RU2158221C2 - Polyhedral closo-hydroborates of chitosan and method of preparation thereof - Google Patents

Abstract

FIELD: pyrotechnical materials. SUBSTANCE: polyhedral closo-hydroborates of chitosan with formula (XH)₂BnHn, wherein n = 6, 10, 12 and X is C₆O₄H₁₁N (chitosan), are synthesized by interaction, in aqueous medium, of substances containing chitosanium cations and anions of corresponding polyhedral closo-hydroboric acids at 2:1 molar ratio to form desired product precipitate, which is further isolated by conventional techniques. Substances containing chitosanium cations are soluble chitosan salts or aqueous suspension of powdered chitosan and aforesaid anions are soluble alkali and alkali-earth metal salts or corresponding acids themselves. Resulting products are capable of inflaming from fire and rapidly and completely burning out, which makes these substances proper for use as quick-burning materials, for instance as pyrotechnical components. EFFECT: enlarged assortment of pyrotechnical materials. 5 cl, 3 dwg, 13 ex

Description

The invention relates to the chemistry of polyhedral borohydride compounds, and in particular to polyhedral chlosan closohydroborates of composition (XH) ₂ B _n H _n , where n = 6, 10, 12, a X = C ₆ O ₄ H ₁₁ N (chitosan), which can be used as a quick-burning component of pyrotechnic compositions, as well as to a method for their preparation.

 These compounds, their properties, method of preparation and scope of use have not been previously described.

Known double decaborate and dodecaborate nitrates of rubidium and cesium, similar to the claimed presence of polyhedral closo-hydroborate anions in their composition. Compounds R ₂ B ₁₀ H ₁₀ • RNO ₃ and R ₂ B ₁₂ H ₁₂ • RNO ₃ (R = Rb, Cs) are prepared by reacting in an aqueous solution substances containing B ₁₀ H ₁₀ ^2- -, B ₁₂ H ₁₂ ^{2 -} - and NO ₃ ^- anions and R ⁺ cation. The sparingly soluble double salt precipitate is filtered off and, in order to purify it from impurities, recrystallized (Kanaeva O.A., Kuznetsov N.T., Sosnovskaya O.O., Goyeva L.V. // Journal of Inorganic Chemistry, 1980, t 25, c. 9, p. 2380-2383).

Cs ₂ B ₁₀ H ₁₀ • CsNO ₃ and Cs ₂ B ₁₂ H ₁₂ • CsNO ₃ due to flammability and relatively high exo-effect of their combustion, it is proposed to use as a flammable substance (U.S. Pat. No. 989295, MKI C 01 V; C 06 B, F 07 F, 1965).

The disadvantage of Cs ₂ B ₁₀ H ₁₀ • CsNO ₃ and Cs ₂ B ₁₂ H ₁₂ • CsNO ₃ as a flammable substance is their relatively low calorific value, as well as the high cost of cesium in its composition.

The closest in composition to the claimed compounds are salts of polyhedral closo-hydroborate acids H ₂ B ₁₀ H ₁₀ and H ₂ B ₁₂ H ₁₂ with organic, for example, alkyl ammonium, bases (R _m NH _4-m ) OH, where R = CH ₃ , C ₂ H ₅ , C ₄ H ₉ , and m = 1-4. Replacing expensive cesium with a cheaper and lighter alkyl ammonium cation makes their practical use as an energy-intensive material more realistic.

The above compounds are obtained by neutralizing polyhedral closo-hydroborate acids with the corresponding alkyl ammonium bases with a molar ratio of acid to base equal to 1: 2. From the resulting solution by evaporation to dryness at a temperature above 100 ^o C to a constant weight, the target product is isolated - a white crystalline powder with a yield close to 100%. (Ivanov S.V., Malinina E.A., Solntsev K.A., Kuznetsov N.T. // Coordination chemistry, 1992, v. 18, No. 4, p. 394-400).

 The disadvantage of these compounds is their low flammability. When ignited, they light up, but when the exposure to them ceases, the flame goes out due to the formation of a surface layer of boron oxide.

 The objective of the invention is to obtain new polyhedral borohydride compounds, more acceptable as energy-intensive quick-burning material, that is, with higher combustibility and comparable in cost to the prototype.

