FR2728572A1 - New tri:alkoxy-silyl-ethynyl derivs. - Google Patents

Abstract

Tri:alkoxysilyl-ethynyl deriv. of formula (I) is new. (RO)3Si-C=C-R1-C=C-Si(OR)3 (I) (RO)3Si-CC- (i) (where R = alkyl and R1 - (cyclo)alkylene, alkenylene, alkynylene or bivalent cyclic aromatic ring or heteroaromatic ring (contg. O, N and/or S), which may be substd., by one or more tri:alkoxysilyl-ethynyl gps. of formula (i)). Also claimed are (a) prepn. of (I), (b) polymer obtd. by hydrolysis and polycondensation of (I) and its prepn., (c) copolymer obtd. by co-hydrolysis and polycondensation of (I) in the presence of Si(OR9)4 (R9 = 1-4C alkyl) and its prepn., (d) prepn. of silica, (e) cpd. of formula (R3)3Si-C=C-R4-C=C-Si(R3)3 (II), (R3)3Si-C=C- (ii) R4 = 1-8C alkylene, 2-8C alkenylene, 2-8C alkynylene, 4-8C cycloalkylene or bivalent cyclic 6-24C aromatic ring or 3-6 membered heteroaromatic ring (contg. O, N and/or S) which may be substd. by one or more gps. of formula (ii), and R3 = 1-4C alkyl, provided that when R4 = phenylene, R3 = 2-4C alkyl, (where (f) cpd. of formula (II) where R3 = 2-4C alkyl, and (g) cpd. of formula (I) where R = 1-4C alkyl opt. substd./ by one or more gps. of formula (ii)).

Description

The present invention relates to novel precursors of silica gels as well as to a process for preparing silicas of controlled porosity from these precursors.

Silica is commonly used in the field of chemistry, in particular as a desiccant, as a catalyst support, or as a catalyst itself, or even as an adsorbent in chromatography.

The sol-gel process allows the preparation of amorphous silicas under very mild conditions by simple hydrolysis of molecular silicon precursors. Thus, the hydrolysis of tetraalkoxysilanes leads to silicas according to equation (i) below:

The physical characteristics of the final material vary depending on many parameters such as the nature of the precursor or the experimental conditions.

For the applications mentioned above, the desired properties relate to the porosity of the material and are in particular a high specific surface area or a particular pore size distribution.

As hydrolyzable precursors, organosilicon compounds offer a very wide field of investigation.

Thus, the hydrolysis of trialkoxysilanes is well known to lead to silsesquioxane-type materials, as shown in equation (ii).

These starting compounds are of considerable interest insofar as the Si-C bond between the R group and the silicon atom is preserved under the conditions of the sol-gel polymerization.

As many silicas with different properties are thus prepared as there are R groups envisaged.

However, the presence of organic residues in the material can constitute a drawback in the case of applications where the material must be inert with respect to a given reactive environment.

The object of the present invention is to propose novel hydrolyzable molecular precursors making it possible to produce in fine in a controlled manner a network of purely inorganic silica having determined physical characteristics.

A subject of the invention is thus polyfunctional compounds containing trialkoxysilylethynyl functions of formula (1) (RO) 3Si-C = -C-R1-C- = C-Si (OR) 3 in which: - R is an alkyl group - R 'is chosen from alkylene, alkenylene, alkynylene, cycloalkylene and divalent radicals derived from aromatic cyclic or heterocyclic aromatic compounds and in which at least one heteroatom chosen from O, N and S is present; each of these radicals possibly being sbstitué one or more times with a trialkoxysilylethynyl group of formula (1 ') (RO) 3Si-C - C- identical to the functional groups of formula (1).

Preferred compounds of formula (1) are those in which: - R is a C, -C4 alkyl group - R 'is chosen from the radicals of C1-C8 alkylene, C2-C8 alkenylene, C4-C8 alkynylene, C3-C8 cycloalkylene and the divalent radicals derived from C6-C24 aromatic cyclic or aromatic heterocidic compounds having 3 to 6 members and in which is present at least one heteroatom chosen from O, N and S; each of these radicals possibly being sbstitué one or more times with a trialkoxysilylethynyl group of formula (1 ') (RO) 3Si-C-C- identical to the functional groups of formula (1).

The R groups can in particular be methyl, ethyl, propyl or butyl groups, preferably the methyl group.

As groups R 1 unsubstituted by groups of formula (1 ′), mention may be made of divalent radicals of C 1 -C 8 alkylene type, in particular ethylene, butylene, octylene groups, and preferably the n-butylene group; divalent radicals of C2-C8 alkenylene type: divalent radicals of C4-C8 alkynylene type; divalent radicals of C3-C8 cycloalkylene type, in particular cydohexylene; divalent radicals derived from C6-C aromatic cyclic compounds, in particular ortho-, meta- and para-phenylene, biphenylene, triphenylene benzene, tetraphenylene methane groups; and divalent radicals derived from aromatic heterocyclic compounds having from 3 to 6 members and in which is present at least one heteroatom chosen from O, N and S, in particular the thiophenylene group.

The R 'groups may themselves bear one or more substituent (s) of formula (1') (RO) 3Si-C # C- identical to the functional groups of formula (1), so that the compounds of formula (1) corresponding have at least three trialkoxysilylethynyl functions.

c'est-à-dire un composé de formule (1) dans laquelle le groupe Rr est un groupe 5-trialcoxysilyléthynyl-1,3-phénylène de formule:

For example, the compound of formula (1) can be a 1, 3.5 tris (trialkoxysilylethynyl) benzene of formula:

that is to say a compound of formula (1) in which the group Rr is a 5-trialkoxysilylethynyl-1,3-phenylene group of formula:

c'est-à-dire un composé de formule (1) dans laquelle le groupe Rr est un groupe 2,5-bis(trialcoxysilyléthynyl)-1 ,4-phénylène de formule::

Tetrafunctional compounds of formula (1) have also been prepared, such as 1,2,4,5-tetrakis (trialkoxysilylethynyl) benzene of formula:

that is to say a compound of formula (1) in which the group Rr is a 2,5-bis (trialkoxysilylethynyl) -1, 4-phenylene group of formula:

The compounds of formula (1) in which the group R 'is a divalent radical derived from a C6-C2 * aromatic cyclic or heterocyclic aromatic compound having from 3 to 6 members and in which is present at least one heteroatom chosen from O , N and S, this radical being optionally substituted one or more times by a group of formula (1 '), can be obtained by a process comprising the following stages: (a) a compound of formula (2) X- is reacted. R2-X in which:
- X is a leaving group, in particular a halo-
uncomfortable.

