A process for the preparation of bis(dimethylamino-2-methyl-2-butoxy) nickel

Abstract

The application discloses a preparation method of bis(dimethylamino-2-methyl-2-butoxy) nickel, sodium amide is used to replace sodium hydride as a salting reagent, and bis(dimethylamino-2-methyl-2-butoxy) nickel is prepared through coordination reaction of nickel chloride and dimethylamino-2-methyl-2-butanol; the nuclear magnetic purity of the obtained product can reach more than 99%, and the total yield is stably more than 85%. The method can avoid hydrogen generation, the reaction condition is mild and controllable, the obtained product has high purity, impurities are easy to remove, batch stability is good, and the method is easy to realize industrial amplification production, can meet the high-purity application requirement of semiconductor ALD precursors, and has wide industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of organometallic compound preparation technology, specifically to a method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel. Background Technology

[0002] Bis(dimethylamino-2-methyl-2-butoxy)nickel (CAS: 942311-35-5) is a liquid nickel precursor used for atomic layer deposition (ALD) or chemical vapor deposition (CVD) in semiconductors. It has the characteristics of excellent volatility, moderate decomposition temperature, excellent step coverage, and low coating impurities. It is widely used in nickel metal gates, nickel barrier layers, and nickel electrode thin film deposition in integrated circuits.

[0003] In existing technologies, the preparation of this compound generally employs sodium hydride as a basic deprotonating agent, followed by ligand salt formation and then coordination reaction with nickel chloride, forming a synthetic route of "ligand salt formation-metal salt coordination." The reaction equation is as follows: Although this route can synthesize the target product under laboratory conditions, it has the following drawbacks: First, the salt formation reaction quantitatively generates hydrogen gas, which is flammable and explosive. In a closed reaction system and with organic solvent vapors present, it can easily form an explosive mixture, posing a high safety risk and making it difficult to control and achieve stable scale-up production. Second, the reaction between sodium hydride and the ligand dimethylamino-2-methyl-2-butanol (dmambH) is highly exothermic, and the reaction rate is difficult to control precisely. Local overheating can easily lead to ligand decomposition, generating amines and olefins, reducing product purity and yield, and increasing the difficulty of subsequent purification. Third, trace amounts of hydride are easily left after the sodium hydride reaction. During coordination with nickel chloride, these can easily form nickel hydrides and other difficult-to-remove impurities. Conventional distillation and filtration methods are ineffective in removing these impurities, resulting in a high content of metallic impurities and decreased thermal stability in the product, affecting the quality of ALD coatings. Fourth, existing processes suffer from poor batch stability, with significant fluctuations in salt conversion rate and impurity content between different batches, resulting in insufficient consistency in product purity and yield, making it difficult to meet the stringent requirements of semiconductor electronic-grade materials. Therefore, there is an urgent need to develop a safe, controllable, easily impurity-removable, high-purity, stable-yield, and industrially scaleable method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing sodium hydride salt-forming routes, such as high safety risks, violent and difficult-to-control reactions, high impurity content, and poor batch stability, and to provide a method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel. This invention uses sodium amide instead of sodium hydride as the salt-forming reagent, and prepares bis(dimethylamino-2-methyl-2-butoxy)nickel through the coordination reaction of nickel chloride with dimethylamino-2-methyl-2-butanol. This method avoids hydrogen generation, provides mild and controllable reaction conditions, yields high-purity products with easily removed impurities, good batch stability, and is easy to scale up for industrial production. It can meet the high-purity application requirements of semiconductor ALD precursors and has broad industrial application prospects.

[0005] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0006] A method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel includes the following steps:

[0007] (1) Under the protection of an inert gas, sodium amide is dispersed in an organic solvent at 0-8 °C, and 1-dimethylamino-2-methyl-2-butanol is added to react for 1-2 h. The temperature is raised to 25-30 °C and kept at a constant temperature for 2-3 h. During the reaction, the generated ammonia gas is continuously removed to obtain a sodium 1-dimethylamino-2-methyl-2-butanol solution.

