Method for producing cyclic silane compound

Abstract

This method for producing a cyclic silane compound includes: a first step for obtaining a reaction liquid that contains a chain polysilane compound by polymerizing a silane compound in a mixture that contains sodium metal and an aromatic hydrocarbon solvent; and a second step for obtaining a cyclic silane compound by subjecting the reaction liquid to a decomposition reaction of the chain polysilane compound in a solution that is obtained by mixing a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon with tetrahydrofuran.

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 cyclic silane compounds. For example, Patent Document 1 discloses a method for producing a cyclic silane compound by: 1) adding a silane monomer compound dropwise to a mixture of THF and sodium dispersion under ice cooling, followed by polymerization reaction to obtain a chain polysilane compound, and 2) adding naphthalene and heating the chain polysilane compound to reflux.

[0005] Japanese Patent Application Laid-Open No. 2019-156792

[0006] However, the above-mentioned method for producing a cyclic silane compound requires the use of an expensive sodium dispersion in a stoichiometric amount or more, which results in a problem of high production costs.

[0007] In addition, sodium dispersions contain a large amount of dispersion oil for dispersing metallic sodium. Dispersion oil is a water-insoluble organic compound, and the cyclic silane compound has a high solubility in the dispersion oil, which makes separation and purification difficult.

[0008] For these reasons, it is desirable to be able to obtain cyclic silane compounds at a predetermined yield or higher without using sodium dispersion, thereby reducing production costs and facilitating separation and purification.

[0009] 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 that reduces production costs and facilitates separation and purification.

[0010] The present invention relates to the following method for producing a cyclic silane compound.

[0011] [1] A method for producing a cyclic silane compound, comprising: a first step of polymerizing a silane compound in a mixture containing metallic sodium and an aromatic hydrocarbon solvent to obtain a reaction solution containing a chain-like polysilane compound; and a second step of decomposing the chain-like polysilane compound in a solution obtained by mixing the reaction solution with a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon and tetrahydrofuran to obtain a cyclic silane compound. [2] The method for producing a cyclic silane compound according to [1], wherein in the second step, the solution contains the tetrahydrofuran and the aromatic hydrocarbon solvent, and the volume ratio of the tetrahydrofuran contained in the solution is 75% by volume or more and 95% by volume or less relative to the total volume of the aromatic hydrocarbon solvent and the tetrahydrofuran. [3] The method for producing a cyclic silane compound according to [1] or [2], wherein in the first step, the mixture is heated to a temperature equal to or higher than the melting point of the metallic sodium. [4] The method for producing a cyclic silane compound according to any one of [1] to [3], wherein the aromatic hydrocarbon solvent contains toluene, ethylbenzene, or xylene. [5] The method for producing a cyclic silane compound according to any one of [1] to [4], wherein the second step is carried out by heating the chain polysilane compound in the solution. [6] The method for producing a cyclic silane compound according to [5], wherein the heating temperature is 40°C or higher and reflux temperature or lower. [7] The method for producing a cyclic silane compound according to any one of [1] to [6], wherein biphenyl, anthracene, or naphthalene is mixed with the reaction solution as the polycyclic aromatic hydrocarbon in the second step.

[0012] According to the present invention, it is possible to provide a method for producing a cyclic silane compound that reduces production costs and facilitates separation and purification.

[0013] The sodium dispersion (SD) described above is a mixture in which solid sodium with an average particle size of 1 μm to 100 μm is dispersed in an electrical insulating oil or an aromatic hydrocarbon solvent, and has higher reactivity than metallic sodium. From the viewpoints of reactivity and safety, the average particle size of the solid sodium in the SD is preferably 2 μm to 10 μm, more preferably 3 μm to 5 μm. Examples of electrical insulating oil include aliphatic hydrocarbons such as liquid paraffin and mineral oil.

[0014] In this specification, metallic sodium refers to sodium as a single element, and its state is not particularly limited. That is, metallic sodium may be solid sodium or liquid sodium. However, in the case of solid sodium, the average particle size is more than 100 μm.

[0015] The sodium dispersion (SD) described above is a dispersion of metallic sodium particles in an electrical insulating oil or an aromatic hydrocarbon solvent, and has higher reactivity than bulk metallic sodium. Examples of the electrical insulating oil include aliphatic hydrocarbons such as liquid paraffin and mineral oil.

