JP7580982B2 - Method for producing cyclic silane hydride compounds - Google Patents

Description

The present invention relates to a method for producing a cyclic hydrogen silane compound.

Thin-film silicon is used in solar cells, semiconductors, etc., and traditionally, this thin-film silicon has been produced by chemical vapor deposition (CVD) using monosilane and other raw materials. In recent years, a method of coating a substrate with a hydrogenated polysilane solution and baking it has also attracted attention as a simpler method of producing thin-film silicon.

Cyclic silane hydride compounds are often used as the hydrogenated polysilanes, and known methods for producing cyclic silane hydride compounds include contacting a salt of a cyclic halosilane compound with an aluminum halide compound (e.g., a Lewis acid compound) to obtain a cyclic halosilane compound, and then contacting the obtained cyclic halosilane compound with a metal hydride to reduce it (Patent Documents 1 and 2).

In Patent Document 1, a cyclic halosilane compound is reduced with a metal hydride, and then purified by concentration or distillation to obtain a cyclic silane hydride compound, which is formed together with an aluminum complex. However, the compound contains a large amount of aluminum compound, and since the presence of a large amount of aluminum affects the electrical properties of the thin film, the amount of the aluminum compound is reduced by washing with water.

U.S. Pat. No. 7,498,015 JP 2017-95324 A

However, in Patent Document 1, the salt of a cyclic halosilane compound is reacted with an aluminum halide compound, the mixture obtained by this reaction is brought into contact with chlorine gas, and then reacted with a reducing agent. This may cause the aluminum complex to precipitate as a residue in the reactor, which may cause the stirring of the reduction reaction or the like to slow down or stop. In addition, the aluminum complex may react with moisture in the air to generate chlorine gas.

Furthermore, when the reduced cyclic silane hydrogen compound is subjected to water washing, there is a risk that the unreacted reducing agent will react violently with water to generate hydrogen, and there is a risk that the cyclic silane hydrogen compound will decompose, resulting in a decrease in purity, etc.

In addition, in Patent Document 2, there was room for efficient separation of the aluminum complex derived from the aluminum halide compound and improvement in the productivity of the cyclic silane hydride compound.

The present invention has been made in light of the above-mentioned circumstances, and the object of the present invention is to provide a method for producing a cyclic silane hydrogen compound, which allows safe and easy handling of the aluminum complex produced by the reaction of a salt of a cyclic halosilane compound with an aluminum halide compound, and which allows the production of a high-purity cyclic silane hydrogen compound with a reduced amount of aluminum.

The gist of the present invention that has solved the problems is as follows.
[1] A method for producing a cyclic silane hydride compound, comprising: step 1, contacting a salt of a cyclic halosilane compound (A) with an aluminum halide compound (B) in a solvent (C) to produce a cyclic halosilane compound (D); step 2, contacting the cyclic halosilane compound (D) with a metal hydride (E) in a solvent (F) to obtain a composition containing a cyclic silane hydride compound (G) and an aluminum complex (H); and step 3, isolating the aluminum complex (H), wherein the step of separating the aluminum complex (H) comprises at least two of the following steps: (a) a filtration step; (b) a separation step of the reaction solution, a concentrate thereof, or a washing solution thereof; and (c) a washing step with an acidic aqueous solution.
[2] The method according to [1], further comprising distilling the cyclic silane hydride compound (G).
[3] The method according to [1] or [2], wherein the molar concentration of the cyclic halosilane compound (D) in step 2 is 0.150 mol/L or more.
[4] The method according to any one of [1] to [3], wherein the ratio of the molar concentration of the cyclic halosilane compound (D) in step 2 to the number of silicon atoms contained in the cyclic halosilane compound (D) is 0.90 mol/L or more.
[5] The production method according to any one of [1] to [4], wherein the step of separating the aluminum complex (H) is (a) a step of separating the reaction solution, a concentrate thereof, or a washing solution thereof, and (b) a step of filtering, or (a) a step of separating the reaction solution, a concentrate thereof, or a washing solution thereof, and (c) a step of washing with an acidic aqueous solution.
[6] The method according to any one of [1] to [5], wherein at least one of the solvent (C) and the solvent (F) is an ether solvent.
[7] The method according to any one of [1] to [6], wherein the cyclic silane hydride compound (G) contains cyclopentasilane or cyclohexasilane.
[8] The method according to [7], wherein the cyclic silane hydrogen compound (G) is cyclohexasilane.

According to the present invention, the aluminum complex produced by the reaction of a salt of a cyclic halosilane compound with an aluminum halide compound can be handled safely and simply, and a high-purity cyclic hydrogen silane compound with a reduced amount of aluminum can be obtained.

The method for producing a cyclic silane hydride compound of the present invention includes step 1 of contacting a salt of a cyclic halosilane compound (A) with an aluminum halide compound (B) in a solvent (C) to produce a cyclic halosilane compound (D), step 2 of contacting the cyclic halosilane compound (D) with a metal hydride (E) in a solvent (F) to obtain a composition containing a cyclic silane hydride compound (G) and an aluminum complex (H), and step 3 of separating the aluminum complex (H), characterized in that the step of separating the aluminum complex (H) includes at least two of the following steps: (a) a filtering step, (b) a step of separating the reaction solution, a concentrated solution thereof, or a washing solution thereof, and (c) a step of washing with an acidic aqueous solution.

The distinctive feature of the present invention is that the aluminum complex is separated by at least two of the following steps (and preferably distillation): a filtration step, a step of separating the reaction solution, its concentrate or their washings, and a step of washing with an acidic aqueous solution. By combining these steps, the aluminum complex produced by the reaction of the salt of the cyclic halosilane compound with the aluminum halide compound can be safely and easily handled, and a cyclic hydrogen silane compound with a reduced amount of aluminum can be obtained with high purity.

Below, steps 1 to 3 performed in the method for producing a cyclic silane hydrogen compound of the present invention will be described in order.

1. Step 1 (Step of Producing Cyclic Halosilane)
Step 1 is a step of contacting a salt of a cyclic halosilane compound (A) with an aluminum halide compound (B) in a solvent (C) to produce a cyclic halosilane compound (D).

