JP2018162169A - Method for producing cyanofluoroboric acid salt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a cyanofluoroboric acid salt at a high yield.SOLUTION: In the presence of a trialkylsilyl halide represented by (R)SiX (1) (wherein, R1 is an alkyl group having 1 to 6 carbon atoms which may be the same group or a different group, and X is a halogen atom), a tetrafluoroboric acid salt represented by (M)[BF](2) (wherein, (M)is a monovalent cation) is reacted with a cyanide represented by (M)CN(3) (wherein, (M)is a monovalent cation) to produce a cyanofluoroboric acid salt represented by (M)[BF(CN)](4) (wherein, (M)is the softer cation in HSAB theory of (M)in the formula (2) and (M)in the formula (3), and (a) is an integer of 1 to 3).SELECTED DRAWING: None

Description

  The present invention relates to a novel process for producing cyanofluoroborate.

  In recent years, non-aqueous electrolytes in electrochemical devices such as lithium primary batteries, lithium secondary batteries, electrolytic capacitors, electric double layer capacitors, electrochromic display elements, dye-sensitized solar cells, etc. As a medium for organic synthesis and the like, many studies have been made on cyanofluoroborate, which is an ionic liquid, from the viewpoint of long-term reliability, durability, and safety.

  Although cyanofluoroborate is a useful compound as described above, it is a compound containing a cyano group, and various investigations have been made on its production method. In a conventional manufacturing method, a method of manufacturing using alkali cyanide, which is a poison, as a raw material has been the mainstream (see, for example, Patent Document 1 and Non-Patent Document 1).

  Specifically, Patent Document 1 discloses a method in which sodium tetrafluoroborate and sodium cyanide are melted and reacted in the presence of lithium chloride. Patent Document 2 discloses a method of reacting boron tribromide and potassium cyanide in the presence of tetra-n-butylammonium bromide.

  However, these methods have room for improvement in that the yield of the obtained cyanofluoroborate is low. In particular, in Patent Document 2, in order to increase the yield, the reaction time must be lengthened (for example, one week or longer), and improvement in the productivity of cyanofluoroborate has been demanded.

  On the other hand, a method for producing cyanofluoroborate without using alkali cyanide as a raw material has been studied (see, for example, Patent Document 2 and Non-Patent Documents 1 and 2).

  Specifically, Patent Document 2 discloses a method of reacting a fluoroborate with a trialkylsilyl cyanide. However, this method also has room for improvement in that the reaction time is long and the yield is low.

  In terms of improving the yield, Non-Patent Documents 1 and 2 disclose a method of reacting sodium tetrafluoroborate with trimethylsilylcyanide in the presence of trimethylsilyl chloride. In this method, trimethylsilyl cyanide is used as a reaction solvent and a raw material, and a large excess of trimethylsilyl cyanide is present in the reaction system. Therefore, although the yield is improved, there is room for improvement in the following points.

  That is, when the trimethylsilyl cyanide is excessively present in the reaction system, a solid in which trimethylsilyl cyanide is solvated with the target cyanofluoroborate is formed, and it may be difficult to remove trimethylsilyl cyanide. In addition, there is room for improvement in that post-treatment such as removing excess trimethylsilylcyanide to make it harmless or recovering it becomes complicated. In addition, since trimethylsilylcyanide is expensive, there is room for improvement in terms of industrial production in that the cost of the obtained cyanofluoroborate is increased.

Japanese Patent No. 4718438 Special table 2014-529335 gazette

Journal of Fluorine Chemistry 2015, 177 46-54 Inorganic Chemistry 2015, 54, 3413-3421

  Accordingly, an object of the present invention is to provide a method capable of producing cyanofluoroborate at a low cost and in a high yield.

  The inventors of the present invention have made extensive studies to solve the above problems. First, using a cyanide which is an inexpensive raw material (for example, an alkali cyanide such as sodium cyanide), a method capable of producing cyanofluoroborate in a high yield was examined. As a result, when reacting tetrafluoroborate as the other raw material to be reacted with cyanide (alkali cyanide), trialkylsilyl halide is present in the reaction system, so that cyanofluoroboron can be obtained in high yield. The present inventors have found that an acid salt can be obtained and have completed the present invention.

