DE102014008131A1 - Process for the preparation of salts with monoyidobiocyanoborate anions - Google Patents

Abstract

The invention relates to a process for the preparation of alkali metal salts with monohydridotricyanoborate anions of alkali metal tetrahydridoborate, alkali metal monocyanotrihydridoborate or alkali metal dihydridodicyanoborate.

Description

The invention relates to a process for the preparation of alkali metal salts with monohydridotricyanoborate anions of alkali metal tetrahydridoborate, alkali metal monocyanotrihydridoborate or alkali metal dihydridodicyanoborate.

Alkali metal salts with monohydridotricyanoborate anions are disclosed in the Offenlegungsschrift WO 2012/163489 are known and serve, for example, as starting materials for the synthesis of monohydridotricyanoborate salts with preferably organic cations. Such ionic liquids with monohydridotricyanoborate anions are suitable, for example, as electrolyte components for electrochemical cells, in particular for dye-sensitized solar cells. In WO 2012/163489 The synthesis of these alkali metal salts is also described, for example, by the processes of claims 4 to 6. In these processes, starting materials used are either alkali metal tetracyanoborates or alkali metal tetrahydridoborates. For example, claim 5 describes the reaction of an alkali metal tetrahydridoborate with {4KSCN + K ₂ [Zn (SCN) ₄ ]}.

In Gyori et al., Journal of Organometallic Chemistry, 255, 1983, 17-28 For example, the isomerization of sodium triisocyanohydridoborate (adduct with 0.5 moles of dioxane) to sodium monohydridotricyanoborate in boiling n-dibutyl ether is described.

Alkali metal salts with Dihydridodicyanoborat anions are disclosed in the disclosures WO 2012/163490 and WO 2012/163488 are known and serve as starting materials for the synthesis of Dihydridodicyanoborat salts with preferably organic cations, which are suitable for example for use as the electrolyte component in electrochemical cells, in particular dye solar cells. In WO 2012/163488 For example, there are described processes for the preparation of the alkali metal dihydridodicyanoborates in which either an alkali metal tetrahydridoborate or an alkali metal trihydridocyanoborate are reacted as starting materials with a trialkylsilyl cyanide, preferably at temperatures between 10.degree. C. and 200.degree. Preferably, the trialkylsilyl cyanide is added in a threefold amount, based on the borate.

However, there remains a need for economical alternative synthetic methods to produce alkali metal monohydridotricyanoborates.

The object of the present invention is therefore to develop alternative production processes for the synthesis of alkali metal monohydridotricyanoborates starting from readily available and comparatively inexpensive starting materials. Preferably, the alternative process has short reaction times with good yield and good product purity.

Surprisingly, it has been found that by selecting the appropriate reaction conditions, alkali metal monohydridotricyanoborates can be prepared from an alkali metal tetrahydridoborate, an alkali metal monocyanotrihydridoborate or an alkali metal dicyanodihydridoborate by reaction with a corresponding trialkylsilyl cyanide. Preferably, the alkali metal monohydridotricyanoborate is prepared by reacting an alkali metal tetrahydridoborate with trimethylsilyl cyanide.

The subject of the invention is therefore a process for the preparation of compounds of the formula I. [Me] ⁺ [BH (CN) ₃ ] ^- I, in which
Me means an alkali metal,
by reacting a compound of formula II [Me ^{1] +} [BH _n (CN) _4-n] ^- II, wherein Me ^{1 represents} an alkali metal which may be the same or different than Me, and
n is 2, 3 or 4,
with a trialkylsilyl cyanide at a reaction temperature of 200 ° C to 300 ° C, under a pressure of 5 to 25 bar and in the presence of a trialkylsilyl chloride, trialkylsilyl bromide and / or trialkylsilyl iodide, wherein the alkyl groups of the trialkylsilylcyanide and / or the trialkylsilyl halide are each independently linear or branched alkyl group having 1 to 10 carbon atoms,
wherein the conditions of the reaction are chosen such that both the water content and the oxygen content amount to a maximum of 1000 ppm, and
subsequent metal cation exchange, in case Me ¹ does not correspond to Me.

