WO2021044016A1

WO2021044016A1 - Method for purifying 2-(fluoroalkyl or fluoroalkoxy)-4,5-dicyanoimidazoles

Info

Publication number: WO2021044016A1
Application number: PCT/EP2020/074831
Authority: WO
Inventors: Rémy Teissier; Grégory Schmidt
Original assignee: Arkema France
Priority date: 2019-09-06
Filing date: 2020-09-04
Publication date: 2021-03-11
Also published as: EP4025563A1; FR3100539B1; CN114341115A; FR3100539A1

Abstract

The present invention concerns a method for purifying a compound of following formula (III), in which Rf is a fluorinated alkyl group or fluorinated alkoxyl group comprising 1 to 5 carbon atoms, said method comprising the following steps: a) a step of heating a composition comprising the compound of formula (III) in an organic solvent S3, to a temperature T₁ until the compound of formula (III) has dissolved; b) a step of cooling to an intermediate temperature T₂ between 23°C and temperature T₁ resulting in a two-phase composition comprising: - a phase P1 comprising the compound of formula (III); - a phase P2; c) a step of separating phases P1 and P2 at temperature T₂; d) a step of cooling phase P1 to a temperature T₃ until crystals of the compound of formula (III) are formed.

Description

2- (FLUOROALKYL OR FLUOROALKOXY) -4,5-DICYANOIMIDAZOLES PURIFICATION PROCESS

FIELD OF THE INVENTION

The present invention relates to a process for the purification of imidazole.

The present invention also relates to a process for preparing lithium salt of imidazolate.

TECHNICAL BACKGROUND

A lithium-ion battery includes at least a negative electrode, a positive electrode, a separator, and an electrolyte. The electrolyte consists of a lithium salt dissolved in a solvent which is generally a mixture of organic carbonates, in order to have a good compromise between viscosity and dielectric constant.

Among the most widely used salts is lithium hexafluorophosphate (LiPF ₆ ), which has many of the many qualities required but has the disadvantage of degrading in the form of hydrofluoric acid gas. This poses safety problems, particularly in the context of the use of lithium-ion batteries for private vehicles.

Other salts have therefore been developed to provide electrolytes for Li-ion batteries, and in particular LiTDI (lithium 1-trifluoromethyl-4,5-dicarbonitrile-imidazolate) and LiPDI (1-pentafluoroethyl-4,5-dicarbonitrile lithium imidazolate), as described in WO 2010/023413. These salts have the advantage of having fewer fluorine atoms and of having strong carbon-fluorine bonds instead of the weaker phosphorus-fluorine bonds of LiPF ₆ . In addition, these salts exhibit very good conductivities of the order of 6 mS / cm, very good dissociation between the imidazolate anion and the lithium cation.

WO 2010/023413 proposes several synthetic routes for the manufacture of these pentacyclic anions, one of which consists of the condensation of diaminomaleonitrile (DAMN) on an acid derivative such as a fluorinated acid anhydride, followed by a proton / lithium exchange. The condensation is carried out in a single step.

WO 2015/49435 describes the preparation of fluoroalkyl-4,5-dicyanoimidazole salts of purity compatible with applications in batteries or in ionic liquids. The process involves the use of activated carbon to purify the salts of pentacyclic anions. However, the use of activated carbon is a delicate operation and capable of bringing ions such as Ca ²⁺ or K ⁺ ions into the medium, which can lead to a decrease in performance in the batteries. In addition, activated carbons commonly require washing in depth before use, which is restrictive and expensive. Finally, at least one recrystallization step is necessary to obtain the desired purity and an acceptable Hazen coloration.

There is therefore a need to provide a novel process for the preparation of salts of pentacyclic anions which can at least partially overcome at least one of the aforementioned drawbacks.

