METHOF FOR PRODUCING HYDRIDOSILANES

Abstract

The invention relates to a method for producing hydridosilanes, in which siloxanes containing SiH groups are reacted in the presence of a cationic Si(II) compound as a catalyst.

Claims

1. A method for preparing hydridosilanes, comprising: reacting siloxanes comprising SiH groups in the presence of a cationic Si(II) compound as a catalyst.

2. The method of claim 1, wherein the siloxanes comprising SiH groups have the general formula I
R.sup.1R.sup.2HSiO.sub.(1/2)Z(I), wherein Z signifies the general formula Ia
(SiO.sub.4/2).sub.a(R.sup.xSiO.sub.3/2).sub.b(R.sup.x.sub.2SiO.sub.2/2).sub.e(R.sup.x.sub.3SiO.sub.1/2).sub.d(Ia) R.sup.1 and R.sup.2 are each independently hydrocarbon radicals, halogen atoms or hydrogen atoms, R.sup.x are each independently hydrogen, halogen, an unbranched, branched, linear, acyclic or cyclic, saturated or mono- or polyunsaturated C1-C20 hydrocarbon radical or an unbranched, branched, linear or cyclic, saturated or mono- or polyunsaturated C1-C20 hydrocarbonoxy radical, wherein in each case individual non-adjacent CH.sub.2 groups can be replaced by oxygen or sulfur atoms and individual CH groups can be replaced by nitrogen atoms and in each case the carbon atoms may bear halogen substituents, and a, b, c and d are each independently in each case integer values from 1 to 10,000, wherein the sum total of a, b, c and d together has at least the value 1.

3. The method of claim 2, wherein R.sup.1 and R.sup.2 are radicals and are each independently hydrogen, chlorine, linear saturated C1-C10 radicals, cyclic saturated or mono- or polyunsaturated C1-C10 hydrocarbon radicals.

4. The method of claim 2, wherein the radicals R.sup.x are selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, butyl, phenyl, benzyl, methoxy, ethoxy, n-propoxy and isopropoxy.

5. The method of claim 2, wherein the sum total of a, b, c and d is 1 to 10.

6. The method of claim 2, wherein the cationic Si(II) compound of the general formula III
([Si(II)Cp].sup.+).sub.aX.sup.a(III) is used, wherein Cp is a -bonded cyclopentadienyl radical of the general formula IV, which is substituted by the radicals R.sup.y, ##STR00004## R.sup.y are monovalent radicals or polyvalent radicals, which can also be bonded to one another to form fused rings, X.sup.a is an a valent anion, which does not react with the cationic silicon (II) compound center under the reaction conditions and a has integer values from 1 to 6.

7. The method of claim 6, wherein R.sup.y is each independently hydrogen, linear or branched, acyclic or cyclic, saturated or mono- or polyunsaturated C1-C20 alkyl or aryl.

8. The method of claim 6, wherein a has the value 1.

9. The method of claim 8, in which X.sup. is selected from halogen, BF.sub.4.sup., ClO.sub.4.sup., AlZ.sub.4.sup., MF.sub.6.sup. where Z=halogen and M=P, As or Sb, tetraaryl borate anion, wherein the aryl radical is phenyl or fluorinated phenyl or phenyl substituted by perfluoroalkyl radicals, carborate anion, alkoxymetallate ion and aryloxymetallate ion.

10. The method of claim 8, wherein the proportion by weight of the cationic Si(II) compound, based on the total mass of siloxanes comprising SiH groups, is 10.sup.5% by weight (0.1 ppm) to 5% by weight.

Description

EXAMPLES

[0058] Unless stated otherwise in each case, all amounts and percentages are based on weight and all temperatures are 20 C.

[0059] Gas chromatograms were recorded using a Model A6890 plus gas chromatograph from Agilent. Column used: HP-5, No. U.S. Pat. No. 2,441,516H, 30 m, 0.32 mm, 0.25 m, temperature: 40 C.-120 C. at 5 C./min.; from 120 C. to 300 C. at 10 C./min.; injector: 290 C., split 1:250, 1.0 l, carrier gas He 1.5 ml/min.; detector: FID, 320 C. The products were identified by comparison with authentic material.

[0060] In the following examples, the conversion was determined in each case by .sup.1H-NMR spectroscopy. For this purpose, the integral of the hydrogens of the silanes formed (dimethylsilane at =3.8 and trimethylsilane at =4.0) and the total integral of all hydrogens on siloxane moieties at =4.7-4.8 were determined and the conversion was calculated according to the following equation.

Conversion (%)=100I(silanes)/[I(siloxanes)I(silanes)]

Example 1: Disproportionation of 1,1,1,2,2-pentamethyldisiloxane in the Presence of (-Me.SUB.5.C.SUB.5.)Si.SUP.+.B(C.SUB.6.F.SUB.5.).SUB.4..SUP.

[0061] All working steps were conducted under Ar.

[0062] 296 mg (2.00 mmol) of pentamethyldisiloxane were dissolved in 1.0 ml of d.sub.2-dichloromethane and a solution of 1.8 mg (0.0021 mmol, 0.11 mol %) of (-Me.sub.5C.sub.5)Si.sup.+B(C.sub.6F.sub.5).sub.4.sup. was added at 20 C. The reaction was monitored by NMR spectroscopy. After 45 minutes, the reactant pentamethyldisiloxane was no longer detectable by NMR spectroscopy and the NMR shows the formation of higher molecular weight siloxanes comprising H groups. The silanes dimethylsilane and trimethylsilane were formed in the molar ratio of 70:30

Conversion=95%.

