DE871302C - Process for the production of aromatic halosilanes - Google Patents

Description

The invention relates to an improved process for the production of aromatic halosilanes, in which there is a valence of the Si atom by bonding with a C atom of a benzene hydrocarbon is saturated.

It has been found that a benzene hydrocarbon, which is free from aliphatic unsaturated side chains, with a polyhalogenmonohydrosilane in the presence of a silicon-boron complex compound at a reaction temperature above 150 ⁰ and below 420 ⁰ and under such a pressure that at least part of the reaction mixture in liquid Phase is present, can be brought into reaction with the formation of arylhalosilanes.

The benzene hydrocarbons to be used according to the invention include: benzene, polyphenyls such as diphenyl and naphthalene, and alkyl-substituted benzenes, e.g. B. toluene, xylene, isopropylbenzene or ^I > 3. 5-trimethylbenzene. Since to a certain extent a cleavage of side chains in substances such as. B. isopropylbenzene, can occur and relatively pure products are obtained, if side chains only contain 1 carbon atom, it is preferable to use only benzene or polyphenyls or the methyl derivatives of benzene as aromatic hydrocarbons.

The polyhalogenmonohydrosilanes which are suitable according to the invention for the process are compounds

gene of the general formula R _n HSiCl ₃ _ ", in which each R is a monovalent hydrocarbon radical free of unsaturated aliphatics and η is a number from ο to ι. The polyhalogenmonohydrosilanes to be used with preference are HSiCl ₈ , CH ₃ HSiCl ₂ and C ₆ H ₅ HSiCl ₂ . ·

The SiHcium-boron complex compound according to the invention is a substance in which at least some, but only part of the valences of Si

ίο and B through substituents from the group: phenyl, Methyl, alkoxy, halogen and hydrogen are saturated, while the remaining valences of Si and B are saturated by oxygen atoms, these with the Si and B atoms of the complex compound are connected.

The Si-B-complex compounds are used in amounts such that at least 0.01 ° / ₀ and generally less than 0.05 ° / ₀ boron are present, namely based on the total weight of the reactants. Larger amounts can be used if necessary.

The complex compounds to be used can either be relatively easily identifiable substances or have such a complex structure that it is impossible to determine the molecular structure. The compound [(CH ₃ ) ₃ SiO] ₃ B provides e.g. B. represent an identifiable type of these complex compounds. In the more complex types, bonds, e.g. B.

i = or = BOSiOB =

= SiOSiOB =, = BOBOSi

appear. The free valences of substituents of the aforementioned type, be saturated, or they can be via oxygen atoms with other Si or B atoms. Under the reaction conditions of the benzene hydrocarbons with the polyhalomonohydrosilane it appears that the phenyl, methyl, alkoxy, chlorine or Hydrogen substituents of the Si-B complex compound migrate between the Si and B atoms. if therefore the starting composition of the complex compound is also known, it is among the ruling ones Reaction conditions impossible to determine in which position one of the aforementioned Substituents located. -

The complex compound used can either be formed in situ in the reaction mixture but it can also be added to the reaction mixture.

The complex compound can be produced by the action of a silane on a boron compound. Silanes suitable for this have the general formula R ' ₄ _a- * H _a SiX ₆ , in which each R' is a monovalent 5 & hydrocarbon radical, each X is alkoxy or chlorine, α is a number from 0 to 1, b is a number from 1 to 4 , where the sum of # and b is not greater than 4. Examples of suitable silanes are: SiCl ₄ , HSiCl ₃ , CH ₃ HSiCl ₂ , (CHa) ₂ Si (OC ₂ H ₅ ) Cl, (CH ₃ ), SiOC ₂ H ₅ , (CHg) ₃ SiCl, C ₆ H ₅ SiCl ₃ , C ₆ H ₅ CH ₃ SiCl ₂ or C ₆ H ₅ (CH ₃ ) ₂ SiCl. If alkoxy-substituted silanes are used, it is expedient for the alkoxy group to contain fewer than 5 carbon atoms.

The boron used for the preparation of the complex compound can be in the following forms: boric acid, boric anhydride, organic borates, e.g. B. tributyl borate, phenyl boric acid C ₆ H ₅ B (OH) ₂ , or diphenyl boric acid (C ₆ H _B ) ₂ BOH. The complex compounds can also be obtained by reacting a "suloxane or silanol with boron halides or organic boron compounds, for example phenylboron dichloride and diphenylboron chloride. If halosilanes are present, the complex compounds can also be formed from metallic boron or borohydrides."

