Polycarbosilanes and process for preparing them

Polycarbosilanes having Si units which are linked by phenyl-substituted methylene bridges or by partially or completely fluorinated hydrocarbon bridges. These polycarbosilanes are obtained by a Grignard polycondensation reaction. If phenyl substituents are present on the silicon atoms of the polycarbosilanes, they may also optionally be exchanged for halogen atoms in additional halogenating reactions, so that polycarbosilanes can be prepared which are both fluorinated on the hydrocarbon bridges and halogenated (particularly fluorinated) on the silicon atoms.

BACKGROUND OF THE INVENTION 
The invention relates to novel polycarbosilanes and to processes for 
preparing them. 
Polycarbosilanes are polymers having a backbone structure made from the 
elements carbon and silicon, in which in general Si groups and hydrocarbon 
groups are present alternately. The backbone structure of polycarbosilanes 
of this type consists, for example, of repeating structural units 
corresponding to the formula 
##STR1## 
wherein R.sup.0 represents, for example, a hydrocarbon substituent. 
According to known preparation processes polycarbosilanes of this type are 
obtained by thermally decomposing monosilanes, such as for example 
tetramethylsilane, trimethylchlorosilane, dimethyldichlorosilane or 
methyltrichlorosilane, to convert them into mixtures of various 
polycarbosilanes. A further known process for preparing polycarbosilanes 
of this type starts from polysilanes in which at least one of the two 
substituents on the silicon atom is a methyl group. These polysilanes are 
converted to the polycarbosilane by pyrolysis at temperatures of 
350.degree. to 450.degree. C. During the pyrolysis or thermal conversion, 
methylene groups are formed from some of the methyl substituents and are 
inserted between adjacent Si atoms of the polysilane, and a hydrogen atom 
remains on the silicon atom. Pyrolyses of this type proceed through a 
free-radical reaction mechanism. 
Polycarbosilanes, in which the Si atoms are linked by bridges of organic 
aromatic groups, or preferably heteroaromatic groups, such as 
pyrrol-2,5-diyl or thiophen-2,5-diyl, are known from German published 
application No. 36 34 281. The object of this application is to prepare 
conductive polysilanes by additional chemical or electrochemical doping. 
It is known from British patent specification No. GB 896,301 to convert 
monomeric diaryldihalosilanes and p-phenylene dimagnesium bromide via a 
Grignard reaction to polycarbosilanes in which the Si atoms are linked by 
phenylene bridges. Thermoplastic, heat-curable resins are obtained. 
It is known to prepare copolymers made from silane monomer units and olefin 
units in the presence of potassium in tetrahydrofuran in accordance with 
Schilling and Williams (Schilling, C. L., Jr.; Williams, T. C. (Union 
Carbide Corp., Tarrytown, N.Y., USA). Report 1983, TR-83-2; Order No. 
AD-A141558, 15 pp. (Eng). Avail. NTIS. From Gov. Rep. Announce. Index 
(U.S.) 1984, 84(18), 48; see also Chemical Abstracts 101:196821q). 
Methyltrichlorosilane, dimethyldichlorosilane or methyldichlorohydrosilane 
are reacted as silane monomers with styrene or isoprene, wherein in the 
case of styrene, the Si units are linked by phenyl-substituted ethylene 
units. In the case of isoprene, the Si units are linked by the 
corresponding methyl-substituted C.sub.4 -alkylene chain which has a 
further double bond. In two additional examples, isoprene is reacted with 
methylchloro-methyldichlorosilane or with a mixture of 
vinylmethyldichlorosilane and trimethylchlorosilane. 
Halogenated polycarbosilanes are known from U.S. Pat. No. 4,761,458. These 
halogenated polycarbosilanes are prepared from polycarbosilanes which 
carry at least 0.1 wt % of SiH groups and which are converted to 
chlorinated or brominated polycarbosilanes by reacting with chlorinating 
or brominating reagents in a free-radical reaction, whereby SiCl or SiBr 
groups are formed from the SiH groups. As educts for the halogenation 
reaction, U.S. Pat. No. 4,761,458 uses conventional polycarbosilanes of 
the type described above which are substituted by lower alkyl groups and 
are known from the state of the art. These were prepared by pyrolysis of, 
for example, polydimethylsilane (--(CH.sub.3).sub.2 Si--).sub.n. 
Furthermore, prepolymers made from ceramic-forming elements for the 
preparation of ceramic polymer materials are known from German published 
application no. DE 36 16 378. In these compounds easily cleavable elements 
are partly replaced by elements which are difficult to cleave, such as 
fluorine or completely fluorinated hydrocarbon groups. Hydrogen is 
mentioned there as an easily cleavable element. The exemplary embodiment 
of the published German application also starts from a conventional 
polycarbosilane of the type described above, which is known from the state 
of the art and was prepared by pyrolysis of polydimethylsilane 
(--(CH.sub.3).sub.2 Si--).sub.n. Fluorine is introduced into this 
polycarbosilane by electrofluorination using tetraethylammonium fluoride 
or by direct (free radical) fluorination using elemental fluorine. In this 
case, in addition to the conversion of SiH groups into SiF groups, 
fluorine atoms are also introduced into the methyl substituents on the 
silicon atoms and into the methylene bridges of the Si--CH.sub.2 --Si 
backbone of the polycarbosilane. 
Indeed, a number of polycarbosilanes and also some halogenated 
polycarbosilanes, and processes for their preparation, are already known 
in the state of the art. Yet certain types of polycarbosilane could not be 
prepared in the prior art. For example, it has not heretofore been 
possible to prepare polycarbosilanes in which the Si atoms are linked by 
phenyl-substituted methylene bridges or by defined aliphatic hydrocarbon 
bridges partially or completely substituted by fluorine. Likewise, it has 
not heretofore been possible to prepare polycarbosilanes which have a 
defined structure and carry fluorine substituents on the Si atoms, and in 
which the Si atoms carry linking, aliphatic hydrocarbon bridges. 
Furthermore, the polycarbosilanes known from the state of the art, in 
particular those obtained pyrolytically, and halogenated polycarbosilanes 
prepared therefrom by free radical halogenation, are subject to a series 
of disadvantages with regard to the properties of the products and the 
processes by which they are prepared. The disadvantageous properties of 
these known polycarbosilanes are attributable to the unfavorable effects 
of their pyrolytic preparation, by means of which the basic structure and 
the maximum attainable degree of purity for the polycarbosilanes and also 
the halogenated derivative products is already essentially predetermined. 
Hence the known halogenated and non-halogenated polycarbosilanes are 
non-uniform products which have an irregular SiC backbone and are 
accompanied by more or less volatile decomposition products, the identity 
of which depends on the preparation method. However, additional measures 
for limiting the products to a product spectrum more favorable for the 
intended further use (for example purification and/or separation by 
fractional crystallization or fractional distillation) are work, energy 
and cost intensive. The ease with which halogen atoms are introduced into 
the polycarbosilanes of the prior art also depends directly on the 
presence of SiH groups in these polycarbosilanes, since only these SiH 
groups may be converted to SiHal groups (Hal=halogen) using the known 
processes for preparing halogenated polycarbosilanes. However, the 
formation of SiH groups in the pyrolytic preparation of polycarbosilanes 
is difficult to control, and this also has a direct effect on the 
properties of halogenated polycarbosilanes prepared therefrom. 
