Process for the preparation of halogenated 1,2-disilaethanes

A process for the preparation of halogenated 1,2-disilaethanes of the general formula EQU X.sub.3-n R.sub.n Si--CHR.sup.1 CHR.sup.1 --SiR.sub.n X.sub.3-n (I) in which R may be identical or different and denotes a hydrogen atom or a monovalent optionally substituted hydrocarbon radical having 1 to 40 carbon atom(s) per radical, PA1 R.sup.1 may be identical or different and denotes a hydrogen atom or a monovalent optionally substituted hydrocarbon radical having 1 to 40 carbon atom(s) per radical, PA1 X denotes a halogen atom and n denotes 0, 1 or 2, wherein halogenated 1,2-disilaethenes of the general formula EQU X.sub.3-n R.sub.n Si--CR.sup.1.dbd.CR.sup.1 --SiR.sub.n X.sub.3-n (II) in which R, R.sup.1, X and n have the meaning stated above therefor, are reacted with hydrogen in the presence of promoting catalysts. The product is produced in high yield and purity.

TECHNICAL FIELD
 The invention relates to a process for the preparation of halogenated
 1,2-disilaethanes.
 BACKGROUND ART
 A large number of processes for the preparation of halogenated
 1,2-disilaethanes are known. Thus, they are obtainable via hydrosilylation
 reactions. For example, the preparation of
 1,2-bis(chlorodimethylsilyl)ethane is carried out via the hydrosilylation
 reaction between chlorodimethylsilane and chlorodimethylvinylsilane. The
 hydrosilylation reactions are described in U.S. Pat. Nos. 3,041,362,
 3,497,539, 3,220,972, 3,674,739, DE-A 2 131 74 1 and the corresponding
 U.S. Pat. No. 3,798,252 (Wacker-Chemie GmbH, published on Mar. 19, 1974)
 and DE-A 2 131 742 (Wacker-Chemie GmbH, laid open on Dec. 28, 1972).
 Further processes for the preparation of 1,2-
 bis(chlorodimethylsilyl)-ethane are chlorination reactions of
 bis(trimethylsilyl)ethane (Kumada et al., J. ORGANOMET. CHEM. 1967, 10(1),
 111-119, and Ishikawa et al., J. ORGANOMET. CHEM. 1970, 23(1), 63-69). It
 is also known that halogenated 1,2-disilaethanes can be prepared by
 reacting disilanes with organyl chlorides or HCl (H. Sakurai et al.,
 TETRAHEDRON LETT. 1966, 45, 5493-7). 1, 2-Bis(chlorodimethylsilyl)ethane
 is also obtainable via the hydrosilylation of dimethylmethoxyvinylsilane
 with chlorodimethylsilane (Suryanarayanan et al., J. ORGANOMET. CHEM.
 1973, 55(1), 65-71).
 DE-A 2 131 741 and the corresponding U.S. Pat. No. 3,798,252 (Wacker-Chemie
 GmbH, published on Mar. 19, 1974), DE-A2 131 742 (Wacker-Chemie GmbH, laid
 open on Dec. 28, 1972) and DE-A 2 001 303 (Wacker-Chemie GmbH, laid open
 on Jul. 22, 1971) describe halogenated 1,2-disilaethanes, such as
 1,2-bis(chlorodimethylsilyl)ethane, as solvents in the preparation of
 alkenylsilanes, such as chlorodimethylvinylsilane.
 DISCLOSURE OF THE INVENTION
 It was an object of the present invention to provide a process for the
 preparation of halogenated 1,2-disilaethanes which is simple, the
 halogenated 1,2-disilaethanes being obtained in high yield and purity over
 a short reaction time. It was a further object to provide a particularly
 economical and environmentally friendly process for the preparation of
 halogenated 1,2-disilaethanes. These and other objects are achieved by the
 present invention.
