Method for producing compound having cyclohexasilane structure

Abstract

This method for producing a compound having a cyclohexasilane structure involves: a step for preparing a solution of a compound having a cyclopentasilane structure, the solution containing the compound having a cyclopentasilane structure, metallic sodium, a solvent, and lithium chloride, a polycyclic aromatic hydrocarbon, or a polyphenyl compound; and a step for holding the solution at a liquid temperature of 0°C-60°C.

Description

Method for producing compounds having a cyclohexasilane structure

[0001] This invention relates to a method for producing compounds having a cyclohexasilane structure.

[0002] Silicon carbide fibers are obtained by spinning and infusibly fixing an organosilicon polymer compound, such as polycarbosilane, which is a precursor, and then calcining it, or by obtaining an infusible component from an organosilicon polymer compound, spinning it, and then calcining it. Since silicon carbide fibers containing oxygen decompose at high temperatures, it is desirable to suppress the introduction of oxygen atoms in the organosilicon polymer compound that forms the fiber in order to obtain ultra-heat-resistant silicon carbide fibers. For this reason, the production of ultra-heat-resistant silicon carbide fibers is being investigated by using organosilicon polymer compounds with a low oxygen content and obtaining an infusible component or infusible component by a method that does not introduce oxygen. From compounds having a cyclohexasilane structure, such as dodecamethylcyclohexasilane, polycarbosilane with an oxygen content of about 0.1% by mass can be obtained. Therefore, compounds having a cyclohexasilane structure are useful as raw materials for organosilicon polymer compounds that serve as precursors for silicon carbide fibers.

[0003] Various methods are known for producing compounds having a cyclohexasilane structure. For example, Patent Document 1 discloses a method for producing a compound having a cyclohexasilane structure by adding a silane monomer dropwise to a mixture of sodium dispersion and tetrahydrofuran (THF), reacting the mixture, and then further adding a polycyclic aromatic hydrocarbon and heating under reflux.

[0004] International Publication No. 2019 / 176704

[0005] However, our own investigations have revealed that conventional methods such as those described in Patent Document 1 produce not only the target compound having a cyclohexasilane structure (a six-membered ring compound) but also a compound having a cyclopentasilane structure (a five-membered ring compound) as a by-product. From the viewpoint of further improving the yield of the target compound having a cyclohexasilane structure and making purification easier, it is desirable to reduce the amount of the by-product compound having a cyclopentasilane structure.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a method for producing a compound having a cyclohexasilane structure that can reduce the amount of by-product compounds having a cyclopentasilane structure and improve the yield of compounds having a cyclohexasilane structure.

[0007] The present invention relates to a method for producing compounds having the following cyclohexasilane structure.

[0008] [1] A method for producing a compound having a cyclohexasilane structure, comprising the steps of: preparing a solution of the compound having a cyclopentasilane structure, comprising the compound having a cyclopentasilane structure, metallic sodium, lithium chloride or a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, and a solvent; and maintaining the solution at a liquid temperature of 0°C or higher and 60°C or lower. [2] The method for producing a compound having a cyclohexasilane structure according to [1], wherein the solution further comprises the compound having a cyclohexasilane structure. [3] The method for producing a compound having a cyclohexasilane structure according to [1] or [2], wherein the holding step is performed until the compound having a cyclopentasilane structure in the solution and the compound having a cyclohexasilane structure reach equilibrium. [4] The method for producing a compound having a cyclohexasilane structure according to any one of [1] to [3], wherein the holding step includes a silyl anion in the solution. [5] A method for producing a compound having a cyclohexasilane structure according to any one of [1] to [4], wherein in the holding step, the solution is held at the liquid temperature for 20 minutes or more. [6] A method for producing a compound having a cyclohexasilane structure according to [5], wherein in the holding step, the solution is held at a liquid temperature of T-5°C < T < T+5°C for 20 minutes or more with respect to the liquid temperature T at any given time. [7] A method for producing a compound having a cyclohexasilane structure according to any one of [1] to [6], wherein the step of preparing the solution includes reacting the silane monomer or linear polysilane with metallic sodium, lithium chloride or polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon and a solvent at a liquid temperature of 65°C or higher. [8] A method for producing a compound having a cyclohexasilane structure according to [7], wherein in the reaction step, the compound having the cyclopentasilane structure is produced by the reaction. [9] The method for producing a compound having a cyclohexasilane structure according to any one of [1] to [8], wherein in the holding step, the content of the metallic sodium in the solution is 0.1% by mass or more and 2.0% by mass or less with respect to the total mass of the solution.

[10] A method for producing a compound having a cyclohexasilane structure according to any one of [1] to [9], wherein in the holding step, the content of lithium chloride or polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon in the solution is 0.02 mol / kg or more and 0.5 mol / kg or less with respect to the total mass of the solution.

[11] A method for producing a compound having a cyclohexasilane structure according to any one of [1] to

[10] , wherein the compound having a cyclohexasilane structure is dodecamethylcyclohexasilane.

[12] A method for producing a compound having a cyclohexasilane structure according to any one of [1] to

[11] , further comprising a step of deactivating metallic sodium after the holding step.

[13] A method for producing a compound having a cyclohexasilane structure according to any one of [1] to

[12] , wherein the liquid temperature of the solution in the step of preparing the solution is 65°C or higher.

[14] The method for producing a compound having a cyclohexasilane structure according to

[10] , wherein in the holding step, the content of lithium chloride or polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon in the solution is 0.02 mol / kg or more and 0.08 mol / kg or less with respect to the total mass of the solution.

[0009] According to the present invention, a method for producing a compound having a cyclohexasilane structure can be provided, which reduces the amount of the compound having a cyclopentasilane structure and improves the yield of the compound having a cyclohexasilane structure by converting at least a portion of the by-product compound having a cyclopentasilane structure into a compound having a cyclohexasilane structure.

[0010] Figure 1 is a graph summarizing the relationship between the liquid temperature during the holding process and the change in the yield or selectivity of the six-membered ring compound, based on experimental results.

[0011] As described above, in the process of synthesizing compounds having a cyclohexasilane structure in the presence of metallic sodium or polycyclic aromatic hydrocarbons, compounds having a cyclopentasilane structure are produced as by-products. The present inventors found that when a solution containing a compound having a cyclopentasilane structure obtained in such a synthesis process, along with metallic sodium or polycyclic aromatic hydrocarbons, was held within a predetermined temperature range (0°C to 60°C), the amount of the compound having a cyclopentasilane structure in the reaction product decreased over time, while the amount of the compound having a cyclohexasilane structure obtained increased.

[0012] This phenomenon is presumed to occur through the following mechanism, however, the mechanism is not limited to this.

[0013] In the above solution, for example, a reaction between a compound having a cyclopentasilane structure (also referred to as a five-membered ring compound), metallic sodium, and a specific additive (lithium chloride, polycyclic aromatic hydrocarbon, or polyphenyl hydrocarbon), or a reaction during the synthesis of a compound having a cyclohexasilane structure (also referred to as a six-membered ring compound), results in the formation of an active species (X(R)) containing a three-coordinate silicon atom with a negative charge on the silicon atom. ２ Si) ｎ -R ２ Si － Na ＋ A ring-opening reaction occurs (where n is an integer between 0 and 4). This active species attacks the five-membered ring compound, causing it to open and become a ring-opened product containing a three-coordinate silicon atom with a negative charge on the silicon atom. This ring-closing reaction then reversibly occurs, forming a six-membered ring compound. Furthermore, after the ring-opened product is formed, either the active species or the ring-opened product can attack the five-membered ring compound, potentially generating a new ring-opened product.

