Mixed-Valent Neptunium(IV/V) Compound with Cation–Cation-Bound Six-Membered Neptunyl Rings

A new mixed-valent neptunium­(IV/V)
compound has been synthesized by evaporation of a neptunium­(V) acidic
solution. The structure of the compound features cation–cation-bound
six-membered neptunyl­(V) rings. These rings are further connected
by NpIV ions through cation–cation interactions
(CCIs) into a three-dimensional neptunium cationic open framework.
This example illustrates the possibility of isolating neptunyl­(V)
CCI oligomers in inorganic systems using other cations to compete
with NpV in bonding with the neptunyl oxygen.