Method for producing cyclic silane compound

Abstract

A method for producing a cyclic silane compound includes a step for obtaining a cyclic silane compound by subjecting a linear polysilane to a decomposition conversion reaction in a solution containing a solvent containing at least one of a cyclic ether solvent and an aromatic hydrocarbon solvent, metallic sodium, a polycyclic aromatic compound or a polyphenyl hydrocarbon, a polyether compound represented by formula (I) or (II) and the linear polysilane compound. The amount of the linear polysilane used in the solution is more than 6.0 g relative to 100 mL of the solvent.

Description

Method for producing cyclic silane compounds

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

[0002] Silicon carbide fibers can be obtained by spinning and infusible a precursor organosilicon polymer compound such as polycarbosilane, followed by calcination, or by obtaining an infusible component from the organosilicon polymer compound, spinning the resulting fiber, and then calcining the resulting fiber. Because oxygen-containing silicon carbide fibers decompose at high temperatures, the introduction of oxygen atoms into the organosilicon polymer compound that forms the fiber must be suppressed to obtain ultra-heat-resistant silicon carbide fibers. Therefore, ultra-heat-resistant silicon carbide fibers have been produced by using organosilicon polymer compounds with low oxygen content and infusibleizing or obtaining an infusible component without introducing oxygen. 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.

[0003] 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 dropwise to a mixed solution of a sodium dispersion, tetrahydrofuran (THF), and a polyether compound, and reacting the mixture at room temperature.

[0004] Furthermore, Patent Document 2 discloses a method for producing a cyclic silane compound by subjecting a chain polysilane compound to a decomposition and conversion reaction in a THF solution containing metallic sodium and a polycyclic aromatic hydrocarbon, etc.

[0005] JP 2021-011440 A JP 54-130541 A

[0006] However, in the method of Patent Document 1, a cyclic silane is produced by polymerizing a silane monomer compound, and therefore a stoichiometric amount of sodium dispersion containing metallic sodium, which may react with water and cause a fire, is used, which is highly dangerous and also generates a large amount of by-products such as sodium chloride. Therefore, from the viewpoint of safety and reducing the amount of by-products generated, it is desirable to reduce the amount of metallic sodium used.

[0007] In contrast, the method of Patent Document 2 produces a cyclic silane compound by subjecting a chain polysilane to a decomposition and conversion reaction, and therefore the amount of metallic sodium used can be reduced compared to the method of Patent Document 1. However, there is a problem in that the amount of cyclic silane compound produced per volume of solvent is small.

[0008] Furthermore, the method of Patent Document 2 also has the problem of leaving a large amount of insoluble matter (unreacted and produced chain polysilane compounds) after the reaction is complete. A solution containing a large amount of such remaining insoluble matter is likely to require complicated post-treatment such as purification after the reaction is complete.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a method for producing a cyclic silane compound, which can increase the amount of cyclic silane compound produced per volume of solvent even when the amount of metallic sodium used is reduced, and can reduce the mass proportion of insoluble matter remaining after completion of the reaction.

[0010] [1] A method for producing a cyclic silane compound, comprising: a step of subjecting a chain polysilane compound to a decomposition and conversion reaction in a solution containing a solvent containing at least one of a cyclic ether solvent and an aromatic hydrocarbon solvent, metallic sodium, a polycyclic aromatic compound or a polyphenyl hydrocarbon, a polyether compound represented by formula (I) or (II), and a chain polysilane compound, to obtain a cyclic silane compound, wherein the amount of the chain polysilane compound used is more than 6.0 g per 100 mL of the solvent. (In formulas (I) and (II), R ａ ~R ｈ are each independently a hydrogen atom or an alkyl group and independently for each repeating unit, and m １ and m２ are integers of 2 or more and 7 or less). [2] The method for producing a cyclic silane compound according to [1], wherein the cyclic ether solvent is tetrahydrofuran. [3] The method for producing a cyclic silane compound according to [1] or [2], wherein the ratio of the amount of substance of the polyether compound to the amount of substance of the metallic sodium is 0.5 or more. [4] The method for producing a cyclic silane compound according to any of [1] to [3], wherein the step of obtaining the cyclic silane compound is carried out by heating the chain polysilane compound in the solution. [5] The method for producing a cyclic silane compound according to any of [1] to [4], wherein the ratio of the total amount of substance of the polycyclic aromatic compound and the polyphenyl hydrocarbon to the amount of substance of the metallic sodium is 0.5 or more and 3.0 or less.

[0011] According to the present invention, it is possible to provide a method for producing a cyclic silane compound, which can increase the amount of cyclic silane compound produced per volume of solvent and reduce the mass proportion of insoluble matter remaining after completion of the reaction, even when the amount of metallic sodium used is reduced.