That is, the present invention
Following formula (1)
(R ¹ ) ₃ SiX (1)
(Where
R ¹ is an alkyl group having 1 to 6 carbon atoms, which may be the same or different,
X is a halogen atom. )
In the presence of a trialkylsilyl halide represented by the following (hereinafter sometimes simply referred to as “trialkylsilyl halide”),
Following formula (2)
(M ¹ ) ⁺ [BF ₄ ] ⁻ (2)
(Where
(M ¹ ) ⁺ is a monovalent cation. )
A tetrafluoroborate salt (hereinafter sometimes referred to simply as “tetrafluoroborate”),
Following formula (3)
(M ² ) ⁺ CN ⁻ (3)
(Where
(M ² ) ⁺ is a monovalent cation. )
By reacting with a cyanide represented by the following (hereinafter sometimes simply referred to as “cyanide”),
Following formula (4)
(M ³ ) ⁺ [BF _a (CN) _4-a ] ⁻ (4)
(Where
(M ³ ) ⁺ is a cation that is softer in the HSAB rule among (M ¹ ) ⁺ in the formula (2) and (M ² ) ⁺ in the formula (3).
a is an integer of 1 to 3. )
Is a method for producing a cyanofluoroborate salt (hereinafter sometimes simply referred to as “cyanofluoroborate salt”).

  According to the present invention, cyanofluoroborate can be produced in high yield using an inexpensive raw material. Therefore, since the cost of cyanofluoroborate useful for electrolytes such as lithium ion batteries can be reduced, its industrial utility value is high.

  The present invention is a method for producing a cyanofluoroborate by reacting a tetrafluoroborate with a cyanide in the presence of a trialkylsilyl halide. In the following, description will be given in order.

(Trialkylsilyl halide)
The reaction of the present invention is represented by the following formula (1):
(R ¹ ) ₃ SiX (1)
In the presence of a trialkylsilyl halide represented by

In the formula, R ¹ is an alkyl group having 1 to 6 carbon atoms and may be the same or different. Among these, in view of easy availability and reaction yield, R ¹ is preferably an alkyl group having 1 to 4 carbon atoms.

  In the formula, X is a halogen atom. Of these, chlorine, bromine and iodine are preferable in consideration of reactivity.

  Specific trialkylsilyl halides are exemplified by trimethylsilyl chloride, trimethylsilyl bromide, trimethylsilyl iodide, triethylsilyl chloride, triethylsilyl bromide, triethylsilyl iodide, tri-n-propylsilyl chloride, tri-n-propylsilyl bromide, Examples include tri-n-propylsilyl iodide, tri-n-butylsilyl chloride, tri-n-butylsilyl bromide, tri-n-butylsilyl iodide, considering the availability and reaction yield. , Trimethylsilyl chloride, and triethylsilyl chloride are preferable. As these trialkylsilyl halides, commercially available products can be used.

  In the present invention, the amount of the trialkylsilyl halide used is not particularly limited, but in order to sufficiently proceed the reaction, 1.0 to 1.0 mol per 1 mole of cyanide described in detail below. It is preferable to set it as 3.0 mol, It is more preferable to set it as 1.2-3.0 mol, It is further more preferable to set it as 1.5-2.0 mol.

(Tetrafluoroborate)
In the present invention, the following formula (2)
(M ¹ ) ⁺ [BF ₄ ] ⁻ (2)
Is used as a raw material.

In the above formula, (M ¹ ) ⁺ is a monovalent cation. This monovalent cation may be either an organic cation or an inorganic cation. Among these, alkali metal ions are preferable because they are easily available and inexpensive, and cations selected from lithium ions (Li ⁺ ), sodium ions (Na ⁺ ), and potassium ions (K ⁺ ) are preferable.

  A commercially available tetrafluoroborate can be used.

(Cyanide)
In the present invention, as the other raw material, the following formula (3)
(M ² ) ⁺ CN ⁻ (3)
The cyanide represented by is used.

In the above formula, (M ² ) ⁺ is a monovalent cation. This monovalent cation may be either an organic cation or an inorganic cation. Among these, alkali metal ions are preferable because they are easily available and inexpensive, and cations selected from lithium ions (Li ⁺ ), sodium ions (Na ⁺ ), and potassium ions (K ⁺ ) are preferable.

  As the cyanide, a commercially available product can be used.

