Method for the generation of a phosphorus trifluoride, a hexafluorophosphate, a phosphorus trihalogenide, phosphoric acid or a phosphorus-comprising organic compound

Abstract

The invention concerns a method for the generation of phosphorus trifluoride or a a mixture of a hexafluorophosphate and a phosphorus trifluoride or a hexafluorophosphate, a phosphorus trihalogenide, wherein the phosphorus trihalogenide is a phosphorus trichloride, a phosphorus tribromide or a phosphorus triiodide, phosphoric acid, a mixture of a tertiary phosphite ester and a phosphoric acid triester, or a tertiary aminophosphine, wherein the method comprises the following steps: a) providing an elemental phosphorus, a solvent, an oxidant having a pi-conjugated system and at least two and at most eight electron-withdrawing groups selected from chlorine, bromine, cyano and oxo, and either a fluoride anion, a chloride anion, a bromide anion, a iodide anion, water, a compound R1-OH, or a compound R2-NX1-R3, b) mixing the elemental phosphorus, the oxidant, and either the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1-OH or the compound R2-NX1-R3 in the solvent and c) adjusting a mixture obtained in step b) to a temperature in the range of 20 °C to 95 °C and maintaining the temperature.

Description

[0001] Method for the generation of a phosphorus trifluoride, a hexafluorophosphate, a phosphorus trihalogenide, phosphoric acid or a phosphorus-comprising organic compound

[0002] The present invention relates to a method for the generation of a phosphorus trifluoride, a hexafluorophosphate, a phosphorus trihalogenide, phosphoric acid or a phosphorus-comprising organic compound.

[0003] Industrial routes to phosphorus-comprising organic compounds involve oxidation of phosphorus by chlorine gas to give phosphorus chlorides, for example PCh, PCIs, and POCI3, as intermediates which are subsequently reacted with nucleophiles to generate phosphorus-comprising organic compounds.

[0004] In Hoidn et a. "Transition-Metal-Mediated Functionalization of White Phosphorus", Chem. - Eur. J., 2021 , 27, 1886 - 1902, the transition-metal mediated synthesis of phosphorus-containing products in a two-step process is disclosed. This approach includes the activation of white phosphorus to generate a polyphosphorus transition metal complex and its subsequent functionalization with an appropriate reagent to release the desired phosphorus-containing product.

[0005] EP 0 643 433 B1 discloses a method for preparing LiPF6-based electrolytes for use in lithium non-aqueous batteries. LiPF6is synthesized in a mixture of solvents employed in the electrolyte itself. Residual reactants and by-products of the reaction are removed while the LiPF6remains in solution. Additional required solvents, such as diethylcarbonate, ethylene carbonate, and propylene carbonate, are employed.

[0006] US 5,993,767 A discloses a lithium hexafluorophosphate solvate usable for the preparation of high purity lithium hexafluorophosphate. The solvate of lithium hexafluorophosphate and pyridine complies with the formula Li(CsH5N)PF6 and is prepared by a process comprising the following stages: a) preparation of pyridinium hexafluorophosphate of formula C5H5NHPF6 by the neutralization of hexafluorophosphoric acid HPFe with pyridine and b) conversion of the pyridinium hexafluorophosphate into solvate Li(CsH5N)PF6 by exchange with a lithium compound chosen from among lithium hydroxide, lithium alkoxides and alkyl lithiums.

[0007] In WO 2015 / 150862 A1 a process for producing a hexafluorophosphate salt comprising neutralizing hexafluorophosphoric acid with an organic Lewis base to obtain an organic hexafluorophosphate salt is disclosed. The organic hexafluorophosphate salt is reacted with an alkali hydroxide selected from an alkali metal hydroxide (other than LiOH) and an alkaline earth metal hydroxide, in a non-aqueous suspension medium, to obtain an alkali hexafluorophosphate salt as a precipitate. A liquid phase comprising the non-aqueous suspension medium, any unreacted organic Lewis base and any water that has formed during the reaction to form the precipitate, is removed. Thereby, the alkali hexafluorophosphate salt is recovered.

[0008] US 3,380,803 A discloses a process for preparing hexafluorophosphates which comprises heating a mixture of a member of the group consisting of alkali metal fluorides and alkaline earth metal fluorides, elemental phosphorus and anhydrous hydrogen fluoride at 180 to 220 °C under autogenous pressure to form a reaction mixture containing a hexafluorophosphate of said metal and separating said hexafluorophosphate from said reaction mixture.

[0009] Annan, T. A. et al. "Studies of the oxidation of elemental phosphorus by substituted ortho-benzoquinones", 1991. J. Chem. Soc., Dalton Trans. 19, discloses the preparation of the phosphorus compound P(O2CeR)2Br (R = Ch, BR or BU2H2) by the reaction of red phosphorus, Br2 and a substituted orthobenzoquinone. When white phosphorus was used in the synthesis of [NHEt3][P(O2R)3 salts, UV irradiation was necessary to achieve the reaction. US 2008 / 242870 A1 discloses a procedure according to which a mixture of 1 ,5- dichloroanthraquinone, red phosphorus and hydroiodic acid in glacial acetic acid are refluxed under N2 for 4 days for obtaining 1 ,5-dichloro-9,10-dihydro anthracene.

[0010] The problem to be solved by the present invention is to provide an alternative method to generate a phosphorus-comprising compound. The method shall allow the direct synthesis of the phosphorus-comprising compound by relatively mild reagents with a relatively low amount of waste products generated in addition to the phosphorus-comprising compound.

[0011] The problem is solved by the subject-matter of claim 1. Embodiments of the invention are subject-matter of claims 2 to 13.

[0012] According to the invention a method for the generation of either

[0013] - a phosphorus trifluoride or a mixture of a hexafluorophosphate and a phosphorus trifluoride or a hexafluorophosphate,

[0014] - a phosphorus trihalogenide, wherein the phosphorus trihalogenide is a phosphorus trichloride, a phosphorus tribromide or a phosphorus triiodide,

[0015] - phosphoric acid, a mixture of a tertiary phosphite ester according to formula (I) and a phosphoric acid triester according to formula (II), or a tertiary aminophosphine according to formula (III), is provided. R1, R2and R3are each selected independently from each other from a group consisting of alkyl, aryl, heterocyclyl and heteroaryl. In particular, R1may be aryl. In particular, R2and R3may be alkyl. The method comprises the following steps: a) providing an elemental phosphorus, a solvent, an oxidant having a pi- conjugated system and at least two and at most eight electron-withdrawing groups selected from chlorine, bromine, cyano and oxo, and either a fluoride anion for obtaining the phosphorus trifluoride or the mixture of the hexafluorophosphate and the phosphorus trifluoride or the hexafluorophosphate, a chloride anion for obtaining the phosphorus trichloride, a bromide anion for obtaining the phosphorus tribromide, a iodide anion for obtaining the phosphorus triiodide, water for obtaining the phosphoric acid, a compound R1-OH for obtaining the mixture of the tertiary phosphite ester according to formula (I) and the phosphoric acid triester according to formula (II), or a compound R2-NX1-R3for obtaining the tertiary aminophosphine according to formula (III), wherein X1is selected from a group consisting of an alkali metal atom residue, a magnesium halogenide residue or a hydrogen residue, b) mixing the elemental phosphorus, the oxidant, and either the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1-OH or the compound R2-NX1-R3in the solvent and c) adjusting a mixture obtained in step b) to a temperature in the range of 20 °C to 95 °C and maintaining the temperature, in particular maintaining the temperature for at least 1 minute and at most 168 hours.

[0016] Here and in the following chemical constituents mentioned in singular forms are to be understood as a plurality of molecules of these constituents. For example, the term "an oxidant" means a plurality of molecules of the oxidant and the term "a fluoride anion" means a plurality of fluoride anions.

[0017] Unless defined otherwise or used according to a term's general meaning, the following definitions apply:

[0018] As used herein, “C1-6 alkyl” is any saturated linear or branched alkyl group having 1 to 6 carbon atoms. Examples thereof include methyl, ethyl, propyl, isopropyl, n- butyl, sec-butyl, tert-butyl, pentyl and hexyl. “Cs-10 cycloalkyl” refers to any cyclic version of alkyl having 5 to 10 carbon atoms.

