The role of cation–cation interactions in a neptunyl chloride hydrate and topological aspects of neptunyl structural units

The compound K4(NpO2)3Cl7(H2O)4 was synthesized by evaporation of a Np5+-bearing solution. The crystal structure was determined by single crystal X-ray diffraction and refined to R1=0.0374. The compound is triclinic, P−1, a=8.882(1) Å, b=12.082(2) Å, c=12.403(2) Å, α=65.855(2)°, β=69.604(2)°, γ=74.432(2)°, V=1126.0(3) Å3, and Z=2. The structure contains dimers of edge sharing Np5+ pentagonal bipyramids that are linked into infinite chains through cation–cation interactions with an additional Np5+ pentagonal bipyramid. The structural units are linked through bonds to interstitial K cations and by H bonding. A graphical representation for neptunyl structural units including cation–cation interactions is introduced.