RU2547489C2 - Volatile ytterbium compounds and methods of obtaining thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: volatile ytterbium compounds represent tris-cyclopentadienyl compounds of the general formula {(R₁-C₅H₄)(R₂-C₅H₄)(R₃-C₅H₄)Yb}, where R₁, R₂, R₃ are alkyl radicals, C₅H₄ is a cyclopentadienyl ligand, Yb is ytterbium, with the alkyl radicals containing fluorine atoms as substituents and having the general formula R₁, R₂, R₃=CF₃(CH₂)_n, where n=2-3. The method of obtaining the ytterbium volatile compounds of the general formula {(R₁-C₅H₄)(R₂-C₅H₄)(R₃-C₅H₄)Yb} includes the interaction of a halide ytterbium compound with cyclopentadienyl compounds of alkali metals in a medium of an organic solvent. As the ytterbium halide compound used is an adduct of ytterbium chloride with an ether, and as the cyclopentadienyl compounds of the alkali metals used are fluorine-containing alkylcyclopentadienyls of the alkali metals of the general formula (R-C₅H₄)Me, where R=CF₃(CH₂)_n, where n=2-3, or their mixture, and Me is sodium or potassium.

EFFECT: increased volatility of the ytterbium compound and simple and efficient procedure of the product obtaining.

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Description

The invention relates to the field of chemistry of complex compounds of rare earth metals (REM), and in particular to new volatile compounds of ytterbium and a method for their synthesis. Volatile compounds of ytterbium can be used in technologies of chemical vapor deposition during coating, in the separation of complex mixtures of metals and the deep cleaning of ytterbium from impurities.

Volatile compounds of rare-earth metals, and ytterbium among them, are currently used for coating with special properties and in a number of other areas of technology [Y. Gun'koa; F. Edelmann. Organolanthanides in Materials Science. Comments on Inorganic Chemistry, v. 19, 1997, p. 153-184]. The property of volatility, that is, a relatively high vapor pressure (10-1000 Pa) at temperatures close to room temperature, is fundamentally important for the possibility of technical implementation of such processes. Most often, tris-cyclopentadienyl compounds of the general formula are used for these purposes: (R — C ₅ H ₄ ) ₃ M, where R is hydrogen (—H) or an alkyl group, for example methyl — CH ₃ , ethyl — C ₂ H _5, and t .d., M - ytterbium (or other REE).

Compounds of this class are the most volatile of all types of rare-earth metals and thermally stable [A.Togni, R. Halterman, Editor (s); Metallocenes: Synthesis, Reactivity, Applications, 1998, p. 55-110]. Tris-cyclopentadienyl ytterbium (C ₅ H ₅ ) ₃ Yb was first obtained in 1956 by the interaction of ytterbium chloride YbCl ₃ with sodium cyclopentadienyl C ₅ H ₅ Na [J. Birmingham, G. Wilkinson. J. Am. Chem. Soc., V. 78, 1956, p. 42]. It has a vapor pressure of 0.5 Pa at 100 ° C, which is not enough for most practically important processes. The vapor pressure of tris-methylcyclopentadienyl ytterbium (CH ₃ -C ₅ H ₅ ) ₃ Yb (~ 1.5 Pa at 100 ° C) is slightly higher [J. Weber et al., Appl. Phys. Lett., V. 53, 1988, p.2525]. Further progress in increasing the volatility of ytterbium compounds was achieved by switching to tris-isobutylcyclopentadienyl ytterbium (i-C ₄ H ₉ -C ₅ H ₅ ) ₃ Yb [EP 1659130 A1, 05.24.2006] and tris-isopropylcyclopentadienyl ytterbium (i-C ₃ H ₇ -C ₅ H ₅ ) ₃ Yb [US Patent 4882206, 10.21.1989]. The vapor pressure of the last of the substances of this type is ~ 100 Pa at 75 ° C. A common method for preparing these compounds is to heat an anhydrous metal halide, for example ytterbium chloride YbCl ₃ , with i-C ₃ H ₇ -C ₅ H ₄ -Na sodium isopropylcyclopentadienyl in tetrahydrofuran, followed by removal of the solvent in vacuo and sublimation of the product from the solid residue. The most modern developments in the field of production of highly volatile REM compounds are contained in US Patent Application No. 20100078601 of January 4, 2010. According to this application, the synthesis results in cyclopentadienyl REM compounds of the general formula:

{(R ₁ -C ₅ H ₄ ) (R ₂ -C ₅ H ₄ ) (R ₃ -C ₅ H ₄ ) M}, where M is an REM atom, C ₃ H ₄ is a cyclopentadienyl ligand with a substituent R, a R - hydrogen or an alkyl radical of the general formula C _n H _{2n + 1} , where C is carbon, H is hydrogen, n = 2-5, with R ₁ , R ₂ , R ₃ both identical and different groups. The synthesis of these compounds is carried out in an organic donor solvent (for example, tetrahydrofuran) by reaction of rare-earth chloride with the corresponding cyclopentadienyl derivative of an alkali metal.

This technical solution is the closest to the claimed and we have chosen as a prototype. The disadvantage of these compounds is the insufficient vapor pressure for the effective implementation of technological processes: at low vapor pressure, most processes proceed very slowly or become impossible. The disadvantage of the synthesis method is the use as a medium for the synthesis of a donor solvent (tetrahydrofuran), which forms a strong complex with the synthesis product, which complicates the isolation and purification of the product.

The problem, namely increasing the volatility of the ytterbium compound, is solved by the fact that tris-cyclopentadienyl ytterbium compounds of the general formula {(R ₁ -C ₅ H ₄ ) (R ₂ -C ₅ H ₄ ) (R ₃ - C ₅ H ₄ ) Yb}, where R ₁ , R ₂ , R ₃ are alkyl radicals, C ₅ H ₄ is a cyclopentadienyl ligand, Yb is ytterbium, characterized in that the alkyl radicals contain fluorine atoms and have the general formula R ₁ , R ₂ , R ₃ = CF ₃ (CH ₂ ) _n , where n = 2-3. Moreover, the alkyl radicals in the tris-cyclopentadienyl compounds of ytterbium compounds have identical composition and structure R ₁ = R ₂ = R ₃ or have different composition and structure R ₁ = R ₂ ≠ R ₃ . The essence of the proposed method for producing volatile ytterbium compounds is the use of ytterbium halide compounds with an alkali metal cyclopentadienyl compound instead of alkali metal alkylcyclopentadienyl, as in the known method, alkali metal fluoroalkylcyclopentadienyl of the general formula [CF ₃ (CH ₂ ) _n -C ₅ H ₄ ] Me where Me = Na, K, n = 2-3, or a mixture of these compounds. The synthesis is carried out in an aliphatic organic solvent, and the ytterbium chloride adduct with ether is used as a halogen compound of ytterbium: tetrahydrofuran - YbCl ₃ · 2THF, where THF is tetrahydrofuran C ₄ H ₈ O, or dimethoxyethane γbCl ₃ · 2DME, where DME dimethoxyethane CH ₃ OC ₂ H ₄ OCH ₃ .

The technical result of the invention is to increase the volatility of the ytterbium compound and simplify the procedure for isolating the product from the reaction mixture.

Case Studies

Example 1. Synthesis of tris- (3,3,3-trifluoropropylcyclopentadienyl) ytterbium, {(R ₁ -C ₅ H ₄ ) (R ₂ -C ₅ H ₄ ) (R ₃ -C ₅ H ₄ ) Yb}, where R ₁ , R ₂ , R ₃ = CF ₃ (CH ₂ ) ₂ .

1a. Synthesis of 3,3,3-trifluoropropylcyclopentadiene. To a suspension of 35 g of cyclopentadienyl sodium in 100 ml of pentane, a solution of 67 g of 1,1,1-trifluoro-3-bromopropane in 130 ml of pentane at -40 ° C is added with stirring. The mixture is stirred by heating (to room temperature) for 3 hours. The product and solvent are distilled off at 0 ° C in vacuo. The residue is extracted with 100 ml of pentane. The combined fractions are distilled at -30 ° C and 20 mm Hg. 51.5 g of product are obtained in the form of a colorless oil (yield -80%);

1b. Synthesis of 3,3,3-trifluoropropylcyclopentadienyl potassium. A solution of 51.5 g of 3,3,3-trifluoropropylcyclopentadiene in 150 ml of pentane is pinned to a suspension of 14 g of potassium in 250 ml of pentane at -60 ° C. The mixture was stirred for 4 hours at -30 ° C, after which it was warmed to room temperature and stirred for another 4 hours. The solvent and excess trifluoropropylcyclopentadiene were removed in vacuo, the residue was dried in vacuo for 2 hours at room temperature.

