Formation of Carbosilanes

The formation of tri- and especially tetrasilanes which are already branched (tertiary Si-units) as the first reaction products (described elsewhere [4]) suggests the appearance of intermediate silylene species which could enter in insertion reactions of Si-Si as well as Si-Cl bonds. The tri- and tetrasilanes undergo thermal crosslinking reactions at reaction temperatures of 165-250 °C. In addition dehydrochlorination reactions initiated by acid H-abstraction of methyl groups cause the formation of carbosilane (methylene) units in the polymer framework. Table 1 shows the gross compositions of poly(methylchlorosilanes) which are determined by the reaction temperature. 

In investigating the pyrochemical formation of carbosilanes from Si(CH3)4 with decomposition times of a few minutes, separation of silicon is almost completely suppressed. Instead, a mixture of substances based on the Si—C—Si structure is produced (30), as has been described. In order to... 

The Formation of Carbosilanes Table 8. Compounds from the pyrolysis of SiMe ... 

The Formation of Carbosilanes by Thermal Decomposition of Methylsilanes 37 Table 15. Thermal behavior of l,l,3,3-tetramethyl-l,3-disilapentene... 

The formation of carbosilanes in the gas phase pyrolysis of methylsilanes can be understood from an appraisal of the bond energies of possible reaction products. It is worth considering also the formation of molecules with Si—Si groups, as well as compounds with larger C—C units, as a result of the tetravalent nature of silicon and carbon. However, these were not observed only molecular structures with an Si—C—Si skeleton were found. 

A comparison of the compounds now known containing more than 5 Si atoms in the molecule shows that 17 compounds contain the adamantane skeleton as the basic molecular unit (Fig. 5). Two other compounds contain the adamantane skeleton as a part of their overall skeleton. Only three other types are built based on a different structural principle. This outcome shows distinctly the significance of the adamantane structure in the formation of carbosilanes by pyrolysis reactions. 

Formation of Carbosilanes by Direct Reaction of Halogenomethanes with Silicon... 

Formation of Carbosilanes by Direct Reaction of Halogenomethanes with Silicon 49 Table 19. Distillable compounds from the reaction of Si with CHCI3... 

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