A convenient synthesis of rare earth metal precursors

Abstract

The application discloses a convenient synthesis method of a rare earth metal precursor and belongs to the technical field of precursor synthesis. The application mixes reaction of orthoester, amine and acetic acid, and then adds alkali to obtain amidine ligand; the rare earth metal halide, Brønsted base, cyclopentadiene and amidine ligand are reacted, and after the reaction is completed, the solvent is removed through filtration, and then distillation purification is carried out to obtain a yttrium precursor. The application can obtain the target product by connecting the generation of tricyclopentadienyl yttrium intermediate and ligand exchange of amidine compounds. The application has the advantages of convenient process, excellent yield and the like.

Description

Technical Field

[0001] This invention relates to the field of precursor synthesis technology, and more specifically to a convenient method for synthesizing rare earth metal precursors. Background Technology

[0002] Rare earth oxides (REOs) have long been considered a class of highly promising materials. They can be applied in numerous fields in the form of powders, nanoparticles, or thin films. In particular, yttrium oxide (Y₂O₃) and its rare earth (RE) doped systems (such as Ce) are particularly promising. 3+ Y₂O₃ or Nd 3+ Yttrium oxide (Y₂O₃), with its wide bandgap (5.5 eV) and high refractive index (≈2.0), shows excellent potential in optical fields such as lasers, planar waveguides, and antireflective coatings. Furthermore, yttrium oxide possesses a high relative permittivity (ε₀). With a thermal conductivity of approximately 17-20 kJ, it is suitable as a high-k dielectric material in complementary metal-oxide-semiconductor (CMOS) devices. Thanks to their excellent thermal stability and low thermal conductivity, yttrium-stabilized zirconia (YSZ) and layered yttrium oxide ceramics can be used as high-performance thermal barrier coatings (TBCs) for turbine blades. Furthermore, these materials exhibit good chemical stability in harsh environments, thus effectively serving as corrosion protection layers.

[0003] Previously, researchers have employed various vapor deposition techniques to prepare Y₂O₃, RE:Y₂O₃, and YSZ thin films, including physical methods such as molecular beam epitaxy (MBE), sputtering, and pulsed laser deposition (PLD). In addition, chemical vapor deposition (CVD), especially atomic layer deposition (ALD), has received increasing attention in recent years. ALD technology offers particularly significant advantages: its process is self-limiting, enabling the deposition of large-area, three-dimensional coatings with excellent uniformity, precise thickness control, and good shape retention. These characteristics have led to the application of ALD processes in multiple technological fields.

[0004] Atomic layer deposition (ALD) processes are significantly influenced by the physicochemical properties of the precursors used. One key characteristic is the precursor's reactivity, necessitating the selection of suitable ligands that meet the requirements of the ALD process. Besides reactivity and volatility, an "ideal" ALD precursor should also possess good thermal stability. This characteristic is crucial to prevent any chemical vapor deposition (CVD)-type growth contribution during film growth. In this context, chelating ligands exhibit greater application potential because they can achieve coordination saturation for the large ionic radii of rare-earth metal centers. Furthermore, the volatility and reactivity of the precursor can be tuned by selecting and combining different ligands; and changes in ligand steric hindrance can further fine-tune its physicochemical properties. Both strategies directly affect the intermolecular and intramolecular interactions in the final precursor. To make potential precursors more suitable for the ALD process, their synthesis should be easily scalable, and the purification process should be simple and efficient. Although meeting all of the above requirements is quite challenging, targeted exploratory studies of organometallic compounds can still lay the foundation for finding ALD precursors that can meet most of the requirements and have better performance.

[0005] To date, the vast majority of known yttrium or lanthanide metal precursor compounds are solids with low vapor pressures. In the mass production process of semiconductor devices, these precursors are not suitable as film-forming precursors if yttrium or lanthanide metal oxide films are prepared by chemical vapor deposition (CVD) or atomic layer deposition (ALD).

