Preparation method of tris (ethyl methyl amino) tert-butylamide niobium

Abstract

The invention relates to a preparation method of tris (ethyl methyl amino) tert-butylamide niobium, which comprises the following steps: (1) reacting niobium pentachloride, ethylene glycol dimethyl ether, zinc chloride and tert-butylamine to obtain a niobium-based complex; and (2) reacting the niobium-based complex with methyl ethyl amino lithium to obtain the tri (ethyl methyl amino) tert-butylamide niobium. By optimizing the preparation method of tris (ethyl methyl amino) tert-butylamide niobium in the prior art, the method has the advantages of simple and easily available raw materials, avoidance of the use of toxic and harmful reagents such as pyridine and toluene, simple reaction steps, mild reaction conditions, high reaction speed, no need of extremely high-temperature or low-temperature environment, high yield and high yield, and the product can be obtained by only two steps. And the obtained target product has high yield and purity, and is beneficial to industrial large-scale production.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for preparing niobium tri(ethylmethylamino)tert-butamide. Background Technology

[0002] With the development of semiconductor device manufacturing technology, high-performance niobium-based thin films are playing an increasingly important role in modern semiconductor devices, becoming a cornerstone for achieving breakthroughs in device performance. For example, Nb₂O₅ thin films formed from niobium-based precursors have high dielectric constants, which can increase storage density when applied to memory capacitors; when applied to high-k gate dielectric layers in logic devices, they can use a thicker physical thickness while maintaining the same gate control capability, thus significantly reducing gate leakage current. The preparation of niobium-based thin films mainly relies on atomic layer deposition (ALD) and chemical vapor deposition (CVD) technologies. These technologies place stringent requirements on niobium precursors, including good volatility, excellent thermal stability, high reactivity, and low impurity content in the manufactured films. However, existing mainstream precursors such as niobium halides (e.g., NbCl₅, which easily retains chlorine) and niobium alkoxy (e.g., Nb(OEt)₅, which has poor volatility and high carbon residue) have significant defects, making it difficult to simultaneously meet the above key performance indicators.

[0003] Compared to mainstream precursors, niobium tris(ethylmethylamino)tert-butamide not only avoids chlorine contamination, but the tert-butamide groups in its structure also enhance the thermal stability of the precursor. Furthermore, it produces thin films with low carbon impurity content when deposited via ALD. Currently, there are few reports on the synthesis of niobium tris(ethylmethylamino)tert-butamide.

[0004] Patent CN111440210A reports a i P r The synthesis method of N=Nb(NEt2)3 involves: (1) adding niobium pentachloride to a mixed solution of toluene and tetrahydrofuran to form system I; (2) adding diethylamine to form system II; (3) adding isopropylamine to form system III; (4) adding n-butyllithium to form system IV; (5) filtering and collecting the crude product; and (6) distilling to obtain the product. This method requires a total of six steps, is cumbersome, takes 20 hours, and uses toluene, a toxic reagent, which is harmful to human health and the environment. In the end, only 60% of the product is obtained.

[0005] Patent CN116854727A reports another synthetic method, which first reacts niobium pentachloride with Me3SiNMe2 to obtain solid Nb(NMe2)4Cl, and then purifies Nb(NMe2)4Cl by sublimation, followed by reaction with Me3SiNH t Bu reaction obtained tBuN=Nb(NMe2)3. In this scheme, Me3SiNMe2 and Me3SiNH... t Bu needs to be prepared separately, which is a complicated process. Furthermore, since the intermediate Nb(NMe2)4Cl is a solid, an additional sublimation step is required, which increases the experimental steps and is not conducive to industrial production.

[0006] Patent CN117659076A reports a method in which (1) niobium pentachloride is reacted with tert-butylamine in reactor 1; (2) pyridine is added to reactor 1 to form a niobium complex, and the reaction solution is filtered and concentrated; (3) n-butyllithium is reacted with diethylamine in reactor 2 to obtain diethylaminolithium; and (4) the filtrate is added to reactor 2 to obtain (tert-butylimide)tris(diethylamino)niobium. This method uses toxic pyridine and requires four steps to obtain the product, involving multiple temperature changes, which is time-consuming.

