DaltonTransactions

PAPER

Cite this: Dalton Trans., 2014, 43,13201

Received 27th June 2014,Accepted 6th July 2014

DOI: 10.1039/c4dt01950d

www.rsc.org/dalton

New mono- and diethynylsiloxysilsesquioxanes –efficient procedures for their synthesis†

Beata Dudziec,*a Monika Rzonsowska,a Bogdan Marciniec,b Dariusz Brząkalskia andBartosz 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.

Introduction

Polyhedral silsesquioxanes (POSS) of the general formula(RSiO3/2)n, containing a well-defined nanosized, three dimen-sional inorganic cubic core of Si–O–Si moieties, constitute abroad class of organic–inorganic hybrid compounds. Themost important POSS materials are the cube-like T8 derivatives(RSiO3/2)8, which have found a wide range of technologicalapplications and can be easily functionalized with one or eightreactive groups. These systems are of particular strong interestto scientists not only because of their construction, but alsomainly because of their unique chemical and physical pro-perties (solubility, non-flammability, oxidation resistance, andvery good dielectric properties). Organo-functionalized silses-quioxanes have been proven to constitute an excellent newclass of nanofillers and modifiers used for the preparation ofnanostructured composites with a unique set of attributes.1

They are also widely used as silica-supported catalysts,1,2 den-drimers,3 in optoelectronics4 (e.g. OLEDs5) and as biocompati-ble materials or “scaffolds” for liquid crystals.6 Thedevelopment of new and effective methods for POSS synthesiswith various functional groups influences the number of theirpossible applications. This is particularly important in termsof reactive functional groups attached to a POSS core,e.g. vinyl, amino, epoxy, methacryloxy, and chloropropyl

groups.6c–g To these derivatives one should also add silses-quioxanes bearing very reactive ethynyl functionalities.7

Ethynyl- or alkynyl-substituted silsesquioxanes (title com-pounds) seem to be promising reagents for further modifi-cations because of their interesting electronic properties.There are few examples of one –CC– triple bond in a functionalchain of the POSS or DDSQ core. These are based on the intro-duction of one or two alkynyl- or ethynyl functionalities instages, e.g. via subsequent catalytic reactions, i.e. metathesisand Sonogashira coupling8 or via hydrolytic condensation andconsecutive alkynyl–imide or alkynyl–alkyl formation (used forrare examples of DDSQ functionalization with two alkynylgroups).9 There are some examples of compounds with eightalkynyl groups introduced into the POSS core.10 Yet, all thesemethods are based on functionalization with alkynyl- orethynyl-substituted reagents, although Csp–Csp triple bondmoieties are usually located at some distance (separated by anorganic group, e.g. phenyl, alkyl, etc.) from the Si–O–Si core.Attempts at introducing the ethynyl group in the vicinity of thecubic core have been rare. There is a method based on thehydrolytic condensation of a POSS (tri-)silanol form withEtOSiMe2CCH, performed in toluene, followed by addition ofp-toluenesulfonic acid.7 Yet, the above mentioned methodentails certain difficulties, e.g. the necessity of p-toluenesulfonicacid addition means that it is of the utmost importance tocontrol the pH value to avoid POSS structural degradation orrearrangements of other functional groups at POSS. There isgrowing interest in combining POSS/DDSQ units with organicmoieties, e.g. via copper-catalyzed Huisgen 1,3-dipolar cyclo-addition producing an imidazole ring that is a spacer betweenthese two groups and also affects their physical properties.6c,11

The double-decker silsesquioxane methods of functionali-zation include hydrolytic condensation reactions, hydrosily-

†Electronic supplementary information (ESI) available. See DOI: 10.1039/c4dt01950d

aDepartment of Organometallic Chemistry, Faculty of Chemistry, Adam Mickiewicz

University, Umultowska 89b, 61-614 Poznan, Poland.