Furthermore, the degree and location of halogenation also is difficult to 
control in the preparation of known halogenated polycarbosilanes which is 
carried out under free radical halogenation conditions. Indeed, the SiH 
groups preferably react initially to form SiHal groups, yet there are 
considerable side reactions, particularly when long reaction times and 
slightly intensified reaction conditions are used. Hence, in addition to 
the required halogenation in the SiH groups, nonspecific halogenation 
reactions also occur in the hydrocarbon substituents, at silicon atoms, or 
in the methylene bridges of the polycarbosilane used. Furthermore, the 
free radical reaction conditions may lead to splitting reactions in the 
Si-C-Si backbone of the polycarbosilane, as a result of which the 
polycarbosilane and/or the halogenated polycarbosilane which is used may 
be partly degraded into undesirable fragments and volatile, low molecular 
weight compounds during the reaction. 
SUMMARY OF THE INVENTION 
It was therefore the object of the present invention to provide novel 
halogenated and non-halogenated polycarbosilanes which avoid the 
disadvantages of the prior art. 
Another object of the invention is to provide novel polycarbosilanes having 
advantageous properties which can easily be adapted optimally to 
particular intended uses. 
It is also an object of the invention to provide novel polycarbosilanes 
which heretofore have not been accessible in the prior art. 
A further object is to provide simpler and more readily controllable 
processes for preparing such novel halogenated and non-halogenated 
polycarbosilanes. 
These and other objects are achieved by means of the non-halogenated and 
halogenated polycarbosilanes of the invention and the processes of the 
invention for the preparation of these polycarbosilanes.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The invention relates to polycarbosilanes composed of structural units 
corresponding to the formula I: 
##STR2## 
wherein R.sup.1 represents hydrogen, alkyl, cycloalkyl, aryl, arylalkyl or 
halogen, it being possible for R.sup.2 to also have different meanings in 
various units of one and the same polycarbosilane, 
R.sup.2 represents alkyl, cycloalkyl, aryl, arylalkyl or halogen, it being 
possible for R.sup.2 to also have different meanings in various units of 
one and the same polycarbosilane, 
R.sup.3 represents fluorine or phenyl, it being possible for R.sup.3 to 
also have different meanings in various units of one and the same 
polycarbosilane, 
R.sup.4 represents hydrogen, fluorine or phenyl, it being possible for 
R.sup.4 to also have different meanings in various units of one and the 
same polycarbosilane, 
n represents the numeral 1 if R.sup.3 and/or R.sup.4 represent phenyl, and 
n represents an integer from 1 to 6 if R.sup.3 represents fluorine and 
R.sup.4 represents hydrogen or fluorine, it being possible for n to also 
have different meanings in various units of one and the same 
polycarbosilane, and 
p represents an integer from n to 2n-1, it being possible for p to also 
have different meanings in various units of one and the same 
polycarbosilane. 
In one embodiment of the invention, the polycarbosilanes are composed of a 
number of different structural units corresponding to formula I arranged 
next to one another. These structural units may differ with regard to the 
groups R.sup.1, R.sup.2, R.sup.3 and/or R.sup.4, and with regard to the 
values n and/or p. The structural units of formula I which form the 
polycarbosilane are usually combinations of not more than a maximum of 
three R.sup.1 R.sup.2 Si units having different substituents and of not 
more than a maximum of three different (C.sub.n R.sub.p.sup.3 
R.sub.2n-p.sup.4) units. 
In one advantageous variant, each of the bridge substituents R.sup.3 and 
R.sup.4, and each of the values n and p in all structural units of formula 
I of the polycarbosilane has only a single meaning. For example, this 
provides polycarbosilanes in which the structural units of formula I are 
formed from combinations of not more than three R.sup.1 R.sup.2 Si units 
having different substituents and only one (C.sub.n R.sub.p.sup.3 
R.sub.2n-p.sup.4) unit. 
In another advantageous variant, each of the Si substituents R.sup.1 and 
R.sup.2 in all structural units of formula I of the polycarbosilane has 
only a single meaning. Polycarbosilanes composed of structural units of 
formula I are then provided in which all R.sup.1 R.sup.2 Si units are 
identical. 
In a preferred variant there is only one single type of structural unit of 
formula I present in the polycarbosilanes of the invention. The R.sup.1 
R.sup.2 Si units and the (C.sub.n R.sub.p.sup.3 R.sub.2n-p.sup.4) units 
are then identical in all structural units of the polycarbosilane composed 
of units of formula I. 
R.sup.1 may be hydrogen in the polycarbosilanes of the invention composed 
of structural units of formula I. R.sup.2 then represents saturated or 
unsaturated alkyl, cycloalkyl, aryl, arylalkyl or halogen. 
In the polycarbosilanes of the invention composed of structural units of 
formula I, the groups R.sup.1 and/or R.sup.2 may represent alkyl. As used 
herein the term "alkyl" refers to saturated or unsaturated, straight-chain 
or branched alkyl groups, which may optionally be further substituted by 
inert substituents. Examples of suitable alkyl groups include C.sub.1 to 
C.sub.16 alkyl groups, such as, for example, methyl, ethyl, propyl, butyl, 
pentyl, hexyl, octyl, dodecyl, hexadecyl, isopropyl, isobutyl, tertiary 
butyl, vinyl or allyl. C.sub.1 to C.sub.6 alkyl groups are particularly 
suitable. Lower alkyl groups having 1 to 4 carbon atoms, in particular 
methyl, ethyl, propyl, butyl and vinyl, are preferred. 
In the polycarbosilanes of the invention composed of structural units of 
formula I, the groups R.sup.1 and/or R.sup.2 may represent cycloalkyl. As 
used herein the term "cycloalkyl" refers to a saturated or unsaturated 
cycloalkyl group optionally further substituted by inert substituents. 
Examples of suitable cycloalkyl groups include cyclopentyl, cyclohexyl, 
cyclopentenyl or cyclohexenyl. 
In the polycarbosilanes of the invention composed of structural units of 
formula I, the groups R.sup.1 and/or R.sup.2 may represent aryl. As used 
herein the term "aryl" refers to an aromatic hydrocarbon group which may 
be unsubstituted or which may be substituted by inert substituents. 
Examples of suitable aryl groups include phenyl, naphthyl, p-diphenyl, or 
alkylaryl groups such as tolyl, ethylphenyl or propylphenyl. Phenyl groups 
are preferred. 
In the polycarbosilanes of the invention composed of structural units of 
formula I, the groups R.sup.1 and/or R.sup.2 may represent arylalkyl. 
Examples of suitable arylalkyl groups include phenylmethyl and 
phenylethyl. 
In the polycarbosilanes of the invention composed of structural units of 
formula I, the groups R.sup.1 and/or R.sup.2 may represent halogen. In 
particular, in this context the term "halogen" refers especially to 
chlorine, bromine, or fluorine. 
In a sub-variant of the invention, the polycarbosilanes are characterized 
in that in the structural units of formula I, the group R.sup.3 represents 
phenyl; the other groups R.sup.1, R.sup.2 and R.sup.4, and the value p 
have the meanings given above, and n=1. In an advantageous embodiment of 
this sub-variant, the group R.sup.1 is hydrogen or also phenyl. 
Polycarbosilanes are then provided in which the R.sup.1 R.sup.2 Si units 
are linked to one another by phenylmethylene or diphenylmethylene bridges. 
Examples of phenyl-substituted methylene bridges of this type include 
phenylmethylene (--CHPh--), diphenylmethylene (--CPh.sub.2) and 
phenylfluoromethylene (--CFPh--). In this variant of the invention the 
groups R.sup.1 and/or R.sup.2 in the Si units may have the above-mentioned 
meanings, especially hydrogen, lower alkyl having 1 to 4 carbon atoms 
(including unsaturated lower alkyl such as, for example vinyl), phenyl or 
halogen. 
In another preferred sub-variant of the invention, the polycarbosilanes of 
the invention are characterized in that in the structural units of formula 
I, the group R.sup.3 represents fluorine; the group R.sup.4 represents 
hydrogen or fluorine, preferably fluorine; and the other groups R.sup.1 
and R.sup.2 and the values n and p have the meanings given above. 
