Group VI precursor compounds

Abstract

The invention relates to group VI precursor compounds. The present invention provides a simple process for the preparation of various Group VI precursor compounds that can be used for vapor deposition of such Group VI metals on solid substrates, especially microelectronic semiconductor device substrates. The method provides an effective means of obtaining such volatile materials, which can then be used as a source of molybdenum, chromium or tungsten containing materials to be deposited on the substrate. In addition, the present invention provides a method for vapor deposition of the compound on a microelectronic device substrate.

Description

[0001] This application is a divisional application of the patent application with the application date of February 27, 2020, application number 202080017228.5, and invention title "Group VI Precursor Compounds". Technical Field

[0002] The present invention relates to certain precursors for the chemical vapor deposition of certain Group VI materials and methods for their preparation. Background Art

[0003] Due to the characteristics of extremely high melting points, low thermal expansion coefficients, low resistivity, and high thermal conductivity of Group VI metals (such as molybdenum, chromium, and tungsten), they are increasingly used in the manufacture of semiconductor devices, including their use in diffusion barriers, electrodes, photomasks, power electronics substrates, low-resistivity gates, flat panel displays, and interconnects.

[0004] This utility has spurred efforts to achieve the deposition of molybdenum, chromium, and tungsten films for such applications, characterized by high conformality and high deposition rates of the deposited films to accommodate efficient high-volume manufacturing operations. This, in turn, has enabled efforts to develop improved molybdenum and tungsten source reagents for chemical vapor deposition operations and improved process parameters utilizing such reagents. Summary of the Invention

[0005] The present invention provides a facile method for preparing various Group VI precursor compounds useful for the chemical vapor deposition of certain Group VI metals onto solid substrates, particularly substrates of microelectronic semiconductor devices. The method provides an effective means for obtaining and isolating the volatile solid or liquid materials, which can then serve as a source of molybdenum, chromium, or tungsten-containing materials to be deposited onto the substrate. Additionally, the present invention provides a method for the chemical vapor deposition of such compounds onto microelectronic device substrates. Brief Description of the Drawings

[0006] Figure 1 is a depiction of the three-dimensional solid-state crystal structure of MoO2Cl2(CH3CN)2.

[0007] Figure 2 is a depiction of the three-dimensional solid-state crystal structure of WO2Cl2(CH3CN)2.

[0008] Figure 3 is a graph of the molybdenum deposition rate ( / cycle) on a titanium nitride substrate versus the substrate temperature (°C) using MoO2Cl2(dimethoxyethane) as a precursor.

[0009] Figure 4 is the XRF carbon (X-ray fluorescence analysis for carbon) (μg m / cm2 / 100 Mo) versus substrate temperature (°C). Therefore, Figure 3 and 4 Schematic illustration of process parameters for preferential deposition of Mo relative to MoC.

[0010] Figure 5 It is a three-dimensional solid-state crystal structure drawing of MoO2Cl2(tetrahydrofuran)2. DETAILED DESCRIPTION

[0011] In a first aspect, the present invention provides a method for preparing a compound of formula (I)

[0012]

[0013] wherein M is selected from molybdenum, chromium and tungsten, X is selected from fluorine, chlorine, bromine and iodine, and each L1 and L2 are the same or different and constitute:

[0014] (i) a monodentate hydrocarbon-based ligand coordinated to M, or

[0015] (ii) together form a bidentate hydrocarbon ligand coordinated to M;

[0016] The method comprises:

[0017] (A) The following compound

[0018]

[0019] contacting with: (a) water containing from about 0.1% (w / w) to about 48% (w / w) of a compound of formula HX, and (b) a compound of formula L1 and / or L2; subsequently

[0020] (B) isolating the compound of formula (I) into a solid or liquid.

