Tri (dimethylamino) cyclopentadienyl hafnium and preparation process thereof

Abstract

The invention discloses tris (dimethylamino) cyclopentadienyl hafnium and a preparation process thereof.The preparation process of the tris (dimethylamino) cyclopentadienyl hafnium comprises the following steps that S1, an n-hexane solution of n-butyllithium and dimethylamine are subjected to a reaction, and a lithium dimethylamino emulsion is obtained; s2, adding hafnium tetrachloride into the lithium dimethylamino emulsion for reaction, and separating to obtain a liquid-phase product; s3, the liquid-phase product is heated, a tetra (dimethylamino) hafnium concentrated solution is obtained, and the volume of the tetra (dimethylamino) hafnium concentrated solution is 20%-30% of the volume of the liquid-phase product; and S4, obtaining cyclopentadiene, adding the cyclopentadiene into the tetra (dimethylamino) hafnium concentrated solution to react, and filtering to obtain tris (dimethylamino) cyclopentadienyl hafnium. According to the preparation process of the tris (dimethylamino) cyclopentadienyl hafnium, complex solvent components are not needed, the preparation efficiency is improved, and the use amount of the solvent and the preparation cost are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of compound production, in particular to tris(dimethylamino)cyclopentadienyl hafnium and its preparation process. Background Art

[0002] There are many methods for synthesizing tri(dimethylamino)cyclopentadiene hafnium at present, one of which is to synthesize high-precision tetra(dimethylamino) hafnium in an ionic liquid buffer solvent, then use cyclopentane to prepare cyclopentadiene through a four-step reaction, and finally mix the two to prepare tri(dimethylamino)cyclopentadiene hafnium and distill and purify. This scheme needs to be carried out in an ionic buffer solution with complex components, that is, the solvent composition is too complex, the cost is high, and the complex solvent may also pollute the environment, and the intermediate product (tetra(dimethylamino) hafnium) needs to be purified, the time cost is high and the amount of solvent used is large.

[0003] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0004] The object of the present invention is to provide a preparation process of tris(dimethylamino)cyclopentadienyl hafnium, which does not require complex solvent components, improves preparation efficiency, and reduces the amount of solvent used and the preparation cost.

[0005] To achieve the above object, an embodiment of the present invention provides a preparation process of tris(dimethylamino)cyclopentadienyl hafnium, comprising the following steps:

[0006] S1, reacting a n-hexane solution of n-butyl lithium with dimethylamine to obtain a lithium dimethylamine emulsion;

[0007] S2, adding hafnium tetrachloride to the lithium dimethylamide emulsion to react, and separating to obtain a liquid phase product;

[0008] S3, heating the liquid phase product to obtain tetrakis(dimethylamino)hafnium concentrated solution, wherein the volume of the tetrakis(dimethylamino)hafnium concentrated solution is 20% to 30% of the volume of the liquid phase product;

[0009] S4, obtaining cyclopentadiene and adding it to the tetrakis(dimethylamino)hafnium concentrated solution for reaction, filtering, and obtaining tris(dimethylamino)cyclopentadienylhafnium.

[0010] In one or more embodiments of the present invention, the reaction in step S1 is carried out at a temperature of -20 to -10°C and under inert gas protection; the reaction in step S2 is carried out at a temperature of -20 to -10°C and under inert gas protection.

[0011] In one or more embodiments of the present invention, the inert gas is nitrogen or argon.

[0012] In one or more embodiments of the present invention, the step of obtaining the lithium dimethylamine emulsion comprises:

[0013] The mixture obtained after the reaction of n-butyl lithium and dimethylamine is heated to remove the dimethylamine that has not participated in the reaction and the by-product butane.

[0014] In one or more embodiments of the present invention, the molar ratio of n-butyl lithium to dimethylamine is 1:1.2 to 1.5;

[0015] The molar ratio of n-butyl lithium to hafnium tetrachloride is 1:0.95-1;

[0016] The molar ratio of hafnium tetrachloride to cyclopentadiene is 1:1.15-1.2.

