Preparation method of penta (dimethylamino) tantalum

Abstract

The invention discloses a preparation method of penta (dimethylamino) tantalum, and belongs to the technical field of synthesis of metal organic compounds. The method comprises two core processes: firstly, in an inert atmosphere, tantalum metal powder and tin powder are subjected to mechanical activation treatment in an inert hydrocarbon solvent, and an oxide layer on the surface of the tantalum powder is broken to obtain tin activated tantalum powder; then, in an inert atmosphere and a mixed solvent system, dimethylamine gas is introduced into the activated tantalum powder, a composite reducing agent composed of NaBH4 and CuCl2 is added, and penta (dimethylamino) tantalum is generated in one step through a reduction-amination synergistic reaction. Cheap tantalum powder is used as a raw material, a green reduction system is used for replacing a high-risk alkyl lithium reagent, and the method has the outstanding advantages of being low in cost, high in safety, good in product purity, high in reaction efficiency and the like and is suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, and in particular to a method for preparing penta(dimethylamino)tantalum. Background Technology

[0002] Pentamethylaminotantalum is an important organometallic precursor widely used in chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes to prepare high-performance tantalum nitride and tantalum pentoxide thin films. These films play a crucial role in semiconductor integrated circuits, dynamic random access memory (DRAM), copper interconnect diffusion barrier layers, and high-dielectric-constant gate dielectrics. Furthermore, due to its unique chemical properties, pentamethylaminotantalum also holds significant research value in organic synthesis, coordination chemistry, and materials science.

[0003] CN106916072A discloses a method for synthesizing penta(dimethylamino)tantalum, which involves mixing TaCl5 with excess dimethylamine in an alkane solvent at a low temperature, reacting at 0–-30°C for 8–12 hours, then adding excess n-butyllithium hexane solution, reacting at 0–-30°C for 4–20 hours, and finally purifying to obtain PDMAT. This reaction has a long synthesis time and uses expensive and highly flammable n-butyllithium, resulting in high synthesis costs and significant operational hazards.

[0004] CN110698347B discloses a method for synthesizing penta(dimethylamino)tantalum. The method involves dissolving butyl magnesium chloride in tetrahydrofuran solution, adding a co-catalyst, and introducing dimethylamine gas to obtain di(dimethylamino)magnesium. This di(dimethylamino)magnesium is then reacted with tantalum pentachloride for 10-20 hours to obtain the final product. This method uses Grignard reagents instead of n-butyllithium, reducing operational risks; however, it requires the synthesis of a co-catalyst, making the operation cumbersome, and the longer reaction time increases time costs.

[0005] Currently, the classic method for preparing penta(dimethylamino)tantalum typically uses tantalum pentachloride as the starting material, undergoing an amination reaction with excess dimethylaminolithium or other strong nucleophiles. While these methods are feasible, they have several inherent drawbacks: First, TaCl5 itself is expensive and highly hygroscopic and corrosive, making it inconvenient to handle; second, the reaction produces a large amount of lithium chloride as a byproduct, which may be encapsulated in the product or form adducts, making it difficult to remove completely, resulting in a high chlorine impurity content in the final product. Chlorine impurities can severely impair the electrical performance and reliability of devices in semiconductor processes; furthermore, reagents such as dimethylaminolithium or n-butyllithium are expensive, extremely sensitive to water and oxygen, and n-butyllithium is flammable, requiring stringent storage and usage conditions, posing significant safety risks and difficulties in process control.

[0006] Therefore, there is an urgent need in this field to develop a novel method for preparing penta(dimethylamino)tantalum that can avoid the introduction of chlorine from the source, use safer and cheaper reagents, and achieve the preparation of high-purity products. Summary of the Invention

[0007] The primary objective of this invention is to address the aforementioned deficiencies in existing technologies by providing a novel strategy for the preparation of penta(dimethylamino)tantalum. This method aims to avoid the introduction of chlorine impurities at the source, thereby improving product purity; to use safer and cheaper raw materials and reagents, reducing production costs and operational risks; and to improve reaction efficiency and atom economy through pathway innovation.

[0008] The technical problem solved by this invention is achieved by the following technical solution: A method for preparing penta(dimethylamino)tantalum, the specific scheme of which is as follows: (1) Activation treatment: In an inert atmosphere of argon or nitrogen, tantalum metal powder and tin powder are added to an inert hydrocarbon solvent and mechanically activated by ball milling or ultrasound to obtain tin-activated tantalum powder. This step can effectively break the oxide layer on the surface of tantalum powder and significantly improve the reactivity of tantalum.