[0012] FIG. 1A is a photograph showing the results of the dissolution test for PDMS-1, and FIG. 1B is a photograph showing the results of the dissolution test for PDMS-2.

[0013] In a method for producing a cyclic silane compound by subjecting a chain polysilane compound to a decomposition and conversion reaction as described in Patent Document 2, it is considered effective to increase the amount of the chain polysilane compound used as the starting material per volume of solvent in order to increase the amount of the cyclic silane compound produced per volume of solvent.

[0014] Therefore, the present inventors increased the amount of the chain polysilane compound used as the starting material per volume of solvent in the above method, and found that, contrary to expectations, the amount of cyclic silane compound produced per volume of solvent decreased.

[0015] The reason for this is thought to be as follows. In the reaction of obtaining a cyclic silane compound by a decomposition and conversion reaction of a chain polysilane compound, not only a) the intramolecular bond of the chain polysilane compound is broken, and then each short-chain polysilane molecule, which is an intermediate, recombines to form a cyclic silane compound (intramolecular reaction), but also b) the molecules of the chain polysilane compound polymerize with each other to achieve a high degree of polymerization (intermolecular reaction) is thought to occur. Here, if the amount of chain polysilane compound used per volume of solvent is increased, the concentration of the chain polysilane compound in the solution increases, and the intermolecular reaction (b) above tends to occur preferentially over the intramolecular reaction (a). Therefore, it is thought that the intramolecular reaction (a) above does not proceed easily, i.e., the reaction rate slows down, and the amount of cyclic silane compound produced per volume of solvent decreases.

[0016] In response to this, the present inventors have discovered that by using a specific polyether compound in addition to conventional initiators and catalysts such as metallic sodium and polycyclic aromatic hydrocarbons, it is possible to prevent a decrease in the reaction rate of the decomposition and conversion reaction of the chain polysilane compound even when the amount of chain polysilane compound used per volume of solvent is increased, thereby enabling sufficient production of each short-chain polysilane molecule, increasing the amount of cyclic silane compound produced per volume of solvent, and further reducing the mass proportion of insoluble matter remaining after completion of the reaction. Note that the insoluble matter may be the chain polysilane compound produced, or, if the chain polysilane compound is solid, it may be unreacted chain polysilane compound.

[0017] The reason for this is thought to be as follows. In the reaction a) above, intramolecular bonds of the chain polysilane compound (bonds between terminal groups of the molecule and silicon, or silicon-silicon bonds) are cleaved by the action of a complex formed by metallic sodium and polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons, generating an intermediate having active sites. Here, the specific polyether compound stably captures sodium ions interacting with the active sites of the generated intermediate, thereby activating the generated intermediate. Furthermore, intermolecular reactions are suppressed by steric hindrance from the sodium ions interacting with the active sites and the polyether compound capturing the sodium ions. This is thought to enable the reaction rate of the above a) to be relatively increased even when a large amount of chain polysilane compound is used per volume of solvent. Furthermore, since each of the short-chain polysilane molecules has a shorter chain than the chain polysilane compound, its solubility in the solvent is higher than that of the chain polysilane compound. Therefore, sufficient generation of each short-chain polysilane molecule by the reaction a) above can reduce the amount of insoluble matter.

[0018] A method for producing a cyclic silane compound according to one embodiment of the present invention will be described below.

[0019] 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 / conversion reaction in a solution containing a solvent including at least one of a cyclic ether solvent and an aromatic hydrocarbon solvent, a chain polysilane compound, metallic sodium, a polycyclic aromatic compound, and a specific polyether compound to obtain a cyclic silane compound, wherein the amount of the chain polysilane compound used is greater than 6.0 g per 100 mL of the solvent.

[0020] Specifically, the cyclic silane compound can be obtained through the steps of preparing a solution containing a solvent containing at least one of a cyclic ether solvent and an aromatic hydrocarbon solvent, a chain polysilane compound, metallic sodium, a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon, and a specific polyether compound, and then subjecting the chain polysilane compound to a decomposition and conversion reaction in the solution. Each step is described below.

[0021] 1-1. Preparation Step A solution is prepared containing a solvent containing at least one of a cyclic ether solvent and an aromatic hydrocarbon solvent, a chain polysilane compound, metallic sodium, a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon, and a specific polyether compound.

[0022] (Chain Polysilane Compound) The chain polysilane compound has, for example, a repeating unit represented by the following formula (1).

[0023] R in the formula １ and R ２ each independently represents a hydrogen atom or a hydrocarbon group. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, and an aryl group.

