Process For The Cleavage Of Silicon-Silicon Bonds And/Or Silicon-Chlorine Bonds In Mono-, Poly- And/Or Oligosilanes

Abstract

The invention relates to a method for cleaving silicon-silicon bindings and/or silicon-chlorine bindings in monosilanes, polysilanes, and/or oligosilanes. According to the invention, the monosilane, polysilane, and/or oligosilane is dissolved or suspended in an ether or in an ether-hydrochloric acid solution. Said method is used for example for preparing halogenated oligosilanes from halogenated polysilanes and for preparing siloxanes from organochlorosilanes and chlorinated monosilanes. Said method is particularly simple to carry out and as a result is economical.

Claims

1-16. (canceled)

17. A method for the cleavage of at least one of silicon-silicon bonds and silicon-halogen bonds of at least one of monosilanes, polysilanes and oligosilanes, comprising dissolving or suspending the at least one of monosilanes, polysilanes and oligosilanes in ether or an ether-hydrochloric acid solution. cm. 18. The method of claim 17, characterized in that halogenated oligosilanes, are prepared by cleavage of SiSi bonds in halogenated polysilanes,

19. The method of claim 18, characterized in that the halogenated polysilanes are selected from the group consisting of chlorinated polysilanes and perchlorinated polysilanes.

20. The method of claim 18, characterized in that the halogenated polysilane is dissolved or suspended in ether or ethyl ether-hydrochloric acid solution.

21. The method according to claim 18, characterized in that halogenated oligosilanes having the formula Si.sub.nX.sub.2n+2, where X is a halogen, are prepared.

22. The method according to claim 17, characterized in that thermally produced halogenated polysilane, particularly perchlorinated polysilane is reacted.

23. The method according to claim 22, characterized in that thermally produced perchlorinated polysilane is reacted.

24. The method according to claim 17, characterized in that plasma-chemically produced halogenated polysilane is reacted.

25. The method according to claim 23, characterized in that thermally produced perchlorinated polysilane is reacted with Et.sub.2O or HCl in Et.sub.2O, to prepare Si.sub.2Cl.sub.6.

26. The method according to claim 24, characterized in that plasma-chemically produced perchlorinated polysilane is reacted with Et.sub.2O or HCl in Et.sub.2O, to prepare Si.sub.2Cl.sub.6.

27. The method according to claim 25, characterized in that thermally produced perchlorinated polysilane is reacted with HCl in Et.sub.2O to prepare XSi(SiCl.sub.3).sub.3 where X=H or Cl.

28. The method according to claim 26, characterized in that plasma-chemically produced perchlorinated polysilane is reacted with HCl in Et.sub.2O to prepare XSi(SiCl.sub.3).sub.3 where X=H or Cl.

29. The method according to claim 25, characterized in that thermally produced perchlorinated polysilane is reacted with HCl in Et.sub.2O to prepare X.sub.2Si(SiCl.sub.3).sub.2 where X=H or Cl.

30. The method according to claim 26, characterized in that plasma-chemically produced perchlorinated polysilane is reacted with HCl in Et.sub.2O to prepare X.sub.2Si(SiCl.sub.3).sub.2 where X=H or Cl.

31. The method according to claim 17, characterized in that the solution obtained from the reaction is isolated.

32. The method according to claim 17, characterized in that at least one halogenated oligosilane is isolated from the solution obtained.

33. The method according to claim 17, characterized in that it is used for the cleavage of at least one of polysiloxanes and oligosilanes and for the formation of siloxanes.

34. The method according to claim 33, characterized in that each SiSi and/or SiCl bond is cleaved thermally with a solution of HCl in diethyl ether and transferred into a siloxane unit.

35. The method according to claim 33, characterized in that cyclic, cage-like and/or linear siloxanes are generated from organohalogenmonosilanes and organohalogendisilanes.