[0021] As used herein, the term "hydrocarbyl" refers to a C2-C4 hydrocarbon group comprising carbon and hydrogen atoms and optionally containing at least one nitrogen, sulfur or oxygen atom. 16 The hydrocarbon group may include straight-chain or branched saturated, unsaturated and polyunsaturated alkylene and cycloalkylene groups and may be substituted, for example, by one to five groups selected from the group consisting of C1-C6 alkoxy, carboxyl, nitro, amino, C2-C6 aminocarbonyl, C2-C6 amide, cyano, C2-C7-alkoxycarbonyl, C2-C7-alkanoyloxy, hydroxyl, aryl, heteroaryl, thiol, thioether, C2-C6 10 Dialkylamino, C3-C 15 The terms "C1-C6 alkoxy", "C2-C7-alkoxycarbonyl" and "C2-C7-alkanoyloxy" are used to denote the radicals corresponding to the structures --OR 3, --CO2R 3 and --OCOR 3 groups, where R 3 is a C1-C6 alkyl group or a substituted C1-C6 alkyl group. The terms "C2-C 16 aminocarbonyl" and "C2-C 16 amido" are used to denote groups corresponding to the structures --NHCOR 4 , --CONHR 4 respectively, where R 4 is a C1-C7 alkyl group. As described above, L1 and L2 contain the hydrocarbon groups and contain at least one nitrogen, sulfur or oxygen atom.

[0022] L1 and L2 are independently selected and represent monodentate ligands or together form a bidentate ligand. Generally, L1 and L2 contain hydrocarbon groups having at least one oxygen, sulfur or nitrogen atom. The ligands can be selected from, for example, tert-butyl nitrile, toluene, tetrahydrofuran and acetonitrile, and the groups are optionally substituted with one or more groups selected from: halogen, cyano, nitro, C1-C6 alkyl, C1-C6 alkoxy, tetrahydrofuran, C1-C6 alkoxycarbonyl and phenyl. Other examples include 1,2-dimethoxyethane; 1,2-diethoxyethane; 1,2-dimethoxypropane; N,N-dimethylacetamide; N,N-dimethylformamide; N,N-dimethylcyanoacetamide; diamines and triamines such as N,N,N',N'-tetramethylethylenediamine, ethylenediamine, hexamethylenediamine, diethylenetriamine and diethylenetriamine; dimethyl sulfoxide; and diols such as ethylene glycol, propylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol.

[0023] The separated compound of formula (I) in step (B) can be carried out by: extracting the compound from the aqueous reaction mixture using a water-immiscible solvent, followed by evaporating the solvent or crystallization. Alternatively, a water-soluble solvent such as an alcohol (e.g., ethanol) can be added to the aqueous solution to induce precipitation of the desired compound of formula (I). If desired, the solid compound of formula (I) can be purified by crystallization and / or vacuum sublimation.

[0024] It should be understood that the structures of the compounds of the present invention shown above are drawn in a two-dimensional format and do not necessarily represent their three-dimensional orientation.

[0025] Alternatively, once formed, the compound of formula (I) can react with additional / different compounds of formula L1 and / or L2 to form different compounds of formula (I) via a displacement reaction. Accordingly, in another embodiment, the present invention provides the above method, which further comprises the step of contacting the compound of formula (I) with a compound selected from: tert-butyl nitrile, toluene, tetrahydrofuran, and acetonitrile, and said group is optionally substituted with one or more groups selected from halo, cyano, nitro, C1-C6 alkyl, C1-C6 alkoxy, tetrahydrofuran, C1-C6 alkoxycarbonyl, and phenyl; 1,2-dimethoxyethane; 1,2-diethoxyethane; 1,2-dimethoxypropane; N,N-dimethylacetamide; N,N-dimethylformamide; N,N-dimethylcyanoacetamide; N,N,N',N'-tetramethylethylenediamine, ethylenediamine, hexaethylenediamine, diethylenetriamine and diethylenetriamine; dimethyl sulfoxide; and ethylene glycol, propylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol,

[0026] to obtain a compound of formula (I) having a different ligand of formula L1 and / or L2.

[0027] In other embodiments, the present invention provides a compound of formula (I)

[0028]

[0029] wherein M is selected from molybdenum, chromium, and tungsten, X is selected from fluorine, chlorine, bromine, and iodine, and each L1 and L2 is the same or different and consists of:

[0030] (i) a monodentate hydrocarbyl ligand coordinated to M, or

[0031] (ii) together forming a bidentate hydrocarbyl ligand coordinated to M;

[0032] which is in solid or liquid form. In certain embodiments, the compound of formula (I) has less than about 3 wt% impurities. In other embodiments, the compound of formula (I) has less than 1 wt% impurities. In other embodiments, the compound of formula (I) is isolated in crystalline form. Specific examples of the crystalline form of the compound of formula (I) include MoO2Cl2(CH3CN)2 and WO2Cl2(CH3CN)2 and MoO2Cl2(tetrahydrofuran)2. In another embodiment, the present invention provides a compound having the formula MoO2Cl2(CH3CN)2, in crystalline form and having an x-ray crystal structure as shown in Figure 1 In another embodiment, the present invention provides a compound having the formula WO2Cl2(CH3CN)2, in crystalline form and having an x-ray crystal structure as shown in Figure 2The compound of the x-ray crystal structure shown in Figure 5 The compound of the x-ray crystal structure shown in. These crystalline forms are further characterized in the following experimental section.

