild and effective chlorinating agents, i.e.
TCCA (trichloroisocyanuric acid) for the Si–H to Si–Cl reaction,
and obtain very reactive chlorosyloxy-substituted silsesqui-
oxanes. Their subsequent reaction with ethynylmagnesium
bromide enabled us to obtain mono- and diethynylsiloxy-sub-
stituted POSS in a one-pot reaction with high yields and
selectivity in a short time. Since the above procedure involves
five steps, one may have doubts about its overall efficiency.
However, the yields of the title compounds are very good and
the procedure exploits commercial reagents. In parallel, a
more direct method was also worked out – involving three
steps – to obtain the title silsesquioxanes, with high yields as
well, via hydrolytic condensation of silanol (3A and 3B) pre-
cursors of POSS and DDSQ with ClSiMe2CCH. The title com-
pounds may play an important role in the further synthesis of
new organo-POSS and organo-DDSQ unsaturated derivatives,
ligands and especially in materials science, i.e. (oligo-)
polymer creation and modifications.
Scheme 1 One-pot procedure for synthesis of monoethynylsiloxysil-
sesquioxane (POSS) (6A).
The possibilities of introducing one or two ethynyl groups
to POSS/DDSQ units were tested and the conclusion was that,
mainly for steric reasons, it would be more possible to accom-
plish this idea via incorporating an ethynylsiloxy unit to the
Si–O–Si core than the bare ethynyl group. Therefore, two paths
of the reactions were performed, i.e. involving mono- and
diethynylsiloxysilsesquioxanes (POSS – type A and DDSQ –
type B).
Scheme 2 One-pot procedure for the synthesis of diethynylsiloxysil-
sesquioxane (DDSQ) (6B).
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in the presence of activated charcoal on palladium, etc.14
However, there are major difficulties in their usage arising
from one or more of the following: low yield, difficulty in
handling the reagent, and tedious workup procedures to
obtain a pure product. It was found that organic chloroimides,
especially trichloroisocyanuric acid (TCCA) or 1,3,5-trichloro-
1,3,5-2,4,6-(1H,3H,5H)-trione, known since 1902, belong to this
large group of compounds and would be the best chlorinating
agent to transform silicon hydrides to the chloro derivatives.
The reason for choosing this compound was to develop an
efficient process involving a simple isolation procedure follow-
ing the reaction which required only filtration to remove the
insoluble by-product. Varaprath and co-workers proposed a
very effective and selective protocol for the synthesis of chloro-
silanes from silicon hydrides.15 This method has been shown
to work perfectly even with sterically demanding trimethylsil-
oxy-substituted siloxanes with an Si–H bond, so it was
decided that the method should be used for our purpose. In
the tests, hydro-POSS and dihydro-DDSQ derivatives were
necessary for effective chlorination reactions from Si–H to
Si–Cl and this procedure using TCCA was proved to be very
effective16 (Scheme 1). Hydrodimethylsiloxy-(heptaisobutyl)-
silsesquioxane (4A-1) was used to optimize the chlorination
procedure using TCCA in a 10% excess for an Si–H group. The
use of several solvents from two groups: aliphatic ethers, i.e.
diethyl ether, THF, and chlorinated aliphatic hydrocarbons,
i.e. dichloromethane, chloroform and 1,2-dichloroethane, was
also explored. After several attempts, it was found that the
reaction was most effective and selective when performed in
dichloromethane or THF. When using DCM as the solvent,
4A-1 was added to a slurry of TCCA in CH2Cl2 and the reaction
proceeded under reflux in 2–10 h. However, when THF was
used, the reagents were added in reverse order. TCCA was
added by means of a solid addition funnel to 4A-1 dissolved in
THF cooled to −20 °C. The changed order of the addition of
substances for the reactions in THF as well as the lower temp-
erature (additional heating is not advisable) were necessary to
prevent chlorination of THF by TCCA. The observations were
similar to those presented by Varaprath and co-workers.15
Several tests were performed to optimize the reaction con-
ditions and during the reaction path the intermediate pro-
ducts were isolated and the structure of chlorodimethylsiloxy
(heptaisobutyl)silsesquioxane (5A-1) was confirmed on the
basis of 29Si NMR analysis – a disappearing signal of the Si–H
group (4A-1) at −2.99 ppm and the apparent signal of the Si–Cl
group (5A-1) at −18.93 ppm. As the resulting product, i.e.
