Method for producing cyclic silane compounds

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

[Technical Field]

[0001] This invention relates to a method for producing cyclic silane compounds. [Background technology]

[0002] Silicon carbide fibers are highly heat-resistant and oxidation-resistant even in high-temperature environments of over 1,000 degrees Celsius. Leveraging these properties, silicon carbide fibers are expected to be applied in the nuclear and aerospace fields.

[0003] Silicon carbide fibers are obtained by spinning, infusibility treatment, and calcination of organosilicon polymer compounds such as polycarbosilane, which are precursors. Since silicon carbide fibers containing oxygen decompose at high temperatures, it is necessary to suppress the introduction of oxygen atoms in the organosilicon polymer compounds that form the fibers in order to obtain ultra-heat-resistant silicon carbide fibers. Therefore, ultra-heat-resistant silicon carbide fibers are manufactured by using organosilicon polymer compounds with a low oxygen content and employing a method that does not introduce oxygen during infusibility treatment. From cyclic silane compounds such as dodecamethylcyclohexasilane, polycarbosilane with an oxygen content of about 0.1% by weight can be obtained. Therefore, cyclic silane compounds are useful as raw materials for organosilicon polymer compounds that serve as precursors for 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, then polymerizing it to obtain a linear polysilane compound, and 2) adding naphthalene and heating the linear polysilane compound under reflux. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-156792 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the above-mentioned methods for producing cyclic silane compounds required the use of expensive sodium dispersion in stoichiometric or greater quantities. This resulted in high manufacturing costs.

[0007] Furthermore, sodium dispersions contain a large amount of dispersion oil used to disperse metallic sodium. Since the dispersion oil is a water-insoluble organic compound, and cyclic silane compounds have high solubility in the dispersion oil, separation and purification of these dispersions is difficult.

[0008] Therefore, it is desirable to be able to obtain cyclic silane compounds in a yield above a certain level without using sodium dispersion, thereby reducing manufacturing costs and facilitating separation and purification.

[0009] This invention has been made in view of the above circumstances, and aims to provide a method for producing cyclic silane compounds that reduces manufacturing costs and facilitates separation and purification. [Means for solving the problem]

[0010] This invention relates to a method for producing the following cyclic silane compounds.

[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 comprises tetrahydrofuran and the aromatic hydrocarbon solvent, and a volume ratio of tetrahydrofuran contained in the solution is 75% by volume or more and 95% by volume or less relative to a total volume of the aromatic hydrocarbon solvent and 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 a melting point of sodium metal. [4] The method for producing a cyclic silane compound according to any one of [1] to [3], wherein the aromatic hydrocarbon solvent comprises 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 the reflux temperature or lower. [7] The method for producing a cyclic silane compound according to any one of [1] to [6], wherein in the second step, biphenyl, anthracene or naphthalene is mixed into the reaction solution as the polycyclic aromatic hydrocarbon. Effect of the Invention

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

[0013] The above-mentioned sodium dispersion (SD) is a mixture obtained by dispersing solid sodium having an average particle diameter of 1 µm or more and 100 µm or less in an electrical insulating oil or an aromatic hydrocarbon solvent, and has higher reactivity compared to metallic sodium. From the viewpoints of reactivity and safety, the average particle diameter of solid sodium in SD is preferably 2 µm or more and 10 µm or less, and more preferably 3 µm or more and 5 µm or less. Examples of the electrical insulating oil include aliphatic hydrocarbons such as liquid paraffin and mineral oil.

[0014] In the present specification, metallic sodium refers to elemental sodium, and its state is not particularly limited. That is, the metallic sodium may be solid sodium or liquid sodium. Provided that in the case of solid sodium, the average particle diameter is more than 100 µm.

[0015] The above-mentioned sodium dispersion (SD) is a product obtained by dispersing fine particles of metallic sodium in an electrically insulating oil or an aromatic hydrocarbon solvent, and has higher reactivity than massive metallic sodium. Examples of the electrically insulating oil include aliphatic hydrocarbons such as liquid paraffin and mineral oil.