Alkali metals are the metals lithium, sodium, potassium, cesium or rubidium.

In compounds of the formula I, Me is preferably sodium or potassium, particularly preferably potassium.

Accordingly, the process according to the invention is preferably suitable for the synthesis of sodium monohydridotricyanoborate or potassium monohydridotricyanoborate. The process according to the invention is particularly preferably suitable for the synthesis of potassium monohydridotricyanoborate.

The compounds of formula II are commercially available or accessible by known synthetic methods.

In the compounds of formula II, Me ¹ may be an alkali metal selected from the group lithium, sodium, potassium, cesium or rubidium, which is chosen independently of the alkali metal of the end product of formula I. Me ¹ in formula II may be the same or different than Me in formula I.

In compounds of formula II, Me ^{1 is} preferably sodium or potassium. In compounds of the formula II, Me ^{1 is} particularly preferably sodium.

A linear or branched alkyl group having 1 to 10 C atoms is, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, ethylhexyl, n-nonyl or n-decyl.

Trialkylsilyl cyanides are commercially available or are accessible by known synthetic methods. The alkyl groups of the trialkylsilyl cyanide may be the same or different. The alkyl groups of the trialkylsilyl cyanide have 1 to 10 C atoms, preferably 1 to 8 C atoms, particularly preferably 1 to 4 C atoms. The alkyl groups of the trialkylsilyl cyanide are preferably the same if they are alkyl groups having 1 to 4 C atoms. An alkyl group of the trialkylsilyl cyanide is preferably different when it is an alkyl group of 5 to 10 C atoms or 5 to 8 C atoms. Suitable examples of trialkylsilyl cyanides are trimethylsilyl cyanide, triethylsilyl cyanide, triisopropylsilyl cyanide, tripropylsilyl cyanide, octyldimethylsilyl cyanide, butyldimethylsilyl cyanide, t-butyldimethylsilyl cyanide or tributylsilyl cyanide.

Particularly preferred trimethylsilyl cyanide is used, which is commercially available or can be prepared in situ.

In the process of the present invention, the trialkylsilyl cyanide as described or preferred as described or selected from the group consisting of trimethylsilylcyanide, triethylsilylcyanide, triisopropylsilylcyanide, tripropylsilylcyanide, octyldimethylsilylcyanide, butyldimethylsilylcyanide, t-butyldimethylsilylcyanide or tributylsilylcyanide is not prepared in situ.

The trialkylchlorosilane, trialkylbromosilane or trialkyliodosilane is commercially available or can be prepared by standard methods. Trialkylbromosilane or trialkyliodosilane can be prepared in situ from a trialkylchlorosilane and an alkali metal bromide or alkali metal iodide.

Suitable trialkylsilyl chlorides for the process according to the invention (or synonymously trialkylchlorosilanes), trialkylsilyl bromides (synonymous with trialkylbromosilanes) and / or trialkylsilyliodides (synonymous with trialkyliodosilanes) have alkyl groups which are each independently linear or branched and have 1 to 10 carbon atoms.

The alkyl groups of the trialkylsilyl halide may be the same or different. The alkyl groups of the trialkylsilyl halide preferably have 1 to 8 C atoms, particularly preferably 1 to 4 C atoms. The alkyl groups of the trialkylsilyl halide are preferably the same if they are alkyl groups having 1 to 4 carbon atoms. An alkyl group of the trialkylsilyl halide is preferably different when it is an alkyl group of 5 to 10 C atoms or 5 to 8 C atoms.

Preferably, the trialkylsilyl halide is a trialkylsilyl chloride.

Suitable trialkylsilyl chlorides are trimethylsilyl chloride (or synonymously trimethylchlorosilane), triethylsilyl chloride, triisopropylsilyl chloride, tripropylsilyl chloride, octyldimethylsilyl chloride, butyldimethylsilyl chloride, t-butyldimethylsilyl chloride or tributylsilyl chloride. Particular preference is given to using trimethylsilyl chloride. Very particular preference is given to using trimethylsilyl chloride alone.