[0007] Therefore, there is currently no simple and efficient method for synthesizing niobium tris(ethylmethylamino)tert-butamide, which limits its industrial production. Thus, it is necessary to provide a convenient and efficient method for preparing niobium tris(ethylmethylamino)tert-butamide. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a method for preparing niobium tri(ethylmethylamino)tert-butanamide. This invention primarily optimizes existing methods for synthesizing niobium tri(ethylmethylamino)tert-butanamide by using ethylene glycol dimethyl ether and zinc chloride to replace pyridine, which has a complexing effect on niobium metal. This improves reaction efficiency, simplifies the synthetic route, and reduces the risk of the reaction. The reaction conditions are mild, resulting in high product yield and purity.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a method for preparing niobium tris(ethylmethylamino)tert-butamide, the method comprising the following steps:

[0011] (1) Niobium pentachloride, ethylene glycol dimethyl ether, zinc chloride and tert-butylamine react to give a niobium-based complex;

[0012] (2) The niobium-based complex reacts with methyl ethylamino lithium to obtain the tri(ethylmethylamino)tert-butamide niobium;

[0013] The synthetic route of the preparation method is as follows:

[0014] .

[0015] In this invention, the use of ethylene glycol dimethyl ether and zinc chloride avoids the need for pyridine, improves reaction efficiency, and reduces reaction hazards; the product can be obtained in only two steps, resulting in extremely high synthesis efficiency; simultaneously, all reaction steps do not require extremely low temperatures, 10℃~25℃ is sufficient, reducing energy consumption; furthermore, the complex formed between ethylene glycol dimethyl ether and niobium trichloro-tert-butylamide has low bond energy, higher reactivity, and a faster reaction rate. The preparation method provided by this invention has mild reaction conditions, yields high product yield and purity, and is beneficial for large-scale industrial production.

[0016] Preferably, the molar ratio of ethylene glycol dimethyl ether to niobium pentachloride in step (1) is (1-1.2):1 (for example, it can be 1:1, 1.05:1, 1.1:1, 1.15:1 or 1.2:1, etc.).

[0017] Preferably, the molar ratio of zinc chloride to niobium pentachloride in step (1) is (2-4):1 (for example, it can be 2:1, 2.1:1, 2.2:1, 2.5:1, 3:1 or 4:1, etc.), and more preferably (2-2.2):1.

[0018] Preferably, the molar ratio of tert-butylamine to niobium pentachloride in step (1) is (2.8 to 3.2):1 (for example, it can be 2.8:1, 3:1, 3.05:1, 3.1:1, 3.15:1 or 3.2:1, etc.), and more preferably (3 to 3.2):1.

[0019] In this invention, a specific molar ratio of tert-butylamine to niobium pentachloride is beneficial to improving the yield of the target product. The best technical effect is achieved when the molar ratio is (3-3.2):1. If the molar ratio is lower than 3:1, tert-butylamine cannot completely react with the generated hydrochloric acid to form tert-butylamine hydrochloride compound, resulting in an excessively high concentration of hydrochloric acid in the reaction system, which prevents the reaction from proceeding normally, reduces the product yield, and causes harm to the human body due to the volatilization of hydrochloric acid. If the molar ratio is higher than 3.2:1, it will cause waste of raw materials and increase the production cost of the product.

[0020] Preferably, the reaction in step (1) is carried out in the presence of a solvent.

[0021] Preferably, the solvent is a hydrocarbon solvent, preferably C5-C. 12 (For example, it could be C5, C8, C) 10 Or C 12 Alkanes, etc.

[0022] Preferably, the C5-C 12 The alkanes include any one or a combination of at least two of n-pentane, n-hexane or n-heptane, with n-hexane being more preferred.

[0023] The preferred hydrocarbon solvent used in this invention is n-hexane, which reduces reaction costs and is non-toxic to humans.

[0024] Preferably, the reaction specifically includes: mixing niobium pentachloride, ethylene glycol dimethyl ether, zinc chloride and solvent and cooling, then adding tert-butylamine to react and obtain a niobium-based complex.

[0025] Preferably, the mixing is carried out under stirring.

[0026] Preferably, the cooling is to a temperature of -30℃ to -10℃ (e.g., -30℃, -25℃, -20℃, -15℃, or -10℃, etc.).

[0027] Preferably, the tert-butylamine is added by constant pressure dripping.

[0028] In this invention, the addition of tert-butylamine using a constant-pressure dropwise method is beneficial for controlling the temperature of the reaction system. This not only avoids the risk of byproducts caused by local heat accumulation, but also ensures that the raw materials are in full contact with each other, thereby improving the yield.

[0029] Preferably, the temperature change of the system is controlled to be less than 5°C during the addition of the tert-butylamine.

[0030] Preferably, the temperature of the reaction in step (1) is 10℃~25℃ (e.g., 10℃, 15℃, 20℃ or 25℃, etc.), and the reaction time is 5~12 h (e.g., 5 h, 6 h, 7 h, 8 h, 10 h or 12 h, etc.), more preferably 5~7 h.

[0031] In the preparation method provided by the present invention, step (1) does not require extremely low temperature during the preparation process; 10℃~25℃ is sufficient to meet the requirements, thereby reducing energy consumption.

