Thermolysis polysilane

To see if silacyclobutenes (28) would react in the same manner as the alkynyl-polysilanes (1) and respond similarly to steric differences, compounds 28a and b were heated in the presence of NiCl2(PEt3)2 and PTMSA (Scheme 9). " Compound 28a gave silole 20a in 94% yield,but the only isolable products from the thermolysis of 28b were 26 (51%) and 27b (36%). The products from the thermolysis of silacyclopropene 28b were very similar to that for alkynylsilane lb, but for some reason there were many fewer products for the thermolysis of 28a than for alkynylsilane la. These results suggest that the more sterically hindered lb... 

Tellurium sources, 22-24 Thermodynamics in cyclo-oligomerization, 185-186 butadiene insertion, 187-188 reductive elimination, 193, 194 selectivity control, 212 polysilane isomerisation, 158-160 see also Stability Thermolysis, 135, 136, 158 THF (tetrahydrofuran), 97, 150, 153 Thio-Wittig reaction, 37 Tin, 121... 

TABLE 3. Silenes synthesized by photolysis or thermolysis of acyl di- or polysilanes... 

For some uses it is important to form bonds that link different polysilane chains, to transform soluble, meltable polysilanes into insoluble resins. This process is vital if the polysilanes are to be used as precursors to silicon carbide ceramics, since, if cross-linking is not carried out, most of the polymer is volatilized before thermolysis to silicon carbide can take place. Several methods have therefore been developed to bring about cross-linking of polysilanes.109 110... 

Both 1,2-dimethoxytetramethyldisilane and 1,3-dimethoxyhexamethyl-trisilane also undergo thermolysis at higher temperatures (225° and 175° C, respectively) to give dimethyldimethoxysilane and the homologous series of ,a>-dimethoxypermethylated polysilanes. In contrast to the base-catalyzed... 

The initial polysilane is rearranged to a polycarbosilane by thermolysis at 743 K. The resulting polymer has no well-defined structure. The use of polysilazanes, having a -[RjSi-NH]- structural unit, allowed the production of mixed SiC/Si3N4 ceramics.12 By a variation of the processing conditions, both compounds can be selectively... 

Applications. The polysilazanes have not been studied as extensively as the polysilanes, and the applications of these polymers are just beginning to be developed. One of the most important applications is thermolysis to... 

Irradiation or thermolysis of polysilane dimers a yields the corresponding silyl radicals b (Scheme 1, Eq. 2). 

Polysilanes are produced from thermolysis of polymeric mercury compounds, obtained from diorganosilanes and t-BujHg ... 

In 1966, Atwell and Weyenberg studied the thermolysis of methoxy-substituted polysilanes to give silylenes such as SiMc2 and observed products as shown in equation (90) which could be attributed to the insertion of the silylene... 

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