An Ab Initio Molecular Orbital Study on Twisting in Silyl-Substituted Ethylene Cation Radicals

Abstract

Abstract Twisting in two silyl-substituted ethylene cation radicals, the cation radicals of vinylsilane (1) and vinylidenebissilane (2), were investigated by ab initio UHF calculations with the 3-21G and 3-21G(*) basis sets. Both 1+· and 2+· were found to have twisted equilibrium structures, the twist angle being 29° and 42°, respectively. The planarization barriers evaluated for 1+· and 2+· are about 1 and 7 kcal mol−1, respectively. The planar and 90°-twisted forms of 2+· have comparable energies. The hyperconjugation of the C-Si bonds is reflected in the calculated molecular structures.