[0006] In order to prepare rare-earth metal-based thin films for next-generation semiconductor devices using atomic layer deposition, there is an urgent need in the field for a novel precursor compound with a viscosity lower than that of known rare-earth metal precursor compounds or a vapor pressure higher than that of known rare-earth metal precursor compounds. Summary of the Invention

[0007] In view of this, the present invention provides a convenient method for synthesizing rare earth metal precursors with low viscosity or high vapor pressure.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A convenient method for synthesizing rare earth metal precursors, wherein the rare earth metal precursors have the structure shown in Formula 1:

[0010] General Formula 1 Among them, R 1 ~R 3 M is independently selected from the same or different alkyl substituents having 0 to 5 carbon atoms; 2 It is any one of the rare earth metals yttrium, scandium, or lanthanum.

[0011] The rare earth metal precursor is liquid at room temperature.

[0012] The convenient synthetic route for the rare earth metal precursor is as follows:

[0013] Among them, M 1 It can be any one of sodium, calcium, potassium, lithium, or magnesium; M 2 It is any one of the rare earth metals yttrium, scandium, or lanthanum; R is independently selected from the same or different alkyl substituents having 0 to 5 carbon atoms.

[0014] The convenient method for synthesizing the rare earth metal precursor includes the following steps: (1) Mix the orthoester, amine and acetic acid, then heat to react. After the reaction is complete, add alkali and stir. Then distill to purify and obtain amidine ligand; (2) Disperse rare earth metal halides in an organic solvent to obtain a rare earth metal halide dispersion for later use; disperse Brønsted base in an organic solvent, add cyclopentadiene dropwise to react, and after the reaction is complete, add the rare earth metal halide dispersion and heat under reflux to react. After the reaction is complete, cool to room temperature. (3) Add amidine ligand to the reaction solution obtained in step (2), heat and reflux the reaction. After the reaction is completed, filter to remove the solvent, and then distill to purify and obtain rare earth metal precursor.

[0015] Furthermore, the molar ratio of orthoic acid triester, amine, acetic acid and base in step (1) is (1~5):(1~5):(1~5):(1~5).

[0016] Furthermore, the amine mentioned in step (1) is ethylamine or isopropylamine; The alkali is any one of sodium hydroxide, calcium hydroxide, potassium hydroxide, lithium hydroxide, and magnesium hydroxide.

[0017] Furthermore, the heating reaction temperature in step (1) is 130-170℃, and the heating reaction time is 1-48h; The stirring rate is 50-2000 rpm, and the stirring time is 10 hours.

[0018] Furthermore, the molar ratio of the cyclopentadiene, Brønsted base, rare earth metal halide, and amidine ligand is (1~5):(1~5):(1~5):(1~5).

[0019] Furthermore, the Brønsted base is any one of potassium hydroxide, sodium hydroxide, sodium ethoxide, potassium ethoxide, lithium ethoxide, sodium methoxide, potassium methoxide, lithium methoxide, potassium tert-butoxide, sodium amino, lithium amino, and potassium amino. The halogen in the rare earth metal halide is any one of Cl, Br and I.

[0020] Further, the organic solvent mentioned in step (2) is any one or a mixture of dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, methanol, ethanol, tert-butanol, tetrahydrofuran, toluene, xylene, n-heptane, n-pentane, and n-hexane.

[0021] Furthermore, the drop acceleration rate in step (2) is 1-1000 drops / min.

[0022] After adding cyclopentadiene, the reaction was carried out at room temperature for 1-48 hours. The heating reflux reaction temperature is 50-200℃, and the reaction time is 1-48h.

[0023] Furthermore, in step (3), the reflux reaction temperature is 50-200℃ and the reaction time is 8-12h.

[0024] The beneficial effects of this invention are as follows: Traditional synthesis processes require the initial synthesis of a chlorodicyclopentadiene rare earth metal compound, followed by reaction with an amidine salt containing alkali-dehydrogenated compounds to generate the corresponding precursor. This process is cumbersome, and the multiple steps result in low yields. This invention, however, directly yields the target product by generating a ternary cyclopentadiene rare earth metal complex intermediate in series, followed by ligand exchange with an amidine compound. This invention offers a convenient process and excellent yields. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1 A convenient method for synthesizing yttrium precursors, the structural formula of which is:

[0027] The synthesis method is as follows: (1) Mix 50 g of orthoester, 36 g of isopropylamine and 18.5 g of acetic acid, then heat at 170 °C for 16 h. After the reaction is complete, add 18.5 g of sodium hydroxide and stir for 10 h. Then distill to purify and obtain amidine ligand. (2) Disperse 40 g of yttrium trichloride in 500 mL of n-hexane to obtain a yttrium dispersion for later use; disperse 24 g of sodium hydroxide in 500 mL of tetrahydrofuran, add 40 g of cyclopentadiene dropwise, and react at room temperature for 12 h after the addition is complete. After the reaction is complete, add the yttrium dispersion, heat to 50 °C and reflux for 12 h, and cool to room temperature after the reaction is complete. (3) Add 29 g of amidine ligand to the reaction solution obtained in step (2), heat and reflux at 60°C for 12 h. After the reaction is completed, filter to remove the solvent, and then distill to purify and obtain 69 g of pale yellow liquid yttrium precursor with a yield of 94%. 1 H NMR (400MHz, C6D6): d [ppm] = 6.20 (s, 10H), 3.25 (m, 3H), 1.44 (s, 2H), 0.93 (d, 12H).

[0028] Example 2 A convenient method for synthesizing yttrium precursors, the structural formula of which is:

[0029] The synthesis method is as follows: (1) Mix 50 g of orthocyanin, 44 g of isopropylamine and 22.4 g of acetic acid, and then heat at 150 °C for 16 h. After the reaction is complete, add 32 g of sodium hydroxide and stir for 10 h. Then, distill and purify to obtain amidine ligand. (2) Disperse 36 g of yttrium trichloride in 500 mL of n-hexane to obtain a yttrium dispersion for later use; disperse 24 g of sodium hydroxide in 500 mL of tetrahydrofuran, add 57 g of ethylcyclopentadiene dropwise, and react at room temperature for 12 h after the addition is complete. After the reaction is complete, add the yttrium dispersion and heat to reflux at 70 °C for 12 h. After the reaction is complete, cool to room temperature. (3) Add 29 g of amidine ligand to the reaction solution obtained in step (2), heat and reflux at 50°C for 12 h. After the reaction is completed, filter to remove the solvent, and then distill to purify and obtain 80 g of pale yellow liquid yttrium precursor with a yield of 91%. 1 H NMR (400MHz, C6D6): d [ppm] = 6.07(d, 8H), 3.34(m, 2H), 2.55(q, 2H), 1.24(t, 6H), 0.99(d, 12H), 0.90(t, 3H).

[0030] Example 3 A convenient method for synthesizing yttrium precursors, the structural formula of which is:

[0031] The synthesis method is as follows: (1) Mix 50 g of orthocyanin, 23.7 g of ethylamine and 15.8 g of acetic acid, and then heat at 150 °C for 8 h. After the reaction is complete, add 15.8 g of sodium hydroxide and stir for 10 h. Then, distill to purify and obtain amidine ligand. (2) Disperse 40.7 g of yttrium trichloride in 500 mL of n-hexane to obtain a yttrium dispersion for later use; disperse 40.0 g of sodium tert-butoxide in 500 mL of tetrahydrofuran, add 39.2 g of ethylcyclopentadiene dropwise, and react at room temperature for 12 h after the addition is complete. After the reaction is complete, add the yttrium dispersion, heat to 60 °C and reflux for 12 h, and cool to room temperature after the reaction is complete. (3) Add 26.7 g of amidine ligand to the reaction solution obtained in step (2), heat and reflux at 60 °C for 12 h. After the reaction is completed, filter to remove the solvent, and then distill to purify and obtain 91 g of pale yellow liquid yttrium precursor with a yield of 91%. 1 H NMR (400MHz, C6D6): d [ppm] = 0.83(t, 3H), 0.99(t, 6H), 1.20(t, 6H), 1.36(q, 2H), 1.98(q, 2H), 2.50(q, 4H), 3.00(q, 4H), 6.0(dt, 8H).