[0014] The chemical species containing a three-coordinate silicon atom with a negative charge on the silicon atom, such as the active species and ring-opening products mentioned above, are silyl anions, and these silyl anions can serve as the starting point for nucleophilic reactions. Furthermore, since the ring-opening products containing the three-coordinate silicon atom with a negative charge on the silicon atom can react intermolecularly with other ring-opening products and five-membered ring compounds, the number of silicon atoms in the ring-opening products can be six or more, or even eleven or more.

[0015] When the solution temperature is above 0°C, the silyl anion attacks the five-membered ring compound, making ring-opening reactions more likely, which in turn increases the likelihood of the reaction converting it to a six-membered ring compound (the reaction proceeding to the right in the above scheme). On the other hand, when the solution temperature is below 60°C, the reverse reaction (the reaction proceeding to the left in the above scheme) in which the generated six-membered ring compound returns to a five-membered ring compound is less likely to occur. As a result, by maintaining the solution temperature between 0°C and 60°C, the reaction converting the five-membered ring compound to a six-membered ring compound (the reaction proceeding to the right in the above scheme) becomes dominant in the solution as a whole. This is thought to reduce the amount of the five-membered ring compound in the final reaction product and improve the yield of the six-membered ring compound (see Figure 1 below).

[0016] Furthermore, it was found that the above conversion reaction occurs not only in the solution obtained during the synthesis process, but also in any solution containing at least a compound having a cyclopentasilane structure, metallic sodium, and a specific additive.

[0017] A method for producing a compound having a cyclohexasilane structure according to one embodiment of the present invention will be described in detail below. In this specification, the notation "X to Y" (where X and Y are arbitrary numerical values) means "X or more and Y or less".

[0018] 1. Method for producing a compound having a cyclohexasilane structure The method for producing a compound having a cyclohexasilane structure according to this embodiment comprises the steps of: preparing a solution of the compound having a cyclopentasilane structure (solution preparation step) comprising a compound having a cyclopentasilane structure, metallic sodium, lithium chloride or a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, and a solvent; and maintaining the solution at a liquid temperature of 0°C or higher and 60°C or lower (holding step).

[0019] 1-1. Solution Preparation Process The solution of the compound having the cyclopentasilane structure may be prepared by mixing the components prepared individually, or a solution obtained during the synthesis process of the compound having the cyclohexasilane structure may be used.

[0020] When using a solution obtained in the synthesis process of a compound having a cyclohexasilane structure, the method for synthesizing the compound having a cyclohexasilane structure is not particularly limited. It may be a method of polymerization of silane monomers, a method of decomposition and transformation of linear polysilanes, or a method of polymerization of silane monomers to obtain linear polysilanes, and then decomposition and transformation of said linear polysilanes.

[0021] In particular, when synthesizing compounds having a cyclohexasilane structure under heating, compounds having a cyclopentasilane structure tend to be produced as by-products. In such cases, it is especially effective to convert at least a portion of the compounds having a cyclopentasilane structure into compounds having a cyclohexasilane structure by performing a holding step. Furthermore, when preparing by mixing individually prepared components or using solutions obtained from other sources, it is preferable to heat the solution in the solution preparation step from the viewpoint of increasing the amount of silyl anion mentioned above and obtaining compounds having a cyclohexasilane structure more efficiently in the holding step. That is, it is preferable that the temperature of the solution in the solution preparation step be 65°C or higher. However, if the solution preparation step includes the first and second steps described later, if the second step, which contributes to the formation of compounds having a cyclopentasilane structure, is performed at 65°C or higher, the solution preparation step can be considered to have been performed at 65°C or higher regardless of the temperature of the first step.

[0022] In other words, the solution preparation step preferably includes a step of generating a compound having a cyclopentasilane structure by reacting the silane monomer or linear polysilane with metallic sodium and lithium chloride or polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon at a liquid temperature of 65°C or higher.

[0023] For example, when a silane monomer is used as a raw material, the process includes: 1) a first step of polymerizing the silane monomer in a first solution containing metallic sodium to obtain a reaction liquid containing linear polysilane; and 2) a decomposition conversion reaction of the linear polysilane at a liquid temperature of 65°C or higher in a second solution obtained by mixing lithium chloride, a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon with the obtained reaction liquid, to obtain a compound having a cycloheptasilane structure and a compound having a cyclohexasilane structure. These steps can be carried out.

[0024] 1-1-1. First Step A silane monomer is subjected to polymerization reaction in a first solution containing metallic sodium.

[0025] (Metallic Sodium) In the polymerization reaction of a silane monomer, metallic sodium can function as a reactant. Since the morphology of metallic sodium in the first solution can accelerate the reaction, it is preferably fine particles of metallic sodium or metallic sodium in a molten state. That is, the first solution may contain sodium dispersion (SD) or may contain metallic sodium in a molten state.

[0026] Sodium dispersion (SD) is a product obtained by dispersing fine particles of metallic sodium in electrically insulating oil, and has higher reactivity than massive metallic sodium. The average particle diameter of the fine particles of metallic sodium in SD can be 1 µm or more and 100 µm or less. The average particle diameter can be measured by a laser diffraction particle size distribution analyzer. Examples of the electrically insulating oil include aliphatic hydrocarbons such as liquid paraffin and mineral oil.

[0027] On the other hand, molten metallic sodium means a state where metallic sodium is liquefied, for example, by heating, and is different from a state where sodium is uniformly dispersed in the form of fine particles as in sodium dispersion. The first solution containing such molten metallic sodium can be obtained, for example, by adding metallic sodium to a hydrocarbon-based solvent and then heating the mixture to a temperature not lower than the melting point of metallic sodium (98°C or higher) to melt the metallic sodium. That is, the first solution may contain a hydrocarbon-based solvent together with metallic sodium in a molten state.

[0028] The charging amount of sodium metal varies depending on the number of leaving groups in the charged silane monomer, and is preferably 1.00 eq. or more and 1.80 eq. or less, more preferably 1.05 eq. or more and 1.25 eq. or less relative to the molar amount per leaving group. When the charging amount of sodium metal is 1.00 eq. or more, the rate of the polymerization reaction of the silane monomer in the first step can be further increased. When the charging amount of sodium metal is 1.80 eq. or less, the proportion of unreacted residual sodium metal can be further reduced.

[0029] (Solvent) The type of solvent for the first solution is not particularly limited as long as it does not inhibit the reaction, but it preferably contains at least one of a cyclic ether solvent and a hydrocarbon solvent.

[0030] Specifically, the cyclic ether solvent is a cyclic monoether, which is different from the polyether compound represented by formula (1) or (2) described later. Examples of the cyclic ether solvent include 4-methyltetrahydropyran, 2-methyltetrahydrofuran, and tetrahydrofuran, with tetrahydrofuran being preferred.

[0031] The hydrocarbon solvent should have a boiling point higher than the melting point of metallic sodium (98°C). Furthermore, since high-temperature reactions in the first step can decompose the compounds having a cyclopentasilane structure and compounds having a cyclohexasilane structure, the boiling point of the hydrocarbon solvent is more preferably between 100°C and 210°C, and even more preferably between 110°C and 170°C. Such a hydrocarbon solvent may be an aliphatic hydrocarbon solvent or an aromatic hydrocarbon solvent. Examples of aliphatic hydrocarbon solvents include hydrocarbon solvents having 8 to 12 carbon atoms, such as octane and decane. Examples of aromatic hydrocarbon solvents include toluene, xylene, ethylbenzene, mesitylene, and cumene. Among these, aromatic hydrocarbon solvents are preferred in order to facilitate the formation of complexes between polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons and sodium in the second step described later, with toluene, xylene, and ethylbenzene being more preferred, and toluene and xylene being even more preferred. When a hydrocarbon solvent is used as the solvent for the first solution, it is preferable to add the polyether compound described below to accelerate the polymerization reaction of the silane monomer, the second step described below, and the retention step.

