CATALYTIC REDUCTION OF HALOGENATED CARBOSILANES AND HALOGENATED CARBODISILANES

Abstract

Selective reduction methods for halogenated carbosilanes and carbodisilanes are disclosed. More particularly, high yields of the desired carbosilanes and carbodisilanes are obtained by reduction of their halogenated counterparts using a reducing agent and tetrabutylphosphonium chloride (TBPC) as a catalyst.

Claims

1. A method of synthesizing a carbosilane compound having the formula
SiH.sub.aR.sub.4-a wherein a=1 to 3 and R is a C.sub.1 to C.sub.12 alkyl group, a C.sub.3 to C.sub.12 aryl group, fused bicyclic aryl groups, a substituted phenyl group, or a heterocyclic group, comprising: reacting a halogenated carbosilane having the formula R.sub.bSiH.sub.cX.sub.4-b-c, wherein b=1 to 3; c=0 to 2; b+c=1 to 3; X=a halogen atom (Cl, Br or I); and R is a C.sub.1 to C.sub.12 alkyl group, a C.sub.3 to C.sub.12 aryl group, fused bicyclic aryl groups, a substituted phenyl group, or a heterocyclic group, with a reducing agent catalyzed by using tetrabutylphosphoniumchloride (TBPC) as a catalyst.

2. A method of synthesizing a carbodisilane compound having the formula
Si.sub.2H.sub.6-zR.sub.z, wherein z=1 to 5 and R is a C.sub.1 to C.sub.12 alkyl group, a C.sub.3 to C.sub.12 aryl group, fused bicyclic aryl groups, a substituted phenyl group, or a heterocyclic group, comprising: reacting a halogenated carbodisilane having the formula R.sub.zSi.sub.2H.sub.yX.sub.6-y-z, wherein z=1 to 5; y=0 to 4; y+z=1 to 5; X=a halogen atom (Cl, Br or I); and R is a C.sub.1 to C.sub.12 alkyl group, a C.sub.3 to C.sub.12 aryl group, fused bicyclic aryl groups, a substituted phenyl group, or a heterocyclic group, with a reducing agent catalyzed by using tetrabutylphosphoniumchloride (TBPC) as a catalyst.

3. The method of claim 1, wherein the reducing agent has the formula HSiR.sub.3 wherein R is a C.sub.1-C.sub.12 alkyl group.

4. The method of claim 2, wherein the reducing agent has the formula HSiR.sub.3 wherein R is a C.sub.1-C.sub.12 alkyl group.

5. The method of claim 1, wherein a=4-b-c.

6. The method of claim 5, wherein c=0.

7. The method of claim 6, wherein the reaction yields between approximately 60% w/w and approximately 80% w/w of the carbosilane compound.

8. The method of claim 1, wherein the reducing agent is selected from the group consisting of triethylsilane, trimethylsilane, and combinations thereof.

9. The method of claim 2, wherein the reducing agent is selected from the group consisting of triethylsilane, trimethylsilane, and combinations thereof.

10. The method of claim 1, wherein the halogenated carbosilane is a phenyl or aryl substituted carbohalosilane.

11. The method of claim 10, wherein the phenyl or aryl substituted carbohalosilane is dichlorodiphenylsilane.

12. The method of claim 10, wherein the phenyl or aryl substituted carbohalosilane is p-tolyltrichlorosilane.

13. The method of claim 1, wherein a molar ratio of the reducing agent to the halogenated carbosilane or halogenated carbodisilane is 0 to 10% mol/mol over stoichiometric amount.

14. The method of claim 1, wherein the halogenated carbosilane reduced by the reducing agent is a selective reduction.

15. The method of claim 2, wherein the halogenated carbosilane reduced by the reducing agent is a selective reduction.

16. The method of claim 2, wherein a molar ratio of the reducing agent to the halogenated carbosilane or halogenated carbodisilane is 0 to 10% mol/mol over stoichiometric amount.