[0032] Example 4 A convenient method for synthesizing yttrium precursors, the structural formula of which is:

[0033] The synthesis method is as follows: (1) Mix 50 g of orthocyanin, 25.8 g of ethylamine and 17 g of acetic acid, then heat at 130 °C for 10 h. After the reaction is complete, add 17 g of sodium hydroxide and stir for 10 h. Then distill to purify and obtain amidine ligand. (2) 43.86 g of yttrium trichloride was dispersed in 500 mL of n-hexane to obtain a yttrium dispersion for later use; 50.4 g of potassium tert-butoxide was dispersed in 500 mL of tetrahydrofuran, and 48.6 g of isopropylcyclopentadiene was added dropwise. After the addition was complete, the reaction was carried out at room temperature for 12 h. After the reaction was completed, the yttrium dispersion was added, and the mixture was heated to reflux at 70 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature. (3) Add 28.8 g of amidine ligand to the reaction solution obtained in step (2), heat and reflux at 50°C for 12 h. After the reaction is completed, filter to remove the solvent, and then distill to purify and obtain 90.9 g of pale yellow liquid yttrium precursor, with a yield of 94%. 1H NMR (400MHz, C6D6): d [ppm] = 0.85(t, 3H), 1.02(t, 6H), 1.24(d, 12H), 1.94(q, 2H), 2.82(m, 2H), 3.01(q, 4H), 6.01(dt, 8H).

[0034] Example 5 A convenient method for synthesizing yttrium precursors, the structural formula of which is:

[0035] The synthesis method is as follows: (1) Mix 50 g of orthocyanin, 25.8 g of ethylamine and 17 g of acetic acid, then heat at 130 °C for 10 h. After the reaction is complete, add 17 g of sodium hydroxide and stir for 10 h. Then distill to purify and obtain amidine ligand. (2) 43.86 g of yttrium trichloride was dispersed in 500 mL of n-hexane to obtain a yttrium dispersion for later use; 50.4 g of potassium tert-butoxide was dispersed in 500 mL of tetrahydrofuran, and 29.7 g of cyclopentadiene was added dropwise. After the addition was complete, the reaction was carried out at room temperature for 12 h. After the reaction was completed, the yttrium dispersion was added, and the mixture was heated to reflux at 70 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature. (3) Add 28.8 g of amidine ligand to the reaction solution obtained in step (2), heat and reflux at 50°C for 12 h. After the reaction is completed, filter to remove the solvent, and then distill to purify and obtain 89.9 g of pale yellow liquid yttrium precursor, with a yield of 93%. 1 H NMR (400MHz, C6D6): d [ppm] = 0.81(t, 3H), 0.96(t, 6H), 1.90(q, 2H), 2.96(q, 4H), 6.16(s, 8H).

[0036] Example 6 A convenient method for synthesizing scandium precursors, the structural formula of which is:

[0037] The synthesis method is as follows: (1) Mix 60 g of trimethyl orthobutyrate, 28.4 g of ethylamine and 18.9 g of acetic acid, and then heat at 150 °C for 16 h. After the reaction is complete, add 18.9 g of sodium hydroxide and stir for 10 h. Then, distill and purify to obtain amidine ligand. (2) Disperse 36.0 g scandium trichloride in 500 mL n-hexane to obtain yttrium dispersion for later use; disperse 14.4 g sodium amino in 500 mL tetrahydrofuran, add 34.7 g ethylcyclopentadiene dropwise, react at room temperature for 12 h after the addition is complete, add yttrium dispersion after the reaction is complete, heat to reflux at 70 ℃ for 12 h, and cool to room temperature after the reaction is complete; (3) Add 26.2 g of amidine ligand to the reaction solution obtained in step (2), heat and reflux at 60°C for 12 h. After the reaction is completed, filter to remove the solvent, and then distill to purify and obtain 61.7 g of pale yellow liquid scandium precursor with a yield of 90%. 1 H NMR (400MHz, C6D6): d [ppm] = 0.22(t,3H), 1.00(t, 6H), 1.19(t, 6H), 1.33(q, 2H), 1.92(q,2H), 2.38(q, 4H), 3.03(q, 4H), 6.0(dt, 8H).