DESCRIPTION OF THE INVENTION

Purification process

The present invention relates to a process for the purification of a compound of the following formula (III):

wherein Rf is a fluorinated alkyl or fluorinated alkoxyl group comprising from 1 to 5 carbon atoms, said process comprising the following steps: a. a step of heating a composition comprising said compound of formula (III) in an organic solvent S3, at a temperature Ti until dissolution of said compound of formula

(ni); b. a step of cooling to an intermediate temperature T ₂ of between 23 ° C and the temperature Ti leading to a two-phase composition comprising:

- a phase P1 comprising said compound of formula (III);

- a phase P2; vs. a step of separating the phases P1 and P2 at the temperature T ₂ ; d. a step of cooling phase P1 to a temperature T ₃ until the formation of crystals of the compound of formula (III).

According to one embodiment, Rf represents CF ₃ , CHF ₂ , C ₂ F ₅ , C ₃ F, C ₂ F OCF ₃ , or CF ₂ OCF ₃ preferably CF ₃ , C ₂ F ₅ , or C ₂ F ₄ OCF ₃ .

Preferably, the compound of formula (III) is that for which Rf represents CF ₃ . According to one embodiment, the present invention relates to a process for purifying a compound of the following formula (III):

wherein Rf is C2F4OCF3 OR a fluorinated alkyl or fluorinated alkoxyl group comprising from 1 to 5 carbon atoms, said process comprising the following steps: a. a step of heating a composition comprising said compound of formula (III) in an organic solvent S3 having a donor number ranging from 0.1 to 10, at a temperature Ti until dissolution of said compound of formula (III); b. a step of cooling to an intermediate temperature T ₂ of between 23 ° C and the temperature T1 leading to a two-phase composition comprising:

- a phase P1 comprising said compound of formula (III);

Heating step a)

The organic solvent S3 preferably has a donor number ranging from 0.1 to 10.

The donor index of a solvent represents the value -DH, DH being the enthalpy of the interaction (Kcal / mol) between the solvent and the antimony pentachloride (Journal of Solution Chemistry, vol. 13, No. 9 , 1984).

The organic solvent S3 is preferably chosen from aromatics or aliphatic or cyclic alkanes, such as, for example, toluene, benzene, xylene, cyclohexane, heptane. Preferably, the organic solvent S3 is toluene.

The temperature Ti is the temperature at which the compound of formula (III) is dissolved in the organic solvent S3. The temperature Ti can be between 40 ° C and the boiling point of the organic solvent S3, preferably between 50 ° C and 120 ° C, advantageously between 60 ° C and 100 ° C. The temperature Ti is advantageously equal to 70 ° C.

The composition used in step a), comprising the compound of formula (III) and the organic solvent S3, can be obtained by contacting the organic solvent S3 with the compound of formula (III) in solid form.

Before step a), the compound of formula (III) can be in hydrated form, that is to say that the compound of formula (III) can contain a water content of between 1% and 25%, preferably between 5% and 20% and preferably between 10% and 16% by weight relative to the total weight of the compound of formula (III).

Before step a), the mass content of the compound of formula (III) in the composition comprising the organic solvent S3 can range from 1% to 70% by weight, preferably from 5% to 50% by weight, preferably from 8 % to 30% by weight relative to the total weight of said composition.

Cooling step b)

The temperature T ₂ is between 23 ° C and the temperature Ti, preferably between 23 ° C and 50 ° C, and advantageously between 30 ° C and 50 ° C.

Step b) leads to a two-phase composition comprising:

- a phase P1 comprising said compound of formula (III); and

- a phase P2.

Phase P1 is advantageously a liquid phase, it comprises in particular organic solvent S3.

Phase P1 preferably comprises more than 30%, preferably more than 35%, and advantageously more than 40% of the compound of formula (III) initially contained in the solution obtained at the end of step a).

Phase P1 preferably comprises from 0.5% to 70% by weight, preferably from 1% to 50% by weight, preferably from 5% to 30% by weight of the compound of formula (III) relative to the total weight of said phase P1.