[0019] The term “cycloalkyl” is also meant to include bicyclic, tricyclic and polycyclic versions thereof.

[0020] “Ce- aryl” refers to any aromatic mono- or polycyclic ring containing 6 to 10 carbon atoms. Examples are phenyl or naphthyl, preferably phenyl.

[0021] “5- to 10-membered heteroaryl” refers to any 5- to 10-membered aromatic ring wherein one or more of the carbon atoms in the ring has / have been replaced by one or more of the same or different heteroatoms. The heteroatoms are selected from 0, N and S. Examples of the heteroaryl group include pyrrole, furan, thiophene, imidazole, pyrazole, oxazole, thiazole, pyridine, pyridazine, pyrimidine and pyrazine.

[0022] “5- to 10-membered heterocyclyl” refers to any 5- to 10-membered non-aromatic ring wherein one or more of the carbon atoms in the ring has / have been replaced by one or more of the same or different heteroatoms. The heteroatoms are selected from 0, N and S. Examples of the heterocyclyl group include pyrrolidine, pyrroline, pyrazolidine, pyrazoline, imidazolidine, imidazoline, oxolane, dioxolane, tetrahydrothiophene, oxazolidine, piperidine, morpholine, piperazine, tetrahydropyran, pyran, dioxane, thiane and dithiane.

[0023] "Halogen" represents F, Cl, Br or I.

[0024] "Oxo" represents a double-bonded oxygen atom (=0) on carbon, i.e. carbonyl, or on any other element.

[0025] If a compound or moiety is referred to as being "optionally substituted", it can in each instance include one or more of the indicated substituents, whereby the substituents can be the same or different ones. In the context of the present invention, a pi-conjugated system is a system of connected p orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability. It is conventionally represented as having alternating single and multiple bonds. Lone pairs, radicals or carbenium ions may be part of the system, which may be cyclic, acyclic, linear or mixed. Conjugation is the overlap of one p orbital with another across an intervening sigma bond. A pi-conjugated system has a region of overlapping p orbitals, bridging the interjacent locations that simple diagrams illustrate as not having a pi bond. They allow a delocalization of pi electrons across all the adjacent aligned p orbitals. The pi electrons do not belong to a single bond or atom, but rather to a group of atoms.

[0026] The adjusting of the mixture obtained in step b) to the temperature according to step c) may be by cooling, by keeping the present temperature or by heating. The cooling may be performed as an active cooling or as a passive cooling, i.e. by letting it cool down to ambient temperature. The heating may be performed as an active heating or as a passive heating, i.e. by letting it heat up to ambient temperature.

[0027] The inventors of the present invention found that a common technical feature of the method according to the invention is that an intermediate is formed by mixing the elemental phosphorus and the oxidant and by adjusting the mixture obtained in step b) according to step c). The inventors of the present invention found that the method according to the invention allows a relatively high percentage conversion of the elemental phosphorus and the oxidant to the intermediate. The intermediate can react with either the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1-OH or the compound R2-NX1-R3in a nucleophilic substitution reaction. In the nucleophilic substitution reaction, the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1-OH or the compound R2-NX1-R3are nucleophiles. The inventors of the present invention further found that the reaction of the intermediate with one of the nucleophiles results in the phosphorus trifluoride or mixture of the hexafluorophosphate and the phosphorus trifluoride or the hexafluorophosphate, the phosphorus trihalogenide, the phosphoric acid, the mixture of the tertiary phosphite ester and the phosphoric acid triester or the tertiary aminophosphine. The inventors of the present invention further found that the oxidant is thereby reduced to an oxidant anion. The presence of the oxidant anion can be measured by UV / VIS spectroscopy.

[0028] The inventors of the present invention observed that providing a fluoride anion results in a relatively efficient generation of the phosphorus trifluoride or the mixture of the hexafluorophosphate and the phosphorus trifluoride or the hexafluorophosphate.

[0029] In contrast to the industrial route involving chlorine and the phosphine chloride intermediates, the method according to the invention allows the generation of a hexafluorophosphate, a phosphorus trifluoride, a phosphorus trihalogenide, phosphoric acid or a phosphorus-comprising organic compound with compounds of no or relatively low toxicity and of relatively low corrosivity. Thus, a much lower effort for ensuring occupational safety and health of production workers is required. The method according to the invention is suitable for large-scale industrial production of the phosphorus-comprising organic compound, phosphoric acid, the phosphorus trihalogenide, the phosphorus trifluoride and the hexafluorophosphate. Furthermore, in contrast to the industrial route involving chlorine and the phosphine chloride intermediates, a relatively low quantity of waste products is produced by the method according to the invention.

[0030] In contrast to the method known from US 3,380,803 A, the method according to the invention does not require anhydrous hydrogen fluoride to generate the hexafluorophosphate. Furthermore, the method according to the invention is not performed at a temperature of 180 to 220 °C under autogenous pressure to generate the hexafluorophosphate. Thus, in contrast to the method known from US 3,380,803 A, the method according to the invention allows the generation of hexafluorophosphate with relatively mild reaction conditions using relatively mild reagents.

[0031] In contrast to the method known from Annan, T. A. et al. "Studies of the oxidation of elemental phosphorus by substituted ortho-benzoquinones", 1991. J. Chem. Soc., Dalton Trans. 19, the method according to the invention does not require UV light to achieve the generation of the phosphorus-comprising organic compound. The inventors of the present invention found that neither the oxidant nor the oxidant anion as specified in the method according to the invention - in contrast to the ortho-benzoquinone in the method according to Annan et al. - does become a component of the phosphorus-comprising compound formed by the reaction. Thus, the oxidant enables the generation of a variety of phosphorus-comprising compounds by the method according to the invention that are totally different from the compounds generated according to Annan et al.

[0032] In an embodiment of the invention, the method is performed in the absence of UV irradiation.

[0033] The elemental phosphorus may be white phosphorus or red phosphorus. In particular, the elemental phosphorus may be white phosphorus.

[0034] The oxidant having a pi-conjugated system and at least two and at most eight electron-withdrawing groups selected from chlorine, bromine, cyano and oxo is a substituted para-quinone according to formula (IV), a substituted tetracyanoquinodimethane according to formula (V) or a tetracyanoethylene according to formula (VI), wherein R4, R5, R6and R7are each selected independently from each other from a group consisting of chlorine, bromine, cyano and hydrogen. The inventors of the present invention found that an intermediate is formed by mixing the elemental phosphorus and either the substituted para-quinone (SPQ) according to formula (IV), the substituted tetracyanoquinodimethane (STCNQ) according to formula (V) or the tetracyanoethylene according (TCNE) to formula (VI). If the intermediate is formed from the elemental phosphorus and the SPQ, the intermediate is Px(SPQ)y, where x is 1 and y is 3 or where x is 2 and y is either 3 or 5. If the intermediate is formed from the elemental phosphorus and the STCNQ, the inventors assume that the intermediate is Px(STCNQ)y, where x is 1 and y is 3 or where x is 2 and y is either 3 or 5. If the intermediate is formed from the elemental phosphorus and the TCNE, the inventors assume that the intermediate is Px(TCNE)y, where x is 1 and y is 3 or where x is 2 and y is either 3 or 5. The inventors of the present invention found that the method according to the invention allows a relatively high percentage conversion of the elemental phosphorus and either the SPQ, the STCNQ or the TCNE to the respective intermediate. In particular, the percentage conversion of the elemental phosphorus and the SPQ to the intermediate Px(SPQ)yis at least 90 %. The inventors of the present invention further found that the formed intermediate Px(SPQ)y, the formed intermediate Px(STCNQ)yor the formed intermediate Px(TCNE)yforms the phosphorus trifluoride or the mixture of the hexafluorophosphate and the phosphorus trifluoride or the hexafluorophosphate, the phosphorus trihalogenide, the phosphoric acid, the mixture of the tertiary phosphite ester and the phosphoric acid triester or the tertiary aminophosphine when brought into contact with the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1- OH or the compound R2-NX1-R3in the solvent. The inventors of the present invention further found that the SPQ is thereby reduced to an SPQ anion, that the STCNQ is thereby reduced to a STCNQ anion and that the TCNE is thereby reduced to an TCNE anion. The reduction of the SPQ to the SPQ anion, the reduction of the STCNQ to the STCNQ anion and the reduction of the TCNE to the TCNE anion can be measured by UV / VIS spectroscopy. Thus, a common technical effect of the SPQ, the STCNQ and the TCNE is that each of them acts as an oxidant in the method according to the invention.

