MXPA06004621A - Use of azeotropically dried nickel(ii) halogenides - Google Patents

Abstract

The invention relates to a method for the production of nickel(0) phosphorous ligand complexes containing at least one nickel(0) central atom and at least one ligand containing phosphorus. One nickel (II) halognenide dried by azeotropic distillation is reduced in the presence of at least one ligand containing phosphorous.

Description

USE OF NICKEL HALOGENURQS (II) DRIED BY THE AZEOTROPIC METHOD Description The present invention relates to a process for the preparation of nickel (0) complexes with phosphorus ligands. Another object of the present invention are mixtures containing the complexes of nickel (0) with phosphorus ligands, obtainable by this process, as well as their use in the hydrocyanation of alkenes or, where appropriate, the isomerization of unsaturated nitriles.

Nickel complexes with phosphorus ligands are suitable catalysts for alkene hydrocyanates. Thus, for example, nickel complexes with monodentate phosphites are known, which catalyze the hydrocyanation of butadiene for the preparation of a mixture consisting of isomeric pentenonitriles. These catalysts are equally suitable in a subsequent isomerization of 2-methyl-3-butenonitrile to transform it into linear 3-pentenenitrile and the hydrocyanation of 3-pentenenitrile to transform it in adiponitrile, an important intermediate product in the manufacture of nylon.

US 3,903,120 describes the preparation of zero-valent nickel complexes with monodentate phosphite ligands from nickel powder. The ligands containing phosphorus have, in that process, the general formula PZ3, in which Z corresponds to an alkyl, alkoxy or aryloxy group. In this process, finely distributed elemental nickel is used. Also, the transformation is preferably carried out in the presence of a solvent containing nitrite and in the presence of an excess of ligand.

US 3,846,461 describes a process for the preparation of zero-valent nickel complexes with triorganophosphite ligands by reacting triorganophosphite compounds with nickel chloride in the presence of a finely distributed reducing metal that is more electropositive than nickel. The transformation according to US 3,846,461 is carried out in the presence of a promoter selected from the group consisting of NH3, NH4X, Zn (NH3) 2X2 and mixtures of NH4X and ZnX2, wherein X corresponds to a halogenide.

New developments have shown that it is advantageous to apply complexes of nickel with chelate ligands (muitidentate ligands) in the hydrocyanation of nickel complexes alkenes, since with them both greater activities and higher selectivities can be achieved when the resting time is increased. The processes described above of the state of the art are not suitable for preparing nickel complexes with chelate ligands. However, it is also known from the prior art methods that enable the preparation of nickel complexes with chelate ligands.

US 5,523,453 describes a process for the preparation of nickel-containing hydrocyanation catalysts containing bidentate phosphorus ligands. The preparation of these complexes is carried out starting from soluble complexes of nickel (0) by transcompletion with chelate ligands. The starting compounds are Ni (COD) 2 u (oTTP) 2Ni (C2H4) (COD = 1.5 cyclooctadiene; oTTP = P (0-ortho-C3H4CH3) 3). This process is expensive because the preparation of the nickel starting compounds is expensive.

Alternatively, it is possible to prepare nickel (0) complexes by reduction starting from nickel compounds and bivalent chelate ligands.

When this method is applied, it is usual to work with elevated temperatures, so that the thermally labile ligands within the complex eventually decompose.

US 2003/0100442 Al discloses a process for the preparation of a nickel complex (0) - chelate, in which nickel chloride is reduced, in the presence of a chelate ligand and a solvent containing nitrile, using a metal that is more electropositive than nickel, in particular zinc or iron. In order to achieve high space-time performance, an excess of nickel salt is used, which after the complexation has to be separated again. The process is usually carried out with nickel chloride hydrate, which can lead, in particular, if ligands are used which are unstable before hydrolysis, to which they decompose. When working with anhydrous nickel chloride, in particular, when using ligands that are unstable against hydrolysis, it is essential, according to US 2003/0100442 Al, the nickel chloride is dried as a first step according to a special process, in which very small particles with large surface area and therefore with high reactivity are obtained. A disadvantage of the method resides particularly in the fact that the fine powder of nickel chloride, obtained by spray drying, is carcinogenic. Another disadvantage of this method is that it usually works with high reaction temperatures, which can lead to the decomposition of the ligands or the complex, especially when the ligands are unstable with respect to temperature. It is also inconvenient that you have to work with an excess of reagents, in order to obtain yielding reaction degrees. These excesses have to be eliminated, once the reaction is finished, at a high cost, and eventually be returned.

GB 1 000 477 and BE 621 207 relate to processes for the preparation of nickel (0) complexes by reduction of nickel (II) compounds, using phosphorus-containing ligands.

Accordingly, the object of the present invention was to create a process for preparing nickel (0) complexes with phosphorus ligands which substantially avoids the previously described drawbacks of the state of the art. To this end, a source of anhydrous nickel should be used in particular, so that ligands which are unstable against hydrolysis are not decomposed during complexation. In addition, it is intended that the reaction conditions are preferably with due care, so that unstable ligands do not decompose against the temperature and the resulting complexes. Also, the method according to the invention should preferably enable not to apply an excess of reagents, or only a small excess, so that it is not necessary, as far as possible, to separate these substances once the complex has been prepared. The procedure must also be appropriate for preparing nickel (0) complexes with phosphorus ligands, by applying chelate ligands.

According to the invention, this object is achieved by a process for the preparation of a nickel (0) complex with phosphorus ligands, which contains at least one central nickel atom and at least one ligand containing phosphorus.

Azeotropic distillation In the azeotropic distillation a nickel (II) halide with water content is used. The nickel halide (II) with water content is a nickel halide selected from the group of nickel chloride, nickel bromide and nickel iodide, containing at least 2% by weight of water. Examples thereof are nickel chloride dihydrate, nickel chloride hexahydrate, an aqueous solution of nickel chloride, nickel bromide trihydrate, an aqueous solution of nickel bromide, nickel iodide hydrates or an aqueous solution of nickel iodide. In the case of nickel chloride, nickel chloride hexahydrate or an aqueous solution of nickel chloride are preferably used. in the case of nickel bromide and nickel iodide preferably the aqueous solutions are used. Of special preference is an aqueous solution of nickel chloride.

In the case of an aqueous solution the concentration of the nickel (II) halide in water is not critical per se.

