The electronic structure of (eta5-C5H5)3MOR (M = Ce, Th, U) complexes has been investigated by He I and He II UV photoelectron spectroscopy combined with SCF Xalpha-DVM calculations. Fully relativistic Dirac-Slater calculations were also carried out for the M = Th complex. The nonrelativistic calculations indicate that metal-ligand interactions involving the highest energy ligand orbitals involve primarily metal 5f orbitals while 6d admixtures are found for lower energy orbitals. The M-0 bonding is both sigma and pi in nature and involves primarily metal 6d atomic orbitals. Evidence of a charge redistribution mechanism along the CH3 --> O --> M --> Cp3 direction provides a satisfactory explanation for the shortened M-0 distances and strong propensity for nearly linear M-O-CH3 linkages observed in diffraction studies. The fully relativistic calculations show that metal d contributions are slightly underestimated at the nonrelativistic level. Such deviations do not, however, alter the overall description of the metal-ligand bonding. The nonrelativistic configuration of the metal center compares well with the relativistic data. Gas-phase ionization energies can be accurately and comparably evaluated at the computationally more efficient nonrelativistic level if optimized basis sets and potential representations are used.
A COMPARATIVE FULLY RELATIVISTIC NONRELATIVISTIC 1ST-PRINCIPLES X(ALPHA)-DVM AND PHOTOELECTRON SPECTROSCOPIC INVESTIGATION OF ELECTRONIC-STRUCTURE IN HOMOLOGOUS 4F AND 5F TRIS(ETA(5)-CYCLOPENTADIENYL)METAL(IV) ALKOXIDE COMPLEXES
GULINO, Antonino;DI BELLA, Santo;
1993-01-01
Abstract
The electronic structure of (eta5-C5H5)3MOR (M = Ce, Th, U) complexes has been investigated by He I and He II UV photoelectron spectroscopy combined with SCF Xalpha-DVM calculations. Fully relativistic Dirac-Slater calculations were also carried out for the M = Th complex. The nonrelativistic calculations indicate that metal-ligand interactions involving the highest energy ligand orbitals involve primarily metal 5f orbitals while 6d admixtures are found for lower energy orbitals. The M-0 bonding is both sigma and pi in nature and involves primarily metal 6d atomic orbitals. Evidence of a charge redistribution mechanism along the CH3 --> O --> M --> Cp3 direction provides a satisfactory explanation for the shortened M-0 distances and strong propensity for nearly linear M-O-CH3 linkages observed in diffraction studies. The fully relativistic calculations show that metal d contributions are slightly underestimated at the nonrelativistic level. Such deviations do not, however, alter the overall description of the metal-ligand bonding. The nonrelativistic configuration of the metal center compares well with the relativistic data. Gas-phase ionization energies can be accurately and comparably evaluated at the computationally more efficient nonrelativistic level if optimized basis sets and potential representations are used.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.