CN101792469A - Ultrasonic assisted method for synthesizing lanthanum tris[bis(trimethylsilyl)amide] - Google Patents

Abstract

The invention discloses an ultrasonic-assisted method for synthesizing tris[N,N-bis(trimethylsilyl)amine]lanthanum. Ultrasonic waves of specific frequencies are used to greatly promote the solvation of lanthanum chloride to increase its solubility and reactivity, thereby increasing the conversion rate of the reaction. According to the technical scheme of the present invention, the raw materials are easy to obtain, the synthesis route is simple, the operation is convenient, the cycle is short, the consumption of solvent is less, and the yield is higher, and the tris[N,N-bis(trimethylsilyl)amine can be synthesized more economically. ]lanthanum.

Description

A kind of method for synthesizing three [N, N-bis(trimethylsilyl)amine] lanthanum assisted by ultrasound

Technical field:

The invention relates to a method for synthesizing metal-organic complexes under the promotion of ultrasound, in particular to a method for synthesizing tris[N,N-bis(trimethylsilyl)amine]lanthanum assisted by ultrasound.

Background technique:

With the rapid development of microelectronics technology, when the feature size of integrated circuits develops to 45nm technology node and below, the traditional gate dielectric material _SiO2 can no longer meet the requirements and will be replaced by high dielectric constant (high K) materials.

L，J，

J，et al.phys.stat.sol.(a)，2004，201(7)：1443～1452.)。除此之外，稀土氧化物由于具有很高的稳定性和优异的电学性能，也是一种非常有前景的高K材料(

M，Ritala M.J.Solid State Chem.，2003，171(1-2)：170～174.)。其中，La₂O₃(k＝30)的介电常数比HfO₂还要高，因此La₂O₃可能是继HfO₂之后的新一代高k材料。为了制备出高质量的La₂O₃薄膜材料，寻找合适的前驱体起到至关重要的作用。Finding a suitable high-K material to replace SiO ₂ with a dielectric constant of only 3.9 is an arduous and urgent task. In recent years, the three most studied high-K materials are ZrO ₂ (dielectric constant k=25), HfO ₂ (k=25) and Al ₂ O ₃ (k=9)(

L, J,

J, et al.phys.stat.sol.(a), 2004, 201(7): 1443-1452.). In addition, rare earth oxides are also very promising high-K materials due to their high stability and excellent electrical properties (

M, Ritala MJ Solid State Chem., 2003, 171(1-2): 170-174.). Among them, the dielectric constant of La ₂ O ₃ (k=30) is higher than that of HfO ₂ , so La ₂ O ₃ may be a new generation of high-k material after HfO ₂ . In order to prepare high-quality La ₂ O ₃ thin film materials, finding suitable precursors plays a crucial role.

Tris[N,N-bis(trimethylsilyl)amine]lanthanum (La[N(SiMe ₃ ) ₂ ] ₃ ) is a very good precursor for preparing La ₂ O ₃ thin films, which can be deposited by chemical vapor deposition (CVD) or atomic layer deposition (ALD) process to prepare La ₂ O ₃ thin films (Inman R, Schuetz S A, Silvernail CM, et al. Materials Chemistry and Physics, 2007, 104: 220-224.). In addition, La[N(SiMe ₃ ) ₂ ] ₃ is also a very important catalyst and reaction precursor (Qian Changtao, Du Canping. Organic Chemistry of Rare Earth Metals. Beijing: Chemical Industry Press, 2004.62～104.) .

