A process for the preparation of tris(methylcyclopentadienyl) yttrium

Abstract

This invention provides a method for preparing tris(methylcyclopentadienyl)yttrium. This method can efficiently remove key impurities, simplifying the process while effectively improving the purity and yield of tris(methylcyclopentadienyl)yttrium. The preparation method includes the following steps: S1, under an inert atmosphere, methylcyclopentadiene and a bis(trimethylsilyl)amino potassium salt solution are mixed at a temperature ≤30°C, and then the temperature is raised to 75-85°C for reaction; after the reaction, the mixture is filtered under reduced pressure to obtain a cyclopentadienyl potassium salt intermediate; S2, under an inert atmosphere, yttrium trichloride and the cyclopentadienyl potassium salt intermediate are mixed in the presence of a solvent, and then the temperature is raised for reaction; after the reaction, the mixture is filtered, the filtrate is collected, and the filtrate is concentrated under reduced pressure to obtain a crude product; S3, the crude product is pretreated by reduced pressure distillation to obtain a pretreated product; then, it is sublimated under vacuum to obtain the tris(methylcyclopentadienyl)yttrium.

Description

Technical Field

[0001] This invention relates to the fields of organometallic chemistry and high-end electronic material preparation technology, specifically to a method for preparing tris(methylcyclopentadienyl)yttrium, a yttrium-based precursor, for atomic layer deposition (ALD) or chemical vapor deposition (CVD) processes. Background Technology

[0002] With the development of semiconductors and advanced display devices, the demand for high-k materials is increasing. Yttrium oxide, due to its excellent dielectric properties, good thermal stability, and compatibility with silicon-based processes, shows potential in high-k gate dielectric layers, buffer layers, and catalytic materials. Alternating current generation (ALD / CVD) technology is crucial for preparing high-quality yttrium oxide thin films, and the purity, volatility, and thermal stability of its precursors directly determine the quality of the film.

[0003] Tris(methylcyclopentadienyl)yttrium combines the steric stability of cyclopentadienyl ligands with suitable reactivity, exhibiting good volatility and thermal stability, making it a highly promising yttrium-based precursor. As a key yttrium precursor, high purity and high vapor pressure are crucial requirements for ensuring film growth rate and film quality. In existing technologies, the synthesis of this compound often relies on the direct reaction of methylcyclopentadiene with yttrium halides or Grignard reagent-mediated reactions, with purification typically achieved through simple vacuum distillation or recrystallization.

[0004] The existing methods for preparing tris(methylcyclopentadienyl)yttrium have significant defects and shortcomings, mainly including: 1. Insufficient product purity: The intermediate has not undergone deep purification, and the residual metal and chlorine impurities will affect the subsequent thin film deposition effect and fail to meet the stringent requirements of high-end semiconductor processes for precursors; 2. Yield needs improvement: Due to incomplete purification and numerous side reactions, the yield of existing methods is low, failing to fully realize the economic value of the reactants; 3. Potential safety risks in the process: The reaction is highly exothermic, and the lack of precise temperature control and feeding design may lead to safety risks during scale-up production; 4. Product is easily decomposed: Conventional purification methods can easily lead to partial decomposition of the product, reducing yield and purity. Summary of the Invention

[0005] To address at least one deficiency in existing technologies, this invention provides a method for preparing tris(methylcyclopentadienyl)yttrium. This method can efficiently remove key impurities, significantly improve the purity and yield of tris(methylcyclopentadienyl)yttrium while simplifying the process, and enhance the safety of the process.