17. The method of claim 2, wherein the halogenated carbosilane is a phenyl or aryl substituted carbohalosilane.

18. The method of claim 17, wherein the phenyl or aryl substituted carbohalosilane is dichlorodiphenylsilane.

19. The method of claim 17, wherein the phenyl or aryl substituted carbohalosilane is p-tolyltrichlorosilane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0052] FIG. 1 is a gas chromatogram/mass spectrum of the reaction product of Example 1;

[0053] FIG. 2 is a schematic diagram of the one pot synthesis components utilized in Example 2; and

[0054] FIG. 3 is a gas chromatogram/mass spectrum of the reaction product of Example 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0055] Methods of selectively synthesizing carbosilane and carbodisilane compounds are disclosed.

[0056] The carbosilane compounds have the formula SiH.sub.aR.sub.4-a wherein a=1 to 3; R is a C.sub.1 to C.sub.12 alkyl group, a C.sub.3 to C.sub.12 aryl group, fused bicyclic aryl groups, a substituted phenyl group, or a heterocyclic group. The carbodisilane precursors have the formula Si.sub.2H.sub.6-zR.sub.z wherein z=1 to 5; each R is independently a C.sub.1 to C.sub.6 alkyl group, a C.sub.3 to C.sub.12 aryl group, fused bicyclic aryl groups, or a heterocyclic group. These compounds may be used as precursors to form Si-containing films or Si-containing coatings in the field of ceramics, optical coatings, electronics (i.e., devices), semiconductors (i.e., components), hydrogen storage, and semiconductor components that may be used at least in electronic devices. In some embodiments, R=phenyl or substituted phenyl to produce arylsilanes.

[0057] Exemplary carbosilane compounds include, but are not limited to, H.sub.3Si(C.sub.6H.sub.5), H.sub.2Si(C.sub.6H.sub.5).sub.2, HSi(C.sub.6H.sub.5).sub.3, H.sub.3Si(C.sub.6H.sub.4Me), H.sub.2Si(C.sub.6H.sub.4Me).sub.2, HSi(C.sub.6H.sub.4Me).sub.3, H.sub.3Si(C.sub.5H.sub.5), H.sub.2Si(C.sub.5H.sub.5).sub.2, HSi(C.sub.5H.sub.5).sub.3, H.sub.3Si(C.sub.9H.sub.7), H.sub.2Si(C.sub.9H.sub.7).sub.2, HSi(C.sub.9H.sub.7).sub.3, H.sub.3Si(C.sub.10H.sub.7), H.sub.2Si(C.sub.10H.sub.7).sub.2, HSi(C.sub.10H.sub.7).sub.3, H.sub.3Si(C.sub.8H.sub.7), H.sub.2Si(C.sub.8H.sub.7).sub.2, HSi(C.sub.8H.sub.7).sub.3, H.sub.3Si(C.sub.9H.sub.9), H.sub.2Si(C.sub.9H.sub.9).sub.2, HSi(C.sub.9H.sub.9).sub.3, H.sub.3Si(C.sub.10H.sub.11), H.sub.2Si(C.sub.10H.sub.11).sub.2, or HSi(C.sub.10H.sub.11).sub.3.

[0058] Exemplary carbosilane compounds wherein a=2 and R=phenyl or a=3 and R=tolyl include SiH.sub.2(C.sub.6H.sub.5).sub.2 or SiH.sub.3(C.sub.6H.sub.4Me), respectively.

[0059] Exemplary carbodisilane compounds include, but are not limited to, Me.sub.2HSiSiHMe.sub.2; Et.sub.2HSiSiHEt.sub.2; iPr.sub.2HSiSiHiPr.sub.2; tBu.sub.2HSiSiHtBu.sub.2; MeH.sub.2SiSiH.sub.2Me; EtH.sub.2SiSiH.sub.2Et; iPrH.sub.2SiSiH.sub.2iPr; tBuH.sub.2SiSiH.sub.2tBu; (C.sub.6H.sub.5)H.sub.2SiSiH.sub.2(C.sub.6H.sub.5); (C.sub.6H.sub.5).sub.2HSiSiH(C.sub.6H.sub.5).sub.2; (C.sub.6H.sub.4Me)H.sub.2SiSiH.sub.2(C.sub.6H.sub.4Me); (C.sub.6H.sub.4Me).sub.2HSiSiH(C.sub.6H.sub.4Me).sub.2; (C.sub.5H.sub.5)H.sub.2SiSiH.sub.2(C.sub.5H.sub.5); or (C.sub.5H.sub.5).sub.2HSiSiH(C.sub.5H.sub.5).sub.2.