A proportion of the nickel halide was advantageous (II) of the total weight of said nickel (II) halide and water of at least 0.01% by weight, preferably at least 0.1% by weight, especially preferred at least 0.25% by weight, more preferably at least 0.5% by weight. A proportion of the nickel halide was advantageous (II) and water in the range of at most 80% by weight, preferably at most 60% by weight, especially preferred at most 40% by weight. For practical reasons it is advantageous not to exceed a proportion of nickel halide in the mixture of nickel halide and water, from which a solution results in the given conditions of temperature and pressure. In the case of an aqueous solution of nickel chloride, therefore it is advantageous for practical reasons, in the case of room temperature opt for a proportion of nickel halide of the total weight of nickel chloride and water of maximum 31% in weigh. In the case of higher temperatures, corresponding higher concentrations resulting from the solubility of nickel chloride in water can be chosen.

The nickel halide (II) with water content, prior to reduction, is dried by azeotropic distillation. In a preferred embodiment of the present invention, the azeotropic distillation is a process for the elimination of the water of the corresponding nickel halide (II), where the mixture is added with diluent, whose boiling point in the case of a non-azeotropic formation of the aforementioned solvent with water under the pressure conditions of the distillation indicated below, it is higher than the boiling point of water, which at that boiling point of water appears liquid or which forms an azeotrope or heteroazeotrope with water under the conditions of pressure and The temperature of the distillation indicated below, and the mixture containing the nickel halide (II) containing water and the dilution agent is distilled by separating the water or said azeotrope or the aforementioned heterozeotrope from this mixture and obtaining the an anhydrous mixture containing nickel (II) halide and said dilution agent.

The starting mixture may contain, in addition to the nickel halide (II) with water content, other components, such as ionic or nonionic, organic or inorganic compounds, especially those which can be mixed homogeneously in one phase with the starting mixture or which can dissolve in the starting mixture.

According to the invention, nickel halide is mixed (II) with water content, with a diluent, whose boiling point under the pressure conditions of the distillation, is higher than the boiling point of the water and at this boiling point the water appears liquid.

The pressure conditions for the subsequent distillation are not critical per se. The pressures of at least 10"4 MPa, preferably of at least 10" 3 MPa, especially of at least 5 * 10"3, were advantageous. The pressures of a maximum of 1 MPa, preferably a maximum of 5 * 10_1, were advantageous. MPa, especially at most 1.5 * 10"1 MPa.

In relation to the pressure conditions and the composition of the mixture to be distilled, the distillation temperature is then regulated. With this temperature the diluent preferably presents liquid. In the sense of the present invention, the term "diluent" is understood to mean both a single diluent and also a mixture of such diluents, wherein in the case of such a mixture, the mentioned physical properties refer to this mixture. In addition, the diluent preferably has such conditions of pressure and temperature, a boiling point, which in the case of the non-azeotropic formation of the diluent with water, is greater than the boiling point of the water, preferably at least 5 ° C, especially at least 20 ° C C, and preferably at most 200 ° C, especially at most 100 ° C.

In a special embodiment, diluent can be used which form an azeotrope or heteroazeotrope with water. The amount of diluent with respect to the amount of water in the mixture is not critical in itself. Advantageously, a greater amount of liquid diluent than that corresponding to the amounts to be separated by distillation should be used by the azeotropes, so that an excess of diluent remains as residual product.

If diluents are used that do not form an azeotrope with water, the amount of diluent with respect to the amount of water in the mixture is not critical per se.

The diluent used there is especially selected from the group consisting of organic nitriles, aromatic hydrocarbons, aliphatic hydrocarbons and mixtures of the aforementioned diluents. In respect of organic nitriles are preferably used acetonitrile, propionitrile, n-butyronitrile, n-valeronitrile, cyanocyclopropane, acrylonitrile, crotonitrile, allyl cyanide, cis-2-pentenenitrile, trans-2-pentenenitrile, cis-3-pentenenitrile, trans-3-pentenenitrile , 4-pentenenitrile, 2-methyl-3-butenonitrile, Z-2-methyl-2-butenonitrile, E-2-methyl-2-butenonitrile, ethylsuccinitrile, adiponitrile, methylglutarnitrile or mixtures thereof. With respect to the aromatic hydrocarbons, benzene, toluene, o-xylene, m-xylene, p-xylene or mixtures thereof can preferably be used. The aliphatic hydrocarbons may preferably be selected from the group of linear or branched aliphatic hydrocarbons, especially preferably from the group of cycloaliphatic substances, such as cyclohexane or methylcyclohexane, or mixtures thereof. Particular preference is given to using as solvents cis-3-pentenenitrile, trans-3-pentenenitrile, Adiponitrile, methylglutarnitrile or mixtures thereof.

If an organic nitrile is used as a diluent, or mixtures containing at least one organic nitrile, it was advantageous to fix the amount of diluent in such a way that in the finished mixture the proportion of the Nickel (II) halide in the total sum of the weight of nickel halide (II) and the diluent are at least 0.05% by weight, preferably at least 0.5% by weight, especially preferred at least 1% in weigh.

If an organic nitrile is used as diluent, or mixtures containing at least one organic nitrile, it was advantageous to fix the amount of diluent in such a way that in the finished mixture the proportion of the nickel halide (II) in the total sum of the weight of nickel halide (II) and the diluent are at most 50% by weight, preferably at most 30% by weight, especially preferred at most 20% by weight.

According to the invention, the mixture is distilled with the nickel halide (II) containing water and the diluent, separating the water from this mixture and obtaining an anhydrous mixture containing nickel halide (II) and said diluent. In a preferred embodiment, the mixture is first prepared and then the distillation is carried out. In a further preferred embodiment, the nickel halide with water content, especially preferably the aqueous solution of the nitrile halide, is gradually added to the diluent in boiling during distillation. Thus, the formation of a fatty solid difficult to handle technically in the process can be avoided to a greater degree.

In the case of pentenonitrile as a diluent, distillation with a pressure of not more than 200 kPa, preferably of not more than 100 kPa, in particular of not more than 50 kPa, especially preferably of not more than 20 kPa, can advantageously be carried out.

In the case of pentenonitrile as a diluent, distillation can advantageously be carried out with a pressure of at least 1 kPa, preferably of at least 5 kPa, especially preferred of at least 10 kPa.

The distillation can advantageously be carried out by evaporation in a single step, preferably by distillation by fractionation in one or more, such as 2 or 3 devices, of distillation. The usual devices for distillation are included, as indicated for example in: Kirk-Othmer, Encyclopedia of Chemical Technology, 3. Ed., Vol. 7, John Wiley & Sons, New York, 1979, page 870-881, as columns of screened funds, columns of vaulted backgrounds, columns of garrison, columns of filling bodies, columns with lateral exit or columns with partition wall.

The distillation can be carried out discontinuously.

The distillation can be carried out continuously.

