PYRAMIDAL INVERSION ENERGIES OF HYPERVALENT SELENOXIDES - AN ABINITIO MO STUDY

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.