Salt of Cyclic Halosilane Compound (A)
The salt of a cyclic halosilane compound is a compound having a structure in which silicon atoms are linked to form a monocyclic ring, and a halogen atom is bonded to at least one silicon atom constituting the monocyclic ring, forming a salt. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The number of silicon atoms constituting the monocyclic ring is not particularly limited, but is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more, and is preferably 8 or less, more preferably 7 or less, and even more preferably 6 or less.

The cyclic halosilane compound may contain silicon atoms that do not constitute a monocyclic ring, for example, a silicon atom that constitutes a monocyclic ring may be bonded to a substituent that contains a silicon atom (e.g., a silyl group, etc.). However, if silicon atoms that do not constitute a monocyclic ring are contained, the amount of silane gas generated tends to increase and the yield of the cyclic hydrogenated silane compound tends to decrease during storage of the salt of the cyclic halosilane compound or the cyclic halosilane compound, or during the process of producing a cyclic hydrogenated silane compound by reducing the obtained cyclic halosilane compound, so it is preferable to contain as few silicon atoms that do not constitute a monocyclic ring as possible.

It is preferable that at least one halogen atom is bonded to the monocyclic ring formed from silicon atoms, it is more preferable that one or two halogen atoms are bonded to each of the silicon atoms constituting the monocyclic ring, and it is even more preferable that two halogen atoms are bonded to each of the silicon atoms constituting the monocyclic ring.

As the salt of the cyclic halosilane compound, it is preferable to use a compound represented by the following formula (1).

In the above formula (1), ^X1 and ^X2 each independently represent a halogen atom, L represents an anionic ligand, p represents an integer of -2 to -1 as the valence of the ligand L, K represents a counter cation, q represents an integer of +1 to +2 as the valence of the counter cation K, n represents an integer of 0 to 5, a, b, and c each represent an integer of 0 to 2n+6 (provided that a+b+c=2n+6 and a and c are not simultaneously 0), d represents an integer of 0 to 3 (provided that a and d are not simultaneously 0), e represents an integer of 0 to 3 (provided that d+e=3), m is 1 to 2, s represents an integer of 1 or more, and t represents an integer of 1 or more.

In the above formula (1), n represents the number of silicon atoms constituting the monocyclic ring, and its value is an integer of 0 to 5, preferably 1 or more, more preferably 2 or more, and preferably 4 or less, more preferably 3 or less. n is particularly preferably 3, that is, the compound represented by formula (1) is preferably a 6-membered silicon monocyclic ring.

In the above formula (1), ^X1 represents a halogen atom bonded to a silicon atom constituting a ring, and ^X2 represents a halogen atom of a silyl group bonded to a silicon atom constituting a ring. The halogen atoms of ^X1 and ^X2 include fluorine atom, chlorine atom, bromine atom, and iodine atom, preferably chlorine atom or bromine atom, more preferably chlorine atom. When there are a plurality of ^X1 , the plurality of ^X1 may be the same or different. When there are a plurality of ^X2 , the plurality of ^X2 may be the same or different.

In the above formula (1), a represents the number of halogen atoms bonded to silicon atoms constituting the ring, b represents the number of hydrogen atoms bonded to silicon atoms constituting the ring, and c represents the number of silyl groups bonded to silicon atoms constituting the ring. d represents the number of halogen atoms of the silyl groups bonded to silicon atoms constituting the ring, and e represents the number of hydrogen atoms of the silyl groups bonded to silicon atoms constituting the ring. When c is 2 or more, the multiple silyl groups bonded to silicon atoms constituting the ring may be the same or different. a, b, and c represent integers of 0 to 2n+6 (wherein a+b+c=2n+6 and a and c are not 0 at the same time), and it is preferable that a is an integer of 1 to 2n+6 and b and c are integers of 0 to n+5, and it is more preferable that a is an integer of n+6 to 2n+6 and b and c are integers of 0 to n.

In addition, in the above formula (1), it is even more preferable that c is 0, since it suppresses side reactions such as coupling reactions when reacted with an aluminum halide compound, improves the storage stability of the salt of the cyclic halosilane compound and the cyclic halosilane compound produced therefrom, suppresses the generation of silane gas in the process of producing a cyclic hydrogen silane compound by reducing the obtained cyclic halosilane compound, and increases the yield of the cyclic hydrogen silane compound. It is particularly preferable that a is 2n+6 and b and c are 0.

In the above formula (1), L represents an anionic ligand coordinated to the silicon atom constituting the ring, p represents the valence of the ligand L (an integer from -2 to -1), and m represents the number of ligands L (+1 to +2). Examples of anionic ligands include halide ions, nitrate ions, and cyanide ions.

In the above formula (1), K represents a counter cation, q represents the valence of the counter cation K (an integer between +1 and +2), and the values of s and t are determined according to the valence and number of the ligand L and the valence of the counter cation K.

Examples of the counter cation K include oniums (e.g., phosphonium ion, ammonium ion, etc.), _{polyamine.SiH2Cl} ⁺ (e.g., _{pedeta.SiH2Cl} ⁺ , _{theeda.SiH2Cl} ⁺ , etc.), etc. When the counter cation K is an onium, it is preferred in that the yield of the cyclic halosilane compound is improved when the cyclic halosilane compound is produced by contacting the salt of the cyclic halosilane compound with the onium.

As the onium of the counter cation K, a phosphonium ion represented by the following formula (2) or an ammonium ion represented by the following formula (3) is preferred.

R ¹ to R ⁴ in the above formula (2) and R ⁵ to R ⁸ in the above formula (3) each independently represent a hydrogen atom, an alkyl group, or an aryl group. In the above formula (2), R ¹ to R ⁴ may each be different, but it is preferable that they are all the same group. In the above formula (3), R ⁵ to R ⁸ may each be different, but it is preferable that they are all the same group.

Preferred examples of the alkyl groups of R ¹ to R ⁴ and R ⁵ to R ⁸ include alkyl groups having 1 to 16 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a cyclohexyl group, and more preferred are alkyl groups having 1 to 8 carbon atoms.