[0024] 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, further preferably an alkyl group, and particularly preferably a methyl group.

[0025] Furthermore, in a chain polysilane compound, the groups bonded to the silicon atoms at both molecular terminals may be hydrogen atoms, hydrocarbon groups, halogen groups, alkoxy groups, or hydroxy groups. Examples of halogen groups include chloro groups, and examples of alkoxy groups include methoxy groups and ethoxy groups. Because halogen groups, 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 halogen groups, alkoxy groups, or hydroxy groups.

[0026] The number average molecular weight of the chain polysilane compound is not particularly limited, but is preferably high from the viewpoint of increasing the mass 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, it is possible to increase the amount of intermediates produced by the decomposition conversion reaction, thereby further increasing the mass 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.

[0027] 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, the chain polysilane compound does not completely dissolve in 1-chloronaphthalene at temperatures of 230°C or lower, more preferably does not completely dissolve in 1-chloronaphthalene at temperatures of 240°C or lower, even more preferably does not completely dissolve in 1-chloronaphthalene at temperatures of 250°C or lower, and particularly preferably does not completely dissolve in 1-chloronaphthalene at temperatures of 260°C or lower.

[0028] The temperature at which the chain polysilane compound dissolves in 1-chloronaphthalene can be confirmed by the following method. Specifically, a glass capillary with an inner diameter of 1.0 mm is filled with approximately 3 to 5 mm of a chain polysilane compound and then filled with 5 to 10 mm of 1-chloronaphthalene (approximately twice the amount of the chain polysilane compound), after which 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 230°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.

[0029] The chain polysilane compound is a white solid. Therefore, if even a portion of it remains undissolved, the remaining 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. Whether or not the compound is completely dissolved can also be confirmed by the transmittance or turbidity of the solution or the whiteness of the solution image obtained by image processing.

[0030] As described above, the amount of chain polysilane compound used is increased compared to conventional methods. Specifically, the amount of chain polysilane compound used is set to be greater than 6.0 g per 100 mL of solvent contained in the solution. This allows for a greater amount of cyclic silane compound produced per solvent volume. From the same perspective, the amount of chain polysilane compound used is preferably 8.0 g or more per 100 mL of solvent contained in the solution, and more preferably 12.0 g or more per 100 mL of solvent. The upper limit of the amount of chain polysilane compound used is not particularly limited, but from the perspective of ease of operation and easier suppression of the decrease in reaction rate due to the above-mentioned intermolecular reaction, it is preferably 40.0 g or less per 100 mL of solvent.

[0031] (Metallic sodium) Metallic sodium can function as an initiator of the decomposition conversion reaction. The form of metallic sodium is not particularly limited, and it may be fine particles or lumps. Note that when metallic sodium forms a complex with a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon described below in a solution, it becomes dissolved in the solution as sodium ions.

[0032] The solution containing fine particles of metallic sodium can be prepared using, for example, sodium dispersion (SD).

[0033] Sodium dispersion (SD) is a dispersion of metallic sodium particles in a dispersion oil, and has higher reactivity than lump metallic sodium. The metallic sodium particles can have an average particle size of 1 μm or more and 30 μm or less. The average particle size can be a value measured using a laser diffraction particle size distribution measuring device or the like. Examples of dispersion oils include aliphatic hydrocarbons such as liquid paraffin and mineral oil.

[0034] On the other hand, the solution containing the metallic sodium lump may be used by simply adding the metallic sodium lump to a solvent containing tetrahydrofuran. The metallic sodium lump may have, for example, long and short sides each of 0.3 cm to 3.0 cm.

[0035] The amount of metallic sodium used in the above solution can be defined as the amount per 100 g of the chain polysilane compound as the raw material.

[0036] The lower limit of the amount of metallic sodium used in the solution is not particularly limited, but is preferably 0.5 g or more per 100 g of chain polysilane compound. When the amount of metallic sodium used is 0.5 g or more per 100 g of chain polysilane compound, the decomposition and conversion reaction of the chain polysilane compound can be further promoted. On the other hand, the upper limit of the amount of metallic sodium used in the solution is preferably 50.0 g or less per 100 g of chain polysilane compound, more preferably 25.0 g or less, even more preferably 10.0 g or less, and particularly preferably 5.0 g or less, from the viewpoint of reducing unreacted metallic sodium and the amount of by-products produced. In particular, when the amount of metallic sodium used is 5.0 g or less per 100 g of chain polysilane compound, unreacted metallic sodium can be further reduced. Furthermore, in the present invention, the bonds in the cyclic silane compound are also partially cleaved by the interaction between the metallic sodium and the complex formed by the polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, which tends to decompose the produced cyclic silane compound. Therefore, from the viewpoint of further suppressing decomposition of the produced cyclic silane compound, it is preferable that the amounts of the initiator and catalyst used, i.e., metallic sodium, polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, and polyether compound, are not too large. From these viewpoints, the amount of metallic sodium used is preferably 0.5 g or more and 10.0 g or less, and more preferably 0.5 g or more and 5.0 g or less, per 100 g of the chain polysilane compound.