[0006] To achieve its objective, the present invention provides the following technical solution: This invention provides a method for preparing tris(methylcyclopentadienyl)yttrium, comprising the following steps: S1. Methylcyclopentadiene and bis(trimethylsilyl)amino potassium salt solution are mixed at a temperature of ≤30°C under an inert atmosphere, and then the resulting mixture is heated to 75-85°C and reacted at a constant temperature under normal pressure. After the reaction was completed, the mixture was filtered under reduced pressure to obtain a solid cyclopentadienyl potassium salt intermediate. S2. Under an inert atmosphere, yttrium trichloride and the cyclopentadienyl potassium salt intermediate are mixed in the presence of a solvent, and then the mixture is heated to 95-105°C and subjected to a constant-temperature reaction at atmospheric pressure. After the reaction was completed, the mixture was filtered, the filtrate was collected, and the filtrate was concentrated under reduced pressure to obtain crude tris(methylcyclopentadienyl)yttrium. S3. The crude tris(methylcyclopentadienyl)yttrium product is pretreated by vacuum distillation to obtain a pretreated product; then the pretreated product is sublimated under vacuum to obtain the tris(methylcyclopentadienyl)yttrium; wherein the sublimation temperature of the vacuum sublimation is 180-200℃, the vacuum degree is 1000-5000Pa, and the condensation zone temperature is -10℃ to 0℃.

[0007] Preferably, in step S1, the bis(trimethylsilyl)aminopotassium salt solution is a toluene solution of bis(trimethylsilyl)aminopotassium.

[0008] Preferably, step S2 is performed according to either method one or method two: Method 1: Add a toluene solution of yttrium trichloride to the cyclopentadienyl potassium salt intermediate and stir to form a uniform suspension, then heat to carry out the isothermal reaction; Method 2: Yttrium trichloride is dispersed and activated with tetrahydrofuran at room temperature, and then the resulting solution is added to the toluene solution of the cyclopentadienyl potassium salt intermediate. The solution is stirred to form a uniform suspension, and then the temperature is raised to carry out the isothermal reaction. More preferably, step S2 is performed according to method two.

[0009] Preferably, in the second method, the mass-to-volume ratio of yttrium trichloride and tetrahydrofuran is 1:8 to 1:12, in g / mL; Preferably, the dispersion activation time is 20-26 hours.

[0010] Preferably, in step S1, the filter residue obtained by vacuum filtration is washed with toluene.

[0011] Preferably, in step S1, the molar ratio of methylcyclopentadiene to potassium bis(trimethylsilyl)amino (KN(TMS)2) is 1:(1±0.1). In step S2, the molar ratio of cyclopentadienyl potassium salt to yttrium trichloride (YCl3) is 3:(1±0.2).

[0012] Preferably, in step S3, the pressure of vacuum distillation is 0.05~0.1 MPa.

[0013] Preferably, in step S3, the sublimation temperature of the vacuum sublimation is 185-195℃, and the vacuum degree is 2500-3000Pa.

[0014] The technical solution provided by this invention has the following beneficial effects: The method for preparing tris(methylcyclopentadienyl)yttrium provided by this invention can improve the yield and purity of the target product, while having high safety and good potential for process scale-up. Detailed Implementation

[0015] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0016] 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 term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.

[0017] This invention provides a method for preparing tris(methylcyclopentadienyl)yttrium, comprising the following steps: S1. Methylcyclopentadiene and bis(trimethylsilyl)amino potassium salt solution are mixed under an inert atmosphere at a temperature ≤30°C (e.g., 0, 10, 20, 30°C, etc.), and then the resulting mixture is heated to 75-85°C (e.g., 75, 80, 85°C, etc.) and isothermal reaction is carried out at atmospheric pressure; in some examples, the reaction time is, for example, 4-8 hours. After the reaction was completed, the mixture was filtered under reduced pressure to obtain a solid cyclopentadienyl potassium salt intermediate. S2. Under an inert atmosphere, yttrium trichloride is mixed with the cyclopentadienyl potassium salt intermediate in the presence of a solvent, and then the mixture is heated to 95-105°C (e.g., 95, 100, 105°C, etc.) and isothermal reaction is carried out at atmospheric pressure; in some examples, the reaction time is, for example, 8-14 hours. After the reaction was completed, the mixture was filtered, the filtrate was collected, and the filtrate was concentrated under reduced pressure to obtain crude tris(methylcyclopentadienyl)yttrium. S3. The crude tris(methylcyclopentadienyl)yttrium product is pretreated by vacuum distillation to obtain a pretreated product; then the pretreated product is sublimated under vacuum to obtain the tris(methylcyclopentadienyl)yttrium; wherein the sublimation temperature of the vacuum sublimation is 180-200℃ (e.g., 180, 190, 200℃, etc.), the vacuum degree is 1000-5000Pa (e.g., 1000, 2000, 3000, 4000, 5000Pa, etc.), and the condensation zone temperature is -10℃ to 0℃ (e.g., -10, -5, 0℃, etc.).

