Synthesis method of borohydride anion B11H14-

Abstract

The invention discloses a synthesis method of a borohydride anion B11H14 <->. According to the synthesis method, hydroboron and halogenated hydrocarbon are taken as raw materials and are fully pyrolyzed in an organic solvent to prepare precursor salt, the precursor salt and quaternary ammonium salt are subjected to an ion exchange reaction, so that inorganic hydroboron is converted into organic quaternary ammonium salt, and then a poor solvent is adopted to achieve the purpose of crystallization and purification. According to the method, B11H14-can be efficiently synthesized, the yield can reach 70% or above, and the purity of B11H14-can reach 99.5% or above after repeated crystallization. The method is suitable for preparing the quaternary ammonium salt compound corresponding to high-purity B11H14-on a hectogram scale.

Description

Technical Field

[0001] This invention relates to a class of high-purity polyhedral borohydride anions (B0). 11 H 14 － The efficient synthesis and purification method belongs to the field of functional materials. Background Technology

[0002] B 11 H 14 ⁻As nido The type polyhedral borohydride has an open cage-like structure consisting of 11 boron atoms and 14 hydrogen atoms (as shown in Formula I), and maintains stability through dihydrogen bond interactions and charge delocalization effects.

[0003]

[0004] Ⅰ B 11 H 14 ⁻Applications cover multiple key areas: In the field of high-energy fuels, as a high-boron, high-energy component, its salt derivatives (such as quaternary ammonium salts, ... cesium Boron salts, due to their high calorific value (58 kJ / g), can significantly improve the specific impulse and burning rate of solid propellants, making them suitable for high-energy propulsion systems such as missiles and spacecraft. Simultaneously, their derivatives, as liquid fuel additives, can reduce ignition delay and improve combustion efficiency, showing significant application potential in tactical equipment fuels. In the biomedical field, it is a core drug delivery system for boron neutron capture therapy, helping to precisely kill cancer cells; Japan has already used drugs based on this anion for the treatment of head and neck cancer. In the field of energy materials, its alkali metal salts (such as NaB)... 11 H 14 It can be used as a solid electrolyte with a conductivity of up to 10⁻³ S / cm at 100°C, making it suitable for all-solid-state sodium batteries. In the field of materials catalysis, it can be used as a catalyst support for olefin hydrogenation reactions and as a precursor for high-temperature resistant materials.

[0005] B 11 H 14Traditional synthetic methods have long suffered from significant drawbacks: one is the pyrolysis of borane, using highly toxic and flammable diborane (B₂H₆) as a raw material. Although the reaction steps are relatively simple and it was initially used for small-scale laboratory preparation, the yield is extremely low (usually less than 30%) and it easily generates complex polyborane mixtures. The other is the reaction of borohydrides with boron halides. Although it uses relatively inexpensive and readily available metal borohydrides (such as NaBH₄) as the basic raw material, it requires the use of highly toxic and corrosive boron trifluoride (BF₃) and an additional oxidation step involving oxidants such as potassium permanganate. The process is cumbersome, and the overall yield is also less than 30%. Furthermore, both of these traditional methods produce homologous byproducts that are difficult to separate, resulting in consistently low purity of the final product, which directly hinders their application in demanding fields. Summary of the Invention

[0006] To address the shortcomings or deficiencies of existing technologies, this invention provides a borohydride anion B 11 H 14 － Synthesis method.

[0007] Therefore, the borohydride anion B provided by this invention 11 H 14 － The synthesis methods include: Step 1: In the presence of a catalyst, under inert gas and at 80–120 °C, borohydride is reacted in an organic solvent to prepare a precursor salt; the catalyst is a haloalkane. Step 2: The precursor salt and quaternary ammonium salt are reacted in water to prepare the polyhedral borohydride R4NB. 11 H 14 R4 represents an alkyl group.

[0008] Step 3 involves washing with water, dissolving in polar solvents, and recrystallizing in unsuitable solvents to treat the polyhedral borohydride R4NB. 11 H 14 Purification was performed to obtain borohydride anion B. 11 H 14 － Organic quaternary ammonium salts.

[0009] An alternative approach is to improve product purity in step 3 by recrystallizing multiple times with unsuitable solvents.

[0010] Alternatively, the borohydride may be sodium borohydride or potassium borohydride.

[0011] Alternatively, the haloalkane may be a chloroalkane or a bromoalkane.

[0012] Alternatively, the organic solvent may be an ether solvent.

[0013] An alternative is that the molar ratio of the borohydride to the haloalkane is 1:1 to 3.

[0014] An alternative approach is to react the precursor salt solution with a saturated quaternary ammonium salt solution in step 2 to prepare the polyhedral borohydride R4NB. 11 H 14 .

[0015] An alternative approach is to have a reaction time of 2 to 10 hours for step 1.

[0016] Alternatively, the quaternary ammonium salt may be selected from tetramethylammonium chloride or tetraethylammonium bromide.