[0017] In one or more embodiments of the present invention, in step S2, the step of separating and obtaining a liquid phase product comprises:

[0018] The mixture after the reaction is completed is heated to reflux, and then separated to obtain the liquid phase product.

[0019] In one or more embodiments of the present invention, in step S4, the step of obtaining cyclopentadiene comprises:

[0020] Cyclopentadiene is obtained by heating dicyclopentadiene.

[0021] In one or more embodiments of the present invention, in step S4, the step of obtaining tris(dimethylamino)cyclopentadienyl hafnium comprises:

[0022] The filtered product is subjected to distillation treatment to remove the solvent, thereby obtaining tris(dimethylamino)cyclopentadienylhafnium.

[0023] In one or more embodiments of the present invention, step S4 further includes:

[0024] The crude product obtained after the distillation treatment is subjected to reduced pressure distillation to obtain purified tris(dimethylamino)cyclopentadienylhafnium.

[0025] An embodiment of the present invention further provides tris(dimethylamino)cyclopentadienyl hafnium, which is prepared by the above-mentioned preparation process of tris(dimethylamino)cyclopentadienyl hafnium.

[0026] Compared with the prior art, the preparation process of tris(dimethylamino)cyclopentadienyl hafnium according to the embodiment of the present invention has the following advantages:

[0027] 1. The present invention does not require complex solvent components and only uses n-hexane as a single solvent as the reaction medium, which simplifies the reaction implementation, greatly saves costs, and reduces pollution to the environment;

[0028] 2. The present invention does not require the purification of the intermediate tetrakis(dimethylamino)hafnium, which greatly saves time cost and solvent usage without affecting the yield and quality of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart of a process for preparing tris(dimethylamino)cyclopentadienyl hafnium according to one embodiment of the present invention;

[0030] Figure 2 is the chemical structural formula of tris(dimethylamino)cyclopentadienylhafnium according to one embodiment of the present invention;

[0031] Figure 3 1 is a hydrogen NMR spectrum of tris(dimethylamino)cyclopentadienylhafnium according to one embodiment of the present invention. DETAILED DESCRIPTION

[0032] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0033] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0034] like Figure 1 As shown, the preparation process of tris(dimethylamino)cyclopentadienyl hafnium according to a preferred embodiment of the present invention comprises the following steps:

[0035] S1. reacting a n-hexane solution of n-butyl lithium with dimethylamine to obtain a lithium dimethylamine emulsion.

[0036] The reaction in step S1 is carried out at a temperature of -20 to -10°C and under the protection of an inert gas.

[0037] Specifically, the step of obtaining the lithium dimethylamide emulsion includes: heating the mixture obtained after the reaction of n-butyl lithium and dimethylamine to remove the dimethylamine that does not participate in the reaction and the by-product butane. The mixture in this step is a mixture containing lithium dimethylamide obtained as a solid phase after the reaction of n-butyl lithium and dimethylamine.

[0038] Specifically, the molar ratio of n-butyl lithium to dimethylamine is 1:1.2 to 1.5. Theoretically, n-butyl lithium and dimethylamine react in a 1:1 (molar ratio), but in order to ensure that all n-butyl lithium reacts to generate dimethylamine lithium, dimethylamine is in excess.

[0039] Specifically, the reaction time in step S1 can be 4 hours.

[0040] S2. Add hafnium tetrachloride to lithium dimethylamide emulsion for reaction, and separate to obtain a liquid phase product.

[0041] The reaction in step S2 is carried out at a temperature of -20 to -10°C and under the protection of an inert gas.

[0042] Specifically, hafnium tetrachloride can be added to the lithium dimethylamine emulsion in batches for reaction, thereby avoiding excessive heat release caused by continuous feeding. For example, hafnium tetrachloride can be added in equal amounts in 5-10 times.

