Combined helium I/helium II photoelectron spectroscopic and Hartree-Fock-Slater investigation of electronic structure and bonding in uranium hexamethoxide

The electronic structure of the uranium(VI) alkoxide U(OCH3)6 has been investigated by using a combination of He I/He II photoelectron spectroscopy and discrete variational (DV) X.alpha. molecular orbital calculations. Good agreement is obtained between the experimental and calculated ionization energies. It is found that the low ionization energy features of the photoelectron spectra are due to varying degrees of donation of the oxygen lone pairs to the empty orbitals on the uranium atom and to the reduction of the molecular symmetry to Ci via bending of the U-O-C linkages. The methyl groups act as both sigma and pi donors to the oxygen 2p orbitals, increasing the overall donor strength of the alkoxide ligands