Covalency in Actinide 5f Compounds: The ESCA of Diphtalocyaninato-Uranium(IV) and -Thorium(IV)

Abstract
The nature of the bonding in both UPc2 and ThPc2 (Pc=phthalocyaninato ion) has been studied by x-ray photo-electron spectroscopy. While the ESCA spectrum of each of the U(4f) levels reveals two electron ‘shake-up’ satellites characteristic of 5f-orbital participation in bonding, ie. covalency, the corresponding Th(4f) levels do not. ‘shake-up’ satellite photopeaks observed in the U(4f) spectra probably arise from electron charge-transfer from molecular orbitals of both metal and ligand character to the corresponding anti-bonding molecular orbitals.