[0043] Specifically, the step of separating and obtaining the liquid phase product includes: heating and refluxing the mixture after the reaction is completed, and then separating and obtaining the liquid phase product. Heating and refluxing can cause the precipitated particles to aggregate, and after stopping the stirring, the solid phase precipitate is naturally settled, which is convenient for separating and obtaining the liquid phase product. It can also reduce the influence of the insoluble salts generated by the reaction on the later product purification process, thereby improving the yield.

[0044] Specifically, the reaction time in step S2 can be: stirring the reaction at -20 to -10°C for 12 hours, and then slowly heating to room temperature.

[0045] Specifically, the molar ratio of n-butyl lithium to hafnium tetrachloride is 1:0.95-1. This ratio principle requires a 1:1 feed, but due to the cost of raw materials (the cost of hafnium tetrachloride is relatively high), the hafnium tetrachloride needs to be completely reacted, that is, the molar amount of hafnium tetrachloride should be approximately greater than or equal to the molar amount of n-butyl lithium. Since the molar ratio of n-butyl lithium to dimethylamine in step S1 is 1:1.2-1.5, that is, dimethylamine is excessive, it is considered that n-butyl lithium is completely reacted to form dimethylamine lithium, so it can be considered that the molar amount of dimethylamine lithium is equal to the molar amount of n-butyl lithium. S3, heat the liquid product to obtain tetrakis(dimethylamino)hafnium concentrated solution, wherein the volume of the tetrakis(dimethylamino)hafnium concentrated solution is 20%-30% of the volume of the liquid product.

[0046] This step is to reduce the total volume of the reaction solution. When the process is mass-produced in the later stage, multiple reaction concentrates can be combined and then cyclopentadiene can be added uniformly to improve the production efficiency during mass production. In addition, this step does not require the solvent in the tetrakis(dimethylamino)hafnium concentrate to be completely evaporated, thereby saving energy consumption and improving production efficiency. The reaction intensity of the tetrakis(dimethylamino)hafnium concentrate (i.e., high-concentration tetrakis(dimethylamino)zirconium solution) and cyclopentadiene is relatively low. When concentrated to 20%, the subsequent reaction is still within the controllable range and does not affect the conversion rate of the reaction itself.

[0047] S4, obtaining cyclopentadiene and adding it to the tetrakis(dimethylamino)hafnium concentrated solution to react, filtering, and obtaining tris(dimethylamino)cyclopentadienylhafnium.

[0048] Specifically, the molar ratio of hafnium tetrachloride to cyclopentadiene is 1:1.15-1.2. This ratio means that tetrakis(dimethylamino)hafnium is completely reacted and a large amount of disubstituted products are not generated. Incompletely reacted tetrakis(dimethylamino)hafnium will affect the subsequent purification of the product. This reduces side reactions and by-products and increases the yield of the target product. Among them, the molar amount of tetrakis(dimethylamino)hafnium can be considered to be equal to the molar amount of hafnium tetrachloride.

[0049] Specifically, the step of obtaining cyclopentadiene includes: heating dicyclopentadiene to react and obtain cyclopentadiene. For example, dicyclopentadiene is heated to 170° C. and then cracked and distilled to obtain cyclopentadiene.

[0050] The reaction in step S4 is carried out under the protection of an inert gas.

[0051] Specifically, in step S4, cyclopentadiene can be added to the tetrakis(dimethylamino)hafnium concentrated solution by dropwise addition, and the temperature is maintained at -20 to -10°C during the dropwise addition. After the dropwise addition is completed, the temperature is slowly raised to room temperature and the reaction is continued by stirring for 12 hours.

[0052] Specifically, the filtering step may be: filtering under the protection of an inert gas and washing with n-hexane for several times.

[0053] Specifically, the step of obtaining tris(dimethylamino)cyclopentadienyl hafnium includes: distilling the filtered product to remove the solvent to obtain tris(dimethylamino)cyclopentadienyl hafnium. Removing the solvent refers to removing the n-hexane solvent. The distillation temperature can be about 65°C, for example, 62-68°C.