[0033] In another embodiment, the present invention provides a compound having the formula MoO2Cl2(tetrahydrofuran)2, in a crystalline form and having an x-ray crystal structure as shown in

[0034]

[0035] In another embodiment, the present invention provides a compound having the formula WO2Cl2(CH3CN)2, having an orthorhombic crystal system and unit cell dimensions of approximately the following:

[0036]

[0037] In another embodiment, the present invention provides a compound having the formula MoO2Cl2(tetrahydrofuran)2, having an orthorhombic crystal system and unit cell dimensions of approximately the following:

[0038]

[0039] As used herein, the term "unit cell" refers to the smallest and simplest volume element of a crystal that represents the unit of the crystal pattern completely. The dimensions of the unit cell are defined by six values: the dimensions a, b, and c and the angles α, β, and γ. A crystal is an effective packing array of many unit cells.

[0040] As used herein, the term "orthorhombic unit cell" refers to a unit cell in which a≠b≠c; α = β = γ = 90°.

[0041] As used herein, "lattice" refers to an array of points defined by the vertices of the stacked unit cells, as determined by single crystal x-ray diffraction analysis.

[0042] As used herein, "space group" refers to the symmetry of the unit cell. In a space group name (e.g., C2), the capital letter indicates the lattice type, and the other symbols represent the symmetry operations that can be performed on the unit cell without changing its appearance.

[0043] In the method of the present invention, suitable water-immiscible solvents include dichloromethane, ethyl acetate, diethyl ether, toluene, benzene, pentane, etc.

[0044] In one embodiment, the method is carried out at an elevated temperature (e.g., from about 20°C to about 100°C).

[0045] The compound of formula (I) can also be prepared by using starting materials of the following formula:

[0046]

[0047] That is, a compound of the general formula A2MO4, wherein M is selected from chromium, molybdenum or tungsten, and A is selected from Group I and Group II metals or an ammonium cation. Examples of said cations include Li + , Na + , K + , NH4 + , alkylammonium compounds, etc. Said compound can be similarly reacted with HX in the presence of a compound of formula L1 and / or L2 to obtain the desired precursor compound.

[0048] The method of the present invention provides certain compounds which can in turn be used to vapor deposit certain Group VI metals onto various substrates, including substrates of microelectronic semiconductor devices. Thus, in another aspect, the present invention provides a method of forming a material on a substrate, which comprises contacting the substrate with a compound of formula (I)

[0049]

[0050] wherein M is selected from molybdenum, chromium and tungsten, X is selected from fluorine, chlorine, bromine and iodine, and each of L1 and L2 is the same or different and consists of:

[0051] (i) a monodentate hydrocarbyl ligand coordinated to M, or

[0052] (ii) together forming a bidentate hydrocarbyl ligand coordinated to M;

[0053] Depositing a molybdenum, chromium or tungsten-containing material onto the substrate under vapor deposition conditions.

[0054] The substrate used in the deposition method of the present invention can be of any suitable type and can include (for example) a semiconductor device substrate, such as a silicon substrate, a silicon dioxide substrate or other silicon-based substrates. In various embodiments, the substrate can include one or more metal or dielectric substrates, such as Co, Cu, Al, W, WN, WC, TiN, Mo, MoC, SiO2, W, SiN, WCN, Al2O3, AlN, ZrO2, HfO2, SiO2, lanthanum oxide (La2O3), tantalum nitride (TaN), ruthenium oxide (RuO2), iridium oxide (IrO2), niobium oxide (Nb2O3) and yttrium oxide (Y2O3).

[0055] In certain embodiments, for example in the case of an oxide substrate (such as silicon dioxide) or another alternative silicon or polysilicon substrate, the substrate can be treated or fabricated to include a barrier layer (such as titanium nitride) thereon for subsequent deposition of the material.