[0032] Preferably, the reaction in step (1) is carried out under a protective gas atmosphere.

[0033] Preferably, the protective gas includes any one or a combination of at least two of nitrogen, argon, or helium.

[0034] Preferably, after the reaction in step (1), the reaction further includes: adding a good solvent to the reaction system to dissolve the niobium-based complex, and then filtering to obtain a solution containing the niobium-based complex;

[0035] Preferably, the good solvent includes any one or a combination of at least two of tetrahydrofuran, diethyl ether, or 1,4-dioxane.

[0036] Preferably, the preparation method of methyl ethylamino lithium in step (2) includes: reacting n-butyllithium with methyl ethylamine to obtain methyl ethylamino lithium.

[0037] Preferably, the molar ratio of methyl ethylamine to n-butyllithium is (1-3):1 (for example, it can be 1:1, 1.1:1, 1.2:1, 1.5:1, 2:1 or 3:1, etc.), and more preferably (1-1.2):1.

[0038] In this invention, a specific molar ratio of methyl ethylamine to n-butyllithium is beneficial to improving the yield of the target product. The best technical effect is achieved when the molar ratio is (1 to 1.2):1. If the molar ratio is lower than 1:1, the excess n-butyllithium will react with the intermediate in step (1), reducing the product yield. If the molar ratio is higher than 1.2:1, it will not only waste raw materials, but also increase the viscosity of the reaction solution, leading to excessive side reactions and reducing the product yield and purity.

[0039] Preferably, the molar ratio of the n-butyllithium to the niobium pentachloride in step (1) is (3-3.2):1 (for example, it can be 3:1, 3.05:1, 3.1:1, 3.15:1 or 3.2:1, etc.).

[0040] Preferably, the reaction is carried out in the presence of a solvent.

[0041] Preferably, the solvent is a hydrocarbon solvent, preferably C5-C. 12 (For example, it could be C5, C8, C) 10 Or C 12 Alkanes, etc.

[0042] Preferably, the C5-C 12 The alkanes include any one or a combination of at least two of n-pentane, n-hexane or n-heptane, with n-hexane being more preferred.

[0043] Preferably, the reaction specifically includes: mixing n-butyllithium and a solvent and cooling, adding methyl ethylamine to react, and obtaining a solution containing methyl ethylamine lithium.

[0044] Preferably, the cooling is to a temperature of -30℃ to -10℃ (e.g., -30℃, -25℃, -20℃, -15℃, or -10℃, etc.).

[0045] Preferably, the methyl ethylamine is added by constant pressure dripping.

[0046] Preferably, the temperature change of the system is controlled to be less than 5°C during the addition of methyl ethylamine.

[0047] Preferably, the reaction temperature is 10℃ to 25℃ (e.g., 10℃, 15℃, 20℃ or 25℃, etc.), and the reaction time is 2 to 8 h (e.g., 2 h, 4 h, 6 h or 8 h, etc.), more preferably 2 to 3 h.

[0048] Preferably, the reaction is carried out under a protective gas atmosphere.

[0049] Preferably, the protective gas includes any one or a combination of at least two of nitrogen, argon, or helium.

[0050] Preferably, the reaction in step (2) specifically includes: cooling a solution containing methyl ethylamino lithium, adding a solution containing a niobium-based complex to react, and obtaining the tri(ethylmethylamino)tert-butanamide niobium.

[0051] Preferably, the cooling is to a temperature of -30℃ to -10℃ (e.g., -30℃, -25℃, -20℃, -15℃, or -10℃, etc.).

[0052] Preferably, the solution containing the niobium-based complex is added by constant pressure dropwise addition.

[0053] Preferably, the temperature change of the system is controlled to be below 5°C during the addition of the solution containing the niobium-based complex.

[0054] Preferably, the temperature of the reaction in step (2) is 10℃~25℃ (e.g., 10℃, 15℃, 20℃ or 25℃, etc.), and the reaction time is 5~12 h (e.g., 5 h, 6 h, 8 h, 10 h or 12 h, etc.), more preferably 5~8 h.

[0055] Preferably, the reaction in step (2) is carried out under a protective gas atmosphere.

[0056] Preferably, the protective gas includes any one or a combination of at least two of nitrogen, argon, or helium.

[0057] Preferably, after the reaction in step (2), the reaction system is further filtered, and the filtrate is distilled to obtain the tri(ethylmethylamino)tert-butanamide niobium.

[0058] In this invention, after the reaction is completed, the solvent is removed by atmospheric distillation, and then the fraction at 100~110℃ / 0.16~0.32 mmHg is collected by vacuum distillation to obtain the tri(ethylmethylamino)tert-butanamide niobium.

