Process for preparing higher halosilanes and hydridosilanes

Abstract

The invention relates to a process for preparing higher halosilanes by disproportionation of lower halosilanes. The invention further relates to a process for preparing higher hydridosilanes from the higher halosilanes prepared by disproportionation. The invention further relates to mixtures containing at least one higher halosilane or at least one higher hydridosilane prepared by the process described. Finally, the invention relates to the use of such a mixture containing at least one higher hydridosilane for producing electronic or optoelectronic component layers or for producing silicon-containing layers.

Claims

1. A process for preparing a higher halosilane, the process comprising: converting at least one halosilane of formula:
Si.sub.nX.sub.2n+2, by disproportionation to a product mixture comprising at least one higher halosilane of formula:
Si.sub.mX.sub.2m+2, and at least one lower halosilane of formula:
Si.sub.aX.sub.2a+2, wherein n is equal to or larger than 2; m is larger than n; a is 1 or 2; and X is F, Cl, Br, I, or a combination thereof, and wherein a reaction is catalysed by at least one tertiary phosphine, wherein the at least one halosilane is selected from the group consisting of Si.sub.2X.sub.6, Si.sub.3X.sub.8, and Si.sub.4X.sub.10.

2. The process according to claim 1, wherein the at least one tertiary phosphine is at least one selected from the group consisting of a tertiary alkylphosphine, a tertiary arylphosphine, and a tertiary bidentate phosphine.

3. The process according to claim 2, wherein the at least one tertiary phosphine is at least one selected from the group consisting of trimethylphosphine, triethylphosphine, and triphenylphosphine.

4. The process according to claim 1, wherein the at least one halosilane is a linear silane.

5. The process according to claim 1, further comprising: hydrogenating the at least one higher halosilane, thereby obtaining the at least one higher hydridosilane of formula Si.sub.mH.sub.2m+2.

6. The process according to claim 5, further comprising: removing the at least one lower halosilane from the product mixture prior to the hydrogenating.

7. The process according to claim 5, wherein the hydrogenating is effected by adding at least one hydrogenating agent selected from the group consisting of a metal hydride of a metal of main groups 1 to 3 and a hydridic compound comprising LiAlH.sub.4, NaBH.sub.4, or iBu.sub.2AlH.

8. The process according to claim 7, wherein the hydrogenating agent is present in a 2- to 30-fold molar excess of the at least one halosilane added.

9. The process according to claim 6, wherein the removing is distillative removing or drawing off at a temperature of from −30 to +100° C. and a pressure of from 0.01 to 1013 mbar prior to the hydrogenating.

10. The process according to claim 8, wherein the hydrogenating agent is present in a 10- to 15-fold molar excess of the at least one halosilane added.

11. A method for producing at least one higher halosilane, comprising: producing the at least one higher halosilane with at least one tertiary phosphine.

12. The method according to claim 11, wherein the at least one tertiary phosphine is at least one selected from the group consisting of a tertiary alkylphosphine, a tertiary arylphosphine, and a tertiary bidentate phosphine.

13. The process according to claim 1, which is conducted at room temperature.

Description

EXAMPLES

Example 1

(1) Disproportionation: 10.2 g (0.028 mol) of octachlorotrisilane were admixed at room temperature, while stirring, 16.3 mg (2.1×10.sup.−4 mol; 0.75 mol %) of trimethylphosphine PMe.sub.3 in 0.2 ml of diethyl ether. After stirring at room temperature overnight and removal of the volatile constituents (diethyl ether, Si.sub.2Cl.sub.6, SiCl.sub.4) from the resulting clear solution at 40° C. under reduced pressure (0.05 mbar), the product remains as an oily liquid which was identifiable by means of .sup.29Si NMR spectroscopy as a mixture of oligochlorosilanes of different chain length. Yield: 5.3 g.

(2) Hydrogenation: 5.3 g of the resulting oligochlorosilane mixture were dissolved in 70 ml of toluene and admixed, while cooling with ice, gradually with 30 ml of a 2.1M solution of LiAlH.sub.4 in diethyl ether. Subsequently, the mixture was stirred at room temperature overnight. The reaction mixture was worked up with 150 ml of degassed 10% H.sub.2SO.sub.4 and the organic phase was dried with Na.sub.2SO.sub.4. After removal of the volatile constituents from the resulting clear solution at 40° C. under reduced pressure (0.05 mbar), the product remains as an oily liquid, which was identifiable by means of .sup.1H and .sup.29Si NMR spectroscopy as a mixture of higher hydridosilanes of different chain length. An analysis of the resulting product by means of GPC gave the following results: Mn=450 g/mol; Mw=580 g/mol; Mw/Mn=1.289. Yield: 0.8 g.