где символ "цикл BH" означает один из следующих анионов: B₆H₆ ^2-, B₁₀H₁₀ ^2-, B₁₂H₁₂ ^2-, и способом их получения.The problem is solved by polyhedral closo-hydroborates of chitosan of the general formula 1:

where the symbol "cycle BH" means one of the following anions: B ₆ H ₆ ^2- , B ₁₀ H ₁₀ ^2- , B ₁₂ H ₁₂ ^2- , and the method for their preparation.

The proposed compounds are salts of polyhedral closo-hydroborate acids with chitosan. Chitosan is known to be a natural positively charged gross homopolymer of (C ₆ O ₄ H ₁₁ N) _x , which is obtained from the chitin of living organisms, such as crab shell or ocean krill (Brief chemical encyclopedia. Ed. By I.L. Knunyants T. 5. M.: Soviet Encyclopedia. 1967. P.683). Chitosan, being a typical Lewis base, forms salts with various Lewis acids. The most famous salts of chitosan with acetic and formic acids, which can be obtained by dissolving chitosan in 3% solutions of these acids. Data on the formation of salts of polyhedral closohydroborate acids with chitosan have not been identified.

 For new compounds, a property to catch fire when exposed to temperature was found. At the same time, they continue to burn vigorously with a white-green flame and burn almost completely with the formation of a dark boron-containing solid residue.

The method of producing polyhedral closo-hydroborates of chitosan of formula 1 consists in the interaction in an aqueous medium of substances containing chitosanium cations and anions of the corresponding polyhedral closo-hydroborate acids, taken in a 2: 1 molar ratio, with the formation of a precipitate of the target product and its subsequent isolation by known methods, according to General reactions:
2 (C ₆ O ₄ NH) ⁺ + B _n H _n ^2- = (C ₆ O ₄ H ₁₁ NH) ₂ B _n H _n ,
where n = 6, 10, 12.

 The resulting polyhedral closo-hydroborates of chitosan precipitate in the form of practically insoluble salts, which is a white curd. The resulting precipitate is separated from the mother liquor, for example, by filtration or centrifugation, and then dried to constant weight at a temperature not higher than the temperature of thermal decomposition of the target product.

 As substances containing chitosan cations, chitosan or its salts are readily soluble in water, for example formate, acetate, chitosan fluoride. In order to increase the reaction rate of the interaction of chitosan with acids (which is solid-liquid phase), it is advisable to use powdered chitosan. The preferred option is to use a fine suspension of freshly precipitated chitosan.

 As the substances containing anions of polyhedral closohydroborate acids, both the acids themselves and their alkali and alkaline earth metal salts, soluble in water and not prone to hydrolysis, for example, lithium, sodium, potassium, rubidium, cesium, ammonium, magnesium salts, are used. calcium, barium.

 The optimal molar ratio of chitosan cations to anions of the corresponding polyhedral closohydroborate acids is 2: 1.

 If the optimal ratio of the starting components is violated, the degree of use of one of them decreases; its unjustified overspending, which leads to a drop in the yield of the target product and its cost.

 So, with a lack of chitosan or its salt with respect to polyhedral closo-hydroborate acid or its salt, the excess acid or its salt does not bind to chitosan and goes into solution by filtration.

 With an excess of chitosan or its salt in excess of the claimed, there is an inexpedient cost overrun of these substances. The excess of the soluble chitosan salt is lost, passing into the filtrate, and in the case of using an excess of chitosan, its mixture is formed with the desired polyhedral chlosan closo-hydroborate, which is difficult to separate. This leads to a loss of calorie content of the target product by reducing the proportion of high-calorie borohydride component in the product.

 In the case of obtaining the target product by the interaction of salts of chitosan and polyhedral closo-hydroborate acids or its salts, the precipitate of the target product after separation from the mother liquor is washed from reaction by-products. To facilitate washing, it is preferable to use such starting salts so that the by-product is as soluble as possible.

Separated from the mother liquor, the target product is dried to constant weight. The optimum drying temperature of the resulting precipitate should not exceed in the general case the temperature of the thermal degradation of the polyhedral chlosan hydroborates of formula 1 (about 105 ^° C.).

It has been experimentally shown that, at temperatures above 105 ^o C, chemical changes in the resulting product are possible, confirmed by the onset of a protracted exoeffect with weight loss on the DTA curve of thermogravigrams of polyhedral clozo-hydroborates of chitosan taken in air (see Fig. 1), which can lead to changes in the composition and properties of the target compound.