Preferred examples of the aryl group of R ¹ to R ⁴ and R ⁵ to R ⁸ include aryl groups having 6 to 18 carbon atoms, such as a phenyl group and a naphthyl group, and more preferably an aryl group having 6 to 12 carbon atoms. It is preferable that R ¹ to R ⁴ and R ⁵ to R ⁸ are alkyl groups or aryl groups.

Specific examples of salts of the cyclic halosilane compound represented by the above formula (1) include _salts of tetradecachlorocyclohexasilane dianion complex ([ _Si6Cl142- ^] ) and salts of _{tetradecabromocyclohexasilane} dianion complex ([ _Si6Br142- ^] ). The counter ion is preferably a phosphonium ion or an ammonium ion.

As the salt of the cyclic halosilane compound represented by the above formula (1), it is preferable to use a compound represented by the following formula (4) or formula (5). When such a compound is used as the salt of the cyclic halosilane compound, the production of by-products and the production of silane gas, which is a pyrophoric gas, are suppressed when the salt of the cyclic halosilane compound is reacted with an aluminum halide compound, so that the cyclic halosilane compound can be easily produced. In addition, the obtained cyclic halosilane compound can be reduced to efficiently produce a cyclic hydrogen silane compound.

In the above formulas (4) and (5), ^X1 , ^R1 to ^R4 , ^R5 to ^R8 , n and a are the same as above, and ^X3 represents a halogen atom. Note that ^X3 exists in the form of an ion in the above formulas (4) and (5), and is a halide ion.

The halogen atom of ^X3 includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, preferably a chlorine atom or a bromine atom, and more preferably a chlorine atom.

When there are a plurality of X ^{3 s} , the plurality of X ^{3 s} may be the same or different.

^X1 and ^X3 may be the same or different. In the formulas (4) and (5), when ^X1 and ^X3 are all chlorine atoms, the cyclic silane hydrogen compound can be produced at low cost.

In the above formula (4) and formula (5), n represents an integer of 0 to 5, and a represents an integer of 1 to 2n+6, with n being particularly preferably 3, and in this case, a is preferably 6 or more, more preferably 9 or more, and particularly preferably 12 or more.

The salt of the cyclic halosilane compound may be produced by contacting a halosilane compound (preferably a monosilane halide, more preferably a trihalogenated silane, and even more preferably trichlorosilane) with a tertiary polyamine, or by contacting a halosilane compound with at least one of a phosphonium salt (preferably a quaternary phosphonium salt) and an ammonium salt (preferably a quaternary ammonium salt), and is preferably produced by contacting a halosilane compound with at least one of a phosphonium salt and an ammonium salt (hereinafter also referred to as a cyclization coupling step).

For example, when trichlorosilane is used as the halosilane compound and a phosphonium salt is used, salts consisting _of a dianion of a _cyclic halosilane compound and a phosphonium ion can be _obtained , such as dodecachlorodihydrocyclohexasilane dianion salt (e.g., [ _Ph4P ⁺ ] ₂ [ _Si6H2Cl12 ] ^2- ), tridecachlorohydrocyclohexasilane dianion salt (e.g., [ _Ph4P ⁺ _{] 2} [ _Si6HCl13 ] ^2- ), or tetradecachlorocyclohexasilane dianion salt (e.g., [ _Ph4P ⁺ ] ₂ [ _Si6Cl14 ] ^2- ).

Furthermore, when trichlorosilane is used as the halosilane compound and an ammonium salt is used, salts consisting of _a dianion of a cyclic halosilane compound and an ammonium ion can _{be obtained} , such as dodecachlorodihydrocyclohexasilane dianion salt (e.g., [ _Et4N ⁺ ] ₂ [ _Si6H2Cl12 ] ^2- ), tridecachlorohydrocyclohexasilane dianion salt (e.g., [ _Et4N ⁺ ] ₂ [ _Si6HCl13 ] ^2- ), and tetradecachlorocyclohexasilane dianion salt ( ^e.g. , [ _Et4N ⁺ ] ₂ [ _Si6Cl14 ] _2- ).

The cyclization coupling step may be carried out in the presence of a chelating ligand such as a polyether compound (preferably 1,2-dimethoxyethane), a polythioether compound, or a multidentate phosphine compound (preferably 1,2-bis(diphenylphosphino)ethane).

The cyclization coupling step may be carried out in the presence of a basic compound. Examples of the basic compound include (mono-, di-, tri-, and poly-)amine compounds, and among these, monoamine compounds are preferably used. Specifically, for example, triethylamine, tripropylamine, tributylamine, trioctylamine, triisobutylamine, triisopentylamine, diethylmethylamine, diisopropylethylamine, dimethylbutylamine, dimethyl-2-ethylhexylamine, diisopropyl-2-ethylhexylamine, and methyldioctylamine are preferred, with tributylamine being particularly preferred. The basic compounds may be used alone or in combination of two or more.

The salt of the cyclic halosilane compound may be purified as necessary prior to reaction with the aluminum halide compound. By purifying the salt of the cyclic halosilane compound to increase its purity, it is possible to suppress the generation of by-products in the reaction with the aluminum halide compound. The salt of the cyclic halosilane compound may be purified using known purification methods such as solid-liquid separation, distillation (solvent removal), crystallization, extraction, etc. The solid-liquid separation means used here is not particularly limited, and known solid-liquid separation means such as filtration, precipitation separation, centrifugation, decantation, etc. may be used.

Aluminum halide compound (B)
Examples of the aluminum halide compound include Lewis acid compounds such as aluminum fluoride compounds, aluminum chloride compounds, aluminum bromide compounds, and aluminum iodide compounds.

The aluminum halide compound is preferably aluminum chloride or aluminum bromide, and is more preferably an aluminum chloride compound in terms of reactivity and ease of reaction control.