[0018] The method of this invention employs a finely controlled reaction process and combines a purification strategy of "reduced pressure distillation pretreatment" and "vacuum sublimation purification" in step S3 to achieve efficient removal of key impurities. This method can significantly improve the purity and yield of tris(methylcyclopentadienyl)yttrium while simplifying the process and enhancing the safety of the process.

[0019] This invention first removes low-boiling-point impurities through vacuum distillation pretreatment, and then uses vacuum sublimation to deeply purify the product, efficiently separating metallic impurities and non-volatile organic byproducts, fundamentally solving the problem of impurity residue. In key reaction steps, the mixing temperature and the reaction temperature are strictly controlled to avoid violent exothermic reactions and side reactions, effectively reducing the risk of material spillage and ensuring the safety and stability of process scale-up. In the vacuum sublimation purification stage, the sublimation temperature is controlled at 180-200℃, the vacuum degree at 1000-5000Pa, and the condensation zone temperature at -10℃ to 0℃. Under these conditions, sublimation avoids product decomposition during purification while ensuring high yield and high purity.

[0020] In this invention, in step S1, the mixing stage temperature is controlled at ≤30℃, which effectively suppresses the intensity of the deprotonation reaction and avoids local overheating leading to side reactions of methylcyclopentadiene polymerization. The isothermal reaction temperature is controlled at 75~85℃. Within this range, the deprotonation reaction conversion rate is ≥98%. Below 75℃, the reaction period needs to be significantly extended, for example, to more than 8 hours. Above 85℃, it is easy to trigger the decomposition of KN(TMS)2 and the dimerization reaction of methylcyclopentadiene. The reaction in step S2 is carried out under normal pressure (inert gas protection), without the need for additional pressurization or depressurization, simplifying the process operation and avoiding the loss of methylcyclopentadiene due to negative pressure volatilization.

[0021] In this invention, the isothermal reaction temperature in step S2 is controlled at 95~105℃. Within this range, the coordination reaction rate and selectivity are optimal. In some examples, complete coordination can be achieved in 12 hours. If the temperature is below 95℃, the reaction time needs to be significantly extended, for example, to 16 hours. If the temperature is above 105℃, partial thermal decomposition of the target product is likely to occur. The reaction in step S2 is carried out under normal pressure (dry inert gas protection) to prevent the system from absorbing moisture, which would lead to hydrolysis of YCl3 and deterioration of potassium salts, thus ensuring the stability of the reaction.

[0022] Preferably, in step S1, the bis(trimethylsilyl)aminopotassium salt solution is a toluene solution of bis(trimethylsilyl)aminopotassium. There is no particular limitation on the amount of toluene used, as long as it meets the requirements for dissolution, dispersion and reaction. In some examples, the concentration of the toluene solution is 0.8-1.2 mol / L.

[0023] Furthermore, step S2 is performed according to either method one or method two: Method 1: Add the toluene solution of yttrium trichloride to the cyclopentadienyl potassium salt intermediate and stir to form a uniform suspension, then heat to carry out the isothermal reaction; there is no particular limitation on the amount of toluene in the toluene solution of yttrium trichloride, as long as it can meet the solvent requirements for dissolution, dispersion and reaction. In some examples, the concentration of the toluene solution is 0.2-0.5 mol / L.