[0016] As a method for synthesizing cyclic silane without using sodium dispersion, it is conceivable to use massive metallic sodium instead of sodium dispersion. However, since massive metallic sodium has a small specific surface area, the polymerization reaction of the silane compound is less likely to proceed, and the reaction yield tends to decrease.

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

[0018] Liquid sodium is more likely to be refined by stirring than solid sodium, so liquid sodium has a larger specific surface area than solid sodium, and 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 linear polysilane compound, and a second step of decomposing the linear polysilane compound in the presence of a predetermined catalyst to obtain a cyclic silane compound, the cyclic silane compound can be obtained without using sodium dispersion.

[0019] From the perspective of improving manufacturing efficiency, it is desirable to carry out the second step without isolating the chain-like polysilane compound produced in the first step (one-pot production). However, the reaction solution obtained in the first step contains a large amount of aromatic hydrocarbon solvent used to liquefy the metallic sodium. Since aromatic hydrocarbon solvents do not contribute to the decomposition reaction in the second step, the reaction yield tends 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 reactivity can be increased by carrying out the decomposition reaction of the chain-like polysilane compound in a solution containing an aromatic hydrocarbon solvent and tetrahydrofuran. As a result, the desired reaction yield can be achieved.

[0021] The following describes in detail a method for producing a cyclic silane compound according to one embodiment of the present invention.

[0022] 1. Method for producing cyclic silane compounds As described above, the method for producing a cyclic silane compound according to one embodiment of the present invention is The first step involves 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. The second step involves a reaction in which a chain-like polysilane compound is decomposed in a solution containing a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon and tetrahydrofuran to obtain a cyclic silane compound. Includes.

[0023] 1-1. Regarding the first process A silane compound is polymerized in a mixture containing metallic sodium and an aromatic hydrocarbon solvent.

[0024] The metallic sodium contained in the above mixture is preferably molten. A molten state means that the metallic sodium is in a liquid state, for example, due to heating, and is different from a state in which solid sodium is uniformly dispersed in particulate form, such as in sodium dispersion.

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

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

[0027] The added sodium metal may be in its pure form or mixed with a solvent. The solvent is not particularly limited, but it is preferable to use the same solvent as used in the first step.

[0028] (Aromatic hydrocarbon solvents) The aromatic hydrocarbon solvent should have a boiling point higher than the melting point of metallic sodium (98°C). Specifically, the boiling point of the aromatic hydrocarbon solvent is more preferably between 100°C and 210°C, and even more preferably between 110°C and 170°C.

[0029] Examples of such aromatic hydrocarbon solvents include toluene, xylene, ethylbenzene, and mesitylene. Among these, toluene, xylene, and ethylbenzene are preferred, with toluene being more preferred, because they readily dissolve metallic sodium and are easy to recover during manufacturing.

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

[0031] The amount of aromatic hydrocarbon solvent in the above mixture should be such that the resulting chain-like polysilane is sufficiently stirred and dispersed in the solvent. For example, the amount of aromatic hydrocarbon solvent in the above mixture is preferably 1.0 part by mass or more per 10 parts by mass of silane compound. When the amount of aromatic hydrocarbon solvent is 1.0 part by mass or more, the volume fraction of metallic sodium decreases, which allows for a smaller average droplet diameter, increases the specific surface area of ​​sodium, and further enhances the reactivity of the silane compound. When the amount of aromatic hydrocarbon solvent is 25.0 parts by mass or less, the concentration of the silane compound in the system increases, which facilitates the reaction in the second step. From a similar viewpoint, it is more preferable that the amount of aromatic hydrocarbon solvent in the above mixture is 3.0 parts by mass or more and 16.0 parts by mass or less per 10 parts by mass of silane compound.

[0032] The content of the aromatic hydrocarbon solvent in the above 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 primarily function as a reactant in polymerization reactions.