E-mail: beata.dudziec@gmail.com; Fax: (+48)61 8291508; Tel: (+48)61 8291366bFaculty of Chemistry and Center for Advanced Technologies, Adam Mickiewicz

University, Grunwaldzka 6, 60-780 Poznan, Poland

This journal is © The Royal Society of Chemistry 2014 Dalton Trans., 2014, 43, 13201–13207 | 13201

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lation, etc.11e–j Because of the considerable importance of andeven greater prospect for the functionalized, DDSQ-based com-pounds to become precursors for the synthesis of a wide rangeof materials (also oligo- and polymeric), this new diethynyl-derivative of silsesquioxane would be particularly interesting.In view of the unchanged reactivity of the spC–H bond atthe silsesquioxane core, we expect that these alternativeprocedures for the synthesis of the title compoundswould enhance the availability of a new variety ofsilsesquioxanes.

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 thesynthesis of functionalized mono- and octa-substituted silses-quioxanes and spherosilicates via, e.g., hydrolytic conden-sation and nucleophilic substitution.6e,f,12 This paper presentsthe synthesis of new, mono- and diethynylsiloxy-functionalizedsilsesquioxanes (also the double-decker type of silsesquioxane(DDSQ)) utilizing easy to handle and commerciallyavailable silanol precursors of silsesquioxanes (POSS andDDSQ).

Results and discussion

A series of condensation reactions enabled us to obtain silses-quioxanes with reactive Si–H bond(s). We wanted to combinethe 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 ethynylmagnesiumbromide enabled us to obtain mono- and diethynylsiloxy-sub-stituted POSS in a one-pot reaction with high yields andselectivity in a short time. Since the above procedure involvesfive steps, one may have doubts about its overall efficiency.However, the yields of the title compounds are very good andthe procedure exploits commercial reagents. In parallel, amore direct method was also worked out – involving threesteps – to obtain the title silsesquioxanes, with high yields aswell, 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 ofnew organo-POSS and organo-DDSQ unsaturated derivatives,ligands and especially in materials science, i.e. (oligo-)polymer creation and modifications.

The possibilities of introducing one or two ethynyl groupsto 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 theSi–O–Si core than the bare ethynyl group. Therefore, two pathsof the reactions were performed, i.e. involving mono- anddiethynylsiloxysilsesquioxanes (POSS – type A and DDSQ –

type B).

Synthesis of mono- and diethynylsiloxysilsesquioxanes in aone-pot reaction using TCCA

Trisilanolisobutyl POSS (1,3,5,7,9,11,14-heptaisobutyltricyclo-[7.3.3.15,11]heptasiloxane-endo-3,7,14-triol) (1A-1) was chosenas a model compound for monoethynylsiloxy POSS systems(6A) (Scheme 1). The diethynylsiloxy DDSQ system (6B) wassynthesized according to the procedure proposed for (6A)(Scheme 2). 1A-1 was used as a starting material to be trans-formed in a sequence of two hydrolytic condensations andhydrolysis to hydrodimethylsiloxy(heptaisobutyl)silsesqui-oxane (4A-1), according to known procedures13 (Scheme 1).

In the next step, the possibility of Cl-group substitution atthe Si atom in 4A-1 was tested and, to this end, an attempt wasmade to transform the Si–H bond into Si–Cl. There are a fewknown chlorinating agents that could be used to perform thechlorination: Cl2, HCl, phosphorous trichloride, allyl chloride

Scheme 1 One-pot procedure for synthesis of monoethynylsiloxysil-sesquioxane (POSS) (6A).

Scheme 2 One-pot procedure for the synthesis of diethynylsiloxysil-sesquioxane (DDSQ) (6B).