[0016] One possible method for synthesizing cyclic silanes without using sodium dispersions is to use bulk metallic sodium instead of sodium dispersions. However, because the specific surface area of ​​bulk metallic sodium is small, the polymerization reaction of the silane compound does not proceed easily, and the reaction yield tends to decrease.

[0017] In contrast, metallic sodium can be liquefied (made into a mixed liquid) by heating it in an aromatic hydrocarbon solvent, for example.

[0018] Liquid sodium breaks down more easily with stirring than solid sodium, and therefore has a larger specific surface area than solid sodium, which can promote the polymerization reaction of silane compounds. That is, by carrying out a first step of polymerizing a silane compound in a mixture of an aromatic hydrocarbon solvent and liquid metallic sodium to obtain a chain polysilane compound, and a second step of decomposing the chain polysilane compound in the presence of a predetermined catalyst to obtain a cyclic silane compound, it is possible to obtain a cyclic silane compound without using a sodium dispersion.

[0019] From the viewpoint of improving production efficiency, it is desirable to carry out the second step without isolating the chain polysilane compound produced in the first step (one-pot production). However, the reaction solution obtained in the first step contains a large amount of the aromatic hydrocarbon solvent used to liquefy the metallic sodium. Since the aromatic hydrocarbon solvent does not contribute to the decomposition reaction in the second step, the reaction yield is likely to decrease.

[0020] Therefore, in the present invention, tetrahydrofuran, which contributes to the decomposition reaction, is mixed with the reaction solution obtained in the first step. That is, in the second step, the decomposition reaction of the chain polysilane compound is carried out in a solution containing an aromatic hydrocarbon solvent and tetrahydrofuran, thereby increasing the reactivity and achieving a desired reaction yield.

[0021] Hereinafter, a method for producing a cyclic silane compound according to one embodiment of the present invention will be described in detail.

[0022] 1. Method for Producing Cyclic Silane Compound As described above, a method for producing a cyclic silane compound according to one embodiment of the present invention includes: a first step of polymerizing a silane compound in a mixture containing metallic sodium and an aromatic hydrocarbon solvent to obtain a reaction liquid containing a chain polysilane compound; and a second step of decomposing the chain polysilane compound in a solution obtained by mixing the reaction liquid with a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon and tetrahydrofuran to obtain a cyclic silane compound.

[0023] 1-1. First Step A silane compound is polymerized in a mixture containing metallic sodium and an aromatic hydrocarbon solvent.

[0024] The metallic sodium contained in the mixture is preferably in a molten state. The molten state refers to a state in which metallic sodium has been liquefied by, for example, heating, and differs from a state in which solid sodium is uniformly dispersed in particulate form, such as in a sodium dispersion.

[0025] The mixture can be obtained, for example, by adding metallic sodium to an aromatic hydrocarbon solvent and then heating the mixture to a temperature equal to or higher than the melting point of metallic sodium (98° C. or higher).

[0026] The mixture can be obtained, for example, by adding metallic sodium to an aromatic hydrocarbon solvent and then heating the mixture to a temperature equal to or higher than the melting point of sodium (98° C. or higher). When the metallic sodium to be added is liquid, the operation of melting the sodium can be omitted.

[0027] The metallic sodium to be added may be in the form of a single substance or may be mixed with a solvent. The solvent is not particularly limited, but is preferably the same as the solvent used in the first step.

[0028] (Aromatic Hydrocarbon Solvent) The aromatic hydrocarbon solvent may have a boiling point higher than the melting point of metallic sodium (98° C.). That is, the boiling point of the aromatic hydrocarbon solvent is preferably 100° C. or higher and 210° C. or lower, and more preferably 110° C. or higher and 170° C. or lower.

[0029] Examples of such aromatic hydrocarbon solvents include toluene, xylene, ethylbenzene, mesitylene, etc. Among them, from the viewpoint of ease of dissolving metallic sodium and ease of solvent recovery in production, toluene, xylene, and ethylbenzene are preferred, and toluene is more preferred.

[0030] The mixture may further contain other solvents as needed, examples of which include aliphatic hydrocarbon solvents such as heptane, octane, and decane.

