ELECTRONIC-STRUCTURE OF BIS(2,4-PENTANEDIONATO-O,O')OXOVANADIUM(IV) -A PHOTOELECTRON-SPECTROSCOPY, ELECTRONIC SPECTROSCOPY, AND AB-INITIO MOLECULAR-ORBITAL STUDY

The electronic structure of the title VO(acac)(2) complex has been inv estigated using effective; core potential configuration interaction ab initio calculations, UV-photoelectron spectroscopy, and electronic sp ectroscopy. The metal-ligand bonding with the equatorial acac(-) ligan ds is dominated by a interactions involving the filled ligand orbitals and the empty orbitals of the d(1) vanadium(IV) ion. The oxovanadium interactions involve a larger metal-d participation thus resulting in a strong V-O bonding having partial triple-bond character. Additional three-orbital-four-electron stabilizing interactions involving the fil led acac(-) MOs and the oxovanadium orbitals further reinforce both th e axial and equatorial bonds. The unpaired metal-d electron is complet ely localized in the nonbonding d(x2-y2) orbital. The low ionization e nergy of the photoelectron spectrum has been fully assigned on the bas is of combined Delta SCF and configuration interaction calculations. T he same theoretical approach has, in addition, provided a good fitting of frequencies associated with ''d-d'' and charge transfer electronic transitions.