[0037] (Polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons) Polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons can function as catalysts for the decomposition and conversion reaction of linear polysilane compounds. Either the polycyclic aromatic hydrocarbons or the polyphenyl hydrocarbons or both may be used.

[0038] The polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon is preferably one that forms a complex with metallic sodium. Polycyclic aromatic hydrocarbons are hydrocarbon compounds containing two or more fused aromatic rings. Polyphenyl hydrocarbons are hydrocarbon compounds containing two or more aromatic rings bonded by single bonds. These compounds have conjugated π electrons in multiple aromatic rings, so they easily form complexes with metallic sodium, and 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 and conversion reaction. Complexes of polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons with metallic sodium are preferably formed in the presence of tetrahydrofuran.

[0039] 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 conversion reaction, biphenyl, naphthalene, and anthracene are preferred, and naphthalene and biphenyl are more preferred.

[0040] The ratio of the total amount of polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons to the amount of metallic sodium in the solution is preferably 0.5 or more and 3.0 or less. When the ratio is 0.5 or more, complexes with sodium are more easily formed, and the decomposition and conversion reaction of the chain polysilane compound can be more promoted. When the ratio is 3.0 or less, decomposition of the generated cyclic silane compound can be suppressed. From the same viewpoint, the ratio is more preferably 1.0 or more and 3.0 or less.

[0041] (Specific Polyether Compound) The specific polyether compound can stably capture sodium ions in the reaction system by coordinating oxygen atoms of multiple ether bonds to the sodium ions in the reaction system, thereby accelerating the decomposition and conversion reaction of the chain polysilane compound and increasing the reaction rate.

[0042] The specific polyether compound is a polyether compound represented by formula (I) or (II).

[0043] In formulas (I) and (II), R ａ ~R ｈ are each independently a hydrogen atom or an alkyl group, and each repeating unit is independently ａ ~R ｈ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom, an ethyl group, or a methyl group, even more preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom.

[0044] m １ and m ２ are integers of 2 or more and 7 or less. １ and m ２ is preferably an integer of 2 or more and 6 or less, and more preferably 5 from the viewpoint of selectively capturing sodium ions in the reaction system and further accelerating the reaction.

[0045] The first solution may contain only one of the polyether compound represented by formula (I) and the polyether compound represented by formula (II), or may contain both. Among them, the polyether compound represented by formula (I) is preferred from the viewpoints of ease of procurement and further reduction in production costs.

[0046] Examples of the polyether compound represented by formula (I) include diglyme, triglyme, and tetraglyme. Examples of the compound represented by formula (II) include 1,4-dioxane, 12-crown-4, 15-crown-5, and 18-crown-6. Among these, tetraglyme and 15-crown-5 are preferred from the viewpoint of their high reaction-accelerating effect.

[0047] The lower limit of the ratio of the amount of substance of the polyether compound represented by formula (I) or (II) to metallic sodium in the solution is preferably 0.01 or more, more preferably 0.04 or more, from the viewpoint of accelerating the decomposition and conversion reaction of the linear polysilane compound, and is more preferably 0.50 or more, even more preferably 0.65 or more, from the viewpoint of further reducing the mass proportion of residual insoluble matter. This allows for a greater amount of cyclic silane compound produced per solvent volume in a short reaction time, and a smaller mass proportion of residual insoluble matter. On the other hand, the upper limit of the ratio of the amount of substance of the polyether compound to metallic sodium is preferably 5.00 or less, more preferably 3.50 or less, even more preferably 1.00 or less, from the viewpoint of further suppressing decomposition of the produced cyclic silane compound and further reducing the amount of reagent used. The ratio of the amount of substance of the polyether compound to metallic sodium may be set within a range that arbitrarily combines the above-described lower and upper limits for the ratio. For example, it is preferably 0.01 or more and 5.00 or less, more preferably 0.04 or more and 5.00 or less, even more preferably 0.5 or more and 3.50 or less, particularly preferably 0.50 or more and 1.00 or less, and most preferably 0.65 or more and 1.00 or less.

[0048] (Solvent) The solvent includes at least one of a cyclic ether solvent and an aromatic hydrocarbon solvent.

