Quasirelativistic SCF-Xα Scattered-Wave Study of Uranocene, Thorocene, and Cerocene

Quasirelativistic SCF-Xα scattered-wave calculations are presented for di-ir-[8]annuleneuranium(IV) (uranocene), -thorium(IV) (thorocene), and -cerium(IV) (cerocene). Improved agreement over previous nonrelativistic results is found for both spectra and photoelectron spectra. An explanation is presented for the apparent relative success of the previous nonrelativistic calculations. The quasirelativistic calculations confirm that f±2 orbitals of the central metal atom contribute to the covalent ring-metal bonding, but they emphasize even more than the nonrelativistic treatment the important role of the 6d orbitals in such bonding.