As long as the effects of the present invention are achieved, the following compounds may be used in combination with the aluminum halide compound.
Specific examples of the halogen include titanium halides such as titanium chloride and titanium bromide; zirconium halides such as zirconium chloride and zirconium bromide; copper halides such as copper chloride and copper bromide; silver halides such as silver chloride and silver bromide; gold halides such as gold chloride and gold bromide; boron halides such as boron trifluoride, boron trichloride and boron tribromide; gallium halides such as gallium chloride and gallium bromide; indium halides such as indium chloride and indium bromide; thallium halides such as thallium chloride and thallium bromide; calcium halides such as calcium chloride and calcium bromide; iron halides such as iron chloride and iron bromide; zinc halides such as zinc chloride and zinc bromide; and the like.

The amount of the aluminum halide compound (preferably a Lewis acid compound) used may be adjusted as appropriate depending on the reactivity between the salt of the cyclic halosilane compound and the aluminum halide compound, but for example, it is preferably 0.5 mol or more, more preferably 1.5 mol or more, and preferably 20 mol or less, more preferably 10 mol or less, per 1 mol of the salt of the cyclic halosilane compound.

Solvent (C)
The salt of the cyclic halosilane compound is contacted with the aluminum halide compound (preferably a Lewis acid compound) in a solvent or dispersion medium (hereinafter, simply referred to as the solvent).
The solvent (C) (hereinafter sometimes referred to as reaction solvent (I)) is preferably an organic solvent.
Examples of the solvent (C) include aliphatic hydrocarbon solvents such as hexane, heptane, octane, nonane, and decane; aromatic hydrocarbon solvents such as benzene and toluene; and ether solvents such as diethyl ether, tetrahydrofuran, cyclopentyl methyl ether, diisopropyl ether, and methyl tertiary butyl ether.

The solvent (C) is preferably a hydrocarbon solvent, which facilitates the dissolution of residues after contacting the salt of the cyclic halosilane compound with the aluminum halide compound (preferably a Lewis acid compound).
Among them, the solvent (C) is particularly preferably an aliphatic hydrocarbon solvent, and most preferably hexane. These solvents may be used alone or in combination of two or more. It is preferable that the solvent is purified in advance by distillation, dehydration, or the like in order to remove water and dissolved oxygen contained therein.

The amount of solvent (C) used is preferably 1 to 1,000 parts by mass, more preferably 10 to 800 parts by mass, and even more preferably 100 to 600 parts by mass, per 100 parts by mass of the total amount of the salt of the cyclic halosilane compound and the aluminum halide compound.

In other words, the amount of solvent (C) used is preferably adjusted so that the concentration of the salt of the cyclic halosilane compound is 0.005 mol/L or more and 10 mol/L or less, more preferably 0.01 mol/L or more, even more preferably 0.05 mol/L or more, more preferably 5 mol/L or less, and even more preferably 1 mol/L or less.

The method of contacting the salt of the cyclic halosilane compound with the aluminum halide compound (preferably a Lewis acid compound) in the reaction solvent (I) is not particularly limited, but examples include (1) a method in which the salt of the cyclic halosilane compound and the Lewis acid compound are each dissolved or dispersed in a solvent in advance to prepare a solution (or dispersion) of the salt of the cyclic halosilane compound and a solution (or dispersion) of the Lewis acid compound, and then these solutions (or dispersions) are mixed; (2) a method in which the salt of the cyclic halosilane compound and the Lewis acid compound are added simultaneously or sequentially to the solvent; (3) a method in which a Lewis acid compound is added to a solution (or dispersion) of the salt of the cyclic halosilane compound; and (4) a method in which the salt of the cyclic halosilane compound and the Lewis acid compound are charged and then a solvent is added; etc.

The temperature at which the salt of the cyclic halosilane compound is contacted with the aluminum halide compound (preferably a Lewis acid compound) to react may be adjusted appropriately depending on the reactivity, but is preferably -80°C or higher, more preferably -50°C or higher, even more preferably -30°C or higher, and preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 100°C or lower.

The time for contacting the salt of the cyclic halosilane compound with the aluminum halide compound (preferably a Lewis acid compound) may be set appropriately depending on the reaction temperature and the degree of progress of the reaction, but is preferably, for example, 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more. The time can be, for example, 24 hours or less. The time is more preferably 20 hours or less, and even more preferably 15 hours or less.

Heating and/or stirring may be performed to promote the reaction between the salt of the cyclic halosilane compound and the aluminum halide compound (preferably a Lewis acid compound).

The atmosphere in which the salt of the cyclic halosilane compound is contacted with the aluminum halide compound (preferably a Lewis acid compound) to react is not particularly limited, but in order to suppress oxidation of the cyclic halosilane compound and its salt, the oxygen concentration of the atmosphere is preferably 9% by volume or less, more preferably 5% by volume or less, even more preferably 3% by volume or less, and particularly preferably 1% by volume or less.

In addition, in order to suppress hydrolysis of the cyclic halosilane compound and its salt, the moisture concentration of the atmosphere is preferably 2000 ppm (volume basis) or less, more preferably 1500 ppm (volume basis) or less, even more preferably 1000 ppm (volume basis) or less, even more preferably 500 ppm (volume basis) or less, particularly preferably 150 ppm (volume basis) or less, and most preferably 10 ppm (volume basis) or less.

The reaction between the salt of the cyclic halosilane compound and the aluminum halide compound (preferably a Lewis acid compound) is preferably carried out in an inert gas atmosphere (e.g., nitrogen gas or argon gas) and is also preferably carried out in the dark.

Cyclic halosilane compound (D)
By contacting and reacting the salt of the cyclic halosilane compound with an aluminum halide compound (preferably a Lewis acid compound), a free cyclic halosilane compound (a non-complex type cyclic halosilane compound) can be obtained together with a residue (aluminum complex). Such a non-complex type cyclic halosilane compound has a higher solvent solubility than a complex type cyclic halosilane compound. Therefore, when the obtained non-complex type cyclic halosilane compound is contacted with a metal hydride and reduced, the reduction reaction of the cyclic halosilane compound can be carried out at a high concentration, and a cyclic silane hydride compound can be efficiently produced.

In the step of contacting the salt of the cyclic halosilane compound with the aluminum halide compound, for example, a cyclic halosilane compound represented by the following formula (6) can be obtained from the salt of the cyclic halosilane compound represented by the above formula (1).