All in all, La[N(SiMe ₃ ) ₂ ] ₃ has very broad application prospects. However, the currently used synthetic methods have expensive raw materials, cumbersome routes, long cycles, low yields, and low economic benefits. The methods reported at home and abroad can be divided into the following categories:

(1) In 1973, Donald C. Bradley synthesized La[N(SiMe ₃ ) ₂ ] ₃ for the first time (Bradley D C, Ghotra J S, Hart F AJ Chem. Soc. Dalton. Trans., 1973: 1021-1023.). The method is to use THF (tetrahydrofuran) as a solvent under the protection of an inert gas, react LaCl ₃ with bis(trimethylsilyl)amide LiN(SiMe ₃ ) ₂ at room temperature for 24 hours, and then remove the solvent to obtain a solid residue . Then the solid residue was extracted with n-pentane, and La[N(SiMe ₃ ) ₂ ] ₃ was obtained by recrystallization (63% yield), and finally the product was further purified by sublimation.

However, the yields were not reproducible due to the poor solubility of _LaCl3 in THF. Recently, when Peter B. Hitchcock et al. studied the synthesis method of Ln[N(SiMe ₃ ) ₂ ] ₃ (Ln represents lanthanides), they also questioned the yield of the literature: LnCl ₃ and LiN(SiMe ₃ ) ₂ as the starting material in THF, the yield is only 17% (Peter B. Hitchcock, Alexander G. Hulkes, Michael F. Lappert, Zhengning Li. Dalton Trans., 2004, 129-136.).

(2) In 2001, the John A.Belot group improved the synthesis method (Steven A.Schuetz, Victor W.Day, Roger D.Sommer, et al.Inorg.Chem.2001, 40, 5292-5295.) . Using lanthanum trifluoromethanesulfonate La(OTf) ₃ and sodium bis(trimethylsilyl)amide NaN(SiMe ₃ ) ₂ , after refluxing in a mixed solvent of n-heptane and THF for 36 hours, the solvent was removed, Pure La[N(SiMe ₃ ) ₂ ] ₃ was obtained by sublimation (57% yield). Although La(OTf) ₃ can replace LaCl ₃ , the price of La(OTf) ₃ is much more expensive than LaCl ₃ , and the economical efficiency of this synthesis process is poor.

(3) In 2002, the group of Jean-Franois Carpentier proposed another method (Dash A K, Razavi A, Mortreux A, et al. Organometallics, 2002, 21(15): 3238-3249.). Firstly, LaCl ₃ was repeatedly extracted with a large amount of THF under heating and reflux, and then the resulting solution was evaporated to dryness to separate the solvated LaCl ₃ (THF) _x . Using toluene as a solvent, LaCl ₃ (THF) _x and LiN(SiMe ₃ ) ₂ were reacted at room temperature for 72 hours, and the lithium chloride generated by the reaction was removed by filtration, and then the solvent was removed, and pure La[N( SiMe ₃ ) ₂ ] ₃ (58% yield). In this method, the authors use solvated lanthanum trichloride LaCl ₃ (THF) _x to increase its solubility in the solvent to increase the conversion rate of LaCl ₃ .

However, the solubility of _LaCl3 in THF at room temperature is 0.126 g, and the effect of temperature on solubility promotion is not obvious. The disadvantage of this method is that a large amount of THF must be refluxed for a long time to repeatedly extract LaCl ₃ , and finally the solvent is evaporated to dryness to prepare LaCl ₃ (THF) _x , which is cumbersome and wastes solvent.

In addition, the composition of LaCl ₃ (THF) _x is not fixed (x=1.5～2.0), x=1.5 (K.Rossmanith, C.Auer-Welsbach.Monatsh.Chem., 1965,96,602.), x=2.0( Glen B. Deacon, Tiecheng Feng, Siegbert Nickel, et al. J. Chem. Soc., Chem. Commun., 1993, 1328-1329.). Therefore, it is troublesome to accurately know the content of lanthanum in LaCl ₃ (THF) _x (it must be tested), which brings difficulties to the quantification of the next reaction.

Invention content:

The object of the present invention is to provide a method for synthesizing tris[N,N-bis(trimethylsilyl)amine]lanthanum assisted by ultrasound to address the shortcomings of existing synthesis methods. Ultrasonic waves with a certain frequency and power greatly promote the solvation of lanthanum chloride to increase its solubility and reactivity, thereby increasing the conversion rate of the reaction. The technical solution of the invention has easy-to-obtain raw materials, simple synthesis route, convenient operation, short cycle, less solvent consumption, high yield and good economy.