[0032] The solvent may further contain other solvents as long as they do not inhibit the reaction. Other solvents that can be miscible with the cyclic ether solvents and hydrocarbon solvents having a boiling point higher than the melting point of metallic sodium (98°C), and preferably do not react with metallic sodium and silane monomers, are preferred. Specifically, examples include saturated ether solvents, hydrocarbon solvents with a boiling point below the melting point of metallic sodium (98°C) (hereinafter, hydrocarbon solvents with a boiling point higher than the melting point of metallic sodium will be referred to as "hydrocarbon solvents," and hydrocarbon solvents with a boiling point below the melting point of metallic sodium will be referred to as "low-boiling hydrocarbon solvents"), and electrical insulating oils. Examples of saturated ether solvents include diethyl ether, dibutyl ether, and cyclopentyl methyl ether; examples of low-boiling hydrocarbon solvents include n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, and heptane; and examples of electrical insulating oils include mineral oil and liquid paraffin.

[0033] When sodium dispersion is used as a reactant, it is not necessary to bring metallic sodium into a molten state. Therefore, from the viewpoint of partially dissolving the by-produced salt and further promoting the polymerization reaction of the silane monomer, it is preferable to use a cyclic ether solvent as the solvent.

[0034] When metallic sodium is used as a reactant, from the viewpoint of carrying out the reaction in a state where metallic sodium is molten, it is preferable to use a solvent having a boiling point equal to or higher than the melting point of metallic sodium as the solvent, and it is more preferable to use the above-mentioned hydrocarbon solvent.

[0035] When both sodium dispersion and metallic sodium are used as reactants, from the viewpoint of carrying out the reaction in a state where metallic sodium is molten, it is preferable to use a solvent having a boiling point equal to or higher than the melting point of metallic sodium as the solvent, and it is more preferable to use the above-mentioned hydrocarbon solvent.

[0036] (Polyether compound) The first solution may further contain a polyether compound. In the polyether compound, the oxygen atoms of a plurality of ether bonds coordinate to sodium ions in the reaction system, so that sodium ions in the first solution, the second solution and the solution in the holding step can be stably captured, and the reactivity of the counter anion can be improved. Thereby, the polymerization reaction of the silane monomer, the decomposition conversion reaction of the linear polysilane in the second step, and the conversion reaction in the holding step can be promoted.

[0037] The polyether compound is preferably a compound represented by formula (1) or (2).

[0038] In formulas (1) and (2), R ａ to R ｈ are each independently a hydrogen atom or an alkyl group. Among them, R ａ to 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, and still more preferably a hydrogen atom or a methyl group.

[0039] m １and m ２ Each of these is an integer between 2 and 7, preferably between 2 and 6, and more preferably 5.

[0040] Examples of polyether compounds represented by formula (1) include diglyme, triglyme, and tetraglyme. Examples of compounds represented by formula (2) include dioxane, 12-crown-4, 15-crown-5, and 18-crown-6. Among these, tetraglyme and 15-crown-5 are preferred from the viewpoint of having high boiling points, high persistence in the reaction system under heating, and high reaction-promoting effects.

[0041] The amount of polyether compound added is preferably 0.3 mol% to 18.0 mol%, and more preferably 3.0 mol% to 15.0 mol%, relative to the total amount of silicon atoms contained in the added silane monomer. When the amount of polyether compound added is 0.3 mol% or more, it not only further promotes the polymerization reaction of the silane monomer, but also further promotes the decomposition and conversion reaction of the chain-like polysilane in the second step, as well as the conversion reaction in the holding step. Furthermore, when the amount of polyether compound added is 18.0 mol% or less, the decomposition of the resulting compound having a cyclohexasilane structure can be further reduced.

[0042] The total amount of silicon atoms contained in the silane monomer can be calculated using the following formula (X-1): Total amount of silicon atoms contained in the silane monomer = (Number of silicon atoms contained in the molecular formula of the silane monomer) × (Mass of the silane monomer added) / (Molecular weight of the silane monomer) ... Formula (X-1)

[0043] (Silane monomer) The silane monomer used as a raw material is preferably a compound represented by the following formula (3).

[0044] In formula (3), X １ and X ２These are either an alkoxy group or a halogen atom. 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 the silane monomer. Therefore, they are highly reactive substituents that function as leaving groups in reactions. Among them, X １ and X ２ A halogen atom is preferred, and a chlorine atom is more preferred.

[0045] R １ and R ２ R is a hydrogen atom or a hydrocarbon group. １ and R ２ A hydrocarbon group is preferred, an alkyl group having 1 to 6 carbon atoms is more preferred, a methyl group and an ethyl group are even more preferred, and a methyl group is particularly preferred.

[0046] n １ n is an integer between 1 and 5 (inclusive). １ From the viewpoint of increasing the reactivity of the silane monomer, 1 or 2 is preferred, and 1 is more preferred.

[0047] Examples of compounds represented by formula (3) include dichlorodimethylsilane, dichlorodiethylsilane, dichlorodipropylsilane, dichlorodibutylsilane, dichlorodipentylsilane, dichlorodihexylsilane, dibromodimethylsilane, dibromodiethylsilane, dibromodipropylsilane, dibromodibutylsilane, dibromodipentylsilane, dibromodihexylsilane, and dichlorotetramethyldisilane. Of these, dichlorodimethylsilane is preferred. The silane monomer may be one type or two or more types.

[0048] (Polymerization reaction) A silane monomer is added to the first solution to carry out the polymerization reaction. The polymerization reaction of the silane monomer is preferably carried out at a temperature corresponding to the composition of the first solution. For example, if the first solution contains sodium dispersion, the polymerization reaction is preferably carried out at a temperature of 0°C or higher but below the reflux temperature, and more preferably at room temperature. On the other hand, if the first solution contains a mixture of metallic sodium and a hydrocarbon solvent, the polymerization reaction is preferably carried out under heating, from the viewpoint of carrying out the reaction with the metallic sodium in a molten state.

[0049] The amount of metallic sodium consumed in the first solution during a polymerization reaction can be calculated using the following formula (Y): Amount of metallic sodium consumed in polymerization reaction = (Number of leaving groups in the structural formula of the silane monomer added × Amount of substance of the silane monomer added × Formula weight of metallic sodium) ... Formula (Y) In other words, the amount of metallic sodium added to the first solution is consumed in proportion to the amount of substance of the silane monomer added and the number of leaving groups contained in the silane monomer.

[0050] When the first solution contains a mixture of metallic sodium and a hydrocarbon solvent, the heating temperature is preferably above the melting temperature of metallic sodium (98°C), more preferably above 98°C and below the solvent reflux temperature, and even more preferably above 100°C and below the solvent reflux temperature.

[0051] From the viewpoint of increasing the amount of chain-like polysilane produced, it is preferable to continue stirring at the above heating temperature for, for example, 1 to 12 hours after the addition of silane monomer is complete, in order to carry out the heating and reaction uniformly. The stirring method is not particularly limited, and stirring can be performed using a stirring blade or stirring bar.

[0052] Furthermore, in polymerization reactions, silyl anions containing a three-coordinate silicon atom with a negative charge on the silicon atom are generated from silane monomers and can contribute to the polymerization reaction.

[0053] 1-1-2. Second step: A second solution can be obtained by mixing lithium chloride, a polycyclic aromatic hydrocarbon, or a polyphenyl hydrocarbon with the reaction solution containing the chain-like polysilane obtained in the first step.

[0054] (Chain polysilane) Chain polysilane has repeating units represented by the following formula (4).

[0055] R in equation (4) １ and R ２ R in equation (3) １ and R ２ It is identical to [the other one].