[0059] Preferably, the preparation method of the tris(ethylmethylamino)tert-butanamide niobium specifically includes the following steps:

[0060] (1) Under a protective gas atmosphere, the solvent, niobium pentachloride, ethylene glycol dimethyl ether and zinc chloride are mixed and cooled to -30℃ to -10℃. Tert-butylamine is added dropwise, and the system temperature is controlled below 0℃. The reaction is carried out at 10℃ to 30℃ for 5 to 12 h. The solution containing niobium-based complex is obtained by filtration.

[0061] The molar ratio of tert-butylamine, ethylene glycol dimethyl ether, zinc chloride and niobium pentachloride is (3-3.2):(1-1.2):(2-4):1;

[0062] (2) Under a protective gas atmosphere, n-butyllithium and solvent are mixed, cooled to -30℃ to -10℃, methyl ethylamine is added dropwise, the system temperature is controlled below 0℃, and the reaction is carried out at 10℃ to 25℃ for 2 to 8 h to obtain a solution containing methyl ethylamine lithium.

[0063] The molar ratio of methyl ethylamine to n-butyllithium is (1-3):1;

[0064] The molar ratio of the n-butyllithium to the niobium pentachloride in step (1) is (3-3.2):1;

[0065] (3) The solution containing niobium-based complex in step (1) is added dropwise to the solution containing methyl ethylamino lithium in step (2) which is cooled to -30℃ to -10℃. The temperature of the reaction system is controlled to be below 0℃. After the addition is complete, the reaction is carried out at 10℃ to 25℃ for 5 to 12 hours under a protective gas atmosphere. The reaction system is then filtered, and the filtrate is distilled to obtain the tri(ethylmethylamino)tert-butanamide niobium.

[0066] Compared with the prior art, the present invention has at least the following beneficial effects:

[0067] (1) The raw materials in the preparation method of niobium tri(ethylmethylamino)tert-butylamide provided by the present invention are simple and readily available, avoiding the use of toxic raw materials such as pyridine and toluene, making the process safer, more environmentally friendly and simpler to operate; and the reagents used are all inexpensive and common commercial reagents, which can reduce the production cost of the product while ensuring safety.

[0068] (2) Due to the strong Lewis acidity of zinc chloride, the process of forming a complex between ethylene glycol dimethyl ether and zinc chloride with niobium metal in this method is faster and the reaction efficiency is higher; and the coordination bond energy formed between dimethyl glycol dimethyl ether and the niobium metal center is small and the activity is higher, so dimethyl glycol dimethyl ether is easier to detach, making the reaction rate of the methyl ethylamino lithium complex with niobium in step (2) faster and the reaction time shorter.

[0069] (3) The method provided by the present invention eliminates the step of adding pyridine, does not require additional cooling operation, and only requires two steps to obtain the product. The total number of operation steps is less, the process is simpler, the total time is shorter, and the reaction conditions are mild and easy to control.

[0070] (4) The method provided by the present invention can meet the requirements by cooling the temperature to -30℃ to 10℃, thereby reducing energy consumption.

[0071] (5) The synthesis method of the present invention greatly improves the yield and purity of the product, which is conducive to large-scale industrial production. Attached Figure Description

[0072] Figure 1 It is the tris(ethylmethylamino)tert-butanamide niobium prepared in Example 1 of this application. 1 Nuclear magnetic resonance (NMR) test. Detailed Implementation

[0073] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0074] Example 1

[0075] This embodiment provides a method for preparing niobium tris(ethylmethylamino)tert-butamide, the method comprising the following steps:

[0076] (1) Reaction flask 1: Under N2 atmosphere, 20 g of niobium pentachloride (0.074 mol), 200 mL of n-hexane, 6.67 g of ethylene glycol dimethyl ether (0.074 mol) and 20.2 g of zinc dichloride (0.148 mol) were added to a 500 mL three-necked reaction flask and cooled to -10 °C. Then, 16.2 g of tert-butylamine (0.222 mol) was slowly added dropwise, and the temperature of the system was kept to remain within 5 °C. After the addition was completed, the reaction was carried out at 25 °C for 5 h. Then, 40 mL of tetrahydrofuran was added and the solid was removed by filtration to obtain a filtrate containing niobium-based complex.

[0077] (2) Reaction flask 2: Under N2 atmosphere, 2.5 M n-butyllithium n-hexane solution (94.8 mL, 0.237 mol) was added to a 500 mL reaction flask and cooled to -10℃. Methyl ethylamine (16.8 g, 0.284 mol) was slowly added dropwise to the reaction flask through a constant pressure dropping funnel. During this period, the temperature change of the system was kept not more than 5℃. After the addition was completed, the reaction was carried out at 25℃ for 2 h to obtain a solution containing methyl ethylamine lithium.

