METHOD FOR PRODUCING PERHALOGENATED HEXASILANE ANION AND METHOD FOR PRODUCING A CYCLIC SILANE COMPOUND

Abstract

The present invention relates to a process for the production of perhalogenated hexasilane anion by reacting halogenated monosilane in the presence of organosubstituted ammonium and/or phosphonium halide at temperatures in a range from 100 to 120° C., wherein no solvent is used, and a process for the production of a cyclic silane compound of the formula Si.sub.6R.sub.12, by reacting [X].sub.2[Si.sub.6Cl.sub.14] with AlR.sub.3 in at least one organic solvent, wherein R is chlorine or methyl and X, the same or different, is a counter-cation and is preferably selected from organosubstituted ammonium, organosubstituted phosphonium, alkali metal ions and [(PEDETA)(H.sub.2SiCl)]+.

Claims

1. A process for the production of perhalogenated hexasilane anion by reacting halogenated monosilane in the presence of organosubstituted ammonium and/or phosphonium halide at temperatures in a range from 100 to 120° C., wherein no solvent is used.

2. The process for the production of perhalogenated hexasilane anion as claimed in claim 1, wherein the halogenated monosilane is trichlorosilane or dichlorosilane.

3. The process for the production of perhalogenated hexasilane anion as claimed in claim 1, wherein no additional Lewis base is added.

4. The process for the production of perhalogenated hexasilane anion as claimed in claim 1, wherein the reaction time is 12 to 96 hours.

5. The process for the production of perhalogenated hexasilane anion as claimed in claim 1, wherein the ratio of halogenated monosilane to organosubstituted ammonium and/or phosphonium halide is 3:1 to 50:1.

6. The process for the production of perhalogenated hexasilane anion as claimed in claim 1, wherein the organosubstituted ammonium and/or phosphonium halide is selected from [nBu.sub.4N]Cl, [Et.sub.4N]Cl, [Ph.sub.4P]Cl and [nBu.sub.4P]Cl.

7. The process for the production of perhalogenated hexasilane anion as claimed in claim 1, wherein hydrogen (H.sub.2) is obtained as a by-product in the production of the hexasilane anion.

8. A process for the production of a cyclic silane compound of the formula Si.sub.6R.sub.12, by reacting [X]2[Si.sub.6Cl.sub.14] with AlR.sub.3 in at least one organic solvent, wherein R is chlorine or methyl, and X, the same or different, is a counter-cation.

9. The process for the production of a cyclic silane compound as claimed in claim 8, wherein X is organosubstituted ammonium and/or organosubstituted phosphonium.

10. The process for the production of a cyclic silane compound as claimed in claim 9, wherein each organosubstituent of the organosubstituted ammonium or of the organosubstituted phosphonium is independently selected from ethyl, propyl, butyl and phenyl.

11. The process for the production of a cyclic silane compound as claimed in claim 8, wherein the organic solvent is selected from benzene, cyclohexane, n-hexane, n-heptane, chloroform and dichloromethane.

12. The process for the production of a cyclic silane compound as claimed in claim 8, wherein the process is carried out in a temperature range from 20° C. to 120° C.

13. The process for the production of a cyclic silane compound as claimed in claim 8, wherein the ratio of [X].sub.2[Si.sub.6Cl.sub.14] to AlR.sub.3 lies in a range of 5:1 to 1:10.

14. The process for the production of a cyclic silane compound as claimed in claim 8, wherein the Si.sub.6Cl.sub.12 obtained is cleaved in a subsequent reaction.

15. The process for the production of a cyclic silane compound as claimed in claim 8, wherein the counter cation is selected from organosubstituted ammonium, organosubstituted phosphonium, alkali metal ions and [(PEDETA)(H2SiCl)]+.

Description

[0044] Further features and advantages of the invention will become clear from the following description, drawings and example embodiments. There,

[0045] FIG. 1 shows a .sup.29Si-{.sup.1H} NMR spectrum measured in CD.sub.2Cl.sub.2, the solution obtained in variant A of the synthesis of [nBu.sub.4N].sub.2[Si.sub.6Cl.sub.14].

