RU2230067C2 - Method for preparing triarylmethyl cation salts with organoboron anions - Google Patents

Abstract

FIELD: chemistry of organoboron compounds, chemical technology. SUBSTANCE: invention relates to a method for preparing salts consisting of the volume bulky organic cation and bulky organic anion, namely, to triarylmethyl cation salts with organoboron anions. Indicated compounds are used widely as components of highly effective catalytic systems used for preparing polyolefins, among them, in large-tonnage manufacture. Invention describes a method for preparing triarylmethyl cations with organoboron anions of the general formula [Ar₃C][BAr₄], wherein Ar means aryl organic radicals by interaction of triarylmethyl halides with organoboron anion alkaline salts that are used as solid substances. Process is carried out by mechanical treatment of reagents mixture taken in stoichiometric amount, in the absence of solvent, followed by isolation of the end product. Invention provides the possibility for utilization of the easily available parent reagents with high effectiveness and rapidly carrying out the process being with high yield of the end product. EFFECT: improved preparing method. 5 ex

Description

The invention relates to a method for producing salts consisting of a bulky organic cation and a bulky organic anion, in particular salts of the triphenylmethyl cation or its derivatives substituted in the aryl radicals with tetraarylborate anions, in particular fluorinated tetraarylborate anions, such as tetrakis (pentafluorophenylphenyl) boron.

These compounds are widely used as components of high-performance catalytic systems for the production of polyolefins, including in large-scale production [European patent 0277003, 1988. European patent 0277004, 1988. Yang H., Stern C. L., Marks T., J.J. Am. Chem. Soc. 1991. 113. 3623. European Patent 0427697, 1991].

These compounds are obtained by the exchange interaction of solutions of specially selected salts of a triarylmethyl cation and a boron-containing anion in organic solvents. By a special selection of starting materials, solvents, an increase in the duration of the reaction, and carrying out it at the boiling point of the solvents, it is possible to shift the reaction toward the formation of the target product. After completion of the process, the product is separated and purified by recrystallization from a suitable solvent [Bahr S.R., Boudjouk P. Journal of Organic Chemistry. 1992.57 (20). 5545-5547. Brauer D. J., Burger, H. et al. Zeitschrift fur anorganische und allgemeine Chemic. 2001.627 (4). 679-686. Frohn N.J., Franke N. et al. Journal of Organometallic Chemistry. 2000.598 (1). 127-135].

Methods for the synthesis of perfluoroborates were first systematized by Massay and Park [Massey A.G., Park A.J. Journal of Organometallic Chemistry. 1964.2245]. To date, a number of methods have been developed for the synthesis of ionic salts of perfluorophenylborates, in particular triphenylmethyl tetrakis (pentafluorophenylborate), Ph ₃ CB (C ₆ F ₅ ) ₄ [King R.V. Organometallic Synthesis, 1986. V. 3].

The synthesis is most often carried out through the preliminary formation of alkali metal pentafluoroaryl salts by the reaction of alkyl lithium or Grignard reagent with pentafluorobromobenzene, the subsequent exchange reaction with trichloroborane in diethyl ether, and then by prolonged boiling with triphenylchloromethane in an environment of aliphatic solvents [Chien J.C. W., Tsai W. M., Rausch M.D. J. Am. Chem. Soc. 1991. 113. 8570. US patent 5493056, 1996. US patent 6096928, 2000. US patent 6231790, 2001. European patent 505972, 1992. European patent 604961, 1994. International patent WO 9400459, 1994]. After the end of the process, the product contained in the precipitate is separated and recrystallized from a mixture of methylene chloride-hexane.

It should be noted the general disadvantages inherent in the methods of synthesis in a solvent environment according to the indicated schemes. It is noted that operations with a LiC ₆ F ₅ solution are required to be carried out at a temperature of -78 ° C. But even at this temperature they are unsafe, since the reaction mixture often exploded unpredictably [Chen Y.-X., Metz M.V., Li L., Stern C.L., Marks T.JJ Am. Chem. Soc. 1998. 120.6287]. Carrying out reactions in a solvent environment is a multi-stage process, the first stages of which are long, require low temperatures, and the final stage requires prolonged boiling of the reaction mixture; the degree of completion of each stage does not have clear criteria. Significant is the complexity of the selection and low yields of the target product.