[0056] In a linear polysilane, the groups bonded to the silicon atoms at both ends of the molecule are hydrogen atoms, hydrocarbon groups, alkoxy groups, sodium atoms, or halogen atoms. The alkoxy group and halogen atom are represented by X in formula (1). １ and X ２ It is identical to [another compound]. Furthermore, the sodium atom is an ion and can bond with the negatively charged 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, because the electronegativity difference between sodium atoms and silicon atoms is particularly large, it may easily cause silicon atoms to function as active sites. For this reason, the groups at both ends of the linear polysilane molecule may be alkoxy groups, halogen atoms, or sodium atoms.

[0057] The number of repeating units is not particularly limited, but for example, it is an integer between 6 and 12000.

[0058] (Specific Additives) As specific additives, lithium chloride, polycyclic aromatic hydrocarbons, or polyphenyl hydrocarbons may be used, but from the viewpoint of solubility in the solvent, polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons are preferred.

[0059] (Lithium chloride) Lithium chloride can contribute to the stabilization of intermediates produced in the decomposition and transformation reactions of linear polysilanes.

[0060] The amount of lithium chloride added is preferably 1.0 mol% to 50.0 mol%, more preferably 1.0 mol% to 30.0 mol%, even more preferably 2.0 mol% to 30.0 mol%, and particularly preferably 2.0 mol% to 20.0 mol% relative to the total amount of silicon atoms contained in the silane monomer added. When the amount of lithium chloride added is 1.0 mol% or more, the intermediate produced in the decomposition reaction of the chain-like polysilane is more easily stabilized. When the amount of lithium chloride added is 50.0 mol% or less, the decomposition of the resulting compound having a cyclohexasilane structure can be further suppressed.

[0061] (Polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons) Polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons can function as catalysts for the decomposition and transformation reactions of chain polysilanes.

[0062] Polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons are preferably those that 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, they readily form complexes with sodium, and these complexes can act as reducing agents. This is thought to promote decomposition and transformation reactions by cleaving the silicon-silicon bonds of the linear polysilane, or the bonds between the groups (e.g., halogen atoms) at the ends of the linear polysilane and silicon.

[0063] 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 and transformation reaction, and naphthalene and biphenyl are more preferred.

[0064] The amount of polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons added is preferably 1.0 mol% to 50.0 mol%, more preferably 1.0 mol% to 30.0 mol%, even more preferably 2.0 mol% to 30.0 mol%, particularly preferably 2.0 mol% to 20.0 mol%, and most preferably 2.0 mol% to 10.0 mol% relative to the total amount of silicon atoms contained in the silane monomer added. An amount of polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons of 1.0 mol% or more is more likely to promote the decomposition and conversion reaction of the chain polysilane. An amount of polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons of 50.0 mol% or less can further suppress the decomposition of the resulting compound having a cyclohexasilane structure.

[0065] (Other components) If the solvent of the second solution is a hydrocarbon solvent, the second solution may further contain a cyclic ether solvent. This allows the decomposition and transformation reaction of the linear polysilane to proceed to a higher degree. The presence of a cyclic ether solvent in the reaction solution facilitates the formation of complexes between sodium and polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons, and these complexes tend to exist stably, thereby further enhancing the decomposition reactivity of the linear polysilane. The cyclic ether solvent can be selected from the cyclic ether solvents of the first step, and tetrahydrofuran is preferred.

[0066] (Decomposition and Conversion Reaction) The linear polysilane is decomposed and converted in the second solution at a liquid temperature of 65°C or higher. This allows for the acquisition of compounds having a cyclohexasilane structure and compounds having a cyclopentasilane structure.

[0067] There is no particular upper limit to the temperature of the second solution; it should be below the reflux temperature. For example, the temperature of the second solution can be between 65°C and 200°C. If the second solution contains a hydrocarbon solvent and a cyclic ether solvent, the ratio of each solvent can be arbitrarily set as long as it satisfies the above temperature range for the second solution.

[0068] The temperature of the second solution can be adjusted by any method. For example, the second solution may be placed in an atmosphere at a predetermined temperature, or it may be heated using a heater, water bath, oil bath, or electromagnetic waves. The temperature of the second solution can be measured by directly immersing a thermocouple in the second solution, or by immersing a glass protective tube containing a thermocouple in the second solution. When using a protective tube, paraffin oil or the like may be added to the tube to improve thermal conductivity.

[0069] To ensure uniform heating and reaction, the second solution is preferably stirred. The stirring method is not particularly limited and can be performed using a stirring blade or stirring bar.

[0070] The mechanism of the decomposition and transformation reaction is presumed to be as follows: For example, the bond between the terminal group (e.g., halogen atom) of a chain-like polysilane molecule and silicon, or the silicon-silicon bond, is cleaved by the action of metallic sodium or a complex of sodium with a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, changing the electronic state and generating an active site. Subsequently, the molecular chain is cleaved at predetermined intervals and cyclized at this active site, producing compounds having a cyclohexasilane structure and compounds having a cyclopentasilane structure. When lithium chloride is used instead of a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, the generated active site is activated by the lithium chloride, thus increasing the reactivity.

[0071] Furthermore, the number of molecular ends of the chain-like polysilane in the above decomposition reaction is very small. Therefore, the amount of metallic sodium consumed in the above decomposition reaction is almost negligible compared to the polymerization reaction.

[0072] Furthermore, in decomposition and transformation reactions, silyl anions of chemical species containing three-coordinate silicon atoms with a negative charge on the silicon atoms are generated during the decomposition of chain-like polysilanes, which can contribute to the decomposition and transformation reaction.

[0073] (Compounds having a cyclopentasilane structure) The resulting compounds having a cyclopentasilane structure have the structure shown in formula (5) below.

[0074] R in equation (5) １ and R ２ R in equation (3) １ and R ２ These are identical to each other. ２ The answer is 5.

[0075] Specific examples of compounds having a cyclopentasilane structure include decamethylcyclopentasilane, decaethylcyclopentasilane, decapropylcyclopentasilane, and 1,2,3,4,5-pentamethyl-1,2,3,4,5-pentaphenylcyclopentasilane.

[0076] (Cooling) After the decomposition and conversion reaction is complete, heating may be stopped and the temperature of the second solution may be lowered to the temperature of the holding step.

[0077] 1-2. Holding Step In the above solution preparation step, a solution can be obtained containing a compound having a cyclopentasilane structure, metallic sodium, lithium chloride or a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, and a solvent. In this embodiment, the above solution may further contain a compound having a cyclohexasilane structure. The above solution is held at a liquid temperature of 0°C to 60°C. By doing so, at least a portion of the compound having a cyclopentasilane structure can be converted into a compound having a cyclohexasilane structure.

[0078] The above conversion reaction is thought to occur through the mechanism described above. Specifically, when the solution temperature is within the range of 0°C to 60°C, the silyl anions in the solution facilitate ring opening of the cyclopentasilane compound, and the conversion reaction from a five-membered ring compound to a six-membered ring compound is likely to occur. From the viewpoint of carrying out the conversion reaction with high selectivity and a small change in yield, the solution temperature for the conversion reaction is within the range of 0°C to 60°C, preferably 10°C to 60°C, and more preferably 13°C to 35°C, and it is preferable to maintain it at these temperatures. The solution temperature can be measured by the same method as described above.

[0079] From the viewpoint of promoting the above conversion reaction, it is preferable that the solution contains silyl anions (chemical species containing a three-coordinate silicon atom with a negative charge on the silicon atom), and particularly that it contains them in a detectable amount. Whether or not silyl anions are present in the solution can be determined by bubbling air into the reaction mixture. ２９ This can be confirmed by observing changes in the peaks appearing in the chemical shift range of -10 to -50 ppm in Si-NMR. If the peaks in this range disappear, it means that silyl anions are present in the solution. ２９ Tetramethylsilane is used as a standard substance for Si-NMR measurements.