[0046] FIG. 2 shows a .sup.29Si NMR spectrum measured in CD.sub.2Cl.sub.2, the solid obtained in variant A of the synthesis of [nBu.sub.4N]2[Si.sub.6Cl.sub.14]. The .sup.29Si NMR spectrum of the raw product shown in FIG. 2 was measured in CD.sub.2Cl.sub.2 after applying a vacuum and demonstrates the low level of by-product formed.

[0047] FIG. 3 shows a .sup.29Si NMR spectrum measured in C.sub.6D.sub.6, the solution obtained in variant B of the synthesis of [nBu.sub.4N]2[Si.sub.6Cl.sub.14].

[0048] FIG. 4 shows a .sup.1H NMR spectrum measured in C.sub.6D.sub.6, the solution obtained in variant B of the synthesis of [nBu.sub.4N]2[Si.sub.6Cl.sub.14].

[0049] FIG. 5 shows a .sup.29Si NMR spectrum of the cyclic silane compound Si.sub.6Cl.sub.12, produced by method A, in C.sub.6D.sub.6 at 99.4 MHz.

[0050] FIG. 6 shows a .sup.29Si NMR spectrum of the silane compound Si.sub.6Cl.sub.12, produced by method B, in C.sub.6D.sub.6 at 99.4 MHz.

[0051] FIG. 7 shows a .sup.29Si NMR spectrum of the silane compound Si.sub.6Me.sub.12 in C.sub.6D.sub.6 at 99.4 MHz.

GENERAL WORKING CONDITIONS

[0052] All the reactions in the process for the production of perhalogenated hexasilane anion were carried out under dry argon or nitrogen. CD.sub.2Cl.sub.2 was dried over CaH.sub.2 and freshly distilled before use. HSiCl.sub.3 and [nBu.sub.4N]Cl are commercially available; [nBu.sub.4N]Cl was dried in a vacuum at room temperature for 2 d. .sup.29Si NMR spectra were recorded with a Bruker Avance III HD 500 MHz spectrometer; the spectra were calibrated against the external standard SiMe.sub.4 (δ(.sup.29Si)=0).

[0053] Synthesis of [nBu.sub.4N]2[Si.sub.6Cl.sub.14]

[0054] Variant A:

[0055] A jar was placed in an autoclave and filled with [nBu.sub.4N]Cl (5.0 g, 18 mmol) and HSiCl.sub.3 (30 mL, 40.2 g, 297 mmol) in an argon-filled glovebox. The autoclave was sealed and tested for leaks under 50 bar nitrogen pressure. After that, the reaction mixture was heated to 100 to 120° C. for 44 h. During the time of the reaction, there was a slight overpressure of approx. 5 bar in the autoclave. The temperature was measured on the outside of the autoclave between the metal wall and the heating jacket. After the reaction vessel had cooled, a pressure of 50 bar was generated three times in the vessel with nitrogen and then released again in order to remove any hydrogen and H.sub.2SiCl.sub.2 that had formed. The jar was removed in an argon counterflow. In the jar, there was a large amount of white solid on top of a small amount of clear colourless liquid (the amounts are stated relative to the amounts of educts used, HSiCl.sub.3 and [nBu.sub.4N]Cl). A .sup.29Si{.sup.1H} NMR spectrum of the solution in CD.sub.2Cl.sub.2 mainly showed the chemical shift of HSiCl.sub.3 (−10.0 ppm) and SiCl.sub.4 (−18.9 ppm). In addition, minor components identified in the .sup.29Si{.sup.1H} NMR spectrum of the solution were H.sub.2SiCl.sub.2 (−11.5 ppm) and a siloxane which was not definitively identifiable (−46.0 ppm, e.g. Cl.sub.3SiOSiCl.sub.3) or a mixture of different siloxanes (see FIG. 1). The origin of the siloxane is not known; the source might, however, be attributable to traces of water which might have entered the reaction mixture during the refilling or transferring step.

