JPH03104893A - Method for synthesizing polysilane - Google Patents

Abstract

PURPOSE:To inexpensively and easily synthesize the polysilane having a high degree of polymerization in high yield by diaphragmless-electrolyzing an electrolyte contg. organodichloromonosilane using an anode of Al and Mg and a cathode of Al, Mg and other materials. CONSTITUTION:Organodichloromonosilane as the starting material is mixed with a supporting electrolyte or with a polar solvent contg. the supporting electrolyte to obtain an electrolyte. The electrolyte is electrolyzed in an electrolytic cell free of a diaphragm. Pure Al, an Al alloy, pure Mg and an Mg alloy are used for the anode and cathode, or Al or Mg is used for the anode and other materials for the cathode. When the former materials are used, electrolysis is carried out while reversing the polarities of both electrodes at regular time intervals. Dichlorodimethylsilane, dichloromethylphenylsilane or dichlorodiphenylsilane are preferably used as the organodichloromonosilane. The electrolysis product is separated and refined to obtain the polysilane such as polydimethylsilane and polymethylphenylsilane, and the Cl is deposited and removed as AlCl3, MgCl2, etc.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for synthesizing polysilane, and more specifically to the synthesis of polysilane useful as a precursor for SiC fibers, SiC molded bodies, etc., and as a polymerization initiator for polystyrene, etc. Regarding the method. [Conventional technology] Conventionally, when dichloroorganosilane is used as a starting material, the main methods for synthesizing polysilane include reductive dechlorination and condensation reaction with alkali metals such as sodium, sodium-potassium alloy, and lithium. It has been carried out in

Another method for synthesizing polysilane is a method in which dichlorodiphenylsilane is used as a starting material and the starting material is electrolyzed in an electrolytic solution containing n - Bu 4N C Q○4 as a supporting electrolyte, as described by E. Hen
(Journal o
f Organometallic Chemi
try vo1.212 (1981) P. 1
55-161). [Problems to be Solved by the Invention] However, in the method of dechlorinating and condensing dichloroorganosilane or the like with an alkali metal, the alkali metal used is expensive, so the cost of the resulting polysilane is high.

Furthermore, since the alkali metal itself is extremely dangerous, it is difficult and dangerous to handle during synthesis. Polysilane can be synthesized by electrolyzing dichlorodiphenylsilane, but cyclic octaphenyltetrasilane with a degree of polymerization of 4 is only obtained in a yield of 0.5 to 3.0%, and polymerization is difficult. Both the degree and the yield were extremely low and a sufficient amount could not be obtained.

Furthermore, when dichlorodialkylsilane or dichloroalkylarylsilane is used as a starting material, the desired polysilane is not produced at all or only a trace is produced, and polysiloxanes other than the desired product are produced. It was put away.

Therefore, the inventors first electrolyzed at least one of dichloroorganodisilane or trichloroorganodisilane in an electrolytic solution consisting of a polar solvent containing a supporting electrolyte in a dry atmosphere, and separated the resulting product. proposed a method for synthesizing polysilane characterized by purification and isolation (Japanese Patent Application No. 1983-257360).
.

However, although this method is a simple and inexpensive method of synthesizing polysilane with good yield, it requires the use of expensive metals such as platinum in the electrolytic cell with a diaphragm and electrode materials, and it inevitably generates by-products. Improvements have been desired since it is difficult to treat raw chlorine ions.

Additionally, there is an increasing demand for the development of synthetic methods for producing polysilanes with a higher degree of polymerization in high yields.

The present invention has been made in view of the current situation, and an object of the present invention is to treat by-product chlorine ions without using a diaphragm and by using lightweight and inexpensive aluminum or magnesium electrodes. It is an object of the present invention to provide a method for easily synthesizing polysilane having a high degree of polymerization with high yield and efficiency.