1c. A suspension of 42.5 g of the adduct of ytterbium trichloride with tetrahydrofuran YbCl ₃ · 2C ₄ H ₈ O in 300 ml of pentane is prepared. At a temperature of -60 ° C, potassium trifluoropropylcyclopentadienyl is combined. The resulting mixture was stirred for 4 hours at -30 ° C, and then 12 hours at room temperature. A change in color of the solution from red to emerald green is observed. At the end of the process, the precipitate of potassium chloride is separated by filtration, the solution is evaporated in vacuo and a blue-green oil is obtained in the residue. Distill the oil in vacuo at a pressure of ~ 10 Pa at room temperature. The product is collected in a dry ice-cooled receiver. 43 g (~ 65%) of tris- (3,3,3-trifluoropropylcyclopentadienyl) ytterbium (CF ₃ CH ₂ CH ₂ -C ₅ H ₄ ) ₃ Yb are obtained. Melting point ~ 0 ° C.

The vapor pressure is measured by the static method in the range of 20-90 ° C. The data obtained in coordinates coordinates pressure (mmHg) - temperature (° C) are presented in figure 1. From the presented experimental data it follows that the vapor pressure of tris- (3,3,3-trifluoropropylcyclopentadienyl) ytterbium at a temperature of 75 ° C is about 4000 Pa (~ 30 mm Hg), which is about 40 times higher than the vapor pressure of the volatile compounds of ytterbium according to the prototype.

Example 2. Synthesis of bis- (4,4,4-trifluorobutylcyclopentadienyl) (3,3,3-trifluoropropylcyclopentadienyl) ytterbium, {(R ₁ -C ₅ H ₄ ) (R ₂ -C ₅ H ₄ ) (R ₃ -C ₅ H ₄ ) Yb}, where R ₁ , R ₂ = CF ₃ (CH ₂ ) ₃ ; R ₃ = CF ₃ (CH ₂ ) ₂ .

2a. The synthesis of potassium 4,4,4-trifluorobutylcyclopentadienyl is carried out analogously to the procedure described in example 1, starting from 29 g (~ 0.15 mol) of 1,1,1-trifluoro-4-bromobutane. 26.5 substances are obtained (yield ~ 80%).

2b. The synthesis of potassium 3,3,3-trifluoropropylcyclopentadienyl is carried out using 13.5 g of 1,1,1-trifluoro-3-bromopropane (~ 0.076 mol) as the starting compound. The synthesis is carried out under the conditions described above in example 1. Receive 12.4 g of 3,3,3-trifluoropropylcyclopentadienyl potassium (yield ~ 80%).

2c. A suspension of 28.5 g (0.062 mol) of ytterbium trichloride adduct with tetrahydrofuran YbCl ₃ · 2C ₄ H ₁₀ O ₂ in 300 ml of pentane is prepared. At a temperature of -60 ° C, 26.5 g of 4,4,4-trifluorobutylcyclopentadienyl potassium and 12.4 g of 3,3,3-trifluoropropylcyclopentadienyl potassium in 200 ml of pentane are combined with a mixture. The resulting mixture was stirred for 4 hours at -30 ° C, and then 12 hours at room temperature. A change in color of the solution is observed. At the end of the process, the precipitate of potassium chloride is separated by filtration, the solution is evaporated in vacuo and a greenish-blue oil is obtained in the residue. Distill the oil in vacuo at a pressure of ~ 1 Pa at room temperature. The product is collected in a dry ice-cooled receiver. 36 g (~ 85%) of bis- (4,4,4-trifluorobutylcyclopentadienyl) (3,3,3-trifluoropropylcyclopentadienyl) ytterbium are obtained, {(CF ₃ CH ₂ CH ₂ CH ₂ -C ₅ H ₄ ) ₂ (CF ₃ CH ₂ CH ₂ -C ₅ H ₄ ) Yb}. Melting point ~ 0 ° C. The vapor pressure is measured by the effusion method at 70 ° C. Received 350 ± 50 PA, which is approximately 3.5 times higher than the vapor pressure of the volatile compounds of ytterbium according to the prototype.

Example 3. Synthesis of tris- (4,4,4-trifluorobutylcyclopentadienyl) ytterbium, {(R ₁ -C ₅ H ₄ ) (R ₂ -C ₅ H ₄ ) (R ₃ -C ₅ H ₄ ) Yb}, where R ₁ , R ₂ , R ₃ = CF ₃ (CH ₂ ) ₃ .

