Method for producing cyclic silane compound

Abstract

This method for producing a cyclic silane compound comprises a step for obtaining a cyclic silane compound by subjecting a chain polysilane compound that has a repeating unit represented by formula (1) to a decomposition reaction in a solution that contains sodium metal and a lithium salt. In this method for producing a cyclic silane compound, the chain polysilane compound is not completely dissolved in 1-chloronaphthalene at a temperature of 240°C or less. (In the formula, R1 and R2 each independently represent a hydrogen atom or a hydrocarbon group.)

Description

Method for producing cyclic silane compounds

[0001] The present invention relates to a method for producing a cyclic silane compound.

[0002] Silicon carbide fiber has excellent heat resistance and oxidation resistance, even in high-temperature atmospheres of over 1,000 degrees Celsius. Taking advantage of these properties, silicon carbide fiber is expected to be used in the nuclear and aerospace fields.

[0003] Silicon carbide fibers are obtained by spinning, infusibilizing, and calcining a precursor organosilicon polymer compound such as polycarbosilane. Because oxygen-containing silicon carbide fibers decompose at high temperatures, in order to obtain ultra-heat-resistant silicon carbide fibers, it is necessary to suppress the introduction of oxygen atoms into the organosilicon polymer compound that forms the fiber. Therefore, ultra-heat-resistant silicon carbide fibers are produced by using organosilicon polymer compounds with low oxygen content and adopting a method that does not introduce oxygen during infusibilization. Polycarbosilane with an oxygen content of approximately 0.1% by weight can be obtained from cyclic silane compounds such as dodecamethylcyclohexasilane. Therefore, cyclic silane compounds are useful as raw materials for organosilicon polymer compounds that serve as precursors to silicon carbide fibers.

[0004] Various methods are known for producing a cyclic silane compound. For example, Patent Document 1 discloses a method for producing a cyclic silane compound by adding a silane monomer compound dropwise to a mixed solution of THF and sodium dispersion under ice cooling, polymerizing the mixture to obtain a chain polysilane compound, adding naphthalene, and heating the chain polysilane compound to reflux.

[0005] Patent Document 2 discloses a method for producing a cyclic silane compound by adding a silane monomer compound dropwise to a mixed liquid of THF, sodium dispersion, and lithium chloride under ice cooling, followed by polymerization reaction.

[0006] Patent Document 3 discloses a method for producing a cyclic silane compound by reacting a linear polysilane having a degree of polymerization of 10 to 100, an alkali metal, and an aromatic hydrocarbon capable of forming a complex with the alkali metal in an ether solvent. In the examples, naphthalene is used as the aromatic hydrocarbon.

[0007] Japanese Patent Application Laid-Open No. 2019-156792 International Publication No. 2020 / 045614 Japanese Patent Application Laid-Open No. 54-130541

[0008] However, when producing cyclic silanes by polymerizing a silane monomer compound as in Patent Document 2, it is necessary to use a stoichiometric amount of metallic sodium. As a result, a certain amount of by-products such as sodium chloride is produced. From the viewpoint of further improving production efficiency, it is desirable to be able to reduce the amount of by-products such as sodium chloride produced.

[0009] Furthermore, since naphthalene used in Patent Documents 1 and 3 is a water-insoluble solid organic compound, it cannot be removed by washing with water, and purification tends to be complicated. Therefore, it is desired that the purification can be performed by washing with water alone (to simplify the purification).

[0010] It is also desirable to further increase the yield of cyclic silane compounds.

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a cyclic silane compound, which can produce a cyclic silane compound in high yield with simple purification while reducing the amount of by-products produced.

[0012] The present invention relates to the following method for producing a cyclic silane compound.