Paper Dalton Transactions

13202 | Dalton Trans., 2014, 43, 13201–13207 This journal is © The Royal Society of Chemistry 2014

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in the presence of activated charcoal on palladium, etc.14

However, there are major difficulties in their usage arisingfrom one or more of the following: low yield, difficulty inhandling the reagent, and tedious workup procedures toobtain 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 thislarge group of compounds and would be the best chlorinatingagent to transform silicon hydrides to the chloro derivatives.The reason for choosing this compound was to develop anefficient process involving a simple isolation procedure follow-ing the reaction which required only filtration to remove theinsoluble by-product. Varaprath and co-workers proposed avery effective and selective protocol for the synthesis of chloro-silanes from silicon hydrides.15 This method has been shownto work perfectly even with sterically demanding trimethylsil-oxy-substituted siloxanes with an Si–H bond, so it wasdecided that the method should be used for our purpose. Inthe tests, hydro-POSS and dihydro-DDSQ derivatives werenecessary for effective chlorination reactions from Si–H toSi–Cl and this procedure using TCCA was proved to be veryeffective16 (Scheme 1). Hydrodimethylsiloxy-(heptaisobutyl)-silsesquioxane (4A-1) was used to optimize the chlorinationprocedure using TCCA in a 10% excess for an Si–H group. Theuse 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, wasalso explored. After several attempts, it was found that thereaction was most effective and selective when performed indichloromethane or THF. When using DCM as the solvent,4A-1 was added to a slurry of TCCA in CH2Cl2 and the reactionproceeded under reflux in 2–10 h. However, when THF wasused, the reagents were added in reverse order. TCCA wasadded by means of a solid addition funnel to 4A-1 dissolved inTHF cooled to −20 °C. The changed order of the addition ofsubstances for the reactions in THF as well as the lower temp-erature (additional heating is not advisable) were necessary toprevent chlorination of THF by TCCA. The observations weresimilar 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 thebasis of 29Si NMR analysis – a disappearing signal of the Si–Hgroup (4A-1) at −2.99 ppm and the apparent signal of the Si–Clgroup (5A-1) at −18.93 ppm. As the resulting product, i.e.chlorodimethylsiloxy(heptaisobutyl)silsesquioxane (5A-1), isreactive 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 andcyanuric acid and simple evaporation of the solvent, chlorosil-oxy-POSS (5A-1) was then transformed via a known methodwith ethynylmagnesium bromide to ethynylsiloxy(heptaiso-butyl)-silsesquioxanes (6A-1). The desired product 6A-1 wasisolated according to standard procedures for post-Grignardmixtures that involved extraction of the desired ethynylsiloxy

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 phenylgroups attached to the seven silicon atoms in the corners ofPOSS (Table 1) was investigated. Since the synthetic proceduresrequire the absence of by-products originating from unreactedtrisilanol POSS (1A), all the condensation reactions were per-formed with 0.5–1% excess of chlorosilanes and with dry anddeoxidized THF or CHCl3. Under these conditions, stoichio-metric condensation processes and simple filtration from theresulting [Et3NH]+Cl− salt followed by evaporation of thesolvent (and possible chlorosilane residues) was sufficient toobtain the desired product for the consecutive reaction. Therewas also no isolation step after the reaction with TCCA (thestructure of the resulting chlorosiloxy-POSS derivative via 29SiNMR was controlled only for tests). Resulting chlorinated sil-oxysilsesquioxane (5A-1) was subjected to reaction with a 0.5 MTHF solution of ethynylmagnesium bromide (24 h, 45 °C). Theoptimized amount of the ethynyl-Grignard reagent was a2 molar excess for each Si–Cl bond. After post-Grignard silses-quioxane extraction and solvent evaporation, the crudeproduct was purified via column chromatography (silica gel,eluent: n-hexane–diethyl ether for silsesquioxanes with alkylsubstituents R = alkyl and n-hexane–CH2Cl2 for R = aryl) givingover 84% of the total yield.

Table 1 One-pot synthesis of ethynyl-substituted siloxysilsesquioxanes(6A) and (6B) – from silanol forms of POSS and DDSQ

SubstrateReactionconditions Structure

Isolatedyield [%]

(1A-1) R = i-Bu a (6A-1) 92(1A-2) R = Et (6A-2) 91(1A-3) R = i-Oc (6A-3) 89(1A-4) R = c-C5H9 (6A-4) 90(1A-5) R = c-C6H11 (6A-5) 91(1A-6) R = Ph b (6A-6) 84(1B-7) R = Ph (6B-7) 82

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.