[0049] The cyclic ether solvent is specifically a cyclic monoether and is different from the polyether compound represented by the above formula (I) or (II). Examples of the cyclic ether solvent include 4-methyltetrahydropyran, 2-methyltetrahydrofuran, and tetrahydrofuran, and tetrahydrofuran is preferred.

[0050] The aromatic hydrocarbon solvent preferably has a boiling point higher than the melting point of metallic sodium (98°C), and is preferably an aromatic hydrocarbon solvent with a boiling point of 100°C or higher and 210°C or lower, more preferably 110°C or higher and 170°C or lower. Examples of such aromatic hydrocarbon solvents include toluene, xylene, ethylbenzene, and mesitylene. Among these, toluene, xylene, and ethylbenzene are preferred as aromatic hydrocarbon solvents, and toluene and xylene are more preferred, as they are capable of easily dissolving metallic sodium and allowing for easier solvent recovery.

[0051] Among these, from the viewpoint of further enhancing reactivity, the solvent preferably contains a cyclic ether solvent, more preferably tetrahydrofuran (THF). Furthermore, a cyclic ether solvent such as tetrahydrofuran may be used in combination with an aromatic hydrocarbon solvent. For example, as the aromatic hydrocarbon solvent to be combined with tetrahydrofuran, an aromatic hydrocarbon solvent is selected from the viewpoints of separability from THF and improving the reaction temperature, and among these, toluene, which is highly versatile, may be selected.

[0052] The solvent may further contain other solvents as needed, examples of which include aprotic polar solvents such as 1,2-dimethoxyethane, 4-methyltetrahydropyran, bis(2-methoxyethyl)ether, 1,4-dioxane, and cyclopentyl methyl ether.

[0053] The volume ratio of at least one of the cyclic ether solvent and the aromatic hydrocarbon solvent in the solvent is not particularly limited, but from the viewpoint of further promoting the decomposition and conversion reaction of the chain polysilane compound, it is preferably 60% by volume or more, more preferably 75% by volume or more. The upper limit of the volume ratio of tetrahydrofuran is not particularly limited and may be 100% by volume.

[0054] (Mixing) The above solution can be prepared by mixing the respective components. The mixing method and procedure are not particularly limited. For example, the solution can be obtained by adding metallic sodium, polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, specific polyether compound, and chain polysilane compound to a solvent, followed by stirring and mixing, or by adding a solvent to metallic sodium, polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, specific polyether compound, and chain polysilane compound, followed by stirring and mixing.

[0055] 1-2. Step of Decomposition and Conversion Reaction In the solution prepared above, the chain polysilane compound is decomposed and converted into a cyclic silane compound. In the present invention, this reaction is referred to as a decomposition and conversion reaction. The decomposition and conversion reaction may be carried out at room temperature or under heating.

[0056] That is, the temperature of the solution during the decomposition conversion reaction can be 20°C or higher and reflux temperature or lower. 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 conversion 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 further suppressing the decomposition of the produced cyclic silane compound, the upper limit of the solution temperature is preferably 200°C or lower.

[0057] 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.

[0058] The reaction time indicates the time elapsed from the time when the entire amounts of the raw materials, that is, the chain polysilane compound, the polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, and metallic sodium, are added, the time when the color change to green or brown, which indicates the formation of a complex between the polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon and metallic sodium, is confirmed, and the time when the target reaction temperature is reached. The reaction time depends on the temperature and volume of the solution (scale of the reaction system), but is preferably, for example, from 0.5 hours to 3.0 hours when the reaction is carried out by heating in a solvent of from 50 mL to 200 mL.

[0059] 1-3. Operation As described above, in this embodiment, a linear polysilane compound is subjected to a decomposition and conversion reaction in a solution containing a specific polyether compound in addition to metallic sodium and a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon. This allows the reaction to produce a cyclic silane compound to proceed smoothly even when the amount of linear polysilane compound used per volume of solvent is increased. As a result, the amount of cyclic silane compound produced per volume of solvent can be increased, and the mass proportion of insoluble matter remaining after completion of the reaction can be reduced.

[0060] 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.

[0061] R in formula (2) １ and R ２ is R in formula (1). １ and R ２ are identical to

[0062] 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.

[0063] Cyclic silanes are R １ , R ２ and n ２ Examples include decamethylcyclopentasilane, dodecamethylcyclohexasilane, and tetradecamethylcycloheptasilane.

[0064] 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 mass yield of the cyclic silane compound having a molecular weight of 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 mass yield means the mass ratio of the amount of the cyclic silane compound produced to the amount of the chain polysilane compound used.