Suitable trialkylbromosilanes are trimethylbromosilane (or synonymously trimethylsilylbromide), triethylsilylbromide, triisopropylsilylbromide, tripropylsilylbromide, octyldimethylsilylbromide, butyldimethylsilylbromide, t-butyldimethylsilylbromide or tributylsilylbromide. Particularly preferred trimethylsilyl bromide is used in admixture with trimethylsilyl chloride.

Suitable trialkyliodosilanes are trimethyliodosilane (or synonymously trimethylsilyl iodide), triethylsilyl iodide, triisopropylsilyl iodide, tripropylsilyl iodide, octyldimethylsilyl iodide, butyldimethylsilyl iodide, t-butyldimethylsilyl iodide or tributylsilyl iodide. Particularly preferred trimethylsilyliodi is used in admixture with trimethylsilyl chloride.

Particular preference is given to using the trialkylsilyl halide or a mixture of trialkylsilyl halides, as described above or described as being preferred, in a total amount of from 1 to 20 mol%, based on the amount of the trialkylsilyl cyanide used. Particular preference is given to using the trialkylsilyl halide or a mixture of trialkylsilyl halides in a total amount of from 3 to 12 mol%, based on the amount of trialkylsilyl cyanide used. Very particular preference is given to using the trialkylsilyl halide or a mixture of trialkylsilyl halides in a total amount of from 7 to 11 mol%, based on the amount of trialkylsilyl cyanide used.

It is preferable to mix the starting materials in an inert gas atmosphere whose oxygen content is at most 1000 ppm. It is particularly preferred if the oxygen content is less than 500 ppm, very particularly preferably not more than 100 ppm. The water content of the reagents and the inert gas atmosphere is at most 1000 ppm. It is particularly preferred if the water content of the reagents and of the atmosphere is less than 500 ppm, very particularly preferably not more than 100 ppm. The conditions with regard to the water content and the oxygen content do not apply to the work-up after successful reaction of the compound of the formula II with the trialkylsilyl cyanide.

Another object of the invention is therefore a method as described above or described as preferred, wherein the reaction of the compound of formula II with trialkylsilyl cyanide takes place in the presence of 1 to 20 mol% trialkylsilyl halide, based on the amount of Trialklylsilylcyanids used.

In a preferred embodiment of the process, the reaction according to the invention takes place at a reaction temperature of from 200 to 275.degree.

In a preferred embodiment of the process, the reaction according to the invention takes place at a pressure between 5 and 25 bar.

In a particularly preferred embodiment of the process, the reaction according to the invention takes place at a reaction temperature of 200 ° C. to 275 ° C. and a pressure of between 5 and 25 bar.

In a particularly preferred embodiment of the process, the reaction according to the invention takes place with a compound of the formula II in which n is 4, ie. H. with an alkali metal tetrahydridoborate. In this embodiment of the invention, it is preferred that the trialkylsilyl cyanide be added as described above in a 6 to 15 fold amount based on the amount of the alkali metal tetrahydridoborate.

Another object of the invention is therefore the method as described above or described as preferred, characterized in that the reaction of the compound of formula II wherein n is 4, is carried out with a 6-fold to 15-fold amount of trialkylsilyl cyanide, based on the amount the compound of formula II.

In an alternative embodiment of the invention, it is particularly preferred if a compound of the formula II is used in which n is 2 or 3 or in which n is very particularly preferably 2. In this embodiment of the invention, it is preferred that the trialkylsilyl cyanide be added as described above at 4 to 13 times the amount of the compound of formula II.

Another object of the invention is therefore the method as described above or described as preferred, characterized in that the reaction of the compound of formula II, wherein n is 2 or 3, is carried out with a 4-fold to 13-fold amount of trialkylsilyl cyanide, based on the amount of the compound of formula II.

Regardless of which embodiment of the process according to the invention is selected as described above, it is preferred if the reaction of the reactants is followed by a purification step in order to separate the end product of the formula I from by-products or reaction products as described above.

