Bonding in tris(.eta.5-cyclopentadienyl) actinide complexes. 2. The ground electronic configurations of "base-free" Cp3An complexes (An = thorium, protactinium, uranium, neptunium, plutonium)

Abstract

Quasi-relativistic X{alpha}-SW calculations have been carried our on the base-free tris({eta}{sup 5}-cyclopentadienyl) actinide complexes Cp{sub 3}Th (1) and Cp{sub 3}U (2). Unlike the actinide complexes Cp{sub 3}AnL (L = neutral two-electron donor), for which all of the An 6d orbitals are used as electron acceptors, 1 and 2 both contain a low-lying 6d{sub z{sup 2}} orbital that competes with the 5f orbitals for the metal-based electrons. It is predicted that 1 will have a 6d{sup 1} electron configuration, which agrees with recent EPR experiments by Edelstein, Lappert, et al. It is also predicted that, unlike Cp{sub 3}UL complexes, which have a 5f{sup 3} electron configuration, 2 might have a 6d{sup 1}5f{sup 2} ground configuration. Results are also presented for Cp{sub 3}Pa, Cp{sub 3}Np, and Cp{sup 3}Pu.