chlorodimethylsiloxy(heptaisobutyl)silsesquioxane (5A-1), is
reactive toward moisture with a tendency to condense, it is rec-
ommended to preserve dry and inert conditions. After iso-
lation, which included filtration from unreacted TCCA and
cyanuric acid and simple evaporation of the solvent, chlorosil-
oxy-POSS (5A-1) was then transformed via a known method
with ethynylmagnesium bromide to ethynylsiloxy(heptaiso-
butyl)-silsesquioxanes (6A-1). The desired product 6A-1 was
isolated according to standard procedures for post-Grignard
mixtures that involved extraction of the desired ethynylsiloxy
Table 1 One-pot synthesis of ethynyl-substituted siloxysilsesquioxanes
(6A) and (6B) – from silanol forms of POSS and DDSQ
Reaction
conditions
Isolated
yield [%]
Substrate
Structure
a
(1A-1) R = i-Bu
(1A-2) R = Et
(1A-3) R = i-Oc
(1A-4) R = c-C5H9
(1A-5) R = c-C6H11
(1A-6) R = Ph
(6A-1)
(6A-2)
(6A-3)
(6A-4)
(6A-5)
(6A-6)
(6B-7)
92
91
89
90
91
84
82
b
(1B-7) R = Ph
a Condensation: SiCl4, THF, RT, 24 h – second condensation ClSiMe2H,
THF, RT, 24 h; hydrolysis: THF–H2O, reflux, 12 h; TCCA chlorination:
THF, 45 °C, 24 h; Grignard reaction: 0.5 M HCCMgBr in THF, 45 °C,
24 h. b Condensation: SiCl4 for POSS, MeSiCl3 for DDSQ, THF, RT, 24 h
– second condensation for POSS-ClSiMe2H, THF, RT, 24 h; hydrolysis:
THF–CHCl3, H2O, HCl, RT, 6–12 h; TCCA chlorination: THF, 45 °C,
24 h; Grignard reaction: 0.5 M HCCMgBr in THF, 45 °C, 48–72 h.
POSS followed by solvent evaporation. Column chromato-
graphy of a crude product afforded pure – over 92% yield –
6A-1 in the form of a powder. Given our optimized conditions,
the scope of this one-pot reaction sequence using various tri-
silanol silsesquioxanes (1A) with different alkyl or phenyl
groups attached to the seven silicon atoms in the corners of
POSS (Table 1) was investigated. Since the synthetic procedures
require the absence of by-products originating from unreacted
trisilanol POSS (1A), all the condensation reactions were per-
formed with 0.5–1% excess of chlorosilanes and with dry and
deoxidized THF or CHCl3. Under these conditions, stoichio-
metric condensation processes and simple filtration from the
resulting [Et3NH]+Cl− salt followed by evaporation of the
solvent (and possible chlorosilane residues) was sufficient to
obtain the desired product for the consecutive reaction. There
was also no isolation step after the reaction with TCCA (the
structure of the resulting chlorosiloxy-POSS derivative via 29Si
NMR was controlled only for tests). Resulting chlorinated sil-
oxysilsesquioxane (5A-1) was subjected to reaction with a 0.5 M
THF solution of ethynylmagnesium bromide (24 h, 45 °C). The
optimized amount of the ethynyl-Grignard reagent was a
2 molar excess for each Si–Cl bond. After post-Grignard silses-
quioxane extraction and solvent evaporation, the crude
product was purified via column chromatography (silica gel,
eluent: n-hexane–diethyl ether for silsesquioxanes with alkyl
substituents R = alkyl and n-hexane–CH2Cl2 for R = aryl) giving
over 84% of the total yield.
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The protocol used for one-pot synthesis of ethynyl-siloxysil-
sesquioxanes (6A) was the same for alkyl substituents.
However, to acquire 6A-6 with phenyl groups attached to
silicon in seven corners of POSS in quantitative yield, it was
required to perform the hydrolysis process using CHCl3
instead of THF.9a The other steps of the procedure were the
same, except for the crude product purification. Because of the
very poor solubility of 6A-6 in n-hexane, the eluent was n-hexane–
CH2Cl2 3 : 7. All ethynylsiloxysilsesquioxanes (6A) obtained but
one were white solids, and only for the R = iOc at the silicon
corner (6A-3) was the final product a highly viscous, trans-
parent oil (similar to the starting trisilanol (1A-3)).