[0009] (2) Coupled reduction amination reaction: Under an inert atmosphere, a mixed solvent is added to the tin-activated tantalum powder obtained in step (1), followed by the addition of a composite reducing agent. The system temperature is controlled between -20℃ and 0℃, and dimethylamine gas is slowly introduced. Then, the reaction is carried out at a constant temperature of 40℃-80℃ for 10-48h. After the reaction is completed, a reaction solution is obtained. The composite reducing agent can generate a highly active intermediate in the system. On the one hand, it reduces the tantalum surface, and on the other hand, it works synergistically with dimethylamine to achieve the stepwise amination of tantalum and generate penta(dimethylamino)tantalum crude product in one step.

[0010] (3) Purification: The reaction solution obtained in step (2) is filtered to remove impurities, and the solvent is recovered by vacuum distillation to obtain crude product. Then, a unique two-stage sublimation combined with molecular sieve adsorption process is used for purification: first, primary sublimation is carried out at a lower temperature and pressure to remove volatile impurities, and then final purification is carried out in a distillation sublimation tower with integrated molecular sieve adsorption column at a higher temperature and high vacuum. The molecular sieve can selectively adsorb residual tin-containing by-products, thereby obtaining high-purity penta(dimethylamino)tantalum.

[0011] As a preferred technical solution, in step (1), the molar ratio of tantalum metal powder to tin powder is 5:1-20:1.

[0012] As a preferred technical solution, in step (1), the mechanical activation treatment is ball milling or ultrasonic treatment, and the treatment time is 2-6 hours.

[0013] As a preferred technical solution, in step (1), the inert hydrocarbon solvent is n-hexane, cyclohexane, or toluene.

[0014] As a preferred technical solution, in step (2), the composite reducing agent is composed of NaBH4 and CuCl2, wherein the molar ratio of NaBH4 to CuCl2 is 1:1-4:1; the amount of the composite reducing agent added is calculated based on NaBH4, and the molar ratio of it to tantalum metal powder is 1:1-10:1; the molar ratio of the amount of dimethylamine gas introduced to the molar ratio of it to tantalum metal powder is not less than 5:1.

[0015] As a preferred technical solution, in step (2), the composite reducing agent is composed of LiAlH4 and ZnCl2, wherein the molar ratio of LiAlH4 to ZnCl2 is 1:1-4:1; the amount of the composite reducing agent added is calculated based on LiAlH4, and the molar ratio of it to tantalum metal powder is 1:1-10:1; the molar ratio of the amount of dimethylamine gas introduced to the molar ratio of it to tantalum metal powder is not less than 5:1.

[0016] As a preferred technical solution, the mixed solvent is a mixture of an inert hydrocarbon solvent and tetrahydrofuran, with a volume ratio of 3:1 to 5:1.

[0017] As a preferred technical solution, in step (2), the mixed solvent is a mixture of an inert hydrocarbon solvent and tetrahydrofuran, with a volume ratio of 3:1 to 5:1.

[0018] As a preferred technical solution, in step (2), the temperature of the isothermal reaction is 40°C to 80°C, and the reaction time is 10-48 hours.

[0019] As a preferred technical solution, the sublimation device includes a primary sublimation chamber and a distillation sublimation column; the distillation sublimation column integrates a molecular sieve adsorption column.

[0020] As a preferred technical solution, the conditions for primary sublimation are: temperature 40-70℃ and pressure 0.1-1.0kPa; the conditions for distillation sublimation are: temperature 60-90℃ and pressure 0.01-0.5kPa.

[0021] As a preferred technical solution, the molecular sieve is a 3A, 4A or 5A type molecular sieve, used to adsorb residual tin-containing by-products and small molecule impurities.

[0022] The beneficial effects of this invention are as follows: (1) The raw material cost is low. Inexpensive tantalum powder is used directly as the tantalum source, and the less expensive NaBH4 / CuCl2 composite reducing agent is used to partially or completely replace the expensive alkyl lithium reagent, which greatly reduces the raw material cost.

[0023] (2) The operation is safe, avoiding the use of alkyl lithium reagents with spontaneous combustion risk and corrosive TaCl5. The whole process is safer and the requirements for equipment and operation are relatively relaxed.