Ligands In the process according to the invention for the preparation of nickel (0) complexes with phosphorus ligands containing at least one central nickel atom (0) and at least one ligand with phosphorus content, is characterized in that the nickel halide (II) dried by azeotropic distillation is reduced in the presence of at least one ligand with phosphorus content.

In the process according to the invention, the phosphorus-containing ligands are preferably selected from the group consisting of phosphines, phosphites, phosphinites and phosphonites.

These phosphorus-containing ligands preferably have the formula I: P (XaRx) (X2R2) (X3R3) (I) By compound I is understood, in the sense given in the present invention, an individual compound or a mixture of various compounds of the above formula.

According to the invention, X1, X2, X3 are, independently of one another, oxygen or individual compound. In case all the groups X1, X2 and X3 represent individual compounds, the compound I represents a phosphine of the formula P (R1R2R3), with the meanings given in this description for R1, R2 and R3.

In case two of the groups Xa, X2, X3 represent individual compounds and one represents oxygen, compound I represents a phosphinite of the formula P (ORx) (R2) (R3) or P (RX) (OR2) (OR3) ) or P (R1) (R2) (OR3) with the meanings given below for R1, R2 and R3.

In case one of the groups X1, X2 and X3 represents individual compounds and two represent oxygen, the compound I represents a phosphonite of the formula P (ORx) (OR2) (R3) or P (RX) (OR2) (OR3) or P (ORa) (R2) (OR3) with the meanings given in this description for R1, R2 and RJ In a preferred embodiment, all groups X1, X2, X3 should represent oxygen, so that compound I conveniently represents a phosphite of the formula P (OR1) (OR2) (OR3) with the meanings given below. for R1, R2 and R3.

According to the invention, R1, R2 and R3 represent, independently of one another, identical or different organic radicals. As R.sub.1, R.sub.2 and R.sub.3, independently of one another, alkyl radicals, preferably having 1 to 10 carbon atoms, such as methyl, ethyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, aryl groups, such as phenyl, o-tolyl, m-tolyl, p-tolyl, 1-naphthyl, 2-naphthyl, or hydrocarbyl, preferably with 1 to 20 carbon atoms , such as 1, 1 '-biphenol, 1,1' -bullphol. The groups R1, R2 and R3 can be linked directly with one another, ie not only through the central phosphorus atom. Preferably, the groups R1, R2 and R3 are not directly linked to one another.

In a preferred embodiment, radicals selected from the group consisting of phenyl, o-tolyl, m-tolyl and p-tolyl come into account as groups R1, R2 and R3. In a particularly preferred embodiment, two of the groups R1, R2 and R3, at most, should be phenyl groups.

In another preferred embodiment, two of the groups R1, R2 and R3, at most, should be o-tolyl groups.

As especially preferred compounds I, those which are of the formula I can be applied to o-tolyl) -0-) w (m-tolyl-0-) x (p-tolyl-0) and (phenyl-0-) zP (la) meaning w, x, y and z a natural number, and giving the following conditions: w -t- x. + y + z = 3 and w, z = 2.

These compounds I a are for example (p-tolyl-O-) (phenyl-0-) 2P, (m-tolyl-O) (phenyl-0-) 2P, (o-tolyl-O-) (phenyl-O) -) 2 P, (p-tolyl-O-) 2 (phenyl-O-), (m-tolyl-O-) 2 (phenyl-O-) P, (o-tolyl-0-) 2 (phenyl-O-) P, (m-tolyl-O-) (p-tolyl-O) (phenyl-O-) P, (o-tolyl-O) (p-tolyl-O-) (phenyl-O) -P, (o-tolyl-O-) (m-tolyl-O-) (phenyl-O-) P, (p- tolyl-0-) 3P, (m-tolyl-O-) (p-tolyl-O-) 2P, (o-tolyl-O-) (p-tolyl-O-) 2P, (m-tolyl-0- ) 2 (p-tolyl-0-) P, (o-tolyl-O-) 2 (p-tolyl-O-) P, (o-tolyl-O-) (m-tolyl-O) (p-tolyl) -0) P, (m-tolol-0-) 3P, (o-tolyl-O-) (m-tolyl-O-) 2P, (o-tolyl-0-) 2 (m-tolyl-O) - P, or mixtures of such compounds.

Mixtures containing (m-tolyl-O-) 3P, (m-tolyl-O-) 2 (p-tolyl-O-) P, (m-tolyl-O-) (p-tolyl-O-) can be obtained ) 2P and (p-tolyl-O-) 3P, for example, by transforming a mixture containing m-cresol and p-cresol, in particular, in a molar ratio of 2: 1, as is produced in the oil distillation process , with a phosphoric trihalide, such as phosphorus trichloride.

In another, equally preferred embodiment, the phosphites of the formula I -b described in more detail in DE-A 199 53 058 are included as phosphorus-containing ligands: P (0-Rx) x (0-R2) and (0-R3) z (0-R4) p (I b) being R1: an aromatic radical with a C-C18 alkyl substituent in the ortho position with respect to the oxygen atom linking the phosphorus atom with the aromatic system, or with an aromatic substituent in the ortho position with respect to the oxygen atom which binds to the phosphorus atom with the aromatic system, or with an aromatic system condensed in the ortho position with respect to the oxygen atom that joins the phosphorus atom with the aromatic system; R2: an aromatic radical with an alkyl-Ci-Ciß substituent in the meta position with respect to the oxygen atom linking the phosphorus atom with the aromatic system, or with an aromatic substituent in the meta position with respect to the oxygen atom which binds to the phosphorus atom with the aromatic system, or with an aromatic system condensed in meta position with respect to the oxygen atom that joins the phosphorus atom with the aromatic system, carrying the aromatic radical that is in ortho position with respect to the atom of oxygen that joins the phosphorus atom with the aromatic system, a hydrogen atom; R3: an aromatic radical with an alkyl-Ci-Ciß substituent in para position with respect to the oxygen atom linking the phosphorus atom with the aromatic system, or with an aromatic substituent in para position with respect to the oxygen atom that binds the phosphorus atom with the aromatic system, carrying the aromatic radical that is in the ortho position with respect to the oxygen atom that joins the phosphorus atom with the aromatic system, a hydrogen atom; R4: an aromatic radical which, being in ortho, meta or para position with respect to the oxygen atom that joins the phosphorus atom with the aromatic system, carries other substituents than those defined for R1, R2 and R3, bearing the aromatic radical that it is in ortho position with respect to the oxygen atom that joins the phosphorus atom with the aromatic system, a hydrogen atom; x: 1 or 2; y, z, p: independently of each other, 0, 1 or 2, provided that x + y + z + p = 3.