Suitable purification steps include the separation of volatile components by distillation or condensation, extraction with an organic solvent, or a combination of these methods. Any known separation method can be used or combined for this purpose. Each separation method may be followed by another purification step, such as recrystallization.

Another object of the invention is therefore the inventive method, as described above, characterized in that the reaction is followed by a purification step.

If a metal cation exchange after the reaction of the compound of formula II with the specified reactants and the specified reaction conditions, as described above and below, be necessary, because the corresponding alkali metal cation Me for the target product of formula I is not yet contained in the reaction mixture, it is in one embodiment of the invention, when the metal cation exchange takes place during the purification step. Preferably, the metal cation exchange is an alkali metal cation exchange.

A preferred method for the metal cation exchange or preferably the alkali metal cation exchange, for example, the reaction of the resulting reaction mixture with a corresponding carbonate (Me) ₂ CO ₃ and / or a corresponding hydrogen carbonate MeHCO ₃ , wherein Me corresponds to the alkali metal Me of the desired end product of the formula I. Preferably, the reaction mixture obtained from the reaction is cooled to room temperature and all volatile components are removed in vacuo. The solid obtained is then taken up in an organic solvent and water and treated with the corresponding carbonate (Me) ₂ CO ₃ and / or the corresponding bicarbonate MeHCO ₃ , wherein Me corresponds to the alkali metal Me of the desired end product of the formula I. Subsequently, the phases are separated and the organic solvent is separated off. The product obtained can be dried as usual or further purified. Preferably, this purification is followed by recrystallization.

Another object of the invention is therefore the inventive method, as described above, wherein the metal cation exchange, preferably the alkali metal cation exchange, takes place during the purification step.

Another object of the invention is therefore the inventive method, as described above, wherein the metal cation exchange by reaction with the compound (Me ₂ ) CO ₃ and / or the compound MeHCO ₃ , wherein Me corresponds to the alkali metal Me of the desired end product of the formula I. ,

In one embodiment of the process according to the invention, as described above, the reaction of the compound of the formula II as described above or described as preferred takes place without an organic solvent. The reaction mixture in this embodiment of the process according to the invention form the compound of the formula II, the trialkylsilyl cyanide and the trialkylsilyl halide.

Another object of the invention is therefore the inventive method, as described above, wherein the reaction of the compound of formula II, as described above or described below as preferred, takes place without an organic solvent.

However, it is also possible to carry out the reaction of the process according to the invention, as described above, in the presence of an organic solvent.

Suitable solvents are 1,2-dimethoxyethane, diglyme, acetonitrile, propionitrile or benzonitrile.

The method of the invention may now be followed by a classical metathesis reaction, wherein a compound of formula III [Kt] ^{z +} z [BH (CN) ₃ ] ^- III arises in the
[Kt] ^{z + is} an inorganic or organic cation and z corresponds to the charge of the cation.

Another object of the invention is therefore a process for the preparation of compounds of formula III [Kt] ^{z +} z [BH (CN) ₃ ] ^- III, in which
[Kt] ^{z + is} an inorganic or organic cation and z is the charge of the cation,
by anion exchange, wherein a salt containing the cation [Kt] ^{z +} with a compound of formula I. [Me] ⁺ [BH (CN) ₃ ] ^- I, prepared by the process according to the invention, as described above, wherein Me is an alkali metal.

Preferably, [Kt] ^{z + has} the meaning of an organic cation or an inorganic cation, wherein the cation [Kt] ^{z +} does not correspond to the cation used Me ^{+ of} the compound of formula I and the anion A of the salt containing [Kt] ^{z +}
F ^- , Cl ^- , Br ^- , I ^- , HO ^- , [HF ₂ ] ^- , [CN] ^- , [SCN] ^- , [R ₁ COO] ^- , [R ₁ OC (O) O] ^- , [ R ₁ SO ₃ ] ^- , [R ₂ COO] ^- , [R ₂ SO ₃ ] ^- , [R ₁ OSO ₃ ] ^- , [PF ₆ ] ^- , [BF ₄ ] ^- , [HSO ₄ ] ^- , [NO ₃ ] ^- , [(R ₂ ) ₂ P (O) O] ^- , [R ₂ P (O) O ₂ ] ^2- , [(R ₁ O) ₂ P (O) O] ^- , [(R ₁ O ) P (O) O ₂ ] ^2- , [(R ₁ O) R ₁ P (O) O] ^- , tosylate, malonate, which may be substituted by straight-chain or branched alkyl groups having 1 to 4 carbon atoms, [HOCO ₂ ] ^- or [CO ₃ ] ^2- means
wherein R ₁ each independently represents a straight-chain or branched alkyl group having 1 to 12 C atoms, and
R ₂ each independently represents a straight-chain or branched perfluorinated alkyl group having 1 to 12 C atoms and wherein in the formula of the salt [KtA] the electroneutrality is taken into account.

