Crystal and molecular structure of [<i>i</i>‐Pr₂Si]₄ and [(Me₃SICH₂)₂Si]₄ and some structural properties of cyclopolysilanes, [R¹R²Si]_n (<i>n</i> = 3‐6)

Abstract

Abstract The crystal structures of octaisopropylcyclotetrasilane [ i ‐Pr 2 Si] 4 (1) and octakis(trimethylsilylmethyl)cyclotetrasilane [(Me 3 SiCH 2 ) 2 Si] 4 (2) have been determined by means of X‐ray diffraction analysis. Various crystallographic and structural data for the two compounds were recorded. The Si 4 rings of the compounds are nonplanar with quite large dihedral angles of 37.1° in (1) and 36.6° in (2), being comparable to that (36.8)° for [ t ‐BuMeSi] 4 reported previously and other characteristic features in the structures of (1) and (2) were described. Some structural properties of the cyclic catenation systems, [R 1 R 2 Si] n ( n = 3–6), including (1) and (2) were also discussed from a comparative viewpoint with respect to the ring shape and the relationship between ring size and Si‐Si bond length.