A method for preparing metal complexes

Abstract

This invention discloses a method for preparing a metal complex, the general structural formula of which is CpM(NR1R2)3, wherein R1 and R2 are Me or Et, and M is Zr or Hf. The preparation method includes the following steps: S1: Magnesium thiocene is added to a tetrahydrofuran solvent and stirred to form a magnesium thiocene tetrahydrofuran solution for later use; S2: Metal chloride, N,N-diisopropylethylamine and tetrahydrofuran solvent are added to a reaction vessel, the temperature is lowered to -10~-5℃, an amine compound is slowly introduced, and after the introduction is completed, the mixture is stirred for 2 hours, and then slowly raised to 30~40℃ and stirred for 16 hours, and the mixture is filtered to obtain a filtrate; S3: The temperature of the filtrate is controlled at 20~30℃, the magnesium thiocene tetrahydrofuran solution is added to it, the temperature is slowly raised to 50~60℃ and stirred for 12 hours, after the stirring is completed, the mixture is filtered to obtain a filtrate, and then the target product CpM(NR1R2)3 is obtained by distillation and rectification.

Description

Technical Field

[0001] This invention relates to the technical field of organometallic source synthesis, and more specifically to a method for preparing metal complexes. Background Technology

[0002] High-k materials are one of the cornerstone technologies for the evolution of integrated circuits toward smaller size and higher performance. By solving key issues such as leakage current and thermal stability, they not only extend the life of Moore's Law, but also provide material support for innovations such as 3D integration and advanced processes. In the future, with the continuous breakthroughs in materials science and process technology, high-k materials will play a more profound role in the field of integrated circuits, driving electronic devices toward higher performance and lower power consumption.

[0003] In semiconductor manufacturing, hafnium-based and zirconium-based high-k dielectric materials (such as HfO2 and ZrO2) have replaced silicon dioxide as the standard for gate dielectric layers in modern logic chips. As transistor structures evolve from planar to three-dimensional (such as FinFETs) and even all-around gates, the requirements for precursors are becoming increasingly stringent. With the continuous miniaturization of chip manufacturing processes, hafnium dioxide / zirconium thin films can avoid the direct electron tunneling problem caused by the interface barrier between the transistor gate dielectric layer and the silicon substrate due to thinning. Hafnium oxide (HfO2) and zirconium oxide (ZrO2) are cornerstones of modern microelectronics technology. As gate dielectric layers, they have successfully solved the physical bottlenecks (such as quantum tunneling effects) of traditional SiO2 in the continuous miniaturization of semiconductor devices, making the continuous miniaturization of transistors possible. Atomic layer deposition (ALD) technology, with its unparalleled film uniformity, precise thickness control, and excellent three-dimensional structure coverage, has become the preferred method for depositing these high-k thin films.

[0004] Current methods for synthesizing high-purity hafnium-zirconium metal complex precursors suffer from numerous problems. Firstly, the synthesis process is often complex, involving multiple reactions and cumbersome separation and purification steps, leading to low production efficiency and high costs. Existing technologies often use the highly unstable cyclopentadiene monomer (CpH) as a raw material. This monomer readily undergoes the Diels-Alder reaction at room temperature, spontaneously dimerizing to dicyclopentadiene (DCPD), and continues to polymerize during storage, transportation, and feeding. This polymerization process exhibits significant temperature dependence; the higher the temperature, the faster the polymerization rate. However, in actual synthesis reactions, the system temperature is typically high, further exacerbating the uncontrolled polymerization of the cyclopentadiene monomer. The direct consequence is that the effective concentration of the raw material cannot remain constant in the reaction system, but rather continuously and unpredictably decreases before and during the reaction. This problem not only leads to decreased raw material utilization and increased costs, but more importantly, it causes the actual effective feed amount of cyclopentadiene to deviate significantly from the preset stoichiometric ratio. Such deviations can trigger a chain of technical problems: the reaction cannot proceed completely according to stoichiometry, resulting in a decrease in the yield of the target product; unreacted reactive intermediates may remain, or uncontrollable side reactions may be induced, generating impurities that are difficult to separate, ultimately damaging the chemical purity of the product and batch-to-batch consistency, severely restricting the reliability and industrial application of the process. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing metal complexes to overcome the above-mentioned shortcomings in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] 1. A method for preparing a metal complex, wherein the general structural formula of the metal complex is CpM(NR1R2)3, wherein R1 and R2 are Me or Et, and M is Zr or Hf;

[0008] The preparation method includes the following steps:

[0009] S1: Add magnesium pyrocene to tetrahydrofuran solvent and stir to form a magnesium pyrocene tetrahydrofuran solution for later use;

[0010] S2: Add metal chloride, N,N-diisopropylethylamine and tetrahydrofuran solvent to the reaction vessel, first cool to -10~-5℃, then slowly pass in amine compounds, stir for 2 hours after the passage is complete, then slowly raise to 30~40℃ and stir for 16 hours, then filter to obtain filtrate.