[0035] In contrast to the method known from Annan, T. A. et al. "Studies of the oxidation of elemental phosphorus by substituted ortho-benzoquinones", 1991. J. Chem. Soc., Dalton Trans. 19, the method according to the invention involves the SPQ according to formula (IV), the STCNQ according to formula (V) or the TCNE according to formula (VI). The inventors of the present invention found that the SPQ, the STCNQ or the TCNE used in the method according to the invention - in contrast to the ortho-benzoquinone in the method according to Annan et al. - does not become a component of the phosphorus-comprising compound formed by the reaction. Thus, the SPQ, the STCNQ or the TCNE enables the generation of a variety of phosphorus-comprising compounds by the method according to the invention that are totally different from the compounds generated according to Annan et al.

[0036] R4and R6may be chlorine and R5and R7may be cyano in the substituted paraquinone according to formula (IV). Thus, the substituted para-quinone may be 2,3- dichloro-5,6-dicyano-1 ,4-benzoquinone (DDQ). The inventors of the present invention found that DDQ enables a relatively high percentage conversion, in particular a percentage conversion of at least 95 %, to a Px(DDQ)yintermediate, where x is 1 and y is 3 or where x is 2 and y is either 3 or 5. Furthermore, the inventors of the present invention found that the Px(DDQ)yintermediate allows the generation of the phosphorus trifluoride or the mixture of the hexafluorophosphate and the phosphorus trifluoride or the hexafluorophosphate, the phosphorus trihalogenide, the phosphoric acid, the mixture of the tertiary phosphite ester and the phosphoric acid triester or the tertiary aminophosphine in a relatively high yield. Furthermore, DDQ is relatively inexpensive and allows a relatively safe handling and a relatively safe usage in combination with relatively pyrophoric compounds, in particular elemental phosphorus.

[0037] The oxidant anion may be a radical anion, a dianion, an SPQ anion, an STCNQ anion or a TCNE anion. The SPQ anion may be a SPQ” radical anion or a SPQ2’ dianion. The SPQ” radical anion may be DDQ”. The SPQ2’ dianion may be DDQ2’. The STCNQ anion may be a STCNQ” radical anion or a STCNQ2’ dianion. The TCNE anion may be a TCNE” radical anion. Possible structural formulas of DDQ, the radical anion DDQ”, the DDQ2’ dianion, TCNQ, the TCNQ anions, TCNE and the TCNE” radical anion are exemplarily given below:

[0038]

[0039] In the above structural formulas, the position of the negative charge(s) cannot be indicated, as the negative charge(s) are delocalized within the pi-conjugated system of the respective oxidant anion.

[0040] The intermediate formed in the method according to the invention, in particular the Px(SPQ)y intermediate, the Px(STCNQ)yintermediate or the Px(TCNE)yintermediate, is to be understood to be a substance that changes due to redox transformation during the method according to the invention. In particular, the oxidant in the intermediate is reduced during the method according to the invention and the phosphorus in the intermediate is oxidized during the method according to the invention. In the method according to the invention, the oxidant, in particular the SPQ according to formula (IV), the STCNQ according to formula (V) or the TCNE according to formula (VI), can be formed again by oxidation of the oxidant anion, in particular the SPQ anion, the STCNQ anion or the TCNE anion, respectively. After the oxidant is formed again, the intermediate may be formed from the elemental phosphorus and the oxidant, respectively. Thus, the oxidant can be recycled in the method according to the invention.

[0041] The oxidation of the oxidant anion may be performed by electrochemical oxidation or by bringing the oxidant anion into contact with an oxidizing agent. The oxidizing agent may be a common oxidizing agent such as oxygen, tert-butyl nitrite, sodium nitrite, nitrogen dioxide, nitric acid, potassium persulfate or manganese dioxide. In one embodiment of the invention, the oxidizing agent is added to the elemental phosphorus, the solvent, the oxidant or either the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1-OH or the compound R2-NX1-R3before step b) or is mixed with the elemental phosphorus, the solvent, the oxidant and either the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1-OH or the compound R2-NX1-R3during step b) or is added to the mixture obtained in step b) between step b) and step c) and / or during or after step c). The oxidation may be carried out continuously. In the absence of oxygen, the oxidation may be performed under inert atmosphere. In the presence of oxygen, the oxygen may be oxygen gas or contained in an oxygen-containing gas mixture, such as air. For this purpose, the mixture obtained in step b) and / or the mixture obtained in step c) may be contacted with the oxygen gas or the oxygen-containing gas mixture by means of a mixing apparatus like a static mixer or via a liquid-impermeable, gas-permeable membrane. This enables a very effective and continuous oxidation of the oxidant anion, and thus allows a continuous and effective generation of the hexafluorophosphate, the phosphorus trifluoride, the phosphorus trihalogenide, the phosphoric acid, the tertiary phosphite ester, the phosphoric acid triester or the tertiary aminophosphine with a relatively low amount of waste products generated in addition to the hexafluorophosphate, the phosphorus trifluoride, the phosphorus trihalogenide, the phosphoric acid or the phosphorus-comprising organic compound. The fluoride anion may be provided by a fluoride salt, a bifluoride salt, a tetrafluoroborate salt, a hydrogen fluoride or a hydrofluoride. The fluoride salt may be an alkali fluoride salt or an ammonium fluoride salt. The alkali fluoride salt may be lithium fluoride, sodium fluoride, potassium fluoride or cesium fluoride. The ammonium fluoride salt may be NH4F or a quaternary ammonium fluoride salt. The quaternary ammonium fluoride salt may be tetramethylammonium fluoride, tetraethylammonium fluoride or tetrabutylammonium fluoride. The bifluoride salt may be an alkali bifluoride salt. The alkali bifluoride salt may be lithium bifluoride, sodium bifluoride or potassium bifluoride. The tetrafluoroborate salt may be lithium tetrafluoroborate, sodium tetrafluoroborate, potassium tetrafluoroborate or 1- (Chloromethyl)-4-fluoro-1 ,4-diazabicyclo[2.2.2]octane-1 ,4-diium bis(tetrafluoroborate). The hydrofluoride may be an amine hydrofluoride, in particular triethylamine trihydrofluoride.

[0042] In an embodiment of the invention, the chloride anion or the bromide anion are preferred vis-a-vis the iodide anion. The chloride anion may be provided by hydrogen chloride. The hydrogen chloride may be dissolved in 1 ,4-dioxane. The bromide anion may be provided by hydrogen bromide. The hydrogen bromide may be dissolved in 1 ,4-dioxane. The iodide anion may be provided by hydrogen iodide. The hydrogen iodide may be dissolved in 1 ,4-dioxane.

[0043] The alkyl may be C1-6 alkyl or C5-10 cycloalkyl. The aryl may be C6-10 aryl. The heteroaryl may be 5- to 10-membered heteroaryl. The heterocyclyl may be 5- to 10-membered heterocyclyl. The C1-6 alkyl, the C5-10 cycloalkyl, the C6-10 aryl, the 5- to 10-membered heterocyclyl and the 5- to 10-membered heteroaryl may be optionally substituted by halogen, C1-6 alkyl, C6-10 aryl, C5-10 cycloalkyl, 5- to 10- membered heterocyclyl, 5- to 10-membered heteroaryl, OR', COR', COOR', CONR'2 or NR'2. R' may be independently from each other selected from the group consisting of H, C1-6 alkyl, C6-10 aryl and C5-10 cycloalkyl. The alkyl carbon chain may be optionally interrupted by one or more -O-. The C5-10 cycloalkyl and 5- to 10-membered heterocyclyl may be optionally substituted by halogen, C1-6 alkyl, C6-io aryl, C5-10 cycloalkyl, 5- to 10-membered heterocyclyl, 5- to 10-membered heteroaryl, OR", COR", COOR", CONR' 2 or NR' 2. R" may be independently from each other selected from the group consisting of H, C1-6 alkyl, C6-10 aryl and C5-10 cycloalkyl.