Phase P2 can comprise compound of formula (III) in a content strictly less than 45%, preferably less than 35% of the initial content of compound of formula (III) in the solution obtained at the end of stage at). Phase P2 can comprise impurities resulting from the process for preparing the compound of formula (III), such as coloring agents and TFA.

Preferably, phase P2 has a higher density than that of phase P1.

Phase P2 can be separated from phase P1, for example by settling followed by purging of the lower phase or by pumping of the upper phase.

Cooling step d)

The purification process according to the invention comprises a step of cooling phase P1 to a temperature T ₃ until the formation of crystals of the compound of formula (III).

The temperature T ₃ can be between 40 ° C and -30 ° C, preferably between 25 ° C and -15 ° C, and even more preferably between 10 ° C and -5 ° C. The temperature T3 is advantageously 0 ° C.

The temperature T ₃ is advantageously the temperature at which the compound of formula (III) crystallizes from the organic solvent S3.

Steps a, b, c, d can be repeated on P2 in order to recover more compound III. The number of repetitions is between 2 and 4, preferably 3.

Additional steps

The aforementioned purification process may include an additional step e) of filtering the composition obtained at the end of step d). Filtration advantageously results in a compound of formula (III) in solid form and in a filtrate.

The solid is advantageously subjected to an additional drying step, preferably under a stream of nitrogen at 23 ° C or more.

The aforementioned purification process advantageously makes it possible to prepare a compound of formula (III) with a good yield and a reduced content of impurities, in particular a reduced content of agents capable of coloring the product, and / or of TFA (trifluoroacetic acid) and / or in amides derived from the compound of formula (III):

The purification process advantageously makes it possible to prepare a compound of formula (III) having less coloration. The purification process also advantageously makes it possible to obtain a compound of formula (III) with a good yield and a reduced content of impurities in a smaller number of steps, without the need for costly additional purification steps.

Preliminary steps

The purification process according to the invention can comprise a step a ’), prior to step a), of bringing the compound of formula (III) into contact with the organic solvent S3. Preferably, the organic solvent S3 is added to the compound of formula (III).

The compound of formula (III) from step a ′) can be obtained by a process comprising the following steps:

- x) step of bringing a compound of formula (III) into contact with water, preferably in a mass ratio of compound of formula (III): water ranging from 1: 1 to 1: 4, advantageously from 1: 1 to 1: 2;

- y) step of heating the composition obtained in step x) at a temperature T ₆ , preferably between 30 ° C and 80 ° C, advantageously between 40 ° C and 70 ° C;

- z) step of cooling the composition obtained in step y) until the formation of crystals of compound of formula (III);

- z ’) stage of filtering the crystals, and optionally drying;

- z ") optional step of washing the crystals with water, in particular at 23 ° C, and optionally a drying step.

The compound of formula (III) in step x) can be obtained by any process for preparing a compound of formula (III), optionally subjected to a step of evaporating the reaction solvent.

Synthesis of the compound of formula

The above-mentioned compound of formula (III) can be obtained by a process comprising: i. a step of reaction of the diaminomaleonitrile of formula (I):

with the compound of formula (II) below:

in which Y represents a chlorine atom or the OCORf group, to form the salified amide compound of formula (IVa) and / or the corresponding amine (IVb), at a temperature T ₄

(IVa) (IVb) ii. dehydration of the salified amide compound of formula (IVa) and / or the corresponding amine of formula (IVb) to form the imidazole compound of formula (III), at a temperature T ₅ greater than T ₄ .

The temperature T which can range from 0 to 80 ° C, preferably from 10 to 50 ° C, more preferably from 20 to 30 ° C, for example about 25 ° C.

According to one embodiment, step (i) lasts from 1 to 12 hours, preferably from 1 to 3 hours, and / or step (ii) lasts from 1 to 12 hours, preferably from 1 to 3 hours .

According to one embodiment, the diaminomaleonitrile of formula (I) and the compound of formula (II) are dissolved in a solvent prior to step (i), the solvent preferably being 1, 4-dioxane.

