Molecular and electronic structure of selenium and tellurium tetrahalides

Molecular and electronic structures of MX₄ (M = Se, Te: X = F, Cl) were studied by the ab initio method with extended basis sets. The study is aimed at supplementing very scarce experimental information about these molecules. The results indicate that all molecules favour distorted disphenoidal geometries (C_2v point group) in preference to a C_4v geometry. A possibly interesting phenomenon of energy stabilisation by having bonds of different polarities within the same molecule has been observed in SeCl₄ and TeCl₄.