In the above formula (6), X ¹ , X ² , a to e, and n have the same meanings as above.

On the other hand, the cyclic halosilane compound obtained by the reaction of the salt of the cyclic halosilane compound with the Lewis acid compound may be purified as necessary to remove impurities. The cyclic halosilane compound can be purified by known means such as solid-liquid separation, distillation (solvent removal), crystallization, extraction, etc.

2. Step 2 (Step of Obtaining a Composition Containing a Cyclic Silane Hydrogen Compound and an Aluminum Complex)
Step 2 is a step of contacting the cyclic halosilane compound (D) with a metal hydride (E) in a solvent (F) to obtain a composition containing a cyclic silane hydride compound (G) and an aluminum complex (H).

The cyclic halosilane compound obtained by contacting the salt of the cyclic halosilane compound with an aluminum halide compound (Lewis acid compound) is reduced by contacting it with a metal hydride using a known method (hereinafter sometimes referred to as the reduction step) to produce a cyclic silane hydride compound (G).

The molar concentration of the cyclic halosilane compound (D) used in the reaction with the metal hydride (E) (i.e., the molar concentration of the cyclic halosilane compound (D) in step 2) is, from the viewpoint of increasing the yield and purity of the cyclic silane hydride compound, preferably 0.150 mol/L or more, more preferably 0.155 mol/L or more, even more preferably 0.160 mol/L or more, or 0.165 mol/L or more, and is preferably 1.000 mol/L or less, more preferably 0.900 mol/L or less, and even more preferably 0.850 mol/L or less.
Here, the cyclic halosilane compound (D) (solution) or the metal hydride (solution) may be added all at once, or may be added continuously or stepwise. In this case, the molar concentration of the cyclic halosilane compound (D) in step 2 may be the molar concentration of the total amount of the cyclic halosilane compound used in step 2 relative to the total amount of the solvent used in step 2.

The ratio of the molar concentration of the cyclic halosilane compound (D) to the number of silicon atoms contained in the cyclic halosilane compound (D) in step 2 is preferably 0.90 mol/L or more, more preferably 0.95 mol/L or more, even more preferably 1.00 mol/L or more, and is preferably 5.00 mol/L or less, more preferably 4.90 mol/L or less, even more preferably 4.80 mol/L or less.
The ratio may be a value that simultaneously satisfies the above molar concentrations of the cyclic halosilane compound (D), and may be applied to any of the cases of addition in one go, continuous addition, or divided addition.

Metal hydrides (E)
The metal hydride (E) is a conventionally known reducing agent, and is preferably one or more selected from the group consisting of aluminum-based reducing agents and boron-based reducing agents. Examples of the aluminum-based reducing agent include metal hydrides such as lithium aluminum hydride (LiAlH ₄ ; LAH), diisobutylaluminum hydride (DIBAL), and sodium bis(2-methoxyethoxy)aluminum hydride ["Red-Al" (registered trademark of Sigma-Aldrich)]. Examples of the boron-based reducing agent include metal hydrides such as sodium borohydride and lithium triethylborohydride, and diborane, and it is preferable to use a metal hydride. The reducing agent may be used alone or in combination of two or more. Among them, lithium aluminum hydride is particularly preferable.

The amount of metal hydride (E) used may be set appropriately. For example, it is preferable that the equivalent of hydride in the reducing agent per silicon-halogen bond of the cyclic halosilane is at least 0.9 equivalents. The amount of metal hydride (E) used is more preferably 1.0 to 50 equivalents, even more preferably 1.0 to 30 equivalents, particularly preferably 1.0 to 15 equivalents, and most preferably 1.0 to 2 equivalents. If too much metal hydride (E) is used, post-treatment takes time and productivity tends to decrease. On the other hand, if too little metal hydride (E) is used, halogens remain unreduced, tending to decrease yield.

Solvent (F)
The reduction reaction of the cyclic halosilane compound with a metal hydride is preferably carried out in a solvent (F). The solvent used here (hereinafter sometimes referred to as reaction solvent (II)) is preferably an organic solvent, such as a hydrocarbon solvent such as hexane or toluene; an ether solvent such as diethyl ether, tetrahydrofuran, cyclopentyl methyl ether, diisopropyl ether, or methyl tertiary butyl ether; or the like. These solvents may be used alone or in combination of two or more. It is preferable that the reaction solvent (II) used in the reduction step is purified, such as by distillation or dehydration, before the reaction in order to remove water and dissolved oxygen contained therein.

At least one of the solvent (C) and the solvent (F) is preferably an ether solvent, and the solvent (F) is more preferably an ether solvent.
The solvent (F) is preferably a solvent for the metal hydride (E), and the solvent (C) is preferably a solvent for the cyclic halosilane compound (D). During the reduction reaction, both the solvent (C) and the solvent (F) may be present.

The amount of solvent (F) used may be any amount that corresponds to the amount of metal hydride used, as described above, and is preferably 1 to 10,000 parts by mass, more preferably 100 to 5,000 parts by mass, and even more preferably 400 to 2,000 parts by mass, per 100 parts by mass of metal hydride.

In one embodiment of the present invention, the reaction solution produced in step 2 may be recovered without concentrating it or by concentrating the reaction solution produced in step 2. When the reaction solution is concentrated, the reaction solution may be concentrated to preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more of the original volume, and then the upper layer may be recovered by liquid separation.
The reaction mixture may be separated into multiple layers by concentration.
The multiple layers may include, for example, (i) an upper layer and a lower layer, (ii) an upper layer, a middle layer and a lower layer, etc.
The concentration may be any operation that volatilizes the solvent contained in the reaction solution by changing the temperature, pressure, or the like, and examples of the concentration include reduced pressure treatment and heat treatment.
The separation may be any operation that extracts or removes a layer containing a desired substance from a plurality of layers, and examples thereof include separation by decantation, separation using a funnel, and the like.

In one embodiment of the present invention, the upper layer preferably contains a cyclic silane hydride compound, and the lower layer preferably contains an aluminum complex. The lower layer may be concentrated under reduced pressure and filtered to remove the aluminum complex, and the lower layer from which the aluminum complex has been removed may be used together with the upper layer in the next step (preferably a distillation step).