[0080] As described above, silyl anions can be generated in a solution containing a compound having a cyclopentasilane structure, metallic sodium, and lithium chloride or a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon. If the first and / or second steps are carried out, the silyl anions generated in each step may remain in the holding step and contribute to the above conversion reaction. In addition, silyl anions prepared separately may be added to the holding step.

[0081] The metallic sodium, lithium chloride, polycyclic aromatic hydrocarbons, and polyphenyl hydrocarbons in the solution during the holding process may be, for example, components that remain unconsumed in the reaction during the solution preparation process. That is, the content of metallic sodium in the solution during the holding process may be 0.1% to 2.0% by mass, 0.1% to 1.0% by mass, or 0.1% to 0.7% by mass relative to the total mass of the solution during the holding process. Whether or not metallic sodium is present in the solution can be confirmed, for example, by using an excess amount of metallic sodium in the solution preparation process, or by sampling a portion of the solution and observing the generation of hydrogen gas when alcohol or water is added. Ethanol or the like can be used as the alcohol. The amount of alcohol or water added can be, for example, about 5% by mass relative to the mass of the sampled solution.

[0082] Here, the total mass of the solution in the holding step can be, for example, the sum of the masses of each raw material used in the solution preparation step.

[0083] The amount of metallic sodium in the solution during the holding process can be calculated as the difference between the amount of metallic sodium charged in the solution preparation process and the amount of metallic sodium theoretically consumed, or from the amount of hydrogen gas generated when alcohol or water is added to the reaction system. In particular, the difference between the amount of metallic sodium charged in the solution preparation process and the amount of metallic sodium theoretically consumed can be calculated using the following formula (Z): Difference between the amount of metallic sodium charged in the solution preparation process and the amount of metallic sodium theoretically consumed = Mass of metallic sodium charged in the solution preparation process - (Value of formula (Y)) ... formula (Z) Furthermore, the amount of metallic sodium consumed in the solution preparation process can be considered to be substantially the same as the consumption in the first process, since the consumption in the second process is very small compared to the consumption in the first process and can be ignored. Therefore, in this embodiment, the amount of metallic sodium in the solution during the holding process can be calculated using the following formula (A): Content of metallic sodium in the solution during the holding process (mass %) = (Value of formula (Z)) / (Sum of the masses of each raw material used in the solution preparation process) × 100 ... formula (A)

[0084] Furthermore, since the metallic sodium is not deactivated with water or alcohol during the holding process, the solution substantially does not contain deactivated sodium components (NaOH, sodium alkoxide, etc.). In other words, the amount of metallic sodium in the solution is greater than the amount of metallic sodium contained in the deactivated solution.

[0085] The content of lithium chloride, polycyclic aromatic hydrocarbons, or polyphenyl hydrocarbons in the solution is preferably 0.02 mol / kg or more and 0.5 mol / kg or less, more preferably 0.02 mol / kg or more and 0.15 mol / kg or less, even more preferably 0.02 mol / kg or more and 0.10 mol / kg or less, and particularly preferably 0.02 mol / kg or more and 0.08 mol / kg or less, relative to the total mass of the solution. When the content of lithium chloride, polycyclic aromatic hydrocarbons, or polyphenyl hydrocarbons in the solution is within the above range, the decomposition of the ring-opening product generated in the above conversion reaction is suppressed, and the conversion rate from the by-product compound having a cyclopentasilane structure to the compound having a cyclohexasilane structure is improved. Furthermore, the effect is particularly pronounced when the content of lithium chloride, polycyclic aromatic hydrocarbons, or polyphenyl hydrocarbons in the solution is 0.02 mol / kg or more and 0.10 mol / kg or less or 0.02 mol / kg or more and 0.08 mol / kg or less, relative to the total mass of the solution. Whether or not lithium chloride is present in the solution is ７ This can be confirmed by the presence of a peak near a chemical shift value of 0 ppm in Li-NMR. ７ Since lithium chloride is used as the standard substance for Li-NMR measurements, the results can be determined by comparing them with the chemical shift values ​​of the external standard used. Specifically, a known standard solution is prepared by dissolving a certain amount of the reference substance (lithium chloride) for the external standard separately from the sample solution. Then, for both the sample solution and the standard solution... ７ By performing Li-NMR measurements and comparing the results of these two measurements (the presence or absence of a peak near a chemical shift value of 0 ppm), the presence or absence of lithium chloride can be determined. Whether or not polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons are present in the solution can be confirmed by gas chromatography.

[0086] In the solution preparation process, lithium chloride, polycyclic aromatic hydrocarbons, or polyphenyl compounds function as catalysts and are not substantially consumed. Therefore, the content of lithium chloride, polycyclic aromatic hydrocarbons, or polyphenyl compounds in the solution during the holding process can be calculated using the following formula (B): Content of lithium chloride, polycyclic aromatic hydrocarbons, or polyphenyl compounds in the solution during the holding process (mol / kg) = (Amount of lithium chloride, polycyclic aromatic hydrocarbons, or polyphenyl compounds added) / (Sum of the masses of each raw material used in the solution preparation process) ... Formula (B)

[0087] The holding step is preferably carried out until the compound having a cyclohexasilane structure and the compound having a cyclopentasilane structure in the solution reach equilibrium. Whether equilibrium has been reached can be confirmed, for example, by sampling the reaction product in the solution multiple times at elapsed time intervals and checking whether the ratio of the amounts of the reaction products ([six-membered ring compound] / [five-membered ring compound]) or the selectivity of the six-membered ring compound, described later, becomes approximately constant. For example, if the difference in the selectivity of the six-membered ring compound, described later, per 30 minutes is 0.5% or less, it can be determined that equilibrium has been reached.

[0088] The ratio of the above-mentioned amounts of substances can be measured by gas chromatography. The measurement conditions can be as follows: Apparatus: GC-2025 (Shimadzu Corporation) Column: DB1301 (Agilent Technologies), length (30 m), Diameter (0.320 mm), Film (0.25 μm) Carrier gas: He Detector: FID

[0089] During at least part of the holding process, the temperature of the solution may change or be kept substantially constant. For example, the temperature of the solution may be gradually lowered. In particular, from the viewpoint of facilitating the conversion reaction described above to proceed in a short time, it is preferable that the temperature be kept substantially constant during at least part of the holding process. For example, the holding process preferably includes a step of holding the solution for a predetermined time within a temperature range of T-5°C < T < T+5°C with respect to the temperature T at any point in the holding process, and more preferably includes a step of holding the solution for a predetermined time within a temperature range of T-3°C < T < T+3°C. T (°C) may be the temperature at any point in the holding process, for example, the temperature at the start of the holding process, or the temperature after a predetermined time has elapsed from the start. The temperature T (°C) may be, for example, 5°C or more and 55°C or less, preferably 13°C or more and 30°C or less, more preferably 18°C ​​or more and 30°C or less, even more preferably 20°C or more and 30°C or less, and particularly preferably 22°C or more and 27°C or less.

[0090] The method for adjusting the temperature of the solution can be the same as the method described above. For example, the temperature of the solution can be adjusted by placing the solution in a predetermined temperature atmosphere, or by heating it with a heater, water bath, oil bath, or electromagnetic waves.