In order to simplify the process and improve the yield, in the technical solution of the present invention, the cavitation of the solvent by ultrasonic waves of a specific frequency is utilized, and the high temperature and high pressure and the huge shock wave locally generated when the cavitation bubbles collapse, have an effect on the _LaCl solid particles. Strong "washing" and "etching" action, thus greatly promoting the solvation of _LaCl3 . After LaCl ₃ is solvated by ultrasound, its reactivity is greatly improved, and the reaction can be completed quickly by directly adding LiN(SiMe ₃ ) ₂ without separating the activated LaCl ₃ .

A method for ultrasonically assisted synthesis of three [N, N-bis(trimethylsilyl)amine] lanthanum, wherein the steps are as follows:

Under the protection of an inert gas, add 5-20 mL of anhydrous solvent per gram of anhydrous lanthanum chloride, and apply an ultrasonic field for 1-4 hours to fully solvate it. Remove the ultrasonic field, then add lithium bis(trimethylsilyl)amide, wherein the molar ratio of lithium bis(trimethylsilyl)amide to anhydrous lanthanum chloride is 3:1, stir at room temperature for 10~ 60 min; the solvent in the solution was pumped out with an oil pump to obtain an off-white solid, and the off-white solid was sublimed to obtain pure tris[N,N-bis(trimethylsilyl)amine]lanthanum.

Another ultrasonic-assisted method for synthesizing three [N, N-bis(trimethylsilyl)amine] lanthanum, wherein the steps are as follows:

Under the protection of an inert gas, add anhydrous lanthanum chloride and lithium bis(trimethylsilyl)amide into the anhydrous solvent at a molar ratio of 1:3, wherein 5-20 mL of anhydrous lanthanum chloride is added to each gram of anhydrous lanthanum chloride Anhydrous solvent, after stirring for 5 minutes at room temperature and applying an ultrasonic field for 1 to 4 hours, the solution gradually becomes a clear solution. Use an oil pump to remove the solvent in the solution to obtain an off-white solid, which can be sublimed to obtain pure tris[N,N-bis(trimethylsilyl)amine]lanthanum.

The aforementioned inert gas is nitrogen or argon.

The above-mentioned anhydrous solvent is diethyl ether, ethylene glycol dimethyl ether, tetrahydrofuran, toluene, n-hexane or a mixed solvent in which any two of the above-mentioned solvents are mixed in a ratio of 0.1-0.9. A preferred solvent is tetrahydrofuran.

The frequency range of the above-mentioned ultrasonic field is 25-600KHz, and the output power range is 10-3000W.

The preferred frequency of the above-mentioned ultrasonic field is 40-100KHz, and the preferred power is 50-200W.

Beneficial effect:

1. The raw materials LaCl ₃ and LiN(SiMe ₃ ) ₂ used in the present invention can be conveniently prepared from cheap and readily available lanthanum oxide and hexamethyldisilazane.

2. Ultrasound greatly promotes the solvation of lanthanum chloride. The solubility of LaCl ₃ in aprotic solvents is very poor (even in the most ideal solvent THF, the solubility is only 0.126g/100mL THF), and the insoluble lanthanum chloride reacts very slowly with LiN(SiMe ₃ ) ₂ . Therefore the fast solvation of lanthanum chloride is the key of the present invention.

The present invention utilizes ultrasonic waves of a specific frequency to greatly promote the solvation of lanthanum chloride to increase its solubility and reactivity. Compared with the method reported in the literature that first extracts LaCl ₃ with a large amount of THF to prepare and separate LaCl ₃ (THF) _x , it saves a lot of solvent and time, and the experimental operation is also greatly simplified.

3. The time required for the preparation of the product of the present invention only needs several hours, which saves a lot of time compared with the tens of hours required by the existing technology; and the product yield increases from 17 to 63% to 82 to 94%.