[0011] S3: Control the temperature of the filtrate at 20~30℃, add a tetrahydrofuran solution of magnesium thiocene, and after the addition is complete, slowly raise the temperature to 50~60℃ and stir for 12 hours. After the stirring reaction is completed, filter to obtain the filtrate, and then separate it by distillation and rectification to obtain the target product CpM(NR1R2)3.

[0012] Preferably, the operations in steps S1-S3 are all carried out under inert gas protection, and the water and oxygen content of the inert gas is less than 1 ppm.

[0013] Preferably, the molar ratio of metal chloride to amine compound is 1:3.3~4.5, and the molar ratio of metal chloride to N,N-diisopropylethylamine is 1:4~5.

[0014] Preferably, the molar ratio of metal chloride to magnesium thiocene is 2:1.1~1.3.

[0015] Preferably, the metal chloride in step S2 is hafnium tetrachloride or zirconium tetrachloride.

[0016] Preferably, the amine compound in step S2 is one of dimethylamine, diethylamine, and methyl ethylamine.

[0017] Preferably, the Zr-containing compound of CpM(NR1R2)3 is CpZr(NMe2)3, CpZr(NEt2)3, or CpZr(NEtMe)3.

[0018] Preferably, the Hf-containing compound of CpM(NR1R2)3 is CpHf(NMe2)3, CpHf(NEt2)3, or CpHf(NEtMe)3.

[0019] In the above technical solution, the method for preparing metal complexes provided by the present invention has the following beneficial effects:

[0020] 1. Addressing the core defect in existing technologies where cyclopentadiene monomers readily dimerize and polymerize at room temperature and reaction temperature, leading to uncontrollable decline in their effective concentration, this invention creatively employs chemically stable and long-term-storeable magnesium pyrocene (Cp2Mg) as the cyclopentadienyl group (Cp... - The quantitative supply source of magnesium pyrocene is a solid crystal at room temperature, and its effective component concentration is constant, allowing for precise weighing and feeding. This substitution fundamentally eliminates the problem of inaccurate feeding caused by spontaneous polymerization of raw materials, ensuring that cyclopentadienyl groups participate in the reaction strictly according to the stoichiometric ratio. This lays the most critical raw material foundation for achieving high-yield and high-selectivity synthesis, and significantly improves the reliability and reproducibility of the process.

[0021] 2. This invention constructs a highly efficient aminolysis reaction system by introducing sterically hindered N,N-diisopropylethylamine as a specific acid scavenger. This organic base can instantly and completely neutralize the hydrogen chloride (HCl) generated in the reaction, strongly driving the aminolysis equilibrium towards the formation of the tris(dialkylamino)chloro metal intermediate MCl(NR2)3. Simultaneously, its steric hindrance prevents unfavorable coordination or competitive reactions with the metal center. This step achieves highly selective modification of the ligand environment of the metal center, providing a clear and singular active intermediate for subsequent transformations.

[0022] 3. Based on the stable raw material supply and highly selective reaction pathway described above, this invention can prepare the target product CpM(NR2)3 with extremely high purity. This method does not use any alkali metal reagents (such as NaCp, LiNMe2) throughout the entire process, completely eliminating the need for (Li...) reagents at the source. + Na + K + The introduction of ).

[0023] 4. The method provided by this invention has a significantly simplified operation process, avoids the separation and purification steps of unstable intermediates, and replaces flammable and explosive alkyl lithium reagents. It has lower operation risks and is more in line with the safety requirements of industrial production.

[0024] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit this disclosure.