[0091] The time for maintaining the solution temperature within the above range (holding time) is sufficient as long as it is within the range that leads to equilibrium. That is, the holding time depends on the solution temperature, but is preferably 20 minutes or more, more preferably 40 minutes or more, and even more preferably 60 minutes or more. Also, the holding time is preferably 540 minutes or less, more preferably 360 minutes or less, and even more preferably 180 minutes or less. That is, the holding time is preferably 40 minutes or more and 540 minutes or less, more preferably 40 minutes or more and 360 minutes or less, even more preferably 60 minutes or more and 360 minutes or less, and particularly preferably 60 minutes or more and 180 minutes or less. If the holding time is 20 minutes or more, the above conversion reaction proceeds sufficiently, so that the amount of compound having a cyclopentasilane structure in the final reaction product can be further reduced and the proportion of compound having a cyclohexasilane structure can be further increased. If the holding time is 540 minutes or less, the manufacturing efficiency can be further increased. The holding time is defined as the time from the point when the liquid temperature reaches the above-mentioned range of 0°C to 60°C, and preferably the time for holding within the liquid temperature range of T ± 5°C. Furthermore, even within the above temperature range, if the deactivation process is performed, the holding can be considered complete at that point.

[0092] During at least part of the holding process, the solution may or may not be stirred. From the viewpoint of accelerating the conversion reaction, stirring the solution is preferable.

[0093] 1-3. Other Steps The method for producing compounds having a cyclohexasilane structure may further include other steps as needed. For example, after the holding step, a step of inactivating metallic sodium (deactivation step) may be performed by adding alcohol or water to the resulting solution. This treatment makes metallic sodium undetectable in the solution. This stops reactions in the solution, such as conversion reactions. This treatment is also called quenching.

[0094] 2. Compounds having a cyclohexasilane structure The compounds having a cyclohexasilane structure obtained by the above production method are, in formula (5) above, n ２ It can be the same except that it is set to 6.

[0095] Specific examples of compounds having a cyclohexasilane structure include dodecamethylcyclohexasilane, dodecaethylcyclohexasilane, dodecapropylcyclohexasilane, and 1,2,3,4,5,6-hexamethyl-1,2,3,4,5,6-hexaphenylcyclohexasilane.

[0096] In addition to compounds having a cyclohexasilane structure, the reaction products also contain n ２ This may include cyclic silane compounds other than 6, typically compounds having a cyclopentasilane structure as a by-product. However, the amount of compounds having a cyclopentasilane structure in the reaction product can be reduced by performing the above holding step.

[0097] The molar yield of the compound having a cyclohexasilane structure after the holding step is preferably 65% ​​or more, more preferably 67% or more, and even more preferably 70% or more. Furthermore, the ratio of the molar yield of the compound having a cyclohexasilane structure to the sum of the molar yields of the compound having a cyclohexasilane structure and the compound having a cycloheptasilane structure (selectivity of the 6-membered ring compound) is preferably 84% or more, more preferably 85% or more, and even more preferably 90% or more. Moreover, it is particularly preferable that the molar yield of the compound having a cyclohexasilane structure is 65% or more and the selectivity of the 6-membered ring compound is 84% ​​or more, even more preferably 67% or more and the selectivity of the 6-membered ring compound is 85% or more, most preferably 67% or more and the selectivity of the 6-membered ring compound is 90% or more. The yield of the compound having a cyclohexasilane structure 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.

[0098] [Effect] As described above, the manufacturing method of the above embodiment includes the steps of preparing a solution of the compound having a cyclopentasilane structure, containing the compound having a cyclopentasilane structure, metallic sodium, lithium chloride or a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, and a solvent, and maintaining the solution at a liquid temperature of 0°C to 60°C. By performing this holding step, by-products can be reduced and the yield of the target product can be increased, so that the by-product compound having a cyclopentasilane structure can be converted to the target compound having a cyclohexasilane structure with a high conversion rate, and the yield of the compound having a cyclohexasilane structure can be improved. As a result, the amount of by-product compound having a cyclopentasilane structure can be reduced and the yield of the compound having a cyclohexasilane structure can be improved.

[0099] 3. Modifications In the above embodiment, a solution is obtained by polymerizing a silane monomer as a starting material in the presence of metallic sodium to produce a chain-like polysilane, and then decomposing and transforming the chain-like polysilane in the presence of lithium chloride, a polycyclic aromatic compound, or a polyphenyl hydrocarbon. However, the invention is not limited to this. For example, a solution may be obtained by decomposing and transforming a chain-like polysilane as a starting material in the presence of metallic sodium, lithium chloride, a polycyclic aromatic compound, or a polyphenyl hydrocarbon. In this case as well, during the decomposition and transformation reaction, silyl anions of chemical species containing three-coordinate silicon atoms with a negative charge on the silicon atoms are generated when the chain-like polysilane is decomposed, and can contribute to the decomposition and transformation reaction. When chain-like polysilane is used as a starting material, the first step can be omitted, and the chain-like polysilane, metallic sodium, solvent, polyether compound, etc. are added in the second step. In this case, the molar equivalent of the amount of metallic sodium charged relative to the total amount of silicon atoms contained in the chain-like polysilane is 0.02 eq. to 0.50 eq. The following is preferable, and 0.05 eq. to 0.30 eq. is more preferable. On the other hand, the amount of lithium chloride, polycyclic aromatic hydrocarbon, or polyphenyl hydrocarbon charged may be within the above ranges.

[0100] The total amount of silicon atoms contained in the chain-like polysilane can be calculated using the following formula (C): Total amount of silicon atoms contained in the chain-like polysilane = (mass of the chain-like polysilane) / (formula weight of the repeating structure of the chain-like polysilane) ... Formula (C)

[0101] Furthermore, when chain-like polysilane is used as a raw material, the first step is omitted, and therefore, in the holding step, almost no metallic sodium is consumed, similar to the consumption of metallic sodium in the decomposition reaction described above. Accordingly, the metallic sodium content in the solution during the holding step can be calculated using the following formula (D): Metallic sodium content in the solution during the holding step (mass %) = Amount of metallic sodium charged / (Sum of the masses of each raw material used in the solution preparation step) × 100 ... Formula (D)

[0102] Furthermore, in the above embodiment, the reaction solution obtained in the first step of the solution preparation process is used as is, and the second step and the holding step are carried out continuously. Therefore, the solvent used in the second step and the holding step is the same as the solvent used in the first step. However, this is not limited to this, and each step may be carried out independently.

[0103] When each step is carried out independently, it is preferable to use a cyclic ether solvent or a hydrocarbon solvent containing a polyether compound as the solvent used in the second step and the holding step, similar to the first step. This promotes the decomposition and conversion reaction in the second step, allowing for the efficient acquisition of compounds having a cyclohexasilane structure and compounds having a cyclopentasilane structure. Furthermore, the conversion reaction is promoted in the holding step, allowing for the efficient acquisition of compounds having a cyclohexasilane structure.

[0104] Furthermore, in the above embodiment, the solution is prepared by synthesizing a compound having a cyclohexasilane structure in the solution preparation step, and therefore the resulting solution contains a compound having a cyclohexasilane structure, but this is not limited to this. For example, when preparing a new solution, the solution does not need to contain a compound having a cyclohexasilane structure.

[0105] In the above embodiment, lithium chloride is added in the second step, but it may also be added in the first step. That is, the first solution may further contain lithium chloride. This eliminates the need to add additional reagents when lithium chloride is used in the second step. Furthermore, it allows the chain-like polysilane formation reaction to proceed more rapidly.

[0106] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0107] [Test 1] (1) Solution preparation step (First step) In a 100 mL four-necked flask that had been purged with argon, 40 mL (35 g) of toluene (aromatic hydrocarbon solvent), 3.75 g of metallic sodium with a molar equivalent of 2.1 eq. to the total amount of silicon atoms contained in DCDMS (dichlorodimethylsilane, silane monomer), and 1.73 g of tetraglyme (polyether compound) at 10 mol% relative to the total amount of silicon atoms contained in DCDMS were added, and the mixture was heated and stirred at reflux temperature (110°C) to melt the metallic sodium. 10.0 g of DCDMS was added dropwise to the obtained solution (first solution) over 2 hours, and then the mixture was stirred at 110°C for 1 hour to allow the reaction to proceed. A reaction solution containing linear polysilane was obtained.