A perfluorinated linear or branched alkyl group having 1 to 4 C atoms is, for example, trifluoromethyl, pentafluoroethyl, n-heptafluoropropyl, isoheptafluoropropyl, n-nonafluorobutyl, sec-nonafluorobutyl or tert-nonafluorobutyl. By way of example, R ₂ defines a linear or branched perfluorinated alkyl group having 1 to 12 C atoms, comprising the abovementioned perfluoroalkyl groups and, for example, perfluorinated n-hexyl, perfluorinated n-heptyl, perfluorinated n-octyl, perfluorinated ethylhexyl, perfluorinated n-nonyl, perfluorinated n-decyl, perfluorinated n-undecyl or perfluorinated n-dodecyl.

R ₂ is particularly preferably trifluoromethyl, pentafluoroethyl or nonafluorobutyl, very particularly preferably trifluoromethyl or pentafluoroethyl.

R ₁ is particularly preferably methyl, ethyl, n-butyl, n-hexyl or n-octyl, very particularly preferably methyl or ethyl.

Substituted malonates are, for example, the compounds methyl or ethyl malonate.

Preferably, the anion A of the salt comprising [Kt] ^{z +} OH ^-, Cl ^-, Br ^-, I ^-, [CH ₃ SO _3] ^- [CH ₃ OSO _3] ^-, [CF ₃ COO] ^-, [CF ₃ SO _3] ^-, [(C ₂ F _{5) 2} P (O) O] ^- or [CO _3] ^2-, more preferably OH ^-, Cl ^-, Br ^-, [CH ₃ OSO _3] ^-, [CF ₃ SO ₃ ] ^- , [CH ₃ SO ₃ ] ^- or [(C ₂ F ₅ ) ₂ P (O) O] ^- .

The organic cation for [Kt] ^{z +} is selected, for example, from iodonium cations, ammonium cations, sulfonium cations, oxonium cations, phosphonium cations, uronium cations, thiouronium cations, guanidinium cations, tritylium cations or heterocyclic cations.

Preferred inorganic cations are metal cations of the metals of group 2 to 12 or also NO ⁺ or H ₃ O ⁺ .

Preferred inorganic cations are Ag ⁺ , Mg ²⁺ , Cu ⁺ , Cu ²⁺ , Zn ²⁺ , Ca ²⁺ , Y ³⁺ , Yb ³⁺ , La ³⁺ , Sc ³⁺ , Ce ³⁺ , Nd ³⁺ , Tb ³⁺ , Sm ³⁺ or complex (ligand-containing) metal cations, the rare earth, transition or noble metals such as rhodium, ruthenium, iridium, palladium, platinum, osmium, cobalt, nickel, iron, chromium, molybdenum, tungsten, vanadium, Titanium, zirconium, hafnium, thorium, uranium, gold included.

The salting reaction of the salt of the formula I with a salt containing [Kt] ^{z +} , as described above, is advantageously carried out in water, temperatures of 0 ° -100 ° C., preferably 15 ° -60 ° C. being suitable. Particularly preferred is reacted at room temperature (25 ° C).

However, the aforementioned salting reaction may alternatively take place in organic solvents at temperatures between -30 ° and 100 ° C. Suitable solvents are acetonitrile, propionitrile, dioxane, dichloromethane, dimethoxyethane, dimethyl sulfoxide, tetrahydrofuran, dimethylformamide, acetone or alcohol, for example methanol, ethanol or isopropanol, diethyl ether or mixtures of the solvents mentioned.