[0065] The amount of cyclic silane compound produced per solvent volume is preferably 6.0 g or more, more preferably 10.0 g or more, and even more preferably 20.0 g or more per 100 mL of solvent contained in the solution.

[0066] The mass yield of the cyclic silane compound and the amount of the cyclic silane compound produced per volume of solvent 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.

[0067] Furthermore, as described above, the present invention can also reduce the weight percentage of insoluble matter remaining after the reaction. Specifically, the weight percentage of insoluble matter after the reaction is preferably 20.0% by mass or less, more preferably 10.0% by mass or less, even more preferably 5.0% by mass or less, and particularly preferably 3.0% by mass or less, based on the amount of the chain polysilane compound used.

[0068] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0069] 1. Raw Materials (1) Silane Compounds PDMS-1: Linear polydimethylsilane (commercially available, linear polysilane compound, solid at room temperature, R １ , R ２ = methyl group) PDMS-2: linear polydimethylsilane (synthetic product shown below, linear polysilane compound, solid at room temperature, R １ , R ２ = methyl group) DCDMS: dichlorodimethylsilane (commercial product, monosilane, liquid at room temperature)

[0070] PDMS-2 was synthesized by the following method. Under a nitrogen atmosphere, 11.9 g of sodium was added to a 500 mL three-necked recovery flask equipped with a sheath tube and a stirrer. While maintaining the nitrogen atmosphere, 250 mL of xylene was added. After heating to 120°C in an oil bath with stirring, 32.4 g of dichlorodimethylsilane was added dropwise over 30 minutes. After the addition was completed, the mixture reached reflux temperature and was allowed to react for 7.0 hours. Thereafter, unreacted sodium was deactivated using alcohol and water. After filtering off insoluble matter, the mixture was dried in vacuo at 40°C to obtain PDMS-2 (12.3 g).

[0071] The dissolution temperature of PDMS in 1-chloronaphthalene was measured by the following method.

[0072] (Measurement of Melting Temperature) A glass capillary with an inner diameter of 1.0 mm was filled with a silane compound to a depth of about 3 to 5 mm, and filled with 1-chloronaphthalene to a depth of about 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 apparatus (B-545, manufactured by Buchi) whose internal temperature had been previously increased to 240°C, 250°C, 253°C, and 260°C, and left to stand for 5 minutes. After standing, the state of the silane compound filled in the glass capillary was visually confirmed.

[0073] As a result, it was confirmed that PDMS-1 does not completely dissolve at temperatures below 260°C (see Figure 1A), and PDMS-2 does not completely dissolve at temperatures below 240°C (see Figure 1B).

[0074] (2) Metallic sodium SD: sodium dispersion (dispersion of 25% by mass of sodium, average particle size 3.40 μm) Lump: lump metallic sodium

[0075] (3) Polycyclic aromatic compounds or polyphenyl hydrocarbons Naphthalene

[0076] (4) Polyether compounds: Tetraglyme, 15-crown-5 (15C5)

[0077] (5) Solvent: Tetrahydrofuran (THF), toluene

[0078] 2. Preparation of Cyclic Silane Compound [Example 1] A 200 mL three-neck flask containing 12.0 g of PDMS-1 (chain polysilane) was purged with nitrogen, and 0.27 g of metallic sodium block, 100 mL of tetrahydrofuran (THF), 1.8 g of tetraglyme (polyether), and 2.3 g of naphthalene (polycyclic aromatic compound) were then charged, followed by stirring and mixing to prepare a solution.

[0079] The resulting solution was stirred at reflux temperature (68°C) while being heated in an oil bath, and the reaction solution was confirmed to have turned green. The reaction was started when the reflux temperature was reached and the reaction solution had turned green, and the reaction was continued for 1.5 hours.

[0080] After the reaction, the reaction mixture was inactivated with alcohol and water, and the soluble compounds were removed. The insoluble matter was filtered off and the mixture was dried.

[0081] Examples 2, 3, 8 and 9 The reaction was carried out in the same manner as in Example 1, except that the amount of tetraglyme used was changed as shown in Table 1.

[0082] Examples 4, 5, 10 and 11 The reaction was carried out in the same manner as in Example 1, except that the amount of naphthalene (polycyclic aromatic compound) used was changed as shown in Table 1.

[0083] Example 6 The reaction was carried out in the same manner as in Example 1, except that the solvent composition was changed as shown in Table 1. However, the reflux temperature in Example 6 was 72°C.

[0084] Example 7 A reaction was carried out in the same manner as in Example 1, except that the metallic sodium lumps were changed to a sodium dispersion (25 mass % sodium dispersion), the amount of sodium dispersion used was 1.08 g (amount of metallic sodium contained: 0.27 g), and the reaction time was 1.0 hour.