Closest to the proposed method is the synthesis of Ph ₃ CB (C ₆ F ₅ ) _{4 by} boiling LiB (C ₆ F ₅ ) ₄ with an excess of Ph ₃ CCl in hexane for 12 hours, followed by separation of the precipitate and recrystallization from a mixture of methylene chloride - hexane . The yield of Ph ₃ CB (C ₆ F ₅ ) ₄ was 64% [Chien J.C. W., Tsai W. M., Rausch M. D. JAm.Chem.Soc. 1991. 113. 8570] - (prototype).

This method has the following disadvantages: the long duration of the process, the need to use large volumes of various solvents, which, among other things, affects the environmental characteristics of the process.

The objective of the invention is the synthesis of salts of triarylmethyl cations with organoboron anions of the general formula [Ar ₃ C] [BAr ' ₄ ], where Ar are aryl organic radicals, for example phenyl, pentafluorophenyl.

The problem is solved in the proposed method by the interaction of triarylmethyl halides with alkaline salts of organoboron anions. The process is carried out by machining a mixture of solid starting reagents, taken in stoichiometric amounts, without solvent, after which the target product is isolated by known methods.

The starting reagents are taken in stoichiometric amounts. The process is carried out without solvent during mechanical activation of the reaction mixture. Monitoring the progress of the reaction is carried out by changing the color of the reaction mixture (from white to orange). The mixture may contain ballast substances, for example alkali metal halides, which do not interfere with the reaction, but may be contained in the starting materials from which it is difficult to separate them.

In the invention, the reaction mixture is machined. As a device for machining, a vibration mill with grinding balls can be used, either a planetary mill or a special grinding device in which the reactor describes a complex trajectory such as a “drunk barrel” [K.G. Myakishev, V.V. Volkov. Vibratory mill activator of mechanochemical reactions. Preprint No. 89-12 of the Institute of Inorganic Chemistry, Siberian Branch of the USSR Academy of Sciences, Novosibirsk. 1989; E.G. Avvakumov. Mechanical methods of activation of chemical processes. Novosibirsk "The science". 1979].

A method for producing salts of triarylmethyl cations with organoboron anions is described in the examples below. In the examples, the inventive method was carried out by carrying out the reaction in a metal hermetically sealed reactor, in which in an inert atmosphere loaded suspended quantities of starting materials and metal balls as an activating nozzle (grinding media). The reaction mixture was subjected to mechanical action on a vibrating ball mill (vibration with a frequency of 12 Hz and an amplitude of 11 mm) for 1-2 hours. After completion of the mechanical treatment, the reaction mixture was a bright orange powder (starting materials — white) and consisted of an alkali metal halide (according to x-ray phase analysis) and the target product. The target product was recovered by treating the reaction mixture with a suitable solvent (methylene chloride, acetonitrile). The solution was filtered, concentrated to a small volume, hexane was added and left for several hours (usually overnight) to crystallize the target product. The resulting borate crystals were separated, washed with hexane and dried in vacuo. All operations for loading the reactor and isolating the product were carried out in an inert atmosphere.

The inventive solid-phase, solvent-free, mechanochemical method for producing salts of triarylmethyl cations with organoboron anions allows the use of readily available starting reagents, highly efficient, safe and fast process with a high yield of the target product.

Thus, the analysis of the existing scientific, technical and patent literature showed that the claimed combination of features of the proposed technical solution meets the criteria of novelty and inventive step.

The inventive method for producing salts of triarylmethyl cations with organoboron anions is illustrated by the following examples.

Examples

Synthesis of starting compounds.

