EP0000614B1

EP0000614B1 - Production of dichlorosilane derivatives

Info

Publication number: EP0000614B1
Application number: EP19780300045
Authority: EP
Inventors: Isao Koga; Yohji Terui; Masuhito Ohgushi; Tohru Kitahara
Original assignee: Chisso Corp
Current assignee: JNC Corp
Priority date: 1977-06-17
Filing date: 1978-06-14
Publication date: 1981-11-25
Also published as: DE2861341D1; EP0000614A1

Description

The present invention relates to the production of dichlorosilane derivatives.
Diorganodichlorisilanes are very important compounds in the silicone resin industry but only relatively few compounds such as dimethyldichlorosilane and diphenyldichlorosilane are actually used on an industrial scale. With recent developments in the silicone resin industry, it has become appreciated that other diorganodichlorosilanes might be desirable.
In accordance with the present invention we provide a process for preparing substituted phenethyldichlorisilanes represented by the general formula
wherein R is an alkyl group having 3-20 carbon atoms or is a A-phenethyl group.
The novel process in accordance with the invention involves reacting an appropriately mono- substituted dichlorosilane with styrene using as catalyst a complex of platinum and a phosphine.
The dichlorosilane derivatives prepared by process of the invention are novel substituted phenethyldichlorosilanes.
Ethylphenethyldichlorosilane is itself a compound known for example from Chemical Abstracts, Vol 54, 22435 and French Patent Specification No. 1,169,051. As the French Specification describes, ethyl-β-phenethyldichlorosilane can be prepared in 75.5% yield by heating ethyldichlorosilane with styrene in the presence of a particular catalyst, namely a platinum/gamma-alumina catalyst. This catalyst is said not to be prone to catalyst fatigue, as were other catalysts known for the addition of hydrogensilanes to unsaturated hydrocarbons.
Platinum on alumina is also amongst the catalysts mentioned in US Patent No. 2,954,390 for use in preparing β-phenethylchlorosilane, the US and French Patents being approximately cotemporaneous documents. The US Patent mentions that in the then known additions of methyldichlorosilane to styrene, a mixture of α-phenethyl and β-phenethyl substituted methyldichlorosilanes was obtained unless a platinum-on-charcoal catalyst was used.
Proceeding from this standpoint, the US Patent No. 2,954,390 puts forward the use of tetrahydrofuran or related solvents as the key to producing the A-isomer in preference to the a-isomer, thereby obviating the need to use a platinum-on-charcoal catalyst. The various examples in the US Patent all describe only the addition of methyldichlorosilane to styrene, and moreover there is no mention of the catalysts now employed in the present process.
Later literature such as German Auslegeschrift No. 1,492,798 has taught that the platinum- catalysed additions of hydrogensilanes to unsaturated hydrocarbons are relatively inefficient since the known platinum catalysts have only poor activity. Better catalysts are said to be certain complexes of palladium.
In common with the other literature, this Auslegeschrift does not disclose the use of its catalysts for the addition of styrene to monosubstituted dichlorosilanes RHSiCI₂ wherein R is an alkyl group having 3-20 carbon atoms or is a A-phenethyl group.
Contrary to the teaching of the prior art, we have now found that certain monosubstituted dichlorosilanes will react efficiently with styrene in the presence of a catalyst which is a complex of platinum and a phosphine. Such a reaction readily gives a high yield of the corresponding β-phenethyl substituted silane, and in this way we have been able to prepare the novel compounds of formula (I).
More particularly, the novel compounds which can be prepared by our process include alkylphen- ethyldichlorosilanes represented by the general formula
wherein R' is an alkyl group having 3-20 carbon atoms.
Concrete examples of compounds of the formula (II) are propylphenethyldichlorosilane, iso- propylphenethyldichlorosilane, butylphenethyldichlorosilane, isobutylphenethyldichlorosilane, pentyl- phenethyldichlorosilane, isoamylphenethyidichlorosilane, hexylphenethyldichlorosilane, heptylphen- ethyldichlorosilane, octylphenethyldichlorosilane, nonylphenethyldichlorosilane, decylphenethyldi- chlorosilane, undecylphenethyldichlorosilane, dodecylphenethyldichlorosilane, tridecylphenethyldi- chlorosilane, tetradecylphenethyldichlorosilane, hexadecylphenethyldichlorosilane, octadecylphen- ethyldichlorosilane and eicosylphenethyldichlorosilane.
The novel compounds from our process also include diphenethyldichlorosilane represented by the formula:
The method we provide for producing the compounds of formula (I) comprises reacting at a temperature of 30 to 200°C a monosubstituted dichlorosilane having the general formula RHSiCI₂, where R is as defined above, with styrene in the presence of a complex of platinum and a phosphine.