[0056] In one embodiment, a layer containing molybdenum, chromium, or tungsten deposited on a substrate surface can be formed by, for example, pulsed chemical vapor deposition (CVD), atomic layer deposition (ALD), or other vapor deposition techniques without pre-forming a nucleation layer and thus directly utilizing the vapor from the compound of formula (I). The corresponding vapor contacting step of formula (I) can be alternately and repeatedly carried out for the required number of cycles to form a molybdenum, chromium, or tungsten film of the desired thickness. In various embodiments, the contact of the substrate (e.g., titanium nitride) layer with the vapor is carried out at a temperature as low as 350 °C and in other embodiments in the range of 300 °C to 750 °C.

[0057] Using the vapor from the compound of formula (I), a material containing molybdenum, chromium, or tungsten can be directly deposited on a substrate to form a bulk deposit of elemental molybdenum, chromium, or tungsten or their corresponding oxides. The concentration of H2 is crucial for the formation of the metal or oxide because more than four molar equivalents or an excess of H2 is required for metal formation. Less than four (4) molar equivalents of H2 will result in the formation of varying amounts of the metal oxide, and thus further exposure to H2 will be required to reduce the metal oxide thus formed.

[0058] In various embodiments, the material containing molybdenum, chromium, or tungsten is deposited on the substrate surface at a temperature in the range of 300 °C to 750 °C. The method can be carried out such that the vapor deposition conditions cause elemental molybdenum, chromium, or tungsten to be deposited on the substrate as a metal-containing material. The vapor deposition conditions can have any suitable characteristics and can include, for example, the presence of hydrogen or other reducing gases to form a bulk layer of elemental molybdenum, chromium, or tungsten on the substrate.

[0059] More generally, according to the present disclosure, a broad method of forming a material containing molybdenum, chromium, or tungsten on a substrate can include vapor deposition conditions including the presence of hydrogen or other reducing gases. The material containing molybdenum, chromium, or tungsten can be deposited on a barrier layer or surface in the presence or absence of hydrogen. For example, the barrier layer can be composed of titanium nitride, and the titanium nitride layer can be contacted with the vapor from the compound of formula (I) in the presence of hydrogen.

[0060] In another embodiment, when using the compound of formula (I) as a means for depositing metal oxide films (e.g., MoO2, WO3, and Cr2O3), an oxidation co-reactant (e.g., oxygen) can be added to the method.

[0061] It should be understood that the present invention can be implemented in many alternative ways and under a variety of process conditions. The method of the present invention can be implemented, for example, in a process for manufacturing semiconductor devices on a substrate. The semiconductor device can be of any suitable type and can include, for example, a DRAM device, a 3-D NAND device, or other devices or device integration structures. In various embodiments, the substrate can include vias in which a molybdenum-containing material is deposited. For example, the device can have an aspect ratio of depth to lateral dimension in the range of 10:1 to 40:1. In still other embodiments, the device can be a film for a flat panel display or a mobile device.

[0062] According to the present invention, the process chemistry for depositing the molybdenum-containing material can include depositing elemental molybdenum Mo(0) through the reaction: 2MO2Cl2[(L1)(L2)] + 6H2 → 2M (where M = molybdenum, chromium, or tungsten) + 4HCl + 4H2O. The material (M) containing molybdenum, chromium, or tungsten deposited according to the method of the present invention can be characterized by any suitable evaluation metrics and parameters, such as the deposition rate of the material containing molybdenum, chromium, or tungsten, the film resistivity of the deposited material containing molybdenum, chromium, or tungsten, the film morphology of the deposited material containing molybdenum, chromium, or tungsten, the film stress of the deposited material containing molybdenum, chromium, or tungsten, the step coverage of the material, and the process window or process envelope of appropriate processing conditions. Any suitable evaluation metrics and parameters can be used to characterize the deposited material and relate it to specific process conditions to enable mass production of the corresponding semiconductor products. Advantageously, the method of the present invention is capable of depositing a film of high-purity molybdenum, chromium, or tungsten on a semiconductor device. Thus, in another aspect, the present invention provides a semiconductor device having a molybdenum film deposited thereon, wherein the film contains greater than 99% molybdenum, chromium, or tungsten.

[0063] In certain embodiments, the present disclosure relates to a method of forming a material containing molybdenum, chromium, or tungsten on a substrate, which includes depositing molybdenum, chromium, or tungsten on the surface of the substrate by a chemical vapor deposition (CVD) process using a precursor compound of formula (I) to produce a material containing molybdenum, chromium, or tungsten on the substrate.

