A DFT and PM3 Study of a Hypothetical Silicon-Based σ-Allyl Cation and σ-Allyl Radical and Higher Homologues

Abstract

DFT and PM3 calculations were used to model the hypothetical sigma-allyl cation 1-Si(3)()(+) and sigma-allyl radical 1-Si(3)()(*). For both the cation and the radical, the structure with equal Si-Si bond lengths and sigma-delocalized charge or spin is predicted to be favored relative to a bond-localized "capped" triquinane alternative. Higher homologues of 1-Si(3)()(+) and 1-Si(3)()(*) were also modeled; they likewise are predicted to prefer sigma-delocalized structures.