Polycarbosilanes according to the invention are then provided in which the 
R.sup.1 R.sup.2 Si units are linked by partially fluorinated or 
perfluorinated hydrocarbon bridges containing 1 to 6 carbon atoms. In a 
preferred group of these polycarbosilanes, the R.sup.1 R.sup.2 Si units of 
the polycarbosilane are linked by partially or completely fluorinated 
hydrocarbon bridges containing 1 to 3 carbon atoms, i.e. polycarbosilanes 
composed of the structural units of the formula I are provided in which n 
represents an integer from 1 to 3, and the groups R.sup.1, R.sup.2, 
R.sup.3 and R.sup.4 and the value p have the foregoing meanings. Preferred 
hydrocarbon bridges of this sub-variant of the polycarbosilanes of the 
invention are the perfluorinated hydrocarbon bridges in which R.sup.3 and 
R.sup.4 represent fluorine. Examples of suitable partially or completely 
fluorinated hydrocarbon bridges include bridges corresponding to the 
formula (--C.sub.n F.sub.p H.sub.2n-p)-- or to the formula (--CF.sub.2 
--).sub.n, example monofluoromethylene, difluoromethylene, 
difluoroethylene, trifluoroethylene, tetrafluoroethylene, 
trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, 
hexafluoropropylene and the like, up to and including 
dodecafluorohexylene. 
The groups R.sup.1 and/or R.sup.2 may have the meanings given further above 
in the polycarbosilanes having partially fluorinated or perfluorinated 
hydrocarbon bridges. However, in a preferred embodiment of the sub-variant 
of the polycarbosilanes of the invention having partially or completely 
fluorinated hydrocarbon bridges, the groups R.sup.1 and R.sup.2 in the 
structural units of formula I are characterized in that the group R.sup.1 
represents hydrogen, lower alkyl (optionally including unsaturated lower 
alkyl), phenyl or halogen, and the group R.sup.2 represents lower alkyl 
(optionally including unsaturated lower alkyl), phenyl or halogen. As used 
herein the term "lower alkyl" refers to alkyl groups having 1 to 4 carbon 
atoms, in particular methyl, ethyl, propyl, butyl or vinyl. In this 
embodiment of the invention, for example, polycarbosilanes having 
partially or completely fluorinated hydrocarbon bridges are then present 
which contain dimethylsilylene, diethylsilylene and the like, 
methylethylsilylene, methylvinylsilylene, ethylvinylsilylene and the like, 
diphenylsilylene, methylphenylsilylene, ethylphenylsilylene and the like, 
methylhalosilylene, ethylhalosilylene and the like, phenylhalosilylene or 
dihalosilylene units as R.sup.1 R.sup.2 Si units. 
In a preferred embodiment, the polycarbosilanes of the invention having 
partially or completely fluorinated hydrocarbon bridges are characterized 
in that in the structural units of formula I, the group R.sup.2 represents 
halogen, preferably chlorine, bromine or fluorine, R.sup.1 having the 
aforementioned meaning hydrogen, lower alkyl (optionally including 
unsaturated lower alkyl), phenyl or halogen, and the groups R.sup.3 and 
R.sup.4 and the values n and p have the meanings given above for 
polycarbosilanes having partially or completely fluorinated hydrocarbon 
bridges. Si-halogenated or mixed Si-halogenated polycarbosilanes having 
partially or completely fluorinated hydrocarbon bridges are then provided 
which carry the same or different halogen atoms in the R.sup.1 R.sup.2 Si 
units. Examples of halosilylene units of this type include 
methylchlorosilylene, methylbromosilylene, methylfluorosilylene, 
ethylchlorosilylene, ethylbromosilylene, ethylfluorosilylene and the like, 
phenylchlorosilylene, phenylbromosilylene, phenylfluorosilylene and also 
dihalosilylene, for example difluorosilylene. 
In preferred polycarbosilanes of the variant having partially or completely 
fluorinated hydrocarbon bridges and halogenated Si units, the halogen atom 
in the Si unit is bromine or fluorine, particularly preferably fluorine. 
Preferred examples of these halogenated polycarbosilanes are formed, for 
example, from methylbromosilylene units and tetrafluoroethylene units or 
from methylfluorosilylene units and tetrafluoroethylene units. 
The invention also includes mixed halogenated polycarbosilanes, i.e. 
polycarbosilanes in which the halogen atoms chlorine, bromine and/or 
fluorine may be present adjacent one another. 
In a further variant of the invention the polycarbosilanes may be 
cross-linked by branching groups corresponding to the formula II and/or to 
the formula III: 
##STR3## 
wherein A represents a group C.sub.n R.sub.p.sup.3 R.sub.2n-p.sup.4, in 
which the groups R.sup.3 and R.sup.4 and the values n and p have the above 
meanings, and 
R represents hydrogen or alkyl, cycloalkyl, aryl or arylalkyl having the 
above meanings. 
The polycarbosilanes of the invention may be cross-linked by proportions of 
up to 50% of the branching groups II and/or III. 
The polycarbosilanes of the invention composed of structural units of 
formula I may have different end groups. The end groups may be halogen, 
alkyl, cycloalkyl, arylalkyl, aryl, alkoxy or hydroxy groups. Examples of 
suitable end groups include chlorine, bromine, fluorine, methyl, phenyl, 
methoxy and hydroxy. 
The polycarbosilanes of the invention are solid or liquid, wax-like, 
viscous or solid materials having a structure in which essentially every 
silicon atom is bonded only to carbon atoms. These polycarbosilanes are 
characterized by a maximum Si--Si bond proportion of only 5%. In the 
examples of the invention the Si--Si bond proportion is even less than 1%. 
The number of structural units of formula I which form the polycarbosilanes 
of the invention is generally between 10 and 500, preferably between 30 
and 150. The polycarbosilanes thus have average molecular weights in the 
range from 600 to 300,000 g/mole, preferably in the range from 700 to 
30,000 g/mole. 
The invention also relates to a process for preparing polycarbosilanes 
composed of structural units of formula I, wherein 
a) for preparing polycarbosilanes composed of structural units 
corresponding to formula Ia: 
##STR4## 
wherein R.sup.1a represents hydrogen, alkyl, cycloalkyl, aryl or 
arylalkyl, whereby R.sup.1a can have the same or different meanings in 
various units of one and the same polycarbosilane, 
R.sup.2a represents alkyl, cycloalkyl, aryl or arylalkyl, whereby R.sup.2a 
can have the same or different meanings in various units of one and the 
same polycarbosilane, 
R.sup.3 represents fluorine or phenyl, whereby R.sup.3 can have the same or 
different meanings in various units of one and the same polycarbosilane, 
R.sup.4 represents hydrogen, fluorine or phenyl, whereby R.sup.4 can have 
the same or different meanings in various units of one and the same 
polycarbosilane, 
n represents the numeral if R.sup.3 and/or R.sup.4 represent phenyl, or n 
represents an integer from 1 to 6 if R.sup.3 represents fluorine and 
R.sup.4 represents hydrogen or fluorine, whereby n can have the same or 
different values in various units of one and the same polycarbosilane, and 
p represents an integer from n to 2n-1, whereby p can have the same or 
different meanings in various units of one and the same polycarbosilane, 
said process comprises the steps of: reacting a dihalosilane corresponding 
to the formula IV 
##STR5## 
with a dibromide compound corresponding to the formula V 
EQU Br--(C.sub.n R.sub.p.sup.3 R.sub.2n-p.sup.4)--Br (V) 
wherein 
X represents the halogens chlorine, bromine or iodine, preferably chlorine 
or bromine, and 
R.sup.1a, R.sup.2a, R.sup.3, R.sup.4, n and p have the meanings given 
above, in a Grignard polycondensation reaction with magnesium metal, or 
b) for preparing polycarbosilanes composed of structural units 
corresponding to the formula Ib 
##STR6## 
wherein R.sup.1 represents hydrogen, alkyl, cycloalkyl, aryl, arylalkyl or 
halogen, whereby R.sup.1 can have the same or different meanings in 
various units of one and the same polycarbosilane, 
Hal represents halogen, preferably chlorine, bromine or fluorine, whereby 
Hal can have the same or different meanings in various units of one and 
the same polycarbosilane, and 
R.sup.3, R.sup.4, n and p have the above meanings, 
said process comprising the steps of: 
ba) reacting a polycarbosilane composed of structural units corresponding 
to the formula Ic: 
##STR7## 
wherein R.sup.1 has the same meaning as R.sup.1, and 
R.sup.3, R.sup.4, n and p have the above meanings, 
with at least one halogenating reagent under polar or ionic reaction 
conditions, optionally in the presence of a Lewis acid, in such a way that 
the phenyl substituents Ph in the structural units of formula Ic, and 
optionally in the groups R.sup.1 =Ph, are partially or completely 
exchanged for halogen atoms, and 
bb) optionally thereafter completely or partially exchanging the halogen 
introduced into the polycarbosilane in step ba) under polar or ionic 
reaction conditions for another halogen atom. 