Bringing the resulting product to constant weight is possible at lower temperatures, however, this is irrational due to the length of the process. So, for example, the drying time of the samples of the target product obtained under identical conditions, at a temperature of 100 ^o C is up to 1.5 hours, and at a temperature of 60 ^o C - up to 8 hours. The yield of target products resulting from the implementation of the method in the claimed conditions , is close to 100%, and its insignificant decrease is associated with mechanical losses of the substance on chemical utensils.

 Depending on the requirements of the consumer, the target product can be obtained in various shapes, types and sizes. So, by forcing a wet plastic precipitate of the target product through dies, followed by cutting the filaments into pieces of a certain length, it is possible to obtain polyhedral clozo-hydroborates of chitosania in the form of filaments or cylinders. When cutting wet plates of the product, you can get it in the form of plates of the desired geometric shape and specified sizes.

 In addition, the dried solid product is easily crushed into a yellowish powder. When the fine suspension of the precipitate dries, films with good adhesion to the surface can be obtained.

 X-ray diffraction patterns of the obtained compounds differ from x-ray diffraction patterns of the starting components, which indicates the formation of individual chemical compounds.

The IR spectra of the claimed compounds, taken on Specord 75-IR and Perkin-Elmer, in the form of a suspension of chitosan polyhedral closohydroborates in petroleum jelly and perfluorinated oil, as well as its thin films, contain, in addition to absorption bands of the functional groups of the initial chitosan (Fig. 2), also characteristic absorption bands related to B _n H _n ² -anions in the region of 2425-2480 cm ^-1 (Fig. 3) (for example, dodecahydro-closo-dodecaborate of chitosan in the form of a suspension in perfluorinated oil).

The determination of carbon, hydrogen and nitrogen was carried out by known methods used for the analysis of organic substances (Mazor L. Methods of organic analysis. M: Mir, 1986. P. 147). The boron content was found by the gravimetric method using the weight form of boron oxide B ₂ O ₃ formed as a result of burning a sample in a quartz ampoule during microanalysis for carbon and hydrogen. The oxygen content was determined by difference.

 The purity of washing the target product from metal cations was controlled by their absence in the wash water using atomic adsorption analysis.

 Polyhedral clozo-hydroborates of chitosan exhibit properties that make it possible to use them as an effective fast-burning high-calorie material.

Known alkyl ammonium salts of polyhedral closohydroborate acids are similar to those claimed in composition, structure and property to ignite when ignited. However, without a supporting effect on them, the flame stops burning. The inventive compounds have a significant advantage over these known compounds, which consists in their more energetic, faster, spontaneous and complete combustion, which can be explained by their structure. Upon binding of polyhedral closo-hydroborate acid to chitosan, a three-dimensional network structure is formed in which the B _n H _n ² -anions are located as separate groups that are not conglomerated into a strong crystal lattice. The oxygen atoms that make up this compound are in close proximity to the combustible boron and hydrogen atoms of the polyhedral closo-hydroborate anions, thereby causing a very fine distribution of the oxidizing agent and the fuel. Due to the network structure of the claimed compounds, there are no obstacles to the free access of oxygen molecules to fuel. It has also been experimentally shown that, during combustion, these compounds greatly swell, increasing many times in volume, which creates improved conditions for the rapid and complete occurrence of a solid-gas-phase combustion reaction.

 Thus, the proposed new compounds - polyhedral closo-hydroborates of chitosan - as a quick-burning high-calorie material provide a new technical result, which makes them more preferred when used in practice.

 The invention is illustrated by the following examples.

 Example 1

 As the starting point, finely ground chitosan of the M brand (medical) is used, manufactured by Combio LLP (Vladivostok) according to TU 15-01 482-88, which is a white powder with a yellow tint, color in the form of thin lamellar particles no more 0.3 mm across. The moisture content of chitosan is not more than 8.0%, the ash content is not more than 0.3%, and the residual acetogroups are not more than 4.0%. The elemental composition of the sample, wt.%: C - 44.8; H - 6.9; N - 8.6; O - 39.7, which corresponds to a 98% degree of chitin deacetylation and a conditional molecular weight of 162.02 cu

0.32405 g (2.00 mmol) of chitosan dried at 105 ^° C. is dissolved in 100 ml of a 3% aqueous solution of acetic acid to form soluble chitosan acetate. To the resulting clear yellowish viscous solution, 50 ml of an aqueous solution of sodium dodecahydro-closo-dodecaborate containing 0.18780 g (1.00 mmol) of Na ₂ B ₁₂ H _{12 is} added. The mixture is vigorously stirred, and the resulting white cheesy precipitate is filtered off through a glass filter with a porosity of 4. Sodium acetate is washed on the filter with distilled water until Na ⁺ disappears in the washings. The precipitate is dehydrated, compacted, leveled with a thickness of 3-3.5 mm and dried at a temperature of 100 ^o C for 1.5 hours to constant weight. 0.46560 g (0.995 mmol) of dodecahydro-closo-dodecaborate of chitosan is obtained in the form of a round plate of light brown color with a thickness of 1.5-2.0 mm (decrease after drying by 43-50%). The product yield is 99.5%.