[0008] (2) Under the protection of an inert gas, add sodium 1-dimethylamino-2-methyl-2-butoxide solution obtained in step (1) to the suspension formed by nickel chloride and organic solvent at -10 ℃ to 0 ℃, react at 0-10 ℃ for 3-5 h, and then heat to 45-55 ℃ for constant temperature aging for 6-9 h to obtain crude reaction solution;

[0009] (3) Filter to remove sodium chloride from the crude reaction solution obtained in step (2), collect the organic filtrate; remove the organic solvent from the organic filtrate to obtain the crude product; purify the crude product to obtain the bis(dimethylamino-2-methyl-2-butoxy)nickel.

[0010] This invention uses sodium amide (NaNH2) as a mild deprotonating agent, which reacts with 1-dimethylamino-2-methyl-2-butanol (dmambH) in an acid-base reaction to generate sodium 1-dimethylamino-2-methyl-2-butoxide (dmambNa) and ammonia (NH3). The reaction is exothermic and gradual, with no hydrogen generation. Subsequently, sodium 1-dimethylamino-2-methyl-2-butoxide undergoes a biligand chelate coordination reaction with nickel chloride (NiCl2) to generate the target product bis(dimethylamino-2-methyl-2-butoxy)nickel (Ni(dmamb)2) and sodium chloride (NaCl) as a byproduct. The overall reaction equation is as follows: This invention achieves stable preparation of high-purity product Ni(dmamb)2 by continuously removing ammonia during the reaction process and precisely controlling the reaction temperature and heating rate, effectively suppressing side reactions.

[0011] Furthermore, in step (1), all raw materials and reaction apparatus are dehydrated and deoxygenated before the reaction, and the water content and oxygen content in the raw materials and apparatus are controlled to be <1 ppm.

[0012] Further, in step (1), the inert gas is nitrogen; the organic solvent is tetrahydrofuran.

[0013] Further, in step (1), the stirring rate of the sodium amino group dispersed in the organic solvent is 150-200 r / min.

[0014] Furthermore, in step (1), the 1-dimethylamino-2-methyl-2-butanol is added dropwise at a rate of 3-6 mL / min. Using a dropwise addition method allows for precise control of the reaction rate, avoiding concentrated exothermic reactions caused by a large, instantaneous reaction.

[0015] Furthermore, in step (1), the heating rate to 25-30 °C is 0.5-1 °C / min. Using a slow gradient heating can avoid a sudden rise in system temperature and prevent local overheating that could lead to ligand decomposition and ammonia boiling.

[0016] Furthermore, in step (1), the ammonia gas generated is removed using a combination of micro-negative pressure and micro-purging with nitrogen gas. The micro-negative pressure is -0.02 MPa to -0.04 MPa. The removed ammonia gas is absorbed and treated with dilute sulfuric acid to generate ammonium sulfate as a byproduct, thus avoiding environmental pollution.

[0017] In a specific embodiment, in step (1), under nitrogen protection, anhydrous tetrahydrofuran is added to the reaction flask, the temperature is controlled at 0-10 ℃ in a low-temperature bath, sodium amino solid is added and stirred at a low speed of 150-200 r / min to make it uniformly dispersed, and then 1-dimethylamino-2-methyl-2-butanol is slowly added dropwise at a rate of 3-6 mL / min through a dropping funnel, controlling the system temperature not to exceed 8 ℃ to avoid instantaneous exothermic reaction; after the addition is completed, the reaction is kept at 0-8 ℃ for 1-2 h, and a micro negative pressure of -0.02 MPa ~ -0.04 MPa is turned on simultaneously and a small amount of nitrogen is introduced to purge and continuously remove the ammonia gas generated in the reaction (ammonia gas can be treated by absorption with dilute sulfuric acid). Then, the temperature is gradually increased to 25-30 ℃ at a rate of 0.5-1 ℃ / min and kept at a constant temperature for 2-3 h until no ammonia gas overflows, confirming that the ligand is completely converted into dmambNa, and a clear and transparent dmambNa solution is obtained.

[0018] Further, in step (2), the inert gas is nitrogen; the organic solvent is tetrahydrofuran.

[0019] Further, in step (2), the stirring rate of the nickel chloride suspended in the organic solvent is 300-350 r / min.

[0020] Furthermore, in step (2), the rate of heating to 45-55 °C is 0.3-0.5 °C / min. Initially, the coordination reaction is carried out at a low temperature to suppress the formation of single-ligand products, while the temperature is slowly increased to a temperature that promotes the complete chelation reaction of the two ligands.

