DE102007051516B4 - Process for the preparation of hydrogen-rich cyclosiloxanes - Google Patents

Abstract

A process for the preparation of cyclosiloxanes of the type where n is an integer selected from 1, 2 and 3, by reacting: a.) A halosilane of the type H2SiCl2 with 1.5 to 4 molar equivalents of a cyclic amine B, wherein the dihalosilane with b) a salt of a metal from the 1st or 2nd main group or 2nd subgroup of the Periodic Table of the Elements or copper (II) salts or a mixture of these salts, wherein the anion of the Metal salt is carbonate or bicarbonate and the salts contain less than 1% water and less than 1% hydroxide contaminants, the total reaction mixture containing less than 1% water, wherein the cyclic amine B is selected from pyridine, pyrimidine, pyrazine, and / or substituted pyridinines, pyrimidines and pyrazines, wherein the dihalosilane is first mixed with the cyclic amine to form the 1: 2 complexed dichlorosilane before the metal salt is added.

Description

The present invention relates to a process for the targeted synthesis of hydrogen-rich cyclosiloxanes of the type (H ₂ SiO) _n . These compounds may, for. B. as an additive for sealing and curing agents, as SiO ₂ precursors or as a hydrogenating application.

Hydrogen-rich cyclosiloxanes have hitherto been studied primarily on the basis of calculations. From ab initio calculations, for small cycles - (H ₂ SiO) _n with n = 3, 4, 5 - the crystal structure data and thus the symmetry of the compounds could be predicted (T. Kudo, F. Hashimoto, MS Gordon, Journal of Computational Chemistry 17 (1996) 1163).

The first hydrogen-rich cyclosiloxanes of the type (H ₂ SiO) _n were already used in the work of Stock et al. from 1919 and referred to as "prosiloxane" (A. Stock, C. Somieski, Ber. Dtsch. Chem. Ges. 52 (1919) 695).

In the following decades, there was probably very little research in this area due to the high reactivity of the unsubstituted cyclosiloxanes. H ₂ SiO formed in the gas phase from dichlorosilane and water polymerizes only slowly. In the liquid phase, polycondensates are formed from dichlorosilane and water.

DE 1214 876 B with filing date from the year 1963 discloses exclusively the production of linear organopolysiloxanes.

US 5,334,688 ) discloses a process for the synthesis of organo-substituted cyclic polysiloxanes. The process comprises at least 2 steps. Cl ₂ HSiR is first reacted with the unsaturated R 'in the presence of a hydrolyzing catalyst (a platinum-divinyl complex - see examples) to RCl ₂ SiR', which is then cyclized. The process is limited to fully organo-substituted cyclic polysiloxanes.

Also GB 1,213,404 ) discloses a process for the polymerization of organo-substituted cyclic trisiloxanes to linear organopolysiloxanes. ZnO is used as a catalyst for the ring-opening polymerization.

The silicon-hydrogen bond is unstable against bases, but also against strong acids at pH <1 (see US Pat. No. 2,810,628 ). This often leads to a higher cross-linking of the siloxane by T units in the synthesis of cyclosiloxanes. To prevent this, various techniques can be used (D. Seyferth, C. Prud'Homme, GH Wiseman, Inorg. Chem. 22 (1983) 2163).

According to US Pat. No. 2,810,628 results in the H ₂ SiCl ₂ hydrolysis using a mixture of a non-protic solvent (eg. as hexane or diethyl ether) and small amounts of water, a confusing product mixture, the siloxane rings (H ₂ SiO) _n with n = 4-23 contains , In addition, due to the formation of hydrogen chloride, more highly condensed ring systems and insoluble residues are formed (equation (1)):

The cyclic tetramer (H ₂ SiO) ₄ , the pentamer (H ₂ SiO) ₅ and the hexamer (H ₂ SiO) ₆ were detected as major products in the reaction of dichlorosilane with aqueous solvents (D. Seyferth, C. Prud'Homme, Inorg. Chem. 23 (1984) 4412).

Seyferth and coworkers attempted the "controlled" hydrolysis of dichlorosilane with hydratwasserhaltigem nickel chloride (NiCl ₂ · 6H ₂ O) in hexane, but without success in terms of (the narrowing of the product spectrum D. Seyferth, C. Prud'Homme, GH Wiseman, Inorg Chem. 22 (1983) 2163).