When the complex compound is prepared in advance and added to the reaction mixture, the reaction between the silane and the boron compound is generally carried out at atmospheric pressure at or below the reflux temperature. It is expedient to use an excess of silanes, which serve as solvents for the complex compounds formed, although many of the complex compounds are liquid products. If B ₂ O _{3 is used} as the boron starting material and low-boiling silanes, e.g. B. SiCl ₄ and HSiCl ₃ , used as Süiciumausgangsstoffe, then in general expediently higher temperatures than the return temperature are used in order to obtain soluble complex compounds in a short reaction time. Correspondingly, overpressures can also be used in such a process in order to achieve higher temperatures for carrying out the reaction in the liquid phase.

If the complex compound is formed in situ in the reaction mixture, then the complex compound-forming silane is one of the silanes present in the reaction mixture. The boron used is. then expediently a compound of the general formula (R " _C O) ₃ B _{2. C} , in which R" is a substituent of the group of monovalent hydrocarbon radicals and hydrogen and c is a number between 0 and 1. For example, when benzene and silicon chloroform are reacted, boric acid can be added to the reaction mixture. The boric acid then reacts to form the complex compound with the silicon chloroform, which then acts as a catalyst in the reaction between the remaining silicon chloroform and the benzene.

Substances such as H ₃ BO ₃ and B ₂ O ₃ can be used in the formation of the complex catalyst on-site in a continuous or discontinuous process. However, they work better in the batch process than in the continuous process, which is due to the mechanical difficulties when solids are used in continuous high-pressure apparatus. In the continuous process, liquid organoborates or a solution of one of the preformed silicon boron complex compounds are therefore preferably used as the catalyst.

The Si-B complex compounds are formed in the _{reaction of benzene with sulfide chloroform, catalyzed by BCl 3} , if bonded oxygen is present in the form of water or siloxane oxygen. If such a reaction takes place under completely anhydrous conditions and in the absence of bound oxygen, then the entire

BCl _{3 can} be recovered as such. However, if moisture or any siloxane is present in the reaction vessel, the BCl ₃ reacts to form the Si-B complex compound. Under these conditions, metallic boron or boron hydrides or organic boron halides form similar complex compounds in the form of both distillable and non-distillable types, both of which are excellent catalysts for the process according to the invention. They can circulate as often as desired during the process, it being possible to _{compensate for catalyst losses by adding the required amount of B Cl 3} or another of the boron compounds mentioned.

The process of the invention is in a wide range of amounts of polyhalomonohydrosilane and Benzene hydrocarbon can be carried out in the reaction mixture. Due to economic considerations and of the law of mass action, it is expedient to use less than 20 mol of one of the starting materials on ι MbI of the other.

If appropriate, the process is based on the preparation of monosilyl derivatives of a benzene hydrocarbon directed, it is expedient to work with a slight excess of the hydrocarbon. Mixtures containing more than 1 mole equivalent of the silane per mole of hydrocarbon provide increased efficiency Yield of polysilyl derivatives of the hydrocarbon. That way you can by using Larger amounts of silanes increase the yield of di- and tri-alkyl hydrocarbons without significant Reduction in the yield of mono-oil hydrocarbons.

According to the invention, the starting materials are ^{heated to above 150 0} reaction temperature. At temperatures above 420 ⁰ , the advantages achieved through the use of catalysts do not apply. If the polyhalomonohydrosilane is a trichlorosilane, then the reaction temperature is expediently between 230 and 300 ⁰ . B. CH ₃ HSiCl ₂ , then the optimal reaction ^{temperature is between 150 and 250 0} .

A sufficiently high pressure should be used, so at least at the reaction temperatures part of the reaction mixture is in the liquid phase. The pressure can be on different Way to be generated; you can z. B. the starting materials continuously in the reaction zone under pressure conduct, or the process can be carried out under self-generating pressure in a closed system. The stated phase conditions are achieved when at least 1.2 g-mol of the starting materials are used per liter of the reaction space.

In the following examples, the subject of the invention is to be explained in more detail, without thereby the To limit the invention to this. In these examples the yield of percent final products is based on Amount of polyhalomonohydrosilanes consumed during the reaction and is calculated from the following equation:

% Yield =

Moles of product obtained

Moles of R "HSiCl _3. " Applied - moles of R _n HSiCl _{3 recovered}

R HSiCl _3. ,, which is neither recovered as such nor converted to the end product, is in the form of by-products to other halosilanes, e.g. B. R _n SiCl _4. ,,, and converted into di- or trisilyl hydrocarbons.

Example ι

In a comprehensive 14.41 autoclave a mixture of 1402 g of benzene, 2440 g of trichlorosilane and 39 g of boric acid is heated to an average temperature of 290 ⁰ for 16 hours. The highest pressure reached in the autoclave during the heating time is 71.5 at. The fractional distillation of the end product gives 1298 g of phenyltrichlorosilane, which corresponds to a yield of 40.8%.