[0021] Furthermore, in step (2), the sodium 1-dimethylamino-2-methyl-2-butoxide solution is added dropwise, and the system temperature is controlled not to exceed 0 °C during the dropwise addition process.

[0022] In a specific embodiment, in step (2), another reaction flask that has been treated to remove water and oxygen is taken, and anhydrous nickel chloride and anhydrous tetrahydrofuran are added. The temperature is controlled at -10 ℃ to 0 ℃ in a low-temperature bath, and the anhydrous nickel chloride is uniformly suspended by high-speed stirring at 300-350 r / min. Under nitrogen protection, the mixture is stirred at low temperature, and 1-dimethylamino-2-methyl-2-butoxide sodium solution is slowly added dropwise while controlling the temperature not to exceed 0 ℃. After the addition is completed, the mixture is kept at 0-10 ℃ for 3-5 h, and then the temperature is increased to 45-55 ℃ at a rate of 0.3-0.5 ℃ / min for constant temperature aging for 6-9 h, so as to promote the directional double ligand chelation coordination reaction between 1-dimethylamino-2-methyl-2-butoxide sodium and anhydrous nickel chloride, and a dark brown crude reaction solution of bis(dimethylamino-2-methyl-2-butoxy) nickel is obtained.

[0023] Further, in steps (1) and (2), the molar ratio of nickel chloride, 1-dimethylamino-2-methyl-2-butanol and sodium amino group is 1:(2.0-2.4):(2.0-2.2).

[0024] Furthermore, in step (3), the filtration is carried out through a sand core filter under full nitrogen positive pressure protection.

[0025] Furthermore, in step (3), the removal of organic solvent is carried out by vacuum distillation at a distillation temperature of 40-50℃ and a vacuum degree of -0.08 MPa ~ -0.095 MPa.

[0026] Furthermore, in step (3), the purification process employs short-path molecular distillation under nitrogen protection and a vacuum of 1×10⁻⁶. -3 Pa ~ 5×10 -3 The process is carried out under the conditions of Pa, with a distillation temperature of 95-115 ℃ and a condensation temperature of -10 ℃ to 0 ℃.

[0027] In a specific embodiment, in step (3), under nitrogen positive pressure protection throughout the process, the crude reaction liquid is filtered through a pre-treated sand core filter to prevent the filtrate from contacting air and water vapor, removing the byproduct sodium chloride solid and collecting the organic filtrate; the filtrate is then transferred to a vacuum distillation apparatus, where tetrahydrofuran is removed under nitrogen protection at 40-50 ℃ and -0.08 MPa ~ -0.095 MPa to avoid thermal decomposition of the product, yielding a brown liquid crude product; the crude product is then transferred to a molecular distillation apparatus, where tetrahydrofuran is removed under nitrogen protection and 1×10 -3 Pa ~ 5×10 -3 Under high vacuum conditions, short-path molecular distillation was carried out by controlling the distillation temperature at 95-115 ℃ and the condensation temperature at -10 ℃ to 0 ℃ to separate trace impurities such as free ligands and high-boiling impurities. The target main fraction was collected to obtain high-purity bis(dimethylamino-2-methyl-2-butoxy)nickel.

[0028] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0029] 1. This invention replaces sodium hydride with sodium amino acid as the salt-forming reagent, replacing the flammable and explosive hydrogen gas as a byproduct of the salt-forming reaction with easily handled ammonia gas, thus eliminating the risk of combustion and explosion caused by hydrogen gas. At the same time, sodium amino acid is less alkaline than sodium hydride, significantly reducing the exothermic enthalpy change of the reaction. The reaction process is mild and controllable, without the risk of local overheating and material overflow, making it suitable for industrial-scale production and solving the core safety problem of existing processes.

[0030] 2. The sodium amide used in this invention has a mild reaction, which effectively inhibits the thermal decomposition of ligands and reduces the generation of organic impurities. During the reaction, ammonia is continuously removed by micro-negative pressure combined with nitrogen purging, resulting in no residual pollution. The NMR purity of the obtained product can reach more than 99%, and the total yield is stable at more than 85%, which is far superior to the 70%-82% yield and NMR purity of less than 99% of the existing sodium hydride route.