[0034] In the above mixture, the molar equivalent of metallic sodium per alkoxy group or halogen atom of the silane compound is preferably 1.00 eq. or more and 1.80 eq. or less. If the above molar equivalent of metallic sodium is 1.00 eq. or more, the polymerization reaction rate of the silane compound in the first step can be increased. If the above molar equivalent of metallic sodium is 1.80 eq. or less, the proportion of unreacted sodium remaining can be reduced. From a similar viewpoint, it is more preferable that the above molar equivalent of metallic sodium in the above mixture is 1.05 eq. or more and 1.25 eq. or less.

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

[0036] In formula (1), X 1 and X 2 X represents an alkoxy group or a halogen atom, respectively. Examples of alkoxy groups include methoxy and ethoxy groups. Examples of halogen atoms include chlorine, bromine, and iodine atoms. These have a large electronegativity difference with silicon and readily cause intramolecular polarization within silane compounds, making them highly reactive substituents that function as leaving groups in reactions. Among them, X 1 and X 2 From the viewpoint of the reactivity of the silane compound, it is preferable that the atom be a halogen atom, and more preferably a chlorine atom.

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

[0038] n1 is an integer greater than or equal to 1. From the viewpoint of increasing the reactivity of the silane compound, n1 is preferably 1 or 2, and more preferably 1.

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

[0040] (Polymerization Reaction) The polymerization reaction of the silane compound is preferably carried out under heating from the viewpoint of carrying out the reaction in a state where metallic sodium is liquid. That is, the polymerization reaction is preferably carried out while heating at a temperature not lower than the melting point of metallic sodium.

[0041] The heating temperature is preferably not lower than the melting point of sodium, more preferably not lower than 98°C and not higher than the solvent reflux temperature, and still more preferably not lower than 100°C and not higher than the solvent reflux temperature. The reaction is preferably carried out in an inert gas atmosphere such as nitrogen or argon. In addition, the reaction is preferably carried out under normal pressure or elevated pressure.

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

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

[0044] The average addition rate of the silane compound (mol·hr -1 ) is a value obtained by dividing the total amount (mol) of the silane compound used by the addition time (hr); the average addition rate of the silane compound per unit amount (mol) of metallic sodium (hr-1 ) is the average addition rate (mol·hr) of the silane compound. -1 This is the value obtained by dividing ) by the amount (moles) of metallic sodium.

[0045] The average addition rate of silane compounds per unit amount (mol) of metallic sodium is 0.50 hr. -1 The following conditions can better prevent the temperature of the above mixture from dropping below the melting point of sodium, and can further promote the reaction: Average addition rate of silane compound per unit amount (mol) of metallic sodium is 0.06 hr. -1 This allows for a reduction in the total reaction time and an increase in manufacturing efficiency.

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

[0047] The above reaction yields a reaction solution containing crude polydialkylsilane (a chain-like polysilane compound).

[0048] (Chain polysilane compounds) The chain-like polysilane compound has repeating units represented by the following formula (2). [ka]

[0049] R in equation (2) 1 and R 2 R in equation (1) 1 and R 2 It is identical to [the other one].

[0050] In a linear polysilane compound, the groups bonded to the silicon atoms at both ends of the molecule may be hydrogen atoms, hydrocarbon groups, alkoxy groups, sodium atoms, or halogen atoms. The alkoxy group or halogen atom is X in formula (1). 1 and X 2It is identical to the above. Furthermore, the sodium atom is cationized and can coordinate to the anionized silicon atom. Alkoxy groups and halogen atoms have a large electronegativity difference with silicon atoms, so they are easily reduced by sodium and may easily generate active sites. Also, sodium atoms have a particularly large electronegativity difference with silicon atoms, so they may easily function as active sites. For this reason, the groups at both ends of the linear polysilane compound molecule 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 between 6 and 12000.

