FR2650599A1 - ELECTROCHEMICAL PROCESS FOR THE PREPARATION OF ORGANOSILICIAL COMPOUNDS - Google Patents

Abstract

The invention relates to a process for preparing silanes, carbosilanes or polycarbosilanes having at least one organic group bonded to a silicon atom through an Si - C bond. In the process, a compound I having a -RX substituent where R is a group carbon or divalent hydrocarbon which may be substituted and X is a halogen atom, is subjected to electroreduction in the presence of II a silane of general formula R'4 - a - b SiXa (RX) b where R 'is hydrogen , a hydrocarbon group, a group containing H, C and O atoms, S atoms and / or P atoms, or a group consisting of C, H and N atoms and optionally O atoms, where N is not part of an amino group, X and R are as defined above, the value of a is 1 to 4, the value of b is 0 to 3, and the value of a + b is of 2, 3 or 4. Application: electrochemical synthesis of organosilicon compounds.

Description

The present invention relates to an electrochemical process for synthesis

of compounds

  organosilicon compounds, in particular polycarbosilanes.

  By the term "organosilicon compounds" is meant here compounds in which at least one organic group is attached to a silicon atom by an Si-C bond. These compounds include silanes having a single silicon atom and at least one organic substituent which

  is bound to the silicon atom by a silicon-silicon bond

  carbon, and carbosilanes having at least two silicon atoms which are connected through a group R, representing a divalent or divalent hydrocarbon group which may be substituted, bonded to each silicon atom through an Si-C bond. Said carbosilanes include silanes of the general formula -Si-R-Si- and polycarbosilanes having at least two units of the

  general structure - (R-Si) -, where R is as defined above

  above. The formation of Si-C and Si-CH2-Si bonds is usually carried out via Grignard or Wurtz reactions which involve the use of metals such as magnesium, sodium and lithium. These processes are complicated and costly and they require to protect all additional functional groups that

2650'99

  may be present on the reactants.

  Electrochemical synthesis is a known technology that has been practiced for some time in organic chemistry. It has recently been shown that the silylation of certain compounds by trimethylchlorosilane is possible by electrochemical synthesis. Shono et al. (Chem Letters, 1985, pp. 463-466) described the electrochemical reduction of benzyl and allyl halides in the presence of trimethylchlorosilane with production of the corresponding benzylsilanes and allylsilanes. They also showed the electroreduction of 1,4-dichlorobutene to produce the

  1,4-bis (trimethylsilyl) butene. P. Pons et al. (J.

  Organometallic Chemistry, 1988, pages 31-37) described the electroreduction of carbon tetrachloride, chloroform and methylene chloride with trimethylchlorosilane to obtain the corresponding trimethylsilyl compounds in the presence of a consumable electrode. They also illustrated the electroreductior of trimethylchloromethylsilane with trimethylchlorosilane for obtaining

of hexamethylsilmethylene.

  The Applicant has now discovered that it is possible to use electrochemical synthesis for the

  production of organosilicon compounds as defined above.

  above using dihalosilanes, trihalosilanes, tetrahalosilanes or halocarbohalosilanes. According to the invention, there is provided a process for the preparation of organosilicon compounds comprising at least one organic group bonded to a silicon atom by an Si-C bond, in which a compound (I) bearing a substituent of general formula -RX o R is a divalent carbon or hydrocarbon group which may be substituted, and X is a halogen atom, is electroreduced in the presence of (II) a silane of the general formula R '_abSiXa (RX) R' is selected from hydrogen, hydrocarbon groups, groups containing H, C and O atoms, S atoms and / or P atoms and groups consisting of C, H and N atoms and optionally O, in which N is not part of an amino group, X and R are as defined above, the value of a is 1, 2, 3 or 4, the value of b

  is 0, 1, 2 or 3 and the value of a + b is 2, 3 or 4.