The obtained substances are characterized by NMR spectra. The NMR spectra are measured on solutions in deuterated acetone-D ₆ or in CD ₃ CN on a Bruker Avance 500 spectrometer with deuterium lock. The measurement frequencies of the different cores are: ¹ H: 500.1 MHz, ¹¹ B: 160.5 MHz and ¹³ C: 125.8 MHz. Referencing is done with external reference: TMS for ¹ H and ¹³ C spectra and BF ₃ · Et ₂ O - for ¹¹ B spectra. Example 1: Synthesis of potassium monohydridotricyanoborate; K [BH (CN) ₃ ]

Na [BH ₄ ] (3.0 g, 79.3 mmol) is placed in an autoclave (100 mL working volume, void space: 140 mL, heating hood 10S) together with trimethylsilyl cyanide (120 mL, 0.90 mol) and trimethylchlorosilane, (CH ₃ ) ₃ SiCl (10.0 mL, 79.2 mmol) for 10 hours at 250 ° C (temperature is equivalent to the specifications of the temperature control of the heating hoods) heated. The cooled reaction mixture is concentrated to dryness under reduced pressure and the solid obtained in a fine vacuum (1 × 10 ^-3 mbar) dried. The black solid is taken up in tetrahydrofuran (100 mL) and water (30 mL) and treated with K ₂ CO ₃ (20 g) and KHCO ₃ (20 g). The organic phase is separated, the aqueous phase extracted once more with THF (50 mL) and the combined organic phases are dried with K ₂ CO ₃ (20 g). The suspension is filtered, the solvent is removed with a rotary evaporator and the black crude product is dried in a fine vacuum (1 × 10 ^-3 mbar). The yield of K [BH (CN) ₃ ] is 7.7 g (59.9 mmol), corresponding to 75% based on the borate used. A final purification of the crude product is carried out by crystallization from hot isopropanol. The yield of colorless K [BH (CN) ₃ ] is 4.5 g (34.9 mmol), corresponding to 44% based on the borate used.

The product is characterized by NMR spectra in acetone-D ₆ solution:
¹¹ B {1H} NMR, δ, ppm: -40.04, s.
¹¹ B-NMR, δ, ppm: -40.04 d, ¹ J _{11B, 1H} = 96.8 Hz.
¹ H NMR, δ, ppm: 1.79 q, ¹ J _{11B, 1H} = 96.8 Hz.
¹ H { ¹¹ B} NMR, δ, ppm: 1.79, s. Example 2: Synthesis of sodium monohydridotricyanoborate; Na [BH (CN) ₃ ]

Na [BH ₄ ] (5.0 g, 132.2 mmol) is combined in an autoclave (200 mL working volume, empty space: 300 mL, heating hood 20S) together with trimethylsilyl cyanide (180 mL, 1.35 mol) and trimethylchlorosilane, (CH ₃ ) ₃ SiCl (15.0 mL, 118.7 mmol) for 3 hours at 200 ° C and 10 hours at 230 ° C (temperature corresponds to the specifications of the temperature control of the heating hoods) heated. The maximum pressure in the autoclave is 20 bar. The cooled reaction mixture is concentrated to dryness under reduced pressure and the resulting solid dried in a fine vacuum (1 × 10 ^-3 mbar), taken up in acetone (100 mL) and undissolved is filtered off (glass frit, Pore 4). The acetone solution is treated with toluene (150 mL). The precipitated crude product, Na [BH (CN) ₃ ], is filtered off (glass frit, Pore 4) and dried under a fine vacuum (1 × 10 ^-3 mbar). The yield of black crude product, Na [BH (CN) ₃ ], is 8.3 g (73.5 mmol), corresponding to 56% based on the used borate. A final purification of the crude product is carried out by crystallization from acetone by addition of dichloromethane. The ¹⁹ F and ¹¹ B NMR spectra are identical to those of Example 1. Example 3: Synthesis of sodium monohydridotricyanoborate from sodium monocyanotrihydridoborate; Na [BH (CN) ₃ ]