[0017] Alternatively, the polar solvent may be selected from dichloromethane, chloroform, acetone, or 1,2-dichloroethane.

[0018] Alternatively, the undesirable solvent may be selected from petroleum ether, diethyl ether, methyl tert-butyl ether, n-hexane, or cyclohexane.

[0019] Traditional synthesis methods rely on highly toxic and flammable diborane or highly corrosive boron trifluoride, which not only pose high operational risks but also limit the availability of raw materials. This invention uses borohydrides as the core substrate (inexpensive, readily available, and highly stable) in combination with conventional haloalkanes (such as bromoethane), eliminating highly toxic and corrosive raw materials and significantly reducing safety risks in laboratory operations and industrial production. Furthermore, traditional methods generally yield less than 30% of the product; this invention, through an optimized route of "boron pyrolysis + quaternary ammonium salt ion exchange," achieves a total yield of over 70%.

[0020] High-energy fuels, biomedicine and other fields require boron hydride anions (B2O3). 11 H 14 － The purity requirement is extremely high, but traditional methods often fail to meet purity standards due to the difficulty in separating byproducts (mixtures of polyboranes and boric acid). This invention utilizes inorganic borohydride anions (B2) to achieve the desired purity. 11 H 14 － Salt undergoes cation exchange to obtain B 11 H 14 － The organic ammonium salt, specifically the conversion of inorganic salts into organic quaternary ammonium salts, can be purified by recrystallization. This involves a process of "quaternization + repeated crystallization," which, through precise verification by ¹¹B NMR and ¹H NMR, achieves a purity of over 99.5% (e.g., 94.5% after three crystallizations, and >99.5% after six repeated crystallizations). This addresses the core pain point of insufficient purity in traditional processes, directly adapting to high-end applications. Furthermore, this invention is suitable for preparing high-purity B at the 100-gram scale. 11 H 14 － The corresponding quaternary ammonium salt complex.

[0021] This invention also provides a method for synthesizing related intermediate polyhedral borohydrides, the corresponding synthesis method comprising: Step 1: In the presence of a catalyst, under inert gas and at 80–120 °C, borohydride is reacted in an organic solvent to prepare a precursor salt; the catalyst is a haloalkane. Step 2: The precursor salt and quaternary ammonium salt are reacted in water to prepare the polyhedral borohydride R4NB. 11 H 14 R4 represents an alkyl group. Attached Figure Description

[0022] Figure 1 Et4NB before crystallization in this embodiment of the invention 11 H 14 corresponding 11 B NMR spectrum.

[0023] Figure 2 Et4NB after three crystallizations in this embodiment of the invention 11 H 14 corresponding 11 B NMR spectrum.

[0024] Figure 3 In this embodiment of the invention, Et4NB is obtained after six repeated crystallizations. 11 H 14 corresponding 11 B NMR spectrum.

[0025] Figure 4 In this embodiment of the invention, Et4NB is obtained after six repeated crystallizations. 11 H 14 corresponding 1 H NMR spectrum.

[0026] Figure 5 The polyhedral borohydride Et4NB in ​​this embodiment of the invention 11 H 14 High-resolution mass spectra, the image above is B. 11 H 14 - The m / z test values ​​are shown in the figure below, and the predicted values ​​are shown in the figure below.

[0027] Figure 6 For B 11 H 14 － Used as a reference material to analyze the boron content of samples. Detailed Implementation

[0028] Unless otherwise specified, the scientific and technical terms used herein are for the understanding of those skilled in the art. The following examples further illustrate the invention. It should be noted that, based on the synthesis scheme of this invention, those skilled in the art can optimize and select aspects of the method, including but not limited to specific reactants, the ratio of reactants in each step, the temperature and duration of the organic solvents used (including the first and second organic solvents), the order of addition, and product recovery, to achieve the relevant effects of this invention.

[0029] Taking ethyl Et as an example, the polyhedral borohydride Et4NB of this invention... 11 H 14 The structure is shown in Figure II:

[0030] II The corresponding synthesis route is shown in the following example:

[0031] The present invention will be further described in detail below with reference to specific embodiments. All raw materials used in the following embodiments are commercially available products.