[0031] The content of the aromatic hydrocarbon solvent in the mixture may be such that the resulting linear polysilane is sufficiently stirred and dispersed in the solvent. For example, the content of the aromatic hydrocarbon solvent in the mixture is preferably 1.0 part by mass or more per 10 parts by mass of the silane compound. When the content of the aromatic hydrocarbon solvent is 1.0 part by mass or more, the volume fraction of metallic sodium decreases, thereby making it possible to further reduce the average droplet size, increase the specific surface area of ​​sodium, and further enhance the reactivity of the silane compound. When the content of the aromatic hydrocarbon solvent is 25.0 parts by weight or less, the concentration of the silane compound in the system increases, making it easier to promote the reaction in the second step. From the same viewpoint, the content of the aromatic hydrocarbon solvent in the mixture is more preferably 3.0 parts by mass or more and 16.0 parts by mass or less per 10 parts by mass of the silane compound.

[0032] The content of the aromatic hydrocarbon solvent in the mixture relative to 10 parts by mass of metallic sodium is preferably 2.5 parts by mass or more and 60.0 parts by mass or less, and more preferably 6.0 parts by mass or more and 40.0 parts by mass or less.

[0033] (Metallic Sodium) Metallic sodium can function mainly as a reactant in the polymerization reaction.

[0034] In the mixture, the molar equivalent of metallic sodium relative to each functional group of the alkoxy group or halogen atom of the silane compound is preferably 1.00 eq. or more and 1.80 eq. or less. When the molar equivalent of metallic sodium is 1.00 eq. or more, the rate of the polymerization reaction of the silane compound in the first step can be further increased. When the molar equivalent of metallic sodium is 1.80 eq. or less, the proportion of sodium remaining unreacted can be further reduced. From the same viewpoint, the molar equivalent of metallic sodium in the mixture is more preferably 1.05 eq. or more and 1.25 eq. or less.

[0035] (Silane Compound) Next, a silane compound is added to the mixture. The silane compound is preferably a compound represented by the following formula (1).

[0036] In formula (1), X １ and X ２ Each of X represents an alkoxy group or a halogen atom. Examples of the alkoxy group include a methoxy group and an ethoxy group. Examples of the halogen atom include a chlorine atom, a bromine atom, and an iodine atom. These have a large difference in electronegativity with silicon and tend to cause intramolecular polarization in the silane compound, making them highly reactive and a substituent that functions as a leaving group in the reaction. Among these, X １ and X ２ From the viewpoint of the reactivity of the silane compound, is preferably a halogen atom, more preferably a chlorine atom.

[0037] R １ and R ２ is a hydrogen atom or a hydrocarbon group. １ and R ２ is preferably a hydrocarbon group, more preferably an alkyl group having 1 to 6 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0038] n １ is an integer of 1 or greater. １ is preferably 1 or 2, and more preferably 1, from the viewpoint of increasing the reactivity of the silane compound.

[0039] Examples of the compound represented by formula (1) include dichlorodimethylsilane, dichlorodiethylsilane, dichlorodipropylsilane, dichlorodibutylsilane, dichlorodipentylsilane, dichlorodihexylsilane, dibromodimethylsilane, dibromodiethylsilane, dibromodipropylsilane, dibromodibutylsilane, dibromodipentylsilane, dibromodihexylsilane, and dichlorotetramethyldisilane. Among these, dichlorodimethylsilane is preferred. The silane compound may be one type or two or more types.

[0040] (Polymerization Reaction) The polymerization reaction of the silane compound is preferably carried out under heating so that metallic sodium is in a liquid state, i.e., the polymerization reaction is preferably carried out while heating to a temperature equal to or higher than the melting point of metallic sodium.

[0041] The heating temperature is preferably equal to or higher than the melting point of sodium, more preferably equal to or higher than 98°C and equal to or lower than the solvent reflux temperature, and even more preferably equal to or higher than 100°C and equal to or lower than the solvent reflux temperature. The reaction is preferably carried out in an inert gas atmosphere such as nitrogen or argon. The reaction is also preferably carried out under normal pressure or under pressure.

[0042] The addition of the silane compound may be carried out continuously or intermittently, but from the viewpoint of production efficiency, it is preferable to add the silane compound continuously at a constant amount.

[0043] The average addition rate of the silane compound per unit amount (mol) of metallic sodium was 0.06 hr. －１ Over 0.50 hours －１ Preferably, it is 0.10 hr or less. －１ 0.30hr or more －１ More preferably, it is:

[0044] Average addition rate of silane compound (mol hr －１ ) is the value obtained by dividing the total amount (mol) of silane compounds used by the addition time (hr); the average addition rate (hr) of silane compounds per unit amount (mol) of metallic sodium －１ ) is the average addition rate of the silane compound (mol hr －１ ) divided by the amount (mol) of metallic sodium.