[0013] [1] A method for producing a cyclic silane compound, comprising the step of subjecting a chain polysilane compound having a repeating unit represented by the following formula (1) to a decomposition reaction in a solution containing metallic sodium and a lithium salt to obtain a cyclic silane compound, wherein the chain polysilane compound is not completely dissolved in 1-chloronaphthalene at a temperature of 240°C or less: (In the formula, R １ and R ２each independently represent a hydrogen atom or a hydrocarbon group. [2] The method for producing a cyclic silane compound according to [1], wherein the chain polysilane compound is insoluble in 1-chloronaphthalene at a temperature of 250°C or less. [3] The method for producing a cyclic silane compound according to [1] or [2], wherein the step of obtaining the cyclic silane compound is carried out by heating the chain polysilane compound in the solution. [4] The method for producing a cyclic silane compound according to [3], wherein the heating is carried out at 40°C or higher. [5] The method for producing a cyclic silane compound according to any one of [1] to [4], wherein the content of the lithium salt in the solution is 2.0 mmol or more relative to 1 g of the chain polysilane compound.

[0014] According to the present invention, it is possible to provide a method for producing a cyclic silane compound, which can produce a cyclic silane compound in high yield even with simple purification while extremely reducing the amount of by-products produced.

[0015] FIG. 1A is a photograph showing the results of the dissolution test of silane compound A, and FIG. 1B is a photograph showing the results of the dissolution test of silane compound B.

[0016] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0017] 1. Method for Producing a Cyclic Silane Compound A method for producing a cyclic silane compound according to one embodiment of the present invention includes a step of subjecting a chain polysilane compound to a decomposition reaction in a solution containing metallic sodium and a lithium salt to obtain a cyclic silane compound.

[0018] Specifically, a cyclic silane compound can be obtained through a step of preparing a solution containing a chain polysilane compound, metallic sodium, and a lithium salt, and a step of decomposing the chain polysilane compound in the solution.

[0019] 1-1. Preparation Step A solution containing a chain polysilane compound, metallic sodium, and a lithium salt is prepared.

[0020] (Chain Polysilane Compound) The chain polysilane compound has a repeating unit represented by the following formula (1).

[0021] R in the formula １ and R ２ each independently represents a hydrogen atom or a hydrocarbon group.

[0022] Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, and an aryl group.

[0023] R １ and R ２ can be a side chain in a cyclic silane compound. Therefore, it is sufficient to select R according to the cyclic silane compound to be synthesized. １ and R ２ is, for example, preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrocarbon group, even more preferably an alkyl group, and even more preferably a methyl group.

[0024] In addition, in a chain polysilane compound, the groups bonded to the silicon atoms at both molecular terminals may be hydrogen atoms, hydrocarbon groups, alkoxy groups, or hydroxy groups. Examples of alkoxy groups include methoxy groups and ethoxy groups. Because alkoxy groups and hydroxy groups have a large difference in electronegativity from silicon atoms, they are likely to cause intramolecular polarization within the chain polysilane compound and may also be likely to function as leaving groups. Therefore, the groups at both molecular terminals of the chain polysilane compound may be alkoxy groups or hydroxy groups.

[0025] Specifically, specific examples of the chain polysilane compound include compounds represented by the following formula (2).

[0026] In formula (2), R １ and R ２ is R in formula (1). １ and R ２ It is the same as: X １ and X ２ are each a hydrogen atom, a hydrocarbon group, an alkoxy group, or a hydroxy group, and examples thereof are an alkoxy group or a hydroxy group. １is a degree of polymerization such that the compound represented by formula (2) is not completely dissolved at a temperature of 240°C or less in a solubility test in 1-chloronaphthalene described below, and is, for example, an integer of 17 or more, preferably 20 or more, and more preferably 30 or more.

[0027] The number average molecular weight of the chain polysilane compound is preferably high from the viewpoint of increasing the yield of the cyclic silane compound. The number average molecular weight of the chain polysilane compound is, for example, preferably 950 or more, more preferably 1100 or more, and even more preferably higher than 1700. If the number average molecular weight is 1100 or more, the amount of intermediates produced by the decomposition reaction can be increased, thereby further increasing the yield of the cyclic silane compound. The upper limit of the number average molecular weight is not particularly limited, but can be, for example, 650,000 or less from the viewpoint of shortening the reaction time.