[0044] The alkyl may be in particular methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, isopropyl, or an alkylamine residue. The alkylamine residue may be 1 -aminoethyl, 1 -aminopropyl, 2-aminopropyl, 1 -aminobutyl, 2- aminobutyl, amino-tert-butyl, 1 -aminopentyl, 2-aminopentyl, 3-aminopentyl, amino- neo-pentyl, amino-sec-pentyl, amino-tert-pentyl or diisopropylamino. The alkylamine residue may be in particular diisopropylamino.

[0045] The aryl may be in particular a phenyl, a monosubstituted phenyl, a disubstituted phenyl, a naphthyl, a substituted naphthyl, an anthryl, a substituted anthryl, a phenanthryl or a substituted phenanthryl. The monosubstituted phenyl may be 2- methyl-phenyl, 4-hydroxyphenylacetamide or 4-fluoro-phenyl. The disubstituted phenyl may be 3,5-(dimethoxy)phenyl.

[0046] The solvent may be an organic solvent or a mixture of at least two, in particular a mixture of at least three, in particular a mixture of at least four, in particular a mixture of at least five, organic solvents. The organic solvent may be an aromatic hydrocarbon, an alcohol, a chlorinated hydrocarbon, an ether, acetonitrile, dimethylformamide or dimethyl sulfoxide (DMSO). The aromatic hydrocarbon may be benzene or toluene. The alcohol may be methanol or ethanol. The chlorinated hydrocarbon may be dichloromethane or chloroform. The ether may be tetrahydrofuran, 1 ,4-dioxane or diethyl ether. The inventors of the present invention found that the solvent affects the ratio of the hexafluorophosphate and the phosphorus trifluoride formed in the method according to the invention. By providing dichloromethane as solvent, the yield of the phosphorus trifluoride can be increased and at the same time the yield of the hexafluorophosphate can be decreased or even suppressed. By providing dimethylformamide, acetonitrile, acetone and / or tetrahydrofuran as solvent, the yield of the hexafluorophosphate can be increased and at the same time the yield of the phosphorus trifluoride can be decreased or even suppressed.

[0047] The organic solvent may be in particular a polar aprotic solvent. For the purpose of the present invention, a polar solvent is defined as a solvent having a dielectric constant of at least 7 measured at 20 °C. A non-polar solvent is defined as a solvent having a dielectric constant of less than 7 at 20 °C. Here, the dielectric constant of a given solvent is the ratio of the electric permeability of the solvent to the electric permeability of free space, i.e. a vacuum. The dielectric constant may be measured by an LCR meter or an impedance analyzer by methods known in the art or can be taken from published scientific tables such as the following taken on December 21 , 2022 from https: / / organicchemistrydata.org / solvents / solvents:

[0048] The polar aprotic solvent may be in particular tetrahydrofuran, dichloromethane, acetone, acetonitrile or dimethylformamide. The inventors of the present invention found that by providing a polar aprotic solvent, a relatively high yield of the reaction products, in particular the hexafluorophosphate and / or the phosphorus trifluoride, is enabled.

[0049] Xi is selected from a group consisting of an alkali metal atom residue, a magnesium halogenide residue or a hydrogen residue. The alkali metal atom residue may be a lithium residue, a sodium residue or a potassium residue. The magnesium halogenide residue may be a magnesium fluoride residue, a magnesium chloride residue, a magnesium bromide residue or a magnesium iodide residue. If X3is an alkali metal atom residue or a magnesium halogenide residue, the R2-NX1-R3is a metal amide. If X3is a hydrogen residue, the R2-NX1-R3is a secondary amine.

[0050] The temperature may be a temperature in the range of 25 °C to 85 °C, in particular in the range of 30 °C to 80 °C, in particular in the range of 35 °C to 75 °C, in particular in the range of 40 °C to 70 °C, in particular in the range of 45 °C to 65 °C, in particular in the range of 50 °C to 60 °C.

[0051] In an embodiment of the invention the solvent is dichloromethane and the fluoride anion is provided for obtaining the phosphorus trifluoride. The inventors found that this combination is particularly effective when a selective reaction for obtaining the phosphorus trifluoride is desired. Selectivity and yield are relatively high when the temperature is in the range of 60 °C to 70 °C, in particular in the range of 63 °C to 67 °C.

[0052] In any case, the temperature may be maintained for at least 30 minutes, in particular for at least 1 hour, in particular for at least 2 hours, in particular for at least 3 hours, in particular for at least 4 hours, and for at most 72 hours, in particular for at most 48 hours, in particular for at most 24 hours, in particular for at most 12 hours, in particular for at most 8 hours.

[0053] In the method according to the invention steps a) to c), in particular steps b) and c), in particular step c), may be performed under inert atmosphere. The inert atmosphere may be provided by means of an inert gas. The inert gas may be contained in an inert gas mixture. The inert gas may be nitrogen gas, carbon dioxide gas, helium gas, neon gas or argon gas. The inert gas mixture may be a mixture of at least two of nitrogen gas, carbon dioxide gas, helium gas, neon gas and argon gas.

[0054] The mixture may be stirred during the adjusting of the mixture obtained in step b) to the temperature and the maintaining of this temperature according to step c) of the present invention.

[0055] The mixture obtained in step c) may be brought after step c) to a temperature in the range of 5 °C to less than 30 °C, in particular in the range of 10 °C to 25 °C, in particular in the range of 15 °C to 20 °C by cooling or heating. The cooling may be performed as an active cooling or as a passive cooling, i.e. by letting it cool down. The cooling may be performed under inert atmosphere. The heating may be performed as an active heating or as a passive heating, i.e. by letting it heat up. The heating may be performed under inert atmosphere. The hexafluorophosphate, the phosphorus trifluoride, the phosphorus trihalogenide, the phosphoric acid, the tertiary phosphite ester according to formula (I), the phosphoric acid triester according to formula (II), or the tertiary aminophosphine according to formula (III) may be obtained by purification of the hexafluorophosphate, the phosphorus trifluoride, the phosphorus trihalogenide, the phosphoric acid, the tertiary phosphite ester according to formula (I), the phosphoric acid triester according to formula (II), or the tertiary aminophosphine according to formula (III) from the mixture obtained in step c). The purification of the hexafluorophosphate, the phosphorus trifluoride, the phosphorus trihalogenide, the phosphoric acid, the tertiary phosphite ester according to formula (I), the phosphoric acid triester according to formula (II), or the tertiary aminophosphine according to formula (III) may be performed by distillation, extraction, precipitation, crystallization, sublimation or chromatography. The purification may be performed under inert atmosphere.