 DETAILED DESCRIPTION OF THE INVENTION
 The invention relates to a process for the preparation of halogenated
 1,2-disilaethanes of the general formula
EQU X.sub.3-n R.sub.n Si--CHR.sup.1 CHR.sup.1 --SiR.sub.n X.sub.3-n (I),
 in which R may be identical or different and denotes a hydrogen atom or a
 monovalent optionally substituted hydrocarbon radical having 1 to 40
 carbon atom(s) per radical, R.sup.1 may be identical or different and
 denotes a hydrogen atom or a monovalent optionally substituted hydrocarbon
 radical having 1 to 40 carbon atom(s) per radical, X denotes a halogen
 atom, and n denotes 0, 1 or 2,
 wherein halogenated 1,2-disilaethenes of the general formula
EQU X.sub.3-n R.sub.n Si--CR.sup.1.dbd.CR.sup.1 --SiR.sub.n X.sub.3-n (II),
 in which R, R.sup.1, X and n have the meaning stated above therefor, are
 reacted with hydrogen in the presence of a hydrogenation catalyst.
 Examples of hydrocarbon radicals R are alkyl radicals such as the methyl,
 ethyl, n-propyl, isopropyl, 1-n-butyl, 2-butyl, isobutyl, tert-butyl,
 n-pentyl, isopentyl, neopentyl, and tert-pentyl radicals, hexyl radicals
 such as the n-hexyl radical, heptyl radicals such as the n-heptyl radical,
 octyl radicals such as the n-octyl radical and isooctyl radicals such as
 the 2,2,2-trimethylpentyl radical, nonyl radicals such as the n-nonyl
 radical, decyl radicals such as the n-decyl radical, and octadecyl
 radicals such as the n-octadecyl radical; cycloalkyl radicals such as the
 cyclopentyl, cyclohexyl, cycloheptyl, and methylcyclohexyl radicals;
 alkenyl radicals such as the vinyl, allyl, 3-butenyl, 5-hexenyl,
 1-propenyl and 1-pentenyl radicals; alkynyl radicals such as the ethynyl,
 propargyl, and 1-propynyl radicals; aryl radicals such as the phenyl,
 naphthyl, anthryl and phenanthryl radicals; alkaryl radicals, such as o-,
 m- and p-tosyl radicals, xylyl radicals, and ethylphenyl radicals; and
 aralkyl radicals such as the benzyl radical, the phenylethyl radical and
 the phenylnonyl radical.
 Examples of substituted hydrocarbon radicals R are haloalkyl rad//icals
 such as the 3,3,3-trifluoro-n-propyl radical, the
 2,2,2,2',2',2'-hexafluoroisopropyl radical, and the heptafluoroisopropyl
 radical; haloaryl radicals such as the o-, m- and p-chlorophenyl radicals;
 and hydrocarbon radicals substituted by amino, mercapto and ammonium
 groups and having 1 to 18 carbon atoms.
 The radical R is preferably a hydrogen atom or a monovalent hydrocarbon
 radical having 1 to 18 carbon atom(s) per radical, the hydrogen atom, and
 the methyl and ethyl radicals being particularly preferred.
 Examples of unsubstituted and substituted radicals R are all applicable
 also to radicals R.sup.1. The radical R.sup.1 is preferably a hydrogen
 atom or a monovalent hydrocarbon radical having 1 to 18 carbon atom(s) per
 radical, the hydrogen atom and the methyl and ethyl radicals being
 particularly preferred.
 Examples of X are fluorine, chlorine, bromine and iodine, chlorine being
 preferred.
 Preferred examples for halogenated 1,2-disilaethanes of the formula (I)
 are:
 1,2-bis(chlorodimethylsilyl)ethane,
 1,2-bis(dichloromethylsilyl)ethane,
 1,2-bis(trichlorosilyl)ethane,
 1,2-bis(chlorodiethylsilyl)ethane,
 1,2-bis(dichloroethylsilyl)ethane,
 1-(chlorodimethylsilyl)-2-(dichloromethylsilyl)ethane,
 1,2-bis(chlorodimethylsilyl)propane,
 1,2-bis(chlorodimethylsilyl)butane and
 2,3-bis(chlorodimethylsilyl)butane.