In accordance with the invention, in process variant a) for preparing 
polycarbosilanes composed of structural units of formula Ia, at least one 
dihalosilane corresponding to formula IV and at least one 
dibromohydrocarbon of formula V are reacted with each other in a Grignard 
polycondensation reaction in the presence of magnesium and in the presence 
of an organic solvent suitable for Grignard reactions. 
In the dihalosilanes of formula IV used in process variant a), R.sup.1a may 
be hydrogen. R.sup.2a then represents alkyl, cycloalkyl, aryl or 
arylalkyl. 
In the dihalosilanes of formula IV used in process variant a), one or both 
groups R.sup.1a or R.sup.2a may represent alkyl. In this context the term 
"alkyl" has the meaning given above, namely a saturated or unsaturated, 
straight-chain or branched alkyl group which optionally may be further 
substituted by inert groups. Examples of suitable alkyl groups include, in 
particular, the C.sub.1 to C.sub.16 alkyl groups mentioned above, but 
especially the preferred C.sub.1 to C.sub.6 alkyl groups. Lower alkyl 
groups, including unsaturated lower alkyl groups, having 1 to 4 carbon 
atoms are particularly preferred. 
In the dihalosilanes of formula IV used in process variant a), one or both 
groups R.sup.1a or R.sup.2a may represent cycloalkyl. In this context the 
term "cycloalkyl" refers to the meaning given above of a saturated or 
unsaturated cycloalkyl group optionally further substituted by an inert 
substituent. Examples of suitable cycloalkyl groups include cyclopentyl, 
cyclohexyl or cyclopentenyl, cyclohexenyl. 
In the dihalosilanes of formula IV used in process variant a), one or both 
groups R.sup.1a or R.sup.2a may represent aryl. In this context "aryl" 
refers to the meaning given above of an aromatic hydrocarbon group which 
is unsubstituted or has inert substituents. Examples of suitable "aryl" 
groups include phenyl, naphthyl, p-diphenyl, or alkylaryl groups, such as 
tolyl, ethylphenyl or propylphenyl. Phenyl is most preferred as an aryl 
group. 
In the dihalosilanes of formula IV used in process variant a), one or both 
groups R.sup.1a or R.sup.2a may represent arylalkyl. Examples of suitable 
arylalkyl groups include phenylmethyl or phenylethyl. 
The dichlorosilanes or dibromosilanes are particularly suitable as 
dihalosilanes for process variant a) of the invention. Examples of 
particularly suitable dihalosilanes include dimethyldichlorosilane, 
dimethyldibromosilane, diethyldichlorosilane, diethyldibromosilane, 
methylphenyldichlorosilane, methylphenyldibromosilane, 
diphenyldichlorosilane, diphenyldibromosilane, methylvinyldichlorosilane, 
methylhydrogendichlorosilane, and comparable dihalosilanes. 
In the dibromohydrocarbons of formula V used in process variant a), the 
group R.sup.3 may represent fluorine or phenyl, and the group R.sup.4 may 
represent hydrogen, fluorine or phenyl. Phenyl-substituted dibromomethanes 
and particularly partially or completely fluorinated dibromohydrocarbons 
having 1 to 6 carbon atoms are suitable as dibromohydrocarbons for process 
variant a) of the invention. Examples of suitable phenyl-substituted 
dibromomethanes include phenyldibromomethane and diphenyldibromomethane. 
Examples of preferred and particularly suitable partially or completely 
fluorinated dibromohydrocarbons include compounds corresponding to the 
formula Br-(C.sub.n F.sub.p H.sub.2n-p)--Br or to the formula Br--(C.sub.n 
F.sub.2n)--Br, in which the values n and p have the meanings already given 
above. Predominantly fluorinated dibromohydrocarbons, i.e. compounds 
corresponding to the above formula Br--(C.sub.n F.sub.p H.sub.2n-p)--Br in 
which p&gt;&gt;n and ranges up to a maximum value of 2n-1, are preferred. 
Perfluorinated dibromohydrocarbons corresponding to the formula 
Br--(C.sub.n F.sub.2n)--Br are particularly preferred, such as for example 
dibromodifluoromethane, dibromotetrafluoroethane, 
dibromohexafluoropropane, dibromooctafluorobutane, 
dibromodecafluoropentane or dibromododecafluorohexane. 
The magnesium used in process variant a) of the invention is used as a 
metal in the form of magnesium powder, magnesium filings, magnesium 
granules, or the like. The magnesium metal may be pretreated for use in 
the Grignard reaction by measures known to persons skilled in the art. It 
is recommended, for example, to degrease the magnesium before the 
reaction; to dry the magnesium to remove adhering moisture, and/or to 
partially etch the magnesium, optionally using small amounts of lower 
bromine- or iodine-containing hydrocarbons, such as dibromoethane, 
dibromopropane, diiodopropane and the like, but preferably using elemental 
iodine. The amount of magnesium metal to be used is approximately two 
moles per mole of the dihalosilane used or the dibromohydrocarbon used. 
The dihalosilane and the dibromohydrocarbon are used in the reaction in 
approximately equimolar amounts. 
The organic solvent in which the Grignard polycondensation reaction takes 
place may be any dry solvent which is compatible with Grignard reagents, 
in particular an ether such as diethyl ether, dioxane, tetrahydrofuran and 
the like. 
The Grignard polycondensation reaction of the invention is generally 
carried out in such a way, for example, that the starting compounds, the 
dihalosilane and the dibromohydrocarbon, are initially placed with the 
magnesium, preferably in ether. Tetrahydrofuran is then added dropwise, 
and the exothermic reaction is controlled by adjusting the rate of 
dropwise addition of tetrahydrofuran so that even boiling takes place. For 
good results, dry reaction conditions should be maintained, and the 
reaction should be carried out under a protective gas atmosphere with 
stirring. Suitable protective gases include, for example, nitrogen or 
noble gases such as argon. The temperature attained during the reaction 
depends on the boiling point of the solvent used. When the exothermic 
reaction is completed, stirring of the reaction mixture is usually 
continued at room temperature for a longer period of time to assure that 
the reaction is complete. The reaction is typically carried out within a 
period of 1 to 48 hours. The Grignard reaction mixture may be worked up 
and the resulting polycarbosilane isolated in a known manner for working 
up Grignard reactions. Radicals of unreacted Grignard reagents may be 
decomposed, for example, by adding or pouring the Grignard reaction 
mixture into water, hydrochloric acid, aqueous ammonium chloride solution 
and the like, and the polycarbosilane may then be extracted from the 
reaction mixture using a suitable organic solvent, for example using 
halogenated hydrocarbons, such as methylene chloride, chloroform, carbon 
tetrachloride, or fluorochlorohydrocarbons and recovered by removing the 
solvent in a known manner. 
