,8,8-OCTAISOPROPYLTRICYCLO[4.2.0.0(2,5)]OCTASILANE

The title ladder polysilane was synthesized by the cross-coupling of a ll-trans-[(t-Bu)ClSi](4) and Cl(i-Pr)(2)SiSi(i-Pr)(2)Cl with lithium i n 40% yield. X-ray crystallographic analysis of the ladder polysilane shows a highly strained silicon skeleton; the Si-Si bond lengths vary from 2.412(3) to 2.481(2) Angstrom, and the Si-Si-Si bond angles of th e Si-4 rings range from 87.9(1) to 90.5(1)degrees. By comparison of th e structure and UV-visible spectra of this compound with those of the perisopropyl analog, we found that the structures and properties of la dder polysilanes are strongly affected by the substituents.