 Particularly preferred 1,2-disilaethanes(I) are:
 1,2-bis(chlorodimethylsilyl)ethane,
 1,2-bis(dichloromethylsilyl)ethane, and
 1,2-bis(trichlorosilyl)ethane.
 Further examples of halogenated 1,2-disilaethanes of the formula (I) are
 the corresponding fluorine, bromine and iodine derivatives of the examples
 above, the corresponding bromine derivatives being preferred.
 Preferred examples of the halogenated 1,2-disilaethenes of the formula (II)
 which are used in the process according to the invention are the cis and
 trans isomers of
 1,2-bis(chlorodimethylsilyl)ethene,
 1,2-bis(dichloromethylsilyl)ethene,
 1,2-bis(trichloromethyl)ethene,
 1,2-bis(chlorodiethylsilyl)ethene,
 1,2-bis(dichloroethylsilyl)ethene,
 1-(chlorodimethylsilyl)-2-(dichloromethylsilyl)ethene,
 1,2-bis(chlorodimethylsilyl)prop-1-ene,
 1,2-bis(chlorodimethylsilyl)but-1-ene, and
 2,3-bis(chlorodimethylsilyl)but-2-ene.
 Particularly preferred are the cis and trans isomers of
 1,2-bis(chlorodimethylsilyl)ethene,
 1,2-bis(dichloromethylsilyl)ethene, and
 1,2-bis(trichlorosilyl)ethene.
 Further examples of halogenated 1,2-disilaethenes of the formula (II) are
 the corresponding fluorine, bromine and iodine derivatives of the
 foregoing compounds, the corresponding bromine derivatives being
 preferred.
 Halogenated 1,2-disilaethenes are preferably prepared by a hydrosilylation
 reaction between vinylsilanes and hydridosilanes and subsequent hydrogen
 abstraction. Halogenated 1,2-disilaethene are obtained as byproducts of
 1,2-disilaethane preparation from vinylsilanes and hydridosilanes. In the
 process according to the invention, halogenated 1,2-disilaethenes of the
 formula (II) and hydrogen are reacted with one another preferably in a
 molar ratio (ratio of double bond in (II) to molecular H.sub.2) of from
 1:0.6 to 1:10.sup.10, more preferably in a molar ratio of from 1:0.8 to
 1:10.sup.9, and most preferably in a molar ratio of from 1:1 to
 1:10.sup.8.
 Preferably used hydrogenation-promoting catalysts are homogeneous
 catalysts, heterogeneous catalysts and catalysts for catalytic transfer
 hydrogenation, preferably heterogeneous catalysts and homogeneous
 catalysts, most preferably, heterogeneous catalysts.
 Examples of heterogeneous catalysts, i.e. those which are present on
 supports, are metals of subgroup VIII of the Periodic Table, such as
 palladium, platinum, nickel, cobalt and iron; copper; mixtures of the
 above-mentioned metals; metal oxides of the above-mentioned metals, such
 as rhenium oxide, mixed metal oxides of the above-mentioned metals, and
 copper chromite; and metal sulfides of the above-mentioned metals, such as
 cobalt and nickel sulfide and molybdenum sulfide. The metals, e.g.
 palladium and platinum, are preferred heterogenous catalysts, and
 palladium is a particularly preferred catalyst.
 The metals are preferably present in finely divided form on the supports.
 Non-limiting examples of supports are active carbon; carbon; inorganic
 oxides such as silica, alumina, titanium dioxide, zirconium dioxide and
 silicates; carbonates such as calcium carbonate and barium carbonate;
 sulfates such as barium sulfate; and organic supports, such as
 silica-filled polyethyleneimines. Carbon and active carbon are preferred
 supports.