[0060] The disclosed carbosilane or carbodisilane compounds are synthesized by catalytic reduction of halogenated carbosilanes or halogenated carbodisilanes, respectively, by using a tetrabutylphosphoniumchloride catalyst (nBu.sub.4PCl or TBPC). The halogenated carbosilanes have the formula R.sub.bSiH.sub.cX.sub.4-b-c wherein b=1 to 3; c=0 to 2; X=a halogen atom (Cl, Br or I); R is a C.sub.1 to C.sub.12 alkyl group, a C.sub.3 to C.sub.12 aryl group, fused bicyclic aryl groups, a substituted phenyl group, or a heterocyclic group. These compounds are commercially available or may be synthesized by methods known in the art. In some embodiments, the halogenated carbosilanes may be carbochlorosilanes, carbobromosilanes, or carboiodosilanes. In particular, the halogenated carbosilanes may be phenyl or aryl substituted halosilanes. Exemplary phenyl or aryl substituted halosilanes include phenyl or aryl substituted chlorosilanes, phenyl or aryl substituted bromosilanes, or phenyl or aryl substituted iodosilanes.

[0061] Phenyl or aryl substituted halosilanes may be selectively reduced using the disclosed methods. In general arylhalosilanes are more stable than their alkyl counterparts and resist towards such halide exchange reactions. By using TBPC as a catalyst, however, the halide exchange reactions to the arylsilanes may be carried out.

[0062] As shown in the examples that follow, Applicants have surprisingly discovered that high yields of the desired phenyl or aryl carbosilane compound may be obtained when the 4-b-c value of the halogenated carbosilane equals the a value of the carbosilane compound. More particularly, high yields of the SiH.sub.2R.sub.2 compound are obtained when 4-b-c=a=2, when R=phenyl or aryl. Similarly, high yields of the SiH.sub.3R compound are obtained when 4-b-c=a=3.

[0063] The halogenated carbodisilanes have the formula R.sub.zSi.sub.2H.sub.yX.sub.6-y-z, wherein y=0 to 4; z=1 to 4; y+z=1-5; each X is independently a halogen atom selected from Cl, Br or I; each R is independently a C.sub.1 to C.sub.6 alkyl group, a C.sub.3 to C.sub.12 aryl group, fused bicyclic aryl groups, a substituted phenyl group, or a heterocyclic group. These compounds are commercially available or may be synthesized by methods known in the art. Exemplary halogenated carbodisilane compounds include carbochlorodisilanes, carbobromodisilanes, or carboiododisilanes such as Me.sub.2ClSiSiClMe.sub.2; Et.sub.2BrSiSiBrEt.sub.2; iPr.sub.2ISiSiIiPr.sub.2; tBu.sub.2ClSiSiCltBu.sub.2; MeBr.sub.2SiSiBr.sub.2Me; EtI.sub.2SiSiI.sub.2Et; iPrCl.sub.2SiSiCl.sub.2iPr; or tBuBr.sub.2SiSiBr.sub.2tBu. In particular, the halogenated carbodisilanes may be phenyl or aryl substituted halodisilanes. Exemplary phenyl or aryl substituted halodisilanes include phenyl or aryl substituted chlorodisilanes, phenyl or aryl substituted bromodisilanes, or phenyl or aryl substituted iododisilanes, such as (C.sub.6H.sub.5)I.sub.2SiSiI.sub.2(C.sub.6H.sub.5); (C.sub.6H.sub.5).sub.2ClSiSiCl(C.sub.6H.sub.5).sub.2; (C.sub.6H.sub.4Me)Br.sub.2SiSiBr.sub.2(C.sub.6H.sub.4Me); (C.sub.6H.sub.4Me).sub.2ISiSiI(C.sub.6H.sub.4Me).sub.2; (C.sub.5H.sub.5)Cl.sub.2SiSiCl.sub.2(C.sub.5H.sub.5); or (C.sub.5H.sub.5).sub.2BrSiSiBr(C.sub.5H.sub.5).sub.2.

