A high-purity tungsten complex precursor and a synthesis method thereof

Abstract

The application relates to the technical field of tungsten precursor synthesis, in particular to a high-purity tungsten complex precursor and a synthesis method thereof. The (Me2N)4W2Cl2 intermediate is obtained by sequentially reacting a tungsten tetrachloride ethylene glycol dimethyl ether adduct with raw materials such as dimethylaminolithium and trimethylchlorosilane, and then the intermediate is reacted with an alkoxide to obtain the target product. The whole process operation condition is convenient; the reaction process is peaceful, the energy consumption is low, the safety is high; the raw materials are widely and cheaply sourced, the product yield is high, the process stability is good; the product metal purity is high, and the product metal purity meets the requirements of the semiconductor field.

Description

Technical Field

[0001] This invention relates to the field of tungsten precursor synthesis technology, and in particular to a high-purity tungsten complex precursor and its synthesis method. Background Technology

[0002] Two-dimensional transition metal chalcogenides are widely considered promising materials for future electronic device applications due to their graphene-like structures. Tungsten sulfide (WS2) among them exhibits broad application prospects in solar cells, the semiconductor industry, and especially in solid lubrication, due to its solid lubrication and bipolar electron transport properties. Among existing methods for preparing WS2 thin films, atomic layer deposition (ALD) has gained increasing attention due to its self-confined nature and excellent three-dimensional structure conformity. In recent years, literature has reported the deposition of good WS2 thin films using bis(tert-butylamine)bis(dimethylamine)tungsten (VI) as the tungsten source and hydrogen sulfide as the sulfur source via ALD.

[0003] The currently reported conventional synthesis method for bis(tert-butylamine)bis(dimethylamine)tungsten (VI) involves first synthesizing [(tBuN)2WCl2(NH2tBu)]2 from tungsten hexachloride and N-tert-butyltrimethylsilylamine, then reacting it with pyridine to obtain (tBuN)2WCl2(py)2, and finally reacting it with dimethylaminolithium to obtain the target product with a yield of 39%, as reported by Becker et al., Highly Conformal Thin Films of Tungsten Nitride Prepared by Atomic Layer Deposition from a Novel Precursor, Chem. Mater. 2003, 15, 2969-2976.

[0004] The above method not only requires the reaction to be carried out in three steps, but also requires the intermediates of each step to be separated separately, resulting in a low final yield; moreover, the raw material N-tert-butyltrimethylsilylamine is expensive, which is not conducive to large-scale production; finally, the third step requires the addition of dimethylamine lithium solid to the reaction system. Dimethylamine lithium is flammable, extremely sensitive to air, and the addition process is violently exothermic, posing a significant safety hazard.

[0005] Therefore, it is of great significance to develop a tungsten source material with a simple synthesis route, readily available raw materials, safe operation, high yield, and stability. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a high-purity tungsten complex precursor and its synthesis method, so as to solve the problems of complicated reaction, expensive raw materials, high operational risks and low yield.

[0007] To achieve the above objectives, the present invention provides a precursor for a high-purity tungsten complex, the structure of which is shown in general formula (I): (RO)2W2(NMe2)4 (Ⅰ) Wherein, R is a C1~C6 alkyl group.

[0008] Meanwhile, the present invention also provides a method for synthesizing the precursor of the high-purity tungsten complex, comprising the following steps: (1) Under an inert atmosphere, an organic lithium solution is added dropwise to an organic solution of dimethylamine at low temperature and the reaction is carried out for at least 2 hours to obtain a dimethylamine-based lithium system; (2) Add tungsten tetrachloride ethylene glycol dimethyl ether adduct to the dimethylamine lithium system and react for at least 2 hours. Then add trimethylchlorosilane to the system and continue the reaction for at least 12 hours. After separation and purification, the intermediate (Me2N)4W2Cl2 is obtained. (3) Under an inert atmosphere, the (Me2N)4W2Cl2 is dissolved in an organic solvent to obtain an organic solution of (Me2N)4W2Cl2. Then, an alkoxide is added to the organic solution of (Me2N)4W2Cl2 at low temperature. After reacting for at least 12 hours, the solution is separated and purified to obtain (RO)2W2(NMe2)4.

