Tetrakis(trichlorosilyl)germane, process for the preparation thereof and use thereof

Abstract

A novel process provides for the preparation of the chlorinated, uncharged substance tetrakis(trichlorosilyl)germane, and for the use thereof.

Claims

1. A process for preparing a tetrakis(trichlorosilyl)germane of the formula (I), ##STR00003## the process comprising: (a) mixing at least one tris(trichlorosilyl)germanide salt of a formula [X][Ge(SiCl.sub.3).sub.3], wherein X=ammonium (R.sub.4N) and/or phosphonium (R.sub.4P), and wherein R=alkyl[[ic]] radical or aromatic radical, with AlCl.sub.3, thereby obtaining a mixture, and (b) reacting the mixture in an environment comprising at least one chlorinated hydrocarbon at a temperature of 5 to 40° C. to obtain a crude product comprising at least one salt [R.sub.4N][AlCl.sub.4] and/or [R.sub.4P][AlCl.sub.4] and tetrakis(trichlorosilyl)germane, and subsequently (c) introducing said crude product into at least one nonpolar solvent and separating off an insoluble residue, and subsequently (d) removing the nonpolar solvent, to obtain tetrakis(trichlorosilyl)germane.

2. The process according to claim 1, wherein in step (b) the reaction is conducted at room temperature, and/or in step (d) the nonpolar solvent is removed at room temperature.

3. The process according to claim 1, wherein, in step (b), the chlorinated hydrocarbon is dichloromethane (CH.sub.2Cl.sub.2).

4. The process according to claim 1, wherein in step (c), the at least one nonpolar solvent is selected from the group consisting of hexane, n-hexane, pentane, and benzene.

5. The process according to claim 1, wherein in step (a), the mixing of [X][Ge(SiCl.sub.3).sub.3] and AlCl.sub.3 comprises stirring, and in step (b), the mixture obtained in step (a) is dissolved completely in the at least one chlorinated hydrocarbon, and, after a time of 0.1 to 24 hours, the at least one chlorinated hydrocarbon is removed.

6. The process according to claim 1, wherein in step (c), after the introducing of the crude product, the temperature of the at least one nonpolar solvent is brought 1 to 5 times from room temperature to above room temperature, and subsequently the at least one nonpolar solvent is allowed to cool.

7. The process according to claim 1, further comprising: depositing at least one Si—Ge layer with the tetrakis(trichlorosilyl)germane as precursor.

8. A Si—Ge layer deposition process, comprising: depositing at least one Si—Ge layer with, as a precursor, a tetrakis(trichlorosilyl)germane obtained by the process according to claim 1.

9. The process according to claim 1, wherein in step (c), the at least one nonpolar solvent comprises n-hexane.

10. The process according to claim 1, wherein in step (a), the mixing of [X][Ge(SiCl.sub.3).sub.3] and AlCl.sub.3 comprises stirring [X][Ge(SiCl.sub.3).sub.3] and AlCl.sub.3 in a solid state, in an oxygen-free environment under nitrogen or argon in a glovebox, and in step (b), the mixture obtained in step (a) is dissolved completely in the at least one chlorinated hydrocarbon, and, after a time of 1 to 5 hours, the at least one chlorinated hydrocarbon is removed at room temperature, in an oxygen-free, dry, environment, under standard pressure or under a reduced pressure of from 1 to 500 hPa.

11. The process according to claim 1, wherein in step (c), after the introducing of the crude product, the temperature of the at least one nonpolar solvent is brought for 3 times from room temperature to the boiling point of the at least one nonpolar solvent, and subsequently the at least one nonpolar solvent is allowed to cool to room temperature.

12. The process according to claim 1, wherein the crude product obtained in step (b) is uncharged tetrakis(trichlorosilyl)germane.

13. The process according to claim 1, wherein the process is free of added SiH.sub.4.

14. The process according to claim 1, wherein the process is free of added GeH.sub.4.

15. The process according to claim 1, wherein the process is free of added sodium.

16. The process according to claim 1, wherein no organic radicals are present in the tetrakis(trichlorosilyl)germane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A shows the .sup.29Si NMR spectrum of the product I.

(2) FIG. 1B shows the result of the analysis of the product I by X-ray diffractometry.

DETAILED DESCRIPTION OF THE INVENTION

(3) In the context of the invention, the term “standard pressure” is synonymous with the term “ambient pressure”. This is understood to mean the pressure of the surrounding gas of 1013 hPa. In the context of the invention, the term “room temperature” is abbreviated to “RT”.

(4) At least one, two, three or all of the steps of the process according to the invention can preferably be conducted under standard pressure and/or in an oxygen-free, dry environment.

(5) In the reaction in step b of the process according to the invention, a crude product is obtained that comprises, in addition to the salts [R.sub.4N][AlCl.sub.4] and/or [R.sub.4P][AlCl.sub.4], the chlorinated uncharged compound tetrakis(trichlorosilyl)germane.

(6) The ammonium or phosphonium chloride salts form salts with AlCl.sub.3 of the [R.sub.4N][AlCl.sub.4] or [R.sub.4P][AlCl.sub.4] type that are likewise present in the crude product. The uncharged molecule of the formula (I) is separated off from these salt-type compounds by extraction with nonpolar solvents and obtained in pure form. Suitable nonpolar solvents are advantageously pentane, hexane and/or benzene. Particularly preferably, n-hexane can be used.