- R2 is a divalent radical derived from a cyclic compound
aromatic C6-C24 or heterocyclic aromatic having
from 3 to 6 links and in which is present at least one
heteroatom chosen from O, N and S, this radical being
optionally substituted one or more times by a
leaving group X (2 ') identical to the previous one, with a trialkylsilylacetylene of formula (3) R33 Si-C = -CH in which R3 is a C1-C4 alkyl group, in excess relative to the total number of groups X (2 ') present in (2) to form a compound of formula (4)::
R33 Si-C # C-R4-C # C-SiR33 in which R4 is identical to the R2 group defined above, the possible groups (2 ') being transformed into groups (4') of formula -C # C-SiR33 '( b) the compound of formula (4) is reacted with a strong base so as to form a polyanionic species of formula (5) :: Y #, # C # C-R5-C # C #, Y # in which - ye represents a counterion provided by the strong base, in particular the cation Li *, - R5 is a group identical to the group R4, the possible groups (4) being transformed into groups (5 ') of formula C = Ce,; Y
(c) the compound of formula (5) is reacted with a compound of formula
(6) ZSi (OR) 3 in which Z is a halogen atom or an alkoxy group
(OR), to lead to a compound of formula (1) (RO) 3Si-C = -C-R1 -CC-Si (OR) 3 in which R1 is identical to the group R5, the possible groups (5 ′) being transformed into groups of formula (1 ') -CC-Si (OR) 3.

In step (a), it is a question of substituting the group X of the compound of formula (2) by a trialkylsilylethynyl group. For this purpose, it is possible to use, as group X of formula (2 '), any group known as a leaving group, in particular a halogen atom (Cl, Br, I in particular).

The operating conditions used during this step can be any that allow the substitution reaction.

Advantageously, the procedure is carried out by placing the compounds of formulas (2) and (3) in the presence of a palladium-based catalyst at oxidation degree 0 or + II. For example, a mixture of dichloro-bis- (triphenylphosphine) palladium (áP) 2PdCl2 and copper iodide can be used.
Ass in triethylamine.

A compound of formula (4) is thus isolated, which is reacted with a strong base in step (b). Any strong base or any base known for its ability to cut a bond between a silicon atom and an acetylenic carbon atom can be used. Advantageously, lithiated bases such as alkyllithium, in particular methyllithium, preferably mixed with lithium bromide are used.

The formation of the polyanionic species (5) takes place in an inert solvent such as anhydrous ether, dioxane, hexane, or preferably anhydrous tetrahydrofuran (THF).

Step (b) can be carried out at about 20 C.

The use of methyllithium is very advantageous in the case where R3 is a methyl group, insofar as the reaction of MOU on a group of formula (4 ') -CC-SiMe3 leads to the formation of an anion of formula ( 5 ') -C # C #, Lii by releasing inert and voiatil tetramethylsilicon (TMS) which can be removed from the reaction mixture by simple distillation.

The amount of strong base used in step (b) is preferably such that a polyanionic species of formula (5) is formed in which the optional substituents of formula (4 ') are transformed into anionic groups of formula (5). ') -C # C #, # Y, being the counterion provided by the strong base. Thus, an amount of strong base at least stoichiometric is preferably used relative to the total number of -C-C-SiR33 groups present in the compound of formula (4).

A silylating agent of formula (6) ZSi (OR) 3, preferably ClSi (OR) 3, is then added to the reaction mixture of step (b) containing the polyanionic compound of formula (5), which is not not isolated due to its instability in air.

During this step (c), the halogen atom is displaced by attacking acetylides of formula (5 '), so that a compound of formula (1) is formed.

The silylating agent (6) is preferably used in stoichiometric excess relative to the total number of anionic groups -C # C #, # Y present in the compound of formula (5) to ensure complete silylation.

Step (c) is carried out at low temperature, advantageously at a temperature below 0 ° C., preferably at a temperature below -20 ° C. A good yield is thus achieved while avoiding side reactions.

The compounds of formula (1) in which the group R1 is a C1-C8 alkylene group can be obtained by a process comprising the following steps:
(e) reacting a compound of formula (7) HC # C-R7-C # CH in which R7 is a C1-C8 alkylene group, optionally substituted one or more times by a group of formula (7 ') - CECH, with a strong base to form a polyaniF nic species of formula (8) Y #, # C # C-R8-C # C #, iy, in which :: - R8 is identical to the group R7, the possible groups (7 ') being transformed into groups of formula (8') -C # C #, #Y, - Y # represents a counterion provided by the strong base, in particular the cation Li #,
(f) the compound of formula (8) is reacted with a compound of formula (6) ZSi (OR) 3 in which Z is a halogen atom or an alkoxy group (OR), to result in a compound
of formula (1) (RO) 3Si-C = -C-R1-C- = C-Si (OR) 3 in which R1 is identical to the group
R8, the possible groups (8 ') being transformed into group (1') -C # C-Si (OR) 3.

The operating conditions of step (e), respectively of step (f), are similar to those of step (b), respectively of step (c).

When the compound of formula (4) obtained at the end of step (a) has more than two -C # C-SiR33 groups, or when the compound of formula (7) used in step (e) has more than two -C-CH groups, it is possible to prepare a compound of formula (10) (RO) 3Si-C ~ C-Rt -C ~ C-Si (OR) 3 in which R10 is chosen from alkylene radicals C, -C8, C2-C8 alkenylene, C4-C8 alkynylene, C3-C8 cycloalkylene, divalent radicals derived from C6-C2 aromatic cyclic compounds, or aromatic heterocyclic compounds having 3 to 6 members and in which is present at least one heteroatom chosen from O, N and S, each of these radicals being substituted one or more times by a group of formula (10) -CCG in which G represents a hydrogen atom or a group -SiR33 where R3 is a C1-C4 alkyl group, and optionally one or more times with a group of formula (1 ') -CC-Si (OR) 3 identical to the functional groups of the compound of formula (10).