[0024] Method 2: Yttrium trichloride is dispersed and activated with tetrahydrofuran at room temperature. The resulting solution is then added to a toluene solution of the cyclopentadienyl potassium salt intermediate, and stirred to form a uniform suspension. The solution is then heated to carry out the isothermal reaction. There is no particular limitation on the amount of toluene in the toluene solution of the cyclopentadienyl potassium salt intermediate, as long as it meets the requirements for material dispersion and reaction. In some examples, the concentration of the toluene solution is 1.2-1.6 mol / L. Preferably, step S2 is performed according to method two, which can further significantly improve the yield of the target product.

[0025] Preferably, in the second method, the mass-to-volume ratio of yttrium trichloride to tetrahydrofuran is 1:8 to 1:12 (e.g., 1:8, 1:10, 1:12, etc.), in g / mL; Preferably, the dispersion activation time is 20-26 hours.

[0026] Preferably, in step S1, the filter residue obtained by vacuum filtration is washed with toluene.

[0027] Preferably, in step S1, the molar ratio of methylcyclopentadiene to potassium bis(trimethylsilyl)amino (KN(TMS)2) is 1:(1±0.1), i.e., 1:(0.9-1.1). This preferred molar ratio ensures complete deprotonation of methylcyclopentadiene into cyclopentadienyl potassium salt and avoids residual methylcyclopentadiene, preventing impurity accumulation due to excessive amounts. In step S2, the molar ratio of cyclopentadienyl potassium salt to yttrium trichloride (YCl3) is 3:(1±0.2), i.e., 3:(0.8-1.2). This preferred molar ratio ensures sufficient coordination of yttrium ions, allows for molar ratio fluctuations within a certain range, adapts to subtle differences in material conversion rates in industrial production, and avoids separation burden caused by excessive ligand amounts. If the molar ratios in steps S1 and S2 deviate from the above range, it will have adverse effects. For example, insufficient or low amounts of methylcyclopentadiene or KN(TMS)2 will lead to incomplete formation of cyclopentadienyl potassium salt, resulting in incomplete coordination of YCl3. If the amount of a certain material exceeds the above range (such as excessive amounts of methylcyclopentadiene), it will increase the difficulty of purification by vacuum distillation and sublimation, and may introduce additional impurities or cause waste of raw materials.

[0028] In step S3 of this invention, the pressure of the vacuum distillation pretreatment is preferably controlled at 0.05~0.1 MPa, which can efficiently remove low-boiling-point impurities such as toluene and unreacted small molecules. If the pressure is too high (>0.1 MPa), the impurities will not be completely removed, and if it is too low (<0.05 MPa), a small amount of the target product will be lost due to volatilization. During the sublimation stage, the vacuum degree is controlled at 1000~5000 Pa. If the vacuum degree is too low (<1000 Pa), it will reduce the sublimation rate and prolong the production cycle; if it is too high (>5000 Pa), the product may be extracted with the tail gas, reducing the yield. The sublimation temperature is controlled at 180~200℃. In this range, the product has a stable sublimation rate and structure. Below 180℃, the sublimation efficiency is extremely low, and above 200℃, the product is prone to thermal decomposition and carbonization. The temperature of the condensation zone is controlled between -10℃ and 0℃ to ensure that the sublimated product can be quickly condensed and crystallized. If the temperature is too high (>0℃), the condensation will be insufficient and the product recovery rate will decrease; if the temperature is too low (<-10℃), the refrigeration energy consumption will increase and there will be no significant benefit.

[0029] More preferably, in step S3, the sublimation temperature of the vacuum sublimation is 185-195°C, and the vacuum degree is 2500-3000 Pa. The inventors have found that performing vacuum sublimation under these preferred conditions can further improve the sublimation effect and increase the yield of the target product.

