WO2022248067A1 - Silirene-functionalized compounds and mixtures thereof for preparing siloxanes and conferring adhesion-promoting properties on them - Google Patents

Abstract

The invention relates to silirene-functionalized compounds, consisting of a substrate to which at least two silirene groups of the formula (I) are covalently bonded, wherein n = 0 or 1; wherein R is a divalent C1-C20 hydrocarbon group; wherein R1 is selected from the group including (i) C1-C20 hydrocarbon group, (ii) C1-C20 hydrocarbonoxy group, (iii) silyl group -SiR4R5R6, wherein R4, R5, R6 independently of each other represent a C1-C6 hydrocarbon group, (iv) amino group -NRy2, wherein Ry independently of each other is selected from the group including (iv.i) hydrogen, (iv.ii) C1-C20 hydrocarbon group and (iv.iii) silyl group -SiR4R5R6, and (v) imino group -N=CR7R8, wherein R7, R8 independently of each other are selected from the group including hydrogen, C1-C20 hydrocarbon group and silyl group -SiR4R5R6; wherein R2, R3 independently of each other are selected from the group including hydrogen, halogen, C1-C20 hydrocarbon group, silyl group -SiR4R5R6 and organopolysiloxane group -(CH2)y-[SiR9R10-O]χ-[SiR11R12R13], wherein R9 to R13 independently of each other are selected from the group including methyl, ethyl, phenyl, ethinyl and vinyl, wherein index x is zero or an integer from 1 to 200 and index y is zero or an integer from 1 to 10, and wherein R2 and R3 can be part of a cyclic group. The invention further describes processes for preparing these compounds and mixtures for cross-linking and adhesion promotion containing these compounds.

Description

Silene-functionalized compounds and mixtures thereof for the production and adhesion promotion of siloxanes

The invention describes silirene-functionalized compounds consisting of a substrate to which at least two silirene groups of the formula (I) are covalently bonded. Also described is a process for preparing these compounds and mixtures for crosslinking and adhesion promotion, containing these compounds.

Silicones (also called poly(organo)siloxanes or siloxanes for short) can be used in a variety of ways due to their chemical and physical properties. Unlike carbon-based plastics, the van der Waals forces between siloxane polymer chains are weak, which is why high molecular weight siloxane polymers are still flowable. In order to obtain dimensionally stable, rubber-elastic silicones, the polymer components have to be crosslinked with one another.

In general, a distinction can be made between addition crosslinking, condensation crosslinking and free-radical crosslinking. During addition crosslinking, vinyl-functionalized polyorganosiloxanes react with hydridosiloxanes (hydrosilylation).

The reaction requires the use of catalysts containing noble metals (e.g. based on platinum), which cannot be recovered. The majority of platinum-crosslinking systems are thermally activated, and a few UV-activatable systems (primarily based on platinum catalysts) are also known. However, the UV-crosslinking systems require significantly higher amounts of the catalyst, long exposure times and high exposure intensities in order to achieve the crosslinking times and product properties of thermally cured systems. In the case of condensation crosslinking, terminal Si-OH or Si-OR groups with typically multifunctional siloxane building blocks (containing, for example, Si-O-CH ₃ , Si-O-C ₂ H ₅ , Si-O-COCH ₃ ) are cured by atmospheric moisture and in the presence a metal-based catalyst (e.g. based on tin) reacted. This leads to the elimination of small, volatile compounds (e.g. acetic acid or alcohols) and consequently to a loss of material (shrinkage). In contrast to most addition-curing formulations, condensation-curing systems can be handled as one-component systems. Radical crosslinking, on the other hand, uses organic peroxides, for example, which decompose into highly reactive radicals through thermal or photolysis and link functional polyorganosiloxanes (eg vinyl-methyl-siloxanes) with one another in a free-radical manner.

While in the aforementioned processes the siloxanes are crosslinked by catalysts or initiators (in the case of free-radically crosslinking systems), catalyst-free crosslinking can also be done by silirane-containing compounds, as described in PCT/EP2019/083744. The crosslinking is based on the reactivity of intermediately formed silylenes (cf.

Scheme 1). Silylenes are highly reactive divalent silicon compounds and react with a large number of functional groups such as Si-H, Si-OH or CH with insertion. With unsaturated structural motifs such as alkenes, alkynes or carbonyl compounds, silylenes form cyclic secondary products by addition.

Scheme 1: Siliranes can be cleaved by thermolysis or photolysis to give an olefin and a silylene.

Due to their high reactivity, according to

PCT/EP2019/083744 does not use the silylenes themselves, but silirane compounds as storage-stable and easy-to-handle precursors. These can be split into silylene and olefins in particular by thermal activation (thermolysis), with the driving force for dissociation being the ring strain of the siliranes. Photochemical activation of the siliranes to silylenes is also possible, but due to their weak absorption behavior, siliranes can only be converted into silylenes by UV-C light with wavelengths below <300 nm at high intensity and long exposure times. Activation at wavelengths above 300 nm would be technically much easier to implement, but this would require compounds with better absorption bands in the UV-A range.

However, overlapping with the absorption wavelength ranges of other UV-active compounds (e.g. platinum UV catalysts) can be problematic, so that weaker absorbing compounds may only be activated moderately or not at all. Furthermore, siloxanes, regardless of whether they are crosslinked to form elastomers or not, show only low adhesion properties on plastic surfaces made of polyolefins (e.g. polyethylene (PE) and polypropylene (PP)), polyethylene terephthalate (PET) or polycarbonate (PC), which is due to the slightly polar to non-polar nature of the plastics. There can be no mechanically stable connection through polar interaction or covalent bonding. Adhesion to plastic substrates can often only be achieved by complex manipulations of the surface, e.g. by pre-treating with solvents, a multi-stage oxygen plasma treatment and/or by applying a primer (U. Stöhr, Vacuum in Research and Practice 2015, 27, 16-21).

US 2011/0105777 A1 discloses 1,4-disilacyclohexanes, which are formed from intermediately generated, halogenated silacyclopropenes, so-called silirenes. The monomeric silacyclopropenes for this are generated from hydride-containing halosilanes and acetylenes using quaternary organophosphonium salts, however, due to their high reactivity, the silacyclopropenes dimerize rapidly to form 1,4-disilacyclohexanes. The compound class of 1,4-disilacyclohexanes is described as a starting material for the production of inorganic/organic hybrid materials.

JP53-059656 A2 discloses alkyl- and aryl-substituted silacylopropenes (monosilrenes) and their photochemical preparation from disilane- and phenyl-substituted acetylenes by using a mercury vapor or xenon gas discharge lamp. In addition, compound-typical photochemical and thermal cyclization reactions with unsaturated carbon-carbon (eg alkynes) and Called carbon-element multiple bonds (e.g. ketones).

Furthermore, the palladium-catalyzed dimerization of the aforementioned silirenes is described.

Semenov et al. (Russian Journal of Applied Chemistry 2012, 85, 2, 320-326) describe the functionalization of OH-terminated polyorganosiloxanes by reaction with silacyclopropenes produced as intermediates. The silacyclopropene is generated by photolysis of phenylethynyl-substituted disilanes in OH-terminated polyorganosiloxane and reacts with this rapidly with nucleophilic ring opening through the OH function. The previously OH-terminated siloxane now has vinyldimethylsilyl end caps and, for example, is converted to a silicone elastomer with hydridopolysiloxanes in the presence of the platinum-based Speyer catalyst.

Seyferth et al. (J. Organomet. Chem. 1984, 272, 123-129) describe the first stable silacyclopropene and its preparation by thermolysis of a silacyclopropane (silirane) in the presence of bis(trimethylsilyl)acetylene. Furthermore, the thermal release of dimethylsilylene from the silacyclopropene described is demonstrated. The ring opening of the silirene by alcohols has also been described.

Furthermore, Seyferth et al. (Organometallics 1984, 3, 1897-1905) the thermal and photochemical reactivity of silacyclopropenes with cyclic and acyclic carbonyl compounds as well as mono-, dienes and acetylenes. The resulting reaction products are primarily cyclic compounds.

M. Ishikawa, A. Naka, J. Oshita provide an overview of the preparation and reactivity of monomeric silacyclopropenes (Asian. J. Org. Chem. 2015, 4, 1192-1209). The object of the invention was to provide a metal-free system for silicone crosslinking that could be activated under UV-A conditions.

This object is achieved by silirene-functionalized compounds consisting of a substrate to which at least two silirene groups of the formula (I)

(I), are covalently bonded, where n = 0 or 1, the radical R is a divalent C ₁ -C ₂₀ hydrocarbon radical.

The radical R ¹ is selected from the group with (i) C ₁ -C ₂₀ hydrocarbon radical, (ii) C ₁ -C ₂₀ hydrocarbonoxy radical, (iii) silyl radical -SiR ⁴ R ⁵ R ⁶ , where R ⁴ , R ⁵ , R ⁶ are independently C ₁ -C ₆ hydrocarbyl, (iv) amine radical -NR ^Y ₂ , wherein R ^y is independently selected from the group with (iv.i) hydrogen, (iv.ii) C ₁ -C ₂₀ hydrocarbyl and (iv.iii) silyl -SiR ⁴ R ⁵ R ⁶ , and (v) imine -N=CR ⁷ R ⁸ wherein R ⁷ , R ⁸ are independently selected from the group with hydrogen , C ₁ -C ₂₀ hydrocarbon radical and silyl radical -SiR ⁴ R ⁵ R ⁶ .

