Np2Se5 crystallizes in the orthorhombic Pbcn space group. Np(1) is bonded in a 10-coordinate geometry to two equivalent Se(3), four equivalent Se(1), and four equivalent Se(2) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to four equivalent Np(1), one Se(1), and one Se(2) atom. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to four equivalent Np(1), one Se(1), and one Se(2) atom. In the third Se site, Se(3) is bonded to four equivalent Np(1) atoms to form distorted corner-sharing SeNp4 trigonal pyramids.
Np2Se5 crystallizes in the orthorhombic Pbcn space group. Np(1) is bonded in a 10-coordinate geometry to two equivalent Se(3), four equivalent Se(1), and four equivalent Se(2) atoms. There is one shorter (2.92 Å) and one longer (2.94 Å) Np(1)-Se(3) bond length. There are a spread of Np(1)-Se(1) bond distances ranging from 2.98-3.08 Å. There are a spread of Np(1)-Se(2) bond distances ranging from 3.00-3.11 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to four equivalent Np(1), one Se(1), and one Se(2) atom. The Se(1)-Se(1) bond length is 2.70 Å. The Se(1)-Se(2) bond length is 2.80 Å. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to four equivalent Np(1), one Se(1), and one Se(2) atom. The Se(2)-Se(2) bond length is 2.63 Å. In the third Se site, Se(3) is bonded to four equivalent Np(1) atoms to form distorted corner-sharing SeNp4 trigonal pyramids.