Pyramidal inversion energies of hypervalent selenoxides. An ab initio MO study

Abstract

Ab initio MO computations on hypervalent selenoxides, R₂SeO (R = H, F and CH₃), have been performed to obtain their accurate pyramidal inversion energies, which are compared with the corresponding sulfoxides. The Se–O bond at the saddle-point in the inversion reactions depends very much on both the basis set and level of theory employed; a method beyond the Hartree–Fock level of theory with an extended basis set is necessary to attain the present purpose. In difluoro selenoxide (F₂SeO) electron correlations greatly decrease the inversion energy, which is smaller than that in the analogous difluoro sulfoxide (F₂SO). The present computations clearly indicate that the pyramidal inversion energies of compounds with a Se atom depend on the substituent R in R₂SeO and that they are not always larger than those with a lower principal quantum number (for example, a S atom) in the same group of the periodic table.