The proposed and optimized procedure for the synthesis of
ethynyldimethylsiloxy(heptaisobutyl)silsesquioxanes (6A-1) with
respective changes in R substituents as in the heptaphenyl
derivative (6A-6) enabled us to subject the tetrasilanol form of
double-decker silsesquioxanes (1B) to the same reaction
sequence. The diethynylsiloxy DDSQ system (6B) was syn-
thesized according to the procedure proposed for 6A-6
(Scheme 2). The structure of 6B-7 was confirmed by 29Si NMR
spectroscopy and it was revealed that two geometrical isomers
were obtained, i.e. trans-6B-7 and cis-6B-7. Signals at δ =
−63.84, −79.16 and −79.44 ppm were assigned to the trans
Scheme 3 Procedure for the synthesis of mono- and diethynylsiloxysil-
sesquioxanes (POSS and DDSQ) via condensation with ClMe2SiCCH.
techniques. 1H, 13C, and 29Si NMR spectra were recorded at
298 K on Varian XL 300 MHz, Bruker Avance 400 MHz and
500 MHz spectrometers at r.t. using CDCl3 as a solvent.
Chemical shifts are reported in ppm with reference to the
1
residual solvent (CHCl3) peaks for H and 13C and to TMS for
29Si. FT-IR spectra were recorded on a Bruker Tensor 27
Fourier transform spectrophotometer equipped with a SPECAC
Golden Gate diamond ATR unit. In all cases, 16 scans at a
resolution of 2 cm−1 were used to record the spectra. Elemen-
tal analyses were carried out on a Vario EL III instrument.
MALDISynapt G2-S HDMS (Waters Inc.) mass spectrometer
equipped with an electrospray ion source and Q-TOF type
mass analyzer. The instrument was controlled and the
recorded data were processed using the MassLynx V4.1 soft-
ware package (Waters Inc. ). The trisilanol precursors of POSS
(1) were obtained from Hybrid Plastics, other chemicals were
purchased from Aldrich. The column chromatography was per-
formed with silica gel 60 (70–230 mesh; Fluka). All solvents
and liquid reagents were dried and distilled under an argon
atmosphere prior to use.
isomer, whereas signals at
δ = −63.84, 79.16, −79.25,
−79.64 ppm were assigned to the cis isomer. The 29Si NMR
spectrum assignments of 6B-7 were consistent with the results
of Ervithayasuporn and Kawakami11e–g and the cis-6B-7
was successfully separated by recrystallization in the THF–
methanol solvent mixture.
Synthesis of mono- and diethynylsiloxysilsesquioxanes via a
condensation reaction using chloroethynyldimethylsilane
The possibility of reducing the number of steps in the above
procedure was also considered and it was checked whether it
could be realized in 3 steps instead of 5. A common hydrolytic
condensation procedure13 for the parallel reaction of mono-
hydroxy POSS (3A) and dihydroxy DDSQ (3B) with chloro-ethynyl-
dimethylsilane was tested. The main disadvantage of this
method for the synthesis of (6A) and (6B) is that silane is not
commercially available and is not that easy to handle because
of the synthetic procedure and its low boiling point. ClMe2-
SiCCH can be prepared from diethynyltetramethyldisiloxane
using HMPA, which has been described by S. Ichinohe and co-
workers.17 Several tests of known condensation type reac-
tions13c between mono- and dihydroxy-silsesquioxanes (POSS
and DDSQ) and chloroethynyl-dimethylsilane were performed
to obtain all of the expected ethynyl-substituted silsesquiox-
anes (POSS and DDSQ) (Scheme 3) that were isolated with
high yields and their analytical data are identical to the ones
obtained according to the first method.
