Polymeric disilane derivatives

Si-Si Bond Homolysis. Ishikawa and co-workers (50, 51) have also studied the photolysis of a number of polymeric disilane derivatives. These workers have examined both derivatives with pendant silicon substituents (50) and materials in which the disilane moiety is incorporated into the polymeric backbone (5i). For derivatives with pendant silicon substituents (Scheme II), irradiation destroys the characteristic phenyldisilane absorption... 

Degradation of Larger Silicon Catenates. Although it seems clear that polymeric disilane derivatives photodecompose by bond homolysis to produce silyl radicals, model studies on larger silicon catenates indicate that their photochemistry may be more complex (Scheme IV). Cyclic silane derivatives seem to extrude monomeric silylenes upon irradiation to produce smaller cyclic silanes (52). The proposed silylene intermediates have been identified spectroscopically 49, 53), and trapping adducts have been isolated in solution. Exhaustive irradiation ultimately results in acyclic silanes, which... 

Ishikawa and co-workers (50, 51) have also reported the photodegradation of backbone disilane polymers (Scheme III). In this case, as in the previous example with pendant silyl substituents, silicon-silicon bond homolysis to produce silyl radicals was the predominant process. When irradiated in toluene, the photodegraded polymer showed a substantial -SiH band at 2150 cm in the IR spectrum. Similarly, NMR spectroscopic examination of the irradiated polymer showed evidence of silyl radical substitution into the solvent toluene. Irradiation of the polymeric disilane in deuterated methanol produced no bands due to Si-D in the IR spectrum and resulted in the incorporation of the elements of methanol into the chain ends (as revealed by NMR spectroscopy). For the phenyl-substituted polymer, the NMR evidence indicated that <5% of rearranged cyclohexadiene derivatives were formed. 

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