Photoelectron spectroscopy of f-element coordination compounds. 2. He-II spectra of β-diketonate complexes of uranium(IV), thorium(IV), zirconium(IV), and dioxouranium(VI)

Abstract

Photoelectron spectra of some ..beta..-diketonate uranyl complexes are reported. They provide information about the ordering of the upper four molecular subshells (belonging to ..pi../sub g/, ..pi../sub u/, sigma/sub u/, and sigma/sub g/ symmetry species) localized on the uranyl ion which yields, in turn, insight into the nature of the bonding in the uranyl ion. It appears that metal 5f covalency is of major importance in this species. The spectra also give information about the bonding between the uranyl moiety and the equatorial ligands: the uranyl phi/sub u/ orbital is shown to be intimately involved in such bonding. Photoelectron spectra of some tetrakis(..beta..-diketonate)actinide complexes indicate that metal-ligand bonding is dominated by sigma-type overlaps. The differences between the photoelectron spectra of transition-metal(Zr) and actinide(Th,U) complexes suggest substantial involvement of the metal 5f subshell in the bonding molecular orbitals of the actinide complexes. The spectra of the uranium(IV) complexes each contain peaks associated with ionization of the metal 5f subshell.