[0054] Further, step S4 also includes: performing vacuum distillation on the crude product obtained after the distillation treatment to obtain purified tris(dimethylamino)cyclopentadienyl hafnium. For example, the crude product is subjected to vacuum distillation, the vacuum degree of the vacuum distillation is about 0.1 mmHg, and the heating temperature of the vacuum distillation is 85-90°C. Collecting the fraction with a top temperature of 60-65°C is the purified tris(dimethylamino)cyclopentadienyl hafnium. The top temperature refers to the temperature at the top discharge port of the distillation device during the vacuum distillation process.

[0055] The inert gas in the preparation process of tris(dimethylamino)cyclopentadienyl hafnium of the present invention is nitrogen or argon.

[0056] like Figure 2 As shown, an embodiment of the present invention further provides a tris(dimethylamino)cyclopentadienyl hafnium, and the tris(dimethylamino)cyclopentadienyl hafnium is prepared by the above-mentioned preparation process of tris(dimethylamino)cyclopentadienyl hafnium.

[0057] The preparation process of tris(dimethylamino)cyclopentadienyl hafnium of the present invention will be described in detail below in conjunction with specific examples.

[0058] In order to have a clearer understanding of the characteristic methods and effects of the present invention, a detailed description of a specific implementation scheme is now provided in accordance with the accompanying drawings.

[0059] Example 1

[0060] Under nitrogen protection, add 250mL of n-butyllithium n-hexane solution (2.5M) and 300mL of n-hexane to a 1L reaction bottle, keep stirring, keep the temperature of the reaction system between -20℃ and -10℃, and then introduce 40g of dimethylamine gas. After the gas is introduced, maintain the reaction temperature and stir for 4 hours. After the reaction is completed, the system is heated to 40℃, nitrogen is introduced and the exhaust is connected and stirred for 1 hour, then the exhaust is disconnected and returned to room temperature;

[0061] Under nitrogen protection, 47.5 g of hafnium tetrachloride was added to the system in small amounts and in multiple batches, the temperature of the reaction system was kept between -20°C and -10°C, stirred for 12 hours, and then slowly heated to room temperature. After the reaction was completed, the system was heated to 50°C, stirred and refluxed for 1 hour, then returned to room temperature, allowed to settle, and the liquid phase product was separated. After that, the liquid phase product was heated to evaporate, so as to concentrate the total volume of about 600 mL of the liquid phase product to about 150 mL, and tetrakis(dimethylamino)hafnium concentrated solution was obtained;

[0062] Under nitrogen protection, 12 g of freshly prepared cyclopentadiene monomer was slowly added dropwise to the above concentrated solution, and the temperature of the reaction system was kept between -20°C and -10°C during the addition process, and then the temperature was slowly raised to room temperature and stirred for 12 hours;

[0063] After the reaction is completed, the mixture is filtered and washed several times with n-hexane under nitrogen protection, and all the solution is collected. The solvent is evaporated at 65°C to obtain a crude product. The crude product is then subjected to reduced pressure distillation at a vacuum degree of 0.1 mmHg and a heating temperature of 90°C. The fraction with a top temperature of 60-65°C is collected, which is tri(dimethylamino)cyclopentadienyl hafnium, and the yield is 65%. Figure 3 As shown, 1 HNMR (400MHz, C6D6): 6.04 (s, 5H), 2.96 (s, 18H).