SU 556158 discloses a process for the preparation of cyclosiloxanes with organic radicals (organocyclosiloxanes) that can be used to obtain synthetic rubber.

The starting materials used are diorganodichlorosilanes of the general structure R ₂ SiCl ₂ or organodichlorosilanes of the general structure RHSiCl ₂ , with pure organic radical, such as, for example, methyl, phenyl or dichlorophenyl. These can be reacted with sodium or potassium bicarbonate (1 molar equivalent) and pyridine (1 molar equivalent) to (di) organocyclosiloxanes.

For this purpose, first pyridine and metal hydrogen carbonate are stirred in a suitable solvent (eg acetone, ethyl acetate, hexane or toluene). This solution is then added dropwise to a solution of the respective (di) organosilane in the same solvent and stirred for 1 to 5 h at 18 to 25 ° C.

The present invention is a further improved process for the preparation of hydrogen-rich cyclosiloxanes.

Ebsworth et al. describe in J. Chem. Soc. A, 1966, 1508-1514 adducts formed between halosilanes and organic amine bases. They refer to the stoichiometry and mention, inter alia, that SiH ₂ Cl ₂ forms 1: 2 adducts with pyridine, which are present as solid salts.

wobei n eine ganze Zahl gleich oder kleiner 3 ist und bevorzugt ausgewählt aus 1, 2 und 3 ist, durch Umsetzen:

• a) eines Halogensilans des Typs H₂SiCl2 mit mit 1,5 bis 4 Moläquivalenten eines cyclischen Amins B, wobei das Dihalogensilan mit dem cyclischen Amin Verbindungen des Typs H₂SiCl₂·2B bildet, mit b) einem Salz eines Metalls aus der 1. oder 2. Hauptgruppe (Gruppe 1 oder 2) oder aus der 1. oder 2. Nebengruppe (Gruppe 11 oder 12) des Periodensystems der Elemente oder einer Mischung dieser Salze,

wobei das Anion des Metallsalzes Carbonat oder Hydrogencarbonat ist und die Salze unter 1% Wasser und unter 1% Hydroxidverunreingungen enthalten,
wobei die gesamte Reaktionsmischung unter 1% Wasser enthält,
wobei das cyclische Amin B ausgewählt ist aus Pyridin, Pyrimidin, Pyrazin, und/oder substituierten Pyridininen, Pyrimidinen und Pyrazinen
wobei das Halogensilan zunächst mit dem cyclischen Amin vermischt wird, bevor das Metallsalz zugesetzt wird.The object is achieved according to the invention by a process for the preparation of hydrogen-rich cyclosiloxanes of the type

where n is an integer equal to or less than 3 and is preferably selected from 1, 2 and 3, by reacting:

• a) a halogenosilane of the type H ₂ SiCl ₂ having from 1.5 to 4 molar equivalents of a cyclic amine B, wherein the dihalosilane with the cyclic amine forms compounds of the type H ₂ SiCl _2. 2B, with b) a salt of a metal from the 1 or 2nd main group (group 1 or 2) or from the 1st or 2nd subgroup (group 11 or 12) of the Periodic Table of the Elements or a mixture of these salts,

wherein the anion of the metal salt is carbonate or bicarbonate and the salts contain less than 1% water and less than 1% hydroxide contaminants,
wherein the total reaction mixture contains less than 1% water,
wherein the cyclic amine B is selected from pyridine, pyrimidine, pyrazine, and / or substituted pyridinines, pyrimidines and pyrazines
wherein the halosilane is first mixed with the cyclic amine before the metal salt is added.

The process according to the invention is advantageously a one-step process, requires no additions of catalysts and leads selectively to hydrogen-rich (unsubstituted or monosubstituted) cyclosiloxanes.

The ring size is advantageously adjustable to n = 3, 4, 5, 6 (in particular n = 4 to 6), so that larger rings are not formed. Furthermore, there is the possibility of producing defined hydrogen-rich polysiloxane molecules by a gentle ring-opening polymerization.

Preferably, the halosilane is first mixed with the cyclic amine and then contacted with the metal salt. Mixing with the amine forms a bis-adduct of the type H ₂ SiCl _2. 2B, where B stands for the amine base.