[0009] The beneficial effects of this invention are as follows: This invention provides a novel method for synthesizing high-purity ALD precursor tungsten complexes. The method involves reacting a tungsten tetrachloride ethylene glycol dimethyl ether adduct with dimethylaminolithium, trimethylchlorosilane, and other raw materials sequentially to obtain the (Me₂N)₄W₂Cl₂ intermediate. This intermediate is then reacted with an alkoxide to obtain the target product. The entire process is convenient to operate; the reaction is mild, energy-efficient, and highly safe; the raw materials are widely available and inexpensive; the product yield is high; and the process stability is good. The product has high metal purity, meeting the requirements for metal purity in the semiconductor field. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 The intermediate (Me2N)4W2Cl2 in the embodiments of the present invention 1 H NMR spectrum; Figure 2 The target product (tBuO)2W2(NMe2)4 of this invention embodiment 1 H NMR spectrum; Figure 3 The target product of this invention, (MeO)2W2(NMe2)4, is... 1 H NMR spectrum. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0013] To address the problems of cumbersome reaction processes, expensive raw materials, significant operational risks, and low yield in the conventional synthesis methods of bis(tert-butylamine)bis(dimethylamine)tungsten (VI) in the prior art, this invention provides a precursor of a high-purity tungsten complex, the structure of which is shown in general formula (I): (RO)2W2(NMe2)4 (Ⅰ) Wherein, R is a C1~C6 alkyl group.

[0014] As one possible implementation, R in the precursor is one of methyl, tert-butyl, and tert-butyl isomers; The precursor is one of (MeO)2W2(NMe2)4, (tBuO)2W2(NMe2)4 and its (tBuO)2W2(NMe2)4 isomer; The precursor has a metal purity of 6N.

[0015] Meanwhile, the present invention also provides a method for synthesizing the precursor of the high-purity tungsten complex, comprising the following steps: (1) Under an inert atmosphere, an organic lithium solution is added dropwise to an organic solution of dimethylamine at low temperature and the reaction is carried out for at least 2 hours to obtain a dimethylamine-based lithium system; (2) Add tungsten tetrachloride ethylene glycol dimethyl ether adduct to the dimethylamine lithium system and react for at least 2 hours. Then add trimethylchlorosilane to the system and continue the reaction for at least 12 hours. After separation and purification, the intermediate (Me2N)4W2Cl2 is obtained. (3) Under an inert atmosphere, the (Me2N)4W2Cl2 is dissolved in an organic solvent to obtain an organic solution of (Me2N)4W2Cl2. Then, an alkoxide is added to the organic solution of (Me2N)4W2Cl2 at low temperature. After reacting for at least 12 hours, the solution is separated and purified to obtain (RO)2W2(NMe2)4.

[0016] As one possible implementation, the alkoxide has the general formula ROM, where R is a C1-C6 alkyl group and M is an alkali metal; The organic lithium solution is a n-butyllithium n-hexane solution, the organic solution of dimethylamine is a dimethylamine n-hexane solution, the organic solvent is n-hexane, and the molar ratio of n-butyllithium to dimethylamine is 1:(1~1.2). The molar ratio of the tungsten tetrachloride ethylene glycol dimethyl ether adduct to n-butyllithium and trimethylchlorosilane is 1:(2~4):(1~1.2); The molar ratio of the (Me2N)4W2Cl2 intermediate to the alkoxide is 1:(2~2.1); The reaction temperature is -20~10℃.

[0017] Specifically, Example 1 of this invention provides a precursor for a high-purity tungsten complex, wherein the precursor is (tBuO)2W2(NMe2)4. Two tungsten atoms (W) are connected by direct metal-metal bonds (WW), four dimethylamino ligands (-NMe2) are attached to each tungsten atom (two ligands each), and two tert-butoxy ligands (-tBuO) are attached to each tungsten atom (one ligand each). Molecular formula: W2C 18 H 42 N4O2, structural formula as follows: .

[0018] The target product was synthesized using the following synthetic route: .

[0019] Specifically, under a nitrogen atmosphere, a 20% dimethylamine-n-hexane solution (178.6 g, 0.792 mol) and 1.5 L of n-hexane were added to a 3000 mL multi-necked reaction flask. The temperature was lowered to -10 °C, and a 2.5 mol / L butyllithium-n-hexane solution (288 mL, 0.72 mol) was added dropwise. The system turned into a white turbid liquid. After the addition was complete, the temperature was slowly restored to 0 °C, and the reaction was stirred for 2 hours. Tungsten tetrachloride ethylene glycol dimethyl ether adduct (99.8 g, 0.24 mol) was added to the system in portions. The system darkened in color. After the addition was complete, the temperature was slowly restored to room temperature, and the reaction was stirred for 2 hours. Finally, trimethylchlorosilane (28.2 g, 0.26 mol) was added dropwise. After the addition of mol was complete, the mixture was stirred at room temperature for 12 hours. Then, it was filtered through anhydrous and oxygen-free filter. The filtrate was first washed with n-hexane, and then concentrated. The filtrate was then crystallized at -30℃ and filtered again to obtain 62.7 g of orange-red crystals (Me2N)4W2Cl2, with a yield of 85%. 1 H NMR spectrum as shown Figure 1 As shown, (C6D6): 3.45 (s, 24H).