[0078] (3) The solution containing lithium methyl ethylamino was obtained in reaction flask 2 and cooled to -10°C. The filtrate from reaction flask 1 was slowly added dropwise to reaction flask 2 through a constant pressure dropping funnel, while keeping the temperature of the system within 5°C. After the addition was completed, the reaction was carried out at 25°C for 5 h. After the reaction was completed, the solution was filtered to remove the generated inorganic salts. The solvent was removed by atmospheric distillation at 70°C. The apparatus was then replaced with a vacuum distillation apparatus, and the fraction at 100°C / 0.16 mmHg was collected to obtain 21.9 g of yellow liquid tris(ethyl methylamino) tert-butamide niobium (yield: 87.4%).

[0079] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0080] 1 H NMR (400 MHz, C6D6): δ 3.46 (q, J = 7.0 Hz, 6H), 3.19 (s, 9H), 1.41(s, 9H), 1.15 (t, J = 7.0 Hz, 9H).

[0081] Example 2

[0082] This embodiment provides a method for preparing tri(ethylmethylamino)tert-butylamide niobium. The only difference between this method and Example 1 is that the temperature in steps (1), (2), and (3) is changed from -10°C to -30°C. The other raw materials, contents, and methods are the same as in Example 1. 22.1 g of yellow liquid tri(ethylmethylamino)tert-butylamide niobium (yield: 88.2%) is obtained.

[0083] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0084] 1 H NMR (400 MHz, C6D6): δ 3.45 (q, J = 7.0 Hz, 6H), 3.17 (s, 9H), 1.40 (s, 9H), 1.14 (t, J = 7.0 Hz, 9H).

[0085] Example 3

[0086] This embodiment provides a method for preparing niobium tri(ethylmethylamino)tert-butylamide. The only difference between this method and Example 1 is that in step (1), tert-butylamine (16.2 g, 0.222 mol) is adjusted to tert-butylamine (17.3 g, 0.237 mol). The other raw materials, contents and methods are the same as in Example 1, and 22.3 g of yellow liquid niobium tri(ethylmethylamino)tert-butylamide is obtained (yield: 89.0%).

[0087] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0088] 1 H NMR (400 MHz, C6D6): δ 3.47 (q, J = 7.0 Hz, 6H), 3.19 (s, 9H), 1.42(s, 9H), 1.16 (t, J = 7.0 Hz, 9H).

[0089] Example 4

[0090] This embodiment provides a method for preparing niobium tri(ethylmethylamino)tert-butamide. The only difference between this method and Example 1 is that in step (1), ethylene glycol dimethyl ether (6.67 g, 0.074 mol) is changed to ethylene glycol dimethyl ether (8.00 g, 0.089 mol). The other raw materials, contents and methods are the same as in Example 1, and 21.5 g of yellow liquid niobium tri(ethylmethylamino)tert-butamide is obtained (yield: 85.8%).

[0091] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0092] 1 H NMR (400 MHz, C6D6): δ 3.46 (q, J = 7.0 Hz, 6H), 3.20 (s, 9H), 1.42(s, 9H), 1.16 (t, J = 7.0 Hz, 9H).

[0093] Example 5

[0094] This embodiment provides a method for preparing niobium tri(ethylmethylamino)tert-butamide. The only difference between this method and Example 1 is that in step (1), zinc dichloride (20.2 g, 0.148 mol) is adjusted to zinc dichloride (22.2 g, 0.163 mol). The other raw materials, contents and methods are the same as in Example 1, and 21.4 g of yellow liquid niobium tri(ethylmethylamino)tert-butamide is obtained (yield: 85.4%).

[0095] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0096] 1 H NMR (400 MHz, C6D6): δ 3.47 (q, J = 7.0 Hz, 6H), 3.19 (s, 9H), 1.43(s, 9H), 1.16 (t, J = 7.0 Hz, 9H).

[0097] Example 6

[0098] This embodiment provides a method for preparing niobium tri(ethylmethylamino)tert-butamide. The only difference between this method and Example 1 is that in step (2), methyl ethylamine (16.8 g, 0.284 mol) is adjusted to methyl ethylamine (14.0 g, 0.237 mol). The other raw materials, contents and methods are the same as in Example 1, and 21.3 g of yellow liquid niobium tri(ethylmethylamino)tert-butamide is obtained (yield: 85.0%).

[0099] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0100] 1 H NMR (400 MHz, C6D6): δ 3.47 (q, J = 7.0 Hz, 6H), 3.20 (s, 9H), 1.41 (s, 9H), 1.16 (t, J = 7.0 Hz, 9H).