From the reading of DE-A 199 53 058, preferred phosphites of the formula I-b are released. As radical R1, suitable groups of o-tolyl, o-ethyl-phenyl, on-propyl-phenyl, o-isopropyl-phenyl, on-butyl-phenyl, o-sec-butyl-phenyl, o-ter- butyl-phenyl, (o-phenyl) -phenyl or 1-naphthyl.

As the radical R2, the groups m-tolyl, m-ethyl-phenyl, mn-propyl-phenyl, m-isopropyl-phenyl, mn-butyl-phenyl, m-sec-butyl-phenyl, m -tr-butyl-phenyl are preferred. , (m-phenyl) -phenyl or 2-naphthyl.

Suitable radicals R3 include p-tolyl, p-ethyl-phenyl, p-propyl-phenyl, p-isopropyl-phenyl, p-butyl-phenyl, p-sec-butyl-phenyl, p-ter- butyl-phenyl or (p-phenyl) -phenyl.

As the radical R 4, phenyl is preferred. It is preferred that p is equal to zero. For the indices x, y, z and p in compound I the following possibilities are given: Preferred phosphites of the formula I b are those in which p is equal to zero, and R1, R2 and R3 have been selected, independently from each other, from o-isopropyl-phenyl, m-tolyl and p-tolyl, and R 4 is phenyl.

Especially preferred phosphites of the formula I b are those in which R 1 is the o-isopropyl phenyl radical, R 2 is the m-tolyl radical and R 3 is the p-tolyl radical with the indices given in the table above; moreover those are those in which R1 is the o-tolyl radical, R2 is the m-tolyl radical and R3 is the p-tolyl radical with the indices given in the Table above; likewise are those in which R1 is the 1-naphthyl radical, R2 is 1 m-tolyl radical and R3 is the p-tolyl radical with the indices given in the table above; also those in which R1 is the radical o-tolyl, R2 is the 2-naphthyl radical and R 3 is the p-tolyl radical with the indices given in the table above; and finally those in which R1 is the o-isopropyl-phenyl radical, R2 is the 2-naphthyl radical and R3 is the p-tolyl radical with the indices given in the table above; as well as mixtures of those phosphites.

Phosphites of the formula I-b can be obtained a) transforming a phosphoric trihalogenide with an alcohol selected from the group consisting of Rx0H, R20H, R30H and ROH or mixtures thereof obtaining a monoester of dihalophosphoric acid, b) transforming said monoester of dihalophosphoric acid with an alcohol selected from the group consisting of R ^ OH, R20H, R30H and R40H or mixtures of these obtaining a diester of monohalophosphoric acid, c) transforming said diester of monohalophosphoric acid with an alcohol selected from the group consisting of R1OH, R2OH, R30H and R0H or mixtures thereof obtaining a phosphite of the formula I-b.

The transformation can be carried out in three separate steps. In the same way two of the three steps can be combined, that is a) with b) or b) with c). As an alternative, steps a), b) and e) may also be combined.

In that process, parameters and amounts of appropriate alcohols selected from the group consisting of R ^ OH, R2OH, R3OH and R4OH or mixtures thereof can be easily determined by some simple preliminary tests.

As the phosphoric trihalogenide, in principle, all phosphorus trihalides are included, preferably those in which chlorine, bromine, iodine, particularly chlorine, as well as mixtures thereof are used as halogenides. Mixtures of various phosphines substituted by halide in the same or different manner can also be used as phosphoric trihalide. PC13 is especially preferred. Further details regarding the reaction conditions in the preparation of the phosphites I-b and in terms of the treatment result from the reading of DE-A 199 53 058.

The phosphites 1-b can also be used as a ligand in the form of a mixture of various phosphites I-b. A mixture of this kind can occur, for example, in the preparation of the phosphites I-b.

It is preferred, of course, that the ligand with phosphorus content be polydentate, in particular bidentate. Therefore, the ligand employed preferably has formula II in which X11, X12, X13, X21, X22, X23 mean, independently of each other, hydrogen or individual bond, R11, R stand for, independently of one another, identical or different organic radicals, individual or bridge, R21, R22 mean, independently of each other, the same or different organic radicals, individual or bridge, And it means bridge group.

Compound II is understood in the sense of the present invention as an individual compound or a mixture of different compounds of the previously indicated formula.

In a preferred embodiment X11, X12, X13, X21, X22, X23 can represent oxygen. In such a case, the bridge group Y is linked with phosphite groups.

In another preferred embodiment, X11 and X12 can represent oxygen and X13 a single bond or X11 and X13 represent oxygen and X12 a simple bond, so that the phosphorus atom surrounded by X11, X12 and X13 is the central atom of a phosphonite In such a case, X21, X22 and X23 can be oxygen or X21 and X22 are oxygen and X23 is a simple union or X21 and X23 are oxygen and X22 represents a simple union or X23 oxygen and X21 and X22 are a simple union or X21 is oxygen and X22 and X23 are a simple union or X21, X22 and X23 they represent a simple union, so that the phosphorus atom surrounded by X21, X22 and X23 is the central atom of a phosphite, a phosphonite, a phosphinite or a phosphine, preferably a phosphonite.

In another preferred embodiment, X13 can represent oxygen and X11 and X12 a single bond or X11 is oxygen and X12 and X13 are a single bond, so that the phosphorus atom surrounded by X11, X12 and X13 is the central atom of a phosphonite. In such a case, X21, X22 and X23 can represent oxygen or X23 is oxygen and X21 and X22 are a simple union or X21 is oxygen and X22 and X23 are a simple union or X21, X22 and X23 represent a simple union, so that the phosphorus atom surrounded by X21, X22 and X23 is the central atom of a phosphite, a phosphinite or a phosphine, preferably a phosphinite.

In another preferred embodiment, X11, X12 and X13 may represent a single bond, such that the phosphorus atom surrounded by X11, X12 and X13 is the central atom of a phosphine. In such a case, X21, X22 and X23 can represent oxygen or X21, X22 and X23 a simple bond, so that the phosphorus atom surrounded by X21, X22 and X23 is the central atom of a phosphite or a phosphine, preferably a phosphine.

As the bridging group Y, substituted aryl groups are preferably included, for example with C 1 -C 4 alkyl, halogen, such as fluorine, chlorine, bromine, halogenated alkyl, such as trifluoromethyl, aryl, such as phenyl, or unsubstituted aryl groups, preferably those with 6 to 20 carbon atoms in the aromatic system, especially pyrocatechol, bis (phenol) or bis (naphthol).