In order to start the halosilane hydrolysis in practice, already a low concentration of protons is sufficient. The hydrolysis is advantageously controlled by the metal salt. This contains catalytic amounts of water and thus provides the necessary protons. In addition to its function as a controlled water and oxygen donor, it serves in part as a scavenger of hydrogen chloride to form the corresponding metal chlorides, see also equation (2)

In equation (2), the process is explained in more detail by way of example with reference to the bis adduct H ₂ SiX _2. 2B with X = Cl and the preferred carbonates of the metals Li (z = 2), Ca and Zn (z = 1):

Due to the slow formation of the corresponding metal chlorides, the hydrogen chloride formed is trapped by means of a cyclic amine B, particularly preferably a pyridine base of the type PyR (with R = hydrogen, alkyl or halogen).

According to the invention, the cyclic amine B is selected from pyridine or substituted pyridines, e.g. B. selected from the group of alkyl- or halogen-substituted pyridines, such as. As the picolines (2-methyl, 3-methyl, 4-methyl-pyridine), the lutidines (2,3-, 2,4-, 2,5-, 3,4-, and 3,5- Dimethyl pyridine), the collidines (2,3,5- and 2,3,6-tri-methylpyridine), or corresponding ethyl, propyl, t-butyl, pentyl, hexyl, vinyl, phenyl, pyridyl, , Naphthyl, cyclohexyl (e.g., 4-t-butyl or 4-vinylpyridine), the bromine-substituted pyridines, and the dialkyl-amine-substituted pyridines, such as. For example, 4-dimethylamino-pyridine or 4-diethylamino-pyridine or pyrimidine or pyrazine or an appropriately substituted pyrimidine or pyrazine, pyridines, pyrimidines or pyrazines in the 2 and 6-position (ie, for example, 2,6-lutidine and 2,4,6-collidine) are less preferred because they lead to dismutation of the dichlorosilane and do not form more highly coordinated compounds. The type and site of substitution on pyridine, pyrimidine or pyrazine is otherwise not critical to the reaction.

Such a complex of amine and dihalosilane (here pyridine and dichlorosilane) has, for example, the following structure:

By coordination with 2 molecules of cyclic amine, here pyridine, the silicon-halogen bond is extended, d. H. the reactivity of this bond increases.

The dichlorosilane forms 1: 2 complexes with the aromatic amine (one molecule of dichlorosilane, and 2 molecules of an aromatic amine, such as pyridine). For the reaction, it is less of interest whether the aromatic amine is pyridine, methyl, ethyl, t-butyl, vinyl, dimethylamino or a halo-pyridine or a correspondingly substituted pyrimidine or pyrazine. For the reaction, the presence of reactive silicon-halogen bonds is crucial.

In order to obtain a large number of 1: 2 complexes, the aromatic amine is used according to the invention with 1.5 to 4, more preferably 2 to 3 molar equivalents (based on the dihalosilane).

These higher coordinated compounds can be prepared directly from the dichlorosilane, and the aromatic amine, such as. As substituted pyridines, are generated and then used directly for the synthesis of cyclosiloxanes, a purification of the higher-coordinated products is not required.

In contrast to the dichlorosilane which is gaseous at room temperature, these higher-coordinated compounds are liquid at room temperature. The higher-coordinated compounds of the HRSiCl ₂ · 2B type can therefore be metered much easier. The reaction is thereby considerably simplified. A further advantage is that the compounds of the type H ₂ SiCl ₂ · B, in contrast to the compounds H ₂ SiCl ₂ are storable at room temperature.

The amines used as auxiliary bases advantageously catch the resulting hydrogen chloride and thereby cause an equilibrium shift in the direction of the desired product. The organylammonium chloride formed as a by-product from the auxiliary base and hydrogen chloride can advantageously be readily separated from the solution as a solid.

The reaction can be carried out advantageously by using the higher-coordinated compounds at room temperature or higher temperatures. Low temperatures, however, support the formation of small rings. The synthesis is preferably carried out at a temperature of -80 to + 40 ° C, preferably -70 to + 10 ° C, more preferably -70 ° C to + 5 ° C. Especially with small rings (n = 3 to 6, in particular n = 3), the temperature is chosen below 10 ° C, preferably -70 to -0 ° C. Since the reaction is exothermic, the reaction mixture is cooled to the appropriate temperature, preferably with an ice bath or an alcohol / dry ice mixture.