Step (i) is preferably carried out by dissolving the reagents in an S1 solvent.

The solvent S1 can be chosen from the group consisting of 1, 4-dioxane, toluene, dimethylformamide, and their mixtures, the solvent S1 preferably being 1, 4-dioxane.

The concentration of DAMN of formula (I) in the reaction medium of step (i) is preferably from 0.001 to 2 mol / L, more preferably from 0.1 mol / L to 1 mol / L. The molar ratio of compound (I) to compound (II) is preferably from 0.25 to 1.5, more preferably from 0.5 to 1.25. The second step (ii) is carried out at a temperature T ₅ which is greater than T. Preferably, T ₅ is greater than T ₄ by at least 10 ° C, or by at least 20 ° C, or by at least 30 ° C, or by at least 40 ° C, or by at least 50 ° C, or at least 60 ° C, or at least 70 ° C.

According to a particular embodiment, the temperature T ₅ corresponds to the boiling point of the solvent used.

Preferably, T ₅ ranges from 30 to 180 ° C, more particularly from 60 to 150 ° C, more preferably from 75 to 140 ° C, for example around 100 or 101 ° C (which corresponds to the temperature of boiling 1,4-dioxane).

The concentration of compound (IVa) and / or (IVb) in the reaction medium during the second step preferably ranges from 0.001 to 2 mol / L, more preferably from 0.05 mol / L to 0.75 mol / L.

Preferably, the second step (ii) is carried out immediately following the first step without intermediate purification and advantageously without any separation step, simply by modifying the temperature of the reaction mixture, by heating.

In the case where Y = Cl, the amide is salified by adding a carboxylic acid which also makes it possible to improve the yield of the second stage by acid catalysis. The acids used are, for example, trifluoroacetic acid, acetic acid or benzoic acid and preferably trifluoroacetic acid.

The molar ratio of compound (IVa) and / or (IVb) to the catalyst preferably ranges from 0.5 to 20, more preferably from 1 to 10.

The temperature of the reaction T may be constant throughout the first step, and the temperature of the reaction T ₅ may be constant throughout the second step, but this is not necessarily the case. For example, it is possible to provide for an increasing temperature throughout the reaction, or throughout the first step only. In such cases, the condition that T ₅ is greater than T means that the temperature over the whole of the second step is higher than the temperature over the whole of the first step, that is to say again that the minimum temperature reached during the second stage is greater than the maximum temperature reached during the first stage.

A transition period may be necessary to go from the first stage to the second stage and to effect the required temperature change. This transition period preferably has a duration of less than 1 hour, for example less than 30 minutes, for example less than 20 minutes, for example less than 10 minutes, for example less than 5 minutes. The above-mentioned steps i) and ii) can be followed by a step of distilling a solvent S1 / water azeotrope, in particular at a temperature ranging from 40 ° C to 90 ° C.

Process for preparing lithium imidazolate

The present invention also relates to a process for preparing a lithium imidazolate compound of formula (V):

wherein Rf is a fluorinated alkyl or fluorinated alkoxyl group comprising from 1 to 5 carbon atoms, said method comprising:

1) the purification of the compound of formula (III) according to the process as described above; and

- 2) reaction of the compound of formula (III) with a lithiated base.

According to one embodiment, Rf represents CF ₃ , CHF ₂ , C2F5, C3F7, C2F4OCF3, or CF2OCF3, preferably CF ₃ , C2F5, C2F4OCF3.

According to one embodiment, the present invention relates to a process for preparing a lithium imidazolate compound of formula (V), in which Rf is a fluorinated alkyl or fluorinated alkoxyl group comprising from 1 to 5 carbon atoms or C2F4OCF3, said process comprising:

- 2) reaction of the compound of formula (III) with a lithiated base.