 Examples of homogeneous catalysts are tricarbonylchromium-solvent
 complexes, cobalt, ruthenium, rhodium, iridium, platinum and titanium
 compounds and also Ziegler catalysts, cobalt, ruthenium, rhodium, iridium,
 platinum and titanium compounds being preferred and ruthenium, rhodium,
 iridium and platinum compounds being particularly preferred.
 Examples of catalysts for transfer hydrogenation are palladium, nickel and
 platinum, palladium and nickel being preferred and palladium being
 particularly preferred. The catalysts are preferably used in amounts of
 from 0.01 to 20% by weight, based on the total weight of the halogenated
 1,2-disilaethenes of the formula (II) and hydrogen, more preferably in
 amounts of from 0.1 to 5% by weight, based on the total weight of the
 halogenated 1,2-disilaethenes of the formula (II) and hydrogen.
 The process according to the invention is preferably carried out at a
 temperature of from -30.degree. C. to +160.degree. C., preferably from
 +20.degree. C. to +100.degree. C. Furthermore, the process according to
 the invention is preferably carried out at a pressure of from 0.5 to 500
 bar, preferably from 0.6 to 50 bar, more preferably from 0.7 to 20 bar.
 The halogenated 1,2-disilaethanes of the formula (I) which are prepared by
 the subject invention process can not only be isolated as pure substance;
 they may also be prepared in situ, i.e. they can be obtained directly
 after the reaction without a further purification step such as
 distillation, in a purity of from 85 to 99%, preferably from 95 to 99%.
 The halogenated 1,2-disilaethanes of the formula (I) which are prepared by
 the process according to the invention can be isolated by distillation
 from the reaction mixture; or, after the addition of a suitable solvent,
 from the corresponding solution; or can optionally be crystallized from
 solution.
 The process according to the invention can be carried out without a
 solvent, in a nonpolar aprotic or polar aprotic solvent, or a combination
 of such solvents, the use of no solvent or of an aprotic solvent being
 preferred, and the use of no solvent being particularly preferred. In the
 process according to the invention, there is therefore no need to use a
 solvent, although pure nonpolar aprotic or polar aprotic solvents or
 mixtures thereof may be used if desired. The solvents may be coordinating
 or noncoordinating. Preferably, the solvents or mixtures thereof have a
 boiling point of from 20.degree. C. to 250.degree. C. at 1013 hPa, in
 particular of from 30.degree. C. to 230.degree. C. at 1013 hPa.
 Examples of suitable aprotic organic solvents are hydrocarbons such as
 saturated linear hydrocarbons, preferably hexane or heptane; saturated
 cyclic hydrocarbons, preferably cyclohexane; unsaturated hydrocarbons,
 preferably aromatic hydrocarbons such as benzene, toluene or xylene;
 ethers, preferably diethyl ether, di-n-butyl ether, tert-butyl methyl
 ether, dimethoxyethane or cyclic ethers; or other, heteroatom-substituted
 compounds, such as, for example, amines, preferably tributylamine or
 pyridine. Hexane and heptane are particularly preferred.
 When solvents are used, they are preferably employed in amounts of
 0.01-1000, in particular 1-100, equivalents by weight, based on the total
 weight of the halogenated 1,2-disilaethenes of the formula (II). The
 solvents are preferably removed after the reaction. The process has the
 advantage that halogenated 1,2-disilaethanes of the formula (I) are
 obtained in high yield and purity in a short reaction time. Furthermore,
 apart from the catalyst, the process requires no additional activation,
 for example by a solvent.
 In the process according to the invention, the reaction residues which are
 obtained in the preparation of alkenylsilanes (in particular vinylsilanes)
 and contain halogenated 1,2-disilaethenes are preferably used as
 halogenated 1,2-disilaethenes of the formula (II). Reaction residues which
 are obtained in the preparation of chlorodimethylvinylsilanes and contain
 1,2-bis(chlorodimethylsilyl)ethene are preferably used as halogenated
 1,2-disilaethenes of the formula (II).