  The compound (I) to be used in the process of the invention may be any compound which has a carbon atom substituted by a halogen. The halogen atom is preferably chlorine, bromine or iodine, the latter being the most reactive. Chlorine and bromine, however, are preferred for reasons of commercial availability and economic considerations. The halogen atom is bonded to a group which may be purely organic or which may be a compound having both organic and inorganic moieties, for example an organosilicon group or an organogermanic group. The group R, to which is bound an atom

  halogen, is a divalent hydrocarbon or hydrocarbon group

  which can be substituted. The carbon groups include,

  for example, acetylene and 1,3-butadiynylene.

  R hydrocarbon groups can range from methylene to very large hydrocarbon groups. It may be saturated alkylenes, for example ethylene, isopropylene, hexylene and octadecylene, unsaturated aliphatic groups such as alkenylenes or alkynylenes, for example the vinylene, propenylene, butadienylene, hexynylene, propynylene and 1,4 groups. octadecenylene, and aromatic groups, for example phenylene, benzylene, tolylene and phenylethylene. The substituted hydrocarbon groups are those in which the carbon atoms carry one or more substituents which may be any groups which are not reactive with the halo groups of the compound (II) under the reaction conditions. These substituents include fluorine and cyano, nitro, oxyethylene, silyl, siloxane and carbosilyl groups. Examples of such substituted hydrocarbon groups include hexafluoropropylene, oxyethylene-oxypropylene-substituted groups, acetyl-substituted groups, ether-substituted groups, and ester-substituted groups. It is preferable that the group R is an aromatically unsaturated, aliphatically unsaturated or aliphatically saturated hydrocarbon group, for example a benzylene, propenylene group,

  isopentylene, butylene, propylene, ethylene or phenylene.

  The most preferred are the methylene and vinylene groups.

  The group R can be linked, on the other hand, to any atom or group. These include, for example, a hydrogen atom, hydrocarbon groups, organosilicon groups, functional organic groups, for example sulfur-containing groups and phosphorus-containing groups, and even halogen atoms. Preferably, the group R is linked on the opposite side to the group X to a hydrogen atom or a halogen atom. Examples of the comose (I) include organic halides, for example a methyl halide such as methyl chloride, dichloromethane, a benzyl halide such as benzyl chloride, a phenyl halide, a vinyl halide, 1,4-dichloro-2-butene, dibromoethylene, 1,2-bis (chloromethyl) benzene, silanes such as trimethylchloromethylsilane and dimethylchloromethylchlorosilane, and siloxanes such as those having at least one unit of formula

  O4x SiR '(CH2X)' o R 'is as defined above

  4-x, X above but is preferably hydrogen, a hydrocarbon group such as alkyl, aryl, alkenyl or alkaryl, or a group containing C, H atoms and optionally N or O, the value of x is from 0, 1 or 2, the value of y is 1, 2 or 3 and the value of x + y is not greater than 3, all the other possibly present units corresponding to the average formula O4_zSiR ', o R' is as defined above and the value of z is 0, 1, 2 or 3, or those which have at least one unit of the general formula ## STR2 ## where R, R ', x and y are as defined above. Siloxanes are preferably avoided because it is difficult to regulate the nature of the

reaction product.

  The compound (II) to be used in the process of the invention is a silane which comprises at least two halogenated substituents at least one of which is a silicon-bonded halogen atom. Iodine is the most reactive halogen, but chlorine and bromine atoms are preferred for reasons of commercial availability and economic considerations. The non-silicon-bonded halogen atoms are connected to the silicon atom via a group R as defined above for the compound (I). Examples of such halogenated substituents are haloalkyl groups such as chloromethyl, chloroisopropyl and 1-bromoheptyl, haloalkenyl groups such as chlorovinyl and bromopropenyl, and haloaryl groups such as chlorophenyl and bromobenzyl. Non-halogenated R 'substituents, if present, include hydrogen, hydrocarbon groups such as alkyl, aryl, alkaryl, aralkyl, alkenyl and alkynyl groups, groups containing C, H and O atoms, for example, groups containing the carboxyl function, groups containing the C = O function, groups containing the aldehyde function and groups containing the epoxy function, groups containing an ether function, groups containing sulfur, or groups containing C, H and N atoms in which N is not part of an amino group, for example substituents containing the cyano group and substituents containing the NO2 group. Examples of such groups are methyl, ethyl, propyl, phenyl, phenylethyl, tolyl, vinyl, allyl, hexenyl, ethynyl, butadiynyl, stearyl, lauryl, ethoxy, methoxy, polyoxyethyl and benzyl. Preferably, R 'is hydrogen or an alkyl or aryl group, and most preferably methyl or phenyl. It is preferable that the value of a + b is equal to 2, two groups R 'then being present, each representing