[0064] The process may be carried out in any suitable manner as described in various aspects herein. In a specific embodiment, the method may be carried out using a vapor deposition process comprising chemical vapor deposition (e.g., pulsed chemical vapor deposition). The method may be carried out such that the resulting molybdenum-, chromium-, or tungsten-containing material consists essentially of elemental molybdenum, chromium, or tungsten, and in various embodiments, molybdenum, chromium, or tungsten may be deposited on the substrate surface in the presence of hydrogen or other suitable reducing gas. In other embodiments of the present invention, the precursor of formula (I) and the reducing gas may be successively delivered in a pulsed manner to deposit a molybdenum film in a pulsed manner, wherein the pulse sequence is optimized for film conformality and film resistivity. The method may be carried out in the manufacture of semiconductor device products (such as DRAM devices, or 3-D NAND, logic devices, flat panel displays, or IC packaging components).

[0065] Generally, the method of the present disclosure for forming a molybdenum-, chromium-, or tungsten-containing material on a substrate may be carried out to achieve deposition of the molybdenum-, chromium-, or tungsten-containing material at a high step coverage level (e.g., a step coverage in the range of about 75% to about 100%).

[0066] The present invention may be further illustrated by the following examples of its preferred embodiments, but it should be understood that including these examples is for illustrative purposes only and is not intended to limit the scope of the present invention unless otherwise specifically indicated.

[0067] Experimental section

[0068] Using the following general procedure, the compound of formula (I) can be prepared:

[0069] Synthesis procedure No. 1.

[0070] Load MoO3 (20.0 g, 138 mmol) into a 500 mL round-bottom flask equipped with a magnetic stir bar. Add HCl (200 mL, 37%) directly to MoO3. The reaction flask is equipped with a water-cooled condenser (5 °C), and the resulting light green suspension is heated to near reflux (95 °C) using an oil bath. After about 2 hours, the reaction appears as a clear light green solution. Cool the reaction to room temperature and then place it in an ice bath. At this time, add DME (50 mL) directly to the cooled solution and allow the reaction to warm to room temperature and stir overnight. The next morning, pour the light green solution into a 1 L separatory funnel and extract with DCM (2 x 200 mL). Combine the organic layers, dry over MgSO4, filter, place in a 1 L round-bottom flask equipped with a magnetic stir bar, and remove the solvent under reduced pressure to obtain MoO2Cl2(dimethoxyethane) as an off-white solid. Mass = 12.68 g, yield = 31.8%. The product can be purified by vacuum sublimation (80 °C, at 25 millitorr (mTorr)). 11H NMR (400 MHz, C6D6, 298 K): δ 3.29 (s, 6H); 2.78 (s, 4H) ppm. 13 13C{1H} NMR (100 MHz, C6D6, 298 K): δ 70.68, 64.13 ppm.

[0071] Synthesis procedure No. 2

[0072] General formula A2MO4, where M = chromium, molybdenum or tungsten and A = lithium, sodium or potassium.

[0073] Here, the general synthesis procedure and post-treatment are very similar to Procedure No. 1

[0074]

[0075] That is, a compound of the general formula A2MO4, where M is selected from chromium, molybdenum or tungsten, and A is selected from Group I and Group II metals or ammonium cations. Examples include Li + , Na + , K + , NH4 + , alkylammonium compounds, etc.

[0076] Synthesis procedure No. 3

[0077] Ligand substitution can be utilized to synthesize the compound of formula (I). For example, the MoO2Cl2(N,N-dimethylformamide)2 complex can be prepared using Procedure No. 1 above, and then the N,N-dimethylformamide ligand is replaced by dimethoxyethane via solvolysis to produce MoO2Cl2(dimethoxyethane).

[0078] As described above, Figure 1 is a three-dimensional solid crystal structure illustration of MoO2Cl2(CH3CN)2. This compound was subjected to X-ray crystallographic analysis and the following data were obtained:

[0079] Table 1. Crystal data and structure refinement of MoO2Cl2(CH3CN)2.

[0080]

[0081]

[0082] Table 2. Atomic coordinates (×10 4 ) and equivalent isotropic displacement parameters U(eq) is defined as one-third of the trace of the orthogonalized U ij tensor.

[0083]

[0084]

[0085] Table 3. Bond lengths and angles [°] of MoO2Cl2(CH3CN).