 The alkenylsilanes are preferably prepared by an addition reaction between
 silanes having Si-bonded hydrogen atoms, the other silicon valences being
 saturated by halogen atoms and/or monovalent hydrocarbon radicals, with an
 optionally substituted acetylene, in the presence of catalysts promoting
 the addition of Si-bonded hydrogen at an aliphatic multiple bond,
 so-called "hydrosilylation catalysts," such as platinum catalysts. The
 process is described in German Offenlegungsschrift 2 131 741 and the
 corresponding U.S. Pat. No. 3,798,252 published on Mar. 19, 1974,
 Wacker-Chemie GmbH, incorporated herein by reference.
 Chlorodimethylvinylsilane is preferably prepared by an addition reaction of
 dimethylchlorosilane with acetylene in the presence of catalysts promoting
 the addition of Si-bonded hydrogen at an aliphatic multiple bond. The
 preparation of chlorodimethylvinylsilane is best described in example 12
 of the above-mentioned U.S. Pat. No. 3,798,252.
 The reaction residue, preferably distillation residue, consists of a
 mixture of 1,2-bis(chlorodimethylsilyl)ethane,
 1,2-bis(chlorodimethylsilyl)ethene and other polychlorinated compounds
 which cannot be separated by fractional distillation by conventional
 means. The process according to the invention therefore proves
 particularly advantageous in the working-up of distillation residues,
 which would otherwise have to be disposed of in an expensive manner.
 1,2-bis(chlorodimethylsilyl)ethane and 1,2-bis(chlorodimethylsilyl)-ethene
 obtained can be recycled to a very great extent (about 70% by weight) by
 the process according to the invention. By working up the reaction residue
 or the products of the secondary reaction, it will no longer be necessary,
 owing to the large amounts occurring on the world market, to carry out
 syntheses of, for example, 1,2-bis(chlorodimethylsilyl)ethane which
 consume raw materials. It is therefore a particularly environmentally
 friendly and economical process.
 The 1,2-disilaethanes of the general formula (I) prepared by the subject
 invention process are used, in particular, for synthetic purposes, for
 example in the area of pharmaceutical synthesis, agrochemistry or polymer
 chemistry, or as solvents, for analytical purposes, and for academic
 purposes. It is possible, for example, to carry out reactions such as
 substitution, deprotonation and addition reactions, etc., on
 1,2-disilaethanes.
 The 1,2-disilaethanes prepared by the process according to the invention,
 preferably 1,2-bis(chlorodimethylsilyl)ethane, may be used as protective
 groups for amines in the area of organic pharmaceutical synthesis.
 1,2-bis(chlorodimethylsilyl) ethane is the reagent most frequently used for
 the preparation of stabase adducts. Basic primary amines (pKa about 10-11)
 form stabase-adducts in high yields at room temperature in the presence of
 triethylamine in dichloromethane. Various aliphatic amines, .alpha.-amino
 acid esters, methyl 6-aminopenicillanate, N,N-dialkylhydrazines and
 .theta.-isiodoanilines may be protected by this method. Less basic amines
 (generally anilines, pKa about 4-5) require more drastic conditions
 (n-butyl lithium/diethyl ether/-78.degree. C.).

In the examples described below, all parts and percentages, unless
 indicated otherwise, are based on weight. Furthermore, all viscosity data
 are based on a temperature of 25.degree. C. Unless stated otherwise, the
 examples below were carried out at a pressure of the surrounding
 atmosphere, i.e. about 1000 hPa, and at room temperature, i.e. at about
 20.degree. C., or at a temperature which is established on combining the
 reactants at room temperature without additional heating or cooling. The
 hydrogenations were carried out in a 1 liter pressure autoclave.
