Penning ionization electron spectroscopy of group ivb tetramethyl compounds: (CH3)4M (M = C, Si, Ge, Sn, Pb)

Abstract

He* (23S) Penning ionization electron spectra (PIES) and He I photoelectron spectra (UPS) were measured to study the valence electronic structures and reactivities of group IVB tetramethyl compounds: (CH3)4C, (CH3)4Si, (CH3)4Ge, (CH3)4Sn, and (CH3)4Pb. On the basis of ab initio MO calculations and the character of PIES, we have established the assignment of the UPS bands. The bands in UPS and PIES are classified into three groups, which are due to the σMC, σCH, and M ns orbitals. With increasing size of the central atom, the relative band intensity of PIES for the σMC and M ns orbitals is found to decrease. This can be interpreted by the electron distributions on the methyl groups for these orbitals, which diminish on going from (CH3)4C to (CH3)4Pb, as the interaction between the central atom and the methyl groups become weaker. © 1989 American Chemical Society.