The amine preferably has a maximum water content of less than 0.1%, particularly preferably less than 0.01%. Influencing factors used according to the invention for controlling hydrolysis with metal salts and aromatic amines are the type of metal ions used, the anions used and the proportion of chemically and physically bound water in the metal salt, the ability of the aromatic amine to intercept the hydrogen chloride and the properties of the organic solvent used, in particular the polarity.

In addition to the amine, another solvent is preferably used in the reaction. Preferred solvents are aprotic solvents, particularly preferably toluene, n-hexane, n-pentane, petroleum ether, tetrahydrofuran, dioxane, ethyl acetate and glyme, and mixtures of these solvents. To avoid side reactions, the solvent is preferably anhydrous and preferably has a maximum water content of less than 0.1%, more preferably less than 0.01%. Particularly good results were obtained with aprotic, nonpolar solvents, in particular n-hexane, toluene, cyclohexane, n-pentane and n-heptane. In the more polar aprotic solvents such. As ethyl acetate and THF it comes to the formation of larger cycles with n> 6.

As cations of the metal salts are lithium, copper (II) - and metal ions of a metal from the 2nd main group (group 2 or IIa) or 2nd subgroup (group 12 or IIb) of the Periodic Table of the Elements, such as. As Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Zn ²⁺ , Cd ²⁺ , preferred. Particularly preferred are Li ⁺ , Zn ²⁺ and Ca ²⁺ . Somewhat less preferred are Na ⁺ , K ⁺ , Mg ²⁺ and Cu ²⁺ .

According to the invention, anions of the metal salts are bicarbonate and carbonate ions. These decompose on exposure to protons to water and gaseous carbon dioxide. By the escape of the carbon dioxide, the equilibrium of the reaction is advantageously shifted to the product side.

The process is carried out under near anhydrous conditions. Thus the metal salts used, particularly carbonates and bicarbonates are as anhydrous as possible below 1%, preferably below 0.1% H ₂ O) and as free as possible of Hydroxidverunreinigungen below 1%, preferably below 0.1%).

The entire reaction mixture, which contains dichlorosilane and aromatic amine (or H ₂ SiCl _2. 2B), as well as metal salt and solvent, is thus virtually anhydrous and according to the invention has a maximum water content of less than 1%, preferably less than 0.1%.

The selected metal salts advantageously have limited basicity and contain hard metal ions which exert a template effect in the hydrolysis / condensation process of the dihalosilane. The salts are also redox-stable with respect to the silicon-hydrogen bond of the siloxane rings.

In apolar solvents are particularly suitable calcium, lithium and zinc carbonate for hydrolysis. When using basic, hydrous magnesium hydroxide carbonate (4 MgCO _3. Mg (OH) ₂ .5H ₂ O - often referred to as basic magnesium carbonate) and the more basic sodium carbonate, undesirable side reactions occur. The too basic action of the latter salts causes an undesirable nucleophilic attack on the silicon-hydrogen bonds. However, the use of pure, hydroxide-free magnesium carbonate, potassium bicarbonate and sodium bicarbonate is possible.

According to the invention, dichlorosilane H ₂ SiCl ₂ or the corresponding compounds which are monosubstituted by R are used. Dichlorosilane is produced in large quantities for the semiconductor industry and is therefore advantageously an inexpensive starting material.

The dichlorosilane is preferably reacted with from 0.5 to 2, more preferably from 0.75 to 1.25 molar equivalents (based on the dihalosilane) metal salt to the desired cyclosiloxane. There are preferably used 20 mmol HRSiCl ₂ to 10 ml to 80 ml of solvent, preferably 15 ml to 25 ml of solvent.

The cyclic siloxanes (H ₂ SiO) _n or (HRSiO) _n prepared by the process according to the invention are storage-stable in solution.

The mixture of zinc carbonate as the metal salt and hexane or toluene as the solvent gave the best results. This reaction is explained in equation (3) with reference to the example H ₂ SiCl ₂ .pyridine:

Instead of pyridine (Py), one of the other nitrogen bases mentioned can also be used.

After the reaction described, the inorganic salts z. B. separated by decantation or filtration.