 EXAMPLE 1
 Preparation of 1,2-bis(chlorodimethylsilyl)ethane C.sub.6 H.sub.14 Si.sub.2
 Cl.sub.2
 H.sub.2 gas was forced into 300.0 g (1.41 mol) of 1,2-bis
 (chlorodimethylsilyl)ethene and 1.5 g(0.7 mmol of pure Pd) of Pd/active
 carbon while stirring at a temperature of 50.degree. C., until a pressure
 of 5.0 bar was reached. As a result of the reaction, the pressure
 gradually decreased again to about 2.0 to 2.5 bar (progressing
 hydrogenation reaction). Further H.sub.2 gas was forced in until a
 pressure of 5.0 bar was reached. Once again the pressure decreased to 2.0
 to 2.5 bar, as a result of the hydrogenation reaction. This process was
 repeated about 15 to 20 times until the pressure remained constant at 5
 bar when further H.sub.2 gas was forced in, i.e. no more H.sub.2 gas was
 absorbed by the system. Stirring was then continued for 2 h at a pressure
 of 5 bar and a temperature of 50.degree. C. After venting, filtration was
 effected over a pressure drop. The results are summarized in Table 1.
 EXAMPLE 2
 Preparation of 1,2-bis(dichloromethylsilyl)ethane C.sub.4 H.sub.8 Si.sub.2
 Cl.sub.4
 Example 1 was repeated with the modification that, instead of 300.0 g (1.41
 mol) of 1,2-bis(chlorodimethylsilyl)ethene, 300.0 g (1.18 mol) of
 1,2-bis(dichloromethylsilyl)ethene were used. The results are summarized
 in Table 1.
 EXAMPLE 3
 Preparation of 1,2-bis(trichlorosilyl)ethane C.sub.2 H.sub.2 Si.sub.2
 Cl.sub.6
 Example 1 was repeated with the modification that, instead of 300.0 g (1.41
 mol) of 1,2-bis(chlorodimethylsilyl)ethene, 300.0 g (1.02 mol) of
 1,2-bis(trichlorosilyl)ethene were used. The results are summarized in
 Table 1.
 EXAMPLE 4
 Preparation of 1,2-bis(chlorodiethylsilyl)ethane C.sub.10 H.sub.22 Si.sub.2
 Cl.sub.2
 Example 1 was repeated with the modification that, instead of 300.0 g (1.41
 mol) of 1,2-bis(chlorodimethylsilyl)ethene, 300.0 g (1.11 mol) of
 1,2-bis(chlorodiethylsilyl)ethene were used. The results are summarized in
 Table 1.
 EXAMPLE 5
 Preparation of 1,2-bis(dichloroethylsilyl)ethane C.sub.6 H.sub.12 Si.sub.2
 Cl.sub.4
 Example 1 was repeated with the modification that, instead of 300.0 g (1.41
 mol) of 1,2-bis(chlorodimethylsilyl)ethene, 300.0 g (1.06 mol) of
 1,2-bis(dichloroethylsilyl)ethene were used. The results are summarized in
 Table 1.
 EXAMPLE 6
 Preparation of 1-(chlorodimethylsilyl)-2-(dichloromethylsilyl)ethane
 C.sub.5 H.sub.11 Si.sub.2 Cl.sub.3
 Example 1 was repeated with the modification that, instead of 300.0 g (1.41
 mol) of 1,2-bis(chlorodimethylsilyl)ethene, 300.0 g (1.28 mol) of
 1-(chlorodimethylsilyl)-2-(dichloromethylsilyl)ethene were used. The
 results are summarized in Table 1.
 EXAMPLE 7
 Preparation of 1,2-bis(chlorodimethylsilyl)propane C.sub.7 H.sub.16
 Si.sub.2 Cl.sub.2
 Example 1 was repeated with the modification that, instead of 300.0 (1.41
 mol) of 1,2-bis(chlorodimethylsilyl)ethene, 300.0 g (1.32 mol) of
 1,2-bis(dichlorodimethylsilyl)prop-1-ene were used. The results are
 summarized in Table 1.