(7) It may be advantageous, in step b of the process according to the invention, to conduct the reaction at room temperature, and/or in step d to remove the nonpolar solvent at room temperature.

(8) Additionally, in step b of the process according to the invention, the chlorinated hydrocarbon used may be dichloromethane CH.sub.2Cl.sub.2.

(9) In step c of the process according to the invention, the nonpolar solvent can preferably be selected from hexane, n-hexane, pentane and/or benzene. Particularly preferably, n-hexane can be used in step c.

(10) A further-preferred embodiment of the process according to the invention consists, in step a, in [X][Ge(SiCl.sub.3).sub.3] and AlCl.sub.3, these components preferably being in the solid state, being mixed by means of stirring, preferably in an oxygen-free environment, particularly preferably under protective gas, nitrogen or argon, additionally preferably in a glovebox, and, in step b, the mixture obtained in step a is dissolved completely in the chlorinated hydrocarbon(s), and, after a time of 0.1 to 24 hours, preferably after 1 to 5 hours, the chlorinated hydrocarbon(s) are removed, preferably at a temperature of 5 to 40° C. particularly preferably at room temperature, additionally preferably in an oxygen-free, dry environment, particularly preferably in an isolated environment, additionally preferably under standard pressure or reduced pressure, particularly preferably in the range from 1 to 500 hPa.

(11) It may additionally be advantageous when, in step c of the process, after the introduction of the crude product, the temperature of the nonpolar solvent(s) is brought for from 1 to 5 times, preferably 3 times, from RT to elevated temperature. The temperature of the nonpolar solvent(s) can preferably be brought to the boiling point at least of one nonpolar solvent, and subsequently the nonpolar solvent(s) can be allowed to cool, preferably to RT.

(12) It has furthermore been found that tetrakis(trichlorosilyl)germane can be reacted with 6 equivalents of LiAlH.sub.4 in the solvent Et.sub.2O to give the neutral hydrogenated compound tetrakis(silyl)germane. This reaction can preferably be conducted in a glovebox. It is additionally preferable to conduct the reaction at room temperature and under ambient pressure.

(13) The hydrogenated compound tetrakis(silyl)germane has indeed already been described by Thomas Lobreyer et al. (Angew. Chem. 1993, 105, 587-588). However, it was obtained in that document with the use of the pyrophoric and toxic starting materials SiH.sub.4 and GeH.sub.4.

(14) The example which follows provides additional explanation of the present invention without restricting the subject-matter.

(15) Example 1 describes the reaction of [Ph.sub.4P][Ge(SiCl.sub.3).sub.3] with AlCl.sub.3. The reaction of other ammonium or phosphonium tris(trichlorosilyl)germanide salts of the [R.sub.4N][Ge(SiCl.sub.3).sub.3] or [R.sub.4P][Ge(SiCl.sub.3).sub.3] type can be conducted analogously.

(16) Analytical Methods for Determination of the Crystal Structure

(17) The data for all structures were collected at 173 K using a STOE IPDS II two-circle diffractometer with a Genix microfocus tube having mirror optics using MoK.sub.α radiation (λ=0.71073 Å) and scaled using the frame scaling procedure of the X-AREA program (Sloe & Cie, 2002). The structures were solved by direct methods with the aid of the SHELXS program (Sheldrick, 2008) and refined on F.sup.2 by the full matrix least squares technique. Cell parameters were determined by refinement on θ values of the reflections with I>6σ(I).

Example 1: Preparation of tetrakis(trichlorosilyl)germane (I)

(18) The synthesis was effected in accordance with Equation 1 from [Ph.sub.4P][Ge(SiCl.sub.3).sub.3] with AlCl.sub.3 while adding CH.sub.2Cl.sub.2.

(19) ##STR00002##

(20) The reaction was conducted in a glovebox.

(21) [Ph.sub.4P][Ge(SiCl.sub.3).sub.3] at an amount of 0.10 g, corresponding to 0.12 mmol, and AlCl.sub.3 at an amount of 0.016 g, corresponding to 0.12 mmol, were mixed in the solid state and subsequently completely dissolved in dichloromethane CH.sub.2Cl.sub.2.

(22) After 3 hours, the dichloromethane was slowly evaporated at RT and under standard pressure. After one day, a mixture of Ge(SiCl.sub.3).sub.4 (I) and [Ph.sub.4P][AlCl.sub.4] had formed as crystalline crude product. The crude product was heated to boiling three times with in each case 7 ml of n-hexane.

(23) Subsequently, the clear, colourless n-hexane solution was separated off from the insoluble residue with a syringe.

(24) The nonpolar solvent was subsequently removed slowly at RT and under standard pressure, and after one day it was possible to isolate the inventive product Ge(SiCl.sub.3).sub.4 (I) as a crystalline substance. The yield was 0.018 g, corresponding to 0.029 mmol or 24%.

(25) The .sup.29Si NMR spectrum of the inventive product I is presented in FIG. 1a, and the result of the analysis thereof by means of X-ray diffractometry is presented in FIG. 1b.

(26) The data of the .sup.29Si NMR spectroscopy analysis:

(27) .sup.29Si NMR (99.4 MHz, CD.sub.2Cl.sub.2, 298 K): δ=3.8 ppm.