[0045] The average addition rate of the silane compound per unit amount (mol) of metallic sodium is 0.50 hr. －１ When the average addition rate of the silane compound per unit amount (mol) of metallic sodium is 0.06 hr or less, the temperature of the mixture can be more effectively prevented from dropping below the melting point of sodium, and the reaction can be more effectively promoted. －１ If the reaction time is more than this, the total reaction time can be further shortened, and production efficiency can be further improved.

[0046] From the viewpoint of increasing the amount of chain polysilane compound produced, it is preferable to continue stirring at the above reaction temperature after the addition of the silane compound is completed, preferably for 1 hour to 12 hours.

[0047] By the above reaction, a reaction liquid containing crude polydialkylsilane (chain polysilane compound) is obtained.

[0048] (Chain Polysilane Compound) The chain polysilane compound has a repeating unit represented by the following formula (2).

[0049] R in formula (2) １ and R ２ is R in formula (1). １ and R ２ is the same as

[0050] In the chain polysilane compound, the groups bonded to the silicon atoms at both ends of the molecule can be a hydrogen atom, a hydrocarbon group, an alkoxy group, a sodium atom, or a halogen atom. The alkoxy group or the halogen atom is represented by X in formula (1). １ and X ２ The formula is the same as above. Furthermore, the sodium atom is cationized and can be coordinated to the anionized silicon atom. Since the alkoxy group and halogen atom have a large electronegativity difference with the silicon atom, they may be easily reduced by sodium and easily generate active sites. Furthermore, since the sodium atom has a particularly large electronegativity difference with the silicon atom, it may easily function as an active site. Therefore, the groups at both molecular terminals of the chain polysilane compound may be alkoxy groups, halogen atoms, or sodium atoms.

[0051] The number of repeating units is not particularly limited, but is, for example, an integer of 2 or more, and preferably an integer of 6 or more and 12,000 or less.

[0052] 1-2. Regarding the second step, tetrahydrofuran and a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon are mixed with the reaction liquid obtained in the first step. That is, without isolating the product from the reaction liquid obtained in the first step, tetrahydrofuran and a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon are mixed with the reaction liquid.

[0053] As described above, the aromatic hydrocarbon solvent contained in the reaction solution obtained in Step 1 alone is not sufficient to form a complex between sodium and a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon, which is necessary for the decomposition reaction of the chain polysilane compound in Step 2, and therefore the decomposition reaction of the chain polysilane compound does not proceed easily. In contrast, by adding tetrahydrofuran to the reaction solution, a complex between sodium and a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon is formed and can exist stably, thereby increasing the decomposition reactivity of the chain polysilane compound.

[0054] (Tetrahydrofuran) As described above, the solution in the second step contains an aromatic hydrocarbon solvent and tetrahydrofuran. The amount of tetrahydrofuran added is preferably such that the volume ratio of tetrahydrofuran in the solution after addition is 60% by volume or more and 98% by volume or less relative to the total volume of the aromatic hydrocarbon solvent and tetrahydrofuran. When the volume ratio of tetrahydrofuran is 60% by volume or more, the decomposition reaction of the chain polysilane compound can be further promoted, and the yield of the cyclic silane compound can be further increased. When the volume ratio of tetrahydrofuran is 98% by volume or less, the volume ratio of the aromatic hydrocarbon solvent to metallic sodium can be increased, thereby enabling efficient synthesis of the chain polysilane in the first reaction and further increasing the yield of the cyclic silane. From the same viewpoint, the amount of tetrahydrofuran added is more preferably such that the volume ratio of tetrahydrofuran in the solution after addition is 75% by volume or more and 98% by volume or less relative to the total volume of the aromatic hydrocarbon solvent and tetrahydrofuran, and particularly preferably 75% by volume or more and 95% by volume or less.