[0101] Example 7

[0102] This embodiment provides a method for preparing tri(ethylmethylamino)tert-butanamide niobium. The difference between this method and Example 1 is that in step (2), the 2.5 M n-butyllithium n-hexane solution (94.8 mL, 0.237 mol) is adjusted to the 2.5 M n-butyllithium n-hexane solution (88.8 mL, 0.222 mol), and the methyl ethylamine (16.8 g, 0.284 mol) is adjusted to the methyl ethylamine (15.8 g, 0.267 mol). The other raw materials, contents, and methods are the same as in Example 1, and 21.0 g of yellow liquid tri(ethylmethylamino)tert-butanamide niobium is obtained (yield: 83.8%).

[0103] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0104] 1 H NMR (400 MHz, C6D6): δ 3.45 (q, J = 7.0 Hz, 6H), 3.20 (s, 9H), 1.40 (s, 9H), 1.15 (t, J = 7.0 Hz, 9H).

[0105] Example 8

[0106] This embodiment provides a method for preparing tri(ethylmethylamino)tert-butylamide niobium. The only difference between the preparation method and that in Example 1 is that in step (1), the reaction time of the additive was changed from 5 h at 25°C to 7 h at 10°C. The other raw materials, contents and methods are the same as in Example 1, and 21.7 g of yellow liquid tri(ethylmethylamino)tert-butylamide niobium (yield: 86.6%) is obtained.

[0107] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0108] 1 H NMR (400 MHz, C6D6): δ 3.45 (q, J = 7.0 Hz, 6H), 3.18 (s, 9H), 1.42(s, 9H), 1.15 (t, J = 7.0 Hz, 9H).

[0109] Example 9

[0110] This embodiment provides a method for preparing niobium tri(ethylmethylamino)tert-butamide. The only difference between this method and Example 1 is that in step (2), the reaction time at 25°C for 2 hours after the addition of the reagent is changed to the reaction time at 10°C for 3 hours after the addition of the reagent. The other raw materials, contents and methods are the same as in Example 1. 22.1 g of yellow liquid niobium tri(ethylmethylamino)tert-butamide (yield: 88.2%) is obtained.

[0111] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0112] 1 H NMR (400 MHz, C6D6): δ 3.48 (q, J = 7.0 Hz, 6H), 3.20 (s, 9H), 1.42(s, 9H), 1.16 (t, J = 7.0 Hz, 9H).

[0113] Example 10

[0114] This embodiment provides a method for preparing niobium tri(ethylmethylamino)tert-butamide. The only difference between this method and Example 1 is that in step (3), the addition of the raw materials and the reaction at 25°C for 5 hours were changed to the addition of the raw materials and the reaction at 10°C for 8 hours. The other raw materials, contents and methods are the same as in Example 1. 21.4 g of yellow liquid niobium tri(ethylmethylamino)tert-butamide (yield: 85.4%) was obtained.

[0115] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0116] 1 H NMR (400 MHz, C6D6): δ3.45 (q, J = 7.0 Hz, 6H), 3.18 (s, 9H), 1.41(s, 9H), 1.14 (t, J = 7.0 Hz, 9H).

[0117] Example 11

[0118] This embodiment provides a method for preparing tri(ethylmethylamino)tert-butylamide niobium. The only difference between this method and Example 1 is that in step (1), tert-butylamine (16.2 g, 0.222 mol) is adjusted to tert-butylamine (15.2 g, 0.207 mol). The other raw materials, contents and methods are the same as in Example 1, and 20.7 g of yellow liquid tri(ethylmethylamino)tert-butylamide niobium is obtained (yield: 82.6%).

[0119] Comparative Example 1

[0120] This comparative example provides a method for preparing niobium tris(ethylmethylamino)tert-butamide, the method comprising the following steps:

[0121] (1) Under N2 atmosphere, add 20 g of niobium pentachloride (0.074 mol) and 200 mL of n-hexane to reaction flask No. 1, stir well, lower the temperature of reaction flask No. 1 to -30℃ and maintain it, then add anhydrous tert-butylamine (10.82 g, 0.148 mol), and after the addition is complete, restore the temperature to 25℃ and react for 4 hours.

[0122] (2) The temperature of reaction flask No. 1 was lowered to -30℃, and pyridine (12.9 g, 0.163 mol) was added while stirring. After the addition was completed, the temperature was restored to 25℃ and the reaction was carried out for 4 hours. The reaction mixture was filtered and concentrated to obtain a niobium complex suspension.