Cyclic silane hydride compound (G)
The cyclic hydrogenated silane compound has a monocyclic ring formed by a series of silicon atoms, and is a compound formed of silicon atoms and hydrogen atoms. The cyclic hydrogenated silane compound may have hydrogen atoms bonded to all of the substitution positions of the silicon atoms forming the monocyclic ring, or may have unsubstituted silyl groups bonded to the silicon atoms forming the monocyclic ring. However, from the viewpoint of storage stability, it is preferable that the cyclic hydrogenated silane compound does not contain silicon atoms other than the silicon atoms forming the monocyclic ring. By reducing the cyclic halosilane compound rather than the salt of the cyclic halosilane compound, no silane gas is generated due to the counter cation of the salt, and the generation of silane gas can be suppressed overall, so that the cyclic hydrogenated silane compound can be obtained easily and in high yield.

The cyclic silane hydride compound obtained in the reduction step is preferably a compound represented by the following formula (12).
Si _z H _2z (12)

In the above formula (12), z represents the number of silicon atoms constituting the monocyclic ring, and z is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more, and is preferably 8 or less, more preferably 7 or less, and even more preferably 6 or less.

The cyclic hydrogen silane compound is an oxygen-inhibiting substance. Therefore, it is preferable to carry out the reduction step under an inert gas atmosphere such as nitrogen gas or argon gas.

The cyclic hydrogen silane compound (G) preferably contains cyclopentasilane or cyclohexasilane, and more preferably cyclohexasilane.

The content of cyclohexasilane is preferably 97% by mass or more, more preferably 97.5% by mass or more, and even more preferably 98.0% by mass or more, based on 100% by mass of the cyclic hydrogen silane compound (G). It is desirable that the content of cyclohexasilane is as close to 100% by mass as possible, but it may be 99.9% by mass or less or 99.7% by mass or less.
The content may be based on area percentage obtained from gas chromatography analysis.

Aluminum Complex (H)
The aluminum complex (H) is preferably a salt of an aluminum halide compound formed by contacting an aluminum halide compound with a solvent (F) (preferably an ether-based solvent), and preferably contains the salt of an aluminum halide compound as a main component in an amount of 50 mass % or more (preferably 60 mass % or more, more preferably 70 mass % or more, even more preferably 80 mass % or more, and still more preferably 90 mass % or more).

3. Step 3 (step of separating aluminum complex)
Step 3 is a step of separating the aluminum complex (H).
The step of separating the aluminum complex (H) includes at least two of the following steps: (a) a filtration step; (b) a separation step of the reaction liquid, a concentrate thereof, or a washing solution thereof; and (c) a washing step with an acidic aqueous solution.

The filtration step may be filtration carried out under normal pressure and temperature, or may be filtration carried out by changing the pressure or temperature.
Examples of the filtration include natural filtration, reduced pressure filtration, pressure filtration, centrifugal filtration, and hot filtration.
For filtration, filter paper, glass fiber filters, membrane filters, filter plates, etc. can be used.
In the present invention, the filtration step is preferably carried out on the upper or lower layer of the reaction liquid, its concentrate or a washing solution thereof, and more preferably on the lower layer of the reaction liquid, its concentrate or a washing solution thereof.
In the present invention, the aluminum complex cannot be sufficiently removed by the filtration step alone.

Separation may be any operation that extracts or removes a layer containing a desired substance from the multiple layers that are produced, and may be any of the following: separation of a reaction solution that has separated into layers during a reaction; separation of layers that have separated when washed with an acidic aqueous solution, water, or a solvent; separation of layers that have separated due to concentration, dilution, temperature change, pressure change, etc.; separation of layers that have separated due to the addition of an additive that promotes layer separation. There are no particular limitations on the separation, and it may be performed by a known method, such as separation by decantation or separation using a funnel.

The reaction liquid is a composition containing a cyclic hydrogen silane compound (G) and an aluminum complex (H), the concentrated liquid is a liquid obtained by volatilizing the solvent contained in the composition by reducing the pressure or heating the composition, and the cleaning liquid is a solution obtained after contacting the reaction liquid or its concentrated solution with an acidic aqueous solution, as described below.

The step of washing with an acidic aqueous solution may be any operation in which the reaction liquid or a concentrated solution thereof is brought into contact with an acidic aqueous solution.
When washing with an acidic aqueous solution, the contact between the reaction liquid containing the cyclic silane hydrogen compound or a concentrate thereof and the acidic aqueous solution is preferably carried out by dropping at least one of the reaction liquid containing the cyclic silane hydrogen compound or a concentrate thereof and the acidic aqueous solution. By dropping one or both of the reaction liquid containing the cyclic silane hydrogen compound or a concentrate thereof and the acidic aqueous solution in this manner, the metal hydride can be deactivated more mildly than by washing with water, and the generated heat can be adjusted by the dropping speed, etc.

There are three preferred modes for dropping either or both of the reaction liquid or concentrated solution thereof containing the cyclic silane hydrogen compound and the acidic aqueous solution. That is, A) a mode in which a reaction liquid or concentrated solution thereof containing the cyclic silane hydrogen compound is charged in a reactor and an acidic aqueous solution is dropped thereto, B) a mode in which an acidic aqueous solution is charged in a reactor and a reaction liquid or concentrated solution thereof containing the cyclic silane hydrogen compound is dropped thereto, and C) a mode in which a reaction liquid or concentrated solution thereof containing the cyclic silane hydrogen compound and an acidic aqueous solution are dropped into a reactor simultaneously or sequentially. Among these, the mode B) is preferred, that is, it is preferred to drop the reaction liquid or concentrated solution thereof containing the cyclic silane hydrogen compound into the acidic aqueous solution.
In the present invention, it is preferable to separate the reaction liquid or a concentrate thereof into an upper layer and a lower layer by a step of separating the reaction liquid or a concentrate thereof.