Na [BH ₃ CN] (8.30 g, 132.2 mmol) is dissolved in trimethylsilyl cyanide (220.0 mL) in a high pressure reactor [BR-300 (350 mL volume, with anchor stirrer, temperature controller and data logger for heating and agitator) of Berghof, Eningen] , 1.65 mol). Trimethylchlorosilane (10.0 mL, 97.16 mmol) is added to the suspension, and the reaction mixture is heated to 230 ° C. (internal temperature) with stirring (1000 revolutions / minute) for 8 hours. The maximum pressure is 21 bar. Subsequently, all volatiles are distilled off in vacuo at a pressure of about 5 × 10 ^-1 mbar and an oil bath temperature of 100 ° C. The resulting residue is dissolved in THF (15 mL) and dark brown solid is precipitated by addition of CH ₂ Cl ₂ (150 mL). This is taken up in H ₂ O (10 mL) and the aqueous phase is then treated with K ₂ CO ₃ (15 g). The aqueous phase is extracted with THF (50 mL), followed by further K ₂ CO ₃ (15 g) and extracted again with THF (2 × 50 mL). The combined organic phases are dried with K ₂ CO ₃ (15 g) and then concentrated to a residual volume of about 5 mL. Addition of CH ₂ Cl ₂ (50 mL) precipitates slightly yellow K [BH (CN) ₃ ]. This is dried in a fine vacuum to a final pressure of 3 × 10 ^-3 mbar.

The yield of K [BH (CN) ₃ ] is 5.8 g (45.01 mmol), corresponding to 34 based on the borate used.

NMR spectroscopy (200 MHz spectrometer, Bruker Avance 200)

• Referencing: acetone-d ₆ : residual proton signal: 2.05 ppm
• ¹¹ B ⁽¹ H) -NMR (64.14 MHz, acetone-d6) δ -40.06 (s).
• ¹¹ B NMR (64.14 MHz, acetone-d6) δ -40.06 (d, ¹ J ( ¹¹ B, ¹ H) = 96.7 Hz).
• ¹ H-NMR (199.93 MHz, acetone-d ₆ ), δ, ppm: 1.79 (q, ¹ J ( ¹¹ B ¹ H) = 96.8 Hz).
• ¹ H- ( ¹¹ B) NMR (199.93 MHz, acetone-d ₆ ), δ, ppm: 1.80 (s).

The NMR data are consistent with those in WO 2012/163489 and previous examples for K [BH (CN) ₃ ] in CD ₃ CN and acetone-d6, respectively. Example 4: Synthesis of potassium monohydridotricyanoborate from sodium dihydridodicyanoborate; K [BH (CN) ₃ ]

Na [BH ₂ (CN) ₂ ] (44.61 g, 132.2 mmol) is dissolved in trimethylsilyl cyanide in a high pressure reactor [BR-300 (350 mL volume, with anchor stirrer, temperature controller and data logger for heating and stirrer) from Berghof, Eningen] (220.0 mL, 1.65 mol). Trimethylchlorosilane (10.0 mL, 79.16 mmol) is added to the suspension and the reaction mixture is heated to 230 ° C. (internal temperature) with stirring (1000 revolutions / minute) for 6 hours. The maximum pressure is 19-21 bar. Subsequently, all volatiles are distilled off in vacuo at a pressure of about 5 × 10 ^-1 mbar and an oil bath temperature of 100 ° C. The residue obtained is dissolved in THF (50 ml) and by the addition of CH ₂ Cl ₂ (180 ml) a light brown solid is precipitated. This is taken up in H ₂ O (50 mL) and the aqueous phase is then treated with K ₂ CO ₃ (15 g). The aqueous phase is extracted with THF (2 × 70 mL) and then added with additional K ₂ CO ₃ (15 g) and extracted again with THF (2 × 50 mL). The combined organic phases become dried with K ₂ CO ₃ (80 g) and then concentrated to a residual volume of about 20 mL. By adding CH ₂ Cl ₂ (150 mL), colorless K [BH (CN) ₃ ] is precipitated. This is dried in a fine vacuum to a final pressure of 3 × 10 ^-3 mbar. The yield of K [BH (CN) ₃ ] is 4.2 g (32.56 mmol), corresponding to 25% based on the borate used.