[0038] Example 7 A convenient method for synthesizing lanthanum precursors, the structural formula of which is:

[0039] The synthesis method is as follows: (1) Mix 60 g of triethyl orthoacetate, 43.7 g of isopropylamine and 22.2 g of acetic acid, then heat at 150 °C for 6 h. After the reaction is complete, add 22.2 g of sodium hydroxide and stir for 10 h. Then distill to purify and obtain amidine ligand. (2) 66.2 g of lanthanum trichloride was dispersed in 500 mL of n-hexane to obtain yttrium dispersion for later use; 24 g of sodium hydroxide was dispersed in 500 mL of tetrahydrofuran, and 40 g of cyclopentadiene was added dropwise. After the addition was complete, the reaction was carried out at room temperature for 12 h. After the reaction was completed, the yttrium dispersion was added, and the mixture was heated to reflux at 70 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature. (3) Add 30.8 g of amidine ligand to the reaction solution obtained in step (2), heat and reflux at 80°C for 12 h. After the reaction is completed, filter to remove the solvent, and then distill to purify and obtain 108.8 g of pale yellow liquid lanthanum precursor with a yield of 92%. 1 H NMR (400 MHz, C6D6): d [ppm] = 0.89(d, 12H), 1.19(t, 6H), 1.48(s, 3H), 2.53(m, 4H), 3.15(s, 2H), 6.06 (s, 3H), 6.18(s, 3H).

[0040] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A convenient method for synthesizing rare earth metal precursors, characterized in that, The rare earth metal precursor has the structure shown in Formula 1: General Formula 1 Among them, R 1 ~R 3 M is independently selected from the same or different alkyl substituents having 0 to 5 carbon atoms; 2 It is any one of the rare earth metals yttrium, scandium, or lanthanum; The convenient method for synthesizing the rare earth metal precursor includes the following steps: (1) Mix the orthoester, amine and acetic acid, then heat to react. After the reaction is complete, add alkali and stir. Then distill to purify and obtain amidine ligand; (2) Disperse rare earth metal halides in an organic solvent to obtain a rare earth metal halide dispersion for later use; disperse Brønsted base in an organic solvent, add cyclopentadiene dropwise to react, and after the reaction is complete, add the rare earth metal halide dispersion and heat under reflux to react. After the reaction is complete, cool to room temperature. (3) Add amidine ligand to the reaction solution obtained in step (2), heat and reflux the reaction. After the reaction is completed, filter to remove the solvent, and then distill to purify and obtain rare earth metal precursor.

2. The convenient synthesis method for rare earth metal precursors according to claim 1, characterized in that, The molar ratio of orthoic acid triester, amine, acetic acid and base in step (1) is (1~5):(1~5):(1~5):(1~5).

3. A convenient method for synthesizing a rare earth metal precursor according to claim 1 or 2, characterized in that, The amine mentioned in step (1) is ethylamine or isopropylamine; The alkali is any one of sodium hydroxide, calcium hydroxide, potassium hydroxide, lithium hydroxide, and magnesium hydroxide.

4. The convenient synthesis method for rare earth metal precursors according to claim 1, characterized in that, The heating reaction temperature in step (1) is 130-170℃, and the heating reaction time is 1-48h; The stirring rate is 50-2000 rpm, and the stirring time is 1-48 h.

5. The convenient synthesis method for rare earth metal precursors according to claim 1, characterized in that, The molar ratio of the cyclopentadiene, Brønsted base, rare earth metal halide, and amidine ligand is (1~5):(1~5):(1~5):(1~5).

6. The convenient synthesis method for rare earth metal precursors according to claim 5, characterized in that, The Brønsted base is any one of potassium hydroxide, sodium hydroxide, sodium ethoxide, potassium ethoxide, lithium ethoxide, sodium methoxide, potassium methoxide, lithium methoxide, potassium tert-butoxide, sodium amino, lithium amino, and potassium amino. The halogen in the yttrium halide is any one of Cl, Br, and I.

7. The convenient synthesis method for rare earth metal precursors according to claim 1, characterized in that, The organic solvent mentioned in step (2) is any one or a mixture of dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, methanol, ethanol, tert-butanol, tetrahydrofuran, toluene, xylene, n-heptane, n-pentane, and n-hexane.

8. The convenient synthesis method for rare earth metal precursors according to claim 1, characterized in that, The drop acceleration rate mentioned in step (2) is 1-1000 drops / min; After adding cyclopentadiene, the reaction was carried out at room temperature for 1-48 hours. The heating reflux reaction temperature is 50-200℃, and the reaction time is 1-48h.

9. The convenient synthesis method for rare earth metal precursors according to claim 1, characterized in that, In step (3), the heating reflux reaction temperature is 50-200℃ and the reaction time is 1-48h.

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