The Cyclosiloxaneringe obtained by the reaction can be z. B. by chromatographic methods (eg: HPLC or gel permeation chromatography). Alternatively, by at least partial removal of the solvent and subsequent dilution, a rearrangement of the smaller cylosiloxane rings (H ₂ SiO) ₄ and (H ₂ SiO) ₅ in cyclohexasiloxane (H ₂ SiO) ₆ can be achieved. This is in the PCT / DE 2007/000723 (Filing date 19.04.2007 S. 5ff) described in detail, which is incorporated herein by reference. The rearrangement advantageously makes possible a very selective synthesis of cyclohexasiloxane (H ₂ SiO) ₆ . The separation of the solvent, is preferably carried out by distillation, particularly preferably a cold distillation at a temperature around room temperature (below 40 ° C, preferably below 25 ° C) and a vacuum (a pressure less than 100 hPa, preferably less than 10 hPa). After renewed addition of solvent, preferably n-hexane, gives the main product cyclohexasiloxane (H ₂ SiO) ₆ , with a proportion of well over 90%. For this purpose, after the solvent has been separated off, it is preferable to add solvent again directly or at least within 30 minutes, preferably within 5 minutes.

The invention is explained in more detail below by means of exemplary embodiments without being restricted to these: All reactions were carried out under protective gas using the Schlenk technique.

Commercially available starting materials were used and dried according to laboratory instructions.

Embodiment 1: Preparation of cyclosiloxanes of the (H ₂ SiO) _n, n = 4-6 in n-hexane with zinc carbonate and H ₂ SiCl ₂ · 2 pyridine:

First, a solution of dichlorosilane in pyridine) is prepared as follows:
4.23 ml (20 mmol) of a 40% dichlorosilane / toluene solution under isopropanol / dry ice cooling together with 40 ml of toluene are placed in a Schlenk flask (100 ml) with magnetic stir bar. To this solution 3.24 g (41 mmol) of pyridine are added, it comes immediately to the formation of a white precipitate of the resulting product. After completion of the product precipitation, the reaction mixture is slowly warmed to room temperature and the resulting solid is separated by filtration with a Schlenk frit and dried.

The thus complexed dichlorosilane is subsequently H ₂ SiCl ₂ · 2 pyridine (Py) called and used as follows:

In a Schlenk vessel (100 ml) with magnetic stir bar, 2.51 g (20 mmol) of zinc carbonate in 40 ml of n-hexane are placed under ice-cooling. 5.16 g (20 mmol) of H ₂ SiCl ₂ .2 pyridine (Py) are slowly added by means of a funnel. After a reaction time of 30 min, or the end of gas evolution, the solid is filtered off from the solution by means of a Schlenk frit and the solution by NMR spectroscopy (nuclear magnetic resonance - DPX 400 Avance Broker, Rheinstetten, Germany according to the method DEPT 135th ) and by GC-MS (HP 5890 Series II coupled with a mass selective detector HP 5971, use of a Polymethylpolysiloxansäule (30 m x 0.25 mm x 0.25 microns), injector and detector temperature 180 ° C). The solid is washed several times with n-hexane and dried to remove any adhering siloxane residues.
²⁹ Si NMR spectrum:
δ (H ₂ Si 0) ₄ = -46.6 ppm, δ (H ₂ Si 0) ₅ = -48.4 ppm, δ (H ₂ Si 0) ₆ = -48.7 ppm,
Ratio tetramer (H ₂ SiO) ₄ : pentamer (H ₂ SiO) ₅ : hexamer (H ₂ SiO) ₆ : 17.5%: 14.0%: 68.5%
¹ H-NMR spectrum:
δ ( H ₂ SiO) ₄ = about 4.9 ppm, δ ( H ₂ SiO) ₅ = about 4.8 ppm; δ ( H ₂ SiO) ₆ = about 4.7 ppm
GC-MS characterization:
183 m / z (H ₂ SiO) ₄ ; 229 m / z (H ₂ SiO) ₅ ; 275 m / z (H ₂ SiO) ₆
at a retention time of t = 10.575 min.

The analysis results show that the synthesized product is the desired cyclosiloxanes of the type (H ₂ SiO) _n , n = 4-6 in very high purity (at least 98%).