[0064] The reducing agent may be a trialkylsilane having the formula HSiR.sub.3 wherein R is a C.sub.1-C.sub.12 alkyl group. These compounds are commercially available or may be synthesized by methods known in the art. Exemplary reducing agents include, but are not limited to, trimethylsilane or triethylsilane. The reduction produces a trimethylhalosilane or triethylhalosilane by-product that is easy to separate from the carbosilane or carbodisilane product.

[0065] The disclosed synthesis method may be a solvent free process. The reduction process may be controlled by reaction temperature, reaction time and/or by stoichiometry of the reducing agent. Different reaction temperatures and reaction times may produce different products. The reaction temperature may range from approximately 50 C. to approximately 100 C. A molar ratio of the reducing agent to the carbohalosilane or carbodihalosilane may range from approximately 0% to approximately 10% over the stoichiometric amount.

[0066] The disclosed synthesis method may be a selective reduction to the halogenated carbosilanes. The selective reduction may be achieved by varying the stoichiometric amount of the reducing agent. By this way, the disclosed synthesis method may allow making new exotic compounds when only selected number of halogens in the reactant halogenated carbosilanes is reduced and the new exotic molecules may be selectively synthesized in one step. For example, in the reaction of dicholorodiphenylsilane reduced by trimethylsiance using TBPC, if one chlorine is selected to be reduced, cholorodiphenylsilane may be produced with by-product trimethylcholorosilane which is easy to separate from the product.

[0067] The disclosed synthesis method allows 100% quantitative conversion and a yield around 72-80% after purification. The disclosed synthesis method is much safer than the conventional LAH reduction method because there is no slurry formed in the disclosed synthesis methods. Unlike the conventional LAH method that results in large amount of aqueous waste, the disclosed synthesis method allows minimal waste profile. Since the by-product is trialkylchlorosilane, the product purification is less tedious.

[0068] One of ordinary skill in the art will recognize the sources for the equipment components of the systems used to practice the disclosed methods. Some level of customization of the components may be required based upon the desired temperature range, pressure range, local regulations, etc. Exemplary equipment suppliers include Buchi Glass Uster AG, Shandong ChemSta Machinery Manufacturing Co. Ltd., Jiangsu Shajabang Chemical Equipment Co. Ltd, etc. As discussed above, the components are preferably made of corrosion resistant materials, such as glass, glass-lined steel, or steel with corrosion resistant liners, etc.

EXAMPLES

[0069] The following non-limiting examples are provided to further illustrate embodiments of the invention. However, the examples are not intended to be all inclusive and are not intended to limit the scope of the inventions described herein.

Example 1

Synthesis of Diphenylsilane

[0070]
Cl.sub.2Si(C.sub.6H.sub.5).sub.2+2Et.sub.3SiH.fwdarw.H.sub.2Si(C.sub.6H.sub.5).sub.2+2Et.sub.3SiCl

[0071] Dichlorodiphenylsilane (2 g, 7.9 mmol) was added to a reactor. The catalyst TBPC (0.2 g, 0.79 mmol) was added to the reactor to form a solution with dichlorodiphenylsilane. Triethylsilane (2 g, 17.4 mmol) was added to the resulting solution at room temperature under inert atmosphere. The resulting reaction mixture was heated to 100 C. for 15 hr. The reaction mixture was then cooled to ambient temperature. FIG. 1 is the gas chromatography/mass spectrum (GCMS) of the reaction mixture. FIG. 1 shows the peaks corresponding to the dichlorodiphenylsilane (SiCl.sub.2(C.sub.6H.sub.5).sub.2) and triethylsilane (Et.sub.3SiH) starting materials and the diphenylsilane (SiH.sub.2(C.sub.6H.sub.5).sub.2) and triethylchlorosilane (Et.sub.3SiCl) reaction products. In this preliminary R&D reaction, a small amount of SiHCl(C.sub.6H.sub.5).sub.2 was also produced. The GCMS showed 93% conversion of dichlorodiphenylsilane and the non-isolated yield determined by GC analysis was 60%. As can be seen, the majority of reactants are converted to the desired reaction products. Only a small amount of the SiHCl(C.sub.6H.sub.5).sub.2 disproportionation product was produced.