Example 2: Disproportionation of 1,1,2,2-tetramethyldisiloxane in the Presence of (-Me.SUB.5.C.SUB.5.)Si.SUP.+.B(C.SUB.6.F.SUB.5.).SUB.4..SUP.

[0063] All working steps were conducted under Ar.

[0064] 269 mg (2.00 mmol) of tetramethyldisiloxane were dissolved in 1.5 ml of d.sub.2-dichloromethane and 1.9 mg (0.00226 mmol, 0.11 mol %) of (-Me.sub.5C.sub.5)Si.sup.+B(C.sub.6F.sub.5).sub.4.sup. were added at room temperature (ca. 23 C.) with shaking. The reaction was stopped with pyridine after 30 minutes and the reaction mixture was investigated by NMR spectroscopy. The silane formed was exclusively dimethylsilane.

Conversion=70%

[0065] The other products were determined by gas chromatography.

[0066] The following products were detected by comparison with authentic material (retention times and area % in parentheses)dimethylsilane was not detected in this case: 1,1,2,2-tetramethyldisiloxane (2.14 min., 15%), pyridine (3.24 min., 41%), 1,1,2,2,3,3-hexamethyltrisiloxane (3.95 min., 8.6%), 1,1,2,2,3,3,4,4-octamethyltetrasiloxane (7.99 min., 1.5%), 1,1,2,2,3,3,4,4,5,5-decamethylpentasiloxane (12.85 min., 8.6%), 1,1,2,2,3,3,4,4,5,5,6,6-dodecamethylhexasiloxane (17.23 min., 7.0%), 1,1,2,2,3,3,4,4,5,5,6,6,7,7-tetradecamethylheptasiloxane (20.08 min., 5.1%), 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-hexadecamethyloctasiloxane (22.16 min., 3.3%).

[0067] Siloxane cycles were not detected by gas chromatography.

Example 3: Disproportionation of 1,1,2,2-tetramethyldisiloxane in the Presence of (-Me.SUB.5.C.SUB.5.)Si.SUP.+.HB(C.SUB.6.F.SUB.5.).SUB.3..SUP.

[0068] All working steps were conducted under Ar.

[0069] 269 mg (2.00 mmol) of tetramethyldisiloxane were dissolved in 1.5 ml of d.sub.2-dichloromethane and 1.4 mg (0.00207 mmol, 0.10 mol %) of (-Me.sub.5C.sub.5)Si.sup.+HB(C.sub.6F.sub.5).sub.3.sup. were added at room temperature (ca. 23 C.) with shaking. The reaction was stopped with pyridine after 30 minutes and the reaction mixture was investigated by NMR spectroscopy. The silane formed was exclusively dimethylsilane.

Conversion=45%

[0070] Siloxane cycles were not detected by gas chromatography.

Example 4 (Non-Inventive, Formation of Siloxane Cycles): Disproportionation of 1,1,2,2-tetramethyldisiloxane in the Presence of B(C.SUB.6.F.SUB.5.).SUB.3

[0071] 268 mg (2.00 mmol) of tetramethyldisiloxane were dissolved in 1.5 ml of d.sub.2-dichloromethane and 1.1 mg (0.00215 mmol, 0.11 mol %) of B(C.sub.6F.sub.5).sub.3 were added at room temperature (ca. 23 C.) with shaking. The reaction was stopped with pyridine after 30 minutes and the reaction mixture was investigated by NMR spectroscopy. The silane formed was exclusively dimethylsilane.

Conversion=65%

[0072] The other products were determined by gas chromatography-dimethylsilane was not detected in this case. The following products were detected by comparison with authentic material (retention times and area % in parentheses): pyridine (3.20 min., 22%), 1,1,2,2,3,3-hexamethyltrisiloxane (3.92 min., 11.8%), hexamethylcyclotrisiloxane (4.27 min., 0.8%), 1,1,2,2,3,3,4,4-octamethyltetrasiloxane (7.97 min., 0.6%), octamethylcyclopentasiloxane (8.26 min., 10.0%), decamethylcyclopentasiloxane (12.49 min., 0.9%), 1,1,2,2,3,3,4,4,5,5-decamethylpentasiloxane (12.80 min., 1.0%), 1,1,2,2,3,3,4,4,5,5,6,6-dodecamethylhexasiloxane (17.21 min., 7.0%), tetradecamethylcycloheptasiloxane (20.03 min., 7.3%).

Example 5 (Non-Inventive, Detection of Decomposition Product of the Lewis-Acidic Boron Catalyst)

[0073] All working steps were conducted under Ar. 268 mg (2.00 mmol) of tetramethyldisiloxane are dissolved in 1.5 ml of d.sub.2-dichloromethane and 1.1 mg (0.00215 mmol, 0.1 mol %) of tris(pentafluorophenyl)boron were added. Dimethylsilane was formed. In the .sup.19F-NMR spectrum, the formation of several fluorine-containing by-products was identified. After a reaction time of one hour, the formation of dimethyl(pentafluorophenyl)silane (M.sup.+=225) was detected by GC/MS analysis. The relative area percent in the GC was 0.2%.