[0055] The total volume of the aromatic hydrocarbon solvent and tetrahydrofuran contained in the solution is preferably 50.0 mL or more per 10 parts by mass of metallic sodium. When the total volume of the aromatic hydrocarbon solvent and tetrahydrofuran contained in the solution is 50.0 mL or more per 10 parts by mass of metallic sodium, decomposition of the produced cyclic silane compound can be further suppressed. Furthermore, when the total volume of the aromatic hydrocarbon solvent and tetrahydrofuran contained in the solution is 700.0 mL or less per 10 parts by mass of metallic sodium, the concentration of the silane compound in the system increases, making it easier to promote the reaction in the second step. From the same perspective, the total volume of the aromatic hydrocarbon solvent and tetrahydrofuran contained in the solution is more preferably 80.0 mL or more and 580 mL or less per 10 parts by mass of metallic sodium, and particularly preferably 100 mL or more and 560 mL or less per 10 parts by mass of metallic sodium.

[0056] (Polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons) Polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons can function as catalysts for the decomposition reaction of linear polysilane compounds. Either one of polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons or both may be mixed into the reaction liquid.

[0057] The polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon preferably forms a complex with sodium. Polycyclic aromatic hydrocarbons are hydrocarbon compounds containing two or more condensed aromatic rings. Polyphenyl hydrocarbons are hydrocarbon compounds containing two or more aromatic rings bonded by single bonds. Since the π electrons of the aromatic rings in these compounds are conjugated, these complexes can act as reducing agents. This is thought to cleave the silicon-silicon bond of the chain polysilane compound or the bond between the silicon at the end of the chain polysilane and the functional group, promoting the decomposition reaction. The complex of polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons with sodium is preferably formed in the presence of tetrahydrofuran.

[0058] Examples of such polycyclic aromatic hydrocarbons include naphthalene, anthracene, phenanthrene, etc. Examples of polyphenyl aromatic hydrocarbons include biphenyl, terphenyl, etc. Among them, from the viewpoint of further promoting the decomposition reaction, biphenyl, naphthalene, and anthracene are preferred, and naphthalene and biphenyl are more preferred.

[0059] The total molar equivalent of the polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons in the solution relative to the silicon atoms of the charged silane compound (monomer) is preferably 0.01 eq. or more and 0.50 eq. or less. When the total molar equivalent of the polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons is 0.01 eq. or more, the decomposition reaction of the chain polysilane compound is more likely to be promoted, and the yield of the cyclic silane compound is more likely to be increased. When the total molar equivalent of the polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons is 0.50 eq. or less, the decomposition of the generated cyclic silane compound can be further suppressed. From the same viewpoint, the total molar equivalent of the polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons is more preferably 0.04 eq. or more and 0.32 eq. or less, even more preferably 0.06 eq. or more and 0.20 eq. or less, and particularly preferably 0.08 eq. or more and 0.16 eq. or less.

[0060] (Addition and Mixing) The order of mixing the reaction liquid, the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon, and the tetrahydrofuran is not particularly limited. The polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon and the tetrahydrofuran may be added to the reaction liquid simultaneously, or tetrahydrofuran may be added to the reaction liquid and stirred, and then the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon may be added. Alternatively, the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon may be mixed with tetrahydrofuran, and then the reaction liquid may be added, or the reaction liquid may be mixed with tetrahydrofuran, and then the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon may be added. In this embodiment, as an example, it is preferable to add the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon to the reaction liquid obtained in the first step to prepare a reaction liquid containing an aromatic hydrocarbon solvent and a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon, and then further add tetrahydrofuran.

[0061] (Decomposition Reaction) Then, in the obtained solution, the chain polysilane compound is subjected to a decomposition reaction to obtain a cyclic silane compound. The decomposition reaction may be carried out at room temperature or under heating. From the viewpoint of obtaining the cyclic silane compound in a higher yield, it is preferable to carry out the decomposition reaction under heating, that is, to carry out the decomposition reaction by heating the chain polysilane compound in the solution.

[0062] The heating temperature may be equal to or lower than the reflux temperature, but is, for example, equal to or higher than 40° C., more preferably equal to or higher than 50° C., and even more preferably equal to or higher than 60° C. However, the upper limit of the heating temperature is preferably equal to or lower than 200° C. from the viewpoint of suppressing decomposition of the reaction product.

[0063] 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.

[0064] The reaction time refers to the time elapsed after the target reaction temperature is reached. When the reaction is carried out under heating, the reaction time is preferably, for example, from 1 hour to 35 hours, and more preferably from 3 hours to 10 hours, although it depends on the temperature of the solution.

