Polysilanes from cyclosilanes

The preparation of polysilanes by the reaction of intermediately formed silylmetallics, derived from cyclosilanes, will be discussed in the next section. 

The conversion of silicon-functional polysilanes (obtained from cyclosilanes) to other polysilane derivatives is also possible. Thus, reaction of... 

Electron delocalization in cyclic polysilanes has been studied rather extensively. In these compounds the -electrons play the role of the delocalized rc-electrons in cyclic polyenes9. Cyclosilanes therefore show some properties resembling those of aromatic hydrocarbons. In particular, they undergo one-electron oxidation or reduction to form cation radicals or anion radicals, in which (from the ESR spectra) the unpaired electrons are fully delocalized. 

Since only polymers derived from cyclic starting materials, which are likely to have siloxene-like structures, exhibit color and fluorescence, the polysilane ring seems to be essential for the exceptional optical properties. This is in agreement with the original idea assuming the cyclosilane ring to be the chromophore responsible for the photoluminescence of siloxenes. 

Together with the solid phenylated cyclosilanes isolated from these reactions, there were also obtained rather large quantities of viscous liquid materials which have not as yet been fully characterized. Partial separation of these oils was achieved by fractionation from acetone. Some less soluble portions appeared to be materials made up of only diphenylsilylene units. Cryoscopic determinations of various fractions indicated multiples of Si(C6H5)2 ranging from seven to nine, and chemical evidence seemed to indicate that the materials were cyclic polysilanes. ... 

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