  In the present invention, the amount of the cyanide used is not particularly limited, and may be appropriately determined according to the desired composition of the cyanofluoroborate represented by the formula (4). Among these, in order to facilitate the post-treatment and increase the conversion to a cyano group, the amount is preferably 2.0 to 5.0 mol with respect to 1 mol of the tetrafluoroborate. Furthermore, in order to facilitate the post-treatment, increase the conversion to a cyano group, and improve the yield, the amount should be 2.5 to 5.0 mol with respect to 1 mol of the tetrafluoroborate. Is preferable, and it is more preferable to set it as 3.0-3.5 mol.

<Reaction process; reaction conditions>
In the present invention, in order to make the tetrafluoroborate and cyanide react in the presence of the trialkylsilyl halide, it is preferable to stir and mix the components so that the components are sufficiently in contact in the reaction system.

  In the present invention, the reaction does not proceed unless the three components are simultaneously present in the reaction system. That is, even if only the cyanide and tetrafluoroborate as raw materials are put into the reaction system, cyanofluoroborate is not generated. Even if only the trialkylsilyl halide and cyanide are put in the reaction system, trialkylsilyl cyanide as a cyanating agent is not produced. Therefore, although the reason why the reaction proceeds in the presence of the trialkylsilyl halide is not clear, the present inventors presume as follows.

  First, a trialkylsilyl halide and tetrafluoroborate, which is one of the raw materials, react to form a pentacoordinate silicon intermediate. Thereafter, this pentacoordinate silicon intermediate is considered to react with cyanide to produce a pentacoordinate silicon intermediate having a cyano group. The generated pentacoordinate silicon intermediate having a cyano group is a compound similar to trialkylsilyl cyanide. Then, it is estimated that the pentacoordinated silicon intermediate (hereinafter sometimes referred to simply as “analogous compound”) and tetrafluoroborate react with each other to finally obtain cyanofluoroborate. ing. Thus, the reaction of the present invention proceeds only after the presence of the three components, but is a reaction system that has not been conventionally known.

  For the reasons described above, it is preferable that the three components of trialkylsilyl halide, tetrafluoroborate, and cyanide are sufficiently mixed in the reaction system by stirring and mixing in the reaction solvent.

(Reaction solvent; aprotic polar solvent)
In the present invention, the reaction solvent to be used is not particularly limited as long as it does not affect each component, but an aprotic polar solvent is preferably used.

  The aprotic polar solvent is a solvent that does not contain a proton-donating group and has a polar group, and known solvents can be used. By carrying out the reaction in an aprotic polar solvent (by using an aprotic polar solvent as the reaction solvent), cyanofluoroborate can be produced in a higher yield. In addition, since the raw material can be diluted, the reaction can be carried out under mild conditions. And coloring of the cyanofluoroborate obtained can be suppressed, and an after-treatment can be made easy.

  In the present invention, the aprotic polar solvent preferably has a boiling point of 50 to 130 ° C. By using an aprotic polar solvent having a boiling point in the above-mentioned range, coloring of the resulting cyanofluoroborate is suppressed, the removal of the solvent is facilitated in post-treatment, and the temperature during the reaction is further increased. Therefore, the yield can be increased. Considering the ease of post-treatment and the yield, it is more preferable to use an aprotic polar solvent having a boiling point of 60 to 110 ° C., and an aprotic polar solvent having a boiling point of 70 to 90 ° C. Is more preferable. In addition, the aprotic polar solvent can also use multiple types of mixed solvent, and can also be used independently. In consideration of operability and the like, it is preferable to use a solvent alone.

  Specific examples of such aprotic polar solvents include tetrahydrofuran, dioxane, 1,2-dimethoxyethane, acetonitrile, propionitrile, butyronitrile, and ethyl acetate, and use a mixed solvent of these solvents. You can also

Of the aprotic polar solvents, those that do not dissolve the tetrafluoroborate are preferably used. “Undissolved” refers to a state in which even if 1 g of tetrafluoroborate and 25 ml of solvent are mixed at 23 ° C., the tetrafluoroborate solid can be visually confirmed. When a solvent in which the tetrafluoroborate ((M ¹ ) ⁺ [BF ₄ ] ⁻ ) dissolves is used, ((R ¹ ) ₃ Si ⁺ ) [BF ₄ ] ⁻ and (M ¹ ) ⁺ are introduced into the reaction system. A salt of X ⁻ is formed, and (M ² ) ⁺ CN ⁻ cannot participate in the reaction at all. Furthermore, since the generated ((R ¹ ) ₃ Si ⁺ ) [BF ₄ ] ⁻ is unstable, trialkylsilyl fluoride ((R ¹ ) ₃ SiF) and boron trifluoride BF ₃ are generated and collected. The rate may drop dramatically. Therefore, among the aprotic polar solvents exemplified above, it is preferable to use 1,2-dimethoxyethane, tetrahydrofuran, or dioxane. When 1,2-dimethoxyethane, tetrahydrofuran, or dioxane is used, tricyanofluoroborate (a = 1 in the above formula (4)) is likely to be formed, depending on the reaction conditions. Further, when acetonitrile is used, dicyanodifluoroborate (a = 2 in the above formula (4)) is likely to be formed, although this also depends on the reaction conditions.