[0030] The present invention will be further illustrated by the following embodiments, but it should not be construed as the present invention being limited to these embodiments.

[0031] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0032] Example 1: Gram-scale preparation in the laboratory S1: Preparation of cyclopentadienyl potassium salt intermediate Under the protection of inert argon gas, methylcyclopentadiene (0.6 mol, 48.3 g) was added dropwise to a toluene solution (500 mL, containing 20.6 mol, 119.7 g of KN(TMS)2) of the deprotonating reagent bis(trimethylsilyl)amino potassium (KN(TMS)2), allowing the two to mix slowly at low temperature. The reaction temperature during the mixing stage was strictly controlled to ≤30℃ to avoid an overly vigorous deprotonation reaction. After the addition was complete, the temperature was raised to 80℃ and the reaction was maintained at atmospheric pressure for 6 h to generate the cyclopentadienyl potassium salt intermediate. After the reaction was completed, the reaction solvent and the byproduct bis(trimethylsilyl)amine (HN(TMS)2) were removed by vacuum filtration in a glove box. The filter residue was washed three times with toluene, and the resulting white solid was the cyclopentadienyl potassium salt intermediate. The conversion rate of this step was >98%, and 0.59 mol of the cyclopentadienyl potassium salt intermediate was obtained.

[0033] S2: Preparation of crude tris(methylcyclopentadienyl)yttrium Under the protection of inert argon gas, a toluene solution (500 mL) of yttrium trichloride (YCl3, 0.2 mol, 39.1 g) was slowly introduced into the above-mentioned cyclopentadienyl potassium salt intermediate, and stirred to form a homogeneous suspension. The mixture was then heated to 100 °C and reacted at atmospheric pressure for 12 h to allow the coordination reaction to proceed fully. After the reaction was complete, the generated potassium chloride solid byproduct was removed by filtration, and the filtrate was collected and concentrated under reduced pressure to obtain crude tris(methylcyclopentadienyl)yttrium.

[0034] S3: Purify the target product The crude product was first pretreated by vacuum distillation (pressure controlled at 0.05~0.1 MPa) to completely remove low-boiling-point impurities (such as a small amount of toluene and unreacted methylcyclopentadiene) from the system. Then, the pretreated product was placed in a sublimation apparatus and vacuum sublimated at a vacuum of 2000 Pa (i.e. 0.002 MPa) and a sublimation temperature of 200℃. The temperature of the condensation zone was controlled at -2℃ and the sublimation time was maintained for 8 h. The condensed white crystalline product was then collected.

[0035] Yield and Characterization: High-purity tris(methylcyclopentadienyl)yttrium was finally obtained, with a yield of 72%. (NMR spectroscopy, 1H NMR spectrum) 1Characterization results (H NMR, solvent CDCl3, internal standard TMS) showed: δ 1.78~1.82 ppm (s, 9H, methyl hydrogen in -C5H4(CH3)), δ 5.56~5.60 ppm (m, 6H, hydrogen on the cyclopentadienyl ring). The target characteristic peaks were sharp and clear, with no obvious impurity peaks. ICP detection showed that the product purity exceeded 99.9%, which meets the requirements of high-end ALD precursor processes.

[0036] Example 2: Scale-up Experiment Following the reaction conditions, material ratios, and operating procedures of Example 1, a large-scale experiment was conducted by scaling up the dosage of all materials (including solvent volume) by 10 times, while maintaining essentially the same process parameters. The difference lies in: The sublimation conditions for step S3 are: vacuum degree 3000 Pa (0.003 MPa), sublimation temperature 190℃, condensation zone temperature -5℃, and sublimation time 9 h.

[0037] Results: High-purity target product was obtained, with the yield increased to 75%. The proton NMR spectrum was completely consistent with that of Example 1, indicating excellent purity and no obvious impurities. ICP testing showed that the product purity exceeded 99.9%, meeting the requirements of high-end ALD precursor processes, demonstrating that the process has good adaptability for large-scale production.