General procedure for the synthesis of ethynyl-substituted
siloxysilsesquioxanes with an R-alkyl substituent (6A-1 as an
example) in a one-pot reaction using TCCA
A mixture consisting of 2.65 g (3.35 mmol) of 1,3,5,7,9,11,14-
heptaisobutyltricyclo [7.3.3.15,11
]
heptasiloxane-endo-3,7,14-
triol (1A-1) (dried under vacuum for 30 min prior to use),
1.17 g of triethylamine (11.72 mmol) and 100 mL of THF was
placed under an Ar atmosphere in a Schlenk bomb flask fitted
with a plug valve. The flask was placed in an ice bath and
569 mg (3.35 mmol) of SiCl4 was added to the mixture drop-
wise. The suspension was stirred for 24 h at room temperature
and filtered on a glass frit (of triethylammonium chloride
salt). The precipitate was washed with THF (3 × 5 mL) and
solvent was evaporated. The residue left after evaporation
was dissolved in a mixture of 100 mL of THF and 3.01 g
(167 mmol) of H2O and heated at 65 °C for 18 h. After the reac-
Experimental
General methods and chemicals
All syntheses and manipulations were carried out under tion was complete (GC analysis), the THF was evaporated and
an argon atmosphere using standard Schlenk-line and vacuum the residue was extracted with n-hexane 3 × 15 mL. The
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organic phase was collected and dried with MgSO4. Evapor- The only difference is in the final purification of crude ethynyl-
ation gave the analytically pure product hydroxy(heptaisobutyl) siloxy(heptaisobutyl)silsesquioxane (6A-6) which was per-
silsesquioxane (3A-1) in the form of a white powder. The con- formed by column chromatography on silica gel, eluting with
densation procedure for the resulting 3A-1 was repeated with n-hexane–CH2Cl2 at a ratio of 7 : 3 (Rf = 0.73; UV).
364 mg (3.22 mmol) of chlorodimethylsilane and 666 mg
Experimental characterization data of isolated products
(4.83 mmol) of Et3N in the same reaction and isolation con-
ditions as for 1A-1. The hydrodimethylsiloxy(heptaisobutyl)sil-
1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(isobutyl)-
sesquioxane (4A-1) was obtained in the form of a white powder. pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (6A-1). Yield: 2.85 g
A Schlenk bomb flask fitted with a plug valve and connected to (92%); white solid; Rf = 0.75 (n-hexane–Et2O, 11 : 1; I2); IR
a gas and vacuum line was charged under argon with 2.5 g (ATR) (cm−1): 3297, 2953–2870, 2042, 1464–1332, 1229–955,
1
(2.8 mmol) hydrodimethylsiloxy(hepta-isobutyl)silsesquioxane 836–684, 559; H NMR (400 MHz, CDCl3) δ(ppm) = 0.30 (s, 6H
(4A-1) in 13 mL THF and was cooled down in an acetone/dry ice SiCH3), 0.60–0.64 (m, 14H CH2), 0.95–0.98 (m, 42H CH3),
bath to −20 °C and 0.24 g (1.04 mmol) of trichloroisocyanuric 1.83–1.93 (m, 7H CH), 2.38 (s, 1H, HCCSi); 13C NMR
acid (TCCA) was quickly added in one portion. The reaction (100 MHz, CDCl3) δ(ppm) = 1.55 (SiMe3), 22.37, 22.79, 25.71,
was being mixed and kept to heat up to room temperature for 88.45 (CC), 92.11 (CC); 29Si NMR (99 MHz, CDCl3) δ(ppm) =
3 h. In order to remove unreacted TCCA and the resulting −16.05 (HCCSi), −66.89, −67.00, −67.86, −109.83. HRMS (FD):
cyanuric acid precipitate, the mixture was filtered via cannula calcd for C32H70O13Si9Na: 937.2638; found: 937.2626. Anal.
under an Ar atmosphere. The organic phase with chloro- calcd for C32H70O13Si9 (%): C 41.97; H 7.71; found: C 41.87;
dimethylsiloxy(heptaisobutyl)silsesquioxane (5A-1) was added H 7.73.