Ph ₃ CCl and Ph ₃ CBr were obtained according to the usual methods [Agranomov A.E., Shabarov Yu.S. Laboratory work in an organic workshop. Ed. 2nd. M .: Chemistry. 1974. P.176. General Workshop on Organic Chemistry (Organicum). M .: World. 1965. S. 303].

Obtaining alkaline salts of borate anions

A mixture of LiB (C ₆ F ₅ ) ₄ + 3LiCI was prepared by reacting n-butyllithium with a stoichiometric amount of C ₆ F ₅ Br in hexane, followed by treatment of the mixture with boron chloride at -80 ° C [Massey A.G., Park A.J. Journal of Organometallic Chemistry. 1964. 2.245]:

C ₄ H ₉ Li + C ₆ F ₅ Br → C ₆ F ₅ Li + C ₄ H ₉ Br

4C ₆ F ₅ Li + BCl ₃ → LiB (C ₆ F ₅ ) ₄ + 3LiCl.

The precipitate formed was separated and used in the reactions.

NaB (C ₆ F ₅ ) _{4 was} prepared by the Grignard reaction from C ₆ F ₅ Br, magnesium, and the non-volatile readily available boron reagent sodium tetrafluoroborate [Bahr SR, Boudjouk P. Journal of Organic Chemistry. 1992.57 (20). 5545-5547]:

C ₆ F ₅ Br + Mg → C ₆ F ₅ MgBr

C ₆ F ₅ MgBr + NaBF ₄ → NaB (C ₆ F ₅ ) ₄ + MgBrF

KB (C ₆ F ₅ ) _{4 was} obtained by precipitation from an aqueous solution of lithium or sodium salt of anion B (C ₆ F ₅ ) $\genfrac{}{}{0ex}{}{\text{-}}{\text{4}}$ the action of an aqueous solution of potassium chloride:

NaB (C ₆ F ₅ ) ₄ + KCl → KB (C ₆ F ₅ ) ₄ ↓ + NaCl

NaB (C ₆ H ₅ ) ₄ , a commercial product (VEB JENAPHARM – LABORCHEMIE APOLDA, “chda”), was used without further purification.

According to our method, we use available starting materials — commercial or easily synthesized triphenylchloromethane or triphenylbromomethane and alkali metal salts of the Br anion $\genfrac{}{}{0ex}{}{\text{-}}{\text{4}}$ . Note that the potassium salt is well suited for this reaction, which is stable, non-hygroscopic, and is obtained from other salts by precipitation from aqueous solutions with a potassium ion. The precipitation of potassium tetraphenylborate from aqueous solutions is a quantitative analytical reaction to potassium, and derivatives with fluorinated aryl radicals are even more stable.

Example 1 (prototype, the reaction in solution [Chien J.C. W., Tsai W. M., Rausch M. D. J. Am. Chem. Soc. 1991. 113. 8570]).

A mixture of 2.6 g of LiB (C ₆ F ₅ ) ₄ (3.79 mmol) and 1.8 g of Ph ₃ CCl (6.46 mmol) was boiled in 200 ml of hexane for 12 hours. Hexane gradually turned yellow, and the precipitate at the bottom of the flask turned brown. The precipitate was filtered off, washed with hexane (2 times 20 ml) and dried in vacuo. The resulting product was recrystallized from methylene chloride - hexane. Received Ph ₃ CB (C ₆ F ₅ ) ₄ in the form of orange crystals. Yield 1.7 g (47%). (48.6%).

Example 2 (to compare the claimed in the invention method with the method of the prototype in Example 1).