The radicals R ² , R ³ are independently selected from the group consisting of hydrogen, halogen, C ₁ -C ₂₀ hydrocarbon radical, the silyl radical -SiR ⁴ R ⁵ R ⁶ and organopolysiloxane radical - (CH ₂ ) y- [SiR ⁹ R ¹⁰ -O] _x - [SiR ¹¹ R ¹² R ¹³ ] where R ⁹ through R ¹³ are independently selected from the group consisting of methyl, ethyl, phenyl, hydrogen, ethynyl and vinyl, where the index x is zero or an integer value of 1 to 200 and the index y is zero or is an integer from 1 to 10, and where R ² and R ³ can also be part of a cyclic radical.

The silicone-functionalized compounds can be used both as crosslinkers for silicones (formation of elastomers) and as adhesion promoters for coating plastics with silicones, without having to resort to metal-containing catalysts. Their crosslinking or adhesion-promoting effect can be induced not only thermally but also photochemically. The unsaturated structural motif of silacyclopropene, often also referred to as silirene, can be photochemically activated at wavelengths between 300 and 400 n because of its pseudo-aromatic character. This results in the advantage that the crosslinking/adhesion promotion can be stimulated in a more targeted manner with low-energy light. With particular advantage, an overlap with the absorption wavelengths of platinum UV catalysts often contained in existing products can be avoided in order to avoid competing absorption processes.

The following compound is not included in the invention

The substrate is preferably selected from the group consisting of silanes, organosilicon compounds, silicic acids, hydrocarbons, carbon-based oligomers and polymers.

The substrate is particularly preferably selected from the group consisting of siloxanes, precipitated silica, pyrogenic silica, polyolefins, acrylates, polyacrylates, polyvinyl acetates, poly urethanes and polyethers. The polyethers can be, for example, polyethers made from propylene oxide and/or ethylene oxide units.

According to a preferred embodiment of the invention, the substrate is an organosilicon compound of general formula (II)

(Si0 _4/2 )a(R ^X Si0 _3/2 ) _b (R'Si0 _3/2 ) _b '(R ^X 2Si0 _2/2 ) _c (R ^X R'Si0 _2/2 ) _c '

(R ' ₂ SiO _2/2 ) _c " (R ^x ₃ SiO _1/2 )d(R 'R ^x ₂ SiO _1/2 )d-(R ' ₂ R ^x SiO _1/2 ) _d"'

(R ' ₃ SiO _1/2 ) _d "_' (II), wherein R ^x is independently selected from the group consisting of hydrogen, halogen, unsubstituted or substituted C ₁ -C ₂₀ hydrocarbyl and unsubstituted or substituted C ₁ -C ₂₀ - hydrocarbyloxy radical, wherein the subscripts a, b, b', c, c', c'', d, d', d'', d''' indicate the number of the respective siloxane unit in the compound and are independently zero or one are integers from 1 to 100,000, with the proviso that the sum of a, b, b', c, s', c'', d, d', d'', d''' is at least 2 and at least one of the subscripts b', c', d' is h 2 or at least one of the subscripts c'', d'' or d''' is non-zero; and wherein R' is the silirene group of formula (I) is.

The radical R in the formula (I) is preferably a C ₁ -C ₃ - alkylene radical, particularly preferably an ethylene radical.

The substituent R ¹ on the Si atom in the formula (I) can be used to exert a kinetic and thermodynamic influence on the reactivity and stability of the silirene-functionalized compounds. R ¹ is preferably a C ₁ -C ₆ hydrocarbon radical or amine radical -N(SiR ⁴ R ⁵ R ⁶ ) ₂ , where R ⁴ , R ⁵ , R ⁶ are independent of one another are a C ₁ -C ₆ hydrocarbyl radical. R ¹ is particularly preferably a C ₁ -C ₆ -alkyl radical or -N(SiMe ₃ ) ₂ .

The indices a, b, b', c, c', c'', d, d'' and d''' preferably assume the value zero and the index d' the value 2; where in formula (I) the index n has the value 1, R is a C ₁ -C ₃ alkylene radical and R ¹ is a C ₁ -C ₆ hydrocarbon radical, a silyl radical -SiR ⁴ R ⁵ R ⁶ or an amine radical -N is (SiR ⁴ R ⁵ R ⁶ ) ₂ wherein R ⁴ , R ⁵ , R ⁶ are independently C ₁ -C ₆ hydrocarbon radicals. The radicals R ² , R ³ are independently selected from the group consisting of hydrogen, halogen, C ₁ -C ₂₀ hydrocarbon radical, silyl radical --SiR ⁴ R ⁵ R ⁶ and organopolysiloxane radical

- (CH ₂ ) _Y - [SiR ⁹ R ¹⁰ -O] _x -[SiR ^1:L R ¹² R ¹³ ], where the index x is zero or an integer value from 1 to 100 and the index y is zero or an integer value is from 1 to 8, and wherein R ⁹ to R ¹³ are independently methyl, phenyl, hydrogen or vinyl radicals.

According to a further embodiment, the indices a, b, b', c, c', c'', d, d'' and d''" take the value zero and the index d' the value 2, where in formula (I ) the index n has the value 1, R is an ethylene radical and R ¹ is a C ₁ -C ₆ alkyl radical, an amine radical -N(SiMe ₃ ) ₂ or a silyl radical -SiR ⁴ R ⁵ R ⁶ , where R ⁴ , R ⁵ , R ⁶ are independently C ₁ -C ₆ hydrocarbon radicals, and where R ² , R ³ are independently selected from the group with hydrogen, C ₁ -C ₂₀ hydrocarbon radical, silyl radical -SiR ⁴ R ⁵ R ⁶ and organopolysiloxane residue

- (CH ₂ ) _y -[SiR ⁹ R ¹⁰ -O] _x -[SiR ¹¹ R ¹² R ¹³ ], where the index x is zero or an integer value from 1 to 50 and the index y is zero or an integer value from 1 to 4 and wherein R ⁹ to R ¹³ are independently methyl, hydrogen or vinyl radicals. The radical R ^x in the formula (II) is preferably selected independently from the group consisting of methyl, ethyl, hydrido, vinyl and phenyl.

Another aspect of the invention relates to a method for preparing the silirene-functionalized compounds. For this purpose, a silirane-containing precursor, for example compounds as described in PCT/EP2019/083744, with an alkyne of the general formula R ² -C CR ³ in an organic

Solvent in the temperature range from 100 to 150 ° C or implemented with the addition of silver triflate in the temperature range from 50 to 120 ° C. The radicals R ² , R ³ are selected independently of one another

the group with hydrogen, halogen, C1-C ₂₀ hydrocarbon residue, silyl residue -SiR ⁴ R ⁵ R ⁶ , in which R ⁴ , R ⁵ , R ⁶ are independently a C ₁ -C ₆ hydrocarbon residue, and organopolysiloxane residue - (CH ₂ ) _y - [ SiR ⁹ R ¹⁰ -O] _x - t SiR ¹¹ R ¹² R ¹³ ] where R ⁹ to R ¹³ are independently selected from the group consisting of methyl, ethyl, phenyl, ethynyl and vinyl, where the index x Zero or an integer from 1 to 200 and the index y is zero or an integer from 1 to 10, and where R ² and R ³ can be part of a cyclic radical.

The organic solvent is preferably an ether and/or an aromatic solvent. Diethyl ether, THF, benzene and toluene are particularly preferred.

Another subject of the invention is a mixture containing a) at least one of the silirene-functionalized compounds described and b) at least one compound A which has at least two radicals R ¹⁴ , the radicals R ¹⁴ being selected independently of one another are from the group with (i) -Si-H, (ii) -OH, (iii) -C _x H ₂ x-OH, where x is an integer ranging from 1 to 20,

(iv) -C _x H _2x -NH ₂ where x is an integer ranging from 1 to 20, (v) -SH, (vi) -R ¹⁵ _n -CR ¹⁷ =CR ¹⁸ 2 and (vii) - R ¹⁵ _n -CR ¹⁹ =0, where R ¹⁵ is a divalent C ₁ -C ₂₀ hydrocarbyl radical, n = 0 or 1 and R ¹⁷ , R ¹⁸ and R ¹⁹ are independently hydrogen or C ₁ -C ₆ hydrocarbyl radical .

In general, compound A can be a polyether with at least one OH terminus.

The compound A is preferably selected from siloxanes of the general formula (III)

(Si0 _4/2 ) a (R ^x Si0 _3/2 ) b (R 'SiOa _/2 ) b' (R ^x ₂ Si0 _2/2 ) c (R ^X R ' Si0 _2/2 ) _C '

(R ' ₂ SiO _2/2 ) c" (R ^x ₃ SiO _1/2 ) d (R 'R ^x ₂ SiO _1/2 ) * (R ' ₂ R ^x SiO _1/2 ) d '''

(R ' ₃ SiO _1/2 ) d"' ( HI ) ·

R ^x is independently selected from the group consisting of halogen, an unsubstituted C ₁ -C ₂₀ hydrocarbon radical and a substituted C ₁ -C ₂₀ hydrocarbon radical.

