K2NSe4 crystallizes in the monoclinic Cc space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 5-coordinate geometry to one N(1), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. In the second K site, K(2) is bonded in a 8-coordinate geometry to two equivalent N(1), one Se(2), one Se(4), two equivalent Se(1), and two equivalent Se(3) atoms. N(1) is bonded in a T-shaped geometry to one K(1) and two equivalent K(2) atoms. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted pentagonal planar geometry to two equivalent K(1), two equivalent K(2), and one Se(2) atom. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one K(2), two equivalent K(1), one Se(1), and one Se(4) atom. In the third Se site, Se(3) is bonded in a distorted pentagonal planar geometry to two equivalent K(1), two equivalent K(2), and one Se(4) atom. In the fourth Se site, Se(4) is bonded in a 3-coordinate geometry to one K(2), one Se(2), and one Se(3) atom.
K2NSe4 crystallizes in the monoclinic Cc space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 5-coordinate geometry to one N(1), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. The K(1)-N(1) bond length is 3.00 Å. There is one shorter (3.38 Å) and one longer (3.62 Å) K(1)-Se(1) bond length. There is one shorter (3.84 Å) and one longer (3.88 Å) K(1)-Se(2) bond length. There is one shorter (3.31 Å) and one longer (3.43 Å) K(1)-Se(3) bond length. In the second K site, K(2) is bonded in a 8-coordinate geometry to two equivalent N(1), one Se(2), one Se(4), two equivalent Se(1), and two equivalent Se(3) atoms. There is one shorter (3.06 Å) and one longer (3.30 Å) K(2)-N(1) bond length. The K(2)-Se(2) bond length is 3.45 Å. The K(2)-Se(4) bond length is 3.52 Å. There is one shorter (3.30 Å) and one longer (3.49 Å) K(2)-Se(1) bond length. There is one shorter (3.27 Å) and one longer (3.33 Å) K(2)-Se(3) bond length. N(1) is bonded in a T-shaped geometry to one K(1) and two equivalent K(2) atoms. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted pentagonal planar geometry to two equivalent K(1), two equivalent K(2), and one Se(2) atom. The Se(1)-Se(2) bond length is 2.37 Å. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one K(2), two equivalent K(1), one Se(1), and one Se(4) atom. The Se(2)-Se(4) bond length is 2.38 Å. In the third Se site, Se(3) is bonded in a distorted pentagonal planar geometry to two equivalent K(1), two equivalent K(2), and one Se(4) atom. The Se(3)-Se(4) bond length is 2.36 Å. In the fourth Se site, Se(4) is bonded in a 3-coordinate geometry to one K(2), one Se(2), and one Se(3) atom.