36. The method according to claim 35, characterized in that it is used for the degradation of mixtures of organohalogendisilanes, in particular with chlorinated monosilanes.

37. The method according to claim 17, characterized in that it is used for the cleavage of SiCl bonds in monosilanes by using a solution of HCl in Et.sub.2O to form siloxanes.

Description

PREPARATION OF HCL/ET.SUB.2.O SOLUTION

[0042] Diethyl ether (p.a., stabilized with butylhydroxytoluene) was previously dried over sodium/benzophenone and distilled. Then, in a Schlenk flask with gas inlet tube, HCl gas, previously passed through concentrated sulfuric acid, was introduced into the diethyl ether. A slight warming of the solution occurred. The saturation was recognizable, when the quantity of the discharged gas is equal to the quantity of the introduced gas (indicated by a bubble counter). For completion this state was maintained for further 30 minutes.

[0043] By weighing it is determined that 76 g of HCl gas is dissolved in 298 g of diethyl ether (5 M). The molarity of HCl/Et.sub.2O solution was determined additionally by titration of an aliquot with water and NaOH.

Exemplary Embodiment 1

[0044] T-PCS (freed of SiCl.sub.4 in vacuo as far as possible; 64.64 g) was reacted with a saturated solution of HCl in diethyl ether (5 M, 113 mL) with ice cooling (0 C.) (a). The brownish solution was stirred for 16 hours and gradually warmed to room temperature (24 C.), whereupon a color change to pale yellow occurred.

[0045] The volatile components of the reaction mixture were condensed in vacuo (0.1 mbar) into a 196 C. (liquid N.sub.2) cooled cold trap (b). This condensate (c, 145 g) was then warmed to room temperature and distilled at normal pressure up to a boiling temperature of 80 C. The composition of the distillate (d, 104 g) is listed in column E (including the amounts in % and the characteristic .sup.29Si NMR shift values of the compounds). The residue from this distillation (e, 23 g) was subjected again at reduced pressure (membrane pump; 30 mbar) up to a boiling temperature of max. 130 C. to fractionated distillation to obtain two fractions. The distillation residue (f, 2 g) contains the compounds listed in column C, the distillate (g, 16 g), the compounds in column D. The condensation residue from (b) (h, 10 g) was distilled at reduced pressure at the rotary vane pump (0.1 mbar) up to a boiling temperature of 130 C. distilled. The residue remaining after this distillation (i, 7 g) consists mostly of insoluble chlorinated polysilanes as well as traces of the compounds mentioned in column A. In the distillate from (h) (j, 3 g), the compounds of column B are identified.

Illustration 1

Exemplary Embodiment 2

[0046] P-PCS (freed from SiCl.sub.4 in vacuo as far as possible; 4.9 g) was reacted with a saturated solution of HCl in diethyl ether (5 M, 2.5 mL) under ice-cooling (0 C.) (a). The red-brown solution was stirred for 14 hours and gradually warmed to room temperature (24 C.), whereupon only a slight discoloration occurred.

[0047] The volatile components of the reaction mixture were condensed in vacuo (0.1 mbar) into a 196 C. (liquid N.sub.2) cooled cold trap (b). The composition of this condensate (c, 4.2 g) is indicated in column B (including the amounts in % and the characteristic .sup.29Si NMR chemical shift values of the compounds). The condensate residue (d, 2.2 g) consists of the compounds indicated in column A.

Illustration 2

Exemplary Embodiment 3

[0048] In this method, cleavable disilanes Me.sub.xSi.sub.2Cl.sub.6x (x=0-3) and non-cleavable disilanes (x=46) are cleaved in a single reaction step into monomeric functional silanes, which subsequently after an exchange reaction SiX.fwdarw.SiOEt (X=H, Cl) can be directly transformed preferably into methyl- and/or, less preferred, into ethoxy-substituted cyclic siloxanes. The reagent employed here for SiSi and SiCl bond cleavage is a diethyl ether solution saturated with HCl gas (HCl/Et.sub.2O).