The radicals R11 and R12 can independently represent identical or different organic radicals. Advantageously, radicals R11 and R12 are advantageously included, preferably those with 6 to 10 carbon atoms, which can be unsubstituted or simple or multiply substituted, especially with C1-C4 alkyl, halogen, such as fluorine, chlorine , bromine, halogenated alkyl, such as trifluoromethyl, aryl, such as phenyl, or unsubstituted aryl groups.

The radicals R21 and R22 independently of one another can represent the same or different organic radicals. Advantageously, radicals R21 and R22 the aryl radicals, preferably those with 6 to 10 carbon atoms, which may be unsubstituted or single or multiply substituted, especially with C?-C4 alkyl, halogen, such as fluorine, chlorine, bromine, halogenated alkyl, trifluoromethyl, aryl, as phenyl, or unsubstituted aryl groups.

The radicals R11 and R12 can be individual or bridged. Also the radicals R21 and R22 can be individual or bridged. The radicals R11, R12, R21 and R22 can be all individual, two bridge and two individual or all four can be bridged as described.

In a particularly preferred embodiment, the compounds mentioned in US Pat. No. 5,723,641 of Formula I, II, III, IV and V are included. In a particularly preferred embodiment, the compounds mentioned in US Pat. No. 5,512 are included. 696 of Formula I, II, III IV, V, VI and VII, especially the compounds indicated in Examples 1 to 31. In an especially preferred embodiment, the indicated compounds of Formula I, II, III, IV are included , V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV and XV, in the document US 5,821,378 especially the compounds indicated in Examples 1 to 73.

In a particularly preferred embodiment, the compounds set forth in US 5,512,695 of Formula I, II, III, IV, V and VI, especially the compounds indicated therein in Examples 1 to 6, are included. especially preferred embodiment, the compounds described in US 5,981,772 of Formula I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII and XIV, particular compounds include applied in Examples 1 to 66.

In a particularly preferred embodiment, the compounds set forth in US 6,127,567 and the compounds applied in Examples 1 to 29 are included. In an especially preferred embodiment, the compounds of Formula I, II, III are included , IV, V, VI, VII, VIII, IX and X, mentioned in US 6,020,516, especially the compounds applied in Examples 1 to 33. In an especially preferred embodiment, the compounds indicated in the document are included. US 5,959,135 and the compounds applied therein in Examples 1 to 13.

In a particularly preferred embodiment, the compounds of Formula I, II and III mentioned in US 5,847,191 are included. In a particularly preferred embodiment, the compounds set forth in US 5,523,453 are included, especially the compounds represented therein in formulas 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 and 21. In an especially preferred embodiment - the compounds indicated in WO 01/14392 are included, preferably the compounds represented therein in formulas V , VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV, XVI, XVII, XXI, XXII, XXIII.

In a particularly preferred embodiment, the compounds indicated in WO 98/27054 are included. In a particularly preferred embodiment, the compounds indicated in WO 99/13983 are included. In a particularly preferred embodiment, the compounds indicated in WO 99/64155 are included.

In a particularly preferred embodiment, the compounds indicated in German patent application DE 100 380 37 are included. In one embodiment Especially preferred are the compounds indicated in German patent application DE 100 460 25. In a particularly preferred embodiment, the compounds set forth in the German patent application DE 101 502 85 are included.

In a particularly preferred embodiment, the compounds set forth in the German patent application DE 101 502 86 are included. In a particularly preferred embodiment, the compounds indicated in the German patent application DE 102 071 65 are included. In another form of Particularly preferred embodiment includes phosphorus-containing chelate ligands indicated in US 2003/0100442 Al.

In another particularly preferred embodiment, the phosphorus-containing chelate ligands included in the German patent application pre-published with file DE 103 50 999.2 of 30-10-2003 are included.

The compounds described 1, 1 a, 1 b and II, as well as their preparation, are known per se. Mixtures containing at least two of the compounds I, 1 a, I b and II can also be used as a ligand with phosphorus content.

In a particularly preferred embodiment of the process of the invention, the phosphorus-containing ligand of the nickel complex (0) and / or the phosphorus-containing free ligand is selected from tritolyl phosphite, ligands of bidentate chelates with phosphorus content, as well as the phosphites of Formula I b P (0-Rx) x (0-R2) and (0-R3) z (0-R4) p (Ib) wherein R1, R2 and R3 are independently selected from o-isopropyl-phenyl, m-tolyl and p-tolyl, R4 is phenyl; x is equal to 1 or 2, and y, z, p independently of each other are 0, 1 or 2, provided that x + y + z + p = 3; and its mixtures.

Reduction The process according to the invention for the preparation of nickel complexes with phosphorus ligands containing at least one central nickel (0) atom and at least one phosphorus-containing ligand by reduction is preferably carried out in the presence of a solvent. The solvent there is specially selected of the group consisting of organic nitriles, aromatic hydrocarbons, aliphatic hydrocarbons and mixtures of the aforementioned solvents. As regards organic nitriles, acetonitrile, propionitrile, n-butyronitrile, n-valeronitrile, cyanocyclopropane, acrylonitrile, crotonitrile, allyl cyanide, cis-2-pentenenitrile, trans-2-pentenenitrile, cis-3-pentenenitrile, trans-3- are preferably used. pentenenitrile, 4-pentenenitrile, 2-methyl-3-butenonitrile, Z-2-methyl-2-butennitrile, E-2-methyl-2-butenonitrile, ethylsuccinitrile, adiponitrile, methylglutarnitrile or mixtures thereof. With respect to the aromatic hydrocarbons, benzene, toluene, o-xylene, m-xylene, p-xylene or mixtures thereof can preferably be used. The aliphatic hydrocarbons may preferably be selected from the group of linear or branched aliphatic hydrocarbons, especially preferably from the group of cycloaliphatic substances, such as cyclohexane or methylcyclohexane, or mixtures thereof. Particular preference is given to using as solvents cis-3-pentenenitrile, trans-3-pentenenitrile, adiponitrile, methylglutarnitrile or mixtures thereof.

Preferably an inert solvent is used.

The concentration of the solvent is preferably 10 to 90% by mass, especially preferably from 20 to 70% by mass, in particular from 30 to 60% by mass, in each case based on the finished reaction mixture.

In a special embodiment of the present invention, the solvent is identical to the diluent used in the process according to the invention for the preparation of the anhydrous mixture containing the nickel halide (II) and the diluent.

In the process according to the invention, the concentration of the ligand in the solvent is preferably 1 to 90% by weight, particularly preferably 5 to 80% by weight, especially 50 to 80% by weight.