[0024] (3) The product has high purity. Through the synergistic effect of tin powder activation and composite reducing agent, the generation of halogenated byproducts is avoided.

[0025] (4) By using the synergistic design of “tin activation” and “coupled reduction amination”, the problem of low reactivity of tantalum metal was solved, creating a new synthetic route with higher atom economy and simpler steps. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 The 1H NMR spectrum of the penta(dimethylamino)tantalum prepared in Example 1. Detailed Implementation

[0028] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention is further described below.

[0029] The reagents or equipment used in the following examples are all commercially available.

[0030] Example 1 This invention proposes a method for preparing penta(dimethylamino)tantalum, the specific steps of which are as follows: (1) Activation treatment: Under nitrogen protection, 10g of tantalum metal powder, 0.7g of tin powder, and 200mL of n-hexane were added to a 500mL ball mill jar. The ball milling speed was set to 400r / min, and the mixture was milled for 4h to obtain tin-activated tantalum powder. It is worth noting that the nitrogen in this example can be replaced by an inert atmosphere such as argon, and the n-hexane in this example can be replaced by an inert hydrocarbon solvent such as cyclohexane or toluene. Inert hydrocarbon solvents have good stability and low reactivity, and can effectively disperse the reactants without participating in side reactions.

[0031] (2) Coupled Reductive Amination Reaction: In a 500 mL three-necked flask under nitrogen protection, all the tin-activated tantalum powder obtained in step (1) was added, along with 150 mL of mixed solvent (n-hexane:tetrahydrofuran = 4:1, volume ratio), and the mixture was stirred and cooled to -10 °C. Subsequently, a composite reducing agent consisting of 4.2 g NaBH4 and 7.5 g CuCl2 was added, and the mixture was stirred until homogeneous. Dimethylamine gas was slowly introduced at a rate of 0.2 L / h, with a total amount of 8.5 g (molar ratio with tantalum metal powder 7:1), and the reaction was carried out at a constant temperature of 60 °C for 24 h. It is worth noting that the aforementioned composite reducing agent can be replaced by a mixture of LiAlH4 and ZnCl2, such as 4.2 g LiAlH4 and 7.5 g ZnCl2. In this example, n-hexane can be replaced by inert hydrocarbon solvents such as cyclohexane or toluene. Inert hydrocarbon solvents have good stability and low reactivity, effectively dispersing the reactants without participating in side reactions.

[0032] (3) Purification: After the reaction was completed, the reaction solution was filtered and most of the solvent was removed by vacuum distillation at 40°C to obtain a brownish-yellow crude product. The crude product was transferred to a two-stage sublimation apparatus. First, it was kept in the primary sublimation chamber at 60°C / 0.5 kPa for 2 hours to remove volatile impurities. Then, the material was transferred to a distillation sublimation column and sublimated at 80°C / 0.1 kPa. The sublimation product was passed through an adsorption column packed with 4A molecular sieves to obtain 19.1 g of pure penta(dimethylamino)tantalum.

[0033] The reaction equation of this invention is as follows: .

[0034] The yield of penta(dimethylamino)tantalum synthesized in this experiment was 89%.

[0035] Example 2 Unlike Example 1, only the molar ratio of NaBH4 and CuCl2 in the second step was changed.

[0036] In Group 1, the molar ratio of NaBH4 to CuCl2 is 1:1, meaning the amount of CuCl2 used is 15g, with other conditions remaining unchanged.

[0037] After product collection and purification, 19.3 g of penta(dimethylamino)tantalum was obtained, with a yield of 87%.

[0038] Group 2, the molar ratio of NaBH4 to CuCl2 is 4:1, that is, the amount of CuCl2 used is 3.8g, and other conditions remain unchanged.

[0039] After product collection and purification, 17.7 g of penta(dimethylamino)tantalum was obtained, with a yield of 80%.

[0040] Conclusion: The optimal molar ratio of NaBH4 to CuCl2 is 2:1.

[0041] Example 3 Unlike Example 1, only the molar ratio of NaBH4 and tantalum metal powder in the second step was changed.

[0042] In Group 3, the molar ratio of NaBH4 to tantalum metal powder is 1:1, that is, the amount of NaBH4 is 2.1g and the amount of CuCl2 is 3.8g, with other conditions remaining unchanged.

[0043] After product collection and purification, 18.3 g of penta(dimethylamino)tantalum was obtained, with a yield of 82%.