R' is independently selected from the group consisting of (i) hydrogen, (ii) -OH, (iii) -C _x H _2x -OH, where x is an integer in the range 1-20, (iv) -O _c H _2c -NH ₂ where x is an integer in the range 1-20, (v) -SH, (vi) -R ¹⁵ _n -CR ¹⁷ =CR ¹⁸ 2 and (vii) -R ¹⁵ _n -CR ¹⁹ = 0, in which R ¹⁵ is a divalent C ₁ -C ₂₀ hydrocarbon radical, n = 0 or 1 and the radicals R ¹⁷ to R ¹⁹ are independently hydrogen or C ₁ -C ₆ hydrocarbon radicals.

The indices a, b, b', c, c', c'', d, d', d'', d'''' indicate the number of the respective siloxane unit in the compound and independently mean an integer in the range from 0 to 100,000, with the proviso that the sum of a , b , b ' , c, c', c'', d, d', d'', d''' has at least the value 2 and at least one of the indices b', c', d' is ≥ 2 or at least one of the indices c'',d'' or d'" is not equal to 0.

The silirene-functionalized compounds are stable precursors of highly reactive silylenes. After activation, a silylene residue is formed from the silirene group. The silirene-functionalized compounds must have at least two silirene groups in order to function as crosslinkers and adhesion promoters. It is imperative that the Si atoms of the silirene groups are bridged to one another via a basic structure (cf. Scheme 2) in order to link polymers that are otherwise functional to one another.

Scheme 2: Top: The Si atoms of the silirene-functionalized compound are bridged through a backbone, resulting in a crosslinkable, reactive bis-silylene species upon activation. Bottom: The silirene groups are not bridged via the Si atoms, resulting in non-crosslinking cleavage products upon activation.

The molar ratio of silirene groups to functional groups in the siloxane of the general formula (III) is preferably in a range from 5:1 to 1:5.

Another subject of the invention are mixtures containing a) at least one of the silicone compounds described and b) at least one natural or synthetic polymer selected from the group consisting of addition-crosslinking silicone compositions, condensation-crosslinking silicone compositions, hybrid materials/STP, inorganic polymers and organic polymers.

For the purposes of the present invention, the term addition-crosslinking silicone compositions generally refers to hydrosilylatable mixtures containing hydridopolysiloxanes, alkenyl-containing polyorganosiloxanes and fillers (e.g. silicas). These mixtures can only be crosslinked thermally or photochemically to form elastomeric silicones in the presence of catalysts (e.g. the platinum-based Karstedt catalyst) and inhibitors. Such mixtures are described, for example, in EP 0651 019 A1 or EP 0 444 960 A2. The addition-crosslinking silicone compositions therefore contain metal catalysts.

In the context of the invention, condensation-crosslinking silicone compositions are generally mixtures containing OH- or alkoxy-terminated polyorganosiloxanes and multifunctional polysiloxane crosslinkers (for example R-S1X ₃ with X=alkoxy, carboxy or amino). These condense to form three-dimensional networks when exposed to atmospheric moisture and in the presence of a metal catalyst (eg organic tin or titanium compounds) with the release of water, alcohols, acetic acid or amines. Such mixtures are described, for example, in DE 1026 520 or US Pat. No. 3,696,090. The condensation-crosslinking silicone masses contain metal catalysts.

Hybrid materials/STP (silane-terminated polymers) are generally reactive silane-terminated within the meaning of the invention organic polymers (e.g. polyether) which are used, for example, as adhesives, sealants and coating materials. Such materials are described, for example, in WO 2017/137281 A1.

In the context of the invention, inorganic polymers are generally natural and synthetic inorganic polymers (e.g. silicic acids, silicate structures, polysilanes and polysiloxanes). For the purposes of the invention, organic polymers are generally natural and synthetic organic polymers suitable for producing moldings, coatings or laminates. Examples of such polymers can be found, for example, in U.S. 5,792,812; US 2007/0141250 A1 and US 4,686,124.

It was recognized that the silirene-functionalized compounds, or the reactive silylenes produced from them, in addition to their use as noble-metal-free crosslinkers for silicones, are suitable for otherwise crosslinkable siloxanes (technology basis: hydrosilylation or condensation crosslinking) on unreactive polymer substrates such as PE, PP, to bring PET and PC to liability. The Siliren-functionalized compounds act as adhesion promoters between the inert polymer carrier body and the applied crosslinkable siloxane mixture by forming covalent bonds. The mixture according to the invention is therefore, with particular advantage, a self-adhesive mixture.

Also encompassed by the invention are moldings containing the mixture described and a slightly polar to non-polar carrier material.

The molding is preferably selected from the group consisting of extrusion or injection molding, single-layer or multi-layer laminates (e.g. produced by spin coating, Calendering or dipping processes), encapsable shaped bodies (e.g. produced in electrocasting by filling, dipping or plasticizing), bondable or sealable shaped bodies (reactive adhesives) and transitions between identical or different shaped bodies of the same or different carrier materials. The latter means in particular jointing compounds for bonding several dissimilar materials.

The shaped body can contain the carrier material in the form of a coating. The shaped body can consist of the carrier material to which the mixture is applied.

The carrier material preferably comprises at least one synthetic hydrocarbon polymer selected from the group consisting of polyolefins made from mono- or polyenes, polyhalogen olefin, polyether, polyvinyl chloride, polyvinylidene difluoride, polytetrafluoroethene, polycarbonate, polyester and copolymers thereof. Furthermore, the carrier material can consist of or comprise polymer blends of the hydrocarbon polymers mentioned.

The copolymers can be, for example, ethylene propylene diene monomer rubber (EPDM) or acrylonitrile butadiene styrene (ABS).

The mixture according to the invention can be cured by a process for curing by means of thermal and/or photochemical activation. For curing, the mixture is first brought into contact with the carrier material.

Photochemical activation in a wavelength range from 300 to 400 n is particularly preferred. Also included in the invention is a process for preparing siloxanes (siloxane elastomers), comprising the steps

- Providing the mixture described (containing silirene-functionalized compound and natural or synthetic polymer)

- Reacting the mixture by thermal, photochemical or catalytic activation.

The thermal activation preferably takes place in a temperature range from 0.degree. C. to 200.degree. C., preferably from 10 to 180.degree. C., particularly preferably from 15 to 150.degree.

Thermal activation can also be done in two stages and include the following steps:

- Setting a temperature T1 in a range from 0°C to 140°C and

- Setting a temperature T2 in a range from 120°C to 180°C

It applies that T1 < T2.

The photochemical activation is preferably carried out with actinic radiation in a wavelength range from 300 to 800 nm, preferably from 300 to 500 nm, particularly preferably from 300 to 400 nm.

In general, catalysts can also be used to accelerate adhesion promotion. Compounds that destabilize silirenes and thus cause cleavage into silylene and olefin are suitable as catalysts. examples for such catalysts are AgOTf and Cu(OTf),Cu(OTf) ₂ or Zn(OTf) ₂

FIG. 1 shows ²⁹ Si NMR spectra of a reaction mixture of triethylsilane and silacyclopropene 7c after activation.

FIG. 2 shows ¹ H-NMR spectra of a reaction mixture of triethylsilane and silacyclopropene 7c after activation.

FIG. 3 shows a ¹ H- ²⁹ Si HMBC NMR spectrum of a reaction mixture of triethylsilane and silacyclopropene 7c after activation.

FIG. 4 shows ²⁹ Si NMR spectra of a reaction mixture of triethylsilane and silacyclopropene 7d after activation.

FIG. 5 shows ¹ H-NMR spectra of a reaction mixture of triethylsilane and silacyclopropene 7d after activation.

FIG. 6 shows a ²⁹ Si-NMR and a ¹ H-NMR spectrum of a reaction mixture of pentamethyldisiloxane and silacyclopropene 7d after photochemical activation.

examples

General Information

All syntheses were carried out in the absence of atmospheric oxygen and humidity in heated glassware. Argon or nitrogen was used as protective gas. The chemicals used were obtained from the companies Wacker Chemie AG, but GmbH or Sigma-Aldrich. All solvents were dried and distilled before use. All silicone oils were before use about AI2O ₃ and 3 Ä Molecular sieve dried and degassed. The molecular weights are given as average values and relate to the manufacturer's information. The polyorganosiloxanes used are random copolymers. Al ₂ O ₃ (neutral) and activated carbon were dried at 150° C. under high vacuum for 72 h.

Magnetic resonance spectroscopy ( ¹ H, ¹³ C, ²⁹ Si) was performed with a Bruker Avance III 500 MHz.

Mass spectrometry was carried out using a LIFDI-MS 700 with an ion source from Linden CMS.

Elemental analyzes were carried out by the microanalytical laboratory of the Faculty of Chemistry at the Technical University of Munich using a Vario EL from Elementar.

Photoreactions were carried out using Luzchem LZC-UVA (350 nm) fluorescent tubes from Hitachi.

The mixtures were thermally cured in a "LHT6/30" drying cabinet from Carbolite-Gero.

UV/vis spectra were measured in acetonitrile (concentrations: 0.1-0.3 mmol/L) at room temperature using a Varian "Cary 50 Scan UV-Vis" spectrophotometer.

Unless otherwise stated, the siliran starting materials were synthesized according to Herz et al., Green Chem., 2020, 22, 4489).

