BONDING IN TRIS(ETA-5-CYCLOPENTADIENYL) ACTINIDE COMPLEXES .5. A COMPARISON OF THE BONDING IN NP, PU, AND TRANSPLUTONIUM COMPOUNDS WITH THAT IN LANTHANIDE COMPOUNDS AND A TRANSITION-METAL ANALOG

Cp3An (An = U, Np, Pu, Am, Cm, Bk, Cf) compounds have been investigated via Xalpha-SW molecular orbital calculations with quasi-relativistic corrections. The 5f-orbital energy drops across the series while the 6d-orbital energy rises. Due to the greater radial extension of the 6d orbitals, the metal 6d orbitals are more important in bonding the Cp ligands than the 5f orbitals. Comparison of the actinide compounds with the lanthanide series reveals some minor differences. The 4f orbitals and 6s orbital of the lanthanides are not as effective at bonding the Cp ligands as the 5f orbitals and 7s orbital of the actinides. Also, the ''semicore'' 5p orbitals of the lanthanides have a greater antibonding influence on the Cp ligands than do the 6p orbitals of the actinides. Comparison of the actinide compounds with (eta-5-Cp)3Zr shows some major differences. The 4d orbitals of zirconium are much more effective at bonding the Cp ligands than the 6d orbitals of the actinides.