[0108] (Second step) To the obtained reaction solution, 8 mol% (0.79 g) of naphthalene (polycyclic aromatic hydrocarbon) relative to the total amount of silicon atoms contained in DCDMS was added, and the mixture was stirred and mixed. The obtained solution (second solution) was heated in an oil bath and stirred at reflux temperature (115°C, second step temperature) for 5 hours to allow the reaction to proceed. This yielded a solution containing a compound having a cyclohexasilane structure (dodecamethylcyclohexasilane) and a compound having a cyclopentasilane structure (decamethylcyclopentasilane). The amounts of dodecamethylcyclohexasilane and decamethylcyclopentasilane were measured by analyzing the obtained solution using gas chromatography, as described later.

[0109] The flask containing the above solution was transferred to a water bath at a liquid temperature of 22°C and cooled until the solution temperature reached 22°C. According to formula (Z) above, the content of metallic sodium in the obtained solution is 0.35% by mass relative to the total mass of the solution, and the content of naphthalene is 0.12 mol / kg relative to the total mass of the solution.

[0110] The scheme for the solution preparation process is shown below.

[0111] (2) Holding process Next, the holding process began when the liquid temperature of the solution reached 22°C, and the solution was stirred for 120 minutes while being held at a liquid temperature of 22°C. After that, the reaction solution was obtained and the content of decamethylcyclopentasilane and dodecamethylcyclohexasilane was measured by gas chromatography, as described below.

[0112] The scheme for the holding process is shown below.

[0113] [Test 2] (1) Solution preparation step (First step) In a 100 mL four-necked flask that had been purged with argon, 36 g of 40 mL of THF (tetrahydrofuran, cyclic ether solvent) and 15.0 g of sodium dispersion (containing 25% by mass of metallic sodium) in an amount such that the molar equivalent of metallic sodium to DCDMS (dichlorodimethylsilane) was 2.1 eq. were added. To the resulting first solution, 10.0 g of DCDMS was added dropwise over 2 hours, and the mixture was stirred at 20°C to 25°C for 1 hour to allow the reaction to proceed. This yielded a reaction solution containing linear polysilane.

[0114] (Second step) To the obtained reaction solution, 8 mol% (0.79 g) of naphthalene relative to the total amount of silicon atoms contained in DCDMS was added, and the mixture was stirred and mixed. The obtained solution (second solution) was heated in an oil bath and stirred at reflux temperature (70°C, second step temperature) for 5 hours to allow the reaction to proceed. This yielded a solution containing a compound having a cyclohexasilane structure (dodecamethylcyclohexasilane) and a compound having a cyclopentasilane structure (decamethylcyclopentasilane).

[0115] (2) Holding step The obtained solution was held under the same conditions as in Test 1, and the amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the obtained solution were measured by gas chromatography as described later.

[0116] [Tests 3, 4, 7, and 8] The liquid was held in the same manner as in Test 1, except that the liquid temperature during the holding process was changed as shown in Table 2. After holding, a solution containing decamethylcyclopentasilane and dodecamethylcyclohexasilane was obtained, and the amounts of these compounds were measured by gas chromatography as described later.

[0117] [Test 5] (1) In the second step of the solution preparation process, lithium chloride (LiCl) was added instead of naphthalene, and the reaction was carried out at a liquid temperature of 71°C (second step temperature). Except for these steps, a solution containing dodecamethylcyclohexasilane and decamethylcyclopentasilane was obtained in the same manner as in Test 2.

[0118] (2) Holding step The obtained solution was held under the same conditions as in Test 1, and the amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the obtained solution were measured by gas chromatography as described later.

[0119] [Test 6] (1) Solution preparation step In a 100 mL four-necked flask that had been purged with argon, 4.45 g of polydimethylsilane (PDMS, linear polysilane), 35 g of toluene in 40 mL, 0.18 g of metallic sodium with a molar equivalent of 0.10 eq. relative to the total amount of silicon atoms in the PDMS, 0.79 g of naphthalene at 8.0 mol% relative to the total amount of silicon atoms in the PDMS, and 1.73 g of tetraglyme at 10.0 mol% relative to the total amount of silicon atoms in the PDMS were added and stirred at reflux temperature (115 °C, second step temperature) for 5 hours to allow the reaction to proceed. This yielded a solution containing dodecamethylcyclohexasilane and decamethylcyclopentasilane. That is, since linear polysilane was used as the raw material, only the second step was performed.

[0120] (2) Holding step The obtained solution was held under the same conditions as in Test 1, and the amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the obtained solution were measured by gas chromatography as described later.

[0121] [Test 9] (1) Solution preparation process: After obtaining a solution containing decamethylcyclopentasilane and dodecamethylcyclohexasilane in the second step of the solution preparation process, 3.0 g of MeOH was added to the second solution at the second step temperature to perform a deactivation treatment of metallic sodium. The solution preparation process was carried out in the same manner as in Test 1.

[0122] (2) Holding step The obtained solution was held under the same conditions as in Test 1, and the amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the obtained solution were measured by gas chromatography as described later.

[0123] [Test 10] (1) Solution preparation step A solution containing dodecamethylcyclohexasilane and decamethylcyclopentasilane was obtained in the same manner as in Test 1, except that naphthalene was not added.

[0124] (2) Holding step The obtained solution was held under the same conditions as in Test 1, and the amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the obtained solution were measured by gas chromatography as described later.

[0125] [Test 11] (1) Solution preparation step (First step) In a 100 mL four-necked flask that had been purged with argon, 18 g of tetrahydrofuran in 20 mL, 0.10 g of LiCl in an amount of 10.0 mol% relative to the total amount of silicon atoms contained in DCDMS, and 4.7 g of sodium dispersion in an amount such that the molar equivalent of metallic sodium was 2.1 eq. relative to the total amount of silicon atoms contained in DCDMS were added. To the resulting first solution, 3.23 g of DCDMS was added dropwise over 2 hours, and the mixture was stirred at a temperature of 20°C to 25°C for 1 hour to allow the reaction to proceed. This yielded a reaction solution containing linear polysilane.

[0126] (Second step) The obtained second solution was heated in an oil bath and stirred at reflux temperature (71°C, second step temperature) for 6 hours to allow the reaction to proceed. This yielded a solution containing decamethylcyclopentasilane and dodecamethylcyclohexasilane.

[0127] (2) Holding process The holding process began when the temperature reached 22°C. At 10, 20, 40, 60, 90, and 120 minutes, the reaction solution was analyzed by gas chromatography, and the amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane were measured by gas chromatography as described later.

[0128] [Test 12] (1) Solution preparation step: The reaction was carried out in the same manner as in Test 11, thereby obtaining a solution containing decamethylcyclopentasilane and dodecamethylcyclohexasilane.

[0129] (2) Holding process In the holding process, immediately after the holding temperature was reached (i.e., with the holding time set to 0 minutes), the amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the solution were measured by gas chromatography as described later.

[0130] [Test 13] (1) Solution preparation step: The reaction was carried out in the same manner as in Test 1, thereby obtaining a solution containing decamethylcyclopentasilane and dodecamethylcyclohexasilane.

[0131] (2) Holding process The holding process was carried out in the same manner as in Test 1, except that the holding temperature was changed as shown in Table 2. The amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the obtained solution were measured by gas chromatography as described later.

[0132] [Test 14] (1) Solution preparation step: The reaction was carried out in the same manner as in Test 1, thereby obtaining a solution containing decamethylcyclopentasilane and dodecamethylcyclohexasilane.