Dalton Transactions Paper

This journal is © The Royal Society of Chemistry 2014 Dalton Trans., 2014, 43, 13201–13207 | 13203

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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 tosilicon in seven corners of POSS in quantitative yield, it wasrequired to perform the hydrolysis process using CHCl3instead of THF.9a The other steps of the procedure were thesame, except for the crude product purification. Because of thevery poor solubility of 6A-6 in n-hexane, the eluent was n-hexane–CH2Cl2 3 : 7. All ethynylsiloxysilsesquioxanes (6A) obtained butone were white solids, and only for the R = iOc at the siliconcorner (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 ofethynyldimethylsiloxy(heptaisobutyl)silsesquioxanes (6A-1) withrespective changes in R substituents as in the heptaphenylderivative (6A-6) enabled us to subject the tetrasilanol form ofdouble-decker silsesquioxanes (1B) to the same reactionsequence. 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 NMRspectroscopy and it was revealed that two geometrical isomerswere 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 transisomer, whereas signals at δ = −63.84, 79.16, −79.25,−79.64 ppm were assigned to the cis isomer. The 29Si NMRspectrum assignments of 6B-7 were consistent with the resultsof Ervithayasuporn and Kawakami11e–g and the cis-6B-7was successfully separated by recrystallization in the THF–methanol solvent mixture.

Synthesis of mono- and diethynylsiloxysilsesquioxanes via acondensation reaction using chloroethynyldimethylsilane

The possibility of reducing the number of steps in the aboveprocedure was also considered and it was checked whether itcould be realized in 3 steps instead of 5. A common hydrolyticcondensation procedure13 for the parallel reaction of mono-hydroxy POSS (3A) and dihydroxy DDSQ (3B) with chloro-ethynyl-dimethylsilane was tested. The main disadvantage of thismethod for the synthesis of (6A) and (6B) is that silane is notcommercially available and is not that easy to handle becauseof the synthetic procedure and its low boiling point. ClMe2-SiCCH can be prepared from diethynyltetramethyldisiloxaneusing 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 (POSSand DDSQ) and chloroethynyl-dimethylsilane were performedto obtain all of the expected ethynyl-substituted silsesquiox-anes (POSS and DDSQ) (Scheme 3) that were isolated withhigh yields and their analytical data are identical to the onesobtained according to the first method.

ExperimentalGeneral methods and chemicals

All syntheses and manipulations were carried out underan argon atmosphere using standard Schlenk-line and vacuum

techniques. 1H, 13C, and 29Si NMR spectra were recorded at298 K on Varian XL 300 MHz, Bruker Avance 400 MHz and500 MHz spectrometers at r.t. using CDCl3 as a solvent.Chemical shifts are reported in ppm with reference to theresidual solvent (CHCl3) peaks for 1H and 13C and to TMS for29Si. FT-IR spectra were recorded on a Bruker Tensor 27Fourier transform spectrophotometer equipped with a SPECACGolden Gate diamond ATR unit. In all cases, 16 scans at aresolution 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 spectrometerequipped with an electrospray ion source and Q-TOF typemass analyzer. The instrument was controlled and therecorded 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 werepurchased from Aldrich. The column chromatography was per-formed with silica gel 60 (70–230 mesh; Fluka). All solventsand liquid reagents were dried and distilled under an argonatmosphere prior to use.

General procedure for the synthesis of ethynyl-substitutedsiloxysilsesquioxanes with an R-alkyl substituent (6A-1 as anexample) 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 wasplaced under an Ar atmosphere in a Schlenk bomb flask fittedwith a plug valve. The flask was placed in an ice bath and569 mg (3.35 mmol) of SiCl4 was added to the mixture drop-wise. The suspension was stirred for 24 h at room temperatureand filtered on a glass frit (of triethylammonium chloridesalt). The precipitate was washed with THF (3 × 5 mL) andsolvent was evaporated. The residue left after evaporationwas 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-tion was complete (GC analysis), the THF was evaporated andthe residue was extracted with n-hexane 3 × 15 mL. The

Scheme 3 Procedure for the synthesis of mono- and diethynylsiloxysil-sesquioxanes (POSS and DDSQ) via condensation with ClMe2SiCCH.