[0020] Under nitrogen atmosphere, (Me₂N)₄W₂Cl₂ intermediate (49.2 g, 0.08 mol) and 800 mL of n-hexane were added to a 2000 mL reaction flask. The mixture was cooled to 0 °C, and potassium tert-butoxide (18.4 g, 0.164 mol) was added in portions. After the addition was complete, the mixture was slowly brought back to room temperature and stirred for 12 h. The mixture was then filtered through anhydrous and oxygen-free channels. The filtrate was first washed with n-hexane, and then the solvent in the washed filtrate was evaporated. The crude product was further distilled to obtain a pale yellow product (tBuO)₂W₂(NMe₂)₄, 44.2 g, with a yield of 80%. 1 H NMR spectrum as shown Figure 2 As shown, the saturation values ​​were 3.45 (s, 24 H) and 1.35 (s, 18 H). The purity of the product was determined using inductively coupled plasma mass spectrometry (ICP-MS), and the results showed a metal purity of 6N.

[0021] Specifically, Example 2 of this invention provides a precursor for a high-purity tungsten complex, wherein the precursor is (MeO)₂W₂(NMe₂)₄. Two tungsten atoms (W) are connected by direct metal-metal bonds (WW), four dimethylamino ligands (-NMe₂) are attached to each tungsten atom (two ligands), and two methoxy ligands (-OMe) are attached to each tungsten atom (one ligand). Molecular formula: W₂C 10 H 30 N4O2, structural formula as follows: .

[0022] The synthesis method used was the same as in Example 1, except that potassium tert-butoxide was replaced with an equimolar amount of sodium tert-butoxide (15.8 g, 0.164 mol). The final product obtained was a pale yellow product (MeO)₂W₂(NMe₂)₄, 44.4 g, with a yield of 92%.

[0023] Specifically, Example 3 of this invention provides a high-purity tungsten complex precursor and its synthesis method, which is the same as Example 1, except that potassium tert-butoxide is replaced with an equimolar amount of sodium methoxide (8.9 g, 0.164 mol).

[0024] 1 H NMR spectrum as shown Figure 3 As shown, the saturation values ​​were 3.45 (s, 24 H) and 3.22 (s, 6 H). The purity of the product was determined using inductively coupled plasma mass spectrometry (ICP-MS), and the results showed a metal purity of 6N.

[0025] Specifically, Example 4 of this invention provides a high-purity tungsten complex precursor and its synthesis method, which is the same as Example 1, except that the intermediate purification method is changed to sublimation. That is, anhydrous and oxygen-free filtration is performed, the filtrate is first washed with n-hexane, and then the washed filtrate is dried and sublimated to obtain 65.6 g of orange-red crystals (Me2N)4W2Cl2, with a yield of 85%.

[0026] Specifically, Comparative Example 1 of the present invention provides a high-purity tungsten complex precursor and its synthesis method, which is the same as Example 1, except that potassium tert-butoxide is replaced with an equimolar amount of tert-butanol (12.2 g, 0.164 mol) and triethylamine (16.2 g, 0.16 mol) is added as an acid-binding agent.

[0027] Under nitrogen atmosphere, (Me₂N)₄W₂Cl₂ intermediate (49.2 g, 0.08 mol) and 800 mL of n-hexane were added to a 2000 mL reaction flask. The mixture was cooled to 0 °C, and tert-butanol (12.2 g, 0.164 mol) and triethylamine (16.2 g, 0.16 mol) were added in portions. After the addition was complete, the mixture was slowly brought back to room temperature and stirred for 12 h. The mixture was then filtered through anhydrous and oxygen-free channels. The filtrate was first washed with n-hexane, and then the solvent in the washed filtrate was evaporated. The crude product was further distilled to obtain a pale yellow product (tBuO)₂W₂(NMe₂)₄, 36.4 g, with a yield of 66%. The purity of the product was analyzed by inductively coupled plasma mass spectrometry (ICP-MS), and the results showed that the metal purity of the product was 5N.

[0028] Comparative Example 1 shows that even with the addition of the organic base triethylamine, the neutral alcohol (tert-butanol) cannot react efficiently with the intermediate (Me₂N)₄W₂Cl₂. Therefore, the use of pre-prepared, highly reactive alkoxides as reactants is a key technical feature for achieving high-yield and high-purity synthesis in this invention. Alkoxides provide a high concentration of nucleophiles, avoiding time-consuming equilibrium reaction steps and ensuring the reaction proceeds rapidly and completely.