Exemplary Embodiment ₂ Preparation of Cyclosiloxanes of the Type (H ₂ SiO) _n in Toluene with Zinc Carbonate and H ₂ SiCl ₂ .2 (4-t-Butylpyridine):

In a Schlenk flask (100 ml) with magnetic stirrer 3.71 g (10 mmol) H ₂ SiCl ₂ · 2 4-t-butylpyridine (prepared as described for H ₂ SiCl ₂ · 2 pyridine (Py) in Embodiment 1 described above) in 20 Toluene under ice cooling submitted. By means of a funnel, 1.26 g (10 mmol) of ZnCO _{3 are} added. After the evolution of gas has ended, the solid is filtered off from the solution via a Schlenk frit and the solution is analyzed by NMR spectroscopy as described in Example 1.
²⁹ Si NMR spectrum:
δ (H ₂ Si 0) ₄ = -47.0 ppm, δ (H ₂ Si 0) ₅ = -48.6 ppm, δ (H ₂ Si 0) ₆ = -48.8 ppm,
higher homologs at δ = -48.9 ppm, δ = -49.0 ppm and δ = -50.0 ppm;

The analysis results show that the synthesized product is the desired cyclosiloxane type (H ₂ SiO) _n , n = 4-6 (~95%), minor impurities (4-5%) from higher ring homologs are detectable.

Exemplary Embodiment 3 Preparation of Cyclosiloxanes of the Type (H ₂ SiO) _n in Ethyl Acetate with Calcium Carbonate and H ₂ SiCl ₂ .2 Pyridine

In a Schlenk vessel (100 ml) with magnetic stir bar, 1.0 g (10 mmol) of calcium carbonate in 20 ml of ethyl acetate (ethyl acetate) are placed under ice-cooling. By means of a funnel to 2.58 g (10 mmol) H ₂ SiCl ₂ · 2 pyridine (prepared as described in Example 1 above) was added. After the end of gas evolution and a reaction time of 30 min, the solid is filtered off from the solution via a Schlenk frit and analyzed by NMR spectroscopy as described in Example 1:
²⁹ Si NMR spectrum:
δ (H ₂ Si 0) ₄ = -46.6 ppm, δ (H ₂ Si 0) ₅ = -47.9 ppm, δ (H ₂ Si 0) ₆ = -48.3 ppm,
higher homologs at δ = -48.4 ppm, δ = -48.5 ppm and δ = -49.5 ppm
Ratio tetramer (H ₂ SiO) ₄ : pentamer (H ₂ SiO) ₅ : hexamer (H ₂ SiO) ₆ : 20.4%: 24.0%: 55.6%

The analysis results show that the synthesized product is the desired cyclosiloxane type (H ₂ SiO) _n , n = 4-6 (approximately 85%), but these are contaminated with higher ring homologs (approximately 15%). ,

Exemplary Embodiment 4 Preparation of Cyclosiloxanes of the Type (H ₂ SiO) _n in Ethyl Acetate with Lithium Carbonate H ₂ SiCl ₂ .2 (4-Methylpyridine):

In a Schlenk vessel (100 ml) with magnetic stir bar, 0.67 g (10 mmol) of lithium carbonate in 20 ml of ethyl acetate (ethyl acetate) are introduced with ice cooling. By means of a funnel to 2.87 g (10 mmol) H ₂ SiCl ₂ · 2 (4-methylpyridine) (prepared as described for H ₂ SiCl ₂ · 2 pyridine (Py) in Embodiment 1 described) was added. After the end of gas evolution and a reaction time of 30 min, the solid is filtered off from the solution via a Schlenk frit and analyzed by NMR spectroscopy as described in Example 1:
²⁹ Si NMR spectrum:
δ (H ₂ Si 0) ₄ = -46.6 ppm, (H ₂ Si 0) ₅ = -48.0 ppm, δ (H ₂ Si 0) ₆ = -48.3 ppm,
higher homologs at S = -48.5 ppm, S = -49.5 ppm and S = -49.7 ppm
Ratio tetramer (H ₂ SiO) ₄ : pentamer (H ₂ SiO) ₅ : hexamer (H ₂ SiO) ₆ : 24.7%: 53.4%: 21.9%

The analysis results show that the synthesized product is the desired cyclosiloxanes (approximately 85%), but they are contaminated with higher ring homologs (approximately 15%).