[0123] (3) Under N2 atmosphere, 2.5 M n-butyllithium in n-hexane solution (92.4 mL, 0.231 mol) was added to reaction flask No. 2, and the temperature was lowered to -20℃. Methyl ethylamine (14.2 g, 0.241 mol) was slowly added dropwise to the reaction flask through a constant pressure dropping funnel, while keeping the system temperature below 0℃. After the addition was completed, the temperature was restored to 25℃ and the reaction was carried out for 3 hours. Then the temperature of reaction vessel No. 2 was lowered to -20℃, and the niobium complex suspension obtained in step (2) was added to it. After the addition was completed, the temperature was restored to 25℃ and the reaction was carried out overnight.

[0124] (4) After passing the liquid obtained in step (3) through a solid-liquid separator, the separated solution is transferred to a distillation apparatus. First, the pressure is reduced to 20 kPa and the temperature is 50 °C to distill off n-hexane. Then, the pressure is reduced to 0.16 mmHg and the temperature is 100 °C to distill off yellow (tri(ethylmethylamino)tert-butamide niobium 17.1 g (yield: 68.3%)).

[0125] Comparative Example 2

[0126] This comparative example provides a method for preparing niobium tri(ethylmethylamino)tert-butamide. The only difference between this method and Example 1 is that in step (1), ethylene glycol dimethyl ether (6.67 g, 0.074 mol) is changed to tetrahydrofuran (5.34 g, 0.074 mol). The other raw materials, contents and methods are the same as in Example 1, and 3.28 g of yellow liquid niobium tri(ethylmethylamino)tert-butamide is obtained (yield: 13.1%).

[0127] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0128] 1 H NMR (400 MHz, C6D6): δ 3.46 (q, J = 7.0 Hz, 6H), 3.20 (s, 9H), 1.42(s, 9H), 1.16 (t, J = 7.0 Hz, 9H).

[0129] Comparative Example 3

[0130] This comparative example provides a method for preparing niobium tri(ethylmethylamino)tert-butamide. The only difference between this method and Example 1 is that in step (1), zinc dichloride (20.2 g, 0.148 mol) is replaced with aluminum trichloride (19.7 g, 0.148 mol). The other raw materials, contents and methods are the same as in Example 1, and 2.2 g of yellow liquid niobium tri(ethylmethylamino)tert-butamide is obtained (yield: 8.0%).

[0131] The NMR characterization data of the compound tris(ethylmethylamino)tert-butamide niobium are as follows:

[0132] 1 H NMR (400 MHz, C6D6): δ 3.47 (q, J = 7.0 Hz, 6H), 3.19 (s, 9H), 1.43(s, 9H), 1.16 (t, J = 7.0 Hz, 9H).

[0133] The yields and NMR purities of the products tris(ethylmethylamino)tert-butanamide niobium obtained in Examples 1-11 and Comparative Examples 1-3 are shown in Table 1.

[0134] Table 1

[0135]

[0136] The test results show that:

[0137] (1) As can be seen from Examples 1-11, the method for preparing niobium tri(ethylmethylamino)tert-butamide provided by the present invention uses a combination of ethylene glycol dimethyl ether and zinc chloride, which completely replaces the toxic and irritating pyridine. Furthermore, the method uses n-hexane instead of toluene, which significantly eliminates the health hazards, environmental problems and operational inconveniences caused by pyridine and toluene, making the process greener, safer and easier to scale up. In addition, all raw materials are common commercially available raw materials with low prices, which can greatly reduce the production cost of the product.

[0138] (2) As can be seen from the comparison between Example 1 and Example 11, the present invention can further improve the yield and purity of the product by optimizing the molar ratio of tert-butylamine to niobium pentachloride.

[0139] (3) As can be seen from the comparison of Examples 1-7 and Comparative Example 1, compared with the previous methods, the preparation method of niobium tri(ethylmethylamino)tert-butylamide provided by the present invention not only shortens the reaction steps, requiring only two steps to obtain the product, but also improves the activity of the niobium-based intermediate by using a combination of ethylene glycol dimethyl ether and zinc chloride. Ethylene glycol dimethyl ether has a weaker bond energy in the complex formed with (tert-butylimide)trichloroniobium, resulting in higher reactivity, and the reaction time between methylethylaminolithium and the complex is shorter. The preparation method provided by the present invention has higher yield and purity compared with the prior art.

[0140] The comparison of Examples 1, 2, and 3 shows that the use of specific zinc chloride in this invention results in higher yields and purity of the reaction. Furthermore, compared to tetrahydrofuran, when ethylene glycol dimethyl ether is used as a stabilizer for the niobium-based complex, the yield and purity of the final product are higher.