[0029] The specific analysis is as follows: In the reaction of (Me₂N)₄W₂Cl₂ + alkoxides, the alkoxide anion is a very strong nucleophile, which can directly and efficiently replace chlorine atoms, resulting in a rapid, complete, and high-yield reaction. In the comparative example, the reaction of (Me₂N)₄W₂Cl₂ + alcohol + amine is an equilibrium reaction, in which triethylamine acts as a base, first undergoing proton exchange with tert-butanol to generate a very small amount of tert-butanol anion in situ, and then the substitution reaction occurs. Because tert-butanol is a very weak acid, the conversion rate of this equilibrium is limited, resulting in a slow reaction rate, low efficiency, and low yield.

[0030] This invention uses tungsten tetrachloride ethylene glycol dimethyl ether adduct as the tungsten source and dimethylamine, a conventional industrial reagent, as the amine source, resulting in raw material costs far lower than those of N-tert-butyltrimethylsilylamine used in existing technologies. More importantly, the in-situ generation of dimethylaminolithium from dimethylamine and n-butyllithium fundamentally avoids the severe exothermic reaction and safety hazards associated with the direct use of solid dimethylaminolithium in existing technologies. The concentration of dimethylaminolithium generated in situ is controllable within the system, and the reaction process is gentle and controllable, making it more suitable for industrial scale-up. Furthermore, the entire synthesis requires only two reaction steps to obtain the target product, significantly simplifying the process and increasing the overall yield to over 68% compared to the three-step method disclosed in existing technologies (each step requires separation of intermediates).

[0031] The key raw materials involved in this invention patent are referenced in Dalton Transactions (2022), 51(20), 7856-7863. Other conventional raw materials or reagents are commercially available.

[0032] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in the details for the sake of brevity.

[0033] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A high-purity tungsten complex precursor, characterized in that, The precursor structure is shown in general formula (Ⅰ): (RO)2W2(NMe2)4 (Ⅰ) Wherein, R is a C1~C6 alkyl group.

2. The precursor according to claim 1, characterized in that, In the precursor, R is one of methyl, tert-butyl, and tert-butyl isomers.

3. The precursor according to claim 1, characterized in that, The precursor is one of (MeO)2W2(NMe2)4, (tBuO)2W2(NMe2)4, and its (tBuO)2W2(NMe2)4 isomer.

4. The precursor according to claim 1, characterized in that, The precursor has a metal purity of 6N.

5. A method for synthesizing a precursor of the high-purity tungsten complex according to claims 1-4, characterized in that, Includes the following steps: (1) Under an inert atmosphere, an organic lithium solution is added dropwise to an organic solution of dimethylamine at low temperature and the reaction is carried out for at least 2 hours to obtain a dimethylamine-based lithium system; (2) Add tungsten tetrachloride ethylene glycol dimethyl ether adduct to the dimethylamine lithium system and react for at least 2 hours. Then add trimethylchlorosilane to the system and continue the reaction for at least 12 hours. After separation and purification, the intermediate (Me2N)4W2Cl2 is obtained. (3) Under an inert atmosphere, the (Me2N)4W2Cl2 is dissolved in an organic solvent to obtain an organic solution of (Me2N)4W2Cl2. Then, an alkoxide is added to the organic solution of (Me2N)4W2Cl2 at low temperature. After reacting for at least 12 hours, the solution is separated and purified to obtain (RO)2W2(NMe2)4.

6. The synthesis method according to claim 5, characterized in that, The structure of the alkoxide is as follows: ROM, where R is a C1-C6 alkyl group and M is an alkali metal.

7. The synthesis method according to claim 5, characterized in that, The organic lithium solution is a n-butyllithium n-hexane solution, the organic solution of dimethylamine is a dimethylamine n-hexane solution, the organic solvent is n-hexane, and the molar ratio of n-butyllithium to dimethylamine is 1:(1~1.2).

8. The synthesis method according to claim 7, characterized in that, The molar ratio of the tungsten tetrachloride ethylene glycol dimethyl ether adduct to n-butyllithium and trimethylchlorosilane is 1:(2~4):(1~1.2).

9. The synthesis method according to claim 5, characterized in that, The molar ratio of the (Me2N)4W2Cl2 intermediate to the alkoxide is 1:(2~2.1).

10. The synthesis method according to claim 5, characterized in that, The reaction temperature is -20~10℃.

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