MgPr2Se4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded in a distorted trigonal pyramidal geometry to one Se(2), one Se(3), and two equivalent Se(1) atoms. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded in a 7-coordinate geometry to one Se(2), two equivalent Se(3), and four equivalent Se(1) atoms. In the second Pr site, Pr(2) is bonded in a 6-coordinate geometry to one Se(2), one Se(3), and four equivalent Se(1) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Mg(1), two equivalent Pr(1), and two equivalent Pr(2) atoms to form a mixture of distorted edge, face, and corner-sharing SePr4Mg square pyramids. In the second Se site, Se(2) is bonded in a T-shaped geometry to one Mg(1), one Pr(1), and one Pr(2) atom. In the third Se site, Se(3) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Pr(2), and two equivalent Pr(1) atoms.
MgPr2Se4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded in a distorted trigonal pyramidal geometry to one Se(2), one Se(3), and two equivalent Se(1) atoms. The Mg(1)-Se(2) bond length is 2.45 Å. The Mg(1)-Se(3) bond length is 2.55 Å. Both Mg(1)-Se(1) bond lengths are 2.56 Å. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded in a 7-coordinate geometry to one Se(2), two equivalent Se(3), and four equivalent Se(1) atoms. The Pr(1)-Se(2) bond length is 3.04 Å. There is one shorter (2.97 Å) and one longer (2.98 Å) Pr(1)-Se(3) bond length. There are two shorter (3.16 Å) and two longer (3.32 Å) Pr(1)-Se(1) bond lengths. In the second Pr site, Pr(2) is bonded in a 6-coordinate geometry to one Se(2), one Se(3), and four equivalent Se(1) atoms. The Pr(2)-Se(2) bond length is 2.84 Å. The Pr(2)-Se(3) bond length is 3.13 Å. There are two shorter (3.02 Å) and two longer (3.11 Å) Pr(2)-Se(1) bond lengths. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Mg(1), two equivalent Pr(1), and two equivalent Pr(2) atoms to form a mixture of distorted edge, face, and corner-sharing SePr4Mg square pyramids. In the second Se site, Se(2) is bonded in a T-shaped geometry to one Mg(1), one Pr(1), and one Pr(2) atom. In the third Se site, Se(3) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Pr(2), and two equivalent Pr(1) atoms.