[0038] Example 3 S1: Prepare the cyclopentadienyl potassium salt intermediate according to step S1 of Example 1. The difference is that after obtaining the cyclopentadienyl potassium salt intermediate, the intermediate is transferred to a 2 L flask and 400 mL of toluene is added for dispersion.

[0039] S2: Preparation of crude tris(methylcyclopentadienyl)yttrium Under the protection of inert argon gas, yttrium trichloride (YCl3, 0.2 mol, 39.1 g) was weighed and dispersed in 400 mL of tetrahydrofuran at room temperature for 24 h with stirring. Then, it was slowly added to the toluene dispersion of the above-mentioned cyclopentadienyl potassium salt intermediate, and stirred to form a homogeneous suspension. The reaction system was heated to 100 °C and reacted at atmospheric pressure for 12 h to allow the coordination reaction to proceed fully. After the reaction was completed, the generated potassium chloride solid byproduct was removed by filtration, and the filtrate was collected and concentrated under reduced pressure to obtain crude tris(methylcyclopentadienyl)yttrium.

[0040] S3: Refer to step S3 of Example 1, and will not be repeated here.

[0041] Yield and Characterization: The yield was increased to 81%. The 1H NMR spectrum was consistent with that of Example 1, indicating excellent purity, with a product purity exceeding 99.9%. The 1H NMR spectrum and ICP characterization results showed that the product purity met the requirements of high-end ALD precursor processes.

[0042] Comparative Example 1: Sublimation purification step omitted The preparation process of Example 1 was repeated, with only the purification step adjusted: step S3 was performed only by vacuum distillation pretreatment, without sublimation, and the remaining reaction conditions and material amounts were the same as in Example 1.

[0043] Results: The product purity was insufficient, with impurity content far exceeding the process limits for high-end ALD precursors, and the target product yield was only 48%. 1H NMR spectroscopy showed multiple impurity peaks around the target peak (mainly concentrated in the δ1.5~2.0 ppm and δ5.3~5.8 ppm ranges), indicating that without sublimation purification, coordination impurities and residual salts in the system could not be effectively removed.

[0044] Comparative Example 2: Sublimation temperature too high The preparation process of Example 1 was repeated, except that the sublimation temperature in step S3 was adjusted to 220°C, while the other process parameters (vacuum degree, condensation temperature, sublimation time, etc.) remained unchanged.

[0045] Results: A dark, viscous product was obtained, with the yield decreasing to 45%. Analysis of the characterization results showed that tris(methylcyclopentadienyl)yttrium underwent significant thermal decomposition at higher temperatures, leading to abnormal product color and a sharp decrease in yield, proving that sublimation temperatures exceeding 200℃ would destroy the structure of the target product.

[0046] Comparative Example 3 The procedure was carried out in accordance with Example 1, except that in step S1, during the isothermal reaction stage, the reaction temperature was 90°C.

[0047] Results: After step S1, a dark, viscous mixture was obtained. The yield of the intermediate product cyclopentadienyl potassium salt was significantly reduced, and it was difficult to separate the usable cyclopentadienyl potassium salt, making it impossible to proceed to the next step.

[0048] Comparative Example 4 The procedure was carried out in accordance with Example 1, except that in step S2, during the isothermal reaction stage, the reaction temperature was 110°C.

[0049] Results: The crude product became significantly darker in color, and the yield of the final product, tris(methylcyclopentadienyl)yttrium, decreased significantly to 54%, with the impurity content failing to meet the requirements of high-end ALD precursor processes.

[0050] Application performance data (ALD deposition of yttrium oxide thin film) Using the products of Example 1 and Comparative Example 1 as ALD precursors, yttrium oxide (Y2O3) thin film deposition experiments were conducted at a deposition temperature of 250°C and with deionized water as the oxygen source. The test results are as follows: Thin film growth rate: The precursor of Example 1 had a growth rate of 0.75 Å / cycle, which was stable; the precursor of Comparative Example 1 had a growth rate of 0.58 Å / cycle, which was lower and fluctuated more.