[0056] The invention will be explained in more detail with reference to the following embodiments:

[0057] Fig. 1 shows a schematic representation of the chemical synthesis of potassium hexafluorophosphate starting from white phosphorus in different solvents,

[0058] Fig. 2 shows a schematic representation of the chemical synthesis of hexafluorophosphate starting from white phosphorus and different fluoride sources,

[0059] Fig. 3 shows a schematic representation of the chemical synthesis of potassium hexafluorophosphate starting from white phosphorus and different oxidizing agents,

[0060] Fig. 4 shows a schematic representation of the chemical synthesis of potassium hexafluorophosphate starting from white phosphorus or red phosphorus,

[0061] Fig. 5 shows a schematic representation of the chemical synthesis of phosphorus trifluoride starting from white phosphorus,

[0062] Fig. 6 shows a schematic representation of the chemical synthesis of phosphorus trichloride starting from white phosphorus,

[0063] Fig. 7 shows a schematic representation of the chemical synthesis of phosphoric acid starting from white phosphorus, Fig. 8 shows a schematic representation of the chemical synthesis of aryl phosphites starting from white phosphorus,

[0064] Fig. 9 shows a schematic representation of the chemical synthesis of alkyl phosphites starting from white phosphorus,

[0065] Fig. 10 shows a schematic representation of the chemical synthesis of phosphoric acid triesters starting from white phosphorus,

[0066] Fig. 11 shows a schematic representation of the chemical synthesis of tertiary aminophosphines starting from white phosphorus,

[0067] Fig. 12 shows a schematic representation of the chemical synthesis of the Px(DDQ)yintermediate (1 :5 stoichiometry),

[0068] Fig. 13 shows a schematic representation of the chemical synthesis of the Px(DDQ)yintermediate (1 :3 stoichiometry),

[0069] Fig. 14 shows a31P{1H} NMR (162.0 MHz, CH2CI2, CeDe capillary) spectrum of all the products of a reaction of P4 with KF and DDQ in dichloromethane at 65 °C for 18 h and the distribution of these products,

[0070] Fig. 15 shows a qualitative19F{1H} NMR (367.6 MHz, CH3CN, CeDe capillary) spectrum of the products of a reaction of P4 with KF and DDQ in acetonitrile at 25 °C for 1 h and the distribution of these products,

[0071] Fig. 16 shows a31P{1H} NMR (162.0 MHz, CH3CN, CeDe capillary) spectrum of the products of a further reaction of P4 with KF and 8.0 equiv. of DDQ in acetonitrile at 65 °C for 18 h and the distribution of these products and Fig. 17 shows a31P{1H} NMR (162.0 MHz, CH3CN, CeDe capillary) spectrum of the products of a further reaction of P4 with KF and 20.0 equiv. of DDQ in acetonitrile at 65 °C for 18 h and the distribution of these products.

[0072] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equivalent (equiv.)) are mixed with 0.300 mmol of KF (17.4 mg, 7.50 equivalents (equiv.) per P atom) in 0.8 mL of an organic solvent solution containing 0.200 mmol of DDQ (45.5 mg, 5.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in the corresponding solvent, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio organic solvent / benzene is 9:1 . The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. A schematic representation of the chemical synthesis of hexafluorophosphate starting from white phosphorus in different solvents is shown in Fig. 1 . The results of the solvent screening are depicted in Table 1 .

[0073] Table 1 : Solvent screening

[0074] Molar

[0075] _ . . Dielectric Conversion Yield PF3 Yield KPFe . .

[0076] Solvent balance P constant K P4 [mol-%]a[mol-%] [mol-%]a. . ,

[0077] [mol-%]hb

[0078] Toluene 2.4 84 <1 <1 16

[0079] Diethyl ether 4.3 92 <1 <1 8

[0080] Chloroform04.8 60 <1 <1 68

[0081] Tetrahydrofuran 7.5 >99 <1 22 22

[0082] Dichloromethaned9.1 89 13 <1 13

[0083] Acetone021.0 >99 <1 27 41

[0084] Ethanol624.6 85 <1 <1 85

[0085] Acetonitrile 36.6 >99 <1 95 95

[0086] N'N~ 38.3 >99 <1 64 64 dimethylformamideaYield of KPFe and conversion of P4 were determined by quantitative31P{1H} NMR spectroscopy using TPPO as internal standard.bMolar balance refers to the total amount (mmol) of observed species divided by the initial amount (mmol) of phosphorus used in the reaction, expressed as percentage.

[0087] 0H3PO4 identified as the side product by qualitative31P{1H} NMR spectroscopy (5 = - 0.4 ppm, s)dPFswas identified as the major product by qualitative31P{1H} NMR spectroscopy (5 =104.6 ppm, quadruplet,1JP-F = 1400.9 Hz).eOP(OEt)3 was identified as the major product by qualitative31P NMR spectroscopy (5 = - 0.5 ppm, hept.3JP-H = 8.0 Hz).

[0088] Here and in the following, the molar balance can be calculated according to the following formula:

[0089] Molar balance 100

[0090] Where: m = number of observed species

[0091] [P]i = amount of substance i against the internal standard (mmol) [P]o= initial amount of phosphorus against the internal standard (typically 0.040 mmol, unless otherwise noted)

[0092] The presence of the reaction products KPFe and PF3 was determined by quantitative integration of31P{1H] NMR spectra. The yields of the reaction products KPFe and PF3 determined by NMR spectroscopy and related to the amount of white phosphorus used in each case are given in the columns "Yield KPFe [mol- %]" and "Yield PF3 [mol-%]", respectively.

[0093] The first optimization step was to find a suitable solvent for the reaction to be performed in. A selection of nine common laboratory solvents, covering most of the polarity range, was tested (see Table 1 ). Generally, a trend between the solvent dielectric constants, K, and the KPFe yields is noticeable. The reactions in the media with the lowest K values, from toluene to chloroform, returned almost no hexafluorophosphate product, while the KPFe yield gradually increases from tetrahydrofuran through to acetonitrile. This trend breaks down at DCM, where almost no KPFe was detected but instead the formation of phosphorus trifluoride (5 104.6 ppm, q,1JPF = 1400.9 Hz), and at ethanol, where other phosphorus compounds are observed rather than KPFe. Acetonitrile gave the best results with 90% yield KPFe, full conversion of P4 and no side products detected in both31P{1H} and19F{1H} NMR spectra. The reaction in A / , / \ / -dimethylformamide, the solvent with the highest K in Table 1 , also returned KPFe cleanly but less effectively than in acetonitrile. The latter was then chosen as the optimal solvent for the fluorination of white phosphorus to afford the PFe’ anion. fluoride source

[0094] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equiv.) are mixed with 0.300 mmol of the fluoride source (7.50 equiv. per P atom) in 0.8 mL of acetonitrile containing 0.200 mmol of DDQ (45.5 mg, 5.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in acetonitrile, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio acetonitrile / benzene is 9:1 . The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. A schematic representation of the chemical synthesis of hexafluorophosphate starting from white phosphorus and different fluoride sources is shown in Fig. 2. The results of the fluoride source screening are depicted in Table 2.

[0095] Table 2: Fluoride source screening

[0096] Entrysource Yield PFe- [mol-%]aYield PO2F2- [mol-%]aMolar balance P

[0097] [mol-%]b

[0098] 4 CsF 47 Traces 48

[0099] 5 NH4F 68 4 72

[0100] 6 NMe4F 92 6 98

[0101] 7 NEt3(HF)327 57 84

[0102] 8 KBF473 n.d. 73aYield of KPFe or KPO2F2 and conversion of P4 (>99% in all entries) were determined by quantitative31P{1H} NMR spectroscopy using TPPO as internal standard.bMolar balance refers to the total amount (mmol) of observed species divided by the initial amount (mmol) of phosphorus used in the reaction, expressed as percentage.

[0103] Abbreviation n.d. stands for “not detected”

[0104] A selection of different fluoride sources was used to study their possible influence on the reaction performance in terms of activity and selectivity. With the exception of KF, the alkali metal fluorides returned low to moderate yields of the corresponding PFe- salt (Table 2, entries 1 - 4). Moreover, excluding KF, the alkali fluorides afforded as well a species identified as PO2F2-. The species PO2F2- is a by-product commonly encountered during the hydrolysis of PFe-. Two simple ammonium fluoride salts were tested (entries 5 and 6) and with the non-protic NMe4F a high yield of PFe-, along with minor amounts of PO2F2-, was obtained. In contrast, the HF surrogate NEts(HF)3 gives PO2F2- as the major product (entry 7). The tetrafluoroborate ion could also be used as fluorinating agents, giving full conversion of P4 and a selective transformation to KPFe in 73% yield. Based on this results, the best fluoride source for the fluorination of white phosphorus to afford the PFe’ anion is KF. This salt not only returned KPFe in high yield and selectively, but it is also relatively cheap and easy to handle. oxidant

[0105] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equiv.) are mixed with 0.300 mmol of KF (17.4 mg, 7.50 equiv. per P atom) in 0.8 mL of acetonitrile containing 0.200 mmol of the oxidant (5.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in acetonitrile, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio acetonitrile / benzene is 9:1 . The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. A schematic representation of the chemical synthesis of hexafluorophosphate starting from white phosphorus and different oxidizing agents is shown in Fig. 3. The results of the oxidant screening are depicted in Table 3.