Synthesis examples Synthesis Example 1: Preparation of monofunctional 1,1-di-tert-butyl-2,3-substituted silirenes 7a to 7e (scheme 3)

Scheme 3: Representation of the silacyclopropenes 7a to 7e.

The syntheses of compounds 7a to 7e were carried out analogously and are summarized. 1,1-di-tert-butyl-2,3-dimethylsilirane

(1.26 mmol, 1 eq.) is placed in a 25 ml Schlenk flask with 5 ml of diethyl ether. The 1,2-substituted acetylene (1.25 mmol, 1.0 eq.) is added to this reaction mixture and mixed. Then the catalyst AgOTf (silver trifluoromethanesulfonate, 1.25 μmol, 0.001 eq.) is dissolved in 0.5 ml diethyl ether, added and stirred at 25° C. for 24 h. The mixture is then filtered over dried neutral alumina to remove the catalyst. The solvent is removed in vacuo and the crude product is isolated by distillation.

1.1-Di-tert-butyl-2,3-dimethyl-silrene (7a)

Distillation: 5-10 ^“2 mbar, 70°C; Yield: 80%; colorless liquid. 1H NMR: (294K, 500MHz, _C6D6 ) d = 1.08 (s, 18H, CH3 ₎ , 2.06 ( _s , 6H, CH3 ₎ .

²⁹ Si NMR: (294K, 99.4MHz, _{C6D6 )} d = -67.5. λ _max = 250 nm (cf. starting material 1,1-di-tert-butyl-2,3-dimethylsilirane: λ _max = 225 nm)

1.1-di-tert-butyl-2-methyl-3-phenyl-silrene (7b)

distillation: 5*10 ^-2 mbar, 100°C; Yield: 65%; colorless liquid. ¹ H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 1.12 (s, 18 H, CH ₃ ), 2.34 (s,

3 H, CH ₃ ), 7.08-7.11 (m, 1 H, CH _arom .), 7.23-7.27 (m, 2 H, CH _arom .), 7.53“7.55 (m, 2 H, CH _arom .).

¹³ C NMR: (294 K, 125.8 MHz, C ₆ D ₆ ) d = 15.8, 21.7, 30.3, 127.3,

128.8, 129.9, 136.2, 150.0, 151.0.

²⁹ Si NMR: (294 K, 99.4 MHz, _{C6 D6} ) d = -68.4. λ _max — 280nm

1.1-Di-tert-butyl-2,3-bis(trimethylsilyl)silrene (7c)

Distillation: 5*10 ^-2 mbar, 80°C; Yield: 72%, colorless liquid. ¹ H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.27 (s, 18 H, CH ₃ , TMS),

1.03 (s, 18H, _CH3 , tBu).

¹³ C NMR: (294K, 125.8MHz, _{C6 D6} ) d = -0.1, 20.0, 30.7, 184.4.

²⁹ Si NMR: (294 K, 99.4 MHz, _{C6 D6} ) d = -86.5, -13.1. λ _max = 350 nm

1.1-Di-tert-butyl-2-phenyl-3-trimethylsilylsilrene (7d)

Distillation: 5·10 ^“2 mbar, 50°C; Yield: 86%; colorless liquid. ¹ H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.33 (s, 9 H, CH ₃ , TMS),

1.10 (s, 18H, CH _3r tBu), 7.07-7.13 (m, 1H, CH _arom .), 7.22-

7.28 (m, 2 H, CH arom.), 7.59-7.65 (m, 2 H, CH _arom .). ²⁹ Si NMR:

(294K, 99.4MHz, _{C6 D6} ) d = -72.2, -14.0. λ _max 325nm

1.1-di-tert-butyl-2,3-diphenylsilrene (7e)

Distillation: 5-10 ^~2 mbar, 120°C; Yield: 89%; colorless crystals.

^X H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 1.16 (s, 18 H, CH ₃ , tBu),

7.04-7.09 (m, 2 H, CH _arom .), 7.16-7.21 (m, 4 H, CH _arom .), 7.64-7.69 (m, 4 H, CH _arom .)

¹³ C NMR: (294 K, 125.8 MHz, C ₆ D ₆ ) d = 21.9, 30.3, 127.7, 128.9, 129.2, 132.0, 136.6, 151.8.

²⁹ Si NMR: (294K, 99.4MHz, _{C6 D6} ) d = -67.1. λ _max ⁼ 275 nm

Synthesis Example 2: Preparation of bis-functional 1,3-bis-(2-(1-(tert-butyl)-2,3-bis(trimethylsilyl)siliren-1-yl)ethyl)-1,1,3, 3-tetramethyldisiloxane V1 (Scheme 4).

Scheme 4: Preparation of the silacyclopropene V1.

Bis-silacyclopropane (PI, 200 mg, 424 μmol, 1 eq.) is mixed with bis(trimethylsilyl)-acetylene (181 mg, 1.06 mmol, 2.5 eq.) and 5 mL toluene in a 25 mL Schlenk flask at 110° C and refluxed for 72 h. The solvent and excess acetylene are then removed at 2*10 ^-2 mbar and 50°C. 196 mg (66%, 280 μmol) of the Siliren crosslinker V1 are obtained as a colorless oil. 1H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.15 (s, 12 H, OSi-CH ₃ ),

0.30 (s, 36 H, CH ₃ , TMS), 0.75-0.83 (m, 4 H, CH ₂ ), 0.90-0.98 (m, 4 H, CH ₂ ), 1.02 (s, 18 H, CH _3r tBu) .

²⁹ Si NMR: (294 K, 99.4 MHz, _{C6 D6} ) d = -87.0, -12.9, 7.63. λ _max = 350 nm (cf. PI: λ _max 220 nm)

Synthesis Example 3: Preparation of bis-functional 1,1'-((1,1,3,3-tetramethyldisiloxane-1,3-diyl)bis(ethane-2,1-diyl))bis(N,N,2, 3-tetrakis(trimethylsilyl)-silren-1-amine) V2 (Scheme 5).

Scheme 5: Preparation of silacyclopropene V2.

Bis-silacyclopropane (P2, 50.0 mg, 73.8 μmol, 1 eq.) is treated with bis(trimethylsilyl)-acetylene (31.4 mg, 184 μmol, 2.5 eq.) and 5 mL toluene in a 25 mL Schlenk flasks, heated to 110°C and refluxed for 72 h. Then the solvent and excess acetylene are removed at 2*10 ^-2 mbar and 50°C. 501 mg (75%, 55.3 μmol) of the Siliren crosslinker V2 are obtained as a colorless oil. 1H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.15 (s, 12 H, OSi-CH ₃ ),

0.24-0.0.27 (m, 4H, _CH2 ), 0.28-0.30 (m, 4H, CiFe), 0.31 (s, 36H, CSi- _CH3 , TMS), 0.35 (s, 36H, NSi _-CH3 , TMS).

²⁹ Si NMR: (294 K, 99.4 MHz, _{C6 D6} ) d = -92.3, -13.0, 3.4, 7.7. λ _max = 350 nm (cf. P2: λ _max 224 nm)

Synthesis Example 4 Preparation of bis-functional 1,3-bis(2-(1-(tert-butyl)-2-phenyl-3-(trimethylsilyl)-silren-1-yl)ethyl)-1,1,3, 3-tetramethyldisiloxane V3 (Scheme 6)

Bis-silacyclopropane (PI, 200 mg, 424 μmol, 1 eq.) is treated with l-phenyl-2-trimethylsilyl-acetylene (185 mg, 1.06 mmol,

2.5 eq.) and 5 mL toluene in a 25 mL Schlenk flask mixed, heated to 110°C and refluxed for 72 h. The solvent and excess acetylene are removed at 2*10 ^-2 mbar and 80°C. 213 mg (71%, 301 μmol) of the Siliren crosslinker C3 are obtained as a yellowish oil. 1H NMR: (294 K, 500 MHz, _{C6 D6} ) d - 0.32 (s, 12 H, OSi- _CH3 ),

0.60 (s, 18H, _CH3 , TMS), 1.01-1.04 (m, 4H, _CH2 ), 1.16-1.12 (m, 4H, _CH2 ) _r 1-33 (s, 18H, _CH3 , tBu), 7.33-7.36 (m,

2 H, CH _arom . ) , 7.47-7.52 (m, 4H, CH _arom . ) , 7.86-7.93 (m,

4 H, CH _arom . ) ·

²⁹ Si NMR: (294 K, 99.4 MHz, _{C6 D6} ) d = -72.2, -13.7, 7.8. λ _max = 320 nm (cf. PI: λ _max 220 nm)

Synthesis Example 5: Preparation of bis-functional 1,1'-((1,1,3,3-tetramethyldisiloxane-1,3-diyl)bis(ethane-2,1-diyl))bis(2-phenyl-27, 27,3-tris(trimethylsilyl)-silren-1-amine) V4 (Scheme 7).

Scheme 7: Preparation of the silacyclopropene V4.