[0049] The disilanes used for the investigations Me.sub.xSi.sub.2Cl.sub.6x(x=0 to 6) and Me.sub.5Si.sub.2H were purchased and are known from the literature. They were checked for purity by GC-MS analysis and NMR spectroscopy (.sup.1H-, .sup.29SiNMR). The identified substance specific chemical shift values are consistent with literature data (see particularly R. Lehnert, M. Hoeppner, H. Kelling, Z. anorg. allg. Chem. 1990, 591, 209-213). The same applies for the cyclic, linear and cage-like siloxanes which have been obtained as the reaction products from the reaction of the disilanes Me.sub.xSi.sub.2Cl.sub.6x (x=0 to 6) and Me.sub.5Si.sub.2H. Since these siloxanes are basic building units for the technical manufacture of silicones, their substance-specific NMR chemical shift values particularly are also known from literature (see particularly H. Marsmann, .sup.29Si-NMR Spectroscopic Results in NMR: Oxygen-17 and silicone-29; Springer-Verlag: New York, 1981, 27, 65-235). Since for all reactants and products in addition to the mass spectrometric fragmentation, the retention times in the gas chromatogram are characteristic, in table 1 the employed disilanes as well as those obtained by substitution of SiCl.fwdarw.SiOR (R=Et, nBu) are listed with the characteristic retention time (in minutes) and the associated mass fragment. The disilanes 1-8 are listed in a sequence of decreasing shares in the residue of the disilane fraction of the MllerRochow process. Tab. 2 contains comparable data for monomeric silane degradation products, also alkoxysubstituted. The cyclic siloxanes D3 to D10 are listed in table 3, and in table 4 the values of linear siloxanes L2 to L13 are indicated. Table 5 contains the data for cage-type structure silsesquioxanes (RSiO.sub.3/2).sub.x (R=Me, Vi, Et; x=8, 10, 12) and open precursors.

TABLE-US-00001 TABLE 1 GC-MS data for disilanes. No. Disilane R.sub.T GC Mass Fragment 1 Cl.sub.2MeSiSiMeCl.sub.2 17.06 193 [M CH.sub.3].sup.+ 2 ClMe.sub.2SiSiMe.sub.2Cl 16.63 186 [M].sup.+ 3 Me.sub.3SiSiMe.sub.2Cl 15.47 151 [M H].sup.+ 4 Me.sub.3SiSiMe.sub.3 12.36 146 [M].sup.+ 5 Me.sub.3SiSiMe.sub.2H 11.02 131 [M H].sup.+ 6 Cl.sub.3SiSiCl.sub.3 7 Me.sub.3SiSiMeCl.sub.2 16.40 151 [M Cl].sup.+ 8 ClMe.sub.2SiSiMeCl.sub.2 17.02 171 [M Cl].sup.+ 9 Cl.sub.2MeSiSiMeCl(OEt) 18.04 209 [M C.sub.2H.sub.5].sup.+ 10 (EtO)ClMeSiSiMeCl(OEt) 18.64 211 [M Cl].sup.+ 11 Cl.sub.2MeSiSiMeCl(OBu) 19.59 229 [M Cl].sup.+ 12 (BuO)ClMeSiSiMeCl(OBu) 21.29 267 [M Cl].sup.+ 13 (BuO).sub.2MeSiSiMeCl(OBu) 22.63 341 [M + H].sup.+