(Other reaction conditions)
In the present invention, the order of mixing the components is not particularly limited. For example, there may be mentioned a method in which three components diluted with a reaction solvent are simultaneously introduced into the reaction system as necessary, followed by stirring and mixing. Further, if necessary, one component diluted with a reaction solvent can be sequentially introduced into the reaction system and mixed with stirring. Furthermore, if necessary, two components diluted with a reaction solvent can be introduced into the reaction system in advance and mixed with stirring, and one component diluted with a reaction solvent can be added to the mixture, if necessary. Above all, in order to proceed the reaction under milder conditions, the raw materials tetrafluoroborate and cyanide are mixed in the reaction solvent with stirring as necessary, and then the reaction solvent is added as necessary. It is preferable to employ a method of adding a trialkylsilyl halide diluted with 1.

  The temperature during the reaction (temperature during stirring and mixing) is not particularly limited, but is preferably 23 ° C. or higher and the reflux temperature of the aprotic polar solvent to be used. In order to maintain a high yield and suppress the coloring of the obtained cyanofluoroborate, the reaction temperature is more preferably 50 to 110 ° C, and further preferably 50 to 90 ° C. However, when the trialkylsilyl halide has a lower boiling point than the aprotic polar solvent, it is preferable to carry out the reaction at or below the reflux temperature of the trialkylsilyl halide in consideration of loss due to volatilization. In this case, if the cyanide is consumed (usually, a reaction time of 1 to 3 hours is sufficient), it is considered that a compound similar to trialkylsilyl cyanide (similar compound) is formed. Once this analogous compound is formed, the reaction temperature can thereafter be raised to the reflux temperature of the aprotic polar solvent. Therefore, for example, when trimethylsilyl chloride is used, the reaction is performed at a reaction temperature of 50 to 60 ° C. until cyanide is consumed, and then the reaction temperature is set to exceed 60 ° C. and 90 ° C. or less to complete the reaction. It is preferable.

  The atmosphere during the reaction is not particularly limited, but it is preferably carried out in a dry atmosphere, for example, a dry air atmosphere. Moreover, it is preferable to implement in inert gas atmosphere, such as nitrogen or argon. The pressure during the reaction is not particularly limited, and the reaction can be carried out under reduced pressure, normal pressure (atmospheric pressure), or increased pressure. However, since trialkylsilyl fluoride is by-produced as a gas in this reaction, the internal pressure may increase in a closed reaction, and in order to make the reaction proceed efficiently, the by-produced gas is out of the system. It is more advantageous to discharge it. Therefore, the reaction is preferably carried out under reduced pressure or atmospheric pressure, and is preferably carried out under atmospheric pressure in view of the volatilization of the reaction solvent.

The reaction time may be determined in consideration of the progress of the reaction, such as the consumption of the raw material compound and the amount of the desired cyanofluoroborate produced, but 0.5 to 10 hours according to the method of the present invention. If so, a cyanofluoroborate compound can be obtained in a sufficiently high yield. The progress of the reaction can be easily confirmed by analysis by ¹¹ B-NMR spectroscopy.

<Cyanofluoroborate>
According to the above method, the following formula (4)
(M ³ ) ⁺ [BF _a (CN) _4-a ] ⁻ (4)
Can be produced.

In the formula, (M ³ ) ⁺ is a cation that is softer in the HSAB rule among (M ¹ ) ⁺ in the formula (2) and (M ² ) ⁺ in the formula (3), and a is 1 It is an integer of ~ 3.

  Here, the HSAB rule is an abbreviation for Hard and Soft Acids and Bases. G. This is a rule proposed by Pearson. In other words, acid bases are classified into soft ones and hard ones, and qualitatively pointed out that "soft acids are easy to bond with soft bases and hard acids are easy to bond with hard bases". It is. The general characteristics of a hard acid base are that the central atom is small, the electronegativity is large, the polarizability is small, and the charge density is high, and the soft acid base has the opposite properties.