Preferably, the compound of formula (V) is that for which Rf represents CF ₃ . The lithiated base can be selected from the group consisting of lithium hydride, lithium carbonate, lithium hydroxide, and mixtures thereof. Preferably, the lithiated base is lithium carbonate.

The lithiated base can be in solid form or in the form of an aqueous or organic composition (for example a suspension or a solution). The concentration of lithiated base in the aqueous or organic composition preferably ranges from 0.01 to 10 mol / L, more preferably from 0.1 to 5 mol / L.

The compound of formula (III) obtained at the end of the purification process as described above can be in solid form, or in solution in an organic solvent. The compound (III) can be at a concentration which preferably ranges from 0.01 to 5 mol / L, more preferably from 0.1 to 3 mol / L in the organic phase.

Preferably, prior to step 2), the compound of formula (III) is dissolved in an organic solvent S4, preferably having a donor number ranging from 1 to 70, advantageously from 5 to 65. As solvent S4, one can mention in particular esters, nitriles or ethers. Advantageously, the organic solvent S4 is chosen from methyl acetate, ethyl acetate, butyl acetate, acetonitrile, propionitrile, isobutyronitrile, glutaronitrile, dioxane, or tetrahydrofuran, and even more preferably acetonitrile.

Preferably, step 2) comprises adding a composition comprising the compound of formula (III) in an aqueous lithiated base composition.

The reaction of step 2) can be carried out at a temperature between 0 ° C and 100 ° C, preferably between 10 ° C and 50 ° C, even more preferably between 20 ° C and 30 ° C.

The duration of step 2) can be between 1 h and 72 h, preferably between 3 h and 24 h, even more preferably between 6 h and 18 h.

The process may include an additional step of evaporating the water and the solvent, preferably under vacuum. In the case where there is an organic solvent, the water is preferably removed by azeotropic distillation.

The process can comprise an additional step of recrystallization of the compound of formula (V) in an organic solvent S4 as defined above.

The use of the purification process according to the invention advantageously makes it possible to prepare the compounds of formula (V), and in particular LiTDI, with an improved yield, and in particular with a reduced number of steps.

The purification process according to the invention advantageously leads to compounds of formula (V), and in particular LiTDI, having a reduced content of impurities, such as by example a reduced or even zero content of amide-LiTDI, of Ca ²⁺ , K ⁺ , TFA-Li, etc., and less coloration.

The purification process according to the invention advantageously makes it possible to prepare the compounds of formula (V), and in particular LiTDI, with improved purity without requiring the use of numerous additional purification steps. Such purity advantageously allows the use of compounds of formula (V) in batteries or in ionic liquids.

In the context of the invention, by "between x and y", or "ranging from x to y", is meant an interval in which the limits x and y are included. For example, the temperature “between -20 and 80 ° C” notably includes the values -20 ° C and 80 ° C.

The present invention is illustrated by the following example, to which it is, however, not limited.

EXAMPLES

The Hazen coloration is measured according to the Hazen standard, for dissolving (I) in a non-absorbent solvent in the Visible range, at a concentration of 1 mol / L, on a Hach Licol 50 spectrophotometer, in cells of 11 mm in diameter. When a solution provides a value of less than 10 Hazen, the optical path is increased by using a 50mm cell for more precision. The Hazen values given in the examples are the means of 3 measurements of the same solution.

For the examples, the NMR analysis conditions for fluorinated species in F19, H1, C13 NMR are as follows:

Equipment: The NMR spectra and quantifications were carried out on a Bruker AV 400 spectrometer, at 100.62 MHz for C13 and 376.47 MHz for F19, on a 5 mm BBFO ⁺ type probe.

Sample: The samples are dissolved in DMSO-d6 (approximately 30 mg in 0.6 ml). In the case of the detection of fluorides or the addition of LiF to check for the unwanted presence of fluorides, the solvent is D2O due to the insolubility of LiF in DMSO.