[0065] The mechanism of the decomposition reaction is presumed to be as follows: The bond between a group (e.g., a halogen atom) at the molecular end of a chain polysilane compound and silicon, or the silicon-silicon bond, is cleaved by the action of a complex formed by a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon and metallic sodium, causing a change in the electronic state and the generation of active sites.Then, these active sites cause the molecular chain to break at predetermined intervals and undergo cyclization, producing a cyclic silane compound.

[0066] 1-3. Operation According to the above embodiment, in the first step, a silane compound is polymerized in a mixture containing metallic sodium and an aromatic hydrocarbon solvent. In this mixture, metallic sodium exists in a liquid state, resulting in a moderately large specific surface area. This allows the polymerization reaction of the silane compound to proceed smoothly in the first step. Furthermore, in the second step, the decomposition reaction of the linear polysilane compound is carried out in a solution containing an aromatic hydrocarbon solvent and tetrahydrofuran. This facilitates catalytic activity due to sodium and its complex with a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, thereby enhancing decomposition reactivity. This allows a cyclic silane compound to be obtained in good yield without using sodium dispersion. This allows for reduced production costs and facilitates separation and purification.

[0067] 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 (3).

[0068] R in formula (3) １ and R ２ is R in formula (1). １ and R ２ are identical to

[0069] n ２ is an integer of 3 or more. ２ is preferably 3 or more and 10 or less, more preferably 5 or more and 7 or less, and even more preferably 6.

[0070] Cyclic silane is R１ and R ２ Examples include decamethylcyclopentasilane, dodecamethylcyclohexasilane, and tetradecamethylcycloheptasilane.

[0071] 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 molar yield of the cyclic silane compound (6-membered ring) in which is 6 is preferably 50% or more, more preferably 60% or more, and even more preferably 70% 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.

[0072] Furthermore, since six-membered rings have good stability among the cyclic silanes produced, it is preferable that the resulting cyclic silane contains as many six-membered rings as possible. The selectivity of six-membered rings is preferably 80% or more, and more preferably 85% or more. The selectivity of six-membered rings is expressed as a percentage by dividing the molar yield (%) of six-membered rings by the total yield (%) of cyclic silanes.

[0073] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0074] Example 1 (1) First Step: A 200 mL four-neck flask, which had been purged with argon, was charged with 12 mL of toluene (aromatic hydrocarbon solvent, solvent [A]) and metallic sodium, the molar equivalent X of which relative to dimethyldichlorosilane was 2.4 eq., and the mixture was stirred while being heated at reflux temperature (110°C) to melt the metallic sodium. Next, 10 g of dimethyldichlorosilane (silane compound) was added dropwise to the resulting mixture over 150 minutes (average addition rate of the silane compound per unit amount (mol) of metallic sodium: 0.17 hr －１After the reaction, the mixture was stirred at a reflux temperature of 100°C or higher and 110°C or lower for 6 hours to allow the reaction to proceed. This resulted in a reaction solution containing a chain polysilane compound. The resulting reaction solution was cooled to room temperature. The toluene content in the mixed solution was 10.3 parts by mass relative to 10 parts by mass of the silane compound and 24.0 parts by mass relative to 10 parts by mass of metallic sodium.

[0075] (2) Step 2: To the reaction solution containing the chain polysilane compound, 60 mL of tetrahydrofuran (THF, solvent [B]) and naphthalene (polycyclic aromatic hydrocarbon) having a molar equivalent Y relative to dimethyldichlorosilane of 0.08 eq. were added, followed by stirring and mixing to prepare a solution. The resulting solution was then stirred and reacted at reflux temperature (71°C) for 6 hours while being heated in an oil bath. This resulted in a solution containing a cyclic silane compound. Note that the total volume of toluene and tetrahydrofuran in the reaction solution relative to 10 parts by mass of metallic sodium used in Step 1 was 167 mL, and the volume ratio of tetrahydrofuran to the total volume of toluene and tetrahydrofuran was 83% by volume.

[0076] The reaction scheme of Example 1 is shown below.

[0077] Examples 2 to 5 Solutions containing cyclic silane compounds were obtained in the same manner as in Example 1, except that the amount of toluene charged in the first step and the amount of tetrahydrofuran (THF) added in the second step were changed so that the volume ratio of tetrahydrofuran to the total volume of toluene and tetrahydrofuran in the solution obtained in the second step would be the volume ratio shown in Table 1.

[0078] Comparative Example 1 A solution containing a cyclic silane compound was obtained in the same manner as in Example 1, except that toluene was added to the reaction solution obtained in the first step instead of tetrahydrofuran (THF).

