SU1043105A1 - Method for preparing aluminohydrides of alkaly-earth metals - Google Patents

Abstract

A method for producing alkaline-earth metal aluminohydrates by reacting binary hydrides of gshyumin and alkaline-earth metal in an organic solvent, so that. With the purpose of increasing the purity of the product, the interaction of the starting products is carried out in diethyl ether. lithium and stirring, the clarified solution is poured in. aromatic. the solvent in a volume ratio, respectively, at 80, the precipitate obtained is passed through with ether and dried. ...

Description

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This invention relates to a method. alkaline earth metal aluminum hydrides, used as reducing agents for organic functional groups and as effective sources of hydrogen. A known method, fl, for the preparation of alkaline earth metal aluminum hydrides by the interaction of sodium aluminum hydride with chlorides of the corresponding metals. Solvating tetrahydrofuran (THF) through the reaction of 2KaL1H4 M (A1H4) 2 PTHF + 2N.aCl solution However, this way to produce aluminum hydroxide metal is not possible due to the strength of THF with aluminohydride. Moreover, the final alkaline product is alkaline. contains - with NaAlHif mixtures; The closest to the technical essence and the achieved result of the invention is method 2 of obtaining alkaline earth metal aluminum hydrides by the interaction of alkaline earth metal hydride and aluminum hydride solution in GF reaction. THF. 2A1E + MHj (A1H4) -n THF, solution However, it is not possible to obtain pure aluminum-alkali metal hydrides in a known manner. Ca (AlH4) 2 preparations were obtained with a total content of 94% of the main substance. SrCAlH Jj could not be obtained due to the ease of its decomposition with the transformation into Sr (AlH4) 2-1 / 3Sr (A1Hb) 2 + 4/3 A1 + 2H 2 into hexahydryloaluminate. Ba (A1H4) -PTGP in a mixture with BaNg is also obtained by the interaction of BaHj and AlHj in THF, but in the sediment due to its insolubility in THF, the difficulty of synthesizing pure aluminum hydrides of alkaline earth metals and their relatively little knowledge is due to the fact that for Ca (A1H ) 2I, Sr (A1H) 2, only strongly solvated by solvents are known: THF and Diglyme. For Ba (A1H4), solvents are not known at all. The aim of the invention is to increase the purity of the products. The goal is achieved by the fact that the action of binary aluminum and alkaline earth metal hydrides is carried out in diethyl ether by adding complex lithium hydride and stirring, the clarified solution is poured into an aromatic solvent in a volume ratio of l-3f5, respectively, at 80-100 ° C, the precipitate obtained is washed with ether and dried. The process is reflected by the equations MH2 4 2A1H + 2YEH4 M (A1H4) 2, solution M (AHH4) 2 M (A1H4) 2 2YEH 4 4YEH4. toluene . (M. Ca, Sr, Ba, E A1, B). During the reaction, diethyl ether-soluble double complexes of alkaline earth metal aluminum hydrate with aluminum (boro) lithium hydride, M (A1H4) 2 2XEN4, are formed, the heterogeneity barrier of the reaction in question is overcome. by converting the alkali metal forming aluminum hydride to the form soluble in EtiO. This soluble form M (A1H4) 2 is sufficiently stable to exist in an ethereal solution, but in an excess of aromatic solvent at 80-100 ° C dissociates into alkali metal aluminum hydride and aluminum (boro) lithium hydride. The latter is easily separated from the main washing product in diethyl ether. The solid residue after drying is pure alkaline earth metal aluminum hydride. The duration of the reaction depends on the intensity of mixing. Under cavitation conditions of the reaction mass, the reaction is completed in 1 hour, in a device with a simple, mechanical stirrer, in 2 hours. The choice of the temperature interval SO-IOO C when the post-reaction solution comes in contact with an aromatic solvent is determined alkali metal aluminum hydride from the complex complex M (A1H;)) 2-2Li3H, Below 80 G, there are lithium impurities in the product, above — partial destruction of the aluminum hydride molecule may occur, especially lyumogidrida least stable calcium compound mSlShd row r where M Ca Sr, Ba. Dilution of toluene by a factor of 3–5 after the reactive ether solution is also caused by the necessity to eliminate LiAlH4 and LiBH4 in the final product, as well as to weaken the bond of M (A1H4) 2 with boro or aluminum lithium hydride. Example 1. A mixture of 3.0 g of calcium hydride, 4.12 g of aluminum hydride and 3.0 F of LiBH4 (CaHj: AlHv5: l, iBH4 1; 2: 2) is stirred. 2 hours at 35 ° C in 400 ml of ethyl ether. l interaction using a three-neck flask of 0.5 l, equipped with a mechanical stirrer, reflux condenser and thermometer. The solution clarified by settling is separated from the precipitate; evaporated to 1/3 of the original volume and poured into 1200 ml of toluene at 100 ° C while stirring. The precipitate is washed three times with ether and the solid is dried in vacuum at 80 ° C for 1 hour. Received 6.52 g CafAlH j, yield 93.1%, Found,%: Ca 38.8; A1 52.2; H 7.70. .

Ca (AiH4) t.

Calculated% t Ca 39,22; A1 52.94;

H 7/84.

Example 2. To a solution of 3.8 g of LiAlH, Into 500 ml of diethyl ether, 3.1 g of A1H and 4.7 g of BHH2 are added with stirring and the mixture is stirred for 2 hours. The clarified solution is poured with stirring at 1500 MP of benzene at. The remaining operations are similar to Example 1. 7.12 g of SrCIHH) were obtained. Yield 92%.

Found: Sr 57.9; Al 36.0;

H 5.30. Sr (AlH),. .

Calculated,%: Sr 58.56; Al 36.1; H 5.34.

PRI me R 3. To a solution of 1.8 g of LiBH4 in 500 ml of EtjO at 20 ° C, 0 g of BaH2 and 2.5 g of AlH are added. The remaining operations are similar to Example 1. 7.74 g of Ba (AlH) j were obtained. The yield is 94.2%.

Found,%: Ba 68.2; Al 26.6; H 3.96.

Ba (AlH4l2

Calculated,%: Ba 68,89; A1 27.1; H 4.01.

Thus, the proposed method obtained individual crystalline aluminum hydrides of alkaline earth metals with an output of 90-95% with a purity of more than 99%. The process is simple to perform, and available starting materials are used for the synthesis.

Claims (1)

METHOD FOR PRODUCING ALUMINUM HYDROXIDES OF ALKALINE EARTH METALS by the interaction of binary aluminum hydrides and alkaline earth metals in an organic solvent, what is the result of the fact that they are safe? increasing the purity of the product, the interaction of the starting products ^{1 is} carried out in diethyl ether by adding complex lithium hydride and stirring, the clarified solution is poured into aromatic. the solvent in a volume ratio of 1-3 ^ 5, respectively, at 80-100 ° C; the precipitate obtained is washed with ether and dried. ,.