Quantification: The relative quantification in F19 NMR is carried out by integration of the signals of the fluorinated species, weighted by the number of fluorine contributing to the signal, a method well known to those skilled in the art. The absolute quantification in F19 NMR is made by metered addition of α, α, α-trifluorotoluene (TFT), Aldrich in the tube containing the compound, and by integration of the signals of the fluorinated species to be assayed in comparison with that of the CF ₃ of this internal standard, according to a method well known to those skilled in the art. The limit of quantification of such a species than LiTDI at the frequency of 376.47 MHz and the chosen probe is of the order of about fifty ppm.

Example 1 method for preparing HTDI

20 kg DAMN (diaminomaleonitrile), 98% purity, in 60 kg of 1, 4- are introduced into a vitrified 100-liter reactor fitted with a condenser, a reagent introduction pump and a temperature measurement. dioxane at room temperature (23 ° C). The suspension is stirred while 40.4 kg of trifluoroacetic anhydride (TFAA) of 99% purity is introduced by means of the pump; the rate of introduction of the TFAA is adjusted so that the reaction medium remains at a temperature below 30 ° C (reactor wall temperature around 12 ° C). The suspension quickly turns into a brown colored solution. When all of the trifluoroacetic anhydride is introduced, the medium is left under stirring for 15 minutes then the temperature of the reaction medium is increased until the dioxane refluxes (105 ° C) (Reactor wall temperature: 130 ° C max ) which is maintained so that this entire operation lasts 30 minutes of reflux.

Then the temperature of the double wall is adjusted to 100 ° C and the pressure in the reactor is gradually reduced to distill the dioxane / water azeotrope at 70 ° C. Four additions of 10 kg of dioxane are made at this temperature while continuing the distillation. The pressure is adjusted so as to ensure distillation of the solvent at 60 ° C. The medium is concentrated at 60 ° C until a brown oil is obtained. This oil is then taken up in water with a water: oil mass ratio of 1: 1. The whole is stirred and heated to 60 ° C until a homogeneous brown paste is obtained, then cooled. The crystals obtained are then filtered and then resuspended in water at room temperature (23 ° C) and then filtered. This operation is done three times in all.

The solid is partially dried overnight at room temperature (23 ° C) under a stream of nitrogen. 33.7 kg of brown crystals of HTDI are obtained.

Example 2: purification of HTDI

The product obtained in Example 1 is taken up in 280 kg of toluene and, with stirring, is brought to 70 ° C for 2 hours. A colored solution is obtained. Cooled to 40 ° C, and two phases are obtained. A very colored heavy phase gradually forms at the bottom of the reactor. This is purged. The light yellow solution is recovered. By cooling to 0 ° C, solid HTDI is recovered. The solid HTDI is recovered by filtration and then washing with toluene at a temperature between 0 ° C and 25 ° C.

The colored lower phase is treated twice with toluene according to the same principle. Example 3: process for preparing LiTDI

The solid HTDI obtained in Example 2 is dissolved in acetonitrile to obtain a solution of between 40% and 50% by weight of HTDI. At room temperature, this solution is gradually added to a suspension of 5 kg of U ₂ CO ₃ in 94 kg of acetonitrile while controlling the evolution of CO ₂ . The mixture is left under stirring at room temperature (23 ° C.) overnight.

The water of reaction is removed by distillation of the water / CH ₃ CN azeotrope. The excess lithium carbonate is filtered off and the reaction medium is then concentrated at 70 ° C. under reduced pressure to a LiTDI / CH ₃ CN concentration of 30% by weight.

The concentrate is cooled to -10 ° C. LiTDI crystallizes. It is filtered, rinsed twice with acetonitrile cooled to -20 ° C. Its purity measured by NMR is 100%.

It is then dried first under a stream of nitrogen and then under vacuum at 75 ° C. In ion chromatography, the lithium content is measured at 3.63%. The Hazen color is 14. The overall yield relative to the DAMN is 43%, ie 14.7 kg of LiTDI.