Calculated for (XH) ₂ B ₁₂ H ₁₂ , wt. %: C - 31.01; H - 7.79; N -5.98; B - 27.72; O is 27.50.

 Found, wt.%: C - 31.0; H - 7.8; N, 6.0; B - 27.7; O is 27.5.

 Example 2

0.32405 g (2.00 mmol) of chitosan dried at 105 ^° C. is dissolved in 100 ml of a 3% aqueous solution of hydrofluoric acid to form chitosan fluoride. To the resulting clear yellowish viscous solution was added 50 ml of an aqueous solution of potassium decahydro-closo-decaborate containing 0.19640 g (1.00 mmol) K ₂ B ₁₀ H ₁₀ . Subsequent operations to obtain the target product are carried out as in example 1. The precipitate is dehydrated, filled into a syringe and squeezed out through a hole with a diameter of 1.5 mm in the form of threads 50-100 mm long. The threads are dried in air until they harden, while they are shortened by 30-40 and reduced in diameter by 40-50%. Then they are dried in a bottle at a temperature of 105 ^o C for 1 h to constant weight. 0.44280 g (0.99 mmol) of (XH) ₂ B ₁₀ H _{10 are} obtained in the form of yarns, which corresponds to a 99.0% yield of the target product.

Calculated for (XH) ₂ B ₁₀ H ₁₀ wt. %: C - 32.66; H - 7.75; N, 6.30; B - 24.33; 0 - 28.96.

 Found, wt.%: C - 32.7; H - 7.7; N, 6.3; B - 24.3; O is 29.0.

 Example 3

 Get decahydro-closo-decaborate chitosan in accordance with the conditions of example 2. The obtained strands of the target product are slightly dried in air, and then cut into pieces with a length of 2-2.5 mm and dried, as in example 2. Receive 0.46415 g (0.992 mmol ) decahydro-closo-decaborate of chitosan in the form of yellow cylinders, which corresponds to a 99.2% yield of the target compound.

Calculated for (XH) ₂ B ₁₀ H ₁₀ , wt.%: C - 32.66; H - 7.75; N, 6.30; B - 24.33; O - 28.96.

 Found, wt.%: C - 32.7; H - 7.7; N, 6.30; B - 24.3; O is 29.0.

 Example 4

0.32405 g (2.00 mmol) of chitosan dried at 105 ^° C. is dissolved in 100 ml of a 3% aqueous solution of acetic acid. 200 ml of an aqueous solution of cesium hexahydro-closose-hexaborate containing 0.33675 g (1.00 mmol) of Cs ₂ B ₆ H ₆ are added to the resulting viscous, viscous yellowish solution. Subsequent operations until the desired product is obtained and drying to constant weight as in example 1. The dehydrated washed precipitate is transferred to a glass plate and spread in an even layer 1.5–2.0 mm thick, then parallel cuts are applied with a scalpel in steps of 4–4.5 mm, first along and then across the plate. with the product is kept in the air until you drying, as a result of which the chopped mass breaks up into separate slightly curved square plates with a side of 2.0-2.5 mm (decrease after drying 50-45%) and a thickness of 0.7-1.0 mm (decrease by 53-50% ) 0.39420 g (0.993 mmol) of chitosan hexahydro-closo-hexaborate are obtained, which corresponds to a 99.3% yield of the target product.

Calculated for (XH) ₂ B ₆ H ₆ , wt. %: C - 36.55; H - 7.65; N - 7.05; B - 16.34; O is 32.41.

 Found, wt.%: C - 36.6; H - 7.7; N - 7.0; B - 16.3; O is 32.4.