[0028] The number average molecular weight of a chain polysilane compound can be evaluated using the temperature at which it dissolves in 1-chloronaphthalene as an index. For example, the higher the number average molecular weight of a chain polysilane compound, the higher the temperature at which it dissolves in 1-chloronaphthalene. Since the chain polysilane compound used in this embodiment preferably has a high number average molecular weight, it is also preferable that the temperature at which it dissolves in 1-chloronaphthalene is high. Specifically, it is preferable that the chain polysilane compound does not completely dissolve in 1-chloronaphthalene at temperatures of 240° C. or lower, and does not completely dissolve in 1-chloronaphthalene even at temperatures of 250° C. or lower.

[0029] The temperature at which the chain polysilane compound dissolves in 1-chloronaphthalene can be confirmed by the following method. A glass capillary with an inner diameter of 1.0 mm is filled with approximately 3 to 5 mm of the chain polysilane compound and 5 to 10 mm of 1-chloronaphthalene (approximately twice the amount of the chain polysilane compound), and then the capillary is purged with argon gas and sealed. This is then placed in a melting point measuring device (B-545, manufactured by Buchi) whose internal temperature has been preheated to 240°C, and allowed to stand for 5 minutes. After standing, the state of the chain polysilane compound filled in the glass capillary is visually confirmed to determine whether it has completely dissolved. By repeating this procedure at different temperatures, the temperature at which the chain polysilane compound completely dissolves can be identified.

[0030] The chain polysilane compound is a white solid. Therefore, if even a portion of the compound remains undissolved, the remaining state of the white solid can be visually confirmed. Therefore, whether or not the compound is completely dissolved can be determined by visually checking whether or not the white solid remains and whether the solution is transparent. For example, at 250°C in FIG. 1A (described later), a portion of the white solid remains undissolved, whereas at 250°C in FIG. 1B (described later), the white solid is completely dissolved. Whether or not the compound is completely dissolved can also be confirmed by the transmittance or turbidity of the solution or the whiteness obtained by image processing of the solution image.

[0031] The chain polysilane compound can be identified using a Fourier transform infrared spectrophotometer and a microscopic Raman spectrophotometer. In the IR spectrum measured with a Fourier transform infrared spectrophotometer, ―１ , 831 cm ―１ , 1246 cm ―１ , 1400 cm ―１ , 2892 cm －１ , 2950 cm －１ A peak was observed at 482 cm in the Raman spectrum measured with a microscopic Raman spectrometer. ―１ If a peak is observed at , it can be determined that the compound contained in the sample has the repeating unit represented by the above formula (1) (is a chain polysilane compound). ２９ It can be confirmed by Si CP / MAS NMR that it has a chain structure with terminals.

[0032] The chain polysilane compound may be a synthesized compound or a commercially available product.

[0033] (Metallic sodium) Metallic sodium can function as a catalyst for the decomposition reaction. The form of metallic sodium is not particularly limited, but from the viewpoint of increasing the surface area and enhancing the reactivity, it is preferably processed into a sodium dispersion.

[0034] In this specification, sodium dispersion (SD) refers to metallic sodium dispersed in electrical insulating oil or aromatic hydrocarbon. Examples of electrical insulating oil include aliphatic hydrocarbons such as liquid paraffin and mineral oil, and examples of aromatic hydrocarbons include toluene and xylene.

[0035] From the viewpoints of reactivity and safety, the average particle size of metallic sodium is preferably 1 to 30 μm, more preferably 2 to 10 μm, and even more preferably 3 to 5 μm. The average particle size can be measured using a laser diffraction particle size distribution measuring device.

[0036] From the viewpoint of the yield of the cyclic silane compound, the amount of metallic sodium contained in the solution is preferably 0.1 to 120 mmol per 1 g of the chain polysilane compound. When the metallic sodium content is 0.1 mmol or more, the decomposition reaction of the chain polysilane compound is more likely to proceed. When the metallic sodium content is 120 mmol or less, the amount of unreacted metallic sodium can be reduced while the reaction is allowed to proceed sufficiently. Furthermore, when the chain polysilane compound is dichlorodimethylpolysilane or the like, the amount of by-products such as sodium alkoxide produced can also be reduced. From the viewpoint of allowing the reaction to proceed sufficiently and further reducing the amount of unreacted metallic sodium, the amount of metallic sodium is more preferably 0.5 to 80 mmol, even more preferably 0.5 to 20 mmol, and particularly preferably 1.0 to 10.0 mmol per 1 g of the chain polysilane compound.