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organic phase was collected and dried with MgSO4. Evapor-ation gave the analytically pure product hydroxy(heptaisobutyl)silsesquioxane (3A-1) in the form of a white powder. The con-densation procedure for the resulting 3A-1 was repeated with364 mg (3.22 mmol) of chlorodimethylsilane and 666 mg(4.83 mmol) of Et3N in the same reaction and isolation con-ditions as for 1A-1. The hydrodimethylsiloxy(heptaisobutyl)sil-sesquioxane (4A-1) was obtained in the form of a white powder.A Schlenk bomb flask fitted with a plug valve and connected toa gas and vacuum line was charged under argon with 2.5 g(2.8 mmol) hydrodimethylsiloxy(hepta-isobutyl)silsesquioxane(4A-1) in 13 mL THF and was cooled down in an acetone/dry icebath to −20 °C and 0.24 g (1.04 mmol) of trichloroisocyanuricacid (TCCA) was quickly added in one portion. The reactionwas being mixed and kept to heat up to room temperature for3 h. In order to remove unreacted TCCA and the resultingcyanuric acid precipitate, the mixture was filtered via cannulaunder an Ar atmosphere. The organic phase with chloro-dimethylsiloxy(heptaisobutyl)silsesquioxane (5A-1) was addeddropwise at the same time to 12.6 mL ethynylmagnesiumbromide (0.5 M in THF) and placed in a two-necked, 50 mLflask equipped with a reflux condenser and connected to a gasand vacuum line. The reaction mixture was maintained at atemperature of 45 °C for 24 h. After completion of the reaction,unreacted ethynylmagnesium bromide was decomposed with4 mL of i-PrOH and water and the product was extracted withCHCl3 (3 × 5 mL). The organic phase was collected and driedwith MgSO4. Evaporation gave the crude product ethynylsiloxy(heptaisobutyl)silsesquioxane (6A-1) which was purified bycolumn chromatography on silica gel, eluting with n-hexane–diethyl ether at a ratio of 11 : 1 (Rf = 0.75; I2).

General procedure for the synthesis of ethynyl-substitutedsiloxysilsesquioxanes with an R-phenyl substituent (6A-6 as anexample) in a one-pot reaction using TCCA

The procedure for condensation of both the trisilanol precur-sor of heptaphenylsilsesquioxane (1A-6) and the tetrasilanolprecursor of octaphenylsilsesquioxane (1B-7) is analogous tothat described for 1A-1. The next step, i.e. the hydrolysis (con-sistent with literature9a) that is described below for synthesisof 6A-6, is different from that for alkyl derivatives. The crudecondensation product, i.e. chloro(heptaphenyl)-silsesquioxane(2A-6) (prepared from 2.65 g (2.84 mmol) (1,3,5,7,9,11,14-heptaphenyltricyclo [7.3.3.15,11] heptasiloxane-endo-3,7,14-triol)(1A-6)), was dissolved in THF (1.5 mL) and chloroform (4 mL),water (4 mL) and diluted HCl (0.5 mL) over a 90 min period.The aqueous layer was separated and extracted twice withchloroform. The combined organic layers were extracted withwater first, then with diluted HCl, water, saturated brine andthen dried with MgSO4. After filtration, the solvent wasremoved under vacuum to obtain the product, i.e. hydroxy(hepta-phenyl)silsesquioxane (3A-6), in the form of a white residue.The subsequent steps in the reaction procedures are analogousto those described for alkyl substituents (see the General pro-cedure for the synthesis of ethynyl-substituted siloxysilses-quioxanes with an R-alkyl substituent (example for 6A-1)).

The only difference is in the final purification of crude ethynyl-siloxy(heptaisobutyl)silsesquioxane (6A-6) which was per-formed by column chromatography on silica gel, eluting withn-hexane–CH2Cl2 at a ratio of 7 : 3 (Rf = 0.73; UV).