Bis-silacyclopropane (P2, 150 mg, 221.4 μmol, 1 eq.) is treated with l-phenyl-2-trimethylsilyl-acetylene (96.5 mg, 553.4 μmol,

2.5 eq.) and 5 mL toluene in a 25 mL Schlenk flask, heated to 110°C and refluxed for 72 h. The solvent and excess acetylene are removed at 2*10 ^-2 mbar and 80° C., and 137 mg (68%, 151 μmol) of the Siliren crosslinker V4 are obtained as a colorless oil. ¹ H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.19 (s, 12 H, OSi-CH ₃ ), 0.24 (s, 18 H, CSi-CH ₃ , TMS), 0.29 (s , 36H, NSi- _CH3 , TMS),

0.59-0.70 (m, 4H, CH ₂ ), 1.19-1.36 (m, 4H, CH ₂ ), , 7.05-7.09 (m, 2H, CH _arom . ), 7.22-7.26 (m, 4H, CH _arom . ), 7.47-7.52 (m, 4 H, CH _arom . ) .

²⁹ Si NMR: (294 K, 99.4 MHz, _{C6 D6} ) d = -80.8, -13. 2, 3.4, 7.9. λ _max = 320 nm (cf. P2: λ _max 224 nm)

Synthesis example 6.0: Preparation of the precursor Px2 of trifunctional silirene crosslinker V5 (scheme 8).

Scheme 8: Representation of the Px2 precursor.

Tris-vinylsiloxane (Pxl, 20.0 g, 57.7 mmol, 1 eq.), trichlorosilane (35.2 g, 260 mmol, 4.5 eq.) and 100 mL toluene are mixed in a 500 mL Schlenk flask . 0.05 mL Karstedt catalyst (2.1 to 2.4% Pt in xylene) is added to this mixture and the mixture is stirred at room temperature for 18 h. The mixture is then heated at 80° C. for 1 h. The mixture is filtered over dried neutral aluminum oxide and the remaining solvent is removed in vacuo. 40.2 g (92%) of the precursor Px2 are obtained as a clear, colorless liquid. 1H NMR: (294K, 500MHz, _{C6 D6} ) d = 0.01 (s, 18H, OSi-( _CH3 ) ₂ ), 0.10 (s, 3H, OSi- _CH3 ) _r 0.67-0.70 (m, 6H, Cl ₃ Si-CH ₂ ), 1.17-1.20 (m, 6H, OSi-CH ₂ ),

¹³ C NMR: (294 K, 125.8 MHz, C ₆ D ₆ ) d = -1.9, -0.6, 9.2, 17.3, 2 ⁹ Si NMR: (294 K, 99.4 MHz, C ₆ D ₆ ) d = - 63.7, 8.5, 13.9. Synthesis example 6.1: Preparation of the precursor Px3 of tri-functional silirene crosslinker V5 (scheme 9).

Scheme 9: Representation of the Px3 precursor.

Tris-trichlorosilane (Px2, 10.0 g, 13.3 mmol, 1 eq.) is mixed with 50 mL of pentane in a 250 mL Schlenk flask. A 1.7 M L-tert-butyl solution in pentane (25.0 mL, 42.5 mmol, 3.2 eq.) is added dropwise over a period of 0.5 h. The reaction was then stirred at room temperature for 4 h and refluxed for a further 2 h. The Li salt formed is filtered off and the filtrate is concentrated in vacuo. 10.1 g (93%) of the precursor Px3 are obtained as colorless crystals. 1H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.17 (s, 18 H, OSi-(CH ₃ ) ₂ ),

0.18 (s, 3H, OSi-CH ₃ ), 0.86-0.92 (m, 6H, Cl ₂ Si-CH ₂ ), 1-03 (s,

27 H, C-CH ₃ ), 1.11-1.15 (m, 6 H, OSi-CH ₂ ),

¹³ C NMR: (294 K, 125.8 MHz, C ₆ D ₆ ) d = -1.7, -0.4, 9.6, 9.8,

22.9, 25.9, ²⁹ Si NMR: (294 K, 99.4 MHz, _{C6 D6} ) d = -63.7, 8.57, 38.5.

Synthesis example 6.2: Preparation of the precursor P3 of trifunctional silirene crosslinker V5 (scheme 10).

Scheme 10: Representation of the precursor P3.

Tris-dichlorosilane (Px3, 9.5 g, 11.6 mmol, 1 eq.) is dissolved in 20 mL THF, cooled to -30 °C, followed by trans-but-2-ene (19.5 g, 348 mmol, 30 eq.) to condense the reaction.

Crushed Li pieces (1.21 g,

232 mmol, 20 eq.) was added and the temperature adjusted to -10°C and stirred for 12 h. The mixture is then warmed to room temperature and stirred for a further 72 h until the starting material has reacted completely. Remaining butene and solvent are removed in vacuo. The crude product is dissolved in pentane and the suspension is filtered. After the product has been dried in vacuo, 3.2 g (36%) of precursor P3 are obtained as a colorless viscous oil.

¹ H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.15 (s, 3 H, OSi-CH ₃ ),

0.24 (s, 18H, OSi-(CH ₃ ) ₂ ), 0.92-0.95 (m, 6H, Si-CH ₂ ),

1.05 (s, 27H, C-CH ₃ ) 1.10-1.13 (m, 6H, Si-CH), 1.23-1.27 (m, 6H, OSi-CH ₂ ), 1.37-1.38 (m, 18H, SiCH-CH ₃ ),

²⁹ Si NMR: (294K, 99.4MHz, _{C6 D6} ) d = -64.1, -49.6, 7.5.

Synthesis example 6.3: Preparation of the precursor Px4 of trifunctional silirene crosslinker V5 (scheme 11).

Scheme 11: Representation of the Px4 precursor.

Tris-trichlorosilane (Px2, 10.0 g, 13.3 mmol, 1 eq.) is mixed with 50 mL of THF in a 250 mL Schlenk flask. To this A solution of potassium hexamethyldisilazide (KHMDS) (8.1 g, 40.5 mmol, 3.1 eq.) dissolved in 20 mL THF is added dropwise to the mixture. The reaction is stirred for 3 h at room temperature and for 1 h at 50°C. The resulting suspension is filtered and the filtrate is then dried in vacuo.

The crude product is redissolved in pentane and filtered again. The pentane is removed in vacuo and 11.8 g (80%) of the precursor Px4 are obtained as clear, colorless crystals. 1H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.19 (s, 18 H, OSi-(CH ₃ ) ₂ ), 0.20 (s, 3 H, OSi-CH ₃ ), 0.35 (s , 54 H, TMS), 0.90-0.94 (m, 6 H, CI ₃ Si-CH ₂ ), 1.29-1.33 (m, 6 H, OSi-CHz),

²⁹ Si NMR: (294K, 99.4MHz, _{C6 D6} ) d = -63.8, 2.2, 6.4, 8.5.

Synthesis example 6.4: Preparation of the precursor P4 of trifunctional silirene crosslinker V5 (scheme 12).

Scheme 12: Representation of the precursor P4.

Tris-dichlorosilane (Px4, 5.0 g, 4.43 mmol, 1 eq.) is dissolved in 10 mL THF, cooled to -30 °C, followed by trans-but-2-ene (7.46 g, 133 mmol, 30 eq.) to condense the reaction. Crushed Li pieces (460 mg,

66.5 mmol, 15 eq.), warmed to -10 °C and stirred for 12 h. The mixture is then stirred at room temperature for a further 72 h until the starting material has reacted. Remaining butene and Solvents are removed in vacuo. The crude product is dissolved in pentane and the suspension is filtered through aluminum oxide and Celite. After drying in vacuo, 1.2 g (25%) of precursor P4 are obtained as a colorless viscous oil. 1H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.09 (s, 3 H, OSi-CH ₃ ),

0.26 (s, 18H, OSi-(CH ₃ ) ₂ ), 0.31 (s, 54H, TMS), 0.62-0.64 (m,

6H, Cl ₃ Si-CH ₂ ) , 0.78-0.84 (m, 6H, Si-CH), 1.00-1.07 (m, 6H, OSi-CH ₂ ) _r 1.40 (s, 18, SiCH-CH ₃ ),

²⁹ Si NMR: (294K, 99.4MHz, _{C6 D6} ) d = -64.1, -41.1, 4.7, 8.0.

Synthesis example 6.5: Preparation of the tri-functional silirene crosslinker V5 (scheme 13).

Scheme 13: Preparation of the silacyclopropene V5.

Bis-silacyclopropane (P3, 150 mg, 194 μmol, 1 eq.) is mixed with l-phenyl-2-trimethylsilyl-acetylene (118 mg, 669 μmol, 3.5 eq.) and 5 mL toluene in a 25 mL Schlenk flask . The mixture is heated to 110° C. and refluxed for 72 h. The solvent and excess acetylene are then removed in vacuo (2*10 ^-2 mbar, 80° C.). 213 mg (71%, 301 μmol) of the Siliren crosslinker V5 are obtained as a colorless oil. 1H NMR: (294 K, 500 MHz, C ₆ D ₆ ) d = 0.24 (s, 27 H, TMS),

0.36 (s, 18 H, OSi-(CH ₃ ) ₂ ), 0.37 (s, 3 H, Si-CH ₃ ), 0.52-0.59 (m, 6 H, Si-CH ₂ ), 0.89-0.96 (m, 6 H, OSi-CH ₂ ), 1.11 (s, 27 H, C-(CH ₃ )3.), 7.08-7.12 (m, 3 H, CH _arom . 7.24-7.27 (m,

6 H, CH _arom . ) , 7.64-7.68 (m, 6H, CH _arom . ) ,

²⁹ Si NMR: (294 K, 99.4 MHz, _{C6 D6} ) d = -72.1, -64.0, -13.7, 7.8. λ _max = 318 nm

Synthesis Example 7: Preparation of tri-functional silirene crosslinker V6 (scheme 14).