[0031] 3. Impurities are easily removed in the preparation method of this invention. The reaction only produces two byproducts: solid sodium chloride and ammonia. Sodium chloride can be directly removed by filtration, and ammonia can be removed by micro-negative pressure purging. Impurities such as nickel hydride and polynuclear nickel, which are difficult to remove in existing processes, will not be introduced. Combined with subsequent low-temperature vacuum distillation and short-path molecular distillation purification, residual solvent, free ligands and high-boiling-point impurities can be effectively separated. The metal impurity content of the final product is less than 1 ppm, which meets the requirements of semiconductor electronic-grade materials.

[0032] 4. This invention has excellent industrial feasibility and batch stability. The process operation conditions are mild and the temperature control is easy. No special high-pressure or explosion-proof equipment is required. All raw materials used are commercially available industrial-grade reagents with low cost. The purity and yield of the products vary very little between different batches, and the batch consistency is good, which can realize large-scale continuous production.

[0033] 5. The bis(dimethylamino-2-methyl-2-butoxy)nickel prepared by this invention has excellent volatility and thermal stability, which is fully compatible with the deposition requirements of semiconductor ALD / CVD nickel metal gate, nickel barrier layer and nickel electrode film. It can effectively improve the uniformity and electrical performance of the coating and has extremely high industrial application value. Attached Figure Description

[0034] Figure 1 The image shows the 1H NMR spectrum of bis(dimethylamino-2-methyl-2-butoxy)nickel prepared in Example 1.

[0035] Figure 2 The image shows the 1H NMR spectrum of bis(dimethylamino-2-methyl-2-butoxy)nickel prepared in Comparative Example 1. Detailed Implementation

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0038] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0039] In the following examples, the raw materials 1-dimethylamino-2-methyl-2-butanol (dmambH, GC purity ≥99%), sodium amide (NaNH2, anhydrous grade), anhydrous nickel chloride (NiCl2, high purity anhydrous, water content 8 ppm) and solvent anhydrous tetrahydrofuran (THF, molecular sieve dried, water content <5 ppm) were all dehydrated and deoxygenated in a nitrogen glove box to ensure that the water and oxygen contents of each raw material were <1 ppm. The reaction apparatus (reaction flask, condenser, dropping funnel, filter) was preheated to 120 °C under vacuum for 2 h and purged with nitrogen three times to ensure that the water and oxygen contents in the apparatus were <1 ppm.

[0040] Example 1

[0041] A method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel includes the following steps:

[0042] (1) Under nitrogen protection, 200 mL of anhydrous tetrahydrofuran was added to the reaction flask and placed in an ice-water bath at 5 °C. 12.87 g (0.33 mol) sodium amide solid was added and stirred at a low speed of 180 r / min to disperse it evenly. Then, 47.24 g (0.36 mol) of 1-dimethylamino-2-methyl-2-butanol was slowly added dropwise at a rate of 4.5 mL / min through a dropping funnel. The system temperature was controlled not to exceed 8 °C to avoid instantaneous exothermic reaction. After the addition was completed, the reaction was kept at 5 °C for 1.5 h. Simultaneously, a micro negative pressure of -0.03 MPa was turned on and a small amount of nitrogen was introduced to purge and continuously remove the ammonia generated in the reaction (ammonia can be absorbed by dilute sulfuric acid). Then, the temperature was gradually increased to 28 °C at a rate of 0.8 °C / min and kept constant for 2.5 h until no ammonia was released, and a clear and transparent sodium 1-dimethylamino-2-methyl-2-butanol solution was obtained.

[0043] (2) Take another reaction flask that has been dehydrated and deoxygenated, add 19.4 g (0.15 mol) of anhydrous nickel chloride and 100 mL of anhydrous tetrahydrofuran, place it in a -5 ℃ low temperature bath, and stir at 320 r / min to suspend the anhydrous nickel chloride evenly; stir at low temperature under nitrogen protection, slowly add sodium 1-dimethylamino-2-methyl-2-butoxide solution and control the temperature not to exceed 0 ℃; after the addition is completed, keep the reaction at 5 ℃ for 4 h, and then raise the temperature to 50 ℃ at a rate of 0.4 ℃ / min and keep it at a constant temperature for 7 h to obtain a dark brown crude reaction solution of bis(dimethylamino-2-methyl-2-butoxy) nickel.