dropwise at the same time to 12.6 mL ethynylmagnesium
1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(ethyl)pentacyclo-
bromide (0.5 M in THF) and placed in a two-necked, 50 mL [9.5.1.13,9.15,15.17,13]octasiloxane (6A-2). Yield: 2.19 g (91%);
flask equipped with a reflux condenser and connected to a gas white solid; Rf = 0.73 (n-hexane–Et2O, 11 : 1; I2); IR (ATR)
and vacuum line. The reaction mixture was maintained at a (cm−1): 3288, 2964–2882, 2040, 1461–1414, 1253–1011,
1
temperature of 45 °C for 24 h. After completion of the reaction, 836–692, 526; H NMR (400 MHz, CDCl3) δ(ppm) = 0.32 (s, 6H
unreacted ethynylmagnesium bromide was decomposed with SiCH3), 0.61 (qu, J = 8 Hz, 14H, CH2), 0.99 (tr, J = 8 Hz, 42H
4 mL of i-PrOH and water and the product was extracted with CH3), 2.39 (s, 1H, HCCSi); 13C NMR (100.6 MHz, CDCl3)
CHCl3 (3 × 5 mL). The organic phase was collected and dried δ(ppm) = 1.45 (SiMe3), 3.97, 6.42, 88.26 (CC), 92.22 (CC); 29Si
with MgSO4. Evaporation gave the crude product ethynylsiloxy NMR (99 MHz, CDCl3) δ(ppm) = −15.58 (HCCSi), −65.01,
(heptaisobutyl)silsesquioxane (6A-1) which was purified by −65.69, −65.73, −108.86. HRMS (FD): calcd for
column chromatography on silica gel, eluting with n-hexane– C18H42O13Si9Na: 741.0446; found: 741.0427. Anal. calcd for
diethyl ether at a ratio of 11 : 1 (Rf = 0.75; I2).
C18H42O13Si9 (%): C 30.06; H 5.89; found: C 29.95; H 5.91.
1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(isooctyl)penta-
General procedure for the synthesis of ethynyl-substituted
siloxysilsesquioxanes with an R-phenyl substituent (6A-6 as an
example) in a one-pot reaction using TCCA
cyclo[9.5.1.13,9.15,15.17,13]octasiloxane
(6A-3). Yield:
3.89
(89%); pale yellowish oil. Rf = 0.76 (n-hexane–Et2O, 11 : 1; I2);
IR (ATR) (cm−1): 3296, 2951–2869, 2042, 1467–1364, 1226,
The procedure for condensation of both the trisilanol precur- 1–92, 908, 844–683, 566; 1H NMR (400 MHz, CDCl3, 300 K)
sor of heptaphenylsilsesquioxane (1A-6) and the tetrasilanol δ(ppm) = 0.3 (s, 6H SiCH3), 0.54–0.59, 0.74–0.78, 0.90, 1.00,
precursor of octaphenylsilsesquioxane (1B-7) is analogous to 1.10–1.14, 1.30–1.34, 1.85 (m, i-Oc), 2.37 (s, 1H, HCCSi); 13C
that described for 1A-1. The next step, i.e. the hydrolysis (con- NMR (100 MHz, CDCl3) δ(ppm) = 1.61 (SiMe3), 23.38, 23.44,
sistent with literature9a) that is described below for synthesis 24.96, 25.66, 30.13, 31.15, 38.13, 53.93, 88.42 (CC), 92.16 (CC);
of 6A-6, is different from that for alkyl derivatives. The crude 29Si NMR (99 MHz, CDCl3) δ(ppm)
= −16.21 (HCCSi),
condensation product, i.e. chloro(heptaphenyl)-silsesquioxane −66.99, −67.19, −68.19, −110.00. HRMS (FD): calcd for
(2A-6) (prepared from 2.65 g (2.84 mmol) (1,3,5,7,9,11,14- C54H114O13Si9Na: 1245.6080; found: 1245.6068. Anal. calcd for
heptaphenyltricyclo [7.3.3.15,11] heptasiloxane-endo-3,7,14-triol) C54H114O13Si9 (%): C 52.98; H 9.39; found: C 52.89; H 9.41.
