Photoelectron spectra of the trimethyl compounds of the group V elements. Constant ionisation potentials of the lone pair orbital electrons

The lone pair orbital ionisation potentials of the compounds Me3X (X: N, P, As, Sb) are found to be constant, in contrast to the series Me2Y and H2Y (Y: O, S, Se, Te) whose first i.p. values vary distinctly with Y. This difference is explained on symmetry grounds by changes in hybridization of the lone pair orbitals on the central atoms X. In a qualitative MO model the interactions of the a1 orbitals of Me3X and H3X are discussed. On the basis of this model and semiempirical calculations a consistent interpretation of the photoelectron spectra of the title compounds is proposed.