Where R in the monosubstituted dichlorosilane is an alkyl group having 3 to 20 carbon atoms it is preferred that the reaction with styrene is effected at 30 to 1 10°C. The reaction time is not critical but is usually 1 to 60 hours. The required starting material, a monoalkyldichlorosilane of formula RHSiCI₂, R' being as defined above, is preferably prepared by the addition reaction with dichlorosilane itself of an α-olefin having 3 to 20 carbon atoms. For example such a starting material can be obtained by reacting dichlorosilane and an a-olefin having 3 to 20 carbon atoms in the presence of a complex of a phosphine compound and a transition metal of group 8 at a temperature of 30 to 200°C. Conveniently the reaction is carried out for 1 to 60 hours at atmospheric or greater pressure. Where the transition metal is other than platinum the reaction is preferably effected at 50 to 200°C and the catalyst then separated off before the subsequent reaction with styrene. On the other hand, where the transition metal is platinum then the preferred reaction temperature is 30 to 110°C. Furthermore, the complex need not be separated off but can be retained in the liquid as the catalyst for the subsequent reaction with styrene.
Where R in the monosubstituted dichlorosilane is phenethyl, the required starting material, monophenethyldichlorosilane, can be obtained by reacting dichlorosilane with an equimolar or excess amount of styrene in the presence of a complex of a transition metal of group 8 and a phosphine. Examples of such complexes include chlorotris(triphenylphosphine)rhodium(l), [RhCI(PPh₃)_3] and tetra- kis(triphenylphosphine)platinum(0), [Pt(PPh₃)₄]. Suitably the reaction is effected at 30 to 200°C, and when the complex is a platinum complex then it is usually found that monophenethyldichlorosilane alone is obtained if the molar ratio of styrene to dichlorosilane is 1 or less, and that diphenethyldichlorosilane is also produced if styrene is present in molar excess. Such reactions may be represented by the following equations (1) and (2):
In other words, diphenethyldichlorosilane can be produced by reacting dichlorosilane with 2 or more molar equivalents of styrene or by reacting monophenethyldichlorosilane with 1 or more equivalents of styrene, the reaction being effected in the presence of a complex of platinum and a phosphine compound at 30 to 200°C. The preferred reaction time is 0.5 to 60 hours.
The complex of platinum and a phosphine compound employed in the methods of the present invention acts as a catalyst and is preferably tetrakis(triphenylphosphine)platinum(O). The preferred concentration of complex is 1 to 10-¹⁵, preferably 1 to 10-⁸, mol percent per silicon atom.
The production of the substituted phenethyldichlorosilanes can be carried out as a batch, flow- method or half-batch procedure. For example, diphenethyldichlorosilane can be produced by a method in which liquefied dichlorosilane, styrene and the catalytic complex are charged into a sealed reactor, reacted by heating under pressure, and distilling off the product after reaction. Other methods include those in which dichlorosilane is flowed into a reaction vessel containing styrene and a catalytic liquid, or in which styrene and dichlorosilane are counter-flowed through a fixed bed supporting a catalyst on a carrier.
A characteristic feature of the methods described is the use of dichlorosilane and/or a mono- substituted dichlorosilane as starting material for production of the substituted phenethyldichlorosilanes. In such methods it is to be noted that the hydrogen directly joined to the silicon of dichlorosilane or of the mono-substituted dichlorosilane adds only to the opposition of styrene to form the product. It is of great advantage that the isomer in which the above mentioned hydrogen adds to the 13- position of styrene is not formed. Moreover we have found that other by-products are not obtained and that the desired substituted phenethyldichlorosilanes are typically formed in an extremely high yield.
The compounds (I) are novel compounds which can be polymerized using conventional methods to produce polysiloxanes. As is well known the polymerization involves hydrolysis to give initially the corresponding hydroxy compounds which then readily undergo inter- and intra-molecular condensation. The polysiloxanes obtained using the substituted phenethyldichlorosilanes of formula (I) have improved heat-resistance and other desirable characteristics. The compounds of formula (I) can thus be used for improving the heat-resisting and other properties of silicone oils, rubbers and varnishes which are used as electrical insulating materials, lubricating oils, water-repelling agents, paints, release agents and other known uses.
The present invention will now be illustrated by the following non-limiting specific Examples; comparative examples are also given. In the examples reference is made to the accompanying drawings, in which:

Figures 1 and 2 are respectively the infrared (ir) and nuclear magnetic resonance (nmr) spectra of n-hexylphenethyldichlorosilane produced in Example 1;
Figures 3 and 4 are respectively the ir and nmr spectra of n-dodecylphenethyldichlorosilane produced in Example 2; and
Figures 5 and 6 are respectively the ir and nmr spectra of diphenethyldichlorosilane produced in Example 4.

Example 1

3.80 g (20.5 millimol) of n-hexyldichlorosilane, 2.00 g (19.2 millimol) of styrene, and 0.023 g (1.92 x 10-⁵ mol) of tetrakis(triphenylphosphine)platinum(0) were introduced into a flask and reacted with stirring by heating in an oil bath at 60°C for 8 hours. Distillation under reduced pressure of the reacted mixture produced 5.6 g (17.5 millimol) of a product shown to be n-hexylphenethyldichlorosilane, (n-C₆H₁₃) (C₆H₅CH₂CH₂)SiCl₂.
The n-hexylphenethyldichlorosilane had a boiling point of 120 to 123°C/1 mmHg and an n²⁰ of 1.5009. The elemental analysis was as follows:-

found: C: 57.87%, H: 7.57%, Cl: 23.5%;
theoretical: C: 58.12%, H: 7.66%, Cl: 24.51%.

Comparative Example 1

Reaction was carried out as in Example 1 except that an isopropanol solution of H₂PtCl₆.6H₂O was substituted for the tetrakis(triphenylphosphine)platinum(O). A resinous product formed and no n-hexylphenethyldichlorosilane could be obtained.

Example 2

Reaction was carried out as in Example 1 except that n-dodecyldichlorosilane was substituted for the n-hexyldichlorosilane, whereby a product shown to be n-dodecylphenethyldichlorosilane (n-C₁₂H₂₅) (C₆H₅CH₂CH₂)SiCl₂, was obtained.
The boiling point of the product was 165.2 to 168.0°C/2mmHg. The ir spectrum of this product was as shown in Figure 3 and the nmr spectrum was as shown in Figure 4.

Example 3

0.89 mol of 1-hexane, 0.08 mol % (relative to dichlorosilane introduced later) of catalyst, tetra- kis(triphenylphosphine)platinum(O), were introduced into a 500 ml pressure-proof stainless steel reactor which was sealed and then cooled with a dry-ice-methanol bath. After introduction into the reactor of 0.64 mol of dichlorosilane through an inlet pipe, the reactor was sealed and reaction was carried out by heating in an oil bath at 100°C for 2 hours with stirring. The reacted liquid was transferred to a flask, 0.64 mol of styrene was added and further reaction was carried out with stirring at 80°C for 4 hours. After the reaction, distillation was carried out under reduced pressure to obtain 0.58 mol of n-hexylphenethyldichlorosilane having a boiling point of 120 to 123°C/1 mmHg.

Example 4

25.6 g (254 millimol) of dichlorosilane, 52.3 g (502 millimol) of styrene and 0.295 g (0.237 millimol) of tetrakis(triphenylphosphine)platinum(O) were charged into a 200 ml pressure-proof stainless steel reaction tube as in the procedure Example 3, then heated in an oil bath at 150°C for 16 hours with stirring. Distillation of the reacted liquid under reduced pressure gave 36.0 g of a product shown to be diphenethyldichlorosilane, (C₆H₅CH₂CH₂)₂SiCl₂.
The diphenethyldichlorosilane had a boiling point of 140 to 151°C/1.0mmHg. The ir spectrum was as shown in Figure 5. Absorptions are observed for aromatic C-H stretch at 3000 to 3100 cm^-1 and for deformation of a C-H directly connected to Si at 1260 cm-', but no characteristic absorption is seen for Si-H in the neighbourhood of 2100-'. The nmr spectrum was as shown in Figure 6. Referring to the δ scale (ppm), there is no signal corresponding to Si-H at 3.0 to 5.0, but signals are seen at 0.99 (corresponding to Si-CH₂-) at 2.72 (-CH₂-CH₂-C₆H₅) and at 7.12 (C₆H₅-). The integration for these signals was in the ratio 4:4:10. In the mass spectra, a parent ion M⁺ 308 was observed.
A polysiloxane was then prepared in a conventional manner using the diphenethyldichlorosilane as obtained in this Example. Initial hydrolysis at 60°C give a product of average molecular weight 860 which was shown by ir to include cyclic components formed by intramolecular condensation. This initial product had a refractive index (25°C, D) of 1.570 and a kinetic velocity (25°C) of 280 centistokes. Further reaction at 80°C of 94 g of the product with 3 g of hexamethyldisiloxane in the presence of 1 ml of 10% aqueous tetramethylammonium hydroxide gave a polysiloxane of average molecular weight 3800.
The polysiloxane had the following physical characteristics:

Comparative Example 2

30.0 g (300 millimol) of dichlorosilane, 56.5 g (543 millimol) of styrene and 50 ml of an isopropanol solution of chloroplatinic acid (H₂PtCl₆.6H₂O) containing 4.83 x 10^-6mol of the acid were charged into a 200 ml pressure-proof stainless steel reaction tube and reaction was carried out as in the procedure of Example 3 by heating in an oil bath at 50°C for 15 hours with stirring. After reaction, the reacted liquid resinified and no diphenethyldichlorosilane could be obtained.

Comparative Example 3

31.7 g (314 millimol) of dichlorosilane, 56.3 g (541 millimol) of styrene and 0.2182 g (2.36 x 10-⁴ mol) of chlorotris(triphenylphosphine)rhodium(l) were charged into a 200 ml pressure-proof stainless steel reaction tube as in the procedure of Example 3 and reaction was carried out by heating in an oil bath at 150°C for 20 hours with stirring.
After reaction, the reacted liquid was distilled under a reduced pressure. 45.7 g (223 millimol) of a product found to be monophenethyldichlorosilane was obtained, but no diphenethyldichlorosilane was identified in the distillate.

Example 5

Following the procedure of Example 3, 73.2 g (725 millimol) of dichlorosilane, and 92.7 g (890 millimol) of styrene were reacted in the presence of 0.1164 g (1.68 x 10-⁴ mol) of chlorotris(triphenylphosphine) rhodium (I) at 100°C for 16 hours and then the reacted liquid was distilled to obtain 147.6 g of monophenethyldichlorosilane (b.p. 95°C/7 mmHg).
10.3 g (50 millimol) of the monophenethyldichlorosilane, 22.7 g (218 millimol) of styrene and 0.08 g (6.42 x 10-⁵ mol) of tetrakis(triphenyiphosphine)piatinum(0) were charged into a 100 ml stainless steel reaction tube and reacted by heating in an oil bath at 100°C for 15 hours with stirring. After reaction, the reacted liquid was distilled under reduced pressure to obtain 13.6 g of a product having a boiling point of 141 °C/1.5mmHg and having the same ir, nmr and mass spectra as the product of Example 4. It was thus confirmed that the product produced by the present example was diphenethyldichlorosilane.

Claims

1. A method for producing a substituted phenethyldichlorosilane having the general formula

wherein R is an alkyl having 3 to 20 carbon atoms or a β-phenethyl group, which comprises reacting at a temperature of 30 to 200°C a monosubstituted dichlorosilane having the general formula RHSiCI₂, where R is as defined, with styrene in the presence of a complex of platinum and a phosphine.

2. A method according to Claim 1 wherein the complex is tetrakis(triphenylphosphine)platinum-(0).

3. A method according to Claim 1 or Claim 2 wherein R is an alkyl group having 3 to 20 carbon atoms and the reaction with styrene is effected at 30 to 110°C.

4. A method according to Claim 1 or Claim 2 wherein R is phenethyl.

5. A method according to any one of Claims 1 to 4, wherein the monosubstituted dichlorosilane RHSiCI₂ is prepared by reacting at a temperature of 30 to 200°C dichlorosilane itself with, as may be appropriate, an α-olefin having 3 to 20 carbon atoms or styrene, in the presence of a complex of platinum and a phosphine.

6. A method according to Claim 5 wherein the complex employed for reaction of the dichlorosilane itself is also employed for reaction of the monosubstituted dichlorosilane produced.

7. A method according to Claim 6 wherein when R is A-phenethyl, dichlorosilane itself is reacted with 2 or more molar equivalents of styrene to give diphenethyldichlorosilane.