A new approach to the distortion of the tetrahedral geometry at E in the E(ZXY2)4 compounds

Abstract

Density functional theory calculations have been used to study the structural features of a variety of tetrahedral E(ZXY₂)₄ compounds. In these compounds, the six Z–E–Z angles deviate from the ideal tetrahedral geometry in such a way that they are either four smaller and two larger (4s2l), or four larger and two smaller (4l2s). A simple cubic model has been used to explain such structural distortions. Within this cubic model, the stability of the D_2d and S₄ conformers of E(ZXY₂)₄ compounds can be understood in terms of the homophobic and heterophilic nature of the substituents on the Z atoms. The hyper-conjugation effect has also been emphasized for compounds when the Z atoms have lone pairs of electrons.