The process of subvariant a) of the invention makes a simple and generally 
applicable method available for easy preparation of various 
polycarbosilanes. In particular, polycarbosilanes, in which the Si units 
are linked to one another by partially or completely fluorinated 
hydrocarbon bridges can be prepared according to this process. By varying 
the type and number of reactants used, the process of the invention 
permits the preparation of a number of interesting polycarbosilanes which 
have not been accessible in the prior art, particularly polycarbosilanes 
in which the hydrocarbon groups are partially or completely fluorinated. 
In a further variant of the process a) of the invention, it is possible, if 
desired, to effect additional specific cross-linking of the linear 
polycarbosilane chain based on the general structural formula Ia. 
Depending on the degree of cross-linking required, up to 50 mole % of the 
dihalosilane IV used is then replaced by a trihalosilane corresponding to 
the formula RSiX.sub.3, in which X represents halogen, preferably chlorine 
or bromine, and R has the meaning given above for R.sup.1, namely 
hydrogen, alkyl, cycloalkyl, aryl or arylalkyl. The trihalosilane 
RSiX.sub.3 may be mixed directly with the reactant mixture of dihalosilane 
IV, dibromohydrocarbon V and magnesium. Alternatively, it may also be 
added dropwise separately from this reactant mixture. Examples of 
trihalosilanes RSiX.sub.3 which can be used include trichlorosilane, 
methyltribromosilane, methyltrichlorosilane or phenyltrichlorosilane. The 
cross-linked polycarbosilanes described above which additionally contain 
branching groups corresponding to the formula II are obtained by this 
process variant. 
Furthermore, in a further process variant, the linear polycarbosilane 
chains formed of units corresponding to the formula Ia can be cross-linked 
by adding tetrahalosilanes, such as tetrachlorosilane or tetrabromosilane. 
The cross-linked polycarbosilanes also described above, which additionally 
contain branching groups corresponding to the formula III, are obtained in 
this way. 
Moreover, in a further process variant the degree of condensation of the 
chain-like or cross-linked polycarbosilanes to be prepared may be 
controlled by stopping the Grignard condensation by adding condensation 
terminating reagents. Suitable reagents for terminating the condensation 
reaction include monohalosilanes R.sub.3 SiX, in which X represents 
halogen, preferably chlorine or bromine, and R' represents alkyl, 
cycloalkyl, aryl or arylalkyl. Further suitable reagents for terminating 
the condensation reaction include, for example, fluorinated 
monobromohydrocarbons. Specific examples of suitable monohalosilanes 
include trimethylchlorosilane, trimethylbromosilane or 
diphenylmethylchlorosilane. Specific examples of suitable fluorinated 
monobromohydrocarbons include trifluorobromomethane or 
pentafluorobromoethane. 
In order to carry out process variant b) for preparing polycarbosilanes 
composed of structural units corresponding to the formula Ib, 
aryl-substituted polycarbosilanes are reacted as educts for up to several 
hours, optionally in the presence of a Lewis acid as a catalyst, with at 
least one halogenating reagent which reacts in a polar or ionic manner 
under a protective gas atmosphere in an organic solvent which is inert 
under the reaction conditions while substantially excluding water. 
All polycarbosilanes prepared according to process variant a) which carry 
phenyl substituents on the silicon atoms may be used as polycarbosilane 
educts for this purpose. 
Conventional halogenating reagents which react in a polar or ionic manner 
may be used to prepare the polycarbosilanes halogenated at the Si atoms 
according to the invention from the phenyl-substituted polycarbosilanes 
described above. Any halogenating reagents which can only react in a free 
radical manner are therefore excluded. Suitable halogenating reagents for 
the reactions mentioned include hydrohalic acids, such as HBr, HCl or HF; 
ammonium salts of these hydrohalic acids, such as NH.sub.4 Br, NH.sub.4 Cl 
or NH.sub.4 F; acid alkali fluorides, such as sodium hydrogen fluoride 
(NaHF.sub.2 or NaF.multidot.HF) or acid potassium fluorides, such as 
KF.multidot.(HF).sub.n where n=1 to 3; hydrogen fluoride adducts with 
ammonium fluoride, such as NH.sub.4 F.multidot.(HF).sub.n or NH.sub.4 
F.multidot.HF; or further halogenating reagents, such as phosphorus 
pentachloride, antimony pentachloride, antimony trifluoride, arsenic 
trifluoride, titanium tetrafluoride, tin tetrafluoride, copper difluoride, 
zinc difluoride and the like. Halogenating reagents preferred here include 
the hydrohalic acids and ammonium salts thereof, the hydrogen fluoride 
adducts with ammonium fluoride, and the acid alkali fluorides. Indeed, 
elemental halogens may also be used under polar or ionic reaction 
conditions. If some of the phenyl substituents are to be retained in the 
halogenated polycarbosilane, care should be taken in the process to ensure 
that electrophilic, aromatic substitution of hydrogen atoms by halogen 
atoms can also take place in the remaining phenyl substituents (in 
addition to the exchange of phenyl substituents for halogen atoms). On the 
other hand, such electrophilic aromatic substitution in the phenyl 
substituents does not take place when using the other halogenating 
reagents mentioned above. 
The polar or ionic reaction of the halogenating reagent is assured first by 
using halogenating reagents which are themselves already compounds having 
a polar or ionic reaction, such as for example HCl, HF, NH.sub.4 Cl, 
NH.sub.4 F, NH.sub.4 F.multidot.(HF).sub.n, NaF.multidot.HF, 
KF.multidot.(HF).sub.n, PCl.sub.5, SbCl.sub.5, SbF.sub.3, AsF.sub.3, 
TiF.sub.4, SnF.sub.4, CuF.sub.2, ZnF.sub.2, etc. Second, the polar or 
ionic reaction conditions are assured when using halogenating reagents 
which may react both in a polar or ionic as well as a free radical manner 
(for example HBr, halogens), by carrying out the reactions in the presence 
of Lewis acid catalysts. However, the presence of Lewis acid catalysts may 
be advantageous even in reactions using halogenating reagents which 
themselves already react in a polar or ionic manner and which themselves 
are not Lewis acids, for example, in reactions using hydrogen chloride. 
The known electrophilic and catalytically active electron pair acceptor 
compounds of the halogens with the elements boron, aluminum, phosphorus, 
antimony, arsenic, iron, zinc or tin are suitable as Lewis acid catalysts 
for preparing halogenated polycarbosilanes by the process of the 
invention. Examples of suitable Lewis acid catalysts include compounds 
such as BF.sub.3, AlCl.sub.3, AlBr.sub.3, PCl.sub.5, SbCl.sub.5, 
SbF.sub.3, ZnF.sub.2, etc. 
The organic solvent in which the halogenation reactions of process variant 
b) take place may be any solvent in which the polycarbosilanes used as 
educts are soluble and which is compatible with the halogenation reagents 
and the optionally present Lewis acid catalysts. Preferably the organic 
solvent also is a solvent for the halogenated polycarbosilanes to be 
prepared according to the invention. Suitable solvents include, for 
example, hydrocarbons such as benzene, toluene, xylene or paraffins, or 
completely or partially halogenated hydrocarbons such as carbon 
tetrachloride, chloroform, methylene chloride, dichloroethane, 
fluorochlorohydrocarbons or hydrogen-containing fluorochlorohydrocarbons. 
Those solvents which can easily be removed again by distillation after the 
reaction are advantageously used. The amount of solvent may be varied 
within wide limits depending on the practical requirements. 