  independently a substituent as described above.

  The values of a and b are preferably 1 and 1 or 2 and 0, respectively. Examples of the compound (II) include dimethyldichlorosilane, dimethylchloromethylchlorosilane, methyltrichlorosilane, carboxymethyltrichlorosilane, phenylmethyldichlorosilane, diphenyldichlorosilane, methylcyanopropyldichlorosilane, methyldichlorosilane, dichlorosilane, methylbis (chloromethyl) chlorosilane

  and methylglycidoxypropylchloromethylchlorosilane.

  It is necessary to choose certain types of compounds (I) and (II) according to the organosilicon compound which one wishes to synthesize. Other compounds may also be added. Organosilicon compounds which can be prepared by the process of the invention include silanes. Silanes are produced if (I) is a purely organic compound having no silicon atom in its structure, and if a single -RX group is present in (I) or if more than one -RX group is present in (I) and if a fair enough amount of (II) is provided to react with a single -RX group of (I). The resulting silanes include, for example, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, tetramethylsilane, hydroquinyltrimethylamethylene, chloromethyldimethylbutylsilane, dibromovinyl dimethylsilane and the like. 'other. Carboxilanes as defined above can be obtained by the electrochemical reaction of a compound (I) comprising more than one -RX group or a compound (I) of formula XRX with a sufficient amount of compound (II) to react with at least two of these -RX or X-linked X groups, or to provide a sufficient compound (I) having only one -RX group with a compound (II) having more than one atom of silicon-bonded halogen, or by providing certain silicon-containing compounds (I), for example those having a -RX group and an SiX group, for their reaction with a compound (II) which may be the same. In general, the value of a + b in the compound (II) determines, in most cases, the general character of the product carbosilane. When a + b is 2, the use of such a compound (II) increases the chain length of the organosilicon compound produced,

  while if a + b is 3 or 4, a certain degree of.

  Branching is introduced into the organosilicon compound, which in some cases leads to a three-dimensional structure. A mixture of compound (II) o a + b is 2 and compound (II) o a + b is 3 or 4 can lead to predominantly linear carbosilanes with some degree of branching, while increasing the proportion of compound (II) where a + b is 3 or 4 increases the degree of branching, ultimately leading to the production of a resinous carbosilane such as

reaction product.

  Depending on the nature of the desired carbosilane, only one type of each of the compounds (I) and (II) can be reacted together, or a mixture of different types of compound (I) and / or compound can be reacted together. (II). It is also possible to use the same body reacting both as compound (I) and as compound (II), for example a silane having one or more silicon-bonded halogen atoms and one or more -RX groups. For example, chloromethylchlorosilanes that fall within each of the definitions of the compounds (I) and (II) may react with one another. Such a reaction leads to the formation of a polycarbosilane having repeating units of formula - [Si (R ') 2 CH 2] -. These compounds can be linear or cyclic or consist of a mixture of linear and cyclic organosilicon compounds. When it is desired to obtain linear polycarbosilanes, it may be preferable to add other compounds, for example endblocking compounds which may be silanes of the formula R '3 SiX o R' and X are as defined above. above. For example, in order to obtain a linear polymer having the general formula R '[Si (R') 2 R] .SiR'3, the reactants must include, besides the compounds (I) and (II), a silane of the general formula R'3SiX in an amount sufficient to act as a terminal blocking agent for a polymer having the length

desired channel.