The reducing agent used in the process according to the invention is preferably selected from the group consisting of metals that are more electropositive than nickel, metal alkyls, electric current, complex hydrides and hydrogen.

When a metal that is more electropositive than nickel is used as the reducing agent in the process according to the invention, this metal is preferably selected from the group consisting of sodium, lithium, potassium, magnesium, calcium, barium, strontium, titanium. , vanadium, iron, cobalt, copper, zinc, cadmium, aluminum, gallium, indium, tin, lead and thorium. Iron and zinc are particularly preferred here. If aluminum is used as a reducing agentIt is advantageous if this is pre-activated by the reaction of a catalytic amount of mercury (II) salt or metal alkyl. For preference preactivation, triethylaluminum is used in an amount of preferably 0.05 to 50 mol%, especially preferably 0.5 to 10 mol%. The reduction metal is preferably finely distributed, with the term "finely distributed" meaning that the metal is used at a particle size less than a 10 mesh aperture, particularly preferably less than a 20 mesh aperture.

When a metal that is more electropositive than nickel is used as the reducing agent in the process according to the invention, that amount of metal it is preferably from 0.1 to 50% by weight, based on the reaction mass.

When metal alkyls are used as reducing agents in the process according to the invention, they are preferably lithium alkyls, sodium alkyls, magnesium alkyls, especially Grignard reagents, zinc alkyls or aluminum alkyls. Especially preferred are aluminum alkyls, such as trimethylaluminum, triethylaluminum, triisopropylaluminum or mixtures thereof, especially triethylaluminum. Metal alkyls may be dissolved in a substance or in inert organic solvent, such as hexane, heptane or toluene.

When complex hydrides are used as the reducing agent in the process according to the invention, metal-aluminum hydrides, such as lithium-aluminum hydrides, or metal-boron hydrides, such as sodium borohydride, are preferably used.

The molar ratio of the redox equivalent between the nickel (II) source and the preference reducing agent amounts to 1 -. 1 to 1 100, special preference from 1: 1 to 1-: 50, especially from 1: 1 to 1: 5.

In the method according to the invention, the ligand to be used can also be present in a ligand solution, which was already used as a catalyst solution in hydrocyanation reactions and is depleted of nickel (0). This "retrocatalyzed solution" usually has the following composition: - 2 to 60% by weight, especially 10 to 40% by weight of pentenenitrile, - 0 to 60% by weight, especially 0 to 40 *.% By weight of adiponitrile, - 0 to 10% by weight, especially 0 to 5% by weight of other nitriles, - 10 to 90% by weight, especially 50 to 90% by weight of the phosphorus content ligand and - 0 to 2% by weight, especially 0 to 1% by weight of nickel (0).

The free ligand contained in the retrocatalyzed solution can therefore be converted back into a nickel (0) complex according to the process according to the invention.

In a special embodiment of the present invention, the ratio of the nickel (II) source to the phosphorus-containing ligand is 1: 1 to 1: 100. Other preferred ratios of the nickel (II) source of the ligand with phosphorus content is 1: 1: 3, especially 1: 1 to 1: 2.

The process according to the invention can be carried out at any pressure. For practical reasons, pressure values are preferably between 0.1 bar and 5 bar, more preferably 0.5 bar and 1.5 bar.

The process according to the invention can be carried out by the system in batches or continuously.

It is possible to use the nickel (II) -ether adduct directly in the solution, or in the suspension thus obtained for the preparation of the nickel complexes (0) with phosphorus ligand. Alternatively, the adduct can also be first isolated and possibly dried, subsequently dissolved or resuspended again for the preparation of the nickel (0) complex with phosphorus ligand. An isolate of the adduct from the suspension can be carried out by the skilled person by methods known per se, such as filtration, centrifugation, sedimentation or by hydrocyclones, as described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, Unit Operation I, Vol. B2, VCH, Weinheim, 1988, in chapter 10, pages 10-1 to 10-59, chapter 11, pages 11-1 to 11-27 and chapter 12, pages 12-1 to 12-61.

In the process according to the invention, it is possible to work without excess nickel (II) halide or reduction agent, for example zinc, so that its cleavage is prevented after the formation of the nickel (0) complex.

In a special embodiment of the present invention, the method according to the invention includes the following process steps: (1) Drying of a nickel (II) halide containing water, by azeotropic distillation, (2) Precomplexation of the nickel halide (II) halide dried by zeotropic method in a solvent in the presence of a ligand with phosphorus content, (3) Aggregate of at least one reducing agent to the solution or suspension originated from step of the process (2) with an addition temperature of 20 to 120 ° C, (4) Agitation of a suspension or solution originated from the step of the process (3) with a transformation temperature of 20 to 120 ° C.

The precomplexation, aggregate and transformation temperatures can each rise independently from 20 ° C to 120 ° C. The precomplexation, the aggregation and the transformation, the temperatures of 30 ° C to 80 ° C are of special preference.

The precomplexation, aggregation and transformation periods can each rise independently from one minute to 24 hours'. The term of precomplex ation especially is from 1 minute to 3 hours. The aggregate period of preference is from 1 minute to 30 minutes. The transformation period of preference is 20 minutes to 5 hours.

Another object of the present invention are the solutions contained in the nickel (0) -linking phosphorus complexes obtainable by the process of the invention, as well as their use in the hydrocyanation of alkenes and unsaturated nitriles, especially in the butadiene hydrocyanation for the preparation of a mixture of pentenenitriles and the hydrocyanation of pentenenitrile in adiponitrile. The present invention also relates to its use in the isomerization of alkenes and unsaturated nitriles, especially of 2-methyl-3-butenonitriles to 3-pentenenitriles.

Another object of the present invention is a process for the preparation of a nickel (II) halogenide dried by azeotropic distillation, by removing water from mixtures containing at least one nickel (II) halide containing water, wherein mixture is added a diluent, whose point of boiling in the case of a non-azeotropic formation of the aforementioned diluent with water under the pressure conditions of the distillation indicated below, is higher than the boiling point of water, which at that boiling point of the water is liquid; or which forms an azeotrope or heteroazeotrope with water under the pressure and temperature conditions of the distillation indicated below, and the mixture containing the nickel halide (II) containing water and the dilution agent is distilled by separating the water or the mentioned azeotrope or the aforementioned heterozeotrope of this mixture and with obtaining an anhydrous mixture containing nickel halide (II) and said dilution agent. Other embodiments and conformations of this method have already been described previously.

The present inventions are explained in more detail by the following exemplary embodiments.