 EXAMPLE 8
 Preparation of 1,2-bis(chlorodimethylsilyl)-butane C.sub.8 H.sub.18
 Si.sub.2 Cl.sub.2
 Example 1 was repeated with the modification that, instead of 300.0 g (1.41
 mol) of 1,2-bis(chlorodimethylsilyl)ethene, 300.0 g (1.24 mol) of
 1,2-bis(dichloromethylsilyl)but-1-ene were used. The results are
 summarized in Table 1.
 EXAMPLE 9
 Preparation of 2,3-bis (chlorodimethylsilyl)butane C.sub.9 H.sub.18
 Si.sub.2 Cl.sub.2
 Example 1 was repeated with the modification that, instead of 300.0 g (1.41
 mol) of 1,2-bis(chlorodimethylsilyl)ethene, 300.0 g (1.24 mol) of
 2,3-bis(dichloromethylsilyl)but-2-ene were used. The results are
 summarized in Table 1.
 EXAMPLE 10
 Working-up of Distillation Residues of the Chlorodimethylvinylsilane
 (VM.sub.2) Preparation I
 Chlorodimethylvinylsilane is prepared by a hydrosilylation reaction of
 chlorodimethylsilane and acetylene. Distillation residues contain
 considerable amounts of 1,2-bis(chlorodimethylsilyl)ethane and
 1,2-bis(chlorodimethylsilyl)ethene in addition to other residues.
 H.sub.2 gas was forced into a mixture of 300.0 g (294 ml) of VM.sub.2
 residue comprising 1,2-bis(chlorodimethylsilyl)ethane,
 1,2-bis(chlorodimethylsilyl)ethene and other compounds, including
 polychlorinated compounds, and 1.5 g (0.7 mmol of pure Pd) of Pd/active
 carbon while stirring at a temperature of 50.degree. C., until a pressure
 of 5.0 bar was reached. As a result of the reaction, the pressure
 gradually dropped again to about 2.0 to 2.5 bar (progressing hydrogenation
 reaction). Further H.sub.2 gas was forced in until a pressure of 5.0 bar
 was reached. The pressure dropped again to 2.0 to 2.5 bar as a result of
 the hydrogenation reaction. This process was repeated about 15 to 20 times
 until the pressure remained constant at 5 bar on forcing in further
 H.sub.2, gas, i.e. no more H.sub.2 gas was absorbed by the system.
 Stirring was then continued for 2 h at a pressure of 5 bar and a
 temperature of 50.degree. C.
 After the apparatus had been vented, filtration was effected via a pressure
 filter, and distillation effected over a 30 cm packed column at a pressure
 of 5 bar and a temperature of 75-80.degree. C. The results are summarized
 in Table 1.
 EXAMPLE 11
 Working-up of Distillation Residues of the Chlorodimethylvinylsilane
 (VM.sub.2) Preparation I
 Chlorodimethylvinylsilane is prepared by a hydrosilylation reaction of
 chlorodimethylsilane and acetylene. Distillation residues contain
 considerable amounts of 1,2-bis(chlorodimethylsilyl)ethane and
 1,2-bis(chlorodimethylsilyl)ethene in addition to other residues.
 445.1 g (437 ml) were subjected to a fractional distillation. H.sub.2 gas
 was forced into 261.0 g (256 ml) of VM.sub.2 residue from the
 fractionation, (comprising 1,2-bis(chlorodimethylsilyl)ethane,
 1,2-bis(chlorodimethylsilyl)ethene) and 1.5 g (0.7 mmol of pure Pd) of
 Pd/active carbon while stirring at a temperature of 50.degree. C., until a
 pressure of 5.0 bar was reached. As a result of the reaction, the pressure
 gradually dropped again to about 2.0 to 2.5 bar. Further H.sub.2 gas was
 forced in until a pressure of 5.0 bar was reached. The pressure dropped
 again to 2.0 to 2.5 bar as a result of the hydrogenation reaction. This
 process was repeated about 15 to 20 times until the pressure remained
 constant at 5 bar on forcing in further H.sub.2 gas, i.e. no more H.sub.2
 gas was absorbed by the system. Stirring was then continued for 2 h at a
 pressure of 5 bar and a temperature of 50.degree. C.