[0037] (Lithium Salt) The lithium salt mainly contributes to stabilizing an intermediate produced in the decomposition reaction. The lithium salt may be an inorganic salt or an organic salt.

[0038] Inorganic salts include halides and salts of inorganic acids. Examples of halides include lithium chloride, lithium bromide, lithium iodide, and lithium fluoride. Examples of inorganic acid salts include lithium carbonate, lithium bicarbonate, lithium nitrate, lithium nitrite, lithium sulfate, and lithium sulfite.

[0039] Examples of organic salts include carboxylates, sulfonates, and salts of phenols. Examples of carboxylates include lithium acetate, lithium formate, and lithium citrate. Examples of sulfonates include lithium methanesulfonate, lithium benzenesulfonate, and lithium p-toluenesulfonate. Examples of phenol salts include lithium phenoxide, lithium salicylate, and lithium cresol salt.

[0040] Among these, inorganic salts are preferred, and halides are more preferred. Among halides, lithium chloride and lithium bromide are preferred, and lithium chloride is more preferred. The lithium salt may be used alone or in combination.

[0041] The molar ratio of the lithium salt to the metallic sodium contained in the solution (lithium salt / metallic sodium) varies depending on the metallic sodium content, but is preferably 0.01 or more, more preferably 0.06 or more, even more preferably greater than 1.0, and most preferably 1.3 or more. When the molar ratio is 0.06 or more, it is easy to moderately stabilize the intermediate produced in the decomposition reaction of the chain polysilane compound, and it is easy to further increase the yield of the cyclic silane compound. Furthermore, even if the metallic sodium content is low, it is easy to maintain the yield of the cyclic silane compound. On the other hand, the molar ratio of lithium is preferably 10.0 or less, more preferably 6.0 or less, even more preferably 3.0 or less, and most preferably 2.0 or less. When the molar ratio is 3.0 or less, decomposition of the produced cyclic silane compound can be further suppressed. Thus, by setting the molar ratio of the lithium salt in the solution within the above range, the yield of the cyclic silane compound can be further increased.

[0042] The amount of lithium salt contained in the solution may be within the range of the molar ratio, and is preferably 1.0 mmol or more, more preferably 1.5 mmol or more, and even more preferably 2.0 mmol or more, relative to 1 g of the chain polysilane compound. The upper limit of the amount of lithium salt is, for example, preferably 9.0 mmol or less, more preferably 5.0 mmol or less.

[0043] The amounts of metallic sodium, lithium salt, and molar ratios thereof are as described above, but from the viewpoint of further increasing reactivity and yield, it is preferable that these quantitative relationships are simultaneously satisfied. For example, per gram of chain polysilane compound, the amount of metallic sodium contained in the solution is preferably 0.1 to 120 mmol, more preferably 0.5 to 20 mmol; the amount of lithium salt is preferably 1.0 to 9.0 mmol, more preferably 2.0 to 5.0 mmol; and the molar ratio (lithium salt / metallic sodium) is preferably 0.01 or greater, more preferably greater than 1.0.

[0044] (Solvent) The solution preferably further contains a solvent. The solvent may be any solvent that can disperse metallic sodium and disperse or dissolve lithium salt.

[0045] Examples of the solvent include aprotic polar solvents. Examples of the aprotic polar solvent include tetrahydrofuran (THF), 1,2-dimethoxyethane, 4-methyltetrahydropyran, bis(2-methoxyethyl)ether, 1,4-dioxane, and cyclopentyl methyl ether. These solvents may be used alone or as a mixture of two or more. Among these, tetrahydrofuran, 4-methyltetrahydropyran, and cyclopentyl methyl ether are preferred, and tetrahydrofuran is more preferred.