The acidic aqueous solution may be an aqueous solution of hydrochloric acid, nitric acid, sulfuric acid, etc. A preferred acidic aqueous solution is an aqueous solution of sulfuric acid.
The concentration of the acidic aqueous solution is, for example, 0.1 to 20% by mass, preferably 0.5 to 15% by mass, and more preferably 1 to 10% by mass.

Specific examples of the process for separating the aluminum complex include (i) a filtration process and a process for separating the reaction liquid, its concentrate or their washings, (ii) a filtration process and a process for washing with an acidic aqueous solution, (iii) a process for separating the reaction liquid, its concentrate or their washings and a process for washing with an acidic aqueous solution, and (iv) a filtration process, a process for separating the reaction liquid, its concentrate or their washings and a process for washing with an acidic aqueous solution.

Among these, from the viewpoint of safe and simple handling of the aluminum complex produced by the reaction of the salt of a cyclic halosilane compound with an aluminum halide compound, the step of separating the aluminum complex (H) is preferably (a) a step of separating the reaction liquid, a concentrate thereof, or a washing solution thereof, and (b) a step of filtering, or (a) a step of separating the reaction liquid, a concentrate thereof, or a washing solution thereof, and (c) a step of washing with an acidic aqueous solution, and more preferably (a) a step of separating an upper layer and a lower layer formed by the reaction liquid, a concentrate thereof, or a washing solution thereof, and (b) a step of filtering the obtained lower layer, or (c) a step of washing the reaction liquid or a concentrate thereof with an acidic aqueous solution, and (a) a step of separating an upper layer and a lower layer formed by the washing solution used for washing.
The lower layer obtained by the separation may be subjected to a filtration step, and the filtered lower layer may be combined with the upper layer.

The cyclic silane hydride compound obtained in the reduction step may be purified to increase its purity. As a method for purifying the cyclic silane hydride compound, known purification methods such as solid-liquid separation, distillation, crystallization, extraction, etc. can be used.
Among these, it is preferable that the method further comprises distilling the cyclic silane hydride compound after the step of separating the aluminum complex.
By separating the aluminum complex and then distilling the cyclic silane hydride compound, a high-purity cyclic silane hydride compound with a reduced amount of aluminum can be obtained.

The solution containing the purified cyclic silane hydrogen compound is further purified by distillation. If necessary, the solution containing the cyclic silane hydrogen compound may be concentrated, and then the highly concentrated cyclic silane hydrogen compound (preferably cyclohexasilane) may be distilled. This distillation is preferably vacuum distillation. There are no particular limitations on the method of vacuum distillation, and it may be performed using a known distillation column, and it may be performed under light-shielding conditions. The above distillation is preferably performed by dividing the fraction into multiple fractions, and only the appropriate fraction may be selected from the obtained fractions.

In particular, the distillation (particularly reduced pressure distillation) may be carried out two or more times. For example, a solution containing a cyclic silane hydrogen compound may be distilled under reduced pressure to recover a fraction having an appropriate content of the cyclic silane hydrogen compound (particularly cyclohexasilane) (first distillation), and the recovered fraction may be distilled under reduced pressure again to recover a fraction having an appropriate content of the cyclic silane hydrogen compound (particularly cyclohexasilane) (second distillation), and the second distillation may be repeated as necessary.

The purity of the cyclic hydrogenated silane compound obtained by the manufacturing method of the present disclosure (hereinafter also referred to as the "cyclic hydrogenated silane compound of the present disclosure"), i.e., the content of the cyclic hydrogenated silane compound in the cyclic hydrogenated silane compound-containing composition of the present disclosure, is preferably 97.5 mass% or more, more preferably 98.0 mass% or more, and even more preferably 98.5 mass% or more, based on 100 mass% of the cyclic hydrogenated silane compound (G), and is preferably as close to 100 mass% as possible, but may be 99.9 mass% or less or 99.7 mass% or less. It is preferable that cyclohexasilane is in the above range.

The aluminum concentration in the cyclic silane hydrogen compound of the present disclosure or the composition containing the cyclic silane hydrogen compound of the present disclosure is preferably 3000 ppm or less, more preferably 2500 ppm or less, even more preferably 2000 ppm or less, even more preferably 1500 ppm or less, and is preferably 0.01 ppb or more.

The present invention has been described above, but a combination of two or more of the individual preferred embodiments of the present invention described above is also a preferred embodiment of the present invention.

The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is of course possible to carry out the invention with modifications within the scope of the above and below-mentioned aims, and all such modifications are included in the technical scope of the present invention.

Measurement and analysis equipment for aluminum content: Multi-type ICP emission spectrometer (Shimadzu Corporation ICPE-9000)
The pretreatment was carried out as follows. First, in a glove box under a nitrogen atmosphere, 50 μL of the cyclic hydrogenated silane compound was placed in a 100 mL PFA (polytetrafluoroethylene) container, and then 2500 μL of 12.5% TMAH (tetramethylammonium hydride aqueous solution) was placed in the container. The container was lightly closed and left to stand overnight to inactivate the compound. After standing overnight, the container was diluted with 45 ml of 5% HNO ₃ and further left to stand overnight to complete the pretreatment.
The amount of Al in the pretreated cyclic silane hydride compound was measured using an ICPE-9000 manufactured by Shimadzu Corporation.

Measurement of the content of cyclic silane hydride compound In a glove box under a nitrogen atmosphere, the obtained cyclic silane hydride compound was diluted to about 1% with cyclopentyl methyl ether, and the solution was measured by gas chromatography (GC). The content of the cyclic silane hydride compound was calculated by the area percentage method.
(Gas Chromatography (GC) Analysis Method)
Measurement method: GC FID method Analysis equipment: Shimadzu GC2014
Column: DB-5MS 0.25μm (Film) x 0.25mm (Diam) x 30m (Length) (Agilent Technologies)
Vaporizer temperature: 250 degrees Detector temperature: 280 degrees Heating conditions: Hold at 50 degrees for 5 minutes, heat to 250 degrees at 20 degrees/min, heat to 280 degrees at 10 degrees/min and hold for 10 minutes

Example 1
(1) Example of the preparation of a salt (A) of a cyclic halosilane compound After replacing the inside of a 300 mL four-neck flask equipped with a thermometer, a condenser, a dropping funnel and a stirrer with nitrogen gas, 123.5 g (0.59 mol) of tetraethylammonium bromide, 490.0 g (2.64 mol) of tributylamine and 702.7 g of dichloromethane were placed in the flask. Then, while stirring the solution in the flask, a solution consisting of 238.1 g (1.76 mol) of trichlorosilane and 117.2 g of dichloromethane was slowly dropped from the dropping funnel under a condition of 25°C. After the dropping was completed, the mixture was stirred for 2 hours, and then stirred while heating at 50°C for 6 hours to carry out a cyclization coupling reaction. After the reaction, the obtained solid was filtered and purified to obtain 102.7 g of a salt (A) of a cyclic halosilane compound.