[0032] Example: This embodiment uses NaBH4 as a raw material and bromoethane as a catalyst. The specific synthesis steps are as follows: Step 1: In a round-bottom flask equipped with a mechanical stirrer and a reflux condenser, add sodium borohydride (60.0 g, 1.58 mol) and diethylene glycol dimethyl ether (diglyme, 600 mL). Heat the reaction system to 110°C under a nitrogen atmosphere, and slowly add bromoethane (165 mL, 2.21 mol, 0.5 mL / min). Stir vigorously and continue the reaction for 8 hours to allow the sodium borohydride to fully pyrolyze and generate NaB. 11 H 14 The reaction system turned orange-yellow; Step 2: After cooling the reaction mixture obtained in Step 1, filter to remove insoluble matter. Then, perform vacuum distillation on the filtrate to remove the solvent, obtaining a yellow solid. Add 500 mL of deionized water to the yellow solid, stir to dissolve it completely, and filter to remove insoluble matter. Then, add 200 mL of saturated Et4NCl aqueous solution to the aqueous solution, stir thoroughly to carry out ion exchange, generating a large amount of white flocculent precipitate. Collect the crude product Et4NB by vacuum filtration. 11 H 14 (Crude yield 85%), nuclear magnetic resonance spectroscopy analysis showed the product purity to be 85%. Figure 1 As shown, according to 11 B NMR was used to determine the atom, using B atoms as a reference. δ= 14.2, 15.9, 16.8 ppm for Et4NB 11 H 14 The peak may contain boric acid ( ). δ = 19.8 ppm) and other borohydride homologues ( δ =20.5, 23.9, 29.3 ppm); Step 3, the crude product Et4NB obtained in step 2 11 H 14 Wash repeatedly with deionized water to remove boric acid impurities; then dissolve it in dichloromethane, add n-hexane, and recrystallize. Repeat the crystallization process three times. 11 B NMR analysis showed that its purity reached 94.5% ( Figure 2 As shown (based on B atoms); repeated crystallization more than 6 times, 11 The B NMR spectrum shows almost no B impurity peaks, indicating a purity of over 99.5%. Figure 3 As shown (based on the B atom). After recrystallization six times, 1 The H NMR spectrum further confirmed the presence of Et4NB. 11 H 14 Structure ( Figure 4 As shown, MS(ESI) m / z = 133.2186.

[0033] This embodiment obtains Et4NB 11 H 14 Mass spectrometry analysis of the spectrum yielded the following results: Figure 5 As shown.

[0034] B 11 H 14 － It is an important intermediate in the synthesis of o-carboranes. The following synthetic route, involving oxidation and palladium-catalyzed alkyne addition, allows for the efficient synthesis of o-carboranes. (B) 11 H 14 － The synthesis efficiency and purity of intermediates directly determine the synthesis cost and product purity of ortho-boranes.

[0035]

[0036] In addition, the quantitative analysis of boron cluster compounds often employs... 11 However, due to the unique structure of these compounds, their boron spectra are complex and their chemical shift distributions are wide, making it difficult to match suitable reference materials. The boron-containing compounds synthesized in this invention... 11 H 14 －High purity results in chemically stable quaternary ammonium salts with high structural symmetry, making them ideal reference materials. For example... Figure 6 As shown, the high-purity B obtained from the above embodiments 11 H 14 － As a reference material, it is quantitatively added to the sample to be tested (containing B). 10 H 14 In the sample, the boron content was determined by NMR analysis and the integral area ratio.

Claims

1. A synthetic method of borohydride anion B 11 H 14 － characterized in that, The synthesis method comprises: Step 1, in the presence of a catalyst, inert gas and at 80-120 DEG C, borohydride is reacted in an organic solvent to prepare a precursor salt; the catalyst is a halogenated alkane; Step 2, reaction of precursor salt with quaternary ammonium salt in water to prepare polyhedral borohydride compound R4NB 11 H 14 ; R represents an alkyl group. Step 3, purification of polyhedral borohydride compound R4NB 11 H 14 Step 4, purification of borohydride anion B 11 H 14 － organic quaternary ammonium salt.

2. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The purity of the product is improved by multiple recrystallizations in poor solvents in step 3.

3. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The borohydride is sodium borohydride or potassium borohydride.

4. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The halogenated alkane is a chloroalkane or a bromoalkane.

5. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The organic solvent is an ether solvent.

6. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The molar ratio of the borohydride to the halogenated alkane is 1:1-3.

7. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The polyhedral borohydride compound R4NB is prepared by reacting the precursor aqueous salt solution with a saturated aqueous solution of a quaternary ammonium salt in step 2 11 H 14 .

8. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The reaction time in step 1 is 2-10 hours.

9. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The quaternary ammonium salt is selected from tetramethylammonium chloride or tetraethylammonium bromide.

10. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The polar solvent is selected from dichloromethane, chloroform, acetone or 1,2-dichloroethane.

11. The borohydride anion B according to claim 1 11 H 14 － Synthesis method characterized in that, The poor solvent is selected from petroleum ether, diethyl ether, methyl tert-butyl ether, n-hexane or cyclohexane.

12. A method of synthesizing a polyhedral borohydride compound, characterized by, The synthesis method comprises: Step 1, in the presence of a catalyst, inert gas and at 80-120 DEG C, borohydride is reacted in an organic solvent to prepare a precursor salt; the catalyst is a halogenated alkane; Step 2, reaction of precursor salt with quaternary ammonium salt in water to prepare polyhedral borohydride compound R4NB 11 H 14 ; R represents an alkyl group.

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