To do this, we use in step (b), respectively in step (e), an amount of strong base less than the stoichiometric amount calculated relative to the total number of -CC-SiR33 groups present in the compound of formula (4), or the total number of -C-CH groups present in the compound of formula (7)
A polyanionic intermediate compound is thus prepared in which at least one group of formula (4 '), respectively (7'), is kept intact while the other (s) are transformed into anions (5 '), respectively (8').

By silylation in step (c), respectively (f), using the reagent of formula (6), a compound of formula (10) is obtained which has at least two functions -C = -C-Si (OR) 3 and at least one function -CC-SiR33, respectively -C-CH.

le 1 ,3,5-tribromobenzène, on peut appliquer le mode opératoire A d- dessous qui conduit à un composé de formule (1), alors que le mode opératoire (B) ci-dessous conduit à un composé de formule (10). For example, from the following compound of formula (2)

1, 3,5-tribromobenzene, one can apply the procedure A below which leads to a compound of formula (1), while the procedure (B) below leads to a compound of formula (10) .

Operating mode A:

Operating mode B:

Compounds of formula (10) can be converted into corresponding compounds of formula (1) by applying steps (b) and (c), or (e) and (f), with appropriate amounts of reagents.

A subject of the present invention is also the polyfunctional compounds containing trialkoxysilylethynyl functions, having at least one trialkylsilylethynyl function corresponding to formulas (4) and (10).

A subject of the invention is therefore a compound of formula (4) R33Si-C # C-R4-C # C-SiR33 in which R4 is chosen from C, -C8 alkylene, C2-C8 alkenylene and C-C8 alkynylene radicals. C4-C8, C3-C8 cycloalkylene and divalent radicals derived from C6-C24 aromatic cyclic or heterocyclic aromatic compounds having 3 to 6 members and in which is present at least one heteroatom chosen from O, N and S; each of these radicals possibly being optionally substituted one or more times by a trialkylsilylethynyl group of formula (4 ') -C-C-SiR33, formulas in which R3 is a C1-C4 alkyl group; with the proviso that if R4 is a phenylene radical, then R3 is a C2-C4 allyl group.

In particular, the subject of the invention is a compound of formula (4) in which R3 is a C2-C4 alkyl group.

A further subject of the invention is a compound of formula (10) (RO) 3Si-C ~ CR '-CC-Si (OR) 3 in which R is a C1-C4 alkyl group and R10 is chosen from the radicals C1-C6 alkylene, C2-C8 alkylene, C4-C8 alkynylene, C3-C81 cycloalkylene and divalent radicals derived from C6C aromatic cyclic compounds, or aromatic heterocyclic compounds having 3 to 6 members and in which is present at least one heteroatom chosen from O, N and S, each of these radicals being substituted one or more times by a group of formula (4 ') -CC-SiR33 in which R3 is a Ct-C4 alkyl group and optionally a or several times with a group of formula (1 ') -CC-Si (OR) 3 identical to the functional groups of the compound of formula (10), in particular a compound of formula: C6H3 (CC-SiR33) (CC-Si (OR ) 3) 2 in which R and R3 are the same or different C1 -C4 alkyl groups.

The compounds of formulas (1) and (10) according to the invention can be used as precursors of hybrid silica gels in which silicon atoms are linked together by organic bridges.

A subject of the invention is therefore also a polymer or gel obtained by hydrolysis and polycondensation of a polyfunctional compound of formula (1) and 'or (10), as well as a copolymer obtained by cohydrolysis and polycondensation of a polyfunctional compound of formula (1) and'or (10) in the presence of a tetraalkoxysilane of formula (9) Si (OR9) 4 in which R9 is a C1-C4 allyl group.

For the sake of clarity, the polymerization conditions are described below with regard to a compound of formula (1), but also apply to a compound of formula (10) or optionally to a mixture of compounds of formulas (1) and (10).

To carry out the hydrolysis and polycondensation Crun compound of formula (1) on itself:
(i) water is added to a solution of (1) in an inert solvent in an amount at least stoichiometric relative to the total number of hydrolyzable Si-OR bonds present in (1),
(ii) the mixture is left until gelling, and
(iii) the gel obtained is dried.

A copolymer gel according to the invention can be prepared from a compound of formula (1) and a very variable amount of silicate (9).

To perform cohydrolysis and polycondensation:
(i) is added to a solution of (1) and (9) in an inert solvent, water in an amount at least stoichiometric relative to the total number of hydrolyzable Si-OR and Si-OR9 bonds present in (1) and (9),
(ii) the mixture is left until complete gelation, and
(iii) the gel obtained is dried.

The inert solvent can in particular be anhydrous ThIF, dioxane or an alcohol (methanol in particular). Gelation was observed after a time which may vary between several seconds and several months, preferably between 1 minute and several pure.

Advantageously, the gel is left for an aging period during which the phenomenon of syneresis is observed.

The gel obtained is preferably washed one or more times with a polar solvent and the isolated solid is finally dried.

The use of a compound of formula (1) as a precursor of silica gel is of very particular interest which resides in the fact that the organic part of the compound of formula (1) is very stable under mild conditions. hydrolysis while the SiZ bond between a silicon atom and an adjacent acetylenic carbon atom is capable of being cleaved under appropriate conditions. It is thus possible to remove the organic fragments from the gel obtained by hydrolysis or cohydrolysis in order to separate a purely inorganic silica gel.

The invention therefore provides a process for the synthesis of silica in two stages which consists in preparing a hybrid gel by hydrolysis or cohydrolysis of a compound of formula (1) eVou (10) and then in removing the organic part of this mixed gel.

The elimination of the organic part of the hybrid gel can be carried out by a hydrolysis reaction in the presence of a catalyst based on fluoride ions, in particular ammonium fluoride.

Advantageously, the hydrolysis is carried out in a hydromethanolic medium under reflux.