[0025] This application provides an overview of various implementations or examples of the technology described in this disclosure, and is not a full disclosure of the entire scope or all features of the disclosed technology. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0027] Figure 1 The NMR spectrum of CpZr(NMe2)3 provided in Example 6 of this invention;

[0028] Figure 2 The NMR spectrum of CpHf(NMe2)3 provided in Example 8 of this invention;

[0029] Figure 3 The nuclear magnetic resonance spectrum of CpZr(NMe2)3 provided for Comparative Example 1 of this invention;

[0030] Figure 4The NMR spectrum of CpHf(NMe2)3 provided for Comparative Example 2 of this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0032] A method for preparing a metal complex, the general structural formula of which is CpM(NR1R2)3, wherein R1 and R2 are Me or Et, and M is Zr or Hf;

[0033] The preparation method includes the following steps:

[0034] S1: Add magnesium pyrocene to tetrahydrofuran solvent and stir to form a magnesium pyrocene tetrahydrofuran solution for later use;

[0035] S2: Add metal chloride, N,N-diisopropylethylamine and tetrahydrofuran solvent to the reaction vessel, first cool to -10~-5℃, then slowly pass in amine compounds, stir for 2 hours after the passage is complete, then slowly raise to 30~40℃ and stir for 16 hours, then filter to obtain filtrate.

[0036] S3: Control the temperature of the filtrate at 20~30℃, add a tetrahydrofuran solution of magnesium pyrocene, and after the addition is complete, slowly raise the temperature to 50~60℃ and stir for 12 hours. After the stirring reaction is completed, filter to obtain the filtrate, and then separate it by distillation and rectification to obtain the target product CpM(NR1R2)3.

[0037] By using magnesium pyrocene (Cp2Mg) as a cyclopentadienyl (Cp - The quantitative supply source of MgO avoids the problem of inaccurate feeding caused by spontaneous polymerization of raw materials. Since MgO is a solid crystal at room temperature, the concentration of effective components is constant, which facilitates accurate weighing and feeding, thus providing a raw material basis for high yield of the final product. By adding N,N-diisopropylethylamine as an acid-binding agent, the hydrogen chloride (HCl) generated in the reaction is neutralized, promoting the aminolysis reaction and avoiding incomplete metal chloride reaction.

[0038] All operations in steps S1-S3 are carried out under inert gas protection, with the inert gas containing less than 1 ppm of water and oxygen.

[0039] The molar ratio of metal chloride to amine compound is 1:3.3~4.5, and the molar ratio of metal chloride to N,N-diisopropylethylamine is 1:4~5.

[0040] The molar ratio of metal chloride to magnesium thiocene is 2:1.1~1.3.

[0041] The metal chloride in step S2 is hafnium tetrachloride or zirconium tetrachloride.

[0042] The amine compound in step S2 is one of dimethylamine, diethylamine, and methyl ethylamine.

[0043] The Zr-containing compounds of CpM(NR1R2)3 are CpZr(NMe2)3, CpZr(NEt2)3, and CpZr(NEtMe)3;

[0044] The Hf-containing compounds of CpM(NR1R2)3 are CpHf(NMe2)3, CpHf(NEt2)3, and CpHf(NEtMe)3.

[0045] The following are embodiments of the present invention:

[0046] Example 1

[0047] In this embodiment:

[0048] The molar ratio of metal chloride to N,N-diisopropylethylamine is 1:4;

[0049] The molar ratio of metal chloride to amine compound is 1:3.3;

[0050] The molar ratio of metal chloride to magnesium thiocene is 2:1.1;

[0051] 1. Under inert gas protection, add 42.5g of magnesium pyrocene and 300mL of tetrahydrofuran solvent to a 1L reaction flask, start stirring, and set aside.

[0052] 2. Add 116.5g of zirconium tetrachloride, 500mL of tetrahydrofuran solvent and 258.6g of N,N-diisopropylethylamine to a 2L reaction flask. First, cool the mixture to -10~-5℃, then slowly introduce 74.4g of dimethylamine. After the introduction is complete, stir for 2 hours, then slowly raise the temperature to 30~40℃ and stir for 16 hours. Filter to obtain the filtrate.

[0053] 3. First, control the temperature of the filtrate at 20~30℃, then slowly add the tetrahydrofuran solution of magnesium pyrocene from step 1. After the addition is complete, slowly raise the temperature to 50~60℃ and stir for 12 hours. After the stirring reaction is completed, filter to obtain the filtrate. Distill the filtrate at 70~90℃ to remove the tetrahydrofuran, and then perform vacuum distillation, controlling the pressure at 1~3 Torr. Collect the fraction at 120~140℃ to obtain 122.6g of the target product cyclopentadiene tris(dimethylamino)zirconium.