[Means for Solving the Problems] Therefore, as a result of intensive research in order to achieve the above object, the present inventors found that a halogenated organosilicon compound is mixed with a supporting electrolyte, or a polar solvent containing a supporting electrolyte is used. As an electrolytic electrode, use an aluminum or magnesium electrode for both the anode and the cathode, or use an aluminum or magnesium electrode for the anode and another electrode for the cathode. This book was based on the knowledge that the above objective could be solved by electrolyzing in an electrolytic cell without a diaphragm using an electrode material, and further, in the case of the former, reversing the polarity at regular intervals. Completed the invention. In the synthesis method of the present invention, dichloroorganomonosilane is used as a starting material. Dichloroorganomonosilanes are not particularly limited and include various types, including dichlorodialkylsilanes such as dichlorodimethylsilane, dichloroalkylarylsilanes such as dichloromethylphenylsilane, or dichlorodiarylsilanes such as dichlorodiphenylsilane. is preferable. The starting material is at least Q. Qlmo117m
They are mixed at the above concentrations, and are selected and used as appropriate depending on the electrolytic conditions. If the concentration is less than the lower limit of the above range, the mixed starting materials will be decomposed by impurities in the polar solvent or supporting electrolyte, especially water, and will no longer function, which is undesirable. In the synthesis method of the present invention, the electrolytic solution for electrolyzing the above-mentioned starting materials is used by mixing a supporting electrolyte with the starting materials or by mixing with a polar solvent containing the supporting electrolyte. The supporting electrolyte used in the present invention must have a wide usable potential range and a property that does not react with the starting materials or polar solvents used, and specifically, n-Bu, NBF, etc. n − B u 4N C
Quaternary ammonium salts such as Q are used, especially n-B
u4NCQ (tetra n-butylammonium chloride) is preferred. In addition, the polar solvent used in the present invention must be one that does not react with the starting materials, and therefore protic solvents (alcohols, carboxylic acids, etc.) or water-containing solvents are unsuitable. A polar solvent having a dielectric constant of 10 or more is preferable, specifically, 1,2-dimethoxyethane (DME).
, tetrahydrofuran (THF), polar ether solvents such as anisole, hexamethylphosphoramide (HMPA). Acetonitrile (AN). Dimethylformamide (DMF), dimethyl sulfoxide (DMS)
O), highly polar aprotic solvents such as propylene carbonate (pc), etc. are preferably used, and 1,2-dimethoxyethane is particularly preferred.

For example, tetra-n-butylammonium chloride is used as the supporting electrolyte in 1,2-dimethoxyethane (DME).
) is used as a polar solvent, the preferred mixing ratio is a saturation concentration of about 0.02 mon/fi. In the electrolytic electrode of the present invention, the anode is made of pure aluminum or an aluminum alloy such as A1050, pure magnesium or a magnesium alloy such as A231, and the cathode is made of the same material as the above-mentioned anode or platinum, cadmium, etc.
Use conductive materials that are stable under electrolytic conditions, such as metals such as mercury and lead, and carbon.

In the synthesis method of the present invention, electrolysis is performed in a dry atmosphere, and polysilane corresponding to the starting material is obtained in an electrolytic solution in a dissolved and/or precipitated state.

The current density at this time is preferably 0.1 to 1000 m
A/d, more preferably l-100mA/d. Generally, at current densities lower than the lower limit of the above range, the cathode potential is in the residual current region, so reduction of the starting material either does not occur at all, or even if it occurs, the current efficiency is drastically reduced, and at current densities higher than the upper limit, Reactions (reduction of the solvent and/or supporting electrolyte) occur together, leading to a decrease in current efficiency, and reductive decomposition of the target product polysilane dissolved in the electrolyte occurs, resulting in lower yield and selectivity. rate,
Both are unfavorable because the degree of polymerization decreases in both cases. If a diaphragm is not used in the electrolytic cell as in the present invention, if the anode is made of a CQ-resistant material (such as Pt.Ru), the rigid chlorine ions will be CQ-resistant at the anode. is further oxidized to C
Since a2 is re-reduced to chloride ions at the cathode, not only is the by-product chloride ion not treated, but the current efficiency is reduced and the electrolytic reductive polymerization itself of the dichloroorganosilane as a raw material is significantly hindered. In addition, CQ generated at the anode.
oxidation and chlorination are also serious problems. On the other hand, if a normal metal (such as Zn.CU) that does not have resistance (II) is used for the anode, CQ, will not be generated and will become chloride, but reduction of metal ions will occur at the cathode, and the treatment of CI2- Not only does it reduce the current efficiency, but it also prevents the polymerization of the M material.In the present invention, since an aluminum or magnesium electrode is used as the anode, the current efficiency decrease due to metal precipitation at the cathode as described above is also avoided. <.CQ1 is A
ffi C j1. Alternatively, it can be removed as a precipitate of MgCQ. That is, during the electrolysis in the present invention, the following reaction occurs at the cathode: R, . "AQCQ3 33 For magnesium, n -Mg+nCI2-YS"MgCa. 22 A reaction occurs. On the other hand, since the oxidation potential of the raw material dichloroorganosilane or the polysilane produced is higher than the oxidation potential of these reactions, decomposition of the raw materials and products does not occur. Therefore, although the aluminum or magnesium electrode of the anode wears out as a sacrificial electrode, it is effective in terms of processing by-product chlorine. On the other hand, by using aluminum or magnesium electrodes for both the anode and cathode, and reversing the polarity at regular intervals (preferably 0.1 to 10 hours), A fi C Q or MgCQ attached to the anode electrode is removed. , the electrode-attached surface of the layer becomes a reduced state at the electrode, which serves as a cathode with reversed polarity, and is easily detached. Therefore, in addition to the treatment of by-product chlorine, the activity of the electrode continues without decreasing, and as a result, there is virtually no decrease in the current efficiency of the electrode reaction in the target reaction. Further, the temperature condition is preferably -20 to 80°C. At this time, the energization amount is the theoretical amount (CQlmon in the starting material
It is preferably 1/10 to 10/1 of the IF), and particularly preferably 0.5/1 to 1.571 of the theoretical amount. In general, if the amount is less than the lower limit of the above range, the desired polysilane cannot be obtained satisfactorily, and if the current is applied in excess of the upper limit, reductive decomposition of the formed polysilane occurs, which is not preferable. As described above, by the above-mentioned electrolysis in the present invention, polysilanes such as polydimethylsilane and polymethylphenylsilane can be obtained depending on the starting materials subjected to electrolysis. In addition, by arbitrarily selecting electrolytic conditions such as current density and amount of current, the degree of polymerization of the resulting polysilane can be determined by
is possible. Next, the obtained polysilane is separated from the electrolyte solution after electrolysis, purified, and isolated. The method is not particularly limited, and a suitable method is selected depending on the type of polysilane to be used, the amount of treatment, etc.
An example of a preferred method is shown below. First, if any precipitate is present in the electrolyte after electrolysis, filter it out and remove the supporting electrolyte from the electrolyte. The methods used include a separation method in which an excess amount of n-hexane, xylene, toluene, benzene, etc. is added to precipitate and filtration, or a separation method by chromatography using a silica gel-CH, (112 column). Preferably. Next, the electrolytic solution from which the supporting electrolyte has been removed is concentrated by vacuum distillation, etc., and then purified by ff/# chromatography (TLC), column chromatography, etc. as necessary, and the isolated vorisilane is purified. The polysilane obtained in this way is .SiC fiber, S
It is useful as a precursor for iC or the like, a polymerization initiator for polystyrene, etc.