[0056] The solid contained in the reaction jar was dried in a vacuum. 9.9 g product were isolated (yield≧80%). The .sup.29Si NMR spectrum of the solid in CD.sub.2Cl.sub.2 showed the chemical shift of [Si.sub.6Cl.sub.14].sup.2- (21.8 ppm). As a by-product, [Si.sub.6Cl.sub.13H].sup.2- (−36.9 ppm (d, J=230 Hz, 1 Si), −23.0 ppm (d, J=2 Hz, 1 Si), −22.0 ppm (d, J=4 Hz, 2 Si), (−18.0 ppm (d, J=22 Hz, 2 Si)) were identified. In addition, HSiCl.sub.3 (−11.1 ppm (d, J=363 Hz)) and SiCl.sub.4 (−18.9 ppm) could also be identified in the spectrum (see FIG. 2).

[0057] Variant B:

[0058] An NMR tube was filled with [nBu.sub.4N]Cl (0.16 g, 0.6 mmol) and HSiCl.sub.3 (0.5 mL, 0.67 g, 5.0 mmol) and C.sub.6D.sub.6 (0.2 mL) in an argon-filled glovebox and melted in a vacuum. The solvent, C.sub.6D.sub.6, is only needed for the NMR measurement and was already added at the beginning for process engineering reasons. The involvement of benzene in the reaction was ruled out in an experiment without solvent. The sealed NMR tube was heated to 120° C. for 48 h. After the reaction time, a .sup.29Si NMR spectrum was measured. In the spectrum, the chemical shifts of HSiCl.sub.3 (−9.9 ppm, d, J=364 Hz), H.sub.2SiCl.sub.2 (−11.7 ppm, t, J=289 Hz) and SiCl.sub.4 (−18.9 ppm) could be identified (see FIG. 3). There is no shift of the product [Si.sub.6Cl.sub.14].sup.2-, because it is sparingly soluble in benzene. It was possible to identify it unambiguously by means of x-ray crystallography. In addition to the chemical shifts of the butyl group, the shifts of HSiCl.sub.3 (5.78 ppm), H.sub.2SiCl.sub.2 (5.12 ppm) and H.sub.2 (4.53 ppm) were identified in the .sup.1H NMR spectrum (see FIG. 4). Carrying out this reaction in sealed glass vessels is extremely dangerous, since they are under considerable pressure because of the gases forming. The experiment was only carried out in the molten NMR tube so that the gases forming could be detected beyond doubt.

[0059] Synthesis of [Et.sub.4N]2[Si.sub.6Cl.sub.14] and [Ph.sub.4P][Si.sub.6Cl.sub.14]:

[0060] The syntheses with [Et.sub.4N]Cl and [Ph.sub.4P]Cl as the educt proceed analogously to the synthesis proceeding from [nBu.sub.4N]Cl. Because of the poorer solubilities, the yields are lower (<50%); the reaction times should therefore be made longer, preferably 72 hours. In both cases, [Si.sub.6Cl.sub.13H].sup.2- is also obtained with the corresponding counter-ion as a by-product. The analytical method is limited in both cases to x-ray crystallography, since the main products obtained are not soluble; using monocrystal structural analysis, [Si.sub.6Cl.sub.14].sup.2-was clearly identified as the product.

[0061] Synthesis of Si.sub.6Cl.sub.12

[0062] Method A:

[0063] [nBu.sub.4N]2[Si.sub.6Cl.sub.14] (1.00 g, 0.87 mmol) and AlCl.sub.3 (0.24 g, 1.80 mmol) were prepared in benzene (6 mL) and stirred overnight at room temperature. After that, the solvent was removed in a vacuum. The colourless residue obtained was absorbed in dry cyclohexane and the suspension obtained was heated to 80° C. for 0.5 h. The batch was filtered and the solvent of the clear filtrate was removed in a vacuum. 0.50 g Si.sub.6Cl.sub.12 were obtained as a colourless solid (yield: 0.84 mmol, corresponding to 97%). The .sup.29Si NMR spectrum (C.sub.6D.sub.6; 99.4 MHz; see FIG. 1) of the solid showed the chemical shift of Si.sub.6Cl.sub.12 (−2.95 ppm). An examination by x-ray crystallography of monocrystals, selected from the solid obtained, revealed the crystal structure of Si.sub.6Cl.sub.12. In the filter cake obtained, the monocrystal x-ray structures of [nBu.sub.4N][AlCl.sub.4] and [nBu.sub.4N][AlCl.sub.4]*C.sub.6H.sub.6 were identified.