[0052] 1-2. Regarding the second process In the reaction solution obtained in the first step, tetrahydrofuran and a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon are mixed. In other words, without isolating the product from the reaction solution obtained in the first step, tetrahydrofuran and a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon are mixed into the reaction solution.

[0053] As described above, the aromatic hydrocarbon solvent contained in the reaction solution obtained in the first step is insufficient to form the complex between sodium and polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons necessary for the decomposition reaction of the chain-like polysilane compound in the second step, thus hindering the decomposition reaction of the chain-like polysilane compound. In contrast, by adding tetrahydrofuran to the reaction solution, a complex between sodium and polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons is formed and can exist stably, thereby increasing the decomposition reactivity of the chain-like polysilane compound.

[0054] (Tetrahydrofuran) As described above, the solution in the second step contains an aromatic hydrocarbon solvent and tetrahydrofuran. Preferably, the amount of tetrahydrofuran added is such that the volume ratio of tetrahydrofuran in the solution after addition is 60% to 98% of the total volume of the aromatic hydrocarbon solvent and tetrahydrofuran. If the volume ratio of tetrahydrofuran is 60% or more, the decomposition reaction of the chain-like polysilane compound can be further promoted, and the yield of the cyclic silane compound can be further increased. If the volume ratio of tetrahydrofuran is 98% or less, the volume ratio of the aromatic hydrocarbon solvent to metallic sodium can be increased, so the synthesis of chain-like polysilane in the first reaction can be carried out efficiently, and the yield of cyclic silane can be further increased. From a similar viewpoint, the amount of tetrahydrofuran added is more preferably such that the volume ratio of tetrahydrofuran in the solution after addition is 75% to 98% of the total volume of the aromatic hydrocarbon solvent and tetrahydrofuran, and is particularly preferably 75% to 95% of the total volume.

[0055] The total volume of the aromatic hydrocarbon solvent and tetrahydrofuran contained in the above 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 above solution is 50.0 mL or more per 10 parts by mass of metallic sodium, the decomposition of the generated cyclic silane compound can be further suppressed. Furthermore, when the total volume of the aromatic hydrocarbon solvent and tetrahydrofuran contained in the above 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, which facilitates the reaction in the second step. From a similar viewpoint, it is more preferable that the total volume of the aromatic hydrocarbon solvent and tetrahydrofuran contained in the above solution is 80.0 mL to 580 mL per 10 parts by mass of metallic sodium, and particularly preferable that it is 100 mL to 560 mL per 10 parts by mass of metallic sodium.

[0056] (Polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons) Polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons can function primarily as catalysts for the decomposition reactions of chain-like polysilane compounds. The reaction solution may contain either one of the polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons, or both.

[0057] It is preferable that polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons form complexes 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 linked by single bonds. Because the π electrons of the multiple aromatic rings in these compounds are conjugated, these complexes can act as reducing agents. This is thought to promote decomposition reactions by cleaving the silicon-silicon bonds in the chain-like polysilane compound, or the bonds between silicon at the end of the chain-like polysilane and the functional groups. Complexes of polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons with sodium are preferably formed in the presence of tetrahydrofuran.

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

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

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

[0061] (Decomposition reaction) Then, the linear polysilane compound is decomposed in the resulting solution 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, by heating the linear polysilane compound in solution.

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

[0063] The heating method is not particularly limited, but for example, it may be a method of placing the above solution in a predetermined temperature atmosphere, or it may be a method of heating by a heater, water bath, oil bath, electromagnetic waves, etc.

[0064] The reaction time indicates the time elapsed since reaching the target reaction temperature. The reaction time depends on the temperature of the solution, but when the reaction is carried out under heating, it is preferably between 1 hour and 35 hours, and more preferably between 3 hours and 10 hours.