Tris-silacyclopropane (P4, 150 mg, 138 μmol, 1 eq.) is mixed with l-phenyl-2-trimethylsilyl-acetylene (84 mg, 484 μmol, 3.5 eq.) and 5 mL toluene in a 25 mL Schlenk flask . The mixture is then heated to 110° C. and refluxed for 72 h. The solvent and excess acetylene are then removed in vacuo (2*10 ⁻² mbar, 80° C.), with 213 mg (71%, 301 μmol) of the Siliren crosslinker V6 being obtained as a yellowish oil.

¹ H NMR: (294 K, 500 MHz , C ₆ D ₆ ) d = 0.24(s, 27 H, TMS ) , 0.29 (s, 3 H, OSi-CH ₃ ) _r 0.31 (s, 27 H, N (TMS ) ₂ ), 0.35 (m, 18H, OSi- ( CH ₃ ) 2 ) , 0.68-0.76 (m, 6H, OSi -CH ₂ , tBu) , 1.17-1.27 (m,

6 H, Si-CH ₂ .), 6.88-6.90 (m, 3 H, CH _arom . ), 6.90-6.93 (m,

6 H, CH _arom . ) , 7.46-7.48 (rn, 6H, CH _arom .. )

²⁹ Si NMR : (294 K, 99.4 MHz , C ₆ D ₆ ) d = -80.8, -64.0, -13.2, 3.4,

8.1. λ _max = 320 nm Synthesis example 8.1: Preparation of P6 as a precursor for a hydrocarbon-based silirene crosslinker V7 (scheme 15). 1,6-bis(trichlorosilyl)hexane (P5) was prepared according to

Procedure according to T. Saiki; Phosphorus, Sulfur, and Silicon and the Related Elements, 2008, 183, 1556-1563.

Scheme 15: Representation of precursor P6 from P5.

10.0 g (28.3 mmol, 1.0 eq.) P5 were placed in 40 ml THF and cooled to 0°C. A solution of 11.3 g (56.7 mmol, 2.0 eq.) of potassium hexamethyldisilazane (KHMDS) in 30 ml of THF is then slowly added dropwise over a period of 30 min. The resulting suspension is for 6 h at

stirred at room temperature. The solvent is then removed in vacuo. The residue is taken up in 40 ml of pentane and then filtered. After removing the solvent again in vacuo, the precursor P6 is obtained (15.4 g; 25.5 mmol; 90%).

²⁹ Si NMR: (294 K, 99.4 MHz, C ₆ D ₆₎ d = 2.0 (Si-Cl ₂₎ , 6.5 (N-Si-

Me ₃ ). Synthesis example 8.2: Preparation of P7 as a precursor for a hydrocarbon-based silirene crosslinker V7 (scheme 16).

Scheme 16: Representation of precursor P7 from P6.

10.0 g (16.6 mmol, 1.0 eq.) P6 are dissolved in 50 ml THF and the reaction mixture is brought to -30°C. Subsequently, an excess of 28.0 g of trans-but-2-ene (497.6 mmol, 30 eq.) is condensed into the reaction vessel and 1.47 g (212 mmol, 15.0 eq.) of lithium-sodium alloy ( 2.5% Na) added in argon countercurrent. The reaction mixture is warmed to room temperature overnight and stirred for 5 days. After the complete reduction of the chlorosilane, the solvent is removed in vacuo and the residue is resuspended in 30 ml of pentane. LiCl which precipitates out is separated off and the product solution is filtered through dried, neutral aluminum oxide. The filtrate is then dried in vacuo to give the bis-silirane functionalized hexane P7 (6.8 g,

11.9 mmol; 72%) to get.

²⁹ Si NMR: (294 K, 99.4 MHz, C ₆ D ₆ ) d = -48.2 (CH-Si-CH), 4.6 (N-

Si TMS).

Synthesis Example 8.3: Preparation of crosslinker V7 from precursor P7 (scheme 17).

Scheme 17: Representation of crosslinker V7 from precursor P7. The precursor P7 (200 mg, 349 μmol, 1 eq.) is heated to 110°C with bis(trimethylsilyl)-acetylene (149 mg, 872 μmol, 2.5 eq.) and 5 ml toluene in a 25 ml Schlenk flask and left for 72 h refluxed. The solvent and excess acetylene are then removed at 2*10 ^-2 mbar and 50°C. 156 mg (56%, 195 μmol) of the Siliren crosslinker V7 are obtained as a colorless oil.

²⁹ Si NMR: (294 K, 99.4 MHz, _{C6 D6} ) d = -85.8, -13.2, 7.5.

Application examples

Application example 1: Crosslinking of hydridomethylsiloxane-dimethylsiloxane copolymer with Siliren crosslinkers C1 to C4 (diagram 18)

Scheme 18: Crosslinking with Siliren crosslinkers V1 to V4.

The silacyclopropene crosslinker Vx (representing V1 to V4) and the silicone oil are mixed in different ratios and homogenized in a vessel that is sufficiently permeable in the intended wavelength range. The photochemical crosslinking takes place by irradiation at 350 nm under a fluorescent tube for 1 hour. For thermal crosslinking, the mixture was stored at 140° C. for 1-2 hours. Application example 2: Crosslinking of H-terminated polydimethylsiloxane with Siliren crosslinkers V1 to V4 (Scheme 19)

Scheme 19: Crosslinking with Siliren crosslinkers V1 to V4.

The implementation is analogous to application example 1.

Application example 3: Crosslinking of OH-terminated polydimethylsiloxane with Siliren crosslinkers V1 to V4 (Scheme 20)

Scheme 20: Crosslinking with Siliren crosslinkers V1 to V4.

The procedure is analogous to application example 1. Application example 4: Crosslinking of hydridomethylsiloxane-dimethylsiloxane copolymer with Siliren crosslinkers C5 and C6 (diagram 21)

Scheme 21: Crosslinking with Siliren crosslinkers V5 and V6.

Silacyclopropene crosslinker Vx (V5 or V6, 14 μmol each) and the silicone oil in the ratios R = 1, 2, or 3 (R = [number of siliren units]/[ Number functional group silicone oil]) mixed and homogenized. Crosslinking takes place by irradiation at 350 nm under a fluorescent tube for 2 hours. For thermal crosslinking, the mixture was stored at 140° C. for 1-2 hours.

Application example 5: Crosslinking of H-terminated polydimethylsiloxane with Siliren crosslinkers V5 and V6 (Scheme 22)

( ) ₂

Scheme 22: Crosslinking with Siliren crosslinkers V5 and V6.

The procedure is analogous to application example 4. Application example 6: Crosslinking of OH-terminated polydimethylsiloxane with Siliren crosslinkers V5 and V6 (Scheme 23)

Scheme 23: Crosslinking with Siliren crosslinkers V5 and V6.

The implementation is analogous to application example 4.

In order to demonstrate the crosslinking method according to the mechanism described, the feasibility in principle was tested on monofunctional silacyclopropene compounds with various H-silanes (triethylsilane and pentamethyldisiloxane) in model reactions. Due to the insolubility of the crosslinked polyorganosiloxanes, analysis of the crosslinking mechanism, in particular by means of NMR analysis, is difficult or impossible. The advantage of this simplified method lies in a clear analysis, which becomes visible in the following examples with monofunctional silirenes. Due to the structural and chemical similarity of the compounds used, the properties and results can be transferred to the multifunctional silacylopropene crosslinkers. Analysis Example 1 Detection of the reaction products from silirene compound 7c and silane model compound triethylsilane by means of ¹ H and ²⁹ Si NMR (scheme 24).

Scheme 24: Model reaction of silacyclopropene 7c with triethylsilane.

The reaction between 4 eq. Triethylsilane and 7c is irradiated in C6D12 in a sealed J.Young NMR tube at 350 nm for 1 h. Triethylsilane acts as a scavenger for the silylene formed by the irradiation. By comparison of the NMR spectra before and after irradiation, as well as by a thermal control reaction, it can be shown that the reaction takes place according to Scheme 23. A rearrangement reaction of silirene, which is known from the literature, occurs as a side reaction. This can be greatly reduced by modifying the substituents (cf. analysis example 2).

Figure 1 shows ²⁹ Si NMR spectra (in C ₆ D ₁₂ ) of the reaction mixture of triethylsilane and the silacyclopropene 7c after thermal treatment (diagram a (top)) and after photochemical irradiation (diagram b (middle)) . The spectrum of the cleavage product bis-(TMS)-acetylene 9c (diagram c (bottom)) is also shown.

From the comparison of the ²⁹ Si-NMR (Fig. 1) it is clear that in the thermal control reaction (140 ° C for 3 h) under Exclusion of light has resulted in no reaction (diagram a). Diagram b (photoactivation at 350 nm) shows that the silacyclopropene signal is no longer present at -86.5 and -13.1 ppm (complete conversion of the silacyclopropene). At the same time, the insertion product 8a (see Scheme 24) was formed with a chemical shift of -8.1 and -6.2 ppm. Further confirmation of the proposed course of the reaction can be seen in the formation of bis-(TMS)-acetylene 9c at -19.5 ppm. This indicates the formation of the corresponding silylene as a reactive intermediate. The lower diagram c shows the NMR spectrum of bis (TMS) - acetylene. The remaining three signals at -14.6, -18.7, and -19.8 ppm in diagram b belong to the rearrangement product 9c mentioned. Although the rearrangement is a competitive reaction (ratio 8a/9c = 34/66) during the irradiation, the occurrence does not hinder crosslinking and can be severely restricted by choosing suitable substituents on the silirene compound (see analysis example 2). or even prevented altogether. The signal at 0.0 ppm is due to triethylsilane, since this was added in excess (4 eq.).