[Examples] The present invention will be explained in more detail below based on Examples. Example 1 Tetra n-butylammonium chloride was added as a supporting electrolyte at a concentration of 0.02 moQ/12.
．． 50 mJ1 of 2-dimethoxyethane and 1.2 mQ (10 mmoQ) of dichlorodimethylsilane as starting material
was injected into a beaker-type electrolytic cell without a diaphragm having a pure AQ plate (25 mm x 40 mm) as the cathode and anode, and in a dry atmosphere at a current density of 60 mA/am and a temperature of 10 °C, 70% of the theoretical amount (1350 °C) was added. I turned on electricity and performed electrolysis.
After the electrolysis was completed, the electrolyte was passed through a 04 glass filter to separate the precipitate deposited during the electrolysis. The precipitate was washed with methanol and acetone, dilute hydrochloric acid, and distilled water to remove the solvent, supporting salt, aluminum chloride, and low molecular weight products, and then dried under reduced pressure. The yield of the obtained insoluble polydimethylsilane was 20%, and the current efficiency was 29%. When this insoluble polydimethylsilane was analyzed by examining its infrared absorption spectrum and ultraviolet absorption spectrum, it was found that the degree of polymerization of this insoluble polysilane was equivalent to that of commercially available polydimethylsilane obtained by the sodium condensation method, and the degree of polymerization was 20. It was more than that. Example 2 In Example 1, when electrolysis was carried out by reversing the polarity of the electrode every hour, the yield of insoluble boridimethylsilane obtained was 40%, and the current efficiency was 57%. Furthermore, the degree of polymerization was comparable to that of Example 1. Example 3 As a supporting electrolyte, 24mM dichlorodimethylsilane (200 m m
on) was used in the same equipment as in Example 1, and as in Example 2, the polarity of the electrodes was reversed every 30 minutes and 10% of the theoretical amount of current (40 mF = 3860 C) was applied. The product was passed through the mouth under a dry atmosphere and purified according to Example 1. As a result, the insoluble polydimethylsilane 0.46. I got it. The current efficiency was 40%. Example 4 Dichlorodiphenylsilane was used as the starting material, and A was used as the anode.
Q alloy A1050. Example 1 except that platinum was used for the cathode
Electrolysis was performed according to the method. The yield of the obtained insoluble octaphenyltetracyclosilane (phs1)* was 15%.
, the current efficiency was 21%. After concentrating the oral fluid under reduced pressure to remove the solvent, cyclohexane was added with a small amount of n-hexane and methanol, stirred well to dissolve and separate the layers, and the hexane layer from which the supporting salt and low molecular weight products were removed was concentrated under reduced pressure. As a result, a solid linear perphenyl polysilane with a degree of polymerization of about 15 was obtained. The yield of this polymer was 30% and the current efficiency was 43%.