Example 2

As in Example 1, a mixture of 1402 g of benzene, 2440 g of trichlorosilane and 39 g of B ₂ O _{3 is} heated to an average temperature of 294 ^° for 16 hours. The maximum pressure measured is 73.5 at. Fractional distillation of the reaction product gave 977 g of phenyltrichlorosilane, which corresponds to a yield of 37.5%.

Example 3

A mixture of 597 g (5.5 mol) of (CH _{3) 3} SiCl and 93 g (i, 5 mol) H ₃ BO ₃ is heated to 57-78 ⁰ refluxed for 40 hours. During this time, hydrochloric acid evaporates. During the last ι hour of refluxing, a constant temperature of 78 ^{0 is established} . The fractionation of the reaction product results in a yield of 260.8 g of the desired end product [(CH _{3) 3} SiO] ₃ B, which boils at 5 mm Hg at 47 ⁰ and 25 ⁰ having a nD of 1.3852. 468 g of benzene, 542 g of HSiCl ₃ and 25 g of the [(CH ₃ ) ₃ SiO] ₃ B thus obtained are placed in a 2.4 l autoclave. The autoclave is heated for 7 hours on the average temperature of 275 ^0th Fractionation of the end product gives a yield of 108 g of C ₆ H ₅ SiCl ₃ , which corresponds to 35.9%.

Example 4

A mixture of 624 g of benzene, 460 g of CH ₃ HSiCl ₂ and 27 g of the [(CHg) ₃ SiO] ₃ B obtained according to Example 3 is heated to 200 to 20 ° for 7 hours in a 2.4 l autoclave. The fractionation of the end product obtained in addition to not pressed in response CH ₃ HSiCl benzene and a 46 ° / ₀ yield of C ₆ H ₅ CH ₃ SiCl ₂ g in an amount of from 194th

Example 5

A mixture of 142 g of C ₆ H ₅ (CH ₃ ) ₂ SiCl and 15.5 g of H ₃ BO ₃ is heated to 150 to 160 ° for 16 hours. Vigorous evolution of HCl occurs. The liquid reaction product is placed under reduced pressure to remove the remaining dissolved HCl. A somewhat cloudy solution containing 3.45 percent B by weight is obtained. A mixture

47 g of this solution, 468 g of benzene and 542 g of H ₃ SiCl is heated in an autoclave for 7 hours from 2.4 to 1 to about 275 ^0th Fractionation gave 295 g of C ₆ H ₅ SiC] ₃ , which corresponds to a yield of 45.6%. 5

Example 6

50 g of the Si-B solution prepared according to Example 5,

552 g of toluene and 460 g of CH ₃ HSiCl ₂ are heated to about 180 ° for 16 hours in a 2.4-liter autoclave. Tolylmethyldichlorosilane is obtained.

Example 7

A mixture of 62 g H ₃ BO _{3 and} 345 g CH ₃ HSiCl ₂ is refluxed for 48 hours, with evolution of HCl. The analysis of the liquid decanted part of the reaction product shows a boron content of 1.8 percent by weight. One

ao mixture of 55 this solution, 624 g of benzene and 460 g CH ₃ HSiCl ₂ is heated in an autoclave 2.41 comprehensive for 7 hours at 200 ° to 210 ⁰ g. The fractionation of the reaction product gives 217 g · C ₆ H ₅ CH ₃ SiCl _2, corresponding to a yield of 35.2 ° / ₀

is equivalent to. '

Example 8

A mixture of C ₆ H ₅ SiCl ₃ and H ₃ BO ₃ is refluxed for 16 hours, with evolution of HCl. The liquid portion of the reaction product containing 0.98 weight percent boron. A mixture of 96 g of this liquid, 468 g of benzene and 542 g H SiCl ₃ are in a 2.4 1 comprehensive autoclave for 7 hours at about 275 ⁰ heated Fractionation of the reaction product yields 276 g of C ₆ H ₅ SiCl _3, which corresponds to a 46.4 ° / ₀ yield.

Example 9

If a mixture of 2776 g of diphenyl, 2440 g of .HSiCl ₃ and 400 g of the reaction product C ₆ H ₅ SiCl ₃ -H ₃ BO ₃ obtained according to the examples is heated to 300 ° for 16 hours in a 14.41-capacity autoclave, then two are obtained isomeric diphenyltrichlorosilanes. One is a liquid which boils from 200 to 202 ° at 30 mm Hg, and the other is a white crystalline mass which boils 205-207 ⁰ at 30 mm Hg.

