Mixed-valent neptunium oligomer complexes based on cation-cation interactions.

Mixed-valent tri- and tetranuclear complexes of neptunium, [{(NpCl4)-Cl-IV}{(NpO2Cl)-O-V(THF)(3)}(2)]THF and [{(NpCl3)-Cl-IV}{(NpO2)-O-V((2)-Cl)(THF)(2)}(3){(3)-Cl}] (THF = tetrahydrofuran), were synthesised and characterised. Both the complexes are formed via the cation-cation interactions between the Np(iv) centre and the axial oxygens of the neptunyl(v) unit (i.e. trans-dioxo NpO2+ cation), demonstrating the potential of cation-cation interactions for further exploring the oligomer/cluster chemistry of actinides.