  It is, however, preferable to produce relatively small molecules, for example polycarbosilanes having 2 or 3 silicon atoms, which can then be used as precursors for the manufacture of higher molecular weight substances using, for example, of

conventional polymerization.

  The reaction can be performed in any convenient manner using a cell having a cathode and an anode. The cell may be a single-chamber cell, but it is preferable that there are two chambers

  separated by a membrane, for example a sintered disc.

  The cell is equipped with a constant voltage and / or constant current generator to regulate the voltage or current. The electrodes that can be used as a cathode or active electrode are preferably made of an inert metal such as gold, silver or platinum, most preferably silver, or other metal or alloy that is reasonably inert, for example stainless steel, while the opposite electrode (anode) can be either inert or consumable to some extent. The choice of the opposite electrode sometimes depends on the projected reaction. In some cases, a relatively inert opposed electrode is preferable, while in

  in other cases, a consumable electrode is better suited.

  Useful metals for making the opposite electrode include, for example, C, Al, Pt, Ni, Zn and Mg, with C being particularly preferred for an inert electrode and Al being particularly preferred for an electrode.

consumable ...

  It is preferred to use a complexing agent together with a consumable Al electrode. The use of complexing agents counteracts the catalytic activity of the Lewis acids formed. Lewis acids, such as AlCl3, are known catalysts for ring opening, for example, tetramethylsilacyclobutane and even tetrahydrofuran which can be used as a solvent in the process according to the invention. Suitable complexing agents are known to those skilled in the art and include, in particular, tris (3,6-dioxaheptyl) amine and hexamethylphosphoramide. The cell is filled with a solution of an electrolyte that can be any of those that are

  available commercially and which are soluble in the-

  solvent used for the reactants. These electrolytes are salts of the general formula M'Y-M represents, for example, Li, Na, NBu4, NMe4 or NEt4, and Y represents, for example, C104, Cl, Br, I, N03, BF4, AsF6. , BPh4, PF6, AlCl4, CF3SO3 or SCN, Bu, Me, Et and Ph represent respectively butyl, methyl, ethyl and phenyl groups. Examples of suitable electrolytes include tetraethylammonium p-toluenesulfonate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium bromide, and the like. tetraethylammonium tetrafluoroborate,

  lithium and magnesium chloride.

  The solvents usually employed dissolve both the reactants and the electrolytes. Suitable solvents are those in which the reactant is at least partially soluble under the operating conditions of concentration and temperature. These solvents include, in particular, tetrahydrofuran, acetonitrile, abutyrolactone, a

  mixture of dimethoxyethane and nitromethane, 1,3-

  dioxolane, liquid SO2, trimethylurea and dimethylformamide. The electrochemical reaction can be conducted by keeping the intensity constant at predetermined values or by maintaining a constant voltage that has been determined by cyclic voltammetry. The techniques

  Electrochemical techniques are applicable to the process of.

the invention.

  A number of illustrative examples of the invention are now given in which the parts and percentages are all by weight unless otherwise indicated.

Example 1

  In a single compartment cell equipped with a nitrogen inlet, a stirrer and an air-cooling system, 50 ml of a 0.2 molar solution of tetrabutylammonium hexafluorophosphate are placed in the first compartment. tetrahydrofuran and 8.5 g of chloromethyldimethylchlorosilane. A constant current intensity of 125 mA is applied by means of a current / voltage regulator using a sheet

  aluminum as anode and a silver wire as cathode.