[0106] Table 3: Oxidant screening

[0107] Oxidant c Eo° r [Vi] Conversion Yield KPFe [mol-

[0108] Entry %1 [OX] vs. Fc / Fc+[mol-%]a 1a / oj aYield of KPFe and conversion of P4 were determined by quantitative31P{1H} NMR spectroscopy using TPPO as internal standard. Table 3 depicts a selection of the oxidizing agents used for the fluorination of white phosphorus to afford the PFe’ anion, where the standard oxidation potentials E° and the achieved yield of KPFe in each case are presented. The E° values correspond to those in acetonitrile and against the Fc / Fc+redox couple as E°(Fc / Fc+) = 0.00 V. The yield is apparently independent from the standard potential E° of the oxidizing agent, except within the electron-deficient p-quinone systems, where the yield continuously increases with the oxidation potential from chloranil to DDQ (entries 1 , 2 and 5). When looking at the oxidizing agents in Table 3, one common feature comes apparent: all the compounds have a quinone / quinonoid pi-system, which readily accepts one electron to form the aromatically stabilized semi quinone / semi quinonoid radical anion, as illustrated with DDQ, TCNQ and TCNE above. With this screening, the best oxidant for the fluorination of white phosphorus to yield the PFe’ anion is DDQ, but also TCNQ and TCNE are well-suited for such transformation.

[0109] Example 4: Chemical synthesis of hexafluorophosphate, phosphorus source screening

[0110] 0.40 mmol of white phosphorus or red phosphorus (12.4 mg, 1.00 equiv.) are mixed with 3.0 mmol of KF (174.3 mg, 7.50 equiv. per P atom) in 8.0 mL of acetonitrile containing 2.0 mmol of DDQ (454.0 mg, 5.00 equiv. per P atom). Additionally, 0.10 mmol of triphenylphosphine oxide (27.8 mg, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. A schematic representation of the chemical synthesis of hexafluorophosphate starting from white phosphorus or red phosphorus is shown in Fig. 4. The results are depicted in Table 4.

[0111] Table 4: Phosphorus source

[0112] Molar Yield Yield

[0113] Phosphorus balance

[0114] Entry Conversion [mol-%] KPFe PO2F2- allotrope P [mol-

[0115] [mol-%]a[mol-%]a

[0116] 1 White > 99a89 <1

[0117] 2 Red 50c42 9 51aYield of KPFe or KPO2F2 and conversion of P4 were determined by quantitative31P{1H} NMR spectroscopy using TPPO as internal standard.bMolar balance refers to the total amount (mmol) of observed species divided by the initial amount (mmol) of phosphorus used in the reaction, expressed as percentage.cConversion of red phosphorus was determined gravimetrically. The reaction precipitate was washed with acetonitrile (3 x 4 mL), water (3 x 5 mL) and ethanol (3 x 4 mL). The resulting brick red residue, unreacted red P, was dried under reduced pressure and weighted.

[0118] One common problem with the P4 chemistry, among others, is the formation of very insoluble polyphosphorus species, structurally related to the red allotrope of phosphorus. In this regard, the inventors wondered if red phosphorus, hypothetically formed in the reaction from white phosphorus, would be prone to fluorination under the reaction conditions. When using red phosphorus instead of white phosphorus as phosphorus source, the reaction returned 42% of the desired PFe’ anion, along with its hydrolysis side product PO2F2- (entry 2). Owing its readily solubility in non-polar solvents and its intrinsic reactive nature, white phosphorus is a better phosphorus source than red phosphorus. Nevertheless, the methodology here presented is also suitable to fluorinate the less reactive red phosphorus. This represents an advantage in terms of safety and the possibility of using molecular oxygen as the terminal oxidant. trifluoride, a mixture of a

[0119] Embodiment 1 :

[0120] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equiv.) are mixed with 0.150 mmol of KF (8.7 mg, 3.75 equiv. per P atom) in 0.8 mL of dichloromethane containing 0.120 mmol of DDQ (27.2 mg, 3.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in acetonitrile, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio dichloromethane / acetonitrile / benzene is 8:1 :1. The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. PF3 can be easily separated from the by-products by condensation of the reaction mixture into a cooled trap (cooled by liquid nitrogen) under vacuum (10-3mbar). The condensate still contains a mixture of solvents (acetonitrile, dichloromethane and benzene). PF3 is then isolated by fractional distillation under ambient pressure. A schematic representation of the chemical synthesis of phosphorus trifluoride starting from white phosphorus is shown in Fig. 5.

[0121] The reaction in dichloromethane (DCM) returned the selective formation of phosphorus trifluoride (5 104.6 ppm, q,1JPF = 1400.9 Hz) in 13% yield and 89% conversion of P4, as determined by quantitative31P{1H} NMR spectroscopy. The low molar balance of this reaction could be explained in terms of the volatility of PF3, which is a gas under normal conditions (boiling point: -101.8 °C). This means that only a fraction of PF3 is dissolved in dichloromethane, while the rest remains in the headspace of the NMR tube. PF3 is usually synthesized from phosphorus trichloride (PCI3), by treating it with a metal or main group fluoride (e.g., NaF, ZnF2 or AsFs). With the method presented here, PF3 can be obtained directly from P4, circumventing the use of elemental fluorine gas, chlorine gas or hydrogen fluoride. The adjustment of the reaction stoichiometry (3 equiv. of F’ and DDQ) and the solvent (dichloromethane) can avoid further oxidation / fluorination of PF3 to PFs or PF6-.

[0122] The31P{1H} NMR (162.0 MHz, CH2CI2, CeDe capillary) spectrum of the reaction mixture of P4 with KF and DDQ in dichloromethane after the reaction is shown in Fig. 14. Triphenylphosphane oxide (TPPO) was used as an internal standard. The signal at 5 = 136.5 ppm is assigned to the hypothetical reaction intermediate P(DDQ)3. In addition, some unreacted P4 is identified by a signal at 5 = -523.1 ppm.

[0123] Embodiment 2:

[0124] Phosphorus trifluoride can also be prepared when another solvent than dichloromethane, such as acetonitrile, is used. When white phosphorus (P4 stock solution in benzene) is mixed with KF and DDQ (5.00 equiv. per P atom) in acetonitrile and reacted at 25 °C for 1 h, PF3 was identified as the major species in the reaction mixture after the reaction. Analysis was performed by19F{1H} NMR (367.6 MHz, CH3CN, CeDe capillary) spectroscopy. The spectrum of the reaction mixture after the reaction is shown in Fig. 15. The spectrum clearly reveals that obtaining PFs.is not restricted to dichloromethane as the solvent and that the solvent dichloromethane is not necessary for obtaining PF3.

[0125] Embodiment 3:

[0126] The fact that obtaining PFs.is not restricted to dichloromethane is also evident when performing the reaction of P4, KF and DDQ at 65 °C for 18 h in acetonitrile as the solvent. In the present embodiment, a phosphorus to oxidant ratio of 1 :8 has been used. The ratio relate to equiv. P4 against equiv. DDQ, meaning 2.00 equivalents of oxidant per P atom. The reaction mixture after the reaction was analyzed by means of31P{1H} NMR spectroscopy. This revealed a considerable amount of PF3 (8% according to qualitative31P NMR integration) relative to the internal standard TPPO along with unreacted P4 and hexafluorophosphate. The spectrum is shown in Fig. 16.

[0127] Embodiment 4:

[0128] If the same reaction is performed with a phosphorus to oxidant ratio of 1 :20 (5.00 equiv. of oxidant per P atom), analysis by means of31P{1H} NMR spectroscopy revealed that the reaction resulted in the generation of KPFe and no or nearly no PF3. The spectrum is shown in Fig. 17.

