Synthesis of Cyclic and Bicyclic Polysilanes of Variable Ring Sizes

Some trimethylsilyl-substituted cyclohepta-, cycloocta-, and cyclononasilanes were obtained by salt elimination reaction of α,ω-dipotassiotetrakis(trimethylsilyl)permethyloligosilanes with α,ω-dichloropermethyloligosilanes. Utilizing the same synthetic concept, the use of dianionic cyclooligosilanes led to the formation of various bicyclooligosilanes. The UV absorption behavior of the trimethylsilyl-substituted cyclosilanes is different from that of permethylated cyclosilanes of the same ring size. Spectroscopic analysis suggests that σ-electron delocalization occurs along chain segments in the ring reaching from one trimethylsilyl group to the other.