(1A-6)), was dissolved in THF (1.5 mL) and chloroform (4 mL),
1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(cyclopentyl)-
(6A-4). Yield:
water (4 mL) and diluted HCl (0.5 mL) over a 90 min period. pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane
The aqueous layer was separated and extracted twice with 3.02 g (90%); white solid; Rf = 0.80 (n-hexane–Et2O, 11 : 1; I2);
chloroform. The combined organic layers were extracted with IR (ATR) (cm−1): 3293, 2948, 2865, 2041, 1450, 1253–949,
1
water first, then with diluted HCl, water, saturated brine and 834–676, 513; H NMR (500 MHz, CDCl3) δ(ppm) = 0.31 (s, 6H
then dried with MgSO4. After filtration, the solvent was SiCH3), 0.96–1.03, 1.46–1.60, 1.71–1.76 (m, c-C5H9), 2.38 (s,
removed under vacuum to obtain the product, i.e. hydroxy(hepta- 1H, HCCSi); 13C NMR (125 MHz, CDCl3) δ(ppm) = 1.56
phenyl)silsesquioxane (3A-6), in the form of a white residue. (SiMe3), 22.10, 22.17, 26.98, 27.28, 29.70, 88.47 (CC), 92.08
The subsequent steps in the reaction procedures are analogous (CC); 29Si NMR (99 MHz, CDCl3) δ(ppm) = −15.90 (HCCSi),
to those described for alkyl substituents (see the General pro- −65.87, −65.45, −65.87, −108.54. HRMS (FD): calcd for
cedure for the synthesis of ethynyl-substituted siloxysilses- C39H70O13Si9Na: 1021.2638; found: 1021.2618. Anal. calcd for
quioxanes with an R-alkyl substituent (example for 6A-1)). C39H70O13Si9 (%): C 46.85; H 7.06; found: C 46.84; H 7.07.
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These assignments are in good accord with those in the main reagent, i.e. ClMe2SiCCH, is not commercially available.
literature.7a
Both methods lead to mono- and diethynylsiloxy silsesqui-
1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(cyclohexyl)- oxanes with good yields and are comparably effective. The pro-
pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane
(6A-5). Yield: ducts were isolated and characterized by spectroscopic
3.34 g (91%); white solid; Rf = 0.81 (n-hexane–Et2O, 11 : 1; I2); methods (1H, 13C and 29Si NMR, FT-IR, HRMS). These alterna-
IR (ATR) (cm−1): 3292, 2920, 2848, 2040, 1446, 1269–1011, tive procedures for the synthesis of the title compounds will
1
893–674, 507; H NMR (500 MHz, CDCl3) δ(ppm) = 0.33 (s, 6H enhance the availability of a new variety of silsesquioxanes.
SiCH3), 0.74–0.80, 1.20–1.28, 1.70–1.78 (m, c-C6H11), 2.39 (s,
1H, HCCSi); 13C NMR (125 MHz, CDCl3) δ(ppm) = 1.64
(SiMe3), 22.99, 23.09, 26.50, 26.83, 27.48, 88.57 (CC), 92.13
Acknowledgements
(CC); 29Si NMR (99 MHz, CDCl3) δ(ppm) = −16.14 (HCCSi),
The authors gratefully acknowledge support from the Ministry
−67.83, −67.97, −68.66, −108.55. HRMS (FD): calcd for
of Science and Higher Education (Poland), grant no.
C46H84O13Si9Na: 1119.3733; found: 1119.3734. Anal. calcd for
UMO-2012/05/D/ST5/03348 and from the European Regional
C46H84O13Si9 (%): C, 50.32; H, 7.71; found: C 50.16; H 7.73.
Development Fund, Operational Programme Innovative
1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(phenyl)-penta-
Economy, 2007-2013, project no. UDA-POIG.01.03.01-30-173/
cyclo[9.5.1.13,9.15,15.17,13]octasiloxane (6A-6). Yield: 2.97
g
09-02.
(84%); white solid; Rf = 0.73 (n-hexane–CH2Cl2, 7 : 3; UV); IR
(ATR) (cm−1): 3281, 3074–2965, 2038, 1595, 1430, 1260–997,
834–694, 558.; 1H NMR (500 MHz, CDCl3) δ(ppm) = 0.31 (s, 6H
SiCH3), 2.27 (s, 1H, HCCSi), 6.88–7.73 (Ph); 13C NMR
(125 MHz, CDCl3) δ(ppm) = 1.48 (SiMe3), 87.99 (CC), 92.75
(CC), 127.78–128.86, 130.08, 130.78, 134.18–134.29 (Ph); 29Si
NMR (99 MHz, CDCl3) δ(ppm) = −14.62 (HCCSi), −78.03,
78.30, −78.33, −108.88. HRMS (FD): calcd for C46H42O13Si9Na:
1077.0446; found: 1077.0448. Anal. calcd for C46H42O13Si9 (%):
C 52.34; H 4.01; found: C 52.19; H 4.02.
Notes and references
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In summary, we have devised new versatile one-pot protocols
for high yield preparation of new ethynylsiloxysilsesquioxanes
bearing one or two ethynyl groups in a POSS/DDSQ molecule.
Because of the potential importance of this new ethynyl func-
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