[0064] Example 2

[0065] Under nitrogen protection, add 3L of n-butyl lithium in n-hexane solution (2.5M) and 1L of n-hexane to a 5L reaction bottle, keep stirring, keep the temperature of the reaction system between -20°C and -10°C, and then introduce 450g of dimethylamine. After the gas is introduced, maintain the reaction temperature and stir for 4 hours. After the reaction is completed, the system is heated to 40°C, nitrogen is introduced and the vent is connected and stirred for 1 hour, then the vent is disconnected and returned to room temperature;

[0066] Under nitrogen protection, 590 g of hafnium tetrachloride was added to the system in small amounts and in multiple batches, the temperature of the reaction system was kept between -20°C and -10°C and stirred for 12 hours, and then slowly heated to room temperature. After the reaction was completed, the system was heated to 50°C, stirred and refluxed for 1 hour, and then returned to room temperature, and allowed to settle to separate the liquid phase product. After that, the liquid phase product was heated to evaporate, so as to concentrate the total volume of about 4 L of the liquid phase product to about 1 L, and obtain tetrakis(dimethylamino)hafnium concentrated solution;

[0067] Under nitrogen protection, 140 g of freshly prepared cyclopentadiene monomer was slowly added dropwise into the system, and the temperature of the reaction system was kept between -20°C and -10°C during the addition process, and then the temperature was slowly raised to room temperature and stirred for 12 hours;

[0068] After the reaction, the mixture was filtered and washed several times with n-hexane under nitrogen protection, and all the solution was collected. The solvent was evaporated at 65°C to obtain a crude product. The crude product was then subjected to reduced pressure distillation at a vacuum degree of 0.1 mmHg and a heating temperature of 90°C, and the fraction with a top temperature of 60-65°C was collected, which was tri(dimethylamino)cyclopentadienyl hafnium, with a yield of 63%. 1 H NMR (400MHz, C6D6): 6.03 (s, 5H), 2.95 (s, 18H).

[0069] Example 3

[0070] Under nitrogen protection, add 30L of n-butyl lithium in n-hexane solution (2.5M) and 10L of n-hexane to a 50L reactor, keep stirring, keep the temperature of the reaction system between -20°C and -10°C, and then introduce 5.1kg of dimethylamine. After the gas is introduced, maintain the reaction temperature and stir for 4 hours. After the reaction is completed, the system is heated to 40°C, nitrogen is introduced and the exhaust is connected and stirred for 1 hour, then the exhaust is disconnected and returned to room temperature;

[0071] Under nitrogen protection, 6 kg of hafnium tetrachloride was added to the system in small amounts and in multiple batches, the temperature of the reaction system was kept between -20°C and -10°C and stirred for 12 hours, and then slowly heated to room temperature. After the reaction was completed, the system was heated to 50°C, stirred and refluxed for 1 hour, and then returned to room temperature, and allowed to settle to separate the liquid phase product. After that, the liquid phase product was heated to evaporate, so as to concentrate the total volume of about 40 L of the liquid phase product to about 10 L, and obtain tetrakis(dimethylamino)hafnium concentrated solution;

[0072] Under nitrogen protection, 1.4 g of freshly prepared cyclopentadiene monomer was slowly added dropwise into the system. During the addition, the temperature of the reaction system was kept between -20°C and -10°C, and then the temperature was slowly raised to room temperature and stirred for 12 hours.

[0073] After the reaction, the mixture was filtered and washed several times with n-hexane under nitrogen protection, and all the solution was collected. The solvent was evaporated at 65°C to obtain a crude product. The crude product was then subjected to reduced pressure distillation at a vacuum degree of 0.1 mmHg and a heating temperature of 90°C, and the fraction with a top temperature of 60-65°C was collected, which was tri(dimethylamino)cyclopentadienyl hafnium, with a yield of 59%. 1 H NMR (400MHz, C6D6): 6.04 (s, 5H), 2.95 (s, 18H).