  The current is applied for a period of 22 hours to provide 1.9 faradays per mole of ClCH2. A mixture of reaction products is obtained which is analyzed by gas chromatography / mass spectrometry and which consists of approximately 50% of cyclic compounds of which approximately 65% correspond to the formula [(CH 3) 2 Si-CH 2] 32 and about 35% corresponds to the formula [(CH 3) 2 Si-CH 2] 3, and about 50% of linear compounds corresponding to the formula ClCH 2 Si (CH 3) 2 - [CH 2 Si (CH 3) 2 InCl which 84% of compound is equal to 3 about 5 to 8% of each of the compounds is 2, 4 and 5 and traces of the compound

is worth 1.

Example 2

  A 250 ml flask is equipped with a nitrogen purge, a magnetic stirrer, a condenser and an air cooling device. 100 ml of a 0.2 molar solution of tetrabutylammonium hexafluorophosphate in tetrahydrofuran and 15.4 g of 3chloropropyldimethylchlorosilane are introduced. An electrochemical reaction is carried out using a model 362 voltage / current regulator. The cathode is a silver wire (5 cm in length and 0.25 mm in diameter) and the anode is formed of 4 aluminum strips. (3 x 5 x 0.01 cm). A constant current is applied for 25 hours (to provide 2.5 faradays per mole of silane) at a temperature of 23 ° C. The resulting reaction mixture is analyzed by gas chromatography / spectrometry.

  mass. The mixture comprises 83.7% 1,1-dimethyl-1

  s i l a c y c l ob u tane, 8, 1% d of 3-

  unreacted chloropropyldimethylchlorosilane and

  7.9% propyldimethylchlorosilane.

Example 3

  A 250 ml flask is equipped with a nitrogen purge, a magnetic stirrer, a condenser and an air cooling device. 150 ml of a 0.2 molar solution of tetrabutylammonium hexafluorophosphate in tetrahydrofuran and 25.5 g of chloromethyl dimethylchlorosilane are introduced. An electrochemical reaction is carried out as in the preceding example, but providing 2.8 faradays per mole of silane at a temperature of 30 ° C. The resulting reaction mixture is

  analyzed as above. It comprises 62.6% of 1,1,3,3-

  1,1,3,3,5,5-hexamethyl-1,3,5-trisilacyclohexane.

Example 4

  A 250 ml flask is equipped with a nitrogen purge, a magnetic stirrer, a condenser and an air cooling device. 100 ml of a 0.2 molar solution of tetrabutylammonium hexafluorophosphate in tetrahydrofuran, 5.24 g of a, a, odichloroxylene and 4 g of dichlorodimethylsilane are introduced. An electrochemical reaction is carried out as in the example

  previous, but providing 4.8 faradays per mole of o-

  dichloroxylene. The resulting reaction mixture is washed with water, extracted with diethyl ether, dried and analyzed as above. It contains 65% of the compound of formula: GAGS_ (Cil3)

Example 5

  A 250 ml flask is equipped with a nitrogen purge, a magnetic stirrer, a condenser and an air cooling device. 100 ml of a 0.2 molar solution of tetrabutylammonium hexafluorophosphate in tetrahydrofuran, 3.70 g of cisdichlorobutene and 4 g of dichlorodimethylsilane are introduced. An electrochemical reaction is carried out as in the preceding example, but providing 2.13 faradays per mole of cis-dichlorobutene. By analyzing the resulting reaction mixture, it is found that it contains 15% dimethylsilacyclopentene.

Example 6

  A 250 ml flask is equipped with a nitrogen purge, a magnetic stirrer, a condenser and an air cooling device. 100 ml of a 0.2 molar solution of tetrabutylammonium hexafluorophosphate in tetrahydrofuran, 12.5 g of chloromethyltrimethylsilane and 6.5 g of dichloromethylsilane are introduced. An electrochemical reaction is carried out as in the preceding example, but providing 2.3 faradays per mole of chloromethyltrimethylsilane. By analyzing the resulting reaction mixture, it is found that it contains 25% of

bis (trimethylsilyl) methylsilane.