The comparison of the ¹ H-NMR spectra of the thermal control reaction (top spectrum) and the photoreaction (bottom spectrum) as shown in FIG. 2 also supports the proposed course of the reaction.

The shift of the Si-H signal of triethylsilane from 3.88 ppm to 3.68 ppm in the insertion product 8a is particularly striking. This upfield shift occurs due to the changed chemical environment of the newly formed Si-H bond. Furthermore, the previous findings can be linked by means of 2D-NMR spectroscopy ( ¹ H- ²⁹ Si-HMBC (Heteronuclear Multiple Bond Correlation)).

Figure 3 shows the ¹ H- ²⁹ Si HMBC NMR spectrum of the reaction according to Scheme 24 ( ²⁹ Si = vertical, ¹ H = horizontal). It becomes clear that the signals described above are coupled. This proves that the newly formed proton signal at 3.68 ppm (the newly formed Si-H bond) belongs to the two silicon signals of the insertion product 8a (dashed lines).

The proposed mechanism of the light-induced reaction of the silacyclopropene via the formation of a silylene and subsequent insertion reaction with the trapping agent triethylsilane is therefore plausible. The basic feasibility of the networking principle is confirmed.

Analysis Example 2 Detection of the reaction products from silirene compound 7d and silane model compound triethylsilane by means of ¹ H and ²⁹ Si NMR (scheme 25).

Scheme 25: Model reaction of silacyclopropene 7d with triethylsilane.

This second analytical example confirms the proposed reaction pathway based on the reaction of silacyclopropene 7d in combination with 4 eq. triethylsilane. The implementation takes place in analogy to analysis example 2. The same insertion product 8a is formed, since the elimination of the corresponding acetylene results in the same silylene fragment. However, the rearrangement product 9a differs structurally, since a TMS functionality is replaced by phenyl.

The selectivity can be controlled by the choice of acetylene used. Here the insertion reaction, with a relative proportion of 71%, is clearly preferred to the rearrangement reaction. The products can again be compared very clearly using their ²⁹ Si NMR spectra.

FIG. 4 shows the ²⁹ Si NMR spectra of the reaction mixture of triethylsilane and the silacyclopropene 7d after thermal treatment (top diagram) and after photochemical irradiation (bottom diagram). In the case of thermal treatment (3 h at 140° C.) there is no reaction here either. However, the photoreaction (350 nm for 1 h) leads to complete conversion of the silacyclopropene 7d with the corresponding signals at -72.2 and -14.0 ppm. The insertion product 8a can be recognized by the signals at -8.1 and -6.2 ppm, the acetylene (l-phenyl-2-triethylsilyl-acetylene) by a shift of -18.4 ppm.

FIG. 5 shows the ¹ H NMR spectrum of the thermal control reaction (top) and the ¹ H NMR spectrum of the photoreaction (bottom). As in the first analytical example, the comparison of the ¹ H-NMR spectra shows that a new Si-H signal is formed at 3.68 ppm (photo reaction below). Analysis Example 3 Detection of the reaction products from silirene compound 7d and siloxane model compound pentamethyldisiloxane by means of ¹ H, ²⁹ Si NMR (scheme 26).

Scheme 26: Model reaction of silacyclopropene 7d with pentamethyldisiloxane.

Based on this analytical example, the transferability of the reaction principle to polysiloxanes should be checked by using small, model siloxane compounds. For this purpose, pentamethyldisiloxane (Me ₃ SiOSiMe ₂ H) was reacted with the Siliren 7d, the procedure being carried out analogously to the preceding analytical examples.

FIG. 6 shows the ²⁹ Si NMR spectrum (top) and the ¹ H NMR spectrum (in C ₆ D ₁₂ , bottom) of the reaction mixture of pentamethyldisiloxane and the silacyclopropene 7d after photochemical irradiation.

Here, too, it could be shown that the expected insertion product 8b was formed after irradiating the reaction mixture at 350 nm for one hour. The chemical shift in the ²⁹ Si NMR at 8.4, 5.5 and -6.6 ppm for the insertion product 8b matches the values known from the literature. The formation of l-phenyl-2-trimethyl-sily-acetylene at -18.4 ppm and the corresponding rearrangement product 9d (cf. also analysis example 2) can also be seen. The proton signal in the ¹ H-NMR is slightly upfield at 3.59 ppm shifted compared to the Si-H signal of the insertion product 8a (3.68 ppm). This small shift speaks for a very similar chemical environment as is the case for the comparison between 8a and 8b. At the same time, however, the difference shows the effect that the different structures have on the proton (Si-H). A distribution of the reaction products of 70% (8b) to 30% (9d) could be determined, which corresponds to the ratio of analysis example 2.

The reaction according to Scheme 26 represents an even better model due to the chemical similarity of the pentamethyldisiloxane used to a polysiloxane. On the basis of this model reaction, the reaction mechanism can very probably also be transferred to long-chain hydridomethylpolysiloxanes.

Investigations on the adhesion promotion of silane-containing siloxanes in photochemically and thermally crosslinked RTV2

crowds

To produce the RTV2 silicone masses, the respective components are mixed together in the following mass ratios (e.g. with a "DAC-150.1" speed mixer from Hausschild):

- SEMICOSIL® 912 : ELÄSTOSIL® CAT UV = 10 : 1

- ELASTOSIL® RT604 A : B = 1 : 1.

The components mentioned are commercially available from Wacker Chemie AG. a) For the additives, 1, 5 and 10% by weight of the Siliren-functionalized siloxane V6 are added and mixed with the RTV2 composition by hand or using a speed mixer. b) Polypropylene specimens were primed with a 10% by weight solution of C6 in pentane, which evaporates rapidly at room temperature.

A UV chamber "UVA cube" from Dr. Hönle (illuminance: 200 mW/cm ² ) was used to activate adhesion promoter and/or RTV2 mass. The mixtures were thermally cured in an "LHT6/30" drying cabinet. from Carbolite-Gero.

The amounts used in each case and all the crosslinking conditions can be found in Tables 1 (photochemical crosslinking) and Table 2 (thermal crosslinking). Peel stability was tested and evaluated by peeling off the crosslinked silicone coating. Could as the reference could be released in one piece without tearing, there was no improvement in adhesion. If the material tore because it stuck particularly firmly to the carrier material and had to be removed piecemeal, the adhesion was rated as better than the reference.

Table 1: Evaluation of the adhesion of photochemically crosslinking RTV2 mass (SEMICOSIL® 912 UV) with and without adhesion promoter containing Siliren; no improvement in adhesion = o; Improvement in adhesion = +.

Table 2: Evaluation of the adhesion of thermally crosslinking RTV2 compound (ELASTOSIL® RT604) with and without adhesion promoter containing Siliren; no improvement in adhesion = o; Improvement in adhesion = +.

Claims

patent claims

1. Silirene-functionalized compounds consisting of a substrate to which are attached at least two silirene groups of formula (I)

(I) are covalently bonded, where n = 0 or 1; wherein R is a C ₁ -C ₂₀ divalent hydrocarbon radical; where R ¹ is selected from the group consisting of (i) C1-C ₂₀ hydrocarbyl, (ii) C ₁ -C ₂₀ hydrocarbyl oxy radical, (iii) silyl radical -SiR ⁴ R ⁵ R ⁶ , wherein R ⁴ , R ⁵ , R ⁶ are independently C ₁ -Ce hydrocarbyl, (iv) amine residue -NR ^Y ₂ , where R ^y is independently selected from the group consisting of (iv.i) hydrogen, (iv.ii) C ₁ -C ₂₀ -hydrocarbon radical and

(iv.iii) silyl radical -SiR ⁴ R ⁵ R ⁶ , and (v) imine radical -N=CR ⁷ R ⁸ where R ⁷ , R ⁸ are independently selected from the group consisting of hydrogen, C ₁ -C ₂₀ hydrocarbon radical and silyl residue

^{-SiR4 R5 R6} ; where R ² , R ³ are independently selected from the group consisting of hydrogen, halogen, C ₁ -C ₂₀ hydrocarbon radical, silyl radical -SiR ⁴ R ⁵ R ⁶ and organopolysiloxane radical -(CH ₂ ) _y -[SiR ⁹ R ¹⁰ -O] _x -[SiR ¹¹ R ¹² R ¹³ ], wherein R ⁹ to R ¹³ are independently selected from the group consisting of methyl, ethyl, phenyl, hydrogen, ethynyl and vinyl, where the index x is zero or an integer value of 1 to 200 and the index y is zero or an integer value is from 1 to 10, and where R ² and R ³ can be part of a cyclic radical.

2. Silirene-functionalized compounds according to claim 1, characterized in that the substrate is selected from the group consisting of organosilicon compounds, silicic acids, hydrocarbons, carbon-based oligomers and polymers.