[0129] By choosing appropriate solvent, temperature and stoichiometry it is possible to tune the selectivity of the fluorination / oxidation such that either the phosphorus trifluoride or the mixture of the hexafluorophosphate and the phosphorus trifluoride or the hexafluorophosphate is obtained. Furthermore, it is possible to influence in this way the ratio of the hexafluorophosphate and the phosphorus trifluoride in the mixture. trichloride

[0130] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equiv.) are mixed with 0.150 mmol of HCI (1 ,4-dioxane solution, 4.0 M, 37.5 pL, 3.75 equiv. per P atom) in 0.8 mL of acetonitrile containing 0.120 mmol of DDQ (27.2 mg, 3.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in acetonitrile, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio acetonitrile / benzene is 9:1 . The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. PCI3 can be easily separated from the by-products by condensation of the reaction mixture into a cooled trap (cooled by liquid nitrogen) under vacuum (10’3mbar). The condensate still contains a mixture of solvents (acetonitrile, 1 ,4-dioxane and benzene). PCI3 is then isolated by fractional distillation under ambient pressure. A schematic representation of the chemical synthesis of phosphorus trichloride starting from white phosphorus is shown in Fig. 6.

[0131] The functionalization of P4 with other halides than fluoride was performed by using anhydrous HCI as chlorine source. Unlike the transformations with KF, that typically proceed rather cleanly, the chlorination reaction is less selective. Nevertheless, the formation of phosphorus trichloride (5 - 220.0 ppm, s) was identified by means of qualitative31P{1H} NMR spectroscopy, thus confirming the potential of extending the reaction scope to heavier halides. PCI3 is synthesized by treating P4 with chlorine gas. With the method presented here, PCI3 can be obtained avoiding the use of elemental chlorine gas.

[0132] Example 7: Chemical synthesis of phosphoric acid

[0133] 1.0 mmol of white phosphorus (123.9 mg, 1.00 equiv.) is mixed with 20.0 mmol of water (360.0 mg, 5.00 equiv. per P atom) in 50.0 mL dimethyl sulfoxide or acetonitrile containing 20.0 mmol of DDQ (4.5 g, 5.00 equiv. per P atom). Additionally, 1.0 mmol of triphenylphosphine oxide (278.3 mg, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. Phosphoric acid can be isolated by liquid-liquid extraction (water / chloroform) and recrystallization of phosphoric acid as the hydrate H3PO4-H2O from the aqueous phase, according to the method from Weber & King (Inorg Synth I, 1939, Chapter s, pp 101 -103, Print ISBN:9780470131602, Online ISBN:9780470132326). A schematic representation of the chemical synthesis of phosphoric acid starting from white phosphorus is shown in Fig. 7.

[0134] Elemental white phosphorus does not react with water. Indeed, the simplest way to store this highly reactive and pyrophoric substance is in water. The inventors attempted to apply the oxidative transformation discovered by them for the reaction of P4 with water, as safe oxygen source rather than molecular oxygen. The reaction takes place effectively both in dimethyl sulfoxide or acetonitrile, returning H3PO4 with more than 95% yield as determined by quantitative31P{1H} NMR spectroscopy. In the so called “dry process”, H3PO4 is synthesized by burning P4 with air, followed by treatment of the resulting phosphorus pentoxide with water. With the method presented here, H3PO4 can be obtained avoiding the hazardous combination of P4 and O2.

[0135] Example 8: Chemical synthesis of triaryl phosphite esters

[0136] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equiv.) are mixed with 0.150 mmol of an aryl alcohol (3.75 equiv. per P atom) in 0.8 mL of acetonitrile containing 0.120 mmol of DDQ (27.2 mg, 3.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in acetonitrile, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio acetonitrile / benzene is 9:1 . The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. The corresponding triaryl phosphite esters, P(OAr)3, can be isolated by fractional distillation under reduced pressure (10’3mbar) from the crude reaction mixture. A schematic representation of the chemical synthesis of triaryl phosphite esters starting from white phosphorus is shown in Fig. 8.

[0137] The functionalization of P4 with aromatic alcohols was attempted. The triaryl phosphite esters can be obtained in variable yields depending on the electronic and steric nature of the aromatic substituents. The best result was observed for phenol as nucleophile, returning almost 60% yield of the corresponding product as determined by quantitative31P{1H} NMR spectroscopy (5 129.0 ppm, s). Triaryl phosphite esters are usually synthesized from phosphorus trichloride (PCI3), by treating it with an aromatic alcohol and base (e.g. pyridine or triethylamine). With the method presented here, P(OAr)3 can be obtained directly from P4, circumventing the use of PCI3 and additional base. The adjustment of the reaction stoichiometry (3 equiv. of ArOH and DDQ) is important to overcome further oxidation of the P(lll) compound to the respective phosphoric acid triester. Nevertheless, a mixture of triaryl phosphite esters and the respective phosphoric acid triarylester was always obtained.

[0138] Example 9: Chemical synthesis of trialkyl phosphite esters

[0139] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equiv.) are mixed with 0.150 mmol of an alkyl alcohol (3.75 equiv. per P atom) in 0.8 mL of acetonitrile containing 0.120 mmol of DDQ (27.2 mg, 3.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in acetonitrile, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio acetonitrile / benzene is 9:1 . The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. The corresponding trialkyl phosphite esters, P(OR)3, can be isolated by fractional distillation under reduced pressure (10-3mbar) from the crude reaction mixture. A schematic representation of the chemical synthesis of trialkyl phosphite esters starting from white phosphorus is shown in Fig. 9.

[0140] Unlike the transformations with ArOH, that typically produced amenable amounts of P(OAr)3, the reaction with aliphatic alcohols is less effective. Nevertheless, when using for example ethanol, the formation of triethyl phosphite ester (5 135.0 ppm, s) was identified by means of qualitative31P{1H} NMR spectroscopy. This illustrates the potential of extending the reaction scope to aliphatic alcohols.

[0141] Example 10: Chemical synthesis of phosphoric acid triesters

[0142] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equiv.) are mixed with 0.300 mmol of an alkyl alcohol (7.50 equiv. per P atom) in 0.8 mL of acetonitrile containing 0.200 mmol of DDQ (45.4 mg, 5.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in acetonitrile, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio acetonitrile / benzene is 9:1 . The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. The corresponding phosphoric acid triesters, (O)P(OR')3, can be isolated by fractional distillation under reduced pressure (10-3mbar) from the crude reaction mixture. A schematic representation of the chemical synthesis of phosphoric acid triesters starting from white phosphorus is shown in Fig. 10.

[0143] The phosphoric acid triesters can be obtained in variable yields depending on the electronic and steric nature of the alcohols used. The best result was observed for ethanol as nucleophile, returning 40% yield of phosphoric acid triethyl ester as determined by quantitative31P{1H} NMR spectroscopy. Phosphoric acid triesters are usually synthesized from either phosphorus trichloride (PCI3) or phosphoryl chloride (OPCh). With the method presented here, OP(OR')3 can be obtained directly from P4, circumventing the use of PC I3, OPCh and the addition of base. The adjustment of the reaction stoichiometry (5 equiv. of R'OH and DDQ) is important to force the fully oxidation of the phosphorus atom. Nevertheless, a mixture of phosphoric acid triesters and the respective tertiary phosphite esters was always obtained. The selectivity with alcohols is lower than the one afforded with fluoride anions or water.

[0144] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL,

[0145] 1.00 equiv.) are mixed with 0.150 mmol of a compound R2-NX1-R3(3.75 equiv. per

[0146] P atom) in 0.8 mL of acetonitrile containing 0.120 mmol of DDQ (27.2 mg, 3.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in acetonitrile, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio acetonitrile / benzene is 9:1 . The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of

[0147] 31P{1H} NMR spectra using TPPO as internal standard. The corresponding tertiary aminophosphines, P(NR2R3)s, can be isolated by fractional distillation under reduced pressure (10’3mbar) from the crude reaction mixture. A schematic representation of the chemical synthesis of tertiary aminophosphines starting from white phosphorus is shown in Fig. 11.