3a. Synthesis of 4,4,4-trifluorobutylcyclopentadiene. To a suspension of 28 g of cyclopentadienyl sodium in 150 ml of hexane, a solution of 60 g of 1,1,1-trifluoro-4-bromobutane in 200 ml of hexane at -40 ° C is added with stirring. The mixture is stirred by heating (to room temperature) for 3 hours. The product and solvent are distilled off at 0 ° C in vacuo. The residue is extracted with 100 ml of hexane. The combined fractions are distilled at 30 ° C and 20 mm Hg. Obtain 55 g of the product as a colorless oil (yield ~ 80%);

3b. Synthesis of 4,4,4-trifluorobutylcyclopentadienyl potassium. To a suspension of 23 g of potassium in 250 ml of hexane at -60 ° C, a solution of 84 g of 4,4,4-trifluorobutylcyclopentadiene in 150 ml of hexane is added dropwise. The mixture was stirred for 4 hours at -30 ° C, after which it was warmed to room temperature and stirred for another 4 hours. The solvent and excess trifluorobutylcyclopentadiene were removed in vacuo, the residue was dried in vacuo for 2 hours at room temperature.

3c. The ytterbium chloride adduct with YbCl ₃ · 2 (C ₂ H ₅ ) ₂ O diethyl ether is obtained by boiling anhydrous 30 g of YbCl ₃ in 150 ml of diethyl ether for 8 hours, followed by removal of excess diethyl ether in vacuum and drying at room temperature in vacuum (5 · 10 ^-2 mm Hg) for 2 hours. From the obtained 46 g of the adduct of ytterbium trichloride with diethyl ether YbCl ₃ · 2 (C ₂ H ₅ ) ₂ O, a suspension is prepared in 200 ml of hexane. Potassium 4,4,4-trifluorobutylcyclopentadienyl is added to the suspension with vigorous stirring. The mixture is stirred at a temperature of -40 ° C for 4 hours, then 12 hours at room temperature. At the end of the process, the precipitate of potassium chloride was separated by filtration, the solution was evaporated in vacuo to give an oil residue. Distill the oil in vacuo at a pressure of ~ 10 Pa at room temperature. The product is collected in a dry ice-cooled receiver. 75 g (~ 75%) of tris- {4,4,4-trifluorobutylcyclopentadienyl) ytterbium (CF ₃ CH ₂ CH ₂ C ₅ H ₄ ) ₃ Yb are obtained. Melting point ~ + 10 ° C.

The vapor pressure is measured by the static method at a temperature of 75 ° C. The resulting value is 150 Pa. From the presented experimental data, it follows that the vapor pressure of tris- (4,4,4-trifluorobutylcyclopentadienyl) ytterbium at a temperature of 75 ° C is about 300 Pa (~ 2.5 mm Hg), which is about 2 times higher than the vapor pressure volatile compound ytterbium prototype.

Example 4. Synthesis of bis- (4,4,4-trifluorobutylcyclopentadienyl) (3,3,3-trifluoropropylcyclopentadienyl) ytterbium, {(R ₁ -C ₅ H ₄ ) (R ₂ -C ₅ H ₄ ) (R ₃ -C ₅ H ₄ ) Yb}, where R ₁ , R ₂ = CF ₃ (CH ₂ ) ₃ ; R ₃ = CF ₃ (CH ₂ ) ₂ .

4a. The synthesis of potassium 4,4,4-trifluorobutylcyclopentadienyl is carried out analogously to the procedure described in example 1, starting from 37 g (~ 0.20 mol) of 1,1,1-trifluoro-4-bromobutane and 8 g of potassium in 200 ml of hexane. 41 g of substance are obtained.

4b. The synthesis of potassium 3,3,3-trifluoropropylcyclopentadienyl is carried out using 17.5 g of 1,1,1-trifluoro-3-bromopropane (~ 0.098 mol) and 4 g of potassium in 150 ml of hexane as the starting compound. The synthesis is carried out under the conditions described above in example 1. Receive 20 g of 3,3,3-trifluoropropylcyclopentadienyl potassium.