[0079] Comparative Example 2 A solution containing a cyclic silane compound was obtained in the same manner as in Example 1, except that tetrahydrofuran (THF) was used instead of toluene in the first step.

[0080] Comparative Example 3 A solution containing a cyclic silane compound was obtained in the same manner as in Example 1, except that naphthalene was not added in the second step.

[0081] Examples 6 to 10 Solutions containing cyclic silane compounds were obtained in the same manner as in Example 1, except that in the first step, the amount of toluene added (parts by mass relative to 10 parts by mass of the silane compound) was changed as shown in Table 1.

[0082] Examples 11 to 14 Solutions containing cyclic silane compounds were obtained in the same manner as in Example 2, except that the amount of naphthalene added in the second step (molar equivalent to the silane compound) was changed as shown in Table 1.

[0083] Examples 15 and 16 Solutions containing cyclic silane compounds were obtained in the same manner as in Example 1, except that in the first step, toluene was replaced with an aromatic hydrocarbon solvent shown in Table 1.

[0084] Example 17 A solution containing a cyclic silane compound was obtained in the same manner as in Example 1, except that in the first step, biphenyl was used instead of naphthalene.

[0085] The reaction products obtained in Examples 1 to 17 and Comparative Examples 1 to 3 were analyzed by gas chromatography under the following measurement conditions.

[0086] (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

[0087] 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 1.

[0088]

[0089] As shown in Table 1, the total yield is extremely low in Comparative Example 1, in which the solution in the second step does not contain THF. Similarly, the total yield is also low in Comparative Example 2, in which the solution in the second step does not contain toluene. Furthermore, the total yield is also low in Comparative Example 3, in which the solution in the second step does not contain naphthalene.

[0090] In contrast to this, in Examples 1 to 17 in which the solution in the second step contains an aromatic hydrocarbon solvent, THF, and also contains naphthalene, the total yield is improved to 38% or more.

[0091] In particular, when the volume ratio of THF to the total volume of the aromatic hydrocarbon solvent and THF in the second step is 67% or more, the total yield is found to be higher (comparison of Examples 1 to 5).

[0092] These facts show that the solution in the second step contains an aromatic hydrocarbon solvent and THF; specifically, by dissolving metallic sodium in toluene in the first step and mixing THF with a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon in the second step, the complex of sodium with the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon promotes the decomposition reaction of the linear polysilane compound, thereby making it possible to obtain a cyclic silane compound without using a sodium dispersion.

[0093] This application claims priority based on Japanese Patent Application No. 2023-127054, filed August 3, 2023, the entire contents of which are incorporated herein by reference.

[0094] According to the present invention, it is possible to provide a method for producing a cyclic silane compound that reduces production costs and facilitates separation and purification.

Claims

1. A method for producing a cyclic silane compound, comprising: a first step of polymerizing a silane compound in a mixture containing metallic sodium and an aromatic hydrocarbon solvent to obtain a reaction liquid containing a linear polysilane compound; and a second step of decomposing the linear polysilane compound in a solution obtained by mixing the reaction liquid with a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon and tetrahydrofuran to obtain a cyclic silane compound.

2. The method for producing a cyclic silane compound described in claim 1, wherein in the second step, the solution contains the tetrahydrofuran and the aromatic hydrocarbon solvent, and the volume ratio of the tetrahydrofuran contained in the solution is 75 volume % or more and 95 volume % or less relative to the total volume of the aromatic hydrocarbon solvent and the tetrahydrofuran.

3. The method for producing a cyclic silane compound according to claim 1 or 2, wherein in the first step, the mixture is heated to a temperature equal to or higher than the melting point of the metallic sodium.

4. The method for producing a cyclic silane compound according to any one of claims 1 to 3, wherein the aromatic hydrocarbon solvent contains toluene, ethylbenzene or xylene.

5. The method for producing a cyclic silane compound according to any one of claims 1 to 4, wherein the second step is carried out by heating the chain polysilane compound in the solution.

6. The method for producing a cyclic silane compound according to claim 5, wherein the heating temperature is 40° C. or higher and reflux temperature or lower.

7. The method for producing a cyclic silane compound according to any one of claims 1 to 6, wherein in the second step, biphenyl, anthracene or naphthalene is mixed as the polycyclic aromatic hydrocarbon into the reaction liquid.

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