[0054] In this case, the yield of cyclopentadiene tri(dimethylamino)zirconium was 87.5%. The product was detected by JNM-ECZ400S nuclear magnetic resonance spectrometer: 1H NMR (400 MHz, C6D6) δ: 6.06 (s, 5H); 2.92 (s, 18H).

[0055] Example 2

[0056] The difference from Example 1 is that the molar ratio of metal chloride to N,N-diisopropylethylamine is 1:4, that is, the amount of N,N-diisopropylethylamine is 290.9g;

[0057] In this case, the yield of cyclopentadiene tri(dimethylamino)zirconium was 86.5%. The product was detected by JNM-ECZ400S nuclear magnetic resonance spectrometer: 1H NMR (400 MHz, C6D6) δ: 6.06 (s, 5H); 2.92 (s, 18H).

[0058] Example 3

[0059] The difference from Example 1 is that the molar ratio of metal chloride to N,N-diisopropylethylamine is 1:5, that is, the amount of N,N-diisopropylethylamine is 323g;

[0060] In this case, the yield of cyclopentadiene tri(dimethylamino)zirconium synthesis was 86.8%. The product was detected by JNM-ECZ400S nuclear magnetic resonance spectrometer: 1H NMR (400 MHz, C6D6) δ: 6.06 (s, 5H); 2.92 (s, 18H).

[0061] Example 4

[0062] The difference from Example 2 is that the molar ratio of the metal chloride to the amine compound is 1:3.9; that is, the dimethylamine content is 87.9 g.

[0063] In this case, the yield of cyclopentadiene tri(dimethylamino)zirconium synthesis was 88.6%. The product was detected by JNM-ECZ400S nuclear magnetic resonance spectrometer: 1H NMR (400 MHz, C6D6) δ: 6.06 (s, 5H); 2.92 (s, 18H).

[0064] Example 5

[0065] The difference from Example 2 is that the molar ratio of the metal chloride to the amine compound is 1:4.5; that is, the dimethylamine is 101.5g.

[0066] In this case, the yield of cyclopentadiene tri(dimethylamino)zirconium synthesis was 88.9%. The product was detected by JNM-ECZ400S nuclear magnetic resonance spectrometer: 1H NMR (400 MHz, C6D6) δ: 6.06 (s, 5H); 2.92 (s, 18H).

[0067] Example 6

[0068] The difference from Example 4 is that the molar ratio of metal chloride to magnesium pyrocene is 2:1.2; that is, the amount of magnesium pyrocene is 46.3 g.

[0069] In this case, the yield of cyclopentadiene tri(dimethylamino)zirconium was 91.5%. The product was detected by JNM-ECZ400S nuclear magnetic resonance spectrometer: 1H NMR (400 MHz, C6D6) δ: 6.06 (s, 5H); 2.92 (s, 18H).

[0070] Example 7

[0071] The difference from Example 4 is that the molar ratio of metal chloride to magnesium pyrocene is 2:1.3; that is, the amount of magnesium pyrocene is 50.2 g.

[0072] In this case, the yield of cyclopentadiene tri(dimethylamino)zirconium was 91.6%. The product was detected by JNM-ECZ400S nuclear magnetic resonance spectrometer: 1H NMR (400 MHz, C6D6) δ: 6.06 (s, 5H); 2.92 (s, 18H).

[0073] Example 8

[0074] In this embodiment:

[0075] The molar ratio of metal chloride to N,N-diisopropylethylamine is 1:4.5;

[0076] The molar ratio of metal chloride to amine compound (dimethylamine) is 1:3.9;

[0077] The molar ratio of metal chloride to magnesium thiocene is 2:1.2;

[0078] The same molar ratio as in Example 6 was used, except that the metal oxide was hafnium tetrachloride, i.e.:

[0079] 1. Under inert gas protection, add 46.4g of magnesium pyrocene and 300mL of tetrahydrofuran solvent to a 1L reaction flask, start stirring, and set aside.

[0080] 2. Add 160.2g hafnium tetrachloride, 600mL tetrahydrofuran solvent and 290.9g N,N-diisopropylethylamine to a 2L reaction flask. First, cool the mixture to -10~-5℃, then slowly introduce 87.9g dimethylamine. After the introduction is complete, stir for 2 hours, then slowly raise the temperature to 30~40℃ and stir for 16 hours. Filter to obtain the filtrate.