Detailed ways:

The following examples are only used to illustrate the present invention, and do not constitute any limitation to the protection scope of the present invention.

Example 1

Preparation of Anhydrous Lanthanum Chloride

Slowly add 1:1 dilute hydrochloric acid (about 20 mL) and NH ₄ Cl (10.0 g) to La ₂ O ₃ (5.0 g), reflux until dissolved, then gradually evaporate water to obtain a white solid. The white solid was transferred to a quartz tube and fired in a tube furnace. Under the condition of vacuuming at 200-470° C., firing for 12 hours, an off-white solid (7.2 g) was obtained with a yield of 95.3%. Lanthanum chloride must be sealed and stored under the protection of inert gas. (Cox D E, Fong F KJof Crystal Growth, 1973, 20(3): 233～238.)

Example 2

Synthesis of lithium bis(trimethylsilyl)amide

Mikko Ritala，Markku

Chem.Vap.Deposition.2007，13，546-552.)Under the protection of an inert gas, THF (about 30 mL) was added to the Schlenk tube, and then the Schlenk tube was placed in a low-temperature reactor at -78°C. Measure n-butyllithium (15.0mL, 30.0mmol) with a syringe, and quickly transfer it to a Schlenk tube, then weigh HN(SiMe ₃ ) ₂ (4.842g, 30.0mmol) with a syringe, and slowly add it dropwise to the Schlenk tube After 3 hours of reaction, the low-temperature reactor was removed, and then the reaction was continued for another 3 hours at room temperature to obtain a colorless solution for use. (Kaupo Kukli, Timo

Mikko Ritala, Markku

Chem.Vap.Deposition.2007, 13, 546-552.)

Example 3

Synthesis of Tris[N,N-bis(trimethylsilyl)amine]lanthanum

Under the protection of inert gas, weigh LaCl ₃ (2.453g, 10mmol) and add in the Schlenk tube, then add THF (about 40mL), then place the Schlenk tube on the ultrasonic generator (frequency is 40KHz, power 100W), react The system immediately turned milky white, and LaCl ₃ was dispersed very uniformly in THF. After 2 hours of ultrasound, the ultrasonic generator was removed.

At room temperature, the THF solution of LiN(SiMe ₃ ) ₂ (30mmol) synthesized in Example 2 was added dropwise to the system, and the reaction system immediately changed from milky white to a colorless transparent solution ( _LaCl after ultrasonic activation was dissolved in LiN(SiMe ₃ ) ₂ reacts very rapidly). After continuing to stir for 0.5h, the solvent was removed to obtain an off-white solid. In the glove box, the off-white solid was transferred to a sublimator. The crude product was purified by sublimation to obtain 5.352 g of white crystals with a yield of 86.3%. Its melting point is measured at 147-149°C by sealing the tube. Calcd for C ₁₈ H ₅₄ LaN ₃ Si ₆ : C, 34.87; H, 8.78; La, 22.40; N, 6.78. Found: C, 34.63; H, 8.33; La, 22.27; determined by titration). ¹ H NMR (δ, C ₆ D ₆ , Si(CH ₃ ) ₃ ): 0.28.

Example 4

Synthesis of tris[N,N-bis(trimethylsilyl)amine]lanthanum (second operating process)

Under the protection of an inert gas, weigh LaCl ₃ (2.453g, 10mmol) into the Schlenk tube, then add THF (about 40mL), then the THF solution of LiN(SiMe ₃ ) ₂ (30mmol) synthesized in Example 2 Add dropwise to the system. After stirring at room temperature for 5 minutes to make preliminary mixing, the Schlenk tube was placed on an ultrasonic generator (frequency 40KHz, power 100W) for 4 hours, and the solvent was removed to obtain an off-white solid. In the glove box, the off-white solid was transferred to a sublimator. The crude product was purified by sublimation to obtain 5.104 g of white crystals with a yield of 82.3%. Its melting point is measured at 148-149°C by sealing the tube. Calcd for C ₁₈ H ₅₄ LaN ₃ Si ₆ : C, 34.87; H, 8.78; La, 22.40; N, 6.78. Found: C, 34.92; H, 8.57; Titration method). ¹ H NMR (δ, C ₆ D ₆ , Si(CH ₃ ) ₃ ): 0.28.