TABLE-US-00002 TABLE 2 GC-MS data for monosilanes from SiSi Bond cleavages. No. Silane R.sub.T GC MS Basic Fragment I Me.sub.3SiH 3.25 43 [M H].sup.+ II Me.sub.3SiCl 6.45 93 [M CH.sub.3].sup.+ III Me.sub.3SiOEt 7.61 103 [M CH.sub.3].sup.+ IV MeSiCl.sub.3 7.95 147 [M].sup.+ V Me.sub.2SiCl.sub.2 8.53 113 [M CH.sub.3].sup.+ VI (EtO).sub.2MeSiH 11.89 133 [M H].sup.+ VII (EtO)MeSiCl.sub.2 12.66 143 [M CH.sub.3].sup.+ VIII (EtO).sub.2SiHCl 13.58 153 [M H].sup.+ IX (EtO).sub.2MeSiCl 14.83 153 [M CH.sub.3].sup.+ X (BuO)MeSiCl.sub.2 16.30 151 [M Cl].sup.+ XI (BuO).sub.2MeSiCl 18.87 225 [M + H].sup.+

TABLE-US-00003 TABLE 3 GC-MS data for cyclic methylsiloxanes. No. Siloxane R.sub.T GC Mass Fragment D3 (Me.sub.2SiO).sub.3 14.21 207 [M CH.sub.3].sup.+ D4 (Me.sub.2SiO).sub.4 16.78 281 [M CH.sub.3].sup.+ D5 (Me.sub.2SiO).sub.5 18.46 355 [M CH.sub.3].sup.+ D6 (Me.sub.2SiO).sub.6 19.91 429 [M CH.sub.3].sup.+ D7 (Me.sub.2SiO).sub.7 21.29 503 [M CH.sub.3].sup.+ D8 (Me(EtO)SiO).sub.4 18.62 401 [M CH.sub.3].sup.+ D9 (Me(EtO)SiO).sub.2(Me.sub.2SiO).sub.3 19.26 415 [M CH.sub.3].sup.+ D10 (Me(EtO)SiO).sub.5 21.11 505 [M CH.sub.3].sup.+

TABLE-US-00004 TABLE 4 GC-MS data for linear methyl siloxanes. No. Siloxane R.sub.T GC Mass Fragment L2 Me.sub.3SiOSiMe.sub.3 10.45 147 [M CH.sub.3].sup.+ L3 Me.sub.3Si(OSiMe.sub.2)OSiMe.sub.3 15.50 221 [M CH.sub.3].sup.+ L4 Me.sub.3Si(OSiMe.sub.2).sub.2OSiMe.sub.3 17.66 295 [M CH.sub.3].sup.+ L5 Me.sub.3Si(OSiMe.sub.2).sub.3OSiMe.sub.3 19.19 369 [M CH.sub.3].sup.+ L6 Me.sub.3Si(OSiMe.sub.2).sub.4OSiMe.sub.3 20.41 443 [M CH.sub.3].sup.+ L7 Me.sub.3Si(OSiMe.sub.2).sub.5OSiMe.sub.3 21.66 517 [M CH.sub.3].sup.+ L8 (EtO).sub.2MeSiO(EtOMeSiO).sub.3SiMe(OEt).sub.2 21.60 579 [M CH.sub.3].sup.+ L9 MeSi(OSiMe.sub.3).sub.2O(OSiMe.sub.3).sub.2SiMe 20.21 443 [M CH.sub.3].sup.+ L10 (EtO)Me.sub.2SiOSiMe.sub.2Cl 16.28 213 [M + H].sup.+ L11 (EtO)Me.sub.2SiOSiMe.sub.2(OEt) 16.55 207 [M CH.sub.3].sup.+ L12 ClMe.sub.2SiSiMe.sub.2OSiMe.sub.2SiMe.sub.2Cl 21.04 283 [M Cl].sup.+ L13 MeSi(OSiMe.sub.3).sub.3 17.48 295 [M CH.sub.3].sup.+