4c. The ytterbium chloride adduct with diethylene glycol dimethyl ether is obtained by boiling anhydrous 27 g of YbCl ₃ in 250 ml of diethylene glycol dimethyl ether for 8 hours, followed by removal of excess diethylene glycol dimethyl ether in vacuum and drying at room temperature in vacuum (5 · 10 ^-2 mm RT .st.) within 2 hours. A suspension of 200 ml of hexane is prepared from the obtained 53.5 g of an adduct of ytterbium trichloride with diethylene glycol dimethyl ether. 41 g of 4,4,4-trifluorobutylcyclopentadienyl potassium in 200 ml of hexane and 20 g of 3,3,3-trifluoropropylcyclopentadienyl potassium in 200 ml of hexane are added to the suspension with vigorous stirring. The resulting mixture was stirred for 4 hours at -30 ° C, and then 12 hours at room temperature. At the end of the process, the precipitate of potassium chloride is separated by filtration, the solution is evaporated in vacuo, the residue is oil. The distillation of the oil is carried out in vacuum at a pressure of ~ 1 Pa at room temperature. The product is collected in a dry ice-cooled receiver. Obtain 66 g of bis- (4,4,4-trifluorobutylcyclopentadienyl) (3,3,3-trifluoropropylcyclopentadienyl) ytterbium, {(CF ₃ CH ₂ CH ₂ CH ₂ -C ₅ H ₄ ) ₂ (CF ₃ CH ₂ CH ₂ - C ₅ H ₄ ) Yb}. Melting point ~ 0 ° C. Received 400 PA, which is approximately 3.5 times higher than the vapor pressure of the volatile compounds of ytterbium according to the prototype.

The volatile compounds of ytterbium according to this invention have advantages in comparison with the technical solution of the prototype: they have up to 40 times higher vapor pressure (4000 Pa at a temperature of 75 ° C instead of 100 Pa at the same temperature according to the prototype). The method for the synthesis of volatile compounds of ytterbium according to the invention in comparison with the prototype provides the production of more volatile compounds and allows to obtain the product according to a simpler procedure: the synthesis product can be isolated from the reaction mixture by distillation in vacuum, in contrast to the method according to the prototype, which includes the stage of additional purification of the product from donor solvent.

Thus, the volatile compounds of ytterbium according to this invention have a higher vapor pressure than in the known technical solutions, and can be obtained with less labor. An additional useful characteristic of the compounds according to this invention is their low melting point - about 0 ° C. Therefore, this invention can be successfully applied in practice to obtain volatile compounds of ytterbium in the processes of chemical deposition from gas and in the separation of complex mixtures of metals by gas-phase methods.

Claims (4)

1. Volatile tris-cyclopentadienyl compounds of ytterbium of the general formula {(R ₁ -C ₅ H ₄ ) (R ₂ -C ₅ H ₄ ) (R ₃ -C ₅ H ₄ ) Yb}, where R ₁ , R ₂ , R ₃ - alkyl radicals, C ₅ H ₄ - cyclopentadienyl ligand, Yb - ytterbium, characterized in that the alkyl radicals contain fluorine atoms as substituents and have the general formula R ₁ , R ₂ , R ₃ = CF ₃ (CH ₂ ) _n , where n = 2-3. 2. Volatile tris-cyclopentadienyl compounds of ytterbium according to claim 1, characterized in that the alkyl radicals in the composition of the compound have the same composition and structure R ₁ = R ₂ = R ₃ or have different composition and structure R ₁ = R ₂ ≠ R ₃ . 3. A method for producing volatile ytterbium compounds of the general formula {(R ₁ -C ₅ H ₄ ) (R ₂ -C ₅ H ₄ ) (R ₃ -C ₅ H ₄ ) Yb}, comprising reacting a ytterbium halide compound with alkali metal cyclopentadienyl compounds in an organic solvent medium, characterized in that ytterbium chloride adduct with ether is used as the ytterbium halide compound, and alkali metal fluorine-containing alkyl cyclopentadienyls of the general formula (RC ₅ H ₄ ) Me are used as cyclopentadienyl compounds of the alkali metals, where R = CF ₃ ( CH ₂ ) _n , where n = 2-3, silt and a mixture thereof, a Me is sodium or potassium. 4. The method for producing volatile ytterbium compounds according to claim 3, characterized in that tetrahydrofuran or dimethoxyethane is used as the ether in the adduct with ytterbium chloride, and the synthesis is carried out in an aliphatic organic solvent.

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