Example 5

Synthesis of Tris[N,N-bis(trimethylsilyl)amine]lanthanum

Under the protection of an inert gas, weigh LaCl ₃ (2.453g, 10mmol) into the Schlenk tube, then add THF (about 20mL) and toluene (about 20mL), then place the Schlenk tube in an ultrasonic generator (frequency 40KHz, power 100W), remove the ultrasonic generator after 2 hours of ultrasonication.

At room temperature, the THF solution of LiN(SiMe ₃ ) ₂ (30 mmol) synthesized in Example 2 was added dropwise to the system, and the reaction system immediately changed from milky white to a colorless transparent solution. After continuing to stir for 0.5h, the solvent was removed to obtain an off-white solid. In the glove box, the off-white solid was transferred to a sublimator. The crude product was purified by sublimation to obtain 5.215 g of white crystals with a yield of 84.1%.

Example 6.

Synthesis of Tris[N,N-bis(trimethylsilyl)amine]lanthanum

Under the protection of an inert gas, weigh LaCl ₃ (2.453g, 10mmol) into the Schlenk tube, then add THF (about 40mL), then place the Schlenk tube on an ultrasonic generator (frequency is 100KHz, power 200W), ultrasonic After 2h, the ultrasonic generator was removed.

At room temperature, the THF solution of LiN(SiMe ₃ ) ₂ (30 mmol) synthesized in Example 2 was added dropwise to the system, and the reaction system immediately changed from milky white to a colorless transparent solution. After continuing to stir for 0.5h, the solvent was removed to obtain an off-white solid. In the glove box, the off-white solid was transferred to a sublimator. The crude product was purified by sublimation to obtain 5.676 g of white crystals with a yield of 91.5%.

Example 7

Synthesis of Tris[N,N-bis(trimethylsilyl)amine]lanthanum

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Under the protection of an inert gas, weigh LaCl ₃ (2.453g, 10mmol) into the Schlenk tube, then add THF (about 40mL), then place the Schlenk tube on an ultrasonic generator (frequency is 100KHz, power 200W), ultrasonic After 4h, the ultrasonic generator was removed.

At room temperature, the THF solution of LiN(SiMe ₃ ) ₂ (30 mmol) synthesized in Example 2 was added dropwise to the system, and the reaction system immediately changed from milky white to a colorless transparent solution. After continuing to stir for 0.5h, the solvent was removed to obtain an off-white solid. In the glove box, the off-white solid was transferred to a sublimator. The crude product was purified by sublimation to obtain 5.843 g of white crystals with a yield of 94.2%.

Embodiment 8-14

An ultrasonic-assisted method for synthesizing tris[N,N-bis(trimethylsilyl)amine]lanthanum, its substances and reaction conditions are shown in Table 1, and the others are the same as in Example 3.

Substance and reaction conditions in table 1 embodiment 8～14

Example 8 9 10 11 12 13 14 LaCl ₃ mmol 10 10 10 10 10 10 10 LiN(SiMe ₃ ) ₂ mmol 30 30 30 30 30 30 30 Ether mL 40 / / / / 20 / Ethylene glycol dimethyl ether mL / 30 / / / 20 10 Tetrahydrofuran mL / / 20 / / / / Toluene mL / / / 30 / / 20 n-Hexane mL / / / / 20 / / Ultrasound time h 4 4 3 3 3 2 2 Stirring time min 10 30 40 30 40 50 60 Ultrasonic field frequency KHz 25 40 70 100 400 500 600 Output power W 10 50 150 200 800 1500 3000 White crystal g 5.277 5.252 5.742 5.283 5.407 5.791 5.810 Yield 85.1% 84.7% 92.6% 85.2% 87.2% 93.4% 93.7%

Examples 15-21

An ultrasonic-assisted method for synthesizing tris[N,N-bis(trimethylsilyl)amine]lanthanum, its substances and reaction conditions are shown in Table 2, and the others are the same as in Example 4.