[0081] 3. First, control the temperature of the filtrate to 20~30℃, then slowly add the tetrahydrofuran solution of magnesium pyrocene from step 1. After the addition is complete, slowly raise the temperature to 50~60℃ and stir for 12 hours. After the stirring reaction is completed, filter to obtain the filtrate, and then separate it by distillation and rectification to obtain 171g of the target product cyclopentadiene tris(dimethylamino)hafnium.

[0082] In this case, the yield of cyclopentadiene tris(dimethylamino)hafnium was 91%. The product was detected by a JNM-ECZ400S nuclear magnetic resonance spectrometer: 1H NMR (400 MHz, C6D6) δ: 6.04 (s, 5H); 2.96 (s, 18H).

[0083] Comparative Example 1

[0084] 1. Add 500 mL of n-hexane and 500 mL of n-butyllithium (2.5 M) to a 2 L reaction flask, turn on the stirrer and cool to -60~-30℃, then slowly introduce 67.5 g of dimethylamine. After the introduction is complete, raise the temperature to room temperature and maintain stirring for 2 h.

[0085] 2. Cool down to -60~-30℃ again, add 70g of zirconium tetrachloride in batches to the reaction flask, slowly raise to room temperature and reflux for 2 hours after addition, and then reflux for 8~12 hours.

[0086] 3. Cool down to below 10℃ again, and add the freshly prepared 22g cyclopentadiene monomer dropwise into the reaction flask. After the addition is complete, react at room temperature for 6-8 hours.

[0087] 4. After the reaction is complete, the solvent is distilled off at 70~90℃ and normal pressure, and then vacuum distillation is carried out, controlling the pressure at 1~3 Torr. The product is collected at 120~140℃ to obtain 37.7g of crude cyclopentadiene tris(dimethylamino)zirconium.

[0088] In this case, the yield of cyclopentadiene tri(dimethylamino)zirconium synthesis was 43.6%, and the product was confirmed as the target product by a JNM-ECZ400S nuclear magnetic resonance spectrometer.

[0089] Comparative Example 2

[0090] 1. Add 70g hafnium tetrachloride and 500mL n-hexane to a 2L reaction flask, cool to -30~-20℃, introduce 67.5g dimethylamine gas into the reaction flask, and then slowly add 500mL n-butyllithium (2.5M) dropwise into the reaction flask through a constant pressure dropping funnel, controlling the temperature of the reaction system to be below -10℃ during the dropwise addition. After the dropwise addition is completed, slowly raise the temperature to room temperature and stir the reaction for 12h.

[0091] 2. Slowly add 22g of freshly prepared cyclopentadiene into the reaction flask through a constant pressure dropping funnel, keeping the temperature of the reaction system below 10℃ during the addition. After adding the cyclopentadiene, allow the reaction to proceed at room temperature for 6 hours.

[0092] 3. After the reaction is complete, the solvent is distilled off at 70-90℃ and normal pressure, and then vacuum distillation is performed, controlling the pressure at 1-3 Torr. The product is collected at 120-140℃ to obtain 31.1g of crude cyclopentadiene tris(dimethylamino)hafnium.

[0093] In this case, the yield of cyclopentadiene tris(dimethylamino)hafnium was 35.9%, and the product was confirmed as the target product by a JNM-ECZ400S nuclear magnetic resonance spectrometer.

[0094] As can be seen from the above examples and comparative examples, the raw materials selected in this process, including magnesium thiocene, N,N-diisopropylethylamine, diethylamine and dimethylamine, are all commercially available products with a stable supply chain, no need for customization, and can effectively control raw material costs.

[0095] The cyclopentadienyl anion in magnesium thiocene exhibits high selectivity, undergoing a highly selective nucleophilic substitution reaction with the intermediate trichloro(dimethylamino)zirconium to generate the target product. The reaction process is free of side reactions such as multiple substitutions and rearrangements, resulting in minimal impurity formation. After the reaction, insoluble impurities are removed by filtration, followed by a combination of distillation (to remove solvent tetrahydrofuran, excess dimethylamine, and other low-boiling-point components) and rectification to precisely purify the target product, ultimately yielding a high-purity product.

