Identification of the Formal+2 Oxidation State of Neptunium: Synthesis and Structural Characterization of {Np-II[C5H3(SiMe3)(2)](3)}(1-)

We report a new formal oxidation state for neptunium in a crystallographically characterizable molecular complex, namely Np2+ in [K(crypt)][(NpCp)-Cp-II ''(3)] [crypt = 2.2.2-cryptand, Cp '' = C5H3(SiMe3)(2)]. Density functional theory calculations indicate that the ground state electronic configuration of the Np2+ ion in the complex is Sf(4)6d(1).