[0086]

[0087]

[0088]

[0089]

[0090] Symmetry transformations used to generate equivalent atoms:

[0091] #1 x, -y+1 / 2, z #2 x, -y+3 / 2, z

[0092] Table 4. Anisotropic displacement parameters of MoO2Cl2(CH3CN). The anisotropic displacement factor exponent takes the form: -2π 2 [h 2 a* 2 U 11 +...+2h k a*b*U 12 )

[0093]

[0094]

[0095] Table 5. Hydrogen coordinates (×10 4 ) and isotropic displacement parameters of MoO2Cl2(CH3CN).

[0096]

[0097] As described above, Figure 2 is a three-dimensional solid-state crystal structure illustration of WO2Cl2(CH3CN)2.

[0098] Table 6. Crystal data and structure refinement of WO2Cl2(CH3CN)2.

[0099]

[0100]

[0101] Table 7. Atomic coordinates (×10 4 ) and equivalent isotropic displacement parameters of WO2Cl2(CH3CN)2 U(eq) is defined as the orthonormalized U ij One third of the trace of the tensor.

[0102]

[0103] Table 8. Bond lengths of WO2Cl2(CH3CN)2 and angles [°].

[0104]

[0105]

[0106] Symmetry transformations used to generate equivalent atoms:

[0107] #1 - x + 1, y, -z + 1 / 2

[0108] Table 9. Anisotropic displacement parameters of WO2Cl2(CH3CN)2 The anisotropic displacement factor exponent takes the following form: -2π 2 [h 2 a* 2 U 11 +... + 2h k a*b*U 12

[0109]

[0110] Table 10. Hydrogen coordinates of WO2Cl2(CH3CN)2 (×10 4 ) and isotropic displacement parameters

[0111]

[0112] As described above, Figure 5 is a three-dimensional solid-state crystal structure illustration of MoO2Cl2(THF)2 (THF = tetrahydrofuran).

[0113] This compound was subjected to X-ray crystallographic analysis and the following data were obtained:

[0114] Table 11. Crystal data and structure refinement of MoO2Cl2(THF)2.

[0115]

[0116]

[0117] Table 12. Atomic coordinates (×10 4 ) and equivalent isotropic displacement parameters ​For Example 11, U(eq) is defined as the orthonormalized U ij One third of the trace of the tensor.

[0118]

[0119] Table 13. Bond lengths of MoO2Cl2(THF)2 and angles [°].

[0120]

[0121]

[0122]

[0123]

[0124] Symmetry transformations used to generate equivalent atoms:

[0125] Table 14. Anisotropic displacement parameters of MoO2Cl2(THF)2 The anisotropic displacement factor exponent takes the following form: -2π 2 [h 2 a* 2 U 11 +...+2h k a*b*U 12

[0126]

[0127] Table 15. Hydrogen coordinates (×10 4 ) and isotropic displacement parameters of MoO2Cl2(THF)2

[0128]

[0129] The following table illustrates various physical properties of certain compounds of formula (I):

[0130]

[0131] Abbreviations:

[0132]

[0133] STA-DSC:

[0134] Simultaneous thermal analysis - differential scanning calorimetry.​

Claims

1. A method for preparing a compound of formula (I), wherein M is selected from tungsten and chromium, X is selected from fluorine, chlorine, bromine and iodine, and each of L1 and L2 is the same or different and consists of: (i) a monodentate hydrocarbyl ligand coordinated to M, or (ii) together forming a bidentate hydrocarbyl ligand coordinated to M; The method comprises: (A) contacting a compound of the following formula with the following: (a) water containing from about 0.1% (w / w) to about 48% (w / w) of a compound of formula HX, and (b) a compound of formula L1 and / or L2; subsequently (B) extracting the compound of formula (I) with a non-coordinating, water-immiscible solvent and separating the compound of formula (I) as a solid or a liquid.

2. The method according to claim 1, wherein X is fluorine.

3. The method according to claim 1, wherein X is chlorine.

4. The method according to claim 1, wherein X is bromine.

5. The method according to claim 1, wherein X is iodine.

6. The method according to claim 1, wherein L1 and L2 are dimethoxyethane.

7. The method according to claim 1, wherein the non-coordinating, water-immiscible solvent is dichloromethane, ethyl acetate, diethyl ether, toluene, benzene or pentane.

8. The method according to claim 6, wherein the non-coordinating, water-immiscible solvent is dichloromethane.

9. The method according to claim 1, wherein M is tungsten.

10. The method according to claim 1, wherein M is chromium.

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