 Example 5

0.32405 g (2.00 mmol) of dried chitosan at 105 ^{° C. is} dissolved in 100 ml of a 3% aqueous solution of acetic acid. To the resulting clear yellowish viscous chitosan acetate solution was added 150 ml of a 0.4 N aqueous NaOH solution to form chitosan. A fine precipitate of chitosan is filtered and washed with distilled water until there is no Na ⁺ in the washings. Freshly precipitated chitosan is transferred into a beaker, diluted with water to 200 ml, stirred up, and 50 ml of an aqueous solution containing 0.14386 g (1.00 mmol) of H ₂ B ₁₂ H ₁₂ are added to the resulting suspension. The mixture is vigorously stirred, and the resulting cheesy precipitate of dodecahydro-closo-dodecaborate of white chitosania is filtered. The remaining operations in example 1. The yield of the target compound is 99.0%.

Calculated for (XH) ₂ B ₁₂ H ₁₂ , wt.%: C - 31.01; H - 7.79; N, 5.98; B - 27.72; 0 - 27.50
Found, wt.%: C - 31.0; H - 7.8; N, 6.0; B - 27.7; O is 27.5.

 Example 6

0.32405 g (2.00 mmol) of marketed powdered chitosan dried at 105 ^° C is added to 100 ml of water, and 50 ml of an aqueous solution containing 0.12022 g (1.00 mmol) of H ₂ B ₁₀ H is added to the resulting suspension. ₁₀ . The mixture was vigorously stirred with a magnetic stirrer for 1 day at room temperature. Moreover, as the formation of decahydro-closo-decaborate of chitosan, the initial light yellow powder of chitosan swells, whitens and passes into a white curd mass. The precipitate was filtered off and dried at a temperature of 100 ^° C. for 1.5 hours to constant weight. 0.44025 g (0.991 mmol) of decahydro-closo-decaborate chitosan is obtained in the form of a yellowish-white powder that is easily milled into powder, which corresponds to a 99.1% yield of the target compound.

Calculated for (XH) ₂ B ₁₀ H ₁₀ , wt.%: C - 32.66; H - 7.75; N, 6.30; B - 24.33; O - 28.96.

 Found, wt.%: C - 32.7; H - 7.7; N, 6.3; B - 24.3; O is 29.0.

 Example 7

Dodecahydro-closo-dodecaborate of chitosan was prepared according to the conditions of Example 1 except that 0.18190 g (1.00 mmol) of CaB ₁₂ H _{12 were} taken for 0.32405 g (2 mmol) of chitosan. Obtain 0.46650 g (1.00 mmol) of the target product, which corresponds to a 99.5% yield.

Calculated for (XH) ₂ B ₁₂ H ₁₂ , wt.%: C - 31.01; H - 7.79; N, 5.98; B - 27.72; 0 - 27.50.

 Found, wt.%: C - 31.0; H - 7.8; N, 6.0; B - 27.7; 0 - 27.5.

 Example 8

Chitosania dodecahydro-closo-dodecaborate is prepared in accordance with the conditions of Example 1 except for the amount of initial chitosan taken for the synthesis, which is 0.35645 g (2.20 mmol). 0.46560 g (0.995 mmol) of dodecahydro-closo-dodecaborate of chitosan is obtained, which corresponds to a 99.5% yield (Na ₂ B ₁₂ H ₁₂ ) of the target compound and a 90.9% degree of use of chitosan.

Calculated for (XH) ₂ B ₁₂ H ₁₂ , wt.%: C - 31.01; H - 7.79; N, 5.98; B - 27.72; O is 27.49.

 Found, wt.%: C - 31.0; H - 7.8; N, 6.0; B - 27.7; O is 27.5.

 Example 9

 Chitosan dodecahydro-closo-dodecaborate is prepared in accordance with the conditions of Example 5 except for the amount taken for the synthesis of chitosan, which is 0.34835 g (2.15 mmol).

 0.48730 g of a light brown product is obtained.

Calculated for (XH) ₂ B ₁₂ H ₁₂ , wt.%: C - 31.01; H - 7.79; N, 5.98; B - 27.72; O is 27.49.

 Found, wt.%: C - 31.7; H - 7.8; N, 6.0; B - 26.4; O is 28.1. The final product is a mixture of the desired dodecahydro-closo-dodecaborate chitosan (95.06 wt.%) With the starting chitosan (4.94 wt.%).

 Example 10

 Decahydro-closo-decaborate of chitosan is obtained in accordance with the conditions of example 2 with the exception of the amount taken for the synthesis of chitosan, which is 0.29165 g (1.80 mmol).