The halogenation reactions of process variant b) may be carried out readily 
at temperatures of about room temperature. Furthermore, the reactions are 
generally carried out under a suitable protective gas. Suitable protective 
gases include, for example, nitrogen or argon. The degree of halogenation 
of the products may easily be controlled in these reactions, on the one 
hand by selecting the number of exchangeable substituents (for example 
phenyl) in the polycarbosilane educt, or on the other hand by increasing 
or decreasing the reaction time and/or the amount of halogenating reagent 
introduced. 
The reaction is generally carried out in such a way that gaseous 
halogenating reagents are introduced into an anhydrous solution of the 
polycarbosilane, optionally containing catalytic amounts of Lewis acid 
catalyst. If on the other hand, solid halogenating reagents are used, such 
as for example acid alkali fluorides, ammonium fluoride or ammonium 
fluoride-HF adducts, these halogenating reagents are initially introduced 
into the reaction vessel as such (for example in powder form) or suspended 
in a solvent, optionally together with a Lewis acid catalyst. A solution 
of the educt polycarbosilane is then added dropwise. 
When the reaction is completed, the halogenated polycarbosilane may be 
recovered from the reaction mixture by any suitable method. If the 
halogenated polycarbosilane is soluble in the solvent, the other insoluble 
components, for example the Lewis acid catalyst optionally suspended in 
the solvent, can be separated by filtration. The halogenated 
polycarbosilane remaining in the solvent may then optionally be subjected 
to further purification measures and may be isolated by removing the 
solvent. If the halogenated polycarbosilane which forms is insoluble in 
the solution, it may be dissolved using another solvent which is suitable, 
separated from insoluble components by filtration, and isolated by 
removing the solvent. The isolated products may then be additionally 
treated ("dried") in vacuo, and optionally at elevated temperatures, to 
remove any adhering solvent residues. 
Polycarbosilanes halogenated on the Si atoms, both uniformly, i.e. having 
only one type of halogen atom on the Si atoms, and mixed halogenated 
polycarbosilanes, i.e. polycarbosilanes having various halogen atoms on 
the Si atoms, may be obtained according to this process variant b). 
Polycarbosilanes halogenated uniformly on the Si atoms are obtained, for 
example, by reacting a polycarbosilane of the type described above which 
is not halogenated on the Si atoms as a starting compound with a single 
halogenating agent. On the other hand, polycarbosilanes having mixed 
halogens on the Si atoms can also be prepared directly from educt 
polycarbosilanes which are not halogenated on the Si atoms, by reacting 
the polycarbosilanes simultaneously with, for example, two halogenating 
agents carrying different halogen atoms. Polycarbosilanes containing 
chlorine and bromine can, for example, be obtained in this manner using an 
HCl/HBr gas mixture. The reaction conditions in this case are analogous to 
the conditions used in reactions involving only a single halogenating 
reagent. 
Furthermore, it is also possible to prepare polycarbosilanes halogenated 
uniformly on the Si atoms starting from polycarbosilanes already 
halogenated on the Si atoms with a different halogen atom by means of 
complete halogen exchange. For example, chlorine or bromine atoms may 
advantageously be exchanged in this manner for fluorine atoms on the Si 
atoms of the polycarbosilane. On the other hand, if only partial halogen 
exchange is carried out at the Si atoms, a polycarbosilane having mixed 
halogens on the Si atoms is obtained as a product from a starting 
polycarbosilane which was uniformly haloqenated on the Si atoms. Hence, 
for example, Si-chlorine/fluorine-containing polycarbosilanes can be 
prepared from Si-chlorinated polycarbosilanes by partial exchange of the 
Si-chlorine atoms for fluorine atoms. Furthermore, it is also possible to 
convert mixed Si-halogenated polycarbosilanes to other mixed 
Si-halogenated polycarbosilanes. Hence, for example, 
Si-chlorine/fluorine-containing polycarbosilanes can also be prepared in 
this manner from Si-chlorine/bromine-containing polycarbosilanes. In this 
process the reaction may be controlled easily so that initially only the 
Si-bromine atoms are completely exchanged for fluorine atoms, and, in 
contrast, the Si-chlorine atoms are retained in the polycarbosilane. The 
reaction conditions for these Si-halogen exchange reactions are analogous 
to the conditions already described above for the Si-halogenation 
reactions. It is possible using this Si-halogen exchange technique to also 
easily obtain those polycarbosilanes halogenated on the Si atoms which can 
be prepared by direct means (that is without transhalogenation) only with 
difficulty or in unsatisfactory yields. The bromine atom is most 
particularly advantageously suitable as a halogen atom which is to be 
exchanged for a further halogen atom on the Si atoms. 
The fluorinating agents which are particularly suitable for this halogen 
exchange include hydrogen fluoride, ammonium fluoride or adducts of 
hydrogen fluoride with ammonium fluoride, acid alkali fluorides and also 
SbF.sub.3, AsF.sub.3, TiF.sub.4, SnF.sub.4, CuF.sub.2, ZnF.sub.2 etc. The 
ammonium salts, for example NH.sub.4 F.multidot.(HF).sub.n, NH.sub.4 
F.multidot.HF or NH.sub.4 F, are preferred because when they are used, the 
presence of additional Lewis acid catalysts is superfluous. Furthermore, 
the reactions can easily be carried out such that either all chlorine or 
bromine atoms contained in the educt, or only some of the chlorine or 
bromine atoms contained in the educt, are exchanged. Furthermore, it also 
is readily possible to exchange only, for example, the bromine atoms 
partially or completely from chlorine/bromine-containing polycarbosilanes 
without changing the chlorine content. Hence chlorine/fluorine-containing 
polycarbosilanes are obtained when there is complete exchange of bromine 
for fluorine, or polycarbosilanes having mixed halogens on the Si atoms 
and containing fluorine, chlorine and bromine atoms at the same time are 
obtained when the bromine atoms are only partially exchanged. Under more 
intensive reaction conditions, the aryl substituents, which are optionally 
still present in the polycarbosilane, are also completely or partially 
exchanged for fluorine atoms. 
The polycarbosilanes of the invention are distinguished by defined 
properties which can be determined by specifically varying the molecular 
size, the number and type of cross-linking, by appropriately selecting the 
groups R.sup.1, R.sup.2, R.sup.3 and R.sup.4 the values n and p, and by 
the type and content of the halogen atoms. Of the Si-halogenated 
polycarbosilanes, the Si-fluorinated polycarbosilanes are particularly 
advantageous because of their unexpectedly high degree of stability, as a 
result of which they are especially suitable for numerous applications. 
The more reactive Si-bromine-containing products are particularly 
advantageously suitable as educts for halogen exchange reactions and other 
exchange reactions. Polycarbosilanes having partially or completely 
fluorinated hydrocarbon bridges, which produce a broad spectrum of liquid, 
viscous and solid products as a function of the degree of fluorination, 
have particularly advantageous properties. Similar favorable chemical and 
physical properties are also achieved with Si-halogenated, particularly 
Si-fluorine-containing, polycarbosilanes. 
The polycarbosilanes of the invention, particularly the bridge-fluorinated 
and/or Si-fluorinated polycarbosilanes, are suitable as valuable starting 
polymers for preparing silicon carbide ceramics of high technical quality. 
They are also outstandingly suitable for various other technical 
applications, for example as binding materials or coating materials. 
Further possibilities for use include impregnation, treatment of fibers, 
and as working fluids such as hydraulic oils, and other areas of 
application in which conventional polycarbosilanes also are used. 