[0044] Group 4, the molar ratio of NaBH4 to tantalum metal powder is 5:1, that is, the amount of NaBH4 is 10.5g and the amount of CuCl2 is 18.8g, and other conditions remain unchanged.

[0045] After product collection and purification, 19.1 g of penta(dimethylamino)tantalum was obtained, with a yield of 86%.

[0046] Conclusion: The optimal molar ratio of NaBH4 to tantalum metal powder is 2:1. Example 4 Unlike Example 1, only the reaction temperature in the second step was changed.

[0047] Group 5, reaction temperature 40℃, other conditions unchanged.

[0048] After product collection and purification, 17.7 g of penta(dimethylamino)tantalum was obtained, with a yield of 78%.

[0049] Group 6, reaction temperature is 80℃, other conditions remain unchanged.

[0050] After product collection and purification, 17.9 g of penta(dimethylamino)tantalum was obtained, with a yield of 81%.

[0051] Conclusion: The optimal reaction temperature for the second step is 60℃.

[0052] Table 1 Comparison of Test Results .

[0053] The test results show that the preparation method of penta(dimethylamino)tantalum described in this invention has a high yield. The highest yield is achieved when the ratio of NaBH4:CuCl2 is 2:1, the ratio of NaBH4:Ta is 2:1, and the reaction temperature in the second step is 60°C.

[0054] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing penta(dimethylamino)tantalum, characterized in that, Includes the following steps: (1) Activation treatment Tantalum metal powder and tin powder are added to an inert hydrocarbon solvent under an inert atmosphere and mechanically activated to obtain tin-activated tantalum powder. (2) Coupled reductive amination reaction: Under an inert atmosphere, a mixed solvent was added to the tin-activated tantalum powder obtained in step (1), followed by the addition of a composite reducing agent. The system temperature was controlled between -20℃ and 0℃. Dimethylamine gas was slowly introduced, and then the reaction was carried out at a constant temperature of 40℃-80℃ for 10-48h. After the reaction was completed, the reaction solution was obtained. (3) Purification: The reaction solution obtained in step (2) is post-processed to obtain crude penta(dimethylamino)tantalum, which is then purified by a sublimation device to obtain high-purity penta(dimethylamino)tantalum.

2. The method according to claim 1, characterized in that, In step (1), the molar ratio of tantalum metal powder to tin powder is 5:1-20:

1.

3. The method according to claim 1, characterized in that, In step (1), the mechanical activation treatment is ball milling or ultrasonic treatment, and the treatment time is 2-6 hours.

4. The method according to claim 1, characterized in that, In step (2), the composite reducing agent is composed of NaBH4 and CuCl2, wherein the molar ratio of NaBH4 to CuCl2 is 1:1-4:1; the amount of the composite reducing agent added is calculated based on NaBH4, and the molar ratio of it to tantalum metal powder is 1:1-10:1; the molar ratio of the amount of dimethylamine gas introduced to tantalum metal powder is not less than 5:

1. or In step (2), the composite reducing agent is composed of LiAlH4 and ZnCl2, wherein the molar ratio of LiAlH4 to ZnCl2 is 1:1-4:1; the amount of the composite reducing agent added is calculated based on LiAlH4, and the molar ratio of it to tantalum metal powder is 1:1-10:1; the molar ratio of the amount of dimethylamine gas introduced to tantalum metal powder is not less than 5:

1.

5. The method according to claim 1, characterized in that, The mixed solvent is a mixture of an inert hydrocarbon solvent and tetrahydrofuran, with a volume ratio of 3:1 to 5:

1.

6. The method according to claim 1 or 5, characterized in that, In step (1), the inert hydrocarbon solvent is n-hexane, cyclohexane, or toluene.

7. The method according to claim 1, characterized in that, In step (3), the post-processing steps include filtering the reaction solution to remove impurities and recovering the solvent by vacuum distillation.

8. The method according to claim 1, characterized in that, In step (3), the sublimation device includes a primary sublimation chamber and a distillation sublimation tower; the distillation sublimation tower is equipped with a molecular sieve adsorption column.

9. The method according to claim 9, characterized in that, The conditions for the primary sublimation are: temperature 40-70℃, pressure 0.1-1.0kPa; The conditions for the distillation and sublimation are: temperature 60-90℃ and pressure 0.01-0.5kPa.

10. The method according to claim 9, characterized in that, The molecular sieve is a 3A, 4A, or 5A type molecular sieve, used to adsorb residual tin-containing byproducts and small molecule impurities.

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