[0085] Examples 12 and 13 The reaction was carried out in the same manner as in Example 1, except that the type of solvent and the amount of tetraglyme used were changed as shown in Table 1. However, the reflux temperature in Example 12 was 112°C, and the reflux temperature in Example 13 was 135°C. The reaction solution turned brown instead of green, and the reaction was started when the solution turned brown, and was continued for 1.5 hours.

[0086] Example 14 The reaction was carried out in the same manner as in Example 1, except that the type of solvent and the amount of tetraglyme used were changed as shown in Table 1. However, the reflux temperature in Example 13 was 80°C.

[0087] Comparative Example 1 The reaction was carried out in the same manner as in Example 1, except that no polyether compound was added.

[0088] [Comparative Example 2] A 100 mL three-necked flask containing 2.0 g of PDMS-2 (chain polysilane) was purged with nitrogen, and 0.21 g of metallic sodium block, 50 mL of tetrahydrofuran (THF), and 1.1 g of naphthalene (a polycyclic aromatic compound) were added. The mixture was stirred at room temperature (22 ° C) for 2.0 hours, and a green coloration was confirmed to prepare a solution. The resulting solution was heated to reflux temperature (68 ° C) in an oil bath. The reaction started when the reflux temperature was reached and the above-mentioned green coloration was achieved, and the mixture was stirred for 1.5 hours. After the reaction, the reaction solution was inactivated with alcohol and water, and the soluble compounds were removed. The insoluble matter was then filtered off and dried.

[0089] Comparative Example 3 The reaction was carried out in the same manner as in Example 1, except that the polycyclic aromatic compound (naphthalene) was not charged and the reaction time was changed as shown in Table 1. However, since no green color change was observed during the reaction, the start of the reaction was determined to be when the reflux temperature (68°C) was reached.

[0090] Comparative Example 4 A 100 mL three-necked flask containing 3.2 g of PDMS-1 (chain polysilane) was purged with nitrogen, and 55 mL of tetrahydrofuran (THF) and 0.6 g of 15-crown-5 (15C5) were added. Then, 5.00 g of sodium dispersion (containing 1.25 g of metallic sodium) was added dropwise over 5 minutes. The reaction started when the sodium dispersion addition was completed, and the mixture was stirred at room temperature (22°C) for 5.0 hours. However, no green coloring was observed during the reaction. After the reaction, the reaction solution was inactivated with alcohol and water, and the soluble compounds were removed. The insoluble matter was then filtered off and dried.

[0091] [Comparative Example 5] A 100 mL three-necked flask was purged with nitrogen, and 30 mL of tetrahydrofuran (THF), 5.00 g of sodium dispersion (containing 1.25 g of metallic sodium), and 0.6 g of 15-crown-5 (15C5) were charged. Then, a DCDMS solution prepared by dissolving 3.2 g of dichlorodimethylsilane (DCDMS) in 25 ml of THF was added dropwise over 5 minutes. After completion of the dropwise addition of the DCDMS solution, the reaction started and the mixture was stirred at room temperature (22 ° C.) for 1.0 hour to react. However, no green coloring was observed during the reaction. After the reaction, the reaction solution was inactivated with alcohol and water and the soluble compounds were removed, and the insoluble matter was filtered off and dried.

[0092] Comparative Example 6 The reaction was carried out in the same manner as in Example 1, except that the type of solvent and the amount of tetraglyme used were changed as shown in Table 1. However, the reflux temperature in Comparative Example 6 was 128°C.

[0093] [Evaluation] For Examples 1 to 14 and Comparative Examples 1 to 6, the mass yield, the amount of cyclic silane compound produced per volume of solvent, and the mass ratio of remaining insoluble matter were measured by the following methods.

[0094] (Mass yield, production amount) The reaction solution was analyzed using gas chromatography for the obtained reaction product. The measurement conditions were as follows. 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

[0095] The production of cyclic silanes (dodecamethylcyclohexasilane (6-membered ring), decamethylcyclopentasilane (5-membered ring), and tetradecamethylcycloheptasilane (7-membered ring)) was confirmed, and the mass yield and the amount of cyclic silane compound produced per volume of solvent were determined. The mass yield refers to the mass ratio of the amount of each cyclic silane produced to the amount of the starting chain polysilane compound or dichlorodimethylsilane used.

[0096] (Ratio of Residual Insoluble Matter) The mass ratio of the insoluble matter after drying to the starting chain polysilane compound or dichlorodimethylsilane was calculated as the mass ratio of the residual insoluble matter.