The hydrolysis is carried out in a time which can range from a few hours to several days.

During hydrolysis, the breaking of bonds
Si-acetylenic leads to the reorganization of the gel into a network of silicates alone, while a compound of formula (11) HCC-Rtt-C ~ CH where R11 is identical to R1 except that the possible groups (1 ') are released -C = -Si (OR) 3 are converted into groups (11 ') of formula -C-CH.

The compound of formula (11) can be easily removed from the desired silica by filtration and washing of the solid obtained at the end of the hydrolysis. For washing, solvents such as ethers or acetone, in particular THF or ether, are preferably used.

The organic part of the hybrid gel can also be removed by pyrolysis in the presence of oxygen at a temperature of 400 to 700 ° C. In this case, the organic part is calcined.

The pyrolysis operation can last between 2 and 8 hours. It is verified that the elimination of the organic fragments is total when the loss of mass of the material measured at two consecutive instants becomes zero.

Optionally, a silica obtained by hydrolysis in the presence of fluoride ions can be treated by pyrolysis.

The silicas prepared by hydrolysis or by pyrolysis have high specific surfaces.

The silicas prepared by hydrolysis also have quite advantageous porosity characteristics. Indeed, these materials exhibit a very narrow pore size distribution around a particular value which depends on the precursor used and on the composition of the hybrid gel prepared in an intermediate manner. The process for preparing silica according to the invention in two stages with hydrolysis in the second stage thus makes it possible to obtain easily and in a controlled manner silicas of defined porosity.

It is surprising to note that the size of the pores of these silicas is not necessarily of the same order of magnitude as the size of the organic fragment included in the hybrid gel.

On the other hand, the size of the pores of the silica can be controlled by means of the composition of the hybrid gel or more precisely by controlling the dilution of the organic fragment in this hybrid gel.

The silicas prepared by pyrolysis also have a particular porosity, although very different. In fact, these silicas are of the microporous type with a wider distribution of pore diameters.

The differences in the properties of the silicas of the invention will appear clearly in the light of the following examples which illustrate the invention.

Example 1
Preparation of 1, 3,5-tris (trimethoxysilylethynyl) - benzene
la) Preparation of 1,3,5-tris (trimethylsilylethynyl) benzene: C21HSi3.

40 g (127.1 mmol) of 1,3,5 tribromobenzene, 5.3 g (7 , 6 mmol) of dichloro-bis (triphenylphosphine) - palladium (+ 3P) 2PdCl2 and 0.54 g (4.9 mmol) of cuprous iodide Cul, then 48.6 g (496 mmol) of trimethylsilylacetylene.

A precipitate forms immediately at room temperature. The mixture is then heated at 40 ° C. for 12 h with vigorous stirring and the yellow-brown solution turns greenish then brown-red. The reaction mixture is filtered and the solid residue washed with pentane. The filtrate is evaporated, the viscous product obtained is taken up in a minimum of hexane and purified on a chromatographic column filled with 500 g of silica and eluted with hexane.

After evaporation of the solvent, the product obtained is recrystallized from pentane to give 40.2 g of pale yellow crystals.

The reaction yield is 86%.

The characteristics of the product (1 a) obtained are as follows: - Melting point: 61 -63 C - Elemental analysis:
theoretical C 68.78%; H 8.24%; Si 22.98%
exp. C 68.54%; H 8.24%.

- Spectrometric characteristics:
@ Fourier transform infrared spectroscopy (IRTF) (in
CCL4, cm-1): 1249, 1580, 2166, 2896, 2959.

. 1 H NMR (CC14.6, ppm): 0.02 (27H, s), 7.27 (3H, s);
@ 29 Si NMR (CDCl3, #, ppm), -17.34;
. 13C NMR (CDCl3.6, ppm): 0.22 (q), 95.97 (s), 103.51 (s), 124.01 (s), 135.30 (d).

@ Mass spectrometry (MS) m / e: 366 (33, M +), 351 (100, M + -1Me), 321 (4, M + -3Me), 168 (26, M + -2 (-CC-SiMe3), 153 (3, M + -2 (-CG SiMe3) -1Me), 73 (16, SiMe3 +).

1 b0 Preparation of 1,3,5-trilithioethynylbenzene
In a flask fitted with a condenser and an isobaric pouring funnel, 26.9 g (73.4 mmol) of compound (la) are dissolved in 400 ml of anhydrous THF (distilled beforehand over calcium hydride, then over sodium thread).

insoluble de couleur gris bleuté.220 ml of a solution of methyllithium and lithium bromide in ether of concentration [MeLi] = 1.3 M. are introduced into the funnel. The reaction mixture is cooled to -40 C. The solution of MeLilLiBr is added drop by drop, under a stream of nitrogen and rapid stirring. After the addition, the reaction mixture is heated at 55- C for 24 h until the trianion is obtained.

insoluble bluish gray color.

1c) Preparation of 1,3,5-tris (trimethoxysiMéttiynyl) benzene:
C21H30O9Si3
The suspension of the trianion (1 b) in THF from the previous step is cooled to -50 C and added dropwise with stirring to a solution of 44.8 g (286 mmol, excess) of ClSi (OMe) 3 in 100 ml of
Anhydrous THF at -70 C.

After the addition, the reaction mixture is allowed to come to room temperature. The THF and the TMS formed during the reaction are evaporated off in vacuo. The evaporation residue is extracted with pentane, the pentane is filtered and then evaporated to isolate 36.0 g of an orange-brown viscous liquid corresponding to the expected product obtained with a silylation yield of 96%.

The characteristics of the product (1 c) obtained are as follows: - Elemental analysis
theoretical C 49.39%; H 5.92%
exp. C 49.25%; H 5.94%.

- Spectroscopic characteristics:
IR (CCl4, cm-1): 1112, 1580, 2174, 2845, 2944.