NMR spectroscopy (200 MHz spectrometer, Bruker Avance 200)

• Referencing: acetone-d ₆ : residual proton signal: 2.05 ppm
• ¹¹ B { ¹ H} NMR (64.14 MHz, acetone-d6) δ -39.9 (s).
• ¹¹ B NMR (64.14 MHz, acetone-d6) δ -39.9 (d, ¹ J ( ¹¹ B, ¹ H) = 96.9 Hz).
• ¹ H-NMR (199.93 MHz, acetone-d ₆ ), δ, ppm: 1.80 (q, ¹ J ( ¹¹ B, ¹ H) = 96.8 Hz).
• ¹ H- { ¹¹ B} NMR (199.93 MHz, acetone-d ₆ ), δ, ppm: 1.80 (s).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2012/163489 [0002, 0002, 0066]
• WO 2012/163490 [0004]
• WO 2012/163488 [0004, 0004]

Cited non-patent literature

• B. Gyori et al., Journal of Organometallic Chemistry, 255, 1983, 17-28 [0003]

Claims (9)

Process for the preparation of compounds of the formula I [Me] ⁺ [BH (CN) ₃ ] ^- I, wherein Me is an alkali metal, by reacting a compound of formula II [Me ^{1] +} [BH _n (CN) _4-n] ^- II, wherein Me ^{1 represents} an alkali metal, which may be the same or different than Me and n is 2, 3 or 4, with a trialkylsilyl cyanide at a reaction temperature of 200 ° C to 300 ° C, under a pressure of 5 to 25 bar and in the presence a trialkylsilyl chloride, trialkylsilyl bromide and / or trialkylsilyl iodide, wherein the alkyl groups of the trialkylsilylcyanide and / or the trialkylsilyl halide each independently represent a linear or branched alkyl group having 1 to 10 carbon atoms, the conditions of the reaction being such that both the water content and the Also, the oxygen content may be at most 1000 ppm, and subsequent metal cation exchange, in the event that Me ¹ does not equal Me. A method according to claim 1, characterized in that the reaction is followed by a purification step. A method according to claim 1 or 2, characterized in that the metal cation exchange takes place during the purification step. Method according to one or more of claims 1 to 3, characterized in that the metal cation exchange is carried out by reaction with the compound (Me) ₂ CO ₃ and / or the compound MeHCO ₃ , wherein Me corresponds to the alkali metal Me of the compound of formula I. Method according to one or more of claims 1 to 4, characterized in that the reaction of the compound of formula II with trialkylsilyl cyanide takes place in the presence of 1 to 20 mol% trialkylsilyl halide, based on the amount of Trialklylsilylcyanids used. Method according to one or more of claims 1 to 5, characterized in that the reaction of the compound of formula II, wherein n is 4, takes place with a 6-fold to 15-fold amount of trialkylsilyl cyanide, based on the amount of the compound of formula II. Method according to one or more of claims 1 to 5, characterized in that the reaction of the compound of formula II, wherein n is 2 or 3, takes place with a 4-fold to 13-fold amount of trialkylsilyl cyanide, based on the amount of the compound of formula II. Method according to one or more of claims 1 to 7, characterized in that the reaction of the compound of formula II with trialkylsilyl cyanide takes place without an organic solvent. Process for the preparation of compounds of formula III [Kt] ^{z +} z [BH (CN) ₃ ] ^- III, wherein [Kt] ^{z + is} an inorganic or organic cation, z is the charge of the cation and n is 1 or 2, by anion exchange, wherein a salt containing the cation [Kt] ^{z +} with a compound of formula I. [Me] ⁺ [BH (CN) ₃ ] ^- I, prepared according to one or more of claims 1 to 8, wherein Me is an alkali metal and n has the same meaning as in the compound of formula III.