(2) Production Example of Cyclic Halosilane Compound (D) In a nitrogen atmosphere, 15.0 g of the white solid obtained in (1) above and 4.6 g of powdered aluminum chloride ( _AlCl3 ) serving as aluminum halide compound (B) were placed in a 300 mL three-neck flask equipped with a stirrer, and 98.7 g of hexane serving as solvent (C) was then added. The mixture was reacted for 3 hours under stirring at room temperature in a light-shielded state, and then filtered and concentrated to obtain a hexane solution of cyclic halosilane compound (D) (concentration: about 40% by mass).

(3) Production Example of Cyclic Hydrogenated Silane Compound (G) 25 g of the hexane solution of the cyclic halosilane compound (D) obtained in (2) above was placed in a 100 mL three-neck flask equipped with a dropping funnel and a stirrer. After replacing the atmosphere in the flask with nitrogen gas, 76 mL of a diethyl ether solution of lithium aluminum hydride (E) (concentration: about 1.0 mol/L) was gradually dropped from the dropping funnel under 0°C while stirring the solution in the flask, and then the mixture was stirred at 25°C for 1 hour to carry out a reduction reaction. After the reaction, the reaction solution was separated into two layers by reducing the pressure, and the lower layer contained the aluminum complex (H). The lower layer was separated by liquid separation, concentrated under reduced pressure until the hexane concentration was 5% or less, and then filtered to remove the precipitated aluminum complex (H). The lower layer from which the aluminum complex (H) had been removed was mixed with the upper layer and purified by distillation to obtain 1.6 g of cyclohexasilane as a cyclic silane hydrogen compound (G) having an area purity of 99% as determined by gas chromatography and an aluminum concentration of 1,300 ppm.

Example 2
(3) Production Example of Cyclic Hydrogenated Silane Compound (G) 25 g of the hexane solution of the cyclic halosilane compound (D) obtained in Example 1 (2) above was placed in a 100 mL three-neck flask equipped with a dropping funnel and a stirrer. After replacing the atmosphere in the flask with nitrogen gas, 76 mL of a diethyl ether solution of lithium aluminum hydride (E) (concentration: about 1.0 mol/L) was gradually dropped from the dropping funnel under 0°C conditions while stirring the solution in the flask, and then the solution was stirred at 25°C for 1 hour to carry out a reduction reaction. After the reaction, the reaction solution obtained was separated into two layers, and the lower layer contained the aluminum complex (H). This two-layered solution was slowly dropped into a 5% aqueous sulfuric acid solution, and after stirring for 10 minutes, the lower layer of the two-layered layer was extracted, and the upper layer was purified by distillation to obtain 1.6 g of cyclohexasilane as the cyclic hydrogenated silane compound (G) having an area purity of 99% by gas chromatography and an aluminum concentration of 160 ppm.

According to the present invention, the aluminum complex produced by the reaction of a salt of a cyclic halosilane compound with an aluminum halide compound can be handled safely and simply. A cyclic hydrogenated silane compound with a reduced amount of aluminum and high purity is useful, for example, as a silicon raw material used in solar cells, semiconductors, etc. In the semiconductor field, it can also be used to produce SiGe compounds and SiGe films by mixing or reacting with a Ge compound.

Claims (8)

Step 1: contacting a salt of a cyclic halosilane compound (A) with an aluminum halide compound (B) in a solvent (C) to produce a cyclic halosilane compound (D);
Step 2 of contacting the cyclic halosilane compound (D) with a metal hydride (E) in a solvent (F) to obtain a composition containing a cyclic silane hydride compound (G) and an aluminum complex (H); and Step 3 of isolating the aluminum complex (H).
Including,
the step of separating the aluminum complex (H) includes at least two of the following steps: (a) a filtration step; (b) a step of separating the reaction liquid, a concentrate thereof, or a washing solution thereof (excluding separation by decantation) ; and (c) a step of washing with an acidic aqueous solution ;
A method for producing a cyclic silane hydride compound, comprising at least one of (b) a step of separating the reaction solution, a concentrated solution thereof, or a washing solution thereof (excluding separation by decantation) and (c) a step of washing with an acidic aqueous solution . The method of claim 1 further comprising distilling the cyclic hydrogen silane compound (G). The method according to claim 1 or 2, wherein the molar concentration of the cyclic halosilane compound (D) in step 2 is 0.150 mol/L or more. The method according to any one of claims 1 to 3, wherein the ratio of the molar concentration of the cyclic halosilane compound (D) in step 2 to the number of silicon atoms contained in the cyclic halosilane compound (D) is 0.90 mol/L or more. The production method according to any one of claims 1 to 4, wherein the step of separating the aluminum complex (H) comprises (a) a step of separating the reaction solution, a concentrate thereof, or a washing solution thereof ( excluding separation by decantation) and (b) a filtration step, or (a) a step of separating the reaction solution, a concentrate thereof, or a washing solution thereof (excluding separation by decantation) and (c) a step of washing with an acidic aqueous solution. The method according to any one of claims 1 to 5, wherein at least one of the solvent (C) and the solvent (F) is an ether solvent. The method according to any one of claims 1 to 6, wherein the cyclic hydrogen silane compound (G) contains cyclopentasilane or cyclohexasilane. The method according to claim 7, wherein the cyclic hydrogen silane compound (G) is cyclohexasilane.