[0148] The functionalization of P4 with A / -nucleophiles of the type R2-NX1-R3was performed. For example, when using diisopropylamine, 70% of the white phosphorus was consumed, forming 51 % of the tertiary aminophosphine P(N'Pr2)3 in a clean reaction, as determined by31P{1H} NMR spectroscopy. The uneven molar balance is still not clear, since the31P{1H} NMR exhibits only three resonances: the starting material ( 5 -524.5 ppm, s), the internal standard (5 28.5 ppm, s) and the product P(N'Pr2)3 (5 147.5 ppm, s). Nevertheless, this result confirms the potential of extending the reaction scope to other A / -nucleophiles. Example 12: Chemical synthesis of the Px(DDQ)v intermediate by reaction of

[0149] P4 and DDQ (5 equiv. per P atom) in dimethylformamide

[0150] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equiv.) are mixed with 0.8 mL of A / , / \ / -dimethylformamide containing 0.200 mmol of DDQ (45.4 mg, 5.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in A / , / \ / -dimethylformamide, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio A / , / \ / -dimethylformamide / benzene is 9:1. The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. A schematic representation of the chemical synthesis of the Px(DDQ)yintermediate (1 :5 stoichiometry) is shown in Fig. 12.

[0151] The31P{1H} NMR spectrum of the reaction mixture shows that the starting material is fully consumed (no signal of P4 is detected). A set of several singlets is observed at around 5 -12.0 ppm, which represents >95% of the initial amount of P atoms used in the reaction according to quantitative31P{1H} NMR integration. Based on the chemical shift for these signals and the reaction stoichiometry, the formed species are likely phosphorus(V) compounds bearing reduced forms of DDQ ( / .e. DDQ" and DDQ2') as substituents.

[0152] Example 13: Chemical synthesis of the Px(DDQ)v intermediate by reaction of P4 and DDQ (3 equiv. per P atom) in acetonitrile

[0153] 0.010 mmol of white phosphorus (P4 stock solution in benzene, 0.1 M, 100 pL, 1.00 equiv.) are mixed with 0.8 mL of acetonitrile containing 0.120 mmol of DDQ (27.3 mg, 3.00 equiv. per P atom). Additionally, 0.010 mmol of triphenylphosphine oxide (TPPO stock solution in acetonitrile, 0.1 M, 100 pL, 0.25 equiv. per P atom) are added as internal standard for31P{1H} NMR quantification. The volumetric ratio acetonitrile / benzene is 9:1 . The mixture is heated to 65 °C and incubated for 18 hours. Conversion and yield were determined by quantitative integration of31P{1H} NMR spectra using TPPO as internal standard. A schematic representation of the chemical synthesis of the Px(DDQ)yintermediate (1 :3 stoichiometry) is shown in Fig. 13.

[0154] The31P{1H} NMR of the reaction mixture shows that the starting material is fully consumed (no signal of P4 is detected). A set of several singlets is observed at around 5 137.0 ppm. Based on the chemical shift for these signals and the reaction stoichiometry, the formed species are likely phosphorus(lll) compounds bearing reduced forms of DDQ ( / .e. DDQ" and DDQ2') as substituents.

[0155] In any of the above examples the method according to the invention can be performed in an inert atmosphere. It has been found that this results in slightly higher yields than without inert atmosphere.

Claims

Claims1. A method for the generation of either- a phosphorus trifluoride or a mixture of a hexafluorophosphate and a phosphorus trifluoride or a hexafluorophosphate,- a phosphorus trihalogenide, wherein the phosphorus trihalogenide is a phosphorus trichloride, a phosphorus tribromide or a phosphorus triiodide,- phosphoric acid,- a mixture of a tertiary phosphite ester according to formula (I) and a phosphoric acid triester according to formula (II), or a tertiary aminophosphine according to formula (III),wherein R1, R2and R3are each selected independently from each other from a group consisting of alkyl, aryl, heterocyclyl and heteroaryl, wherein the method comprises the following steps:a) providing an elemental phosphorus, a solvent, an oxidant having a pi- conjugated system and at least two and at most eight electron-withdrawing groups selected from chlorine, bromine, cyano and oxo, and either- a fluoride anion for obtaining the phosphorus trifluoride or the mixture of the hexafluorophosphate and the phosphorus trifluoride or the hexafluorophosphate,- a chloride anion for obtaining the phosphorus trichloride, a bromide anion for obtaining the phosphorus tribromide, a iodide anion for obtaining the phosphorus triiodide,- water for obtaining the phosphoric acid,- a compound R1-OH for obtaining the mixture of the tertiary phosphite ester according to formula (I) and the phosphoric acid triester according to formula (II), or- a compound R2-NX1-R3for obtaining the tertiary aminophosphine according to formula (III), wherein Xi is selected from a group consisting of an alkali metal atom residue, a magnesium halogenide residue or a hydrogen residue, b) mixing the elemental phosphorus, the oxidant, and either the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1-OH or the compound R2-NX1-R3in the solvent andc) adjusting a mixture obtained in step b) to a temperature in the range of20 °C to 95 °C and maintaining the temperature, wherein the oxidant is a substituted para-quinone according to formula (IV), a substituted tetracyanoquinodimethane according to formula (V) or a tetracyanoethylene according to formula (VI),wherein R4, R5, R6and R7are each selected independently from each other from a group consisting of chlorine, bromine, cyano and hydrogen.

2. Method according to claim 1 , wherein the elemental phosphorus is white phosphorus or red phosphorus.

3. Method according to claim 1 or 2, wherein the oxidant has a molar mass of at least 100 g / mol and at most 750 g / mol, in particular of at least 125 g / mol and at most 250 g / mol.

4. Method according to any of the preceding claims, wherein R4and R6are chlorine and R5and R7are cyano in the substituted para-quinone according to formula (IV).

5. Method according to any of the preceding claims, wherein an oxidizing agent- is added to the elemental phosphorus, the solvent, the oxidant or either the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1-OH or the compound R2-NX1-R3before step b) or- is mixed with the elemental phosphorus, the solvent, the oxidant and either the fluoride anion, the chloride anion, the bromide anion, the iodide anion, the water, the compound R1-OH or the compound R2-NX1-R3during step b) or- is added to the mixture obtained in step b) between step b) and step c) and / or during or after step c).

6. Method according to any of the preceding claims, wherein the alkyl is C1-6 alkyl or C5-10 cycloalkyl, and / or wherein the aryl is C6-10 aryl, and / or wherein the heteroaryl is 5- to 10-membered heteroaryl, and / or wherein the heterocyclyl is 5- to 10-membered heterocyclyl, wherein the C1-6 alkyl, the C5-10 cycloalkyl, the C6-10 aryl, the 5- to 10-membered heterocyclyl and the 5- to 10-membered heteroaryl are optionally substituted by halogen, C1-6 alkyl, C6-10 aryl, C5-10 cycloalkyl, 5- to 10-membered heterocyclyl, 5- to 10- membered heteroaryl, OR', COR', COOR', CONR'2 or NR'2, wherein R' is independently from each other selected from the group consisting of H, C1-6 alkyl, C6-10 aryl and C5-10 cycloalkyl.

7. Method according to any of the preceding claims, wherein the solvent is an organic solvent or a mixture of at least two organic solvents.

8. Method according to claim 7, wherein the organic solvent is a polar aprotic solvent.

9. Method according to any of the preceding claims, wherein the temperature is a temperature in the range of 25 °C to 85 °C, in particular in the range of 50 °C to 60 °C.

10. Method according to claim 8, wherein the solvent is dichloromethane and the fluoride anion is provided for obtaining the phosphorus trifluoride.11 . Method according to claim 10, wherein the temperature is in the range of 60 °C to 70 °C, in particular in the range of 63 °C to 67 °C.

12. Method according to any of the preceding claims, wherein the maintaining of the temperature is for at least 30 minutes, in particular for at least2 hours, and for at most 168 hours, in particular for at most 72 hours.

13. Method according to any of the preceding claims, wherein the mixture obtained in step b) is stirred during the adjusting and the maintaining.

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