[0044] (3) Under nitrogen positive pressure protection throughout the process, the crude reaction liquid is filtered through a pre-treated sand core filter to prevent the filtrate from contacting air and water vapor, removing the byproduct sodium chloride solid and collecting the organic filtrate; the filtrate is transferred to a vacuum distillation apparatus, and tetrahydrofuran is removed under nitrogen protection at 45 ℃ and -0.09 MPa to avoid thermal decomposition of the product, yielding a brown liquid crude product; the crude product is then transferred to a molecular distillation apparatus, and under nitrogen protection and 2×10 -3 Under high vacuum conditions (Pa), short-path molecular distillation was performed at a distillation temperature of 95 °C and a condensation temperature of 0 °C to separate trace impurities such as free ligands and high-boiling impurities. The target main fraction was collected to obtain 41.9 g of high-purity bis(dimethylamino-2-methyl-2-butoxy)nickel, with a yield of 87.54%. The NMR purity of the product was 99.36%, and the NMR spectrum is shown below. Figure 1 As shown; ICP-MS detection showed metal impurities <1 ppm, metal purity reached 6N (≥99.9999%); the product at 25℃ was a brown transparent liquid; the NMR data of the product were: 1 H NMR (500 MHz, C6D6) 0.93(t,6H), 1.35(d,6H), 1.65(m,4H), 1.81(m,4H), 2.29(d,6H), 2.38(d,6H).

[0045] Example 2

[0046] A method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel includes the following steps:

[0047] (1) Under nitrogen protection, 200 mL of anhydrous tetrahydrofuran was added to the reaction flask and placed in an ice-water bath at 8 °C. 12.285 g (0.315 mol) sodium amide solid was added and stirred at a low speed of 180 r / min to disperse it evenly. Then, 47.24 g (0.36 mol) of 1-dimethylamino-2-methyl-2-butanol was slowly added dropwise at a rate of 4.5 mL / min through a dropping funnel. The system temperature was controlled not to exceed 8 °C to avoid instantaneous exothermic reaction. After the addition was completed, the reaction was kept at 8 °C for 2 h. Simultaneously, a micro negative pressure of -0.02 MPa was turned on and a small amount of nitrogen was introduced to purge and continuously remove the ammonia generated in the reaction (ammonia can be absorbed by dilute sulfuric acid). Then, the temperature was gradually increased to 30 °C at a rate of 0.8 °C / min and kept at a constant temperature for 2 h until no ammonia was released, and a clear and transparent sodium 1-dimethylamino-2-methyl-2-butanol solution was obtained.

[0048] (2) Take another reaction flask that has been dehydrated and deoxygenated, add 19.4 g (0.15 mol) of anhydrous nickel chloride and 100 mL of anhydrous tetrahydrofuran, place it in a 0 ℃ low temperature bath, and stir at 320 r / min to suspend the anhydrous nickel chloride evenly; stir at low temperature under nitrogen protection, slowly add sodium 1-dimethylamino-2-methyl-2-butoxide solution and control the temperature not to exceed 0 ℃; after the addition is completed, keep the reaction at 10 ℃ for 3 h, and then raise the temperature to 55 ℃ at a rate of 0.4 ℃ / min and keep it at a constant temperature for 6 h to obtain a dark brown crude reaction solution of bis(dimethylamino-2-methyl-2-butoxy) nickel.

[0049] (3) Under nitrogen positive pressure protection throughout the process, the crude reaction liquid is filtered through a pre-treated sand core filter to prevent the filtrate from contacting air and water vapor, removing the byproduct sodium chloride solid and collecting the organic filtrate; the filtrate is transferred to a vacuum distillation apparatus, and tetrahydrofuran is removed under nitrogen protection at 45 ℃ and -0.09 MPa to avoid thermal decomposition of the product, yielding a brown liquid crude product; the crude product is then transferred to a molecular distillation apparatus, and under nitrogen protection and 5×10 -3 Under high vacuum conditions (Pa), short-path molecular distillation was performed at a distillation temperature of 100 °C and a condensation temperature of -5 °C to separate trace impurities such as free ligands and high-boiling impurities. The target main fraction was collected to obtain 41.9 g of high-purity bis(dimethylamino-2-methyl-2-butoxy)nickel, with a yield of 87.1%. The NMR purity of the product was 99.15%, and ICP-MS analysis showed that the metal impurities were <1 ppm, with a metal purity of 6N (≥99.9999%). The NMR data of the product are as follows: 1 H NMR (400 MHz, C6D6) 0.93(t,6H), 1.35(d,6H), 1.65(m,4H), 1.81(m,4H), 2.29(d,6H), 2.38(d,6H).