[0074] Example 4

[0075] Under nitrogen protection, add 250mL of n-butyllithium n-hexane solution (2.5M) and 300mL of n-hexane to a 1L reaction bottle, keep stirring, keep the temperature of the reaction system between -20℃ and -10℃, and then introduce 38g of dimethylamine gas. After the gas is introduced, maintain the reaction temperature and stir for 4 hours. After the reaction is completed, the system is heated to 40℃, nitrogen is introduced and the exhaust is connected and stirred for 1 hour, then the exhaust is disconnected and returned to room temperature;

[0076] Under nitrogen protection, 48 g of hafnium tetrachloride was added to the system in small amounts and in multiple batches, the temperature of the reaction system was kept between -20°C and -10°C, stirred for 12 hours, and then slowly heated to room temperature. After the reaction was completed, the system was heated to 50°C, stirred and refluxed for 1 hour, then returned to room temperature, allowed to settle, and the liquid phase product was separated. After that, the liquid phase product was heated to evaporate, so as to concentrate the total volume of about 600 mL of the liquid phase product to about 120 mL, and tetrakis(dimethylamino)hafnium concentrated solution was obtained;

[0077] Under nitrogen protection, 11.5 g of freshly prepared cyclopentadiene monomer was slowly added dropwise to the above concentrated solution, and the temperature of the reaction system was kept between -20°C and -10°C during the addition process, and then the temperature was slowly raised to room temperature and stirred for 12 hours;

[0078] After the reaction, the mixture was filtered and washed several times with n-hexane under nitrogen protection, and all the solution was collected. The solvent was evaporated at 65°C to obtain a crude product. The crude product was then subjected to reduced pressure distillation at a vacuum degree of 0.1 mmHg and a heating temperature of 90°C, and the fraction with a top temperature of 60-65°C was collected, which was tri(dimethylamino)cyclopentadienyl hafnium, with a yield of 62%.

[0079] Example 5

[0080] Under nitrogen protection, add 250mL of n-butyl lithium in n-hexane solution (2.5M) and 300mL of n-hexane to a 1L reaction bottle, keep stirring, keep the temperature of the reaction system between -20℃ and -10℃, and then introduce 42g of dimethylamine gas. After the gas is introduced, maintain the reaction temperature and stir for 4 hours. After the reaction is completed, the system is heated to 40℃, nitrogen is introduced and the exhaust is connected and stirred for 1 hour, then the exhaust is disconnected and returned to room temperature;

[0081] Under nitrogen protection, 50 g of hafnium tetrachloride was added to the system in small batches and for multiple times, the temperature of the reaction system was kept between -20°C and -10°C and stirred for 12 hours, and then slowly heated to room temperature. After the reaction was completed, the system was heated to 50°C, stirred and refluxed for 1 hour, and then returned to room temperature, and allowed to settle to separate the liquid phase product. After that, the liquid phase product was heated to evaporate, so as to concentrate the total volume of about 600 mL of the liquid phase product to about 180 mL, and obtain tetrakis(dimethylamino)hafnium concentrated solution;

[0082] Under nitrogen protection, 12 g of freshly prepared cyclopentadiene monomer was slowly added dropwise to the above concentrated solution, and the temperature of the reaction system was kept between -20°C and -10°C during the addition process, and then the temperature was slowly raised to room temperature and stirred for 12 hours;

[0083] After the reaction, the mixture was filtered and washed several times with n-hexane under nitrogen protection, and all the solution was collected. The solvent was evaporated at 65°C to obtain a crude product. The crude product was then subjected to reduced pressure distillation at a vacuum degree of 0.1 mmHg and a heating temperature of 85°C. The fraction with a top temperature of 60-65°C was collected, which was tri(dimethylamino)cyclopentadienyl hafnium. The yield was 61%.