TABLE-US-00005 TABLE 5 GC-MS data for silsesquioxanes. No. Siloxane R.sub.T GC Mass Fragment T1 (MeSiO.sub.3/2).sub.8 20.65 521 [M CH.sub.3].sup.+ T2 (MeSiO.sub.3/2).sub.10 22.69 655 [M CH.sub.3].sup.+ T3 (MeSiO.sub.3/2).sub.12 24.68 789 [M CH.sub.3].sup.+ T4 C.sub.12H.sub.34O.sub.13Si.sub.8 21.09 595 [M CH.sub.3].sup.+ T5 (ViSiO.sub.3/2).sub.8 27.06 631 [M H].sup.+ T6 (ViSiO.sub.3/2).sub.10 37.59 789 [M H].sup.+ T7 (EtSiO.sub.3/2).sub.8 27.76 619 [M C.sub.2H.sub.5].sup.+ T8 C.sub.16H.sub.44O.sub.14Si.sub.8 22.01 669 [M CH.sub.3].sup.+ T9 C.sub.20H.sub.54O.sub.15Si.sub.8 23.26 743 [M CH.sub.3].sup.+

[0050] Furthermore, in table 6 below the analytical data of further solvents and reagents used in our studies are listed.

TABLE-US-00006 TABLE 6 GC-MS data of the solvent and HCl. Substance R.sub.T GC Mass Fragment HCl 2.70 36 [M].sup.+ EtCl 3.87 63 [M H].sup.+ EtOH 4.08 47 [M + H].sup.+ Et.sub.2O 4.35 75 [M + H].sup.+ CH.sub.2Cl.sub.2 5.20 84 [M].sup.+ THF 10.30 73 [M + H].sup.+ Butylated 21.78 220 [M].sup.+ Hydroxytoluene (BHT)

[0051] Attempts for the disilane cleavage were carried out with solutions of HCl in Et.sub.2O with different concentrations/conditions.

[0052] The experiments were performed at room temperature in a Schlenk flask with stirring. 100-300 mg of the disilane were introduced, and 3-5 mL of a saturated solution of HCl in Et.sub.2O was added thereto. After a corresponding period of time a portion (0.1 mL) of the reaction solution was removed for analysis by GCMS. For NMR spectroscopy 0.4-0.5 mL of the reaction solution was mixed with 0.1 mL C.sub.6D.sub.6 in an NMR tube.

[0053] Experiments at elevated temperatures were carried out in glass ampoules. The vials have a length of 125 mm, an outer diameter of 26 mm and a wall thickness of 2 mm. The internal volume up to the melting site corresponds to 43 mL. Also in this case to 100 to 300 mg of the disilane 3 to 5 ml of a saturated solution of HCl in Et.sub.2O were added. The reaction mixture was frozen using liquid nitrogen and sealed under vacuum. The vial with the reaction solution was then brought to room temperature, placed in a screwable metal pipe and ultimately heated in a vacuumed drying oven to the appropriate reaction temperature. The reaction pressure in the glass ampoule is estimated at 5-10 bar.

[0054] In this case, the degradation of 1,1,2,2-tetrachlorodimethyldisilane, 1,2-dichlorotetramethyldisilane, chloropentamethyldisilan, hexamethyldisilane, pentamethyldisilane and mixtures of the above-mentioned first four substances was carried out. Furthermore, the degradation of the disilane-residue from a technical Mller-Rochow synthesis and the reaction of monomeric trichlorosilane with HCl/Et.sub.2O, the reaction of monomeric dichlorosilanes with HCl/Et2O, the reaction of monomeric monochlorosilanes with HCl/Et.sub.2O and mixtures of monosilanes with HCl/Et.sub.2O-solutions was carried out. The following results were obtained:

[0055] Each SiSi and SiCl bond was cleaved using a solution of HCl in diethyl ether in one step and transferred into a siloxane unit. Methyl groups of the silanes (with the exception of hexamethyldisilane, which reacts in part to pentamethylchlorodisilane) remained untouched, and siloxanes were obtained corresponding to the remaining functionality:

[0056] MeSi>trifunctional siloxanes

[0057] Me.sub.2Si>difunctional siloxanes, chain extension

[0058] Me.sub.3Si>monofunctional siloxanes, overcapping reagent

[0059] These reactions were performed via a cleavage of diethyl ether by means of HCl, which provided ethanol for the alcoholysis of the SiCl groups. The ethoxydisilanes formed were thereby more prone to SiSi bond cleavage and transferred into the monosilane. Under the chosen reaction conditions, then directly condensation of the ethoxysilanes occured, that is, with subsequent formation of the siloxane units.

