CATIONIC SILICON (II) COMPOUNDS AND METHOD FOR THE PRODUCTION THEREOF

Abstract

The invention relates to a method for producing cationic silicon(II) compounds of general formula I

(R.sup.aSi).sup.+HA.sup.(I) by reacting the silicon(II) compounds of general formula II

(R.sup.b-H)(R.sup.aSi).sup.+(II) with a hydride acceptor compound A, wherein R.sup.a, (R.sup.b-H) and A have the definitions described in claim 1;
to the cationic silicon(II) compounds of general formula I and use thereof as catalysts.

Claims

1. A method for producing cationic silicon(II) compounds of general formula I, comprising:
(R.sup.aSi).sup.+HA.sup.(I) reacting the silicon(II) compounds of general formula II
(R.sup.bH)(R.sup.aSi).sup.+(II) with a compound A, where R.sup.a is a carbon-containing radical, which may additionally comprise heteroatoms, bound to the cationic silicon atom via a covalent bond, ionic bond or via one or more bonds with the cationic silicon atom, (R.sup.bH) is a p-bonded singly negatively charged radical of general formula III, ##STR00003## R.sup.x are monovalent or polyvalent organic radicals, which may also be bonded to one another to form a fused ring, with the proviso that at least one of the radicals R.sup.x is an organic radical bonded via carbon bearing at least one hydrogen atom, and A is a compound which, as an electrophile, is capable of accepting electron pairs, wherein said compound has formula MX.sub.3 where M is B, Al or Ga, and where X is a C6-C20 aryl radical substituted by halogen.

2. A cationic silicon(II) compound of general formula I
(R.sup.aSi).sup.+HA.sup.(I) where R.sup.a is a carbon-containing radical, which may additionally comprise heteroatoms, bound to the cationic silicon atom via a covalent bond, ionic bond or via one or more p bonds with the cationic silicon atom and A is a compound which, as an electrophile, is capable of accepting electron pairs, having formula MX.sub.3 where M is B, Al or Ga, and where X is a C6-C20 aryl radical substituted by halogen.

3. The method of claim 1, wherein the radicals R.sup.x are each independently hydrogen, linear or branched, acyclic or cyclic, saturated or mono- or polyunsaturated C1-C20 alkyl or C6-C20 aryl radicals.

4. The method of claim 1, wherein R.sup.a is a p-bonded cyclopentadienyl radical substituted by the radicals R.sup.y(R.sup.y.sub.5Cp) wherein R.sup.y are monovalent or polyvalent organic radicals, which may be bonded to one another to also form fused rings.

5. The method of claim 1, wherein said reacting the silicon(II) compounds of general formula II with the compound A is carried out in aprotic solvents selected from the group consisting of hydrocarbons, chlorohydrocarbons, ethers, nitriles, organosilanes and organosiloxanes.

6. The cationic silicon(II) compounds of general formula I as claimed in claim 2, wherein said cationic silicon(II) compounds are catalysts.

Description

EXAMPLES

[0044] The reaction of silicocene, (C.sub.5Me.sub.5).sub.2Si with the hydride acceptor B(C.sub.6F.sub.5).sub.3 at 20 C. affords in quantitative yield the cationic silicon(II) compound (C.sub.5Me.sub.5)Si.sup.+HB(C.sub.6F.sub.5).sub.3 and tetramethylfulvene (C.sub.5Me.sub.4)=CH.sub.2.

Example 1

[0045] All process steps are carried out under Ar. 20.1 mg (0.067 mmol) of decamethylsilicocene [(C.sub.5Me.sub.5).sub.2Si, formula II where R.sup.aC.sub.5Me.sub.5 and (R.sup.bH)C.sub.5Me.sub.5], and 30.0 mg (0.059 mmol) of tris(pentafluorophenyl)borane are each dissolved in 0.5 ml of CD.sub.2C.sub.12 and the solutions combined in an NMR tube. A dark yellow coloration is immediately formed which indicates the formation of tetramethylfulvene. The solution comprises the compound (Me.sub.5C.sub.5)Si.sup.+BH(C.sub.5F.sub.5).sub.3.

[0046] The signals of this compound remain unchanged at 20 C. over a time period of 35 days, i.e. no conversion degradation takes place.

[0047] .sup.1H-NMR (CD.sub.2Cl.sub.2): =1.83 and 1.88 (2s, 4 Me of tetramethylfulvene), 2.19 [s, (Me.sub.5C.sub.5)Si.sup.+], 3.57 [q, broad, J(HB)=17 Hz, HB(C.sub.5F.sub.5).sub.3], 5.40 (s, 2H, H.sub.2C of tetramethylfulvene); .sup.19F-NMR (CD.sub.2Cl.sub.2): =133.6 (m, 2F); 164.1 (m, 1F); 167.2 (m, 2F);

[0048] .sup.29SiNMR (CD.sub.2Cl.sub.2): =399.1.