Experimental characterization data of isolated products

1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(isobutyl)-pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (6A-1). Yield: 2.85 g(92%); white solid; Rf = 0.75 (n-hexane–Et2O, 11 : 1; I2); IR(ATR) (cm−1): 3297, 2953–2870, 2042, 1464–1332, 1229–955,836–684, 559; 1H NMR (400 MHz, CDCl3) δ(ppm) = 0.30 (s, 6HSiCH3), 0.60–0.64 (m, 14H CH2), 0.95–0.98 (m, 42H CH3),1.83–1.93 (m, 7H CH), 2.38 (s, 1H, HCCSi); 13C NMR(100 MHz, CDCl3) δ(ppm) = 1.55 (SiMe3), 22.37, 22.79, 25.71,88.45 (CC), 92.11 (CC); 29Si NMR (99 MHz, CDCl3) δ(ppm) =−16.05 (HCCSi), −66.89, −67.00, −67.86, −109.83. HRMS (FD):calcd for C32H70O13Si9Na: 937.2638; found: 937.2626. Anal.calcd for C32H70O13Si9 (%): C 41.97; H 7.71; found: C 41.87;H 7.73.

1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(ethyl)pentacyclo-[9.5.1.13,9.15,15.17,13]octasiloxane (6A-2). Yield: 2.19 g (91%);white solid; Rf = 0.73 (n-hexane–Et2O, 11 : 1; I2); IR (ATR)(cm−1): 3288, 2964–2882, 2040, 1461–1414, 1253–1011,836–692, 526; 1H NMR (400 MHz, CDCl3) δ(ppm) = 0.32 (s, 6HSiCH3), 0.61 (qu, J = 8 Hz, 14H, CH2), 0.99 (tr, J = 8 Hz, 42HCH3), 2.39 (s, 1H, HCCSi); 13C NMR (100.6 MHz, CDCl3)δ(ppm) = 1.45 (SiMe3), 3.97, 6.42, 88.26 (CC), 92.22 (CC); 29SiNMR (99 MHz, CDCl3) δ(ppm) = −15.58 (HCCSi), −65.01,−65.69, −65.73, −108.86. HRMS (FD): calcd forC18H42O13Si9Na: 741.0446; found: 741.0427. Anal. calcd forC18H42O13Si9 (%): 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-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, 1226,1–92, 908, 844–683, 566; 1H NMR (400 MHz, CDCl3, 300 K)δ(ppm) = 0.3 (s, 6H SiCH3), 0.54–0.59, 0.74–0.78, 0.90, 1.00,1.10–1.14, 1.30–1.34, 1.85 (m, i-Oc), 2.37 (s, 1H, HCCSi); 13CNMR (100 MHz, CDCl3) δ(ppm) = 1.61 (SiMe3), 23.38, 23.44,24.96, 25.66, 30.13, 31.15, 38.13, 53.93, 88.42 (CC), 92.16 (CC);29Si NMR (99 MHz, CDCl3) δ(ppm) = −16.21 (HCCSi),−66.99, −67.19, −68.19, −110.00. HRMS (FD): calcd forC54H114O13Si9Na: 1245.6080; found: 1245.6068. Anal. calcd forC54H114O13Si9 (%): C 52.98; H 9.39; found: C 52.89; H 9.41.

1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(cyclopentyl)-pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (6A-4). Yield:3.02 g (90%); white solid; Rf = 0.80 (n-hexane–Et2O, 11 : 1; I2);IR (ATR) (cm−1): 3293, 2948, 2865, 2041, 1450, 1253–949,834–676, 513; 1H NMR (500 MHz, CDCl3) δ(ppm) = 0.31 (s, 6HSiCH3), 0.96–1.03, 1.46–1.60, 1.71–1.76 (m, c-C5H9), 2.38 (s,1H, HCCSi); 13C NMR (125 MHz, CDCl3) δ(ppm) = 1.56(SiMe3), 22.10, 22.17, 26.98, 27.28, 29.70, 88.47 (CC), 92.08(CC); 29Si NMR (99 MHz, CDCl3) δ(ppm) = −15.90 (HCCSi),−65.87, −65.45, −65.87, −108.54. HRMS (FD): calcd forC39H70O13Si9Na: 1021.2638; found: 1021.2618. Anal. calcd forC39H70O13Si9 (%): 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 theliterature.7a