1H NMR (CCI4.6): 3.41 (27H, s), 7.49 (3H, s);
RMN29Si (CDCl3, #): -69.94; 13C NMR (CDCl3.6): 51.29 (q), 86.25 (s), 102.16 (s), 123.08 (s), 136.65 (d); - Mass spectrometry m / e: 510 (5, M +), 390 (4, M ± Si (OMe) 3), 270 (8, M + -2Si (OMe), 121 (86, Si (OMe) 3+) , 90 (27, Si (OMe) 2+).

ld) Preparation of 1-trimethylsilylethynyl-3,5-dilithioethy- nylbenzene
3.0 g (8.2 mmol) of compound (la) are dissolved in 20 ml of anhydrous THF (distilled beforehand over calcium hydride, then over son of sodium). Is introduced into the funnel 17 ml of a solution of methyllithium and lithium bromide in ether of concentration [MeL1 = 1.5 M. The solution is added dropwise, under a stream of nitrogen and rapid stirring. The reaction mixture turns from pale yellow to brown. After the addition of MeLi, the reaction mixture is kept for 2 h at -20 C, then 5 h at -10-C and 0 ° C until a solid color is obtained. of wine indicative of the formation of the dianion:

le) Preparation of 1-trimethylsilylethynyl-3,5-bis (trimethoxysilylethynyl) benzene
The solution of dianion (1d) in THF from the previous step is cooled to -30 C and added dropwise with stirring to a solution of 3.3 g (21.3 mmol) of ClSi (OMe) 3 in 20 ml of anhydrous THF at e C.

the very dark blue mixture is warmed to room temperature. The solution turns green and then a strong yellow. THF and
TMS formed during the reaction are evaporated in vacuo. The evaporation residue is extracted with pentane, the pentane is filtered and then evaporated to isolate a yellow ocher viscous liquid. The spectroscopic characteristics in 1 H NMR are as follows:
TH NMR (CCI4.6) 7.5 (3H, m), 3.38 (18H, s), 0.03 (9H, s).

Example 2
Preparation of 1,8-bis (trimethoxysilyl) - 1,7-octadiync
2a) Preparation of 1,8-dilithioocta-l, ri-diyne
In a flask fitted with a condenser, an isobaric pouring funnel and a gas outlet pipe, 8.2 g (77.2 mmol) of 1.7 are dissolved with stirring and under a stream of nitrogen. -octadlyne in 350 ml of anhydrous THF (distilled beforehand over calcium hydride then over sodium threads). 130 ml of a solution of methyllithium and lithium bromide in ether, of concentration [MeLI1 = 1.5 M.
MeLi / LiBr is added dropwise, during the reaction methane is formed which escapes through the gas outlet. After the addition, the reaction mixture is heated at 55 ° C for 3 h until the dianion (# C # C- (C4H2) -C # C #, 2 Li #) is obtained in the form of a yellow-orange precipitate.

2b) Preparation of 1, 8-bis (trimethoxvsiM) -1, 7-octadiyne
The suspension of dianion (2a) in THF from the previous step is cooled to -60 C and added dropwise to a solution of 30 g (191 mmol, excess) of ClSi (OMe) 3 in 100 ml of THF anhydrous at -70- C.

After the addition, the mixture is allowed to return to room temperature with stirring for 12 h, then it is subjected to vacuum distillation. 13.35 g of a pale yellow liquid are thus isolated, which distils at 135 ° C. under a pressure of 5 Pa, the overall yield of the reaction being 66%.

The characteristics of the product (2b) are as follows: - Elemental analysis:
theoretical C 48.53%; H 7.56%
exp. C 47.09%; H 7.16%.

- Spectroscopic characteristics:
.IRTF (CCI4, cm-1): 1086, 1428, 1460, 2185, 2843, 2943.

.RMN 'H (CC14.6): 1.47 (4H, m), 2.09 (4H, m), 3.29 (18H, s);
.RMN 29Si (CDCl3,6): -69.26;
.RMN'3C (CDCl3.6): 19.36 (t), 27.39 (t), 51.02 (q), 75.32 (s), 107.59 (s); - Mass spectrometry m / e: 345 (1, M +), 315 (28, M + -2Me), 299 (13, M + -3Me), 284 (63, M + -4Me), 269 (30, M + -5Me) , 254 (10, M + 6Me), 227 (26, M + -Si (OMe) 3), 194 (84, M + -Si (OMe) 3-OMe), 121 (120, + Si (OMe) 3), 105 (24, M + -2Si (OMe).

Example 3
Preparation of a G1 gel by hydrolysis and polycondensation of 1,3,5-tris (trimethoxysilylethynyl) benzene
17.39 g (34 mmol) of 1,3,5-tris (trimethoxysilylethynyl) benzene (compound 1c) are dissolved in 34 ml of anhydrous THF previously distilled over calcium hydride, then over sodium threads). 2.76 g (153.3 mrno (> distilled water are then added. The reaction is exothermic. The mixture gels in 2 minutes. The translucent monolith obtained is yellow-orange. Aging for one week is maintained during which the syneresis phenomenon is observed The gel is then ground, the powder obtained is washed with ether, filtered and dried under vacuum for 24 h at room temperature.

The elementary analysis of the solid obtained is as follows:
C 43.52%; H 3.36%; O 24.82%; Si 25.08%.

de formule brute C12H3O4.5Si3.The gross formula of gel G1 is therefore C12,17H11,20O5,21Si3 ′ which corresponds well to a polymer of unit:

molecular formula C12H3O4.5Si3.

The G1 gel obtained is characterized by IRTF and by solid-state NMR. The spectroscopic characteristics of gel G1 are as follows:
CP MAS 29Si NMR (6, ppm): -79.1; -87.4; -98.

13C CP MAS NMR (6, ppm): 50.30; 89.88; 101.71; 123.03; 135.46.

IRTF (KBr pellet, cm-1): 1064.4; 1582.5; 2174.2; 2975.6; 3420.

R=H,Mc
La surface spécifique du gel G1 mesurée par la méthode BET par adsorption/désorption d'azote est de 57 m21g, ce qui est bien en deçà des valeurs observées pour des gels de silice usuels, ne comportant pas d'inclusion organique.The organic structure is maintained in the solid, and no cleavage of the Si-C bond is observable by NMR. Only the presence of a low intensity infrared absorption band at 3292 cm-1 reveals traces of cutting of the Si-C bond. The 29Si NMR shows a maporitary signal at -87.5 ppm attributable to a T2 type substructure: # C-Si (OH (OSi) 2) or # C-Si (OMe) (OSi) 2. Hydrolysis under mild conditions therefore makes it possible to obtain a gel whose average structure is not as follows:

R = H, Mc
The specific surface of the gel G1 measured by the BET method by adsorption / desorption of nitrogen is 57 m21 g, which is well below the values observed for usual silica gels, not comprising any organic inclusion.