[0065] The mechanism of the decomposition reaction is presumed to be as follows: The bond between the terminal group (e.g., halogen atom) and silicon in a chain-like polysilane compound, or the silicon-silicon bond, is cleaved by the action of a complex formed by polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons and metallic sodium, thereby changing the electronic state and creating an active site. Subsequently, the molecular chain is cleaved at predetermined intervals at these active sites and cyclized, generating a cyclic silane compound.

[0066] 1-3. Effect 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, the metallic sodium exists in a liquid state and has a sufficiently large specific surface area. As a result, the polymerization reaction of the silane compound can proceed smoothly in the first step. Furthermore, in the second step, the decomposition reaction of the chain-like polysilane compound is carried out in a solution containing an aromatic hydrocarbon solvent and tetrahydrofuran, which makes it easier to obtain catalytic activity from sodium and its complexes with polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons, thereby enhancing the decomposition reactivity. This allows for the acquisition of cyclic silane compounds in good yield without the use of sodium dispersion. Therefore, it is possible to reduce manufacturing costs while facilitating separation and purification.

[0067] 2. Cyclic silane compounds The cyclic silane compound obtained by the method for producing the cyclic silane compound according to this embodiment has, for example, the structure shown by the following formula (3). [ka]

[0068] R in equation (3) 1 and R 2 R in equation (1) 1 and R 2 These are identical to each other.

[0069] n2 is an integer greater than or equal to 3. Preferably, n2 is between 3 and 10, more preferably between 5 and 7, and even more preferably 6.

[0070] Cyclic silanes are R 1 and R 2 It can have any structure depending on the material used, but examples include decamethylcyclopentasilane, dodecamethylcyclohexasilane, and tetradecamethylcycloheptasilane.

[0071] The resulting cyclic silane compounds may include multiple types of cyclic silane compounds with different n2 values. The molar yield of the cyclic silane compound with n2 = 6 (6-membered ring) is preferably 50% or higher, more preferably 60% or higher, and even more preferably 70% or higher. The yield of the cyclic silane compound can be determined by analyzing the reaction product by gas chromatography. The measurement conditions may be the same as those in the examples described later.

[0072] Furthermore, since the 6-membered ring is more stable among the cyclic silanes produced, it is preferable that the resulting cyclic silane contains a greater number of 6-membered rings. The selectivity for the 6-membered ring is preferably 80% or higher, and more preferably 85% or higher. The selectivity for the 6-membered ring is calculated by dividing the molar yield (%) of the 6-membered ring by the total yield (%) of the cyclic silane, and expressing it as a percentage. [Examples]

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

[0074] [Example 1] (1) First step In a 200 mL four-necked flask that had been purged with argon, 12 mL of toluene (aromatic hydrocarbon solvent, solvent [A]) and metallic sodium with a molar equivalent X of 2.4 eq. relative to dimethyldichlorosilane were charged, and the mixture was heated and stirred 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 a period of 150 minutes (average rate of addition of silane compound per unit amount (mol) of metallic sodium: 0.17 hr). -1 The mixture was then stirred and reacted at a reflux temperature of 100°C to 110°C for 6 hours. This yielded a reaction solution containing a linear polysilane compound. The resulting reaction solution was cooled to room temperature. The toluene content in the mixed solution was 10.3 parts by mass per 10 parts by mass of the silane compound and 24.0 parts by mass per 10 parts by mass of metallic sodium.

[0075] (2)Second process To the reaction solution containing the above-mentioned linear polysilane compound, 60 mL of tetrahydrofuran (THF, solvent [B]) and naphthalene (polycyclic aromatic hydrocarbon) with a molar equivalent Y of 0.08 eq. relative to dimethyldichlorosilane were added, and the mixture was stirred and mixed to prepare the solution. The resulting solution was then heated in an oil bath and stirred at reflux temperature (71°C) for 6 hours to allow the reaction to proceed. This yielded a solution containing a cyclic silane compound. The total volume of toluene and tetrahydrofuran in the reaction solution was 167 mL relative to 10 parts by mass of metallic sodium used in the first step, and the volume ratio of tetrahydrofuran to the total volume of toluene and tetrahydrofuran was 83% by volume.