Example 7

  A Schlenk tube is equipped with an aluminum rod serving as anode (pure & 99.5%, 6.35 mm in diameter) and a cylindrical stainless steel cloth serving as a cathode (7.87 meshes / linear cm, 30 cm2). A solution of 14.3 ml of tetrahydrofuran, 0.08 g of tetraethylammonium tetrafluoroborate, 3.6 ml of hexamethylphosphoramide and 0.1 ml of trimethylchlorosilane is subjected to preliminary electrolysis at 100 mA for 2 hours. 2.28 g of chloromethyl dimethylchlorosilane are added. An electrochemical reaction is carried out by applying a constant current for 10 hours (to provide 2.3 faradays per mole of silane) at a temperature of 23 ° C. The resulting reaction mixture is filtered and stripped under reduced pressure to give 11.68 g of distillate. Gas chromatographic / mass spectrometry analysis reveals a

  69% yield of 1,1,3,3-tetramethyl-1,3-

disilacyclobutane.

Example 8

  Using the assembly of Example 7, 4.24 g of chloropropyltrichlorosilane is added to the reaction product of the preceding example and the electrolysis is continued at 200 mA for nearly 6 hours. After three and a half hours, there is a maximum of

  conversion to dichlorosilacyclobutane 45%.

Example 9

  The setup of Example 7 was used, but adding a dry ice condenser to minimize the loss of reactants. A solution of 8.45 ml of tetrahydrofuran, 0.08 g of tetraethylammonium tetrafluoroborate, 2.1 ml of hexamethylphosphoramide, 6.4 ml of dichloromethane and 0.1 ml of trimethylchlorosilane is subjected to preliminary electrolysis at 50 mA. during 2 hours. 3.03 ml of chloromethyl dimethylchlorosilane is added. An electrochemical reaction is carried out by applying a constant current for 53 hours (to provide 4 faradays per mole of silane) at a temperature of 230 ° C. The analysis of the resulting reaction mixture by gas chromatography / mass spectrometry reveals a yield of 74.

of dimethyldichloromethylsilane.

Example 10

  The preparation of Example 9 is used. A solution of 9.16 ml of tetrahydrofuran, 0.08 g of tetraethylammonium tetrafluoroborate, 2.29 ml of hexamethylphosphoramide, 1.28 ml of dichloromethane and 0.1 ml of trimethylchlorosilane is subjected to preliminary electrolysis at 50 mA for 2 hours. 7.27 ml of dimethyldichlorosilane are added and the electrolysis is continued at 50 mA for 24 hours (to provide 2.2 faradays per mole of silane). Analysis of the resulting reaction mixture by gas chromatography / mass spectrometry revealed a yield of 81% (based on the reacted silane) of chlorodimethylchloromethylsilane.

Example 11

  The assembly of Example 9 is used. A solution of 12.67 ml of tetrahydrofuran, 0.08 g of tetraethylammonium tetrafluoroborate, 3.12 ml of hexamethylphosphoramide, 0.85 ml of dichloromethane and 0.1 ml of trimethylchlorosilane is used. is subjected to preliminary electrolysis at 50 mA for 2 hours. Methyltrichlorosilane (4.48 ml) is added and electrolysis is continued at 50 mA for 12.5 hours (to provide 2.2 faradays per mole of silane). Gas chromatographic / mass spectrometric analysis of the resulting reaction mixture revealed a yield of 62% of methyldichlorochloromethylsilane and 13% of methylchlorodichloromethylsilane.

Example 12

  The assembly of Example 9 is used. A solution of 11.8 ml of tetrahydrofuran, 0.08 g. of tetraethylammonium tetrafluoroborate, 2.95 ml of hexamethylphosphoramide, 0.64 ml of dichloromethane and 0.1 ml of trimethylchlorosilane is subjected to preliminary electrolysis at 50 mA for 2 hours. 6.79 g of tetrachlorosilane are added and the electrolysis is continued at 50 mA for 12.5 hours (to provide 2.2 faradays per mole of silane). Analysis of the resulting reaction mixture by gas chromatography / mass spectrometry reveals a 58% yield of trichlorochloromethylsilane, 15% of

  dichlorodichloromethylsilane and 3% chloro-

trichloromethyl.