Exemplary embodiments In the examples for the synthesis of the complex, a solution of the chelate phosphonite 1 was used as a solution of the chelate ligand 1 in 3-pentenenitrile (65% by weight of the chelate, 35% by weight of 3-pentenenitrile).

In order to determine the yield, its content of complex active Ni (0) was studied in the prepared solutions of the complex. For this, the solutions were mixed with tri (m / p-tolyl) phosphite (usually 1 g of phosphite per 1 g of solution) and kept approx. 30 min. at 80 ° C, in order to achieve total recomplexation. The current-voltage curve in a solution at rest with respect to a reference electrode was then measured for electrochemical oxidation in a cyclo-voltammetric measuring device. which determines the peak current proportional to the concentration and corrects through a calibration with solutions of known concentrations of Ni (0), the Ni (0) content of the test solution, by the amount of the subsequent dilution with tri ( m / p-tolyl) phosphite. The values of Ni (0) mentioned in the examples indicate the content of Ni (0) in% by weight determined by this method, with respect to the total of the reaction solution.

Examples 1-4 describe the preparation of the suspensions with the immediately subsequent formation of a complex: Example 1: In a 250 ml flask with stirrer and water centrifuge were suspended 9.7 g of NiCl2 • 6H20 (41 mmol) in 100 ml of 3-pentenenitrile. The mixture was heated to boiling under reflux and removing the water there. A fine suspension was obtained in 3-pentenenitrile. The suspension was concentrated practically to dryness, resuspended in 13 g 3-pentenntrile and mixed with 100 g of chelate solution (86 mmol of ligand). At 50 ° C, 4 g of zinc powder (61 mmol, 1.4 eq.) Were added.

The mixture was heated at 60 ° C and stirred 3 h. Since no result was observed, stirring was continued for another 3 h at 80 ° C. A Ni (0) value of 1.1% (56% yield) was measured.

Example 2: In a 500 ml flask with stirrer and water centrifuge, a solution of 9.7 g of NiCl2-6H20 (41 mmol) in 10 g of water was mixed with 150 g of 3-pentenenitrile. The two-phase mixture was heated to boiling under reflux and there eliminating water. A fine suspension was obtained in 3-pentenonitrile. The suspension was concentrated practically to dryness, resuspended in 13 g of 3-pentenenitrile and mixed with 100 g of chelate solution (86 mmol of ligand). At 80 ° C, 4 g of zinc powder (61 mmol, 1.4 eq.) Were added and the mixture was stirred 6 h. A Ni (0) value of 1.4% (71% yield) was measured.

Step 3: A suspension prepared analogously to Example 2 was concentrated to dryness, resuspended in 3 g of 3-pentenenitrile and mixed with 50 g of sodium chloride solution. chelate (43 mmol of ligand). At 80 ° C, 4 g of zinc powder (61 mmol, 1.4 eq.) Was added and the mixture was stirred for 4 h. A Ni (0) value of 2.3% (60% yield) was measured.

Example 4: In a 250 ml flask with stirrer and water centrifuge, a solution of 19.7 g of NiCl2 • 6H20 (83 mmol) in 20 g water was mixed with 61 g of 3-pentenenitrile. The two-phase mixture was heated to boiling under reflux and there eliminating water. A thick suspension was obtained in 3-pentenenitrile which can hardly be stirred. The suspension was mixed after cooling to 80 ° C with 100 g of chelate solution (86 mmol of ligand). Then 8 g of zinc powder (122 mmol, 1.4 eq.) Were added at 80 ° C and the mixture was stirred for 4 h. A Ni (0) value of 1.2% (45% yield) was measured.

Examples 5 and 6 describe the separate preparation of a NiCl2 suspension.

Example 5: In a 2 1 flask with stirrer and water centrifuge, a solution of 194 g of NiCl 2 • 6 H 20 (816 mmol) in 100 g of water was mixed with 300 g of 3-pentenenitrile. The two-phase mixture was heated to boiling under reflux and there eliminating water. After 161 g of water had been separated (86% of the theoretical amount), the suspension in the flask was partly so thick and partly solidified in large solid agglomerates that the test had to be interrupted.

Example 6: In a 2 1 flask with stirrer, water centrifuge and dropping funnel, 700 g of 3-pentenenitrile were heated under reflux to boiling. To this boiling pentenonitrile was added dropwise a solution of 194 g of NiCl2-6H20 (816 mmol) * in 105 g of water at the same rate, to which the water was again separated in the water centrifuge. A fine, almost homogeneous suspension was obtained in 3-pentene-nitrile.

Examples 7-12 describe the preparation of the nickel complexes from a suspension prepared separately.

Example 7: A suspension (83 mmol of NiCl 2) prepared according to Example 6 with 100 g of chelate solution (86 mmol of ligand) was stirred in a 500 ml flask with stirrer under argon 74 g and stirred for 15 min. at 80 ° C. Then 8 g of zinc powder (122 mmol, 1.5 eq.) Were added at 80 ° C and stirred at 80 ° C for 5 h. A Ni (0) value of 1.7% (64% yield) was measured.

Example 8: In a 250 ml flask with stirrer was mixed under argon 37 g a suspension 42 mmol of NiCl 2) prepared according to Example 6 (with 50 g of chelate solution (43 mmol of ligand) and stirred 15 min at 50 ° C. Then, 3 g of zinc powder (46 mmol, 1.1 eq) was added at 50 ° C and stirred for 5 h at 50 ° C. A Ni (0) value of 1.2% (43% yield) was measured.

Example 9: A reaction was carried out analogously to Example 8, but prior to the addition of the zinc powder it was heated to 80 ° C. After 5 h a Ni (0) value of 1.4% (50% yield) was measured.

Example 10: A reaction was performed analogously to Example 8, but all steps were carried out at 80 ° C. After 5 h a Ni (0) value of 1.8% (61% yield) was measured.

Example 11: A reaction was carried out analogously to Example 7, but 6.8 g of iron powder (122 mmol, 1.5 eq.) Was added instead of the zinc powder. After 5 h a Ni (0) value of 1.2% (53% yield) was measured.

Example 12: In a 250 ml flask with stirrer was suspended under argon 47.6 g of a suspension prepared according to Example 6 (53 mmol of NiCl2) in 67.3 g of chelate solution (58 mmol of ligand) and cooled to 0 ° C. Next, slowly added 26.5 g of a 25% solution of triethylaluminum in toluene (58 mmol). After heating the solution at room temperature, stirring was continued for another 10 h. A Ni (0) value of 0.64% (28% yield) was measured.

