Structure, conformation, and UV absorption behavior of partially trimethylsilylated oligosilane chains

A number of new oligosilane chains containing linear segments with up to 18 silicon atoms were prepared. Employing salt elimination reactions of oligosilylpotassium compounds and oligosilylhalides, we prepared a number of tris(trimethylsilyl)silyl-terminated chains with varying internal segments consisting of dimethylsilylene and bis(trimethylsilyl)silylene units. Single-crystal X-ray diffraction and UV spectroscopic analysis indicate that the oligosilanes thus obtained are conformationally highly constrained due to steric interactions between trimethylsilyl groups. The chains consist of all-transoidoriented segments, capable of σ-bond electron delocalization, which are separated by cisoid turns.