[0084] Comparative Example 1

[0085] Under nitrogen protection, add 250mL of n-butyllithium n-hexane solution (2.5M) and 300mL of n-hexane to a 1L reaction bottle, keep stirring, keep the temperature of the reaction system between -20℃ and -10℃, and then introduce 40g of dimethylamine gas. After the gas is introduced, maintain the reaction temperature and stir for 4 hours. After the reaction is completed, the system is heated to 40℃, nitrogen is introduced and the exhaust is connected and stirred for 1 hour, then the exhaust is disconnected and returned to room temperature;

[0086] Under nitrogen protection, 47.5 g of hafnium tetrachloride was added to the system in small batches and several times, and the temperature of the reaction system was kept between -20°C and -10°C, and stirred for 12 hours, and then slowly heated to room temperature. After the reaction was completed, the system was heated to 50°C, stirred and refluxed for 1 hour, and then returned to room temperature, and allowed to settle to separate the liquid phase product;

[0087] Under nitrogen protection, 12 g of freshly prepared cyclopentadiene monomer was slowly added dropwise to the above concentrated solution, and the temperature of the reaction system was kept between -20°C and -10°C during the addition process, and then the temperature was slowly raised to room temperature and stirred for 12 hours;

[0088] After the reaction, the mixture was filtered and washed several times with n-hexane under nitrogen protection, and all the solution was collected. The solvent was evaporated at 65°C to obtain a crude product. The crude product was then subjected to reduced pressure distillation at a vacuum degree of 0.1 mmHg and a heating temperature of 65°C, and the fraction with a top temperature of 60-65°C was collected, which was tri(dimethylamino)cyclopentadienyl hafnium, with a yield of 40%.

[0089] Comparative Example 2

[0090] Under nitrogen protection, add 250mL of n-butyllithium n-hexane solution (2.5M) and 300mL of n-hexane to a 1L reaction bottle, keep stirring, keep the temperature of the reaction system between -20℃ and -10℃, and then introduce 40g of dimethylamine gas. After the gas is introduced, maintain the reaction temperature and stir for 4 hours. After the reaction is completed, the system is heated to 40℃, nitrogen is introduced and the exhaust is connected and stirred for 1 hour, then the exhaust is disconnected and returned to room temperature;

[0091] Under nitrogen protection, 47.5 g of hafnium tetrachloride was added to the system in small amounts and in multiple batches, the temperature of the reaction system was kept between -20°C and -10°C, stirred for 12 hours, and then slowly heated to room temperature. After the reaction was completed, the system was heated to 50°C, stirred and refluxed for 1 hour, then returned to room temperature, allowed to settle, and the liquid phase product was separated. After that, the liquid phase product was heated to evaporate, so as to concentrate the total volume of about 600 mL of the liquid phase product to about 100 mL, and obtain tetrakis(dimethylamino)hafnium concentrated solution;

[0092] Under nitrogen protection, 12 g of freshly prepared cyclopentadiene monomer was slowly added dropwise to the above concentrated solution, and the temperature of the reaction system was kept between -20°C and -10°C during the addition process, and then the temperature was slowly raised to room temperature and stirred for 12 hours;

[0093] After the reaction, the mixture was filtered and washed several times with n-hexane under nitrogen protection, and all the solution was collected. The solvent was evaporated at 65°C to obtain a crude product. The crude product was then subjected to reduced pressure distillation at a vacuum degree of 0.1 mmHg and a heating temperature of 90°C, and the fraction with a top temperature of 60-65°C was collected, which was tri(dimethylamino)cyclopentadienyl hafnium, with a yield of 45%.

[0094] It can be seen from the yield data in Comparative Example 1 and Example 1 that step S3 in the method for preparing tris(dimethylamino)cyclopentadienyl hafnium of the present invention can effectively improve the yield of tris(dimethylamino)cyclopentadienyl hafnium.

[0095] Compared with Example 1, in the step of dropping cyclopentadiene, the reaction color changes faster and the system temperature rises faster in Comparative Example 2. This situation has certain risks after the reaction scale is enlarged. In addition, it can be seen from the yield data in Comparative Example 1 and Example 1 that step S3 in the preparation method of tris(dimethylamino)cyclopentadiene hafnium of the present invention can effectively improve the yield of tris(dimethylamino)cyclopentadiene hafnium.