[0046] (Mixing) The solution can be prepared by mixing the components. The mixing method and procedure are not particularly limited, but for example, the solution can be obtained by adding metallic sodium, a lithium salt, and a chain polysilane compound to a solvent while stirring, followed by stirring and mixing.

[0047] In this case, metallic sodium is preferably added as a dispersion (SD) in the above-mentioned electrical insulating oil or aromatic hydrocarbon. The content of metallic sodium in the sodium dispersion to be added is not particularly limited, but from the viewpoint of safety, it is preferably 20 to 45 mass%.

[0048] 1-2. Decomposition Reaction Step The chain polysilane compound is decomposed in the solution prepared above. The decomposition reaction may be carried out at room temperature or under heating.

[0049] That is, the temperature of the solution during the decomposition reaction can be from 20°C to the reflux temperature. The reflux temperature corresponds to the temperature of the solution when it reaches a reflux state at normal pressure. From the viewpoint of obtaining a cyclic silane compound in a higher yield, it is preferable to carry out the decomposition reaction under heating, that is, by heating the chain polysilane compound in the solution. In this case, the temperature of the solution is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. However, from the viewpoint of suppressing decomposition of the reaction product, the upper limit of the solution temperature is preferably 200°C or lower.

[0050] The heating method is not particularly limited, and may be, for example, a method in which the solution is placed in an atmosphere at a predetermined temperature, or a method in which the solution is heated by a heater, a water bath, an oil bath, electromagnetic waves, or the like.

[0051] The reaction time refers to the time elapsed from when the entire amount of the chain polysilane compound as the raw material is added and when the target reaction temperature is reached. The reaction time depends on the temperature of the solution, but when the reaction is carried out under heating, it is preferably, for example, from 1 hour to 35 hours, and more preferably from 3 hours to 10 hours.

[0052] 1-3. Operation According to the above embodiment, a cyclic silane compound is produced by decomposing a chain polysilane compound in the presence of a predetermined catalyst. This allows for a higher yield of the cyclic silane compound than conventional methods involving the polymerization of silane monomers. Furthermore, the chain polysilane compound contains an extremely low content of functional groups that react with metallic sodium, allowing for a reduced amount of metallic sodium used as a catalyst, thereby significantly reducing the amount of by-products such as sodium alkoxides produced.

[0053] Although the specific reaction mechanism is unclear, it is speculated as follows. In conventional methods for producing cyclic silane compounds by polymerizing silane monomers, the substituents (e.g., halogen atoms) contained in the silane monomers are eliminated by the action of metallic sodium, and the silane monomers undergo chain polymerization to produce the cyclic silane compounds. This requires a large amount of metallic sodium, which tends to increase the amount of by-products. Furthermore, it is difficult to further increase the yield of the cyclic silane compounds.

[0054] In contrast, in the method of decomposing a chain polysilane compound as in this embodiment, the molecular terminal groups (e.g., alkoxy groups) of the chain polysilane compound are eliminated by the action of metallic sodium, or the silicon-silicon bonds are cleaved by the action of metallic sodium, resulting in a change in the electronic state and the generation of active sites. Subsequently, these active sites cause the molecular chain to break at predetermined intervals and undergo cyclization, thereby producing a cyclic silane compound. The generated active sites are stabilized by a lithium salt or the like, making them less likely to be deactivated and maintaining a moderate level of reactivity, which can be improved by adding a lithium salt or the like. Thus, the chain polysilane compound has fewer elimination groups per molecule, and the amount of metallic sodium required for the decomposition reaction is also small, thereby reducing the amount of by-products. In addition, stabilizing the active sites with a lithium salt or the like can also increase the yield of the cyclic silane compound.

[0055] Furthermore, since there is no need to use a water-insoluble solid organic compound such as naphthalene, the purification can be carried out simply by washing with water, and the purification can be carried out easily.

[0056] 2. Cyclic Silane Compound The cyclic silane compound obtained by the method for producing a cyclic silane compound according to this embodiment has, for example, a structure represented by the following formula.