When the molecular weight of this product was compared with that of linear perphenylpolysilane obtained by chemical synthesis using metallic sodium by GPC (gel permeation chromatography) using THA as a solvent, it was found that the molecular weight was the same or slightly improved. was recognized.

Example 5 Electrolysis was carried out according to Example 1, except that dichloromethylphenylsilane was used as the starting material. As a result, the yield of the obtained soluble chain polymer with a degree of polymerization of about 20 was 5.
0%, and the current efficiency was 71%. Example 6 Tetra n-butylammonium chloride was added as a supporting electrolyte at a concentration of 0.02 mol/fl.
40 mQ of 2-dimethoxyethane, and 0.24 mQ (2 mmol) of dichlorodimethylsilane as a starting material,
A pure PT plate (20 m x 30 mm) was used as the cathode,
A pure magnesium plate (20 m x 30 m+) was poured into a beaker-type electrolytic cell without a diaphragm having an anode, and a current density of 3. Electrolytic reduction was performed by applying a theoretical amount of current (386 c) at 0 mA/cm2 and a temperature of 20°C. After the electrolysis was completed, the electrolytic solution was passed through a 04 glass filter to separate the precipitate deposited during the electrolysis.

The precipitate was washed with methanol and acetone, dilute hydrochloric acid, and distilled water to remove solvent, supporting salt, magnesium chloride, and low molecular weight products.

The yield of insoluble boridimethylsilane having the same degree of polymerization as in Example 1 was 30%. Example 7 50 mfl of electrolyte used in Example 6, 1.2 m of starting material
Electrolytic reduction was carried out by using pure magnesium plates (25 m x 40 m) at both electrodes, rotating the electrodes every 30 minutes, and applying current to 70% of the theoretical amount (1350 c). The yield of the obtained insoluble polydimethylsilane having the same degree of polymerization as in Example 1 was 35%, and the current efficiency was 50%.

[Effects] As described above, the present invention uses a simple electrolytic cell that does not require a diaphragm, can obtain polysilane with a high degree of polymerization in good yield, and also eliminates the influence of by-product chlorine on the reaction. The device has no adverse effects on the environment and is extremely useful industrially.

Claims (1)

[Claims] 1. Dichloroorganomonosilane as a starting material is mixed with a supporting electrolyte to form an electrolytic solution, the anode is made of pure aluminum, an aluminum alloy, pure magnesium, or a magnesium alloy, and the cathode is made of pure aluminum or aluminum. It is characterized by conducting electrolysis in an electrolytic cell without using a diaphragm using an electrolytic electrode made of an alloy, pure magnesium, a magnesium alloy, or other electrode material, and separating, purifying, and isolating the resulting product. Method for synthesizing polysilane. 2. Dichloroorganomonosilane as a starting material is mixed with a polar solvent containing a supporting electrolyte to form an electrolytic solution, and the anode is made of pure aluminum, aluminum alloy, pure magnesium, or magnesium alloy, and the cathode is made of pure aluminum or aluminum alloy. , characterized in that electrolysis is carried out in an electrolytic cell without using a diaphragm using an electrolytic electrode made of pure magnesium, a magnesium alloy, or other electrode material, and the resulting product is separated, purified, and isolated. Method for synthesizing polysilane. 3. Mix dichloroorganomonosilane as a starting material with a supporting electrolyte to form an electrolytic solution, and use electrolytic electrodes made of pure aluminum, aluminum alloy, pure magnesium, or magnesium alloy for both the anode and cathode in an electrolytic cell without using a diaphragm. A method for synthesizing polysilane, which is characterized by performing electrolysis while reversing the polarity of both poles at regular intervals, and separating, purifying, and isolating the resulting product. 4. Dichloroorganomonosilane as a starting material is mixed with a polar solvent containing a supporting electrolyte to form an electrolytic solution, and a diaphragm is formed using electrolytic electrodes made of pure aluminum, aluminum alloy, pure magnesium, or magnesium alloy for both the anode and cathode. A method for synthesizing polysilane, which comprises performing electrolysis in an unused electrolytic cell while reversing the polarity of both poles at regular intervals, and separating, purifying, and isolating the resulting product. 5. The method for synthesizing polysilane according to any one of claims 1 to 4, wherein the dichloroorganomonosilane is dichlorodimethylsilane, dichloromethylphenylsilane, or dichlorodiphenylsilane.