[0096] In summary, the preparation method of tris(dimethylamino)cyclopentadiene hafnium of the present invention has the following advantages:

[0097] 1. The present invention does not require complex solvent components and only uses n-hexane as a single solvent as the reaction medium, which simplifies the reaction implementation, greatly saves costs, and reduces pollution to the environment;

[0098] 2. The present invention does not require the purification of the intermediate tetrakis(dimethylamino)hafnium, which greatly saves time cost and solvent usage without affecting the yield and quality of the product;

[0099] 3. After all reactions are completed, the insoluble salts generated by the reactions are separated by sedimentation, which reduces the influence of solid phase substances on the second step reaction and the product distillation process during the later product purification process and improves the product yield.

[0100] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A process for preparing tris(dimethylamino)cyclopentadienyl hafnium, characterized in that: The following steps are involved: S1, reacting a n-hexane solution of n-butyl lithium with dimethylamine to obtain a lithium dimethylamine emulsion; S2, adding hafnium tetrachloride to the lithium dimethylamide emulsion to react, and separating to obtain a liquid phase product; S3, heating the liquid phase product to obtain tetrakis(dimethylamino)hafnium concentrated solution, wherein the volume of the tetrakis(dimethylamino)hafnium concentrated solution is 20% to 30% of the volume of the liquid phase product; S4, obtaining cyclopentadiene and adding it to the tetrakis(dimethylamino)hafnium concentrated solution for reaction, filtering, and obtaining tris(dimethylamino)cyclopentadienylhafnium.

2. The process for preparing tris(dimethylamino)cyclopentadienyl hafnium according to claim 1, characterized in that: The reaction in step S1 is carried out at a temperature of -20 to -10°C and under the protection of an inert gas; the reaction in step S2 is carried out at a temperature of -20 to -10°C and under the protection of an inert gas.

3. The process for preparing tris(dimethylamino)cyclopentadienyl hafnium as claimed in claim 2, characterized in that: The inert gas is nitrogen or argon.

4. The process for preparing tris(dimethylamino)cyclopentadienyl hafnium according to claim 1, characterized in that: The step of obtaining the lithium dimethylamine emulsion comprises: The mixture obtained after the reaction of n-butyl lithium and dimethylamine is heated to remove the dimethylamine that has not participated in the reaction and the by-product butane.

5. The process for preparing tris(dimethylamino)cyclopentadienyl hafnium according to claim 1, characterized in that: The molar ratio of n-butyl lithium to dimethylamine is 1:1.2-1.5; The molar ratio of n-butyl lithium to hafnium tetrachloride is 1:0.95-1; The molar ratio of hafnium tetrachloride to cyclopentadiene is 1:1.15-1.

2.

6. The process for preparing tris(dimethylamino)cyclopentadienyl hafnium according to claim 1, characterized in that: In step S2, the step of separating and obtaining a liquid phase product comprises: The mixture after the reaction is completed is heated to reflux, and then separated to obtain the liquid phase product.

7. The process for preparing tris(dimethylamino)cyclopentadienyl hafnium according to claim 1, characterized in that: In step S4, the step of obtaining cyclopentadiene comprises: Cyclopentadiene is obtained by heating dicyclopentadiene.

8. The process for preparing tris(dimethylamino)cyclopentadienyl hafnium according to claim 1, characterized in that: In step S4, the step of obtaining tris(dimethylamino)cyclopentadienyl hafnium comprises: The filtered product is subjected to distillation treatment to remove the solvent, thereby obtaining tris(dimethylamino)cyclopentadienylhafnium.

9. The process for preparing tris(dimethylamino)cyclopentadienyl hafnium as claimed in claim 8, characterized in that: The step S4 further comprises: The crude product obtained after the distillation treatment is subjected to reduced pressure distillation to obtain purified tris(dimethylamino)cyclopentadienylhafnium.

10. A tris(dimethylamino)cyclopentadienyl hafnium, characterized in that The tris(dimethylamino)cyclopentadienyl hafnium is prepared by the preparation process of tris(dimethylamino)cyclopentadienyl hafnium according to any one of claims 1 to 9.

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