[0141] In summary, this invention optimizes the existing method for preparing niobium tri(ethylmethylamino)tert-butamide. The raw materials are simple and readily available and non-toxic. The reaction process is simple to operate, the reaction conditions are mild, and the reaction process is safe with no dangerous byproducts generated. At the same time, the target product obtained has high yield and purity, which is conducive to large-scale industrial production.

[0142] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing niobium tris(ethylmethylamino)tert-butamide, characterized in that, The preparation method includes the following steps: (1) Niobium pentachloride, ethylene glycol dimethyl ether, zinc chloride and tert-butylamine react to give a niobium-based complex; (2) The niobium-based complex reacts with methyl ethylamino lithium to obtain the tri(ethylmethylamino)tert-butamide niobium; The synthetic route of the preparation method is as follows: 。 2. The preparation method according to claim 1, characterized in that, The molar ratio of ethylene glycol dimethyl ether to niobium pentachloride in step (1) is (1-1.2):1; Preferably, the molar ratio of zinc chloride to niobium pentachloride in step (1) is (2-4):1, and more preferably (2-2.2):1; Preferably, the molar ratio of tert-butylamine to niobium pentachloride in step (1) is (2.8-3.2):1, and more preferably (3-3.2):

1.

3. The preparation method according to claim 1 or 2, characterized in that, The reaction described in step (1) is carried out in the presence of a solvent; Preferably, the solvent is a hydrocarbon solvent, preferably C5-C. 12 Alkanes; Preferably, the C5-C 12 Alkanes include any one or a combination of at least two of n-pentane, n-hexane or n-heptane, with n-hexane being more preferred; Preferably, the reaction specifically includes: mixing niobium pentachloride, ethylene glycol dimethyl ether, zinc chloride and solvent and cooling, adding tert-butylamine to react, and obtaining a niobium-based complex; Preferably, the cooling is to a temperature of -30℃ to -10℃; Preferably, the temperature change of the system is controlled to be less than 5°C during the addition of the tert-butylamine.

4. The preparation method according to any one of claims 1-3, characterized in that, The reaction temperature in step (1) is 10℃~25℃, and the reaction time is 5~12 h, more preferably 5~7 h; Preferably, the reaction in step (1) is carried out under a protective gas atmosphere; Preferably, after the reaction in step (1), the reaction further includes: adding a good solvent to the reaction system to dissolve the niobium-based complex, and then filtering to obtain a solution containing the niobium-based complex; Preferably, the good solvent includes any one or a combination of at least two of tetrahydrofuran, diethyl ether, or 1,4-dioxane.

5. The preparation method according to any one of claims 1-4, characterized in that, The preparation method of methyl ethylamino lithium in step (2) includes: reacting n-butyllithium with methyl ethylamine to obtain methyl ethylamino lithium; Preferably, the molar ratio of methyl ethylamine to n-butyllithium is (1-3):1, more preferably (1-1.2):1; Preferably, the molar ratio of the n-butyllithium to the niobium pentachloride in step (1) is (3-3.2):

1.

6. The preparation method according to claim 5, characterized in that, The reaction is carried out in the presence of a solvent; Preferably, the solvent is a hydrocarbon solvent, preferably C5-C. 12 Alkanes; Preferably, the C5-C 12 Alkanes include any one or a combination of at least two of n-pentane, n-hexane or n-heptane, with n-hexane being more preferred; Preferably, the reaction specifically includes: mixing n-butyllithium and a solvent and cooling, adding methyl ethylamine to react, and obtaining a solution containing methyl ethylamine lithium; Preferably, the cooling is to a temperature of -30℃ to -10℃; Preferably, the temperature change of the system is controlled to be less than 5°C during the addition of methyl ethylamine.

7. The preparation method according to claim 5 or 6, characterized in that, The reaction temperature is 10℃~25℃, and the reaction time is 2~8 h, more preferably 2~3 h; Preferably, the reaction is carried out under a protective gas atmosphere.

8. The preparation method according to any one of claims 1-7, characterized in that, The reaction in step (2) specifically includes: cooling a solution containing methyl ethylamino lithium, adding a solution containing a niobium complex to react, and obtaining the tri(ethylmethylamino)tert-butamide niobium; Preferably, the cooling is to a temperature of -30℃ to -10℃; Preferably, the temperature change of the system is controlled to be below 5°C during the addition of the solution containing the niobium-based complex.

9. The preparation method according to any one of claims 1-8, characterized in that, The reaction temperature in step (2) is 10℃~25℃, and the reaction time is 5~12 h, more preferably 5~8 h; Preferably, the reaction in step (2) is carried out under a protective gas atmosphere.

10. The preparation method according to any one of claims 1-9, characterized in that, Step (2) further includes filtering the reaction system and distilling the filtrate to obtain the tri(ethylmethylamino)tert-butanamide niobium.

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