[0096] The chemical reaction formula of this invention is:

[0097] 3HNR1R2+MCl4+3(i-Pr)2NEt→MCl(NR1R2)3+3(i-Pr)2NHEtCl

[0098] 2MCl(NR1R2)3+Cp2Mg→2CpM(NR1R2)3+MgCl2

[0099] Tetrahydrofuran exhibits excellent solubility for magnesium bis(oxocero), zirconium tetrachloride, and hafnium tetrachloride, enabling the reaction to proceed in a homogeneous system. This allows for sufficient contact and reaction of the raw materials without the need for high temperature and pressure, reducing the operational difficulty and safety risks. N,N-diisopropylethylamine, as a tertiary amine, has moderate basicity and significant steric hindrance. It effectively neutralizes the HCl generated in the coordination reaction, promoting the forward reaction, without undergoing additional reactions with the raw materials or products, maintaining system stability and preventing violent reactions. The entire process does not require extreme conditions such as high temperature and pressure, and the use of tetrahydrofuran as a solvent ensures strong system stability, mitigating safety risks under extreme conditions and reducing the investment and maintenance costs of production equipment.

[0100] Detected by a JNM-ECZ400S nuclear magnetic resonance spectrometer, the 1H NMR peaks of the product CpZr(NMe2)3 and the product CpHf(NMe2)3 were both single-shaped (δ: 6.06(s, 5H) corresponds to cyclopentadienyl hydrogen, 2.92(s, 18H) corresponds to dimethylamino hydrogen). There were no obvious impurity peaks, the product structure was uniform, and the purity met the application requirements of high-end organic synthesis, catalysis and other fields.

[0101] By using the same process parameters in Examples 6 and 8, and adjusting the metal chloride to zirconium tetrachloride and hafnium tetrachloride in the same molar ratio, this application can achieve a high yield, effectively demonstrating the universality of this process.

[0102] Instruction manual attached Figure 1 and attached Figure 2 The images show the NMR spectra of CpZr and CpHf from the examples. The NMR spectra indicate that the products are very clean, with no impurity peaks, and high purity. (Comparison with the attached figures...) Figure 1 and Figure 3 ,as well as Figure 2 and Figure 4 The NMR spectra shown in Comparative Examples 1 and 2 show multiple impurity peaks, indicating the presence of byproducts. Compared to this invention, this invention not only further improves purity and yield but also has the advantages of stable raw materials and controllable reaction pathways.

[0103] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for preparing metal complexes, characterized in that, The general structural formula of the metal complex is CpM(NR1R2)3, where R1 and R2 are Me or Et, and M is Zr or Hf. The preparation method includes the following steps: S1: Add magnesium pyrocene to tetrahydrofuran solvent and stir to form a magnesium pyrocene tetrahydrofuran solution for later use; S2: Add metal chloride, N,N-diisopropylethylamine and tetrahydrofuran solvent to the reaction vessel, first cool to -10~-5℃, then slowly pass in amine compounds, stir for 2 hours after the passage is complete, then slowly raise to 30~40℃ and stir for 16 hours, then filter to obtain filtrate. S3: Control the temperature of the filtrate at 20~30℃, add a tetrahydrofuran solution of magnesium thiocene, and after the addition is complete, slowly raise the temperature to 50~60℃ and stir for 12 hours. After the stirring reaction is completed, filter to obtain the filtrate, and then separate it by distillation and rectification to obtain the target product CpM(NR1R2)3.

2. The method for preparing metal complexes according to claim 1, characterized in that, The operations in steps S1-S3 are all carried out under inert gas protection, and the water and oxygen content of the inert gas is less than 1 ppm.

3. The method for preparing metal complexes according to claim 1, characterized in that, The molar ratio of the metal chloride to the amine compound is 1:3.3~4.5, and the molar ratio of the metal chloride to N,N-diisopropylethylamine is 1:4~5.

4. The method for preparing metal complexes according to claim 1, characterized in that, The molar ratio of metal chloride to magnesium thiocene is 2:1.1~1.

3.

5. The method for preparing metal complexes according to claim 1, characterized in that, The metal chloride in step S2 is hafnium tetrachloride or zirconium tetrachloride.

6. The method for preparing a metal complex according to claim 1, characterized in that, The amine compound in step S2 is one of dimethylamine, diethylamine, and methyl ethylamine.

7. The method for preparing metal complexes according to claim 1, characterized in that, The Zr-containing compounds of CpM(NR1R2)3 are CpZr(NMe2)3, CpZr(NEt2)3, and CpZr(NEtMe)3.

8. The method for preparing metal complexes according to claim 1, characterized in that, The Hf-containing compounds of CpM(NR1R2)3 are CpHf(NMe2)3, CpHf(NEt2)3, and CpHf(NEtMe)3.

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