A mixture of solids (LiB (C ₆ F ₅ ) ₄ + 3LiCl) containing 1.03 g of LiB (C ₆ F ₅ ) ₄ (1.50 mmol), 0.42 g of Ph ₃ Cl (1.50 mmol) and 20 steel balls with a diameter of 7.3 mm (total weight ~ 150 g) were loaded into a steel hermetic reactor with a volume of ~ 80 cm ³ . The reactor was mounted on a vibrating ball mill and the reaction mixture was subjected to mechanical action (vibration with a frequency of 12 Hz and an amplitude of 11 mm) for 1 hour. After the cessation of machining, the reaction mixture of the starting white substances turned into a bright orange powder. The powder was transferred to a Schlenk vessel. The reactor and steel balls were washed with methylene chloride (3 times 20 ml). The resulting solution was also transferred to a Schlenk vessel with powder of reaction products. The solution was filtered through a thick glass filter. The filtrate was concentrated to a volume of ~ 5 ml. To the resulting concentrated solution of the target product in methylene chloride was added 30 ml of petroleum ether and left overnight for crystallization. After crystallization, precipitated crystals of Ph ₃ CB (C ₆ F ₅ ) ₄ were separated from the solution by filtration, dried in vacuum. The yield of Ph ₃ CB (C ₆ F ₅ ) ₄ was 0.85 g (61%).

Analysis.

Found,%: H 1.72; C 53.48; F 41.29.

Calculated for Ph ₃ CB (C ₆ F ₅ ) ₄ ,%: H 1.64; C 55.99; F 41.19.

Thus, according to the proposed method, it is possible to use a reaction mixture containing ballast substances (LiCl).

Example 3 (for comparing the inventive method with the method of the prototype in Example 1 and the possibility of using other starting materials for comparison with Example 2).

The reaction was carried out and the product was isolated as described in example 2. A mixture of KB (C ₆ F ₅ ) ₄ (1.20 g, 1.67 mmol) and Ph ₃ CCl (0.47 g, 1, 69 mmol). After extraction and crystallization, 1.15 g of Ph ₃ CB (C ₆ F ₅ ) _{4 was} obtained as orange crystals. Yield 75%.

Thus, in the solid-phase reaction, in contrast to the prototype, it is possible to successfully use the potassium salt of borate anion as a starting material. Comparison with Example 2 shows that the potassium salt of the tetraaryl borate anion can be used as the starting reagent.

Example 4 (for comparing the inventive method with the method of the prototype in Example 1 and the possibility of using other starting materials for comparison with Examples 2, 3).

The reaction was carried out and the product was isolated as described in example 2. A mixture of KB (C ₆ F ₅ ) ₄ (0.91 g, 1.27 mmol) and Ph ₃ CBr (0.41 g, 1, 27 mmol). After extraction of the reaction mixture and crystallization of the product, 0.95 g of Ph ₃ CB (C ₆ F ₅ ) _{4 was} obtained. Yield 81%.

This example shows the possibility of using triphenylmethane bromide rather than chloride as the starting material.

Example 5 (for comparing the inventive method with the method of the prototype in Example 1 and the possibility of using non-fluorinated borate anions for comparison with Examples 1-4).

The reaction was carried out as described in Example 2. A mixture of white starting materials — NaBPh ₄ (1.10 g, 3.21 mmol) and Ph ₃ CCl (0.90 g, 3.23 mmol) —was subjected to mechanical treatment for 1 hour. Received a red-brown granular powder, which is a mixture of Ph ₃ CBPh ₄ and NaCl. Individual products were not isolated from the resulting mixture, since upon dissolution they quickly decompose and decolorize.

This example shows the possibilities of using the proposed method to obtain triarylmethyl derivatives of non-fluorinated tetraarylborate anions.

The above examples show that the inventive solid-phase, solvent-free, mechanochemical method for producing salts of triarylmethyl cations with organoboron anions allows the use of readily available starting reagents, highly efficient, safe and fast process with high yield of the target product.

Claims (1)

The method of producing salts of triarylmethyl cations with organoboron anions of the general formula [Ar ₃ C] [BAr ₄ ], where Ar are aryl organic radicals, by the interaction of triarylmethyl halides with alkaline salts of organoboron anions, characterized in that the starting reagents are used in the form of solids and the process is carried out by machining a mixture of reagents taken in stoichiometric amounts in the absence of solvent, followed by isolation of the target product.