[0051] Thin film impurity content (XPS characterization): The chlorine content of the thin film prepared in Example 1 was <0.3 at%, with no obvious impurity element residue; the chlorine content of the thin film in Comparative Example 1 was about 2.1 at%, mainly due to unremoved potassium chloride impurities and coordination residues.

[0052] Film uniformity: The film uniformity (1σ) of the film obtained in Example 1 is <2%, and the overall morphology is uniform; the film uniformity of Comparative Example 1 is about 5%, and impurities lead to increased surface roughness and uneven component distribution.

[0053] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing tris(methylcyclopentadienyl)yttrium, characterized in that, Includes the following steps: S1. Methylcyclopentadiene and bis(trimethylsilyl)amino potassium salt solution are mixed at a temperature of ≤30°C under an inert atmosphere, and then the resulting mixture is heated to 75-85°C and reacted at a constant temperature under normal pressure. After the reaction was completed, the mixture was filtered under reduced pressure to obtain a solid cyclopentadienyl potassium salt intermediate. S2. Under an inert atmosphere, yttrium trichloride and the cyclopentadienyl potassium salt intermediate are mixed in the presence of a solvent, and then the mixture is heated to 95-105°C and subjected to a constant-temperature reaction at atmospheric pressure. After the reaction was completed, the mixture was filtered, the filtrate was collected, and the filtrate was concentrated under reduced pressure to obtain crude tris(methylcyclopentadienyl)yttrium. S3. The crude tris(methylcyclopentadienyl)yttrium product is pretreated by vacuum distillation to obtain the pretreated product. The pretreated product was then subjected to vacuum sublimation to obtain tris(methylcyclopentadienyl)yttrium; wherein the sublimation temperature of the vacuum sublimation was 180-200℃, the vacuum degree was 1000-5000Pa, and the condensation zone temperature was -10℃ to 0℃.

2. The preparation method according to claim 1, characterized in that, In step S1, the bis(trimethylsilyl)aminopotassium salt solution is a toluene solution of bis(trimethylsilyl)aminopotassium.

3. The preparation method according to claim 1, characterized in that, Step S2 is performed according to either method one or method two as follows: Method 1: Add a toluene solution of yttrium trichloride to the cyclopentadienyl potassium salt intermediate and stir to form a uniform suspension, then heat to carry out the isothermal reaction; Method 2: Yttrium trichloride is dispersed and activated with tetrahydrofuran at room temperature, and then the resulting solution is added to the toluene solution of the cyclopentadienyl potassium salt intermediate. The solution is stirred to form a uniform suspension, and then the temperature is raised to carry out the isothermal reaction. Preferably, step S2 is performed according to method two.

4. The preparation method according to claim 3, characterized in that, In the second method, the mass-to-volume ratio of yttrium trichloride and tetrahydrofuran is 1:8 to 1:12, in g / mL. Preferably, the dispersion activation time is 20-26 hours.

5. The preparation method according to any one of claims 1-4, characterized in that, In step S1, the filter residue obtained by vacuum filtration is washed with toluene.

6. The preparation method according to any one of claims 1-4, characterized in that, In step S1, the molar ratio of methylcyclopentadiene and bis(trimethylsilyl)aminopotassium is 1:(1±0.1). In step S2, the molar ratio of cyclopentadienyl potassium salt to yttrium trichloride is 3:(1±0.2).

7. The preparation method according to any one of claims 1-4, characterized in that, In step S3, the pressure of vacuum distillation is 0.05~0.1 MPa.

8. The preparation method according to any one of claims 1-4, characterized in that, In step S3, the sublimation temperature of the vacuum sublimation is 185-195℃, and the vacuum degree is 2500-3000Pa.