[0064] Method B:

[0065] [nBu.sub.4N].sub.2[Si.sub.6Cl.sub.14] (5.10 g, 4.44 mmol) and AlCl.sub.3 (1.23 g, 9.23 mmol) were prepared in benzene (45 mL) and stirred overnight at room temperature. After that, the solvent was removed in a vacuum. The colourless residue obtained was absorbed in dry hexane and the suspension obtained was heated to 80° C. for 0.5 h. The batch was filtered, concentrated to 10 mL by evaporation and stored at −72° C. for crystallisation. 2.51 g Si.sub.6Cl.sub.12 were obtained as a colourless crystalline solid (yield: 4.23 mmol, corresponding to 95%). The .sup.29Si NMR spectrum (C.sub.6D.sub.6; 99.4 MHz; see FIG. 2) of the solid showed the chemical shift of Si.sub.6Cl.sub.12 (−2.95 ppm). An examination of the monocrystals by x-ray crystallography likewise verified the product obtained as Si.sub.6Cl.sub.12.

[0066] Method C:

[0067] [nBu.sub.4N]2[Si.sub.6Cl.sub.14] (5.8 g, 5.1 mmol), which for processing reasons also contains [nBu.sub.4N]Cl (2.2 g, 7.0 mmol), and AlCl.sub.3 (2.4 g, 18.0 mmol) were prepared in benzene (60 mL) and stirred overnight at room temperature. After that, the solvent was removed in a vacuum. The residue obtained was an intense yellow and was absorbed in hexane (50 mL) and heated to 80° C. for 0.5 h. The supernatant was filtered, and the clear, colourless filtrate was concentrated to 10 mL by evaporation and stored at −72° C. for crystallisation. After 24 hours, the supernatant solution was decanted and 0.5 g solid were isolated. The solution was concentrated to approx. 10 mL by evaporation and stored at −72° C. for further crystallisation. Si.sub.6Cl.sub.12 was isolated as a colourless solid (total yield: 2.6 g, 87%). The .sup.29Si NMR spectrum of the solid showed the chemical shift of Si.sub.6Cl.sub.12 (−2.95 ppm). An examination by x-ray crystallography of monocrystals, selected from the solid obtained, revealed the crystal structure of Si.sub.6Cl.sub.12. In the filter cake obtained, the monocrystal x-ray structures of [nBu.sub.4N][AlCl.sub.4] and [nBu.sub.4N][AlCl.sub.4]*C.sub.6H.sub.6 were identified.

[0068] Synthesis of Si.sub.6Me.sub.12

[0069] Method A:

[0070] [nBu.sub.4N]2[Si.sub.6Cl.sub.14] (1.00 g, 0.87 mmol) was covered with an AlMe.sub.3/heptane solution (1.75 mL, 3.5 mmol, 2 mol/L) and then mixed with dichloromethane (5 mL). The batch was stirred at room temperature for 7 days. After that, the solvent was removed in a vacuum. The residue obtained was reddish-brown and was absorbed in 4 mL hexane and heated to 80° C. for 10 min. The supernatant was filtered, and the clear, colourless filtrate was concentrated to 1 mL by evaporation and stored at −72° C. for crystallisation. After 48 hours, the supernatant solution was decanted and the colourless solid was dried in a vacuum. 249 mg Si.sub.6Me.sub.12 were obtained (yield: 0.714 mmol, corresponding to 82%). The .sup.29Si NMR spectrum (C.sub.6D.sub.6; 99.4 MHz; see FIG. 3) of the solid showed the chemical shift of Si.sub.6Me.sub.12 (−42.2 ppm).

[0071] It is within the scope of the invention that the process for the production of perhalogenated hexasilane anion can be followed by the process of the invention for the production of a cyclic silane compound.

[0072] The features of the invention disclosed in the above description, the claims and the drawings can be essential both individually and in any combination to implementing the invention in its various embodiments.