Substance and reaction conditions in table 2 embodiment 15～21

Example 15 16 17 18 19 20 twenty one LaCl ₃ mmol 10 10 10 10 10 10 10 LiN(SiMe ₃ ) ₂ mmol 30 30 30 30 30 30 30 Ether mL 40 / / / / / / Ethylene glycol dimethyl ether mL / 30 / / / / / Tetrahydrofuran mL / / 20 / / 20 /

Example 15 16 17 18 19 20 twenty one Toluene mL / / / 30 / 20 10 n-Hexane mL / / / / 20 / 20 Ultrasonic time h 4 4 3 3 3 2 2 Ultrasonic field frequency KHz 25 40 70 100 400 500 600 output power W 10 50 150 200 800 1500 3000 white crystal g 5.110 5.189 5.562 5.091 5.103 5.444 5.612 Yield 82.4% 83.7% 89.7% 82.1% 82.3% 87.8% 90.5%

Claims (6)

1. the method for ultrasonic auxiliary synthetic three [N, two (trimethyl silicon based) amine of N-] lanthanum is characterized in that comprising the steps:

(1) under the protection of rare gas element, add 5～20mL anhydrous solvent by every gram anhydrous lanthanum chloride, apply ultrasonic field 1～4h;

(2) remove ultrasonic field after, add two (trimethyl silicon based) amido lithiums, the mol ratio of wherein two (trimethyl silicon based) amido lithiums and anhydrous lanthanum chloride is 3: 1, at room temperature stirs 10～60min;

(3) solvent of taking out in the solution with oil pump gets pale solid, and pale solid obtains purified three [N, two (trimethyl silicon based) amine of N-] lanthanum through distillation.

2. the method for ultrasonic auxiliary synthetic three [N, two (trimethyl silicon based) amine of N-] lanthanum is characterized in that comprising the steps:

(1) under the protection of rare gas element, anhydrous lanthanum chloride and two (trimethyl silicon based) amido lithium are added anhydrous solvent by its mol ratio at 1: 3, wherein every gram anhydrous lanthanum chloride adds 5～20mL anhydrous solvent, at room temperature stirs 5min then;

(2) apply ultrasonic field 1～4h, remove ultrasonic field, after solution gradually becomes clarification, take out with oil pump that solvent gets pale solid in the solution, obtain purified three [N, two (trimethyl silicon based) amine of N-] lanthanum through distillation.

3. the method for a kind of ultrasonic auxiliary synthetic three [N, two (trimethyl silicon based) amine of N-] according to claim 1 and 2 lanthanum, it is characterized in that: described rare gas element is nitrogen or argon gas.

4. a kind of ultrasonic auxiliary synthetic three [N according to claim 1 and 2, two (trimethyl silicon based) amine of N-] method of lanthanum, it is characterized in that: described anhydrous solvent is ether, glycol dimethyl ether, tetrahydrofuran (THF), toluene, normal hexane or the wherein any two kinds of above-mentioned solvents mixed solvent according to 0.1～0.9 mixed.

5. the method for a kind of ultrasonic auxiliary synthetic three [N, two (trimethyl silicon based) amine of N-] according to claim 1 and 2 lanthanum, it is characterized in that: described ultrasonic field range of frequency is 25～600KHz, output power range is 10～3000W.

6. the method for a kind of ultrasonic auxiliary synthetic three [N, two (trimethyl silicon based) amine of N-] according to claim 5 lanthanum, it is characterized in that: the optimized frequency scope of described ultrasonic field is 40～100KHz, the preferable range of output rating is 50～200W.