The process advantageously makes it possible to obtain LiTDI with a Hazen coloration of 14 without having to carry out an activated carbon treatment.

Claims

1. Process for the purification of a compound of the following formula (III):

wherein Rf is a fluorinated alkyl or fluorinated alkoxyl group comprising from 1 to 5 carbon atoms, said process comprising the following steps: a. a step of heating a composition comprising said compound of formula (III) in an organic solvent S3, at a temperature Ti until said compound of formula (III) is dissolved; b. a step of cooling to an intermediate temperature T ₂ of between 23 ° C and the temperature Ti leading to a two-phase composition comprising:

- a phase P1 comprising said compound of formula (III);

2. Method according to claim 1, characterized in that Rf represents CF ₃ , CHF ₂ , C ₂ F ₅ , C ₃ F, C ₂ F OCF ₃ , OR CF ₂ OCF _3, preferably CF ₃ , C ₂ F ₅ , or C ₂ F ₄ OCF ₃ .

3. Method according to any one of claims 1 or 2, characterized in that Rf represents CF ₃ .

4. Method according to any one of claims 1 to 3, characterized in that the organic solvent S3 preferably has a donor number ranging from 0.1 to 10.

5. Method according to any one of claims 1 to 4, characterized in that the organic solvent S3 is chosen from aromatics or aliphatic alkanes or cyclic, such as for example toluene, benzene, xylene, cyclohexane, heptane.

6. Method according to any one of claims 1 to 5, characterized in that the temperature Ti is between 40 ° C and the boiling point of the organic solvent S3, preferably between 50 ° C and 120 ° C, advantageously between 60 ° C and 100 ° C.

7. Method according to any one of claims 1 to 6, characterized in that before step a), the compound of formula (III) contains a water content of between 1% and 25%, preferably between 5%. and 20% and preferably between 10% and 16% by weight relative to the total weight of the compound of formula (III).

8. Method according to any one of claims 1 to 7, characterized in that the temperature T ₂ is between 23 ° C and 50 ° C, and advantageously between 30 ° C and 50 ° C.

9. Method according to any one of claims 1 to 8, characterized in that phase P1 comprises more than 30%, preferably more than 35%, and advantageously more than 40% of the compound of formula (III) initially contained in the solution obtained at the end of step a).

10. Method according to any one of claims 1 to 9, characterized in that phase P1 comprises from 0.5% to 70% by weight, preferably from 1% to 50% by weight, preferably from 5% to 30. % by weight relative to the total weight of said phase P1.

11. Method according to any one of claims 1 to 10, characterized in that the temperature T ₃ is between 40 ° C and -30 ° C, preferably between 25 ° C and - 15 ° C, and even more preferably between 10 ° C and -5 ° C.

12. Method according to any one of claims 1 to 11, characterized in that it comprises an additional step e) of filtering the composition obtained at the end of step d).

13. Method according to any one of claims 1 to 12, characterized in that it comprises a step a ′), prior to step a), of bringing the compound of formula (III) into contact with the organic solvent. S3.

14. Method according to any one of claims 1 to 13, characterized in that the compound of formula (III) from step a ’) is obtained by a process comprising the following steps:

- z ’) stage of filtering the crystals, and optionally drying;

- z ") optional step of washing the crystals with water, in particular at 23 ° C, and possibly a drying step.

15. Process for preparing a lithium imidazolate compound of formula (V):

- 1) the purification of the compound of formula (III) according to the process as described according to any one of claims 1 to 14; and

- 2) reaction of the compound of formula (III) with a lithiated base.

16. The method of claim 15, characterized in that the lithiated base is selected from the group consisting of lithium hydride, lithium carbonate, lithium hydroxide, and mixtures thereof.

17. Method according to any one of claims 15 or 16, characterized in that, prior to step 2), the compound of formula (III) is dissolved in an organic solvent S4, preferably having a donor number ranging from 1 to 70, preferably 5 to 65.