Exemplary Embodiment 5 Preparation of Cyclosiloxanes of the Type (H ₂ SiO) _n in Toluene with Zinc Carbonate and H ₂ SiCl ₂ .2 (4-Vinylpyridine):

In a Schlenk flask (100 ml) with magnetic stirrer 3.11 g (10 mmol) H submitted ₂ SiCl ₂ · 2 4-vinylpyridine in 20 ml of toluene under ice cooling. By means of a funnel, 1.26 g (10 mmol) of ZnCO _{3 are} added. After the evolution of gas has ended, the solid is filtered off from the solution via a Schlenk frit and the solution is analyzed by NMR spectroscopy as described in Example 1.
²⁹ Si NMR spectrum:
δ (H ₂ Si 0) ₄ = -46.6 ppm, δ (H ₂ Si 0) ₅ = -48.4 ppm, δ (H ₂ Si 0) ₆ = -48.7 ppm,

The analysis results show that there is = 4-6 is the synthesized product comprises the desired cyclosiloxanes of the (H ₂ SiO) _n, n (~ 95%).

Exemplary Embodiment 6 Preparation of Cyclosiloxanes of the Type (H ₂ SiO) _n , n = 4-6, in N-Hexane with Zinc Carbonate and H ₂ SiCl ₂ .2 (4-Dimethylaminopyridine):

In a Schlenk flask (100 ml) with magnetic stirrer 3.45 g (10 mmol) H ₂ SiCl ₂ · 2 4-dimethylaminopyridine (prepared as described for H ₂ SiCl ₂ · 2 pyridine (Py) in Embodiment 1), in 20 ml n -Hexane submitted under ice-cooling. 1.26 g (10 mmol) of zinc carbonate are slowly added by means of a funnel. After the evolution of gas has ended, the solid is filtered off from the solution via a Schlenk frit and the solution is analyzed by NMR spectroscopy as described in Example 1.
²⁹ Si NMR spectrum:
δ (H ₂ Si 0) ₄ = -46.6 ppm, δ (H ₂ Si 0) ₅ = -48.4 ppm, δ (H ₂ Si 0) ₆ = -48.7 ppm,
¹ H-NMR spectrum:
δ ( H ₂ SiO) ₄ = about 4.9 ppm, δ ( H ₂ SiO) ₅ = about 4.8 ppm; δ ( H ₂ SiO) ₆ = about 4.7 ppm

Claims (6)

Process for the preparation of cyclosiloxanes of the type

wherein n is an integer selected from 1, 2 and 3, by reacting: a.) a halosilane of the type H ₂ SiCl ₂ with 1.5 to 4 molar equivalents of a cyclic amine B, wherein the dihalosilane with the cyclic amine Compounds of the type H ₂ SiCl _2. 2B forms, with b) a salt of a metal from the 1st or 2nd main group or 2nd subgroup of the Periodic Table of the Elements or copper (II) salts or a mixture of these salts, wherein the anion of the Metal salt is carbonate or bicarbonate and the salts contain less than 1% water and less than 1% hydroxide contaminants, the total reaction mixture containing less than 1% water, the cyclic amine B being selected from pyridine, pyrimidine, pyrazine, and / or substituted pyridinines, pyrimidines and pyrazines, wherein the dihalosilane is first mixed with the cyclic amine to form the 1: 2 complexed dichlorosilane before the metal salt is added. A method according to claim 1, characterized in that the metal salt is selected from zinc carbonate, calcium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, copper (II) carbonate, magnesium carbonate, strontium carbonate and barium carbonate. Method according to one of claims 1 to 2, characterized in that the reaction is carried out at a temperature of -80 to 40 ° C. Method according to one of claims 1 to 3, characterized in that the reaction is carried out in an aprotic solvent. A method according to claim 4, characterized in that the solvent is selected from n-hexane, n-pentane, ethyl acetate, tetrahydrofuran, dioxane, toluene, cyclohexane, glyme and mixtures of these solvents. Use of a compound of the type H ₂ SiCl _2. 2B, wherein B represents a cyclic amine selected from pyridine, pyrimidine, pyrazine, and / or substituted pyridinines, pyrimidines and pyrazines, for the preparation of cyclosiloxanes of the type

where n is an integer selected from 1, 2 and 3.