Boron-containing carbosilanes, boron-containing oligo or...

Details Boron-containing carbosilanes, boron-containing oligo or... Boron-containing carbosilanes, boron-containing oligo or...

1999-09-29

2001-06-05

Shaver, Paul F. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Silicon containing

C536S063000, C501S096100, C501S096300, C501S096500, C528S030000

Reexamination Certificate

active

06242626

ABSTRACT:

The present invention relates to boron-containing carbosilanes, a process for their preparation, boron-containing oligo- or polycarbosilazanes, a process for their preparation and their use and silicon borocarbonitride ceramics and a process for their preparation.
The process for producing multinary, non-oxidic ceramics via molecular single-component precursors has achieved outstanding importance. It opens up the path to nitridic, carbidic and carbonitridic systems which cannot be prepared by conventional solid-state reactions. The products are distinguished by high purity and a homogeneous element distribution on a molecular level.
Ceramic materials consisting of Si, B, N and C demonstrate particular properties with respect to thermal stability and resistance to oxidation. They can be used industrially as bulk material, in composite materials, but also for coatings or as ceramic fibres. These amorphous boron-containing materials, compared with the boron-free (Si—C—N)-compounds, are distinguished by an increased crystallization inhibition, whereas the carbon-containing compounds have, in addition, higher decomposition temperatures than the carbon-free compounds.
According to U.S. Pat. No. 5,233,066, synthesis of the amorphous ceramics Si
3
B
3
N
7
and SiBN
3
C from the precursor trichlorosilylaminodichloroborane (TADB) is achieved by crosslinking with ammonia or amines and subsequent pyrolysis in the gas stream. According to DE-4320785, trissilylalkylboranes of the formula B[—C
2
H
4
—SiCl
2
X]
3
are obtained by reacting vinylsilanes of the formula CH
2
═CH—SiCl
2
X with BH
3
.THF. Carbon-rich ceramics prepared from this single-component precursor have a (Si:B) ratio of 3:1.
In Organosilicone Chemistry III VCH, (1997), via hydroboration of vinylsilane with BH
2
Cl.SMe
2
, a single-component precursor for Si,B,N,C-containing ceramics, abbreviated hereafter as SiBNC, is described, which has a solid Si:B ratio of 2:1, which is also retained in the ceramics.
In the case of all previously known single-component precursors, thus, disadvantageously, the Si:B ratio is bound to the single-component precursor used and the type of crosslinking The stoichiometry of C:N ratio can only be controlled via the pyrolysis conditions and choice of the crosslinking agent (NH
3
or alkylamines).
However, during the pyrolysis, the C:N ratio is set in an uncontrolled manner by reactions which have not been explained in detail. A disadvantage of these syntheses is the low possibility of varying the C content, since extending the side chain does not inevitably lead to a higher C content in the ceramics, but to graphite sediments in the material, which adversely affect the properties.
Although Appl. Organomet. Chem. 10 (1996) 241-256 describes polymeric boron-containing carbosilanes which were obtained by reacting vinyl-containing polysilanes or polysilazanes with borane adducts of the formula BH
3
.SR
2
, this possibility of varying the stoichiometries by using non-single-component precursor compounds, as described in J. Am. Ceram. Soc. 355 (1990) 714-718 for example, leads to ceramics whose properties (e.g. heat stability) are significantly inferior to those produced from single-component precursors.
The object of the present invention was the provision of novel boron-containing carbosilanes which are easy to prepare and permit a high possibility of varying all constituent elements, i.e. B, C, N and Si and can be used as precursors for novel, amorphous silicon borocarbonitride ceramics. For specific applications, by matching the stoichiometry, the respective property optimum is thus to be able to be set.