According to the HSAB rule, the cyanofluoroborate anion is a soft base and has a high affinity with a soft acid (cation). Therefore, (M ³ ) ⁺ becomes a softer cation in the HSAB rule among (M ¹ ) ⁺ and (M ² ) ⁺ . Specifically, an alkali metal ion will be described as an example. The order of softness of the alkali metal ions is K ⁺ > Na ⁺ > Li ⁺ . Therefore, the conversion from Li ⁺ to Na ⁺ and the conversion from Na ⁺ to K ⁺ can be easily performed, but the reverse conversion from K ⁺ to Li ⁺ and conversion from Na ⁺ to Li ⁺ is possible. Is difficult.

Therefore, when both (M ¹ ) ⁺ and (M ² ) ⁺ are alkali metal ions,
(M ³ ) ⁺ is
When at least one of (M ¹ ) ⁺ and (M ² ) ⁺ is K ⁺ , K ⁺
If both (M ¹ ) ⁺ and (M ² ) ⁺ are Na ⁺ , or one is Na ⁺ and the other is Li ⁺ , then Na ⁺
When both (M ¹ ) ⁺ and (M ² ) ⁺ are Li ⁺ , Li ⁺ is obtained.

As described above, when both (M ¹ ) ⁺ and (M ² ) ⁺ are alkali metal ions, (M ³ ) ⁺ is unlikely to be Li ⁺ , but is K ⁺ and Na ⁺ (M ³ ) ^+. Is Li ⁺ ((M ⁴ ) ⁺ ), the following method can be employed. For example, first, potassium cyanofluoroborate or sodium cyanofluoroborate and silver nitrate (I) Let it be silver cyanofluoroborate (I) which is a salt with a soft acid. Next, by reacting silver (I) cyanofluoroborate with lithium halide to produce a silver (I) halide precipitate, lithium cyanofluoroborate can be obtained.

In addition, the method for converting (M ³ ) ⁺ to Li ⁺ has been described above, but by performing various ion exchange reactions (metathesis reactions), an inorganic cation and an organic cation (( M ⁴ ) ⁺ ).

Further, in the purification step or the like, ion exchange can be performed in accordance with the HSAB rule by contacting with a compound containing various cations. For example, as described in detail below, by contacting a cyanofluoroborate (including (M ³ ) ⁺ ) with an alkali metal-containing compound (including (M ⁴ ) ⁺ ) in a purification step or the like, ((M ³ ) ⁺ ) can be a cyanofluoroborate salt replaced with ((M ⁴ ) ⁺ ).

<Purification process>
In this invention, it is preferable to take out the cyanofluoroborate obtained by employ | adopting the following method out of a reaction system. The obtained cyanofluoroborate is preferably purified by washing with water, an organic solvent, and a mixed solvent thereof, oxidation treatment, adsorption treatment, reprecipitation, recrystallization, extraction, and chromatography. These purification methods may be performed in combination. However, since the remaining similar compound may generate hydrogen cyanide by hydrolysis, it is preferably hydrolyzed and rendered harmless under appropriate conditions.

  In the method of taking out cyanofluoroborate, since the similar compound may remain in the reaction system, it is preferable to first render the similar compound harmless by oxidizing treatment. Examples of the oxidizing agent used for the oxidation treatment include peroxides such as hydrogen peroxide, peracetic acid and metachloroperbenzoic acid (mCPBA), manganese compounds such as potassium permanganate and manganese oxide, and chromium compounds such as potassium dichromate. , Halogen-containing compounds such as potassium chlorate, sodium bromate, potassium bromate, sodium perchlorate, sodium hypochlorite, chlorine dioxide, inorganic nitrogen compounds such as nitric acid and chloramine, acetic acid, osmium tetroxide, etc. . Among these, hydrogen peroxide which does not contain a metal element and whose decomposition product is only water is more preferable.