Example 4
Preparation of a gel 62 by cohydrolysis and polycondensation of 1,3,5-tris (trimethoxysilylethynyl) benzene and of tetmm thylorthosilicate
6.67 g (13.06 mmol) of 1, 3,5-tris (trimethoxysilylethynyl) - benzene (compound 1c) are mixed with 17.86 g (117.5 mmol) of tetramethylorthosilicate (9 eq.), The whole in 43.5 ml of anhydrous THF. 5.29 g (293.8 mmol) of distilled water are then added. The reaction is exothermic, the mixture gels in 24 h. The translucent monolith obtained is yellow-orange. Aging of one week is maintained during which the phenomenon of syneresis is observed. The gel is then ground, the powder obtained is washed with ether, filtered and dried under vacuum at room temperature for 24 h.

The elemental analysis and the spectroscopic characteristics of the solid G2 obtained are as follows:
C 22.15%; H 3.10%; 037.91%; Si 31.00%.

CP MAS 29Si NMR (d, ppm): -79; -85; -90.7; -99.5; -110;
13C HPDEC NMR (6, ppm): 51.11; 87.90; 100.99; 122.91; 136.32; IR1F (KBr, cm-1):: 1071.2; 1583.3; 2181.6; 2986.5; 3443.6.

As in the previous case, the Si-C bond is preserved during cohydrolysis and sol-gel polycondensation. Two series of resonances centered at -90 and 100 ppm, corresponding respectively to the CSiO3 and SiO4 substructures, are noted in particular in 29Si NMR.

The specific surface of the gel G2 measured as in Example 4 is 76 m2 / g.

Example 5
Preparation of silica S1 from G1 by pyrolysis.

3.1496 g of gel G1 are placed in an alumina crucible and pyrolyzed up to 600- C with a maximum temperature gradient of 5- C / min with two stages of 30 min at 4500 C and at 550 @ C in air dry. 1.3679 g of white S1 silica powder are recovered.

The formation of the silica S1 from the gel G1 is tive.

The elemental analysis is as follows:
C <0.1%; H 0.88%; O 54.71%; Si 46.81% (SiO2, C0.005H0.52O0.05).

Spectroscopic characteristics:
CP MAS 29Si NMR (6, ppm): -100.14 (broad peak)
CP MAS 13C NMR (6, ppm): no peak
IRTF (KBr, cm-1): 800.4; 1091.9.

The absence of 13C NMR resonance is consistent with the complete elimination of organic fragments. The 29Si NMR spectrum showing a broad resonance centered at -100 ppm is in agreement with SiO4 substructures typical of silica.

The specific surface area and porosity measurements were carried out by the BET method and the results are collated in Table 1. The BET method does not make it possible to measure the microporosity of the silica; on the other hand, the adsorption / desorption isotherms indicate the presence of micropores which cannot however be quantified.

Example 6
Preparation of silica S2 from G2 by pyrolysis.

3.5002 g of G2 are subjected to a pyrolysis operation identical to that of Example 5 to give 2.3129 g of silica S2, quantitatively.

The elementary analysis of solid S2 is as follows:
C 0.2%; H 0.74%; O 54.31%; Si 46.10%
(SiO2, C0.01H0.45O0.07)
Spectroscopic characteristics:
CP MAS 29Si NMR (6, ppm): -100.1 broad peak;
CP MAS 13C NMR (6, ppm): no peak;
IRTF (KBr, cm-1): 793.9, 1082.8.

These results, comparable to those of Example 5, confirm the elimination of the organic fragments from the silica.

The results of the specific surface area and porosity measurements are reported in Table 1.

Example 7
Preparation of silica S3 from G1 by hydrolysis.

25 ml of water, 10 ml of methanol and 9.2 ml of a fluoride solution are introduced into a 100 ml flask fitted with a condenser, containing 3.508 g (11.5 mmol) of gel G1 under nitrogen. ammonium at the concentration [NH4F1 = 0.025 M (0.23 mmol NH4F). The mixture is heated at reflux (75-80-C) with vigorous stirring for 4 days. The residual solid is washed with a mixture of THF and acetone, filtered and dried under vacuum for 24 h at room temperature.

Finally, 1.7176 g of silica S3 obtained quantitatively from G1 are obtained. The washing filtrate is concentrated, and extraction is carried out with ether and with water. The ethereal phase is dried over
MgSO4 and filtered. After evaporation of the solvent from the filtrate, recrystallization of the residue from pentane makes it possible to isolate 1, 3,5-triethynylbenzene with a yield of 85.1%.

Elemental analysis and spectroscopic characteristics of S3 silica are as follows:
C 9.05%; H 1.54%; O 40.16%; Si 39.71%.

The excess carbon and hydrogen are attributable to uncondensed Si-OMe groups. The latter can be removed by pyrolysis at 6000 ° C. for 4 h in dry air.

CP MAS 29Si NMR (#, ppm): -90.9; 100.9; -110.9
IRTF (KBr, cm-1): 808.2; 1093.8; 2964.7; 3454.1.

The results of the specific surface area and porosity measurements are reported in Table 1.

Example 8
Preparation of silica 54 from G2 by hydrolysis.

The hydrolysis is carried out as above on 5.196 g (6.1 mmol) of gel G2 with 30 ml of water, 15 ml of methanol and 5 ml of 0.025M ammonium fluoride solution (0.125 mmol NH4F).

4.0374 g of silica S4 are thus obtained quantitatively from G2 by isolating 1, 3,5-triethynylbenzene with a yield of 84%.

The elemental analysis and the spectroscopic characteristics of silica S4 are as follows:
C 8.35%; H 2.02%; O 50.12%; Si 38.3%
(SiO2, C0.51H1.47O0.29).