Obtain 0.39745 g (0.9 mmol) of the target product is a light brown color, which corresponds to a 99.4% yield on chitosan and 90.0% degree of use of K ₂ B ₁₀ H ₁₀ .

Calculated for (XH) ₂ B ₁₀ H ₁₀ , wt.%: C - 32.66; H - 7.75; N, 6.30; B - 24.33; O - 28.96.

 Found, wt.%: C - 32.7; H - 7.7; N, 6.3; B - 24.3; O is 29.0.

 Example 11

Decahydro-closo-decaborate of chitosan is obtained in accordance with the conditions of example 6 except for the amount taken for the synthesis of chitosan, which is 0.30785 g (1.90 mmol). Obtain 0.41995 g (0.945 mmol) of decahydro-closo-decaborate chitosan, which corresponds to a 99.5% yield on chitosan and a 95.0% degree of use of H ₂ B ₁₀ H ₁₀ .

Calculated for (XH) ₂ B ₁₀ H ₁₀ , wt. %: C-32.66; H-7.75; N-6.30; B-24.33; O-28.96.

 Found, wt.%: C-32.7; H-7.7; N-6.3; B-24.3; O-29.0.

 Example 12

Chitosan hexahydro-closo-hexaborate was prepared according to the conditions of Example 4 except for the amount of Cs ₂ B ₆ H ₆ cesium hexahydro-closo-hexaborate taken for the synthesis, which was 0.30305 g (0.90 mmol). Obtain 0.35410 g (1.79 mmol) of the target product is a light brown color, which corresponds to 99.5% yield on Cs ₂ B ₆ H ₆ and 90.0% degree of use of chitosan acetate.

Calculated for (XH) ₂ B ₆ H ₆ , wt. %: C - 36.55; H - 7.65; N - 7.05; B - 16.34; O is 32.41.

 Found, wt.%: C - 36.6; H - 7.7; N - 7.0; B - 16.3; 0 - 32.4.

 Example 13

0.32405 g (2.00 mmol) of marketed powdered chitosan dried at 105 ^° C is added to 100 ml of water, and 50 ml of an aqueous solution containing 0.14385 g (1.00 mmol) of H ₂ B ₁₂ H is added to the resulting suspension. ₁₂ . The mixture was vigorously stirred with a magnetic stirrer for 1 day at room temperature. The resulting white curdled precipitate of dodecahydro-closo-dodecaborate of chitosan is filtered off and dried at a temperature of 120 ^o C for 0.2 h to constant weight. Obtain 0.46090 g (0.985 mmol) of dodecahydro-closo-dodecaborate chitosan, which corresponds to a 98.5% yield of the target product.

Calculated for (XH) ₂ B ₁₂ H ₁₂ , wt.%: C - 31.01; H - 7.79; N, 5.98; B - 27.72; O is 27.50.

Found, wt.%: C - 34.9; H - 7.2; N, 6.5; B - 29.9; O is 24.3. A noticeable difference from the calculated composition is associated with the occurrence of thermal oxidative degradation of (XH) ₂ B ₁₂ H ₁₂ with the formation of gaseous reaction products due to drying of the product at a temperature above 105 ^o C. In this case, a decrease in the yield of the product is also observed.

Claims (5)

1. Polyhedral closo-hydroborates of chitosan of the general formula

where the symbol "BH cycle" means one of the following anions: B ₆ H ₆ ^2- , B ₁₀ H ₁₀ ^2- , B ₁₂ H ₁₂ ^2- .  2. A method of producing polyhedral closo-hydroborates of chitosan of the general formula I, characterized in that they interact in an aqueous medium with substances containing chitosan cations and anions of the corresponding polyhedral closo-hydroborate acids taken in a 2: 1 molar ratio to form a precipitate of the target product and its subsequent isolation by known methods.  3. The method according to claim 2, characterized in that as substances containing chitosan cations, use soluble salts of chitosan or an aqueous suspension of powdered chitosan, and as substances containing anions of the corresponding polyhedral closo-hydroborate acids, their soluble alkaline and alkaline earth metals or the acids themselves.  4. The method according to p. 2, characterized in that in the case of obtaining the target product by the interaction of salts of chitosan and polyhedral closo-hydroborate acids, the precipitate of the target product after separation from the mother liquor is washed from the reaction by-products.  5. The method according to claim 2, characterized in that the obtained target product is dried to constant weight at a temperature not higher than the temperature of its thermal degradation.

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