K2ScP2Se7 crystallizes in the monoclinic C2/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one Se(2), one Se(6), one Se(7), and three equivalent Se(4) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to one Se(2), one Se(5), one Se(6), one Se(7), and two equivalent Se(1) atoms. Sc(1) is bonded to one Se(1), one Se(2), one Se(4), one Se(5), and two equivalent Se(3) atoms to form ScSe6 octahedra that share  an edgeedge with one Sc(1)Se6 octahedra and edges with two equivalent P(2)Se4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded in a 4-coordinate geometry to one P(1), one Se(1), one Se(2), and one Se(6) atom. In the second P site, P(2) is bonded to one Se(3), one Se(4), one Se(5), and one Se(7) atom to form PSe4 tetrahedra that share edges with two equivalent Sc(1)Se6 octahedra. There are seven inequivalent Se sites. In the first Se site, Se(7) is bonded in a 3-coordinate geometry to one K(1), one K(2), and one P(2) atom. In the second Se site, Se(1) is bonded in a 4-coordinate geometry to two equivalent K(2), one Sc(1), and one P(1) atom. In the third Se site, Se(2) is bonded in a distorted rectangular see-saw-like geometry to one K(1), one K(2), one Sc(1), and one P(1) atom. In the fourth Se site, Se(6) is bonded in a 1-coordinate geometry to one K(1), one K(2), and one P(1) atom. In the fifth Se site, Se(3) is bonded in a distorted T-shaped geometry to two equivalent Sc(1) and one P(2) atom. In the sixth Se site, Se(4) is bonded to three equivalent K(1), one Sc(1), and one P(2) atom to form a mixture of distorted edge and corner-sharing SeK3ScP trigonal bipyramids. In the seventh Se site, Se(5) is bonded in a 3-coordinate geometry to one K(2), one Sc(1), and one P(2) atom.
K2ScP2Se7 crystallizes in the monoclinic C2/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one Se(2), one Se(6), one Se(7), and three equivalent Se(4) atoms. The K(1)-Se(2) bond length is 3.38 Å. The K(1)-Se(6) bond length is 3.63 Å. The K(1)-Se(7) bond length is 3.66 Å. There are a spread of K(1)-Se(4) bond distances ranging from 3.38-3.68 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to one Se(2), one Se(5), one Se(6), one Se(7), and two equivalent Se(1) atoms. The K(2)-Se(2) bond length is 3.54 Å. The K(2)-Se(5) bond length is 3.59 Å. The K(2)-Se(6) bond length is 3.61 Å. The K(2)-Se(7) bond length is 3.41 Å. There is one shorter (3.51 Å) and one longer (3.52 Å) K(2)-Se(1) bond length. Sc(1) is bonded to one Se(1), one Se(2), one Se(4), one Se(5), and two equivalent Se(3) atoms to form ScSe6 octahedra that share  an edgeedge with one Sc(1)Se6 octahedra and edges with two equivalent P(2)Se4 tetrahedra. The Sc(1)-Se(1) bond length is 2.71 Å. The Sc(1)-Se(2) bond length is 2.71 Å. The Sc(1)-Se(4) bond length is 2.74 Å. The Sc(1)-Se(5) bond length is 2.72 Å. There is one shorter (2.77 Å) and one longer (2.79 Å) Sc(1)-Se(3) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded in a 4-coordinate geometry to one P(1), one Se(1), one Se(2), and one Se(6) atom. The P(1)-P(1) bond length is 2.29 Å. The P(1)-Se(1) bond length is 2.25 Å. The P(1)-Se(2) bond length is 2.24 Å. The P(1)-Se(6) bond length is 2.16 Å. In the second P site, P(2) is bonded to one Se(3), one Se(4), one Se(5), and one Se(7) atom to form PSe4 tetrahedra that share edges with two equivalent Sc(1)Se6 octahedra. The P(2)-Se(3) bond length is 2.29 Å. The P(2)-Se(4) bond length is 2.25 Å. The P(2)-Se(5) bond length is 2.22 Å. The P(2)-Se(7) bond length is 2.17 Å. There are seven inequivalent Se sites. In the first Se site, Se(7) is bonded in a 3-coordinate geometry to one K(1), one K(2), and one P(2) atom. In the second Se site, Se(1) is bonded in a 4-coordinate geometry to two equivalent K(2), one Sc(1), and one P(1) atom. In the third Se site, Se(2) is bonded in a distorted rectangular see-saw-like geometry to one K(1), one K(2), one Sc(1), and one P(1) atom. In the fourth Se site, Se(6) is bonded in a 1-coordinate geometry to one K(1), one K(2), and one P(1) atom. In the fifth Se site, Se(3) is bonded in a distorted T-shaped geometry to two equivalent Sc(1) and one P(2) atom. In the sixth Se site, Se(4) is bonded to three equivalent K(1), one Sc(1), and one P(2) atom to form a mixture of distorted edge and corner-sharing SeK3ScP trigonal bipyramids. In the seventh Se site, Se(5) is bonded in a 3-coordinate geometry to one K(2), one Sc(1), and one P(2) atom.