Example 13

  The assembly of Example 9 is used. A solution of 12.37 ml of tetrahydrofuran, 0.08 g of tetraethylammonium tetrafluoroborate, 3.09 ml of hexamethylphosphoramide, 1.12 ml of phenyl chloride and 0.1 ml of trimethylchlorosilane is subjected to preliminary electrolysis at 50 mA for 2 hours. Methyltrichlorosilane (4.48 g) is added and electrolysis is continued at 50 mA for 12.5 hours (to provide 2.2 faradays per mole of silane). Analysis of the mixture

  resulting reagent by chromatography.

  gaseous / mass spectrometry reveals a 65% yield of dichlorophenylmethylsilane, 10% of methylchlorodiphenylsilane and 6% of dichloromethylsilphenylene.

Example 14

  The assembly of Example 9 is used. A solution of 11.52 ml of tetrahydrofuran, 0.08 g of tetraethylammonium tetrafluoroborate, 2; 88 ml of hexamethylphosphoramide, 1.12 ml of phenyl chloride and 0.1 ml of trimethylchlorosilane are subjected to

  preliminary electrolysis at 50 mA for 2-hours. We--

  6.79 g of methyltrichlorosilane are added and the electrolysis is continued at 50 mA for 12.5 hours (to provide 2.2 faradays per mole of silane). Analysis of the resulting reaction mixture by gas chromatography / mass spectrometry reveals a yield of 68% trichlorophenylsilane, 10% dichlorodiphenylsilane

and 8% trichlorosilphenylene.

Claims (10)

  A process for the preparation of organosilicon compounds having at least one organic group bonded to a silicon atom by an Si-C bond, characterized in that a compound (I) bearing a substituent of the general formula -RX o R represents a group carbon or divalent hydrocarbon which may be substituted and X is a halogen atom, is subjected to an electroreduction in the presence of (II) a silane of general formula R'4. bSiXa (RX) R 'is selected from hydrogen, hydrocarbon groups, groups containing H, C and O atoms, S atoms and / or P atoms, and groups consisting of C, H and N atoms and optionally O atoms. where N is not part of an amino group, X and R are as defined above, the value of a is 1, 2, 3 or 4, the value of b is 0, 1, 2 or 3 and the value of a + b is 2, 3 or 4.   2. Method according to claim 1, characterized in that the R group of the compound (I) is an aromatic hydrocarbon group unsaturated, aliphatically   unsaturated or aliphatically saturated.   3. Process according to claim 1 or 2, characterized in that in the compound (II) R 'is   hydrogen, an alkyl group or an aryl group.   4. Method according to any one of the claims   preceding, characterized in that in the compound (II), the value of a + b is equal to 2.   5. Process according to any one of the claims   preceding, characterized in that it is performed in a cell having two chambers which are separated by a membrane, the cathode is made of silver or steel stainless steel and the anode is inert.   6. Process according to any one of the claims   1 to 4, characterized in that it is performed in a cell having two chambers which are separated by a membrane, the cathode is made of silver or stainless steel and the anode is consumable to some extent.   7. Process according to any one of the claims   preceding, characterized in that a complexing agent is used. An organosilicon compound in which at least one organic group is attached to a silicon atom by an Si-C bond, characterized in that it is prepared by a   process according to any of the claims   preceding. 9. Silane having at least one silicon atom and at least one organic substituent which is bonded to the silicon atom by a silicon-carbon bond, characterized in that it is prepared by a process according to any one of Claims 1 to 7.   A carbosilane having at least two silicon atoms which are connected through a group R representing a divalent carbon or hydrocarbon group which may be substituted, bonded to the silicon atoms by Si-C bonds, characterized in that it is prepared by   a method according to any one of claims 1 to 7.