Exemplary Embodiment 4

[0060] a) A reaction of Me.sub.2SiCl.sub.2 with HCl/Et.sub.2O at 120 C. for 67 h leads to the following cyclic siloxanes (GC-MS analysis, Illustration 3),

Illustration 3

[0061] b) A reaction of mixtures of Me.sub.2SiCl.sub.2 and Me.sub.3SiCl with HCl/Et.sub.2O leads after 68 h at 120 C. as expected to a mixture of cyclic and linear siloxanes. This is exemplified in illustration 4.

Illustration 4

[0062] Increasing the Me.sub.2SiCl.sub.2 stake (molar ratio Me.sub.2SiCl.sub.2:Me.sub.3SiCl=4:1) under similar conditions (120 C., 68 h) results in a significant increase in the proportion of cyclic siloxanes in the reaction mixture (illustration 5, page 5).

Illustration 5

[0063] Increasing the Me.sub.3SiCl stake (molar ratio Me.sub.2SiCl.sub.2:Me.sub.3SiCl=1:4) leads under similar conditions (120 C., 68 h) to a significant increase in the proportion of linear siloxanes (illustration 5, Page 6) in the reaction mixture.

[0064] c) The reaction of MeSiCl.sub.3 with HCl/Et.sub.2O for 65 h at 120 C. leads to the silsesquioxanes T1, T2 and T3.

[0065] To generalize this reaction sequence exemplarily further trichlorosilanes XSiCl.sub.3 (X=vinyl, ethyl) were reacted with HCl/Et.sub.2O reacted. The reaction of trichlorovinylsilane (ViSiCl.sub.3) with HCl/Et.sub.2O for 69 h at 120 C. leads to the almost selective formation of (ViSiO.sub.3/2).sub.8 (T5, R.sub.T=27.06 min) in addition to traces of (ViSiO.sub.3/2).sub.10 (T6, R.sub.T=37.59 min). Trichloroethylsilane (EtSiCl.sub.3) reacts with HCl/Et.sub.2O after 68 h at 120 C. also selectively to the corresponding silsesquioxane (EtSiO.sub.3/2).sub.8 (T7, R.sub.T=27.75 min).

[0066] As expected mixtures of MeSiCl.sub.3, EtSiCl.sub.3 and ViSiCl.sub.3 react to silsesquioxanes with random distribution of the methyl, ethyl and vinyl groups at the corners of the silsesquioxanes (illustration 6, Tab. 7)

Illustration 6

[0067]

TABLE-US-00007 TABLE 7 GC-MS data of mixed silsesquioxanes R.sub.T GC Silsesquioxane Mass Fragment 22.37 (MeSiO.sub.3/2).sub.6 (ViSiO.sub.3/2)(EtSiO.sub.3/2) 562 [M H].sup.+ 23.08 (MeSiO.sub.3/2).sub.5 (ViSiO.sub.3/2).sub.2(EtSiO.sub.3/2) 574 [M H].sup.+ 23.88 (MeSiO.sub.3/2).sub.4 (ViSiO.sub.3/2).sub.2(EtSiO.sub.3/2).sub.2 589 [M H].sup.+ 24.85 (MeSiO.sub.3/2).sub.3 (ViSiO.sub.3/2).sub.3(EtSiO.sub.3/2).sub.2 602 [M].sup.+ 25.93 (MeSiO.sub.3/2).sub.2 (ViSiO.sub.3/2).sub.3(EtSiO.sub.3/2).sub.3 602 [M CH.sub.3].sup.+