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

[0077] [Examples 2-5] A solution containing a cyclic silane compound was 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 was 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] In the second step, a solution containing a cyclic silane compound was obtained in the same manner as in Example 1, except that naphthalene was not added.

[0081] [Examples 6-10] A solution containing a cyclic silane compound was obtained in the same manner as in Example 1, except that the amount of toluene added in the first step (parts by mass per 10 parts by mass of the silane compound) was changed as shown in Table 1.

[0082] [Examples 11-14] A solution containing a cyclic silane compound was 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 15-16] A solution containing a cyclic silane compound was 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 biphenyl was used instead of naphthalene in the first step.

[0085] The reaction products obtained in Examples 1-17 and Comparative Examples 1-3 were analyzed using gas chromatography. The measurement conditions were as follows:

[0086] (Gas chromatography measurement) Equipment: GC-2025 (manufactured by Shimadzu Corporation) Column: DB1301 (Agilent Technologies), length (30m), diameter (0.320m), film (0.25m) Carrier gas: He Detector: FID

[0087] The formation of cyclic silanes (dodecamethylcyclohexasilane (6-membered ring), decamethylcyclopentasilane (5-membered ring), and tetradecamethylcycloheptasilane (7-membered ring)) was then confirmed, and their respective yields were determined. The results are shown in Table 1.

[0088] [Table 1]

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

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

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

[0092] From these findings, it can be seen that the solution in the second step contains an aromatic hydrocarbon solvent and THF. Specifically, by melting metallic sodium with toluene in the first step and mixing THF with a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon in the second step, the complex of sodium with the polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon promotes the decomposition reaction of the chain-like polysilane compound, thereby enabling the production of a cyclic silane compound without the use of sodium dispersion.

[0093] This application claims priority under Japanese Patent Application No. 2023-127054, filed on 3 August 2023. All provisions of the said application are incorporated herein by reference. [Industrial applicability]

[0094] According to the present invention, it is possible to provide a method for producing cyclic silane compounds that reduces manufacturing costs while facilitating separation and purification.

Claims

1. A first step involves heating a mixture containing metallic sodium and an aromatic hydrocarbon solvent having a boiling point higher than the melting point of the metallic sodium to a temperature above the melting point of the metallic sodium, and then polymerizing a silane compound represented by the following formula (1) in the heated mixture to obtain a reaction solution containing a chain-like polysilane compound. 【Chemistry 1】 (In formula (1), X1 and X2 each represent an alkoxy group or a halogen atom, R1 and R2 are, respectively, a hydrogen atom or a hydrocarbon group. n 1 is an integer greater than or equal to 1. A second step involves decomposing the chain-like polysilane compound in a solution obtained by mixing a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon with tetrahydrofuran in the aforementioned reaction solution to obtain a cyclic silane compound having the structure shown in the following formula (3). 【Chemistry 2】 (In formula (3), R1 and R2 are each a hydrogen atom or a hydrocarbon group, n² is an integer greater than or equal to 3. Includes, In the second step, the solution comprises the tetrahydrofuran and the aromatic hydrocarbon solvent, and the volume ratio of the tetrahydrofuran 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. A method for producing cyclic silane compounds.

2. The aforementioned aromatic hydrocarbon solvent includes toluene, ethylbenzene, or xylene. A method for producing a cyclic silane compound as described in claim 1.

3. The second step is carried out by heating the chain-like polysilane compound in the solution. A method for producing a cyclic silane compound as described in claim 1.

4. The heating temperature shall be 40°C or higher and below the reflux temperature. A method for producing a cyclic silane compound according to claim 3.

5. In the second step described above, The reaction solution is mixed with the polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, namely biphenyl, anthracene, or naphthalene. A method for producing a cyclic silane compound as described in claim 1.

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