[0050] Example 3

[0051] A method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel is basically the same as that in Example 1, except that: in step (1), 200 mL of anhydrous tetrahydrofuran is replaced with 2000 mL of anhydrous tetrahydrofuran, 12.87 g (0.33 mol) sodium amide is replaced with 128.7 g (3.3 mol) sodium amide, 47.24 g (0.36 mol) 1-dimethylamino-2-methyl-2-butanol is replaced with 472.4 g (3.6 mol) 1-dimethylamino-2-methyl-2-butanol, and the reaction flask is replaced with a 5 L reaction vessel; in step (2), 19.4 g (0.15 mol) of anhydrous nickel chloride is replaced with 194 g (1.5 mol) of anhydrous nickel chloride, 100 mL of anhydrous tetrahydrofuran is replaced with 1000 mL of anhydrous tetrahydrofuran, and the reaction flask is replaced with a 5 L reaction vessel.

[0052] 417.8 g of high-purity bis(dimethylamino-2-methyl-2-butoxy)nickel was finally obtained, with a yield of 87.2%; the NMR purity of the product was 99.32%, and ICP-MS analysis showed that the metal impurities were <1 ppm, with a metal purity of 6N (≥99.9999%); the NMR data of the product are as follows: 1 ¹H NMR (400 MHz, C₆D₆) 0.93(t, ₆H), 1.35(d, ₆H), 1.65(m, ₄H), 1.81(m, ₄H), 2.29(d, ₆H), 2.38(d, ₆H). The preparation method of this invention exhibits good batch stability, eliminates the risk of material spillage and explosion, and meets the requirements for industrial production.

[0053] Comparative Example 1

[0054] A method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel includes the following steps:

[0055] (1) Under nitrogen protection, 200 mL of anhydrous tetrahydrofuran was added to the reaction flask and placed in an ice-water bath at 5 °C. 7.92 g (0.33 mol) of sodium hydride solid was added and stirred at a low speed of 180 r / min to disperse it evenly. Then, 47.24 g (0.36 mol) of 1-dimethylamino-2-methyl-2-butanol was slowly added dropwise at a rate of 4.5 mL / min through a dropping funnel. The system temperature was controlled not to exceed 8 °C to avoid instantaneous exothermic reaction. After the addition was completed, the reaction was kept at 5 °C for 1.5 h. Simultaneously, a micro negative pressure of -0.03 MPa was turned on and a small amount of nitrogen was introduced to purge and continuously remove the hydrogen generated in the reaction. Then, the temperature was gradually increased to 28 °C at a rate of 0.8 °C / min and kept constant for 2.5 h until no hydrogen was released, and a clear and transparent sodium 1-dimethylamino-2-methyl-2-butanol solution was obtained.

[0056] (2) Take another reaction flask that has been dehydrated and deoxygenated, add 19.4 g (0.15 mol) of anhydrous nickel chloride and 100 mL of anhydrous tetrahydrofuran, place it in a -5 ℃ low temperature bath, and stir at 320 r / min to suspend the anhydrous nickel chloride evenly; stir at low temperature under nitrogen protection, slowly add sodium 1-dimethylamino-2-methyl-2-butoxide solution and control the temperature not to exceed 0 ℃; after the addition is completed, keep the reaction at 5 ℃ for 4 h, and then raise the temperature to 50 ℃ at a rate of 0.4 ℃ / min and keep it at a constant temperature for 7 h to obtain a dark brown crude reaction solution of bis(dimethylamino-2-methyl-2-butoxy) nickel.

[0057] (3) Under the protection of nitrogen positive pressure throughout the process, the crude reaction liquid is filtered through a sand core filter device that has been pre-treated for dehydration and deoxygenation to avoid contact between the filtrate and air and water vapor, remove the by-product sodium chloride solid and collect the organic filtrate; the filtrate is transferred to a vacuum distillation device, and tetrahydrofuran is removed under low temperature vacuum at 45 ℃ and -0.09 MPa under nitrogen protection to avoid thermal decomposition of the product, and a brown liquid crude product is obtained; the crude product is then transferred to a molecular distillation device, and short-path molecular distillation is carried out under nitrogen protection and 2×10-3 Pa high vacuum conditions, with the distillation temperature controlled at 95 ℃ and the condensation temperature at 0 ℃, to separate free ligands, high-boiling impurities and other trace impurities, collect the target main fraction, and obtain 33.17 g of high-purity bis(dimethylamino-2-methyl-2-butoxy)nickel.