 After the apparatus had been vented, filtration was effected via a pressure
 filter. The results are summarized in Table 1.
 EXAMPLE 12
 Working-up of Distillation Residues of the Chlorodimethylvinylsilane
 (VM.sub.2) Preparation I
 Chlorodimethylvinylsilane is prepared by a hydrosilylation reaction of
 chlorodimethylsilane and acetylene. Distillation residues contain
 considerable amounts of 1,2-bis(chlorodimethylsilyl)ethane and
 1,2-bis(chlorodimethylsilyl)ethene in addition to other residues.
 445.1 g (437 ml) were subjected to a fractional distillation. H.sub.2 gas
 was forced into 261.0 g (256 ml) of VM.sub.2 residue (comprising
 1,2-bis(chlorodimethylsilyl)ethane, 1,2-bis(chlorodimethylsilyl)ethene)
 and 1.5 g (0.7 mmol of pure Pd) of Pd/active carbon while stirring at a
 temperature of 50.degree. C., until a pressure of 5.0 bar was reached. As
 a result of the reaction, the pressure gradually dropped again to about
 2.0 to 2.5 bar. Further H.sub.2 gas was forced in until a pressure of 5.0
 bar was reached, where the pressure dropped again to 2.0 to 2.5 bar. This
 process was repeated about 15 to 20 times until the pressure remained
 constant at 5 bar on forcing in further H.sub.2 gas, i.e. no more H.sub.2
 gas was absorbed by the system. Stirring was then continued for 2 h at a
 pressure of 5 bar and a temperature of 50.degree. C.
 After the apparatus had been vented, filtration was effected via a pressure
 filter and distillation effected over a 30 cm packed column at a pressure
 of 5 bar and a temperature of 75-80.degree. C. The results are summarized
 in Table 1.
 EXAMPLE 13
 Preparation of 1,2-bis(chlorodimethylsilyl)ethane by homogeneous catalysis
 Example 1 was repeated with the modification that, instead of 1.5 g (0.7
 mmol of pure Pd) of palladium/active carbon, 0.7 g (0.7 mmol) of
 (triphenylphosphine)ruthenium(II) dichloride were used. The results are
 summarized in Table 1.
 EXAMPLE 14
 Preparation of 1,2-bis(chlorodimethylsilyl)ethane by catalytic transfer
 hydrogenation
 Example 1 was repeated with the modification that, instead of 1.5 g (0.7
 mmol of pure Pd) of Pd/active carbon and H.sub.2 gas, 1.5 g (0.7 mmol of
 pure Pd) and 127.4 g (1.55 mol) of cyclohexene were used. The results are
 summarized in Table 1.
 TABLE 1
 Yields [G], Yields [%] and Purities Obtained in Examples 1 to 14
 Example Yield [g] Yield [%] Purity [%]
 1 299.9 99 99
 2 296.3 98 99
 3 292.8 97 99
 4 290.1 96 98
 5 289.8 96 98
 6 290.6 96 98
 6 290.6 96 98
 7 293.6 97 98
 8 293.4 97 98
 9 293.4 97 98
 10 177.9 88* 99
 11 261.0 87* 99
 12 231.0 77* 99
 13 293.8 97 98
 14 293.8 97 98
 *Based on 1,2-bis(chlorodimethylsilyl)ethane and
 1,2-bis(chlorodimethylsilyl)ethene fraction in the mixture.