Example 2

Small Scale Synthesis of p-Tolylsilane

[0072]
Cl.sub.3Si(C.sub.6H.sub.4Me)+3Me.sub.3SiH.fwdarw.H.sub.3Si(C.sub.6H.sub.4Me)+3Me.sub.3SiCl

[0073] p-tolyltrichlorosilane 1 (1.3 g, 5.8 mmol) and TBPC 2 (0.13 g, 0.4 mmol) were added to the reactor 100 of FIG. 2. 3.3 mol equivalents of trimethylsilane 3 (1.4 g, 19.1 mmol) were condensed at 78 C. under inert atmosphere using condenser 20 into the reactor 100. The resulting reaction mixture was heated to 100 C. for 30 min. At this point, the pressure dropped significantly, indicating that the reaction was nearly complete. The reaction mixture was cooled to ambient temperature. The crude reaction product 5 was removed through filter 30 and line 5. Any volatile reaction products in line 5 are captured in the liquid nitrogen cryotrap 50. The crude reaction product was subject to GCMS analysis. FIG. 3 is the GCMS of the reaction mixture. FIG. 3 shows the peaks corresponding to the trimethylsilane (Me.sub.3SiH) starting material and the p-tolylsilane (SiH.sub.3(Me-C.sub.6H.sub.4)) and trimethylchlorosilane (Me.sub.3SiCl) reaction products. The GCMS analysis showed complete conversion of p-tolyltrichlorosilane. The non-isolated yield was 82%.

Example 3

Scale Up Synthesis of p-Tolylsilane

[0074]
Cl.sub.3Si(C.sub.6H.sub.4Me)+3Me.sub.3SiH.fwdarw.H.sub.3Si(C.sub.6H.sub.4Me)+3Me.sub.3SiCl

[0075] p-tolyltrichlorosilane (90 g, 0.4 mol) and TBPC (11.8 g, 0.04 mol) were added to a stainless steel pressure reactor. 3.3 mol equivalents of trimethylsilane (97.7 g, 1.3 mol) were added to the reactor forming a solution. The reactor was sealed and heated to 100 C. for 30 min. The reactor was cooled. The volatiles in the reaction mixture were cryotrapped in a stainless steel lecture bottle. The H.sub.3Si(C.sub.6H.sub.4Me) product was distilled under reduced pressure (1 Torr) at 30 C. The yield of the product was 36.2 g (0.29 mol; 74%).

Example 4

Catalyst Activity

[0076] The p-tolylsilane synthesis reaction was repeated 10 times using the same catalyst in the same reactor system as shown in FIG. 2. Table 2 below summarizes the mass balances for the 10 reactions. More particularly, 10.38 kg (46 moles) of Cl.sub.3Si(Me-C.sub.6H.sub.4) was converted by 130 g (0.44 moles) of the TBPC catalyst. This is a turnover number of 105 (46 moles/0.44 moles).

TABLE-US-00002 TABLE 2 Me.sub.3SiH Total Lights Total Cl.sub.3Si(MeC.sub.6H.sub.4) (g) In (g) Removed (g) Me.sub.3SiCl H.sub.3Si(MeC.sub.6H.sub.4) Out (g) (g) 10384 11517 21901 738 14461 g 5693 g 20892 1009 Theoretical 15.003 kg 5.63 kg GC % 14.45 kg 5.60 kg Non-isolated 13.2 kg 4.6 kg Yield % Non-isolated 88% 82% Yield over Theoretical Yield = Total In Total Out

[0077] It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and/or the attached drawings.