In Example 13, a "retrocatalyst solution" was used as a ligand solution, which had already been used as a catalyst solution in hydrocyanation reactions and was strongly depleted in Ni (0). The composition of the solution amounts to approx. 20% by weight of pentenenitrile, approx. 6% by weight of adiponitrile, approx. 3% by weight of other nitriles, approx. 70% by weight of ligand (composed of a mixture of 40% by mole chelated phosphonite 1 and 60% by mole of tri (m / p-tolyl) phosphite) and a nickel (O) content of only 0.8 %.

Example 13: A suspension prepared according to Example 6 (42 mmol NiCl 2) with 50 g of retrocatalyzed solution was added to a 250 ml flask with agitator and stirred for 15 min. at 80 ° C. Then they were added to 80 ° C 3 g of zinc powder (46 mmol, 1.1 eq.) And stirred 5 h at 80 ° C. A Ni (0) value of 1.64% (according to a P: Ni ratio of 4: 1) was measured.

In Examples 14 to 19 tri (m / p-tolylphosphite) was used as the ligand.

Example 14: Into a 250 ml flask with stirrer was suspended under argon 100 g a suspension (25 mmol of NiCl 2) prepared analogously to Example 6 with 36 g (100 mmol) of tri (m / p-tolyl) phosphite and stirred under stirring. min. at 80 ° C. Then 1.8 g of zinc powder (28 mmol, 1.1 eq.) Was added at 80 ° C and stirred 4 h at 80 ° C. A Ni (0) value of 0.75% (72% yield) was measured.

Example 15: A reaction was performed analogously to Example 14, but 53.8 g (152 mmol) of tri (m / p-tolylphosphite) was used. A Ni (0) value of 0.8% (85% yield) was measured.

Example 16: A reaction was performed analogously to Example 15, but all steps of the procedure were carried out at 40 ° C. A Ni (0) value of 0.6% (65% yield) was measured.

Example 17: A reaction was performed analogously to Example 15, but all steps of the procedure were carried out at 60 ° C. A Ni (0) value of 0.95% (99% yield) was measured.

Example 18: A reaction was performed analogously to Example 14, but 71.8 g (203 mmol) of tri (m / p-tolylphosphite) was used. A Ni (0) value of 0.5% (85% yield) was measured.

In the comparative examples, anhydrous nickel chloride was used for sale in the market as a nickel source.

Comparative example 1: In a 500 ml flask with stirrer, 11 g (885 mmol) of NiCl 2 in 13 g of 3-pentenenitrile were suspended under argon, mixed with 100 g of chelate solution (86 mmol of ligand) and stirred 15 min. at 80 ° C.

After cooling to 40 ° C, 8 g of zinc powder were added (122 mmol, 1.4 eq.) And stirred 4 h at 40 ° C. A Ni (0) value of 0.05% (1% yield) was measured.

Comparative example 2: A reaction was carried out analogously to Comparative Example 1, but the temperature was maintained during the addition of the zinc powder at 80 ° C. After 5 h a Ni (0) value of 0.4% (10% yield) was measured.

Comparative example 3: In a 500 ml flask with stirrer, 11 g (85 mmol) of NiCl 2 in 13 g of 3-pentenenitrile were suspended under argon, mixed with 100 g of chelate solution. (86 mmol) as ligand and stirred 15 min. at 80 ° C. After After cooling to 60 ° C, 5.3 g of zinc powder (95 mmol, 1.1 eq.) was added and stirred for 10 h at 60-65 ° C. A Ni (0) value of 0.16% (4% yield) was measured.

Comparative example 4: A reaction was carried out analogously to Comparative example 3, but the temperature was maintained during the addition of the iron powder at 80 ° C. After 10 h a Ni (0) value of 0.4% (10% yield) was measured.

Claims (11)

1. A process for preparing a nickel (0) -phosphorus ligand complex containing at least one central nickel (0) atom and at least one phosphorus ligand, characterized in that it comprises reducing a nickel (II) halide dried by azeotropic distillation in the presence of at least one phosphorus ligand selected from the group consisting of phosphites, phosphinites and phosphonites.

2. The process according to claim 1, characterized in that the nickel (II) halides are selected from the group consisting of nickel (II) chloride, nickel (II) bromide and nickel (II) iodide.

3. The process according to claim 1 or 2, characterized in that the nickel halide (II) dried by azeotropic distillation is prepared by a process to remove water from the corresponding nickel halide (II) aqueous, by mixing the mixture with a diluent whose boiling point, in the case that said diluent does not form an azeotrope with water under the conditions of pressure? Distillation mentioned below, is greater than the boiling point of the water and is liquid at this boiling point of water, or forming an azeotrope or heteroazeotrope with water under the conditions of pressure and temperature of the distillation mentioned below, and distilling the mixture comprising the nickel halide (II) ) aqueous and the diluent to remove water or the mentioned azeotrope or the aforementioned heteroazeotrope of this mixture to obtain an anhydrous mixture comprising nickel (II) halide and said diluent.

4. The process according to claim 3, characterized in that the diluent is an organic diluent having at least one nitrile group.

5. The process according to any of claims 1 to 4, characterized in that the reducing agent used is a metal that is more electropositive than nickel.

6. The process according to any of claims 1 to 4, characterized in that the reducing agent used is a metal allyl, electric current, a complex hydride or hydrogen.

7. The process according to claim 6, characterized in that the ligand is bidentate.

8. The process according to any of claims 1 to 7, characterized in that the phosphorus ligand is present in a catalytic solution that has already been used in hydrocyanation reactions.

9. A mixture comprising nickel- (0) -phosphorus ligand complexes, characterized in that it can be obtained by a process according to any of claims 1 to 8.

10. The use of mixtures comprising nickel (0) -phosphorus ligand complexes according to claim 9, in the hydrocyanation and isomerization of alkenes and in the hydrocyanation and isomerization of unsaturated nitriles.

11. A process for preparing a nickel (II) halide dried by azeotropic distillation by removing water from mixtures comprising at least one aqueous nickel (II) halide, characterized in that it comprises mixing the mixture with cis-3-pentenenitrile, trans-3-pentenenitrile, adiponitrile, methylglutaronitrile or mixtures thereof as diluents whose boiling points, in the case that said diluent does not form an azeotrope with water under the pressure conditions of the distillation mentioned below, is greater than the point of boiling water and is liquid at this boiling point of water, or forming an azeotrope or heteroazeotrope with water under the conditions of pressure and temperature of the distillation mentioned below, and distilling the mixture comprising the nickel halide (II) aqueous and the diluent to remove water or the aforementioned azeotrope or the heteroazeotrope mentioned from this mixture to obtain an anhydrous mixture comprising nickel (II) halide and said diluent.