[0133] (2) Holding process The holding process was carried out in the same manner as in Test 1, except that the holding time was changed as shown in Table 2. The amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the obtained solution were measured by gas chromatography as described later.

[0134] [Test 15] (1) Solution preparation step The reaction was carried out in the same manner as in Test 1, except that the solvent used was changed to xylene, thereby obtaining a solution containing decamethylcyclopentasilane and dodecamethylcyclohexasilane.

[0135] (2) Holding step The obtained solution was held under the same conditions as in Test 1, and the amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the obtained solution were measured by gas chromatography as described later.

[0136] [Test 16] (1) Solution preparation step The reaction was carried out in the same manner as in Test 1, except that the amount of naphthalene used was changed as shown in Table 1, thereby obtaining a solution containing decamethylcyclopentasilane and dodecamethylcyclohexasilane.

[0137] (2) Holding step The obtained solution was held under the same conditions as in Test 1, and the amounts of decamethylcyclopentasilane and dodecamethylcyclohexasilane in the obtained solution were measured by gas chromatography as described later.

[0138] [Gas Chromatography Measurement] Gas chromatography measurements were performed under the following conditions: (Measurement Conditions) Instrument: GC-2025 (Shimadzu Corporation) Column: DB1301 (Agilent Technologies), length (30 m), Diameter (0.320 mm), Film (0.25 μm) Carrier gas: He Detector: FID

[0139] The formation of cyclic silanes (dodecamethylcyclohexasilane (six-membered ring compound) and decamethylcyclopentasilane (five-membered ring compound)) was confirmed, and their molar yields (%) were determined. The ratio of the molar yield of the six-membered ring compound to the sum of the molar yields of the five-membered ring compound and the six-membered ring compound was defined as the selectivity (%) of the six-membered ring compound. Figure 1 is a graph summarizing the relationship between the liquid temperature during the holding process and the change (%) in the yield or selectivity of the six-membered ring compound, based on the results of tests 1, 3, 4, 7, and 813.

[0140]

[0141]

[0142] As shown in Tables 1 and 2 and Figure 1, in tests 1 to 6 and 13 to 16, in which the liquid temperature was maintained between 0°C and 60°C, the change in yield to compounds having a cyclohexasilane structure (six-membered ring compounds) was positive (i.e., the yield increased) compared to test 7, in which the liquid temperature was maintained below 0°C, and test 8, in which the liquid temperature was maintained at 80°C.

[0143] On the other hand, even when a holding step is performed at 0°C to 60°C, in Test 9, metallic sodium is deactivated in the solution during the holding step, and the metallic sodium is converted to NaOH or sodium alkoxide, etc., so the conversion reaction from five-membered ring compounds to six-membered ring compounds does not proceed, and the selectivity of six-membered ring compounds does not change much even when the predetermined holding step is performed. Furthermore, in Test 10, since no specific additive is contained in the solution, the amount of six-membered ring compounds and five-membered ring compounds produced after the second step is small, and the yield of six-membered ring compounds does not change much even when the predetermined holding step is performed, so it can be seen that silyl anions are not generated and the conversion reaction from five-membered ring compounds to six-membered ring compounds does not occur.

[0144] Furthermore, a comparison of tests 1, 2, 5, and 10 shows that, regardless of whether naphthalene or LiCl is used as the additive, the yield of the six-membered ring compound is improved by performing the predetermined holding step.

[0145] Furthermore, a comparison of tests 1, 2, and 15 shows that the solvent can be any of toluene, THF, or xylene, and that a similar trend is observed even when the form of metallic sodium is SD (sodium dispersion). A comparison of tests 1 and 6 also shows that the yield of the six-membered ring compound improves not only when using silane monomers as starting materials, but also when using linear polysilanes, by performing the prescribed holding step, indicating that the conversion reaction occurs similarly.

[0146] Furthermore, a comparison of tests 11 and 12 shows that by performing a holding process for 20 minutes or more, the molar ratio of the 5-membered ring compound to the 6-membered ring compound approaches equilibrium, and the yield of the 6-membered ring compound is further improved. In addition, the results of test 11 show that the rate of change in the selectivity of the 6-membered ring compound after a holding time of 60 minutes is 0.5% or less, indicating that equilibrium is reached after a holding time of 60 minutes.

[0147] Furthermore, a comparison of Test 1 and Test 16 shows that when the content of polycyclic aromatic hydrocarbons in the solution is between 0.02 mol / kg and 0.08 mol / kg relative to the total mass of the solution, the conversion rate and yield from five-membered ring compounds to six-membered ring compounds are further improved.

[0148] This application claims priority under Japanese Patent Application No. 2025-030433, filed on 27 February 2025. All contents described in the specification and drawings of said application are incorporated herein by reference.

[0149] The method for producing compounds having a cyclohexasilane structure according to the present invention makes it possible to reduce the amount of by-product compounds having a cyclopentasilane structure and improve the yield of compounds having a cyclohexasilane structure.

Claims

1. A method for producing a compound having a cyclohexasilane structure, comprising the steps of: preparing a solution of the compound having a cyclopentasilane structure, comprising the compound having a cyclopentasilane structure, metallic sodium, lithium chloride or a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon, and a solvent; and maintaining the solution at a liquid temperature of 0°C or higher and 60°C or lower.

2. The method for producing a compound having a cyclohexasilane structure according to claim 1, wherein the solution further comprises a compound having a cyclohexasilane structure.

3. The method for producing a compound having a cyclohexasilane structure according to claim 1 or 2, wherein the holding step is carried out until the compound having the cyclopentasilane structure in the solution and the compound having the cyclohexasilane structure reach equilibrium.

4. The method for producing a compound having a cyclohexasilane structure according to claim 1, wherein the holding step includes the presence of a silyl anion in the solution.

5. The method for producing a compound having a cyclohexasilane structure according to claim 1, wherein in the holding step, the solution is held at the liquid temperature for 20 minutes or more.

6. The method for producing a compound having a cyclohexasilane structure according to claim 5, wherein in the holding step, the liquid temperature is maintained for 20 minutes or more at a liquid temperature T such that T-5°C < T < T+5°C relative to the liquid temperature T at any given time.

7. The method for producing a compound having a cyclohexasilane structure according to claim 1, wherein the step of preparing the solution includes reacting the silane monomer or linear polysilane with metallic sodium, lithium chloride or a polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon and a solvent at a liquid temperature of 65°C or higher.

8. The method for producing a compound having a cyclohexasilane structure according to claim 7, wherein the reaction step produces a compound having the cyclopentasilane structure by the reaction.

9. The method for producing a compound having a cyclohexasilane structure according to claim 1, wherein in the holding step, the content of the metallic sodium in the solution is 0.1% by mass or more and 2.0% by mass or less with respect to the total mass of the solution.

10. The method for producing a compound having a cyclohexasilane structure according to claim 1, wherein in the holding step, the content of lithium chloride or polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon in the solution is 0.02 mol / kg or more and 0.5 mol / kg or less with respect to the total mass of the solution.

11. The method for producing a compound having a cyclohexasilane structure according to claim 1, wherein the compound having the cyclohexasilane structure is dodecamethylcyclohexasilane.

12. A method for producing a compound having a cyclohexasilane structure according to claim 1, comprising a step of deactivating metallic sodium after the holding step.

13. The method for producing a compound having a cyclohexasilane structure according to claim 1, wherein the liquid temperature of the solution in the step of preparing the solution is 65°C or higher.

14. The method for producing a compound having a cyclohexasilane structure according to claim 10, wherein in the holding step, the content of lithium chloride or polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon in the solution is 0.02 mol / kg or more and 0.08 mol / kg or less with respect to the total mass of the solution.

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