3. Silirene-functionalized compound according to claim 2, characterized in that the substrate is selected from the group consisting of silanes, siloxanes, precipitated silica, fumed silica, polyolefins, acrylates, polyacrylates, polyvinyl acetates,

polyurethanes and polyethers.

4. Silirene-functionalized compound according to one of the preceding claims, characterized in that the substrate is an organosilicon compound of the general formula (II).

(SiO _4/2 ) a (R ^x Si0 _3/2 ) b (R 'Si0 _3/2 ) b' (R ^x ₂ Si0 _2/2 ) _c (R ^X R 'Si0 _2/2 ) c'

(R ' ₂ Si0 _2/2 ) _cn (R ^x ₃ SiO _1/2 ) _d (R 'R ^x ₂ SiO _1/2 ) _d ' (R ' ₂ R ^x SiO _1/2 ) _d ''' (R ' ₃ SiO _1/2 ) _d '" (II) where R ^x is independently selected from the group consisting of hydrogen, halogen, unsubstituted or substituted C ₁ -C ₂₀ hydrocarbyl and unsubstituted or substituted C ₁ -C ₂₀ hydrocarbyl oxy radical; where the indices a, b, b', c, c', c'', d, d', d'', d''' indicate the number of the respective siloxane unit in the compound and independently zero or are an integer from 1 to 100,000, with the proviso that the sum of a, b, b', c, c', c'', d, d', d'', d''' is at least 2 and at least one of the indices b', c', d'> 2 or at least one of the indices c'', d'' or d''' is non-zero; and wherein R' is the silirene group of formula (I).

5. Silirene-functionalized compounds according to claim 4, characterized in that the indices a, b, b', c, c', c'', d, d'' and d''' are zero and the index d' is den takes value 2; where in formula (I) the index n has the value 1, R is a C ₁ -C3 alkylene radical and R ¹ is a C ₁ -C ₆ hydrocarbon radical, a silyl radical -SiR ⁴ R ⁵ R ⁶ or an amine radical - N is (SiR ⁴ R ⁵ R ⁶ )2 wherein R ⁴ , R ⁵ , R ⁶ are independently C ₁ -C ₆ hydrocarbyl radicals; and where R ² , R ³ are independently selected from the group consisting of hydrogen, halogen, C ₁ -C ₂₀ hydrocarbon radical, silyl radical -SiR ⁴ R ⁵ R ⁶ and

Organopolysiloxane radical -(CH ₂ ) _y -[SiR ⁹ R ¹⁰ -O] _x -[SiR ¹¹ R ¹² R ¹³ ], where the index x is zero or an integer value from 1 to 100 and the index y is zero or an integer value is from 1 to 8, and wherein R ⁹ to R ¹³ are independently methyl, phenyl, hydrogen or vinyl radicals.

6. Silirene-functionalized compounds according to claim 4, characterized in that the indices a, b, b', c, c', c'', d, d'' and d''' are zero and the index d' is den takes value 2; where in formula (I) the index n has the value 1, R is an ethylene radical and R ¹ is a C ₁ -C ₆ alkyl radical, an amine radical -N(SiMe3) ₂ or a silyl radical -SiR ⁴ R ⁵ R ⁶ , where R ⁴ , R ⁵ , R ⁶ are independently C ₁ -C ₆ hydrocarbyl; and wherein R ² , R ³ are independently selected from the group consisting of hydrogen, C ₁ -C ₂₀ hydrocarbon radical, silyl radical -SiR ⁴ R ⁵ R ⁶ and organopolysiloxane radical -(CH ₂ ) _y -[SiR ⁹ R ¹⁰ -O] _x -[SiR ¹¹ R ¹² R ¹³ ], where the index x is zero or an integer from 1 to 50 and the index y is zero or an integer from 1 to 4, and where R ⁹ to R ¹³ are independent from one another are methyl, hydrogen or vinyl radicals.

7. Process for the preparation of silirane-containing compounds, in particular according to at least one of claims 1 to 6, characterized in that a silirane-containing precursor with an alkyne of the general formula R ² -C

CR ³ is reacted in an organic solvent in the temperature range from 100 to 150° C. or with the addition of silver triflate in the temperature range from 50 to 120° C., where R ² , R ³ are independently selected from the group with hydrogen, halogen, C ₁ -C ₂₀ -hydrocarbon radical, silyl radical -SiR ⁴ R ⁵ R ⁶ , in which R ⁴ , R ⁵ , R ⁶ are independently a C ₁ -C ₆ -hydrocarbon radical, and organopolysiloxane radical -(CH ₂ ) _Y -[SiR ⁹ R ¹⁰ -O] _x -[SiR ¹¹ R ¹² R ¹³ ], wherein R ⁹ to R ¹³ are independently selected from the group consisting of methyl, ethyl, phenyl, ethynyl and vinyl, where the index x is zero or an integer value of 1 to 200 and the index y is zero or an integer value from 1 to 10, and where R ² and R ³ can be part of a cyclic radical.

8. Mixture containing a) at least one silirene-functionalized compound according to any one of claims 1-6; and b) at least one compound A which has at least two radicals R ¹⁴ , where the radicals R ¹⁴ are independently selected from the group with (i) -Si-H, (ii) -OH, (iii) -C _x H _2x -OH where x is an integer ranging from 1 to 20, (iv) -C _x H _2x -NH ₂ where x is an integer ranging from 1 to 20, (v) -SH, (vi ) - R ¹⁵ n-CR ¹⁷ =CR ¹⁸ ₂ and (vii) -R ¹⁵ _n -CR ¹⁹ =0, where R ¹⁵ is a C ₁ -C ₂₀ divalent hydrocarbon radical, n = 0 or 1 and the radicals R ¹⁷ to R ¹⁹ are independently hydrogen or C ₁ -C ₆ hydrocarbyl.

9. Mixture according to claim 8, wherein the compound A is selected from functionalized siloxanes of the general formula (III)

(S1O4 _/2 )a(R ^x Si0 _3/2 ) _b (R'Si0 _3/2 ) _b' (R ^x ₂ Si0 _2/2 ) _c (R ^x R'Si02 _/2 ) _c'

(R '2S1O2 _/2 ) _c" (R ^x ₃ SiO _1/2 ) _d (R 'R ^x ₂ SiO _1/2 ) _d' (R ' ₂ R ^x SiO _1/2 ) _d''

(R ' ₃ SiO _1/2 ) _d"' (III), wherein R ^x is independently selected from the group consisting of halogen, unsubstituted and substituted C ₁ -C ₂₀ hydrocarbyl; wherein R ' is independently selected from the group with (i) hydrogen, (ii) -OH, (iii) -C _x H _2x -OH where x is an integer in the range 1-20, (iv) -C _x H _2X -NH ₂ where x is an integer in the range 1 - 20, (v) - SH , (vi) -R ¹⁵ _n -CR ¹⁷ =CR ¹⁸ ₂ and (vii)

-R ¹⁵ "-CR ¹⁹ =0, where R ¹⁵ is a divalent C ₁ -C ₂₀ hydrocarbon radical, n=0 or 1 and the radicals R ¹⁷ to R ¹⁹ are independently hydrogen or C ₁ -C ₆ carbons - hydrogen residue; where the subscripts a, b, b', c, c', c'', d, d', d'', d''' indicate the number of the respective siloxane unit in the compound and independently of one another an integer in the range of 0 to 100,000, with the proviso that the sum of a, b, b', c, c', c'', d, d', d'', d''' is at least 2 and at least one of the indices b', c', d' ≥ 2 or at least one of the indices c'', d'' or d''' is not equal to 0.

10. The mixture according to claim 9, wherein the molar ratio of silirene groups to functional groups in the siloxane is in a range from 5:1 to 1:5.

11. Mixtures containing a) at least one silane-containing compound according to any one of claims 1 to 6, and b) at least one polymer selected from the group consisting of addition-crosslinking silicone compositions, condensation-crosslinking silicone compositions, silyl-terminated polymers, inorganic polymers and organic polymers .

12. Shaped body containing a mixture according to at least one of claims 8 to 11 and a slightly polar to non-polar carrier material.

13. Shaped body according to claim 12, wherein the carrier material comprises at least one synthetic hydrocarbon polymer selected from the group consisting of polyolefin of mono- or polyenes, polyhaloolefin, polyether, polyvinyl chloride, polyvinylidene difluoride, polytetrafluoroethene, polycarbonate, polyester and copolymers thereof.

14. A process for preparing siloxanes, comprising the steps

- providing a mixture according to any one of claims 8 to 11, and

- Reacting the mixture by thermal, photochemical or catalytic activation.

15. The method according to claim 14, characterized in that the mixture is reacted by thermal activation, the temperature being in a range from 0°C to 200°C, preferably from 10 to 180°C, particularly preferably from 15 to 150°C C, lies.

16. The method according to claim 14 or 15, characterized in that the thermal activation takes place in two stages, comprising the steps:

- setting a temperature T1 in a range from 0°C to 140°C, and

- setting a temperature T2 in a range from 120°C to 180°C; where T1 < T2.

17. The method according to claim 14, characterized in that the mixture is reacted by a single- or multi-stage photochemical activation with actinic radiation in a wavelength range of 300 to 800 nm, preferably 300 to 500 nm, particularly preferably 300 to 400 nm.