In contrast to the processes known in the prior art, the process of the 
invention for preparing the polycarbosilanes of the invention, in 
particular the bridge-fluorinated and/or Si-fluorinated polycarbosilanes, 
makes it possible to prepare specific and precisely defined 
polycarbosilanes having any desired composition and consistency, 
particularly compounds which are fluorinated in their hydrocarbon bridges 
and optionally also Si-halogenated polycarbosilanes. The properties of the 
polycarbosilanes of the invention may be modified in a simple and specific 
manner by means of these processes with respect to the type and the degree 
of bridge fluorination and also of Si-halogenation. A number of 
polycarbosilanes, particularly bridge-fluorinated polycarbosilanes, may 
thus be made available which may be adapted in optimum manner to a 
particular intended use by means of specific modifications. 
The invention is described in further detail in the following illustrative 
examples, which are not limiting in scope. Unless otherwise stated, parts 
and percentages given in the examples are understood to refer to parts by 
weight or percentages by weight. All reactions were carried out in 
standard laboratory apparatus. The compounds prepared were analyzed by 
elemental analysis and spectroscopic methods (NMR=nuclear magnetic 
resonance spectroscopy: .sup.1 H-NMR using TMS as standard, .sup.19 F-NMR 
using CCl.sub.3 F as standard); IR=infrared spectroscopy; MS=mass 
spectroscopy. Abbreviations used denote: Ph=phenyl, Me=methyl, Vi=vinyl, 
TMS=tetramethylsilane. 
EXAMPLE 1 
5 to 10 ml of tetrahydrofuran were added dropwise to 0.075 mole of 
diphenyldichlorosilane (18.9 g; 15.3 ml) and 0.075 mole of 
difluorodibromomethane (15.75 g; 6.9 ml) in 100 ml of diethyl ether with 
3.9 g of magnesium filings (previously partially etched using iodine) 
under argon. When the reaction started, a further 30 to 40 ml of 
tetrahydrofuran were added dropwise, and the exothermic reaction which 
proceeded with boiling of the solvent was controlled by adjusting the rate 
of addition of the solvent. When the reaction was completed, the resulting 
reaction mixture was stirred for a further 15 hours at room temperature. 
The reaction mixture was then added to an ammonium chloride solution, 
treated with 250 ml of carbon tetrachloride, and the organic phase was 
separated. The organic phase was then washed using approximately 300 ml of 
water, and the solvent was evaporated. The residue was dried for a further 
2 hours at 110.degree. C. in vacuo. 16.9 g of 
polydiphenylsilyldifluoromethylcarbosilane were obtained as a red, viscous 
liquid. The elemental analysis of this material showed a Si content of 
10.6%. .sup.1 H-NMR analysis: 7.2 ppm (phenyl). .sup.19 F-NMR analysis: 
-140 ppm (CF.sub.2). IR analysis (cm.sup.-1): 3070, 3040 (C--H stretching 
vibration, phenyl); 2960, 2930 (C--H stretching vibration); 1600, 1500 
(C.dbd.C); 1100-1000 and 840-680 (carbosilane backbone vibrations); the CF 
vibration bands coincide with the backbone vibrations. 
EXAMPLE 2 THROUGH EXAMPLE 9 
The following polycarbosilanes were prepared by Grignard polycondensation 
in a manner analogous to Example 1. For this purpose 0.075 mole of a 
dichlorosilane was reacted in each case with 0.075 mole of a 
dibromohydrocarbon. The amount of dichlorosilane reacted in these examples 
was: 18.9 g of diphenyldichlorosilane (Ph.sub.2 SiCl.sub.2); 14.3 g of 
methylphenyldichlorosilane (MePhSiCl.sub.2); 9.6 g of 
dimethyldichlorosilane (Me.sub.2 SiCl.sub.2); 10.5 g of 
vinylmethyldichlorosilane (MeViSiCl.sub.2); 8.6 g of 
methylhydrogendichlorosilane (MeHSiCl.sub.2). The amount of 
dibromohydrocarbon reacted here was: 19.5 g of 
1,2-dibromotetrafluoroethane (BrC.sub.2 F.sub.4 Br); 15.8 g of 
dibromodifluoromethane (CF.sub.2 Br.sub.2). The results which were 
obtained are compiled in the following Table 1: 
TABLE 1 
__________________________________________________________________________ 
Polycarbosilane 
Hydrocarbon 
Dichlorosilane 
Yield 
Exp.*.sup.) 
used used (g) Properties 
__________________________________________________________________________ 
2 CF.sub.2 Br.sub.2 
MePhSiCl.sub.2 
9.3 Brownish, viscous liquid: 11.4% Si. 
.sup.1 H-NMR (ppm): 7.2 (Ph); 0.5 (CH.sub.3). 
.sup.19 F-NMR (ppm): -134; -135 (CF.sub.2). 
IR (cm.sup.-1): 
as in Exp. 1; additionally 1257 
(Si--CH.sub.3 ; stretching 
vibration). 
3 CF.sub.2 Br.sub.2 
Me.sub.2 SiCl.sub.2 
1.7 Brown, viscous liquid 
.sup.1 H-NMR (ppm): 0.5 (CH.sub.3). 
IR (cm.sup.-1): 
2960, 2930 (C--H stretching 
vibration); 1257 (Si--CH.sub.3 ; 
stretching vibration); 1100- 
1000, 840-680 (carbosilane 
backbone vibrations); the CF.sub.2 
vibrations bands coincide with the 
carbosilane backbone vibrations. 
4 CF.sub.2 Br.sub.2 
MeViSiCl.sub.2 
3.7 Brown, viscous liquid: 8.8% Si. 
.sup.1 H-NMR (ppm): 6.2 (Vinyl-H); 0.5 
(CH.sub.3). 
.sup.19 F-NMR (ppm): -135 (CF.sub.2) 
IR (cm.sup.-1): 
as in Exp. 3; additionally 1600, 
1500 (C.dbd.C) 
5 BrC.sub.2 F.sub.4 Br 
Ph.sub.2 SiCl.sub.2 
14.9 
Viscous, brown solid: 13.8% Si. 
.sup.1 H-NMR (ppm): 7.2 (Ph). 
.sup.19 F-NMR (ppm): -140 (CF.sub.2). 
IR (cm.sup.-1): as in Exp. 1. 
6 BrC.sub.2 F.sub.4 Br 
MePhSiCl.sub.2 
10.8 
Reddish brown liquid: 17.0% Si. 
.sup.1 H-NMR (ppm): 7.2 (Ph); 0.5 (CH.sub.3). 
.sup.19 F-NMR (ppm): -134.8 (CF.sub.2) 
IR (cm.sup.-1): as in Exp. 2. 
7 BrC.sub.2 F.sub.4 Br 
Me.sub.2 SiCl.sub.2 
3.7 Brown liquid: 12.6% Si. 
.sup.1 H-NMR (ppm): 0.5 (CH.sub.3) 
.sup.19 F-NMR (ppm): -130 bis -133 (CF.sub.2). 
IR (cm.sup.-1): as in Exp. 3. 
8 BrC.sub.2 F.sub.4 Br 
MeViSiCl.sub.2 
6.6 Brown liquid: 23.5% Si. 
.sup.1 H-NMR (ppm): 6.2 (Vinyl-H): 0.5 
(CH.sub.3). 
.sup.19 F-NMR (ppm): -135, 9 (CF.sub.2). 
IR (cm.sup.-1): as in Exp. 4. 
9 BrC.sub.2 F.sub.4 Br 
MeHSiCl.sub.2 
2.7 Brown liquid: 22.7% Si. 
.sup.1 H-NMR (ppm): 4.7 (SiH): 0.5 (CH.sub.3). 
.sup.19 F-NMR (ppm): -133 (CF.sub.2). 
IR (cm.sup.-1): 
as in Exp. 3; additionally: 2100 
(Si--H stretching 
vibration). 