  In the oxidation treatment, the oxidizing agent may be introduced into the reaction system where the reaction has ended. Specific examples of the purification method including oxidation treatment include the following methods. First, the remaining cyanide is removed from the reaction mixture after the reaction is completed by filtration. Next, the reaction solvent is distilled off, and water and the oxidizing agent are introduced. Subsequently, carbonates, such as sodium carbonate and potassium carbonate, are gradually added while stirring the mixture containing crude cyanofluoroborate, water and an oxidizing agent. By performing such an operation, the oxidation treatment can be performed safely while keeping the liquidity alkaline. By this treatment, cyanide ions are oxidized to cyanate ions having low toxicity. Thereafter, the cyanofluoroborate in the aqueous solution is extracted with an organic solvent, the organic solvent is distilled off under reduced pressure, and the desired cyanofluoroborate can be isolated by vacuum drying.

As described above, depending on the kind of the oxidizing agent and carbonate used in the oxidation treatment in this purification step, cyanofluoroborate containing (M ³ ) ⁺ can be converted to cyanofluoroborate containing (M ⁴ ) ^+. Can be converted to acid salts. For example, potassium cyanofluoroborate ((M ⁴ ) ⁺ ) can be obtained by treating sodium cyanofluoroborate ((M ³ ) ⁺ ) with an oxidizing agent containing potassium, carbonate, or the like.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. First, a method for analyzing cyanofluoroborate will be described.

<NMR measurement>
¹¹ B-NMR and ¹⁹ F-NMR spectra were measured using a Fourier transform nuclear magnetic resonance apparatus JNM-ECA400II manufactured by JOEL RESONANCE. Acetone-D6 was used as the solvent. As a standard substance, sodium tetraphenylborate (δ-6.42 ppm) was used for measurement of ¹¹ B-NMR spectrum, and hexafluorobenzene (δ-162.90 ppm) was used for measurement of ¹⁹ F-NMR spectrum. The production state of cyanofluoroborate was confirmed by measuring ¹¹ B-NMR spectrum.

<GC analysis>
The analysis by GC was performed using Agilent 7890A manufactured by Agilent Technologies. DB-1 was used for the analytical column. The temperature increase pattern is 40 ° C. (5 minutes hold) → 300 ° C., and the temperature increase rate is 20 ° C./min. A flame ionization detector (FID) was used as a detector.

Example 1
Reaction Step In a 100 mL glass three-necked flask, 5.00 g (45.5 mmol; 1.0 eq.) Of sodium tetrafluoroborate (manufactured by Wako Pure Chemical Industries, Ltd .: tetrafluoroborate represented by the above formula (2)) was added. ), Sodium cyanide (manufactured by Wako Pure Chemical Industries, Ltd .; cyanide represented by the above formula (3)) 7.37 g (150.3 mmol; 3.3 eq.) Were charged, and a thermometer, a Dimroth, and a gas introduction tube were connected. Attach and assemble a reactor with a septum. As a reaction solvent, 50 mL of 1,2-dimethoxyethane was charged from a septum using a syringe and stirred with a stirrer piece under a nitrogen flow. Next, 24.74 g (227.7 mmol; 5.0 eq.) Of trimethylsilyl chloride (manufactured by Tokyo Chemical Industry; trialkylsilyl halide represented by the above formula (1)) was similarly charged from the septum using a syringe. At this time, 1.5 mol of trimethylsilyl chloride was used with respect to 1 mol of sodium cyanide. The reaction was started by placing the flask in an oil bath at 60 ° C. After reacting for 2 hours at a temperature in the reaction system (first reaction temperature) of 55 ° C., the reaction was carried out for 5 hours at a temperature in the reaction system (second reaction temperature) of 75 ° C. (reflux). The obtained reaction mixture was an orange solution, and the production ratio of the obtained cyanofluoroborate (cyanofluoroborate in the reaction mixture) was confirmed by ¹¹ B-NMR. As a result, the dicyanodifluoro product was 2.6. The mol% and the tricyanofluoro product were 97.4 mol%.