1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(cyclohexyl)-pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (6A-5). Yield:3.34 g (91%); white solid; Rf = 0.81 (n-hexane–Et2O, 11 : 1; I2);IR (ATR) (cm−1): 3292, 2920, 2848, 2040, 1446, 1269–1011,893–674, 507; 1H NMR (500 MHz, CDCl3) δ(ppm) = 0.33 (s, 6HSiCH3), 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(CC); 29Si NMR (99 MHz, CDCl3) δ(ppm) = −16.14 (HCCSi),−67.83, −67.97, −68.66, −108.55. HRMS (FD): calcd forC46H84O13Si9Na: 1119.3733; found: 1119.3734. Anal. calcd forC46H84O13Si9 (%): C, 50.32; H, 7.71; found: C 50.16; H 7.73.

1-Ethynyldimethylsiloxy-3,5,7,9,11,13,15-hepta(phenyl)-penta-cyclo[9.5.1.13,9.15,15.17,13]octasiloxane (6A-6). Yield: 2.97 g(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, 6HSiCH3), 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); 29SiNMR (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.

Mixture of cis- and trans-di[9,19-ethynyldimethylsiloxy-methyl]-1,3,5,7,11,13,15,17-octa(phenyl)pentacyclo-[11.7.1.13,11.15,17.17,15]decasiloxane (6B-7). Yield: 3.71 g (82%); white solid;Rf = 0.68 (n-hexane–CH2Cl2, 6 : 4; UV); IR (ATR) (cm−1): 3277,3074–2965.45, 2038, 1594, 1430, 1258, 1094–998, 835–694, 577;1H NMR (400 MHz, CDCl3) δ(ppm) = 0.24, 0.37 (s, 18H SiCH3),2.18 (s, 2H, HCCSi), 7.21–7.66 (Ph); 13C NMR (100 MHz,CDCl3) δ(ppm) = −2.97; 1.05, 1.79 (SiMe3), 88.59 (CC), 92.44(CC), 127.50–127.75, 130.41–131.77, 134.06–134.19 (Ph);29Si NMR (99 MHz, CDCl3) δ(ppm) = −17.19 (HCCSi), −63.84,−79.16, −79.25, −79.44, −79.64. HRMS (FD): calcd forC58H60O16Si12Na: 1371.1010; found: 1371.1007. Anal. calcd forC58H60O16Si12 (%): C 51.60; H 4.48; found: C 51.45; H 4.49.

Conclusions

In summary, we have devised new versatile one-pot protocolsfor high yield preparation of new ethynylsiloxysilsesquioxanesbearing one or two ethynyl groups in a POSS/DDSQ molecule.Because of the potential importance of this new ethynyl func-tionalized DDSQ-based silsesquioxane, especially in view of itssignificant possible future application in the synthesis of awide range of materials (also oligo- and polymeric), this com-pound could be particularly interesting. Two alternative waysfor the synthesis of the title compounds were proposed. Thefirst is a one-pot procedure involving five consecutive reactionswithout intermediate isolation, but with very good overallefficiency. According to the other protocol, the reaction is rea-lized in three steps with very high isolating yields, but the

main reagent, i.e. ClMe2SiCCH, is not commercially available.Both methods lead to mono- and diethynylsiloxy silsesqui-oxanes with good yields and are comparably effective. The pro-ducts were isolated and characterized by spectroscopicmethods (1H, 13C and 29Si NMR, FT-IR, HRMS). These alterna-tive procedures for the synthesis of the title compounds willenhance the availability of a new variety of silsesquioxanes.

Acknowledgements

The authors gratefully acknowledge support from the Ministryof Science and Higher Education (Poland), grant no.UMO-2012/05/D/ST5/03348 and from the European RegionalDevelopment Fund, Operational Programme InnovativeEconomy, 2007-2013, project no. UDA-POIG.01.03.01-30-173/09-02.

Notes and references

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