It has now been found that boron-containing carbosilanes of the formula (I)
where
R
1
=
where
R
4
=H, C
1
-C
3
-alkyl and/or phenyl,
R
5
=Cl, Br,
R
6
, R
7
=Cl, Br, H, C
1
-C
3
-alkyl or phenyl,
R
2
=R
1
or Cl, Br,
R
3
=R
5
,
R′=SMe
2
, NMe
2
H,
where
n=0 when R
2
=R
1
,
n=1 when R
2
=R
5
meet the desired profile of requirements.
From these boron-containing carbosilanes of the formula (I) may be prepared carbon-rich ceramics which are distinguished by an elevated stability to alkali metals and alkaline earth metals and their compounds and also by an outstanding resistance to oxidation. In addition, the ceramics of the invention are distinguished by high moduli of elasticity and scratch resistance.
The invention therefore relates to boron-containing carbosilanes of the formula (I)
where
R
1
=
where
R
4
=H, C
1
-C
3
-alkyl and/or phenyl,
R
5
=Cl, Br
R
6
, R
7
=Cl, Br, H, C
1
-C
3
-alkyl or phenyl
R
2
=R
1
or Cl, Br,
R
3
=R
5
,
R′=SMe
2
, NMe
2
H
where
n=0 when R
2
=R
1
,
n=1 when R
2
=R
5
.
In a preferred embodiment of the invention, in the boron-containing carbosilanes of the formula (I)
where
R
4
=CH
3
,
R
5
=Cl or Me,
R
6
=Me,
R
7
=R
5
,
and when
R
2
=R
1
,
R
3
is Cl,
and when R
2
is Cl, n=1 and R′ is SMe
2
.
In a further preferred embodiment of the invention, in the boron-containing carbosilanes of the formula (I)
where
R
4
=CH
3
,
R
5
, R
6
and R
7
=Cl
and when
R
2
=R
1
R
3
is Cl,
and when R
2
is Cl, n=1 and R
1
is SMe
2
.
The invention additionally relates to a process for preparing the boron-containing carbosilanes of the invention, in which at least one halogenoalkenesilane of the formula (II)
where
R
4
=H, C
1
-C
3
-alkyl and/or phenyl,
R
5
=Cl, Br,
R
6
, R
7
=independently of one another Cl, Br, H, C
1
-C
3
-alkyl or phenyl,
and m=0 or 1
is reacted with boranes of the formula (III)
H
X
BR
3- x
5
-SMe
2
or H
2-x
BR
x
5
-NHMe
2
where x=2 or 1,
preferably H
x
BR
3-x
5
-SMe
2
where x=2,
in an inert gas atmosphere, for example N
2
, Ar, He,
in an aprotic solvent at temperatures<20° C., preferably 0-10° C.,
in which case the ratio of halogenoalkenesilanes of the formula (II) to boranes of the formula (III) is established by x, that is to say that the compounds of the formulae (II) and (III) are used in accordance with the stoichiometry x.
All of the starting materials coming under the formulae (II) and (III) are commercially available products.
For the purposes of the invention, aprotic solvents are non-halogenated or halogenated aromatic and aliphatic hydrocarbons, preferably toluene, hexane and/or dichloromethane.
In a preferred embodiment of the process of the invention, when x =1, the aprotic solvent is halogenated hydrocarbons.
The reaction of the invention is described by way of example with reference to the following diagram:
The invention further relates to boron-containing carbosilanes of the formula (IV)
where
R
1
=
where
R
4
=H, C
1
-C
3
-alkyl and/or phenyl,
R
5
=Cl, Br, preferably Cl
R
6
, R
7
=independently of one another Cl, Br, H, C
1
-C
3
-alkyl or phenyl, preferably
Cl or methyl
and
R
8
=SiR
9
where R
9
=C
1
-C
3
-alkyl or Cl or
The invention additionally relates to a process for preparing boron-containing carbosilanes of the formula (IV) where R
8
=SiR
9
where R
9
=C
1
-C
3
-alkyl or Cl, preferably R
8
=SiCl
3
, according to which at least one boron-containing carbosilane of the formula (I), in which R
2
=R
1
, and in which R
6
and R
7
independently of one another are Cl, Br, H, C
1
-C
3
-alkyl or phenyl, are reacted in an inert gas atmosphere with Me
3
Si—NH—SiCl
3
at temperatures<70° C., preferably 20 to 40° C.
Me
3
Si—NH—SiCl
3
can be prepared, for example, as described in U.S. Pat. No. 5,233,066.
The reaction of the invention is described by way of example with reference to the diagram below:
The invention additionally relates to a process for preparing boron-containing carbosilanes of the formula (I) where
according to which at least one boron-containing carbosilane of the formula (I), in which R
1
=R
2
, is reacted with Me
3
Si—NH—SiMe
3
at temperatures <70°

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