[0057] R in formula (3) １ and R ２ is R in formula (1). １ and R ２ are identical to

[0058] n ２ is an integer of 3 or more. ２ is preferably 3 to 10, more preferably 5 to 7, and even more preferably 6.

[0059] Cyclic silane is R １ and R ２ Examples include decamethylcyclopentasilane, dodecamethylcyclohexasilane, and tetradecamethylcycloheptasilane.

[0060] The resulting cyclic silane compound contains n ２ It is also possible to include multiple types of cyclic silane compounds with different n ２ The yield of the cyclic silane compound (6-membered ring) in which is 6 is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. The yield of the cyclic silane compound can be determined by analyzing the reaction product by gas chromatography. The measurement conditions can be the same as those in the examples described below.

[0061] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0062] 1. Materials (1) Silane Compounds Silane Compound A: Linear polydimethylsilane (solid at room temperature, number average molecular weight of more than 1700, R of formula (1) １ , R ２ = methyl group) Silane compound B: linear polydimethylsilane (solid at room temperature, number average molecular weight 1100 to 1700, R of formula (1) １ , R ２= methyl group) Silane compound C: dichlorodimethylsilane (monosilane, liquid at room temperature, molecular weight 129)

[0063] The dissolution temperatures of these compounds in 1-chloronaphthalene were measured.

[0064] (Measurement of Dissolution Temperature) A glass capillary with an inner diameter of 1.0 mm was filled with a silane compound to a depth of approximately 3 to 5 mm, and 1-chloronaphthalene was filled to a depth of approximately 5 to 10 mm (approximately twice the amount of the silane compound), purged with argon gas, and sealed. This was placed in a melting point measuring instrument (B-545, manufactured by Buchi) whose internal temperature had been preheated to 240°C or 250°C, and allowed to stand for 5 minutes. After standing, the state of the silane compound filled in the glass capillary was visually confirmed. The results of the dissolution test for silane compound A are shown in Figure 1A, and the results of the dissolution test for silane compound B are shown in Figure 1B.

[0065] As a result, silane compound A did not completely dissolve at either 240°C or 250°C (see Figure 1A). On the other hand, silane compound B did not completely dissolve at 240°C, but completely dissolved at 250°C (see Figure 1B). These results also correspond to the fact that silane compound A has a higher number average molecular weight than silane compound B.

[0066] (2) Metallic sodium: Sodium dispersion (25% by weight sodium dispersion, average particle size 3.40 μm)

[0067] (3) Lithium salts Lithium chloride (LiCl) Lithium bromide (LiBr)

[0068] (4) Solvent: tetrahydrofuran (THF)

[0069] 2. Preparation of Cyclic Silane Compound [Example 1] A 200 mL four-neck flask, the inside of which had been purged with argon, was charged with 0.98 g of silane compound A (chain polysilane), 20.4 mL of tetrahydrofuran (THF) per 1 g of the silane compound, sodium dispersion (25.72 mass % sodium dispersion) as metallic sodium in an amount of 1.6 mmol (Na) per 1 g of the silane compound, and lithium chloride as a lithium salt in an amount of 2.23 mmol per 1 g of the silane compound, followed by stirring and mixing to prepare a solution.

[0070] The resulting solution was stirred at a reflux temperature of 68° C. for 5 hours while being heated in an oil bath to allow the reaction to occur.

[0071] Examples 2 to 10, Comparative Examples 3 and 4 Solutions were prepared and reacted in the same manner as in Example 1, except that one or more of the type of silane compound, the amount of tetrahydrofuran (THF) charged, the ratio of metallic sodium to lithium salt, the type and amount of lithium salt charged, and the reaction conditions were changed as shown in Table 1.

[0072] Comparative Example 1: A 500 mL four-neck flask, the inside of which had been purged with argon, was charged with 180 mL of THF and 29.90 g of a sodium dispersion (25 wt % sodium dispersion), and the mixture was stirred to prepare a mixed solution. 19.33 g of silane compound C (dichlorodimethylsilane) was dissolved in 150 mL of THF to prepare a silane compound solution.