The excess carbon and hydrogen are attributable to uncondensed Si-OMe groups. The latter can be removed by pyrolysis at 600 ° C. for 4 h in dry air.

CP MAS 29Si NMR (6, ppm): -90.6; -101.0; -110.8;
IRTF (KBr, cm-1): 800.6; 1070.1; 2986.5; 3450.3.

The results of the specific surface area and porosity measurements are reported in Table 1.

Gel <SEP> Silica
<tb> Product
<tb> G1 <SEP> G2 <SEP> S1 <SEP> S2 <SEP> S3 <SEP> S4 <SEP> S4
<tb> + <SEP> pyrolysis
<tb> Specific <SEP> surface <SEP> (m2 / g) <SEP> 57 <SEP> 76 <SEP> 412 <SEP> 275 <SEP> 492 <SEP> 712 <SEP> 601
<tb> Average <SEP> diameter
<tb> of <SEP> pores <SEP> () <SEP> / <SEP> / <SEP> 15.1 <SEP> 14.9 <SEP> 52.3 <SEP> 26.2 <SEP> 25, 7
<tb> Porous <SEP> volume
<tb> (ml / g) <SEP> / <SEP> / <SEP> 0.17 <SEP> 0.14 <SEP> 0.64 <SEP> 0.47 <SEP> 0.39
<tb> Distribution <SEP> of <SEP> / <SEP> / <SEP> wide, <SEP> important <SEP> narrow <SEP> narrow <SEP> narrow
<tb> pores <SEP> microporosity <SEP> centered <SEP> on <SEP> centered <SEP> on <SEP> centered <SEP> on
<tb><<SEP> 10 <SEP><SEP> 52 <SEP><SEP> 26 <SEP><SEP> 26 <SEP>
<tb>

The silicas obtained exhibit particular characteristics which are very different from those of the precursor hybrid gels.

First, all the silicas prepared have the advantage of a high specific surface.

The elimination of the organic fragment under the mild conditions of hydrolysis by H20 / MeOH / Fe leads to materials which are notably different from those produced by pyrolysis at high temperature, in particular as regards the average pore diameter as well as the distribution of the particles. pores. It is interesting to note that, after gentle elimination of the organic part, a final pyrolysis on the other hand only leads to a very moderate reduction in the specific surface area and in the porosity.

For silicas obtained by pyrolysis. the concentration of the organic fragment in the gel (varying by a factor of 9 between the G1 and
G2) has no influence on the spectroscopic and physical characteristics, in particular the porosity of the final material.

Thus, the S1 and S2 silicas obtained by pyrolysis both reveal a significant microporosity and a wide distribution of pores with a diameter of less than 10 A.

On the other hand, in the case of silicas obtained by hydrolysis, a marked difference is noted between the porosity characteristics of the silica originating from the gel G1 concentrated in organic fragment and that originating from the gel G2 where said fragment is "diluted" in the matrix of. silica.

The S3 and S4 silicas prepared by hydrolysis under mild conditions exhibit different characteristics, in particular as regards the size of the pores. They both show a narrow pore size distribution but this distribution is concentrated over a diameter of 52 A for S3 and 26 A for S4.

It is verified that the size of the pores of S3 and S4 is not directly related to the size of the organic fragment included in the gel, which has an average dimension less than 10 A, but rather depends on the concentration of organic fragment in the network silica.

In fact, the dilution of the organic fragment in the silicate network makes it possible to obtain pores of a smaller average diameter.

It is thus understood how one can control the porosity of the final silica by the formation of the hybrid gel.

Claims (20)

1. Polyfunctional compound containing a trialkoxysilylethynyl function of formula (1) (RO3) Si-C # C-R1-C # C-Si (OR3) in which: - R is an allyl group - R 'is chosen from aikylene radicals, alkenylene, alkynylene, cycloalkylene and divalent radicals derived from aromatic cyclic or heterocyclic aromatic compounds in which is present at least one heteroatom selected from ON and S; each of these radicals possibly being optionally substituted one or more times by a trialkoxysilylethynyl group of formula (1 ') (RO) 3Si-C - C- identical to the functional groups of formula (1). 2. Compound according to claim 1, in which: - R is a C, -C4 alkyl group - R 'is chosen from C, -C8 alkylene, Cz-Cs alkenylene, C4-C8 alkynylene, cycloalkylene. C3-C8 and divalent radicals derived from aromatic cyclic C6-C24 or heterocyclic aromatic compounds having 3 to 6 members and in which is present at least one heteroatom chosen from O, N and S; each of these radicals possibly being optionally substituted one or more times by a trialkoxysilylethynyl group of formula (1 ') (RO) 3Si-C # C- identical to the functional groups of formula (1). 3. A compound according to claim 1 or 2, wherein R is methyl. 4. A compound according to any one of claims 1 to 3, wherein R1 is a C 1 -C 8 alkylene group, preferably the n-butylene group. 5. A compound according to any one of claims 1 to 3, in which R ′ is chosen from p-phenylene, 5-trialkoxy silylethynyl-l .3-phenylene groups of formula:

and 2,5-di (trialkoxysilylethynyl) -1,4-phenylene of formula:

formulas in which the substituent groups of formula (1 ') are identical to the functional groups -C- = C-Si (OR) 3 of formula (1). 6. Process for the preparation of a compound according to claim 1 corresponding to formula (1) in which the group R1 is a divalent radical derived from a C6-C24 aromatic cyclic or aromatic heterocyclic compound having 3 to 6 members and in which at least one heteroatom chosen from among O, N and S is present, this radical being optionally substituted one or more times by a group of formula (1 '), comprising the following steps: (a) a compound of formula is reacted (2) X-R2-X where: - X is a leaving group, in particular a halo atom uncomfortable, - R2 is a divalent radical derived from a cydic compound aromatic C6-C24 or heterocyclic aromatic having from 3 to 6 links and in which is present at least one heteroatom chosen from O, N and S, this radical being optionally substituted one or more times by a leaving group X (2 ') identical to the previous one, with a trialkylsilylacetylene of formula (3) R33 Si-C = CH, in which R3 is a C, -C4 alkyl group, in excess relative to the total number of groups X ( 2 ') present in (2) to form a compound of formula (4) R33 Si-C # C-R4-C # C-SiR33 in which R4 is identical to the group R2 defined above, the possible groups (2 ') being transformed into groups (4') of formula -CC-SiR33, (b) the compound (4) is reacted with a strong base so as to form a polyanionic species of formula (5) :: Y #, # C # C-R5-C # C #, Y # in which - Y # represents a counter ion provided by the strong base, in particular the cation Lii, - R5 is a group identical to the group R4, the possible groups (4 ') being transformed into groups (5') of formula -C # C #, # Y, (c) the compound of formula (5) is reacted with a compound of formula (6) ZSi (OR) 3 in which Z is a halogen atom or an alkoxy group (OR), to result in a compound of formula (1) (RO) 3Si-CeC-Rt -cec-si (oR) 3 in which R1 is identical to the group R5, the possible groups (5 ') being transformed into groups of formula (1') -CC-Si (OR) 3 . 7. The method of claim 6, wherein the group X is a bromine atom. 8. A process for preparing a compound according to claim 1 corresponding to formula (1) in which the group R1 is a Ct-C8 alkylene group, comprising the following steps: (e) reacting a compound of formula (7) HC # C-R7-C # CH in which R7 is a C1-C8 alkylene group, optionally substituted one or more times by a group of formula (7 ') - C-CH, with a strong base to form a polyanionic species of formula (8) Y #, # C # C-R8-C # C #, # Y, in which :: - R8 is identical to the group R7, the possible groups (7 ') being transformed into groups of formula (8') -C # C #, gY, - Y # represents a counterion provided by the strong base, in particular the cation Lii, (f) the compound of formula (8) is reacted with a compound of formula (6) ZSi (OR) 3 in which Z is a halogen atom or an alkoxy group (OR), to result in a compound of formula (1) (RO) 3Si-CC-R1-CC-Si (OR) 3 in which R1 is identical to the group R ', the possible groups (8') being transformed into a group (11 -CC Si (OR) 3. 9. Polymer obtained by hydrolysis and polycondensation of a polyfunctional compound of formula (1) according to any one of claims 1 to 5. 10. Copolymer obtained by cohydrolysis and polycondensation of a polyfunctional compound of formula (1) according to any one of claims 1 to 5, in the presence of a tetraalkoxysilane of formula (9) Si (oR9) 4 in which R9 is a C1 -C4 alkyl group. 11. A process for preparing a polymer according to claim 9, whereby: (i) water is added to a solution of (1) in a solvent inertia, in an amount at least stoichiometric relative to the total number of hydrolyzable Si-OR bonds present in (1), (ii) the mixture is left until complete gelation, and (iii) the gel obtained is dried. 12. Process for preparing a copolymer according to claim 10, whereby: (i) is added to a solution of (1) and (9) in an inert solvent, water in an amount at least stoichiometric relative to the total number of hydrolyzable Si-OR and Si-O R9 bonds present in (1) ) and (9), (ii) the mixture is left until complete gelation, and (iii) the gel obtained is dried. 13. Process for preparing silica from a polymer according to claim 9 or from a copolymer according to claim 10, by which said polymer or copolymer is subjected to a hydrolysis reaction in the presence of a catalyst based on d. Fluoride ions, then the solid thus obtained is filtered, washed and dried. 14. The method of claim 13, wherein the hydrolysis is carried out in a hydromethanolic medium under reflux in the presence of catalytic ammonium fluoride. 15. Process for preparing silica from a polymer according to claim 9 or from a copolymer according to claim 10, by which said polymer or copolymer is subjected to pyrolysis in the presence of oxygen at a temperature of 400 to 700. @ VS. 16. The method of claim 13 or 14, wherein the solid isolated after hydrolysis is subjected to pyrolysis in the presence of oxygen at a temperature of 400 to 700 @ C. 17. Compound of formula (4) R33Si-C -C-R4-CC-SiR33 in which R4 is chosen from the radicals aikylene in C1-C8, alkenylene in C2-C8, alkynylene in C4- C8, cycloalkylene in C3-C8 and divalent radicals derived from C6-C2 "aromatic cyclic or heterocyclic aromatic compounds having from 3 to 6 members and in which is present at least one heteroatom chosen from O, N and S; each of these radicals possibly being optionally substituted with one or several times with a trialkylsilylethynyl group of formula (4 ') -CC-SiR33, formulas in which R3 is a C1-C4 alkyl group; with the proviso that, if R. is a phenylene radical, then R3 is a alkyl group in C2-C4. 18. Compound of formula (4) R3, Si-C # C-R4-C # C-SiR33 in which R4 is chosen from the radicals C1-C @ alkylene, C2-C8 alkenylene, C4- alkynylene. C8, C3-C8 cycloalkyleneand divalent radicals derived from C6-C2 * aromatic cyclic or heterocyclic aromatic compounds having 3 to 6 members and in which is present at least one heteroatom chosen from O, N and S; each of these radicals possibly being optionally substituted one or more times by a trialkylsilylethynyl group of formula (4 ') -C # C-SiR33, formulas in which R3 is a C2-C4 alkyl group. 19. Compound of formula (10) (RO), Si-C # C-R10-C # C- Si (OR) 3 in which R is a C, -C4 alkyl group and R10 is chosen from the radicals of C1-C8 alkylene, C2-C8 alkenylene, alkynylene C4-C8, C3-C8 cycloalkylene, and divalent radicals derived from C6-C24 aromatic cyclic or heterocyclic aromatic compounds having 3 to 6 members and in which is present at least one heteroatom selected from O, N and S, each of these radicals being substituted one or more times by a group of formula (4 ') -C # C-SiR33 in which R3 is a C1-C4 alkyl group and optionally one or more made by a group of formula (1 ') -C = -C-Si (OR) 3 identical to the functional groups of the compound of formula (10). 20. A compound according to claim 19, of formula: C6H3 (C # C-SiR33) (C # C-Si (OR) 3) 2 in which R is a C1 -C4 alkyl group and R3 is a C1-alkyl group. -C4.