Example 10

A mixture of 21 g of tributyl borate (C ₄ H ₉ O) ₃ B, 624 g of benzene and 460 g of CH ₃ HSiCl ₂ is heated to 200 to 210 ° for 7 hours in a 2.41 capacity autoclave. Fractionation of the reaction product gives 230 g of C ₆ H ₅ CH ₃ SiCl ₂ , which is a

45.8% yield corresponds.

Example ri

Several crystals of H ₃ BO ₃ are added to a mixture of 64.5 g (CHg) ₂ SiCl ₂ and 74 g (CH ₃ ) ₂ Si (OC ₂ H ₅ ) ₂ . An exchange reaction occurs immediately with the formation of (CHg) ₂ Si (OC ₂ H ₅ ) Cl. _{22 g of H 3} BO _{3 are} added to this reaction product, HCl develops. The mixture is heated at 75 ° until no more solid constituents are present. The remaining HCl is then evaporated off under vacuum. A clear solution is obtained which, when examined, contains 3.05 percent by weight boron and which consists mainly of the following compound: [(CH ₃ ) ₂ C _a H ₅ OSiO] ₃ B. A mixture of 33 g of this solution, 624 g of benzene and 460 g of CH ₃ HSiCl ₂ are heated to 200 to 210 ° for 7 hours in a 2.41 capacity autoclave. Fractionation of the reaction product gives 206 g of C ₆ H ₅ CH ₃ SiCl ₂ in 42.4% yield.

Example 12

A mixture of benzene and trichlorosilane in a molar ratio of 1.5: 1 and BCl ₃ , in an amount that makes up 0.5 percent by weight of the starting materials, is heated in the liquid phase to about 275 ° for 16 hours. The benzene used was contaminated with a small amount of an admixed organosiloxane. The reaction product is fractionated to separate unreacted HSiCl ₃ , benzene and C ₆ H ₅ SiCl ₃ . As soon as the C ₆ H ₅ SiCl _{3 is} almost completely removed, the distillation residue is found to contain 0.46 percent by weight boron. This residue is referred to as Catalyst A. The fractionation of part of this catalyst A is continued in order to obtain substances which boil _{above the C 6} H _{6 SiCl 3.} Two fractions enriched in boron are obtained. The first (catalyst B) boiling at 15 mm Hg between 80 to 90 °, has a density of 1.261 at 25 ⁰ and containing T., 03 percent by weight of B. The second fraction (catalyst C) boiling at 14 mm Hg 106-159 ⁰ , has a density of 1.325 at 25 ° and contains 1.02 percent by weight B. Three tests are carried out in an autoclave with a capacity of 2.41, in each of which the starting materials are 468 g benzene and 542 g HSiCl ₃ . The reaction time is 7 hours each time, the temperature is 275 ^° . The first run uses 202 grams of Catalyst A. Fractionation of the reaction product gives 247 g of C ₆ H ₅ SiCl ₃ , corresponding to a yield of 56.1%. In the second run, 60 g of catalyst B are used. The fractionation results in 382 g of C ₆ H ₅ SiCl _3, corresponding to 55.9 ° / ₀ exploits In the third run, 60 g of catalyst C are used. Fractionation gives 375 g xio C ₆ H ₅ SiCl ₃ , corresponding to a 54.8% yield.

Example 13

. A mixture of 468 g of benzene, 708 g of C ₆ H ₅ HSiCl ₂ and 60 g of catalyst B of Example 12 was heated in an autoclave 2.41 comprehensive 16 hours 200 ^0th Fractionation of the reaction product gives (C ₆ Hs) ₂ SiCl ₂ .

Example 14

A mixture of 380 g of naphthalene, 407 g of trichlorosilane and 20 g of the compound [(CH ₃ J ₃ SiO] ₃ B, according to Example 7 is heated for 16 hours in a 280 ⁰ 2.41 comprehensive autoclave. Fractionation

671

of the reaction product gives naphthyltrichlorosilane and dihydronaphthyltrichlorosilane.

Claims (1)

PATENT CLAIM: Process for the preparation of aromatic halosilanes, characterized in that optionally substituted benzene hydrocarbons with a polyhalogenmonohydrosilane in the presence of a silicon-boron complex compound in which some, but only some of the valences of Si and B are replaced by substituents from the group: phenyl, methyl, Alkoxy, halogen or hydrogen are saturated and all remaining valences are connected by oxygen atoms with Si and B atoms of the complex compound, continuously or discontinuously at a reaction temperature above 150 ⁰ and below 420 ° at such a pressure that at least part of the The reaction mixture is in the liquid phase, the benzene hydrocarbons used being free of unsaturated aliphatic side chains and the polyhalogenmonohydrosilanes used _{corresponding to the general formula R n} H SiQ _3. "(R monovalent hydrocarbon radicals; η a number from obisi). ι 5Ϋ98 3.53