Example 2

[0049] All process steps are carried out under Ar. 11.8 mg (0.046 mmol) of decamethylsilicocene [(Me.sub.5C.sub.5).sub.2Si] and 23.3 g (0.046 mmol) of tris(pentafluorophenyl)borane are weighed successively into an NMR tube and 1 ml of CDCl.sub.3 is added. The two components dissolve and a dark yellow coloration is immediately formed which indicates the formation of tetramethylfulvene. The solution comprises the compound (Me.sub.5C.sub.5)Si.sup.+BH(C.sub.6F).sub.3.

[0050] .sup.1H-NMR (CDCl.sub.3): =1.76 and 1.82 (2s, 4 Me of tetramethylfulvene), 2.10 [s, (Me.sub.5C.sub.5)Si.sup.+], 3.48 [q, broad, HB(C.sub.6F.sub.5).sub.3], 5.40 (s, 2H, H.sub.2C);

[0051] .sup.29SiNMR (CDCl.sub.3): =399.9.

Example 3

[0052] All process steps are carried out under Ar. 100 mg (0.335 mmol) of decamethylsilicocene and 172 mg (0.335 mmol) of tris(pentafluorophenyl)borane are each dissolved in 0.5 ml of CD.sub.2Cl.sub.2 and the two solutions are combined. The solution immediately colors dark yellow, the reason being the formation of tetramethylfulvene. Heptane is added, whereupon a colorless crystalline precipitate of the compound (Me.sub.5C.sub.5)Si.sup.+BH(C.sub.6F.sub.5).sub.3 is formed. The suspension is concentrated a little under reduced pressure to remove CD.sub.2Cl.sub.2 and 1 ml of heptane is again added.

[0053] The solution is removed using a syringe and the crystalline residue is washed twice more with 1 ml of heptane each time. It is dried at 20 C. under high vacuum and 155 mg (64%) of the pure fulvene-free product (Me.sub.5C.sub.5)Si.sup.+BH(C.sub.6F.sub.5).sub.3 is obtained.

Example 4: Hydrosilylation Reaction

[0054] All process steps are carried out under Ar. 118.5 mg (1.00 mmol) of -methylstyrene and 136.7 mg (1.00 mmol) of dimethylphenylsilane are dissolved in 0.5 ml of CD.sub.2Cl.sub.2 and, at 20 C., a solution of 2.8 mg (0.0041 mmol) of the compound (Me.sub.5C.sub.5)Si.sup.+BH(C.sub.6F.sub.5).sub.3 (prepared as in example 3) in 0.5 ml of CD.sub.2Cl.sub.2 is added. The hydrosilylation reaction that occurs spontaneously with formation of the product PhSiMe.sub.2-CH.sub.2CH(CH.sub.3)Ph is monitored by .sup.1H-NMR spectroscopy. After 20 minutes ca. 50% product has formed and the reaction is complete after 24 hours.

Example 5: Hydrosilylation Reaction

[0055] All process steps are carried out under Ar. To the NMR sample prepared according to example 1, comprising the compound (Me.sub.5C.sub.5)Si.sup.+BH(C.sub.6F.sub.5).sub.3 and tetramethylfulvene, is added 9.1 mg (0.067 mmol) of dimethylphenylsilane. The initially still dark yellow solution decolorizes within a few hours. The yellow-colored tetramethylfulvene reacts completely with dimethylphenylsilane to form the hydrosilylation product PhSiMe.sub.2CH.sub.2C.sub.5Me.sub.4 (NMR spectroscopic investigation). The compound (Me.sub.5C.sub.5)Si.sup.+BH(C.sub.6F.sub.5).sub.3 is verified in unchanged amount by .sup.1H-NMR spectroscopy (singlet at =2.2 ppm).

Example 6: Hydrosilylation Reaction

[0056] All process steps are carried out under Ar. To a solution in CD.sub.2Cl.sub.2 prepared according to example 1, comprising 0.033 mmol of the compound (Me.sub.5C.sub.5)Si.sup.+BH(C.sub.6F.sub.5).sub.3 and tetramethylfulvene respectively, is added a mixture of 17.4 mg (0.147 mmol) of -methylstyrene and 14.3 mg (0.105 mmol) of dimethylphenylsilane. The products of the hydrosilylation reactions of dimethylphenylsilane with -methylstyrene [PhSiMe.sub.2CH.sub.2CH(CH.sub.3)Ph] and with tetramethylfulvene (PhSiMe.sub.2CH.sub.2C.sub.5Me.sub.4) are formed.