[0058] The product obtained in Comparative Example 1 had a yield of 69.31% and an NMR purity of 98.34%, as shown in the NMR spectrum. Figure 2 As shown, the product exhibits a small impurity peak at 2.09 ppm, and ICP-MS analysis revealed metal impurities >1 ppm. The reaction process involved vigorous hydrogen release and localized overheating of the system, leading to slight ligand decomposition and posing a risk of material spillage.

[0059] Comparative Example 2

[0060] A method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel is basically the same as that in Example 1, except that in step (1), the ammonia gas is not removed by turning on the micro negative pressure, but is simply allowed to stand naturally to remove the ammonia.

[0061] The product yield of Comparative Example 2 was 73.2%, and the NMR purity was 98.85%. Trace amounts of residual ammonia formed complexes with the ligands, reducing the product yield and failing to meet the purity requirements for ALD precursors.

[0062] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing bis(dimethylamino-2-methyl-2-butoxy)nickel, characterized in that, Includes the following steps: (1) Under the protection of an inert gas, sodium amide is dispersed in an organic solvent at 0-8 °C, and 1-dimethylamino-2-methyl-2-butanol is added to react for 1-2 h. The temperature is raised to 25-30 °C and kept at a constant temperature for 2-3 h. During the reaction, the generated ammonia gas is continuously removed to obtain a sodium 1-dimethylamino-2-methyl-2-butanol solution. (2) Under the protection of an inert gas, add sodium 1-dimethylamino-2-methyl-2-butoxide solution obtained in step (1) to the suspension formed by nickel chloride and organic solvent at -10 ℃ to 0 ℃, react at 0-10 ℃ for 3-5 h, and then heat to 45-55 ℃ for constant temperature aging for 6-9 h to obtain crude reaction solution; (3) Filter to remove sodium chloride from the crude reaction solution obtained in step (2), collect the organic filtrate; remove the organic solvent from the organic filtrate to obtain the crude product; purify the crude product to obtain the bis(dimethylamino-2-methyl-2-butoxy)nickel. In steps (1) and (2), the molar ratio of nickel chloride, 1-dimethylamino-2-methyl-2-butanol and sodium amino group is 1:(2.0-2.4):(2.0-2.2).

2. The preparation method according to claim 1, characterized in that, In step (1), the inert gas is nitrogen; the organic solvent is tetrahydrofuran.

3. The preparation method according to claim 1, characterized in that, In step (1), the 1-dimethylamino-2-methyl-2-butanol is added dropwise at a rate of 3-6 mL / min.

4. The preparation method according to claim 1, characterized in that, In step (1), the rate of heating to 25-30 ℃ is 0.5-1 ℃ / min.

5. The preparation method according to claim 1, characterized in that, In step (1), the ammonia gas generated is removed by a combination of micro-negative pressure and nitrogen micro-purging. The pressure of the micro-negative pressure is -0.02 MPa ~ -0.04 MPa.

6. The preparation method according to claim 1, characterized in that, In step (1), the stirring rate of the sodium amino group dispersed in the organic solvent is 150-200 r / min; in step (2), the stirring rate of the nickel chloride suspended in the organic solvent is 300-350 r / min.

7. The preparation method according to claim 1, characterized in that, In step (2), the rate of heating to 45-55 ℃ is 0.3-0.5 ℃ / min.

8. The preparation method according to claim 1, characterized in that, In step (3), the organic solvent is removed by vacuum distillation at a temperature of 40-50 ℃ and a vacuum of -0.08 MPa ~ -0.095 MPa.

9. The preparation method according to claim 1, characterized in that, In step (3), the purification process employs short-path molecular distillation under nitrogen protection and a vacuum of 1×10⁻⁶. -3 Pa ~ 5×10 -3 The process is carried out under the conditions of Pa, with a distillation temperature of 95-115 ℃ and a condensation temperature of -10 ℃ to 0 ℃.

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