[0073] After the mixture was cooled to 0°C with ice, 0.71 g of lithium chloride was added. The silane compound solution was added dropwise over about 5 hours with stirring under ice cooling. After the dropwise addition, the mixture was stirred for an additional 3 hours, and then reacted at room temperature for 21 hours.

[0074] Comparative Examples 2 and 5 Solutions were prepared in the same manner as in Example 1, except that silane compound C (dichlorodimethylsilane) was used and the amounts of each component were changed as shown in Table 1. The resulting solutions were then reacted in the same manner as in Example 1, except that they were stirred and reacted under the reaction conditions shown in Table 1.

[0075] The reaction products obtained in Examples 1 to 10 and Comparative Examples 1 to 5 were analyzed by gas chromatography under the following measurement conditions.

[0076] (Gas Chromatography Measurement) Apparatus: GC-2025 (Shimadzu Corporation) Column: DB1301 (Agilent Technologies), length (30 m), diameter (0.320 m), film (0.25 m) Carrier gas: He Detector: FID

[0077] The production of cyclic silanes (dodecamethylcyclohexasilane (6-membered ring), decamethylcyclopentasilane (5-membered ring), and tetradecamethylcycloheptasilane (7-membered ring)) was confirmed, and the yields of each were determined. The results are shown in Table 2.

[0078]

[0079]

[0080] As shown in Table 2, the total yield of cyclic silanes was 46.6% or less in Comparative Examples 1, 2, and 5, which used silane compound C (monomer) as a raw material. Also, the total yield was 22% or less in Comparative Examples 3 and 4, which used silane compound A (polymer) as a raw material but did not use a lithium salt.

[0081] In contrast, in Examples 1 to 9, which used silane compound A or B (polymer) and a lithium salt as raw materials, the total yield was as high as 67.5% or more. Also, it can be seen that Example 10 had a higher total yield than Comparative Examples 4 and 5.

[0082] These findings demonstrate that the decomposition reaction of a chain polysilane compound in a solution containing metallic sodium and lithium salts allows the reaction to proceed sufficiently, resulting in a high yield of cyclic silanes.

[0083] In particular, it can be seen that the total yield is further increased by setting the reaction temperature to 40° C. or higher (comparison between Examples 5 and 8, and comparison between Examples 1, 3, and 9).

[0084] It is also clear that the total yield can be further increased by setting the amount of lithium salt to 2.0 mmol or more per 1 g of the chain polysilane compound or by setting the molar ratio (lithium salt / metallic sodium) to more than 1.0 (comparison between Examples 1 and 10).

[0085] This application claims priority based on Japanese Patent Application No. 2023-113668, filed July 11, 2023, the entire contents of which are incorporated herein by reference.

[0086] According to the present invention, it is possible to provide a method for producing a cyclic silane compound that can produce a cyclic silane compound with high purity in high yield even when using a small amount of metallic sodium.

Claims

1. The method includes a step of decomposing a chain polysilane compound having a repeating unit represented by the following formula (1) in a solution containing metallic sodium and a lithium salt to obtain a cyclic silane compound, The chain polysilane compound is not completely dissolved in 1-chloronaphthalene at a temperature of 240°C or less. A method for producing a cyclic silane compound. 【Chemical 1】 (In the formula, R １ and R ２ each independently represents a hydrogen atom or a hydrocarbon group.

2. the chain polysilane compound is insoluble in 1-chloronaphthalene at a temperature of 250°C or less; A method for producing the cyclic silane compound according to claim 1.

3. the step of obtaining the cyclic silane compound is carried out by heating the chain polysilane compound in the solution; A method for producing the cyclic silane compound according to claim 1 or 2.

4. The heating is performed at 40°C or higher. The method for producing the cyclic silane compound according to claim 3 .

5. the content of the lithium salt in the solution is 2.0 mmol or more relative to 1 g of the chain polysilane compound; A method for producing the cyclic silane compound according to claim 1 or 2.

6. The amount of metallic sodium contained in the solution is 1.0 to 10.0 mmol per 1 g of the chain polysilane. A method for producing the cyclic silane compound according to claim 1 or 2.

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