Purification Step After filtering sodium chloride and residual sodium cyanide from the reaction mixture, the solvent was distilled off under reduced pressure to obtain an orange solid. To this, 50 mL of ultrapure water was added and dissolved, and 5 mL of 30% by mass hydrogen peroxide was further added. Next, 5.8 g (54.7 mmol) of anhydrous sodium carbonate was slowly added while stirring. At this time, the color of the solution changed from orange to colorless, and some bubbles were observed. When the 50-fold diluted solution was analyzed using Quantofix test paper (peroxide, cyanide ion), only 100 mg / L of peroxide was detected, and no cyanide ion was detected. Thereafter, 1.7 g (10.8 mmol) of sodium thiosulfate was added to decompose the remaining peroxide. This liquid was similarly analyzed with a Quantofix test paper, and it was confirmed that the peroxide was completely decomposed. Further, this aqueous solution was extracted four times with 30 mL of ethyl acetate, and the resulting ethyl acetate solution was washed with a saturated aqueous sodium chloride solution. Ethyl acetate was distilled off with an evaporator to obtain a white solid. Vacuum drying (80 ° C., 20 hours) was performed to obtain 5.12 g of white sodium tricyanofluoroborate. The yield was 85.9%, and the purity by ¹¹ B-NMR was 98.3%. The analysis results by NMR are shown below.
¹¹ B-NMR (128.3 MHz): δ-17.7 ppm (d, J = 44 Hz).
¹⁹ F-NMR (376.2 MHz): δ-210.5 ppm (q, J = 44 Hz).

  The above reaction conditions and the results obtained are summarized in Table 1.

Comparative Example 1
In the reaction step of Example 1, trimethylsilyl chloride was not added, and the temperature in the reaction system was adjusted to 75 ° C. and stirred for 7 hours. The reaction mixture was a colorless solution and sodium cyanide remained undissolved. When the reaction mixture was analyzed by ¹¹ B-NMR, chemical species other than the starting tetrafluoro compound could not be confirmed, and the reaction did not proceed at all. The results are shown in Table 1.

Comparative Example 2
In the reaction step of Example 1, sodium tetrafluoroborate was not added, and the temperature in the reaction system was set to 55 ° C., followed by stirring and mixing for 7 hours. The reaction mixture was a colorless solution and sodium cyanide remained undissolved. When the reaction mixture was analyzed by GC, formation of trimethylsilyl cyanide as a cyanating agent could not be confirmed. Therefore, the reaction of the present invention is not a mechanism in which trimethylsilyl cyanide, which is a cyanating agent, is generated from sodium cyanide and trimethylsilyl chloride in the system, but the reaction proceeds only when three components are present. The results are shown in Table 1.

Examples 2-6
A cyanofluoroborate was obtained in the same manner as in Example 1 except that the raw materials, reaction solvents, and reaction temperatures (first and second reaction temperatures) shown in Table 1 were used. When the product was a mixture, the average molecular weight was used as a standard for yield, and the purity was calculated as the sum of both. The results are shown in Table 1.

Examples 7-14
Except having set it as the raw material shown in Table 2, the reaction solvent, and reaction temperature (1st, 2nd reaction temperature), operation similar to Example 1 was performed and the cyanofluoro borate was obtained. In the purification step, 7.5 g (54.3 mmol) of anhydrous potassium carbonate instead of anhydrous sodium carbonate, 2.0 g (10.5 mmol) of potassium thiosulfate instead of sodium thiosulfate, and saturated potassium chloride instead of saturated aqueous sodium chloride solution The same operation as in Example 1 was performed except that an aqueous solution was used. The results are shown in Table 2.

Claims (4)

Following formula (1)
(R ¹ ) ₃ SiX (1)
(Where
R ¹ is an alkyl group having 1 to 6 carbon atoms, which may be the same or different,
X is a halogen atom. )
In the presence of a trialkylsilyl halide represented by
Following formula (2)
(M ¹ ) ⁺ [BF ₄ ] ⁻ (2)
(Where
(M ¹ ) ⁺ is a monovalent cation. )
A tetrafluoroborate salt represented by
Following formula (3)
(M ² ) ⁺ CN ⁻ (3)
(Where
(M ² ) ⁺ is a monovalent cation. )
By reacting with a cyanide represented by
Following formula (4)
(M ³ ) ⁺ [BF _a (CN) _4-a ] ⁻ (4)
(Where
(M ³ ) ⁺ is a cation that is softer in the HSAB rule among (M ¹ ) ⁺ in the formula (2) and (M ² ) ⁺ in the formula (3).
a is an integer of 1 to 3. )
A method for producing a cyanofluoroborate represented by the formula:   The cyanide represented by the formula (3) is used in an amount of 2.0 to 5.0 moles per 1 mole of the tetrafluoroborate represented by the formula (2). the method of.   The trialkylsilyl halide represented by the formula (1) is used in an amount of 1.0 to 3.0 moles per 1 mole of the cyanide represented by the formula (3). The method described. The method according to claim 1, wherein an aprotic polar solvent is used as the reaction solvent.