KPrSiSe4 crystallizes in the monoclinic P2_1 space group. K(1) is bonded in a 8-coordinate geometry to one Se(4), two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. Pr(1) is bonded in a 7-coordinate geometry to one Se(2), two equivalent Se(1), two equivalent Se(3), and two equivalent Se(4) atoms. Si(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(4) atom. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent K(1), two equivalent Pr(1), and one Si(1) atom to form distorted corner-sharing SeK2Pr2Si square pyramids. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to three equivalent K(1), one Pr(1), and one Si(1) atom. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to two equivalent K(1), two equivalent Pr(1), and one Si(1) atom. In the fourth Se site, Se(4) is bonded in a distorted see-saw-like geometry to one K(1), two equivalent Pr(1), and one Si(1) atom.
KPrSiSe4 crystallizes in the monoclinic P2_1 space group. K(1) is bonded in a 8-coordinate geometry to one Se(4), two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. The K(1)-Se(4) bond length is 3.46 Å. There is one shorter (3.52 Å) and one longer (3.55 Å) K(1)-Se(1) bond length. There is one shorter (3.49 Å) and one longer (3.67 Å) K(1)-Se(3) bond length. There are a spread of K(1)-Se(2) bond distances ranging from 3.48-3.89 Å. Pr(1) is bonded in a 7-coordinate geometry to one Se(2), two equivalent Se(1), two equivalent Se(3), and two equivalent Se(4) atoms. The Pr(1)-Se(2) bond length is 3.02 Å. Both Pr(1)-Se(1) bond lengths are 3.11 Å. There is one shorter (3.05 Å) and one longer (3.08 Å) Pr(1)-Se(3) bond length. There is one shorter (3.05 Å) and one longer (3.19 Å) Pr(1)-Se(4) bond length. Si(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(4) atom. The Si(1)-Se(1) bond length is 2.30 Å. The Si(1)-Se(2) bond length is 2.26 Å. The Si(1)-Se(3) bond length is 2.30 Å. The Si(1)-Se(4) bond length is 2.29 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent K(1), two equivalent Pr(1), and one Si(1) atom to form distorted corner-sharing SeK2Pr2Si square pyramids. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to three equivalent K(1), one Pr(1), and one Si(1) atom. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to two equivalent K(1), two equivalent Pr(1), and one Si(1) atom. In the fourth Se site, Se(4) is bonded in a distorted see-saw-like geometry to one K(1), two equivalent Pr(1), and one Si(1) atom.