__________________________________________________________________________ 
*.sup.) Exp. = Example 
EXAMPLE 10 
5 to 10 ml of tetrahydrofuran were added dropwise to 0.075 mole of 
diphenyldichlorosilane (18.9 g; 15.3 ml) and 0.075 mole of benzal bromide 
(Br CHPh; 18.8 g) in 100 ml of diethyl ether with 3.9 g of magnesium 
filings (previously partially etched using iodine) under argon. When the 
reaction started a further 30 to 40 ml of tetrahydrofuran were added 
dropwise, and the exothermic reaction proceeding while the solvent boils 
was controlled by adjusting the rate of addition of the solvent. When the 
reaction was completed, the resulting reaction mixture was stirred for a 
further 15 hours at room temperature. The reaction mixture was then added 
to an ammonium chloride solution, treated with 250 ml of carbon 
tetrachloride, and the organic phase was separated. The organic phase was 
then washed using approximately 300 ml of water, and the solvent was 
subsequently evaporated. The residue was dried in vacuo for a further 2 
hours at 110.degree. C. 17.1 g of a polycarbosilane were obtained as a 
viscous reddish-brown solid. The elemental analysis of this material 
showed a content of 12.0% Si; 76.6% C; and 6.1% H. .sup.1 H-NMR analysis: 
7.2 ppm (phenyl); 3.6 (CH). IR analysis (cm.sup.-1): 3070, 3040 (C--H 
stretching vibration, phenyl); 2960, 2930 (C--H stretching vibration); 
1600, 1500 (C.dbd.C); 1100-1000 and 840-680 (carbosilane backbone 
vibrations). 
EXAMPLE 11 THROUGH EXAMPLE 19 
The following polycarbosilanes were prepared by Grignard polycondensation 
in manner analogous to Example 10. For this purpose 0.075 mole of a 
dichlorosilane was reacted in each case with 0.075 mole of a 
dibromohydrocarbon. The amount of dichlorosilane reacted in these examples 
was: 18.9 g of diphenyldichlorosilane (Ph.sub.2 SiCl.sub.2); 14.3 g of 
methylphenyldichlorosilane (MePhSiCl.sub.2); 9.6 g of 
dimethyldichlorosilane (Me.sub.2 SiCl.sub.2); 10.5 g of 
vinylmethyldichlorosilane (MeViSiCl).sub.2); 8.6 g of 
methylhydrogendichlorosilane (MeHSiCl.sub.2). The amount of 
dibromohydrocarbon reacted here was: 18.8 g of benzal bromide (Br.sub.2 
CHPh); 24.6 g of dibromodiphenylmethane (Br.sub.2 CPh.sub.2). The results 
which were obtained are compiled in the following Table 2: 
TABLE 2 
__________________________________________________________________________ 
Polycarbosilane 
Hydrocarbon 
Dichlorosilane 
Yield 
Exp.*.sup.) 
used used (g) Properties 
__________________________________________________________________________ 
11 Br.sub.2 CHPh 
MePhSiCl.sub.2 
13.3 
Viscous, reddish brown solid: 
13.7% Si; 
75.8% C; 
6.7% H. 
.sup.1 H-NMR (ppm): 7.2 (Ph); 3.0-3.6 (CH); 0.5 
(CH.sub.3). 
IR (cm.sup.-1): 
as in Exp. 10; additionally 1257 (Si-- 
CH.sub.3); stretching vibration). 
12 Br.sub.2 CHPh 
Me.sub.2 SiCl.sub.2 
10.3 
Viscous, brown solid: 
15.9% Si; 69.5% C; 
7.8% H. 
.sup.1 H-NMR (ppm): 7.2 (Ph); 2.3 (CH); 0.4 
(CH.sub.3). 
IR (cm.sup.-1): as in Exp. 11. 
13 Br.sub.2 CHPh 
MeViSiCl.sub.2 
11.3 
Viscous, reddish brown solid: 
16.5% Si; 
71.1% C; 
7.4% H. 
.sup.1 H-NMR (ppm): 
7.2 (Ph); 5.8 (Vinyl-H): 2.5 
(CH): 0.5 (CH.sub.3). 
IR (cm.sup.-1): as in Exp. 11. 
14 Br.sub.2 CHPh 
MeHSiCl.sub.2 
7.1 Viscous, dark red solid: 
20.3% Si; 59.9% C; 
6.3% H. 
.sup.1 H-NMR (ppm): 
7.2 (Ph); 4.5 (SiH); 2.0 (CH); 
0.3 (CH.sub.3). 
IR (cm.sup.-1): 
as in Exp. 11; additionally: 2100 
(Si--H, stretching vibration). 
15 Br.sub.2 CPh.sub.2 
Ph.sub.2 SiCl.sub.2 
24.8 
Yellow solid: 7.8% Si. 
.sup.1 H-NMR (ppm): 7.2 (Ph). 
16 Br.sub.2 CPh.sub.2 
MePhSiCl.sub.2 
20.4 
Yellowish brown solid: 8.5% Si. 
.sup.1 H-NMR (ppm): 7.2 (Ph); 0.5 (CH.sub.3). 
17 Br.sub.2 CPh.sub.2 
Me.sub.2 SiCl.sub.2 
7.5 Brown solid: 7.5% Si. 
.sup.1 H-NMR (ppm): 7.2 (Ph); 0.5 (CH.sub.3). 
18 Br.sub.2 CPh.sub.2 
MeHSiCl.sub.2 
3 Brown solid 
19 Br.sub.2 CPh.sub.2 
MeViSiCl.sub.2 
8 Brownish yellow solid 
__________________________________________________________________________ 
*.sup.) Exp. = Example 
EXAMPLE 20 
15 g of polymethylphenylsilyltetrafluoroethylene carbosilane 
(--SiMePh--C.sub.2 F.sub.4 --).sub.n from Example 6 were dissolved in 400 
ml of dry benzene, and 1.3 g of aluminum bromide were added. Hydrogen 
bromide was passed through the solution over a period of 30 hours at room 
temperature. When the reaction was completed, aluminum bromide was 
filtered out, benzene was distilled off, and the remaining solid was dried 
in vacuo at 100.degree. C. 12.8 g of a brown, highly viscous Br-containing 
polycarbosilane were obtained. The elemental analysis of this material 
showed a content of 23.5% Si and 32.4% Br. .sup.1 H-NMR (ppm): 0.5 
(CH.sub.3); very weak signal at 7.2 (=slight residue of unexchanged phenyl 
groups). .sup.19 F-NMR (ppm): -126.7 to --136.3 (CF.sub.2). 
EXAMPLE 21 
A solution of 6.3 g of the brominated polycarbosilane obtained in Example 
20 in 200 ml of chloroform under a protective gas atmosphere was added 
dropwise at room temperature with stirring to 10 g of ammonium fluoride 
(previously dried in vacuo at 60.degree. C.) and 100 ml of chloroform also 
under a protective gas atmosphere. After a reaction time of 2 days, 75 ml 
of water were added. The organic phase was then separated, filtered, the 
solvent was evaporated, and the remaining residue was dried in vacuo at a 
maximum of 80.degree. C. Four grams of a brown, viscous 
fluorine-containing polycarbosilane was obtained. The elemental analysis 
of this material showed a content of 26.4% Si; 27.6% C; 4.8% H; 50.4% F. 
.sup.1 H-NMR (ppm): 0.5 (CH.sub.3); only very weak signal at 7.2(=small 
content of residual phenyl groups). .sup.19 F-NMR (ppm): -128.0 to -137.0 
(CF.sub.2). 
The foregoing description and examples have been set forth merely to 
illustrate the invention and are not intended to be limiting. Since 
modifications of the described embodiments incorporating the spirit and 
substance of the invention may occur to persons skilled in the art, the 
invention should be construed broadly to include all variations falling 
within the scope of the appended claims and equivalents thereof.