[0097] The reaction conditions for Examples 1 to 14 and Comparative Examples 1 to 6 are shown in Table 1, and the measurement results are shown in Table 2.

[0098]

[0099]

[0100] As shown in Tables 1 and 2, in Comparative Example 1, in which no polyether compound was added, the total mass yield of cyclic silanes was low, and the amount produced per 100 mL of solvent was small. In Comparative Example 2, the amount of chain polysilane compound used per solvent volume was small, so the mass yield was relatively good, but the amount produced per 100 mL of solvent was small. In Comparative Examples 3 to 5, in which naphthalene (polycyclic aromatic hydrocarbon) was not added, all had low mass yields and small amounts produced per 100 mL of solvent.

[0101] In contrast, in Examples 1 to 14, although the amount of the starting chain polysilane compound used per volume of solvent was large, the mass yield was high and the amount of product per 100 mL of solvent was large. It was also found that the mass proportion of the remaining insoluble matter was low.

[0102] These findings demonstrate that by reacting a chain polysilane compound in a THF solvent containing metallic sodium, a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon, and a polyether compound, it is possible to achieve a high mass yield, a large amount of product per 100 mL of solvent, and a small mass proportion of insoluble matter remaining after completion of the reaction, even when a large amount of the starting chain polysilane compound is used per volume of solvent.

[0103] In particular, it can be seen that by appropriately increasing the total molar equivalent of the polyether compound to metallic sodium to 0.04 or more, the mass yield is high and the amount produced per 100 mL of solvent is increased (comparison with Examples 1 to 3). Furthermore, a comparison of Examples 1, 3, 8, and 9 with Example 2 reveals that by setting the ratio of the amount of substance of the polyether compound to metallic sodium to 0.50 or more, the mass proportion of the remaining insoluble matter can be further reduced.

[0104] It is also clear that when the ratio of the amount of polycyclic aromatic compound to metallic sodium is 3.0 or less, the mass yield is high and the amount produced per 100 mL of solvent is large (comparison of Examples 1, 10, and 11).

[0105] Furthermore, a comparison of Examples 1, 10 and 11 shows that when the ratio of the amount of polycyclic aromatic compound to metallic sodium is 0.5 or more, the proportion of remaining insoluble matter can be further reduced.

[0106] Furthermore, a comparison of Examples 12 to 14 shows that even when a cyclic ether solvent other than THF or an aromatic hydrocarbon solvent is used, cyclic silanes are synthesized in high yield and the proportion of residual insoluble matter is low. Furthermore, a comparison of Examples 12 and 13 with Comparative Example 6 shows that, among hydrocarbons, aromatic hydrocarbons are suitable as solvents.

[0107] This application claims priority from Japanese Patent Application No. 2024-031373, filed March 1, 2024, the entire contents of which are incorporated herein by reference.

[0108] According to the present invention, it is possible to provide a method for producing a cyclic silane compound, which can increase the amount of cyclic silane compound produced per volume of solvent and reduce the mass proportion of insoluble matter remaining after completion of the reaction, even when the amount of metallic sodium used is reduced.

Claims

1. A method for producing a cyclic silane compound, comprising the step of subjecting a chain polysilane compound to a decomposition and conversion reaction in a solution containing a solvent containing at least one of a cyclic ether solvent and an aromatic hydrocarbon solvent, metallic sodium, a polycyclic aromatic compound or a polyphenyl hydrocarbon, a polyether compound represented by formula (I) or (II), and a chain polysilane compound, to obtain a cyclic silane compound, wherein the amount of the chain polysilane compound used is more than 6.0 g per 100 mL of the solvent. (In formulas (I) and (II), R ａ ~R ｈ are each independently a hydrogen atom or an alkyl group and independently for each repeating unit, and m １ and m ２ are integers between 2 and 7, 2. The method for producing a cyclic silane compound according to claim 1, wherein the cyclic ether solvent is tetrahydrofuran.

3. The method for producing a cyclic silane compound according to claim 1 or 2, wherein the ratio of the amount of substance of the polyether compound to the amount of metallic sodium is 0.5 or more.

4. The method for producing a cyclic silane compound according to claim 3, wherein the step of obtaining the cyclic silane compound is carried out by heating the chain polysilane compound in the solution.

5. The method for producing a cyclic silane compound according to claim 1 or 2, wherein the ratio of the total amount of the polycyclic aromatic compound and the polyphenyl hydrocarbon to the amount of metallic sodium is 0.5 or more and 3.0 or less.

6. The method for producing a cyclic silane compound according to claim 4, wherein the ratio of the total amount of the polycyclic aromatic compound and the polyphenyl hydrocarbon to the amount of metallic sodium is 0.5 or more and 3.0 or less.

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