MgPrS3 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form MgS6 octahedra that share corners with eight equivalent Pr(1)S4 tetrahedra and edges with three equivalent Mg(1)S6 octahedra. Pr(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form distorted PrS4 tetrahedra that share corners with eight equivalent Mg(1)S6 octahedra and  an edgeedge with one Pr(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-72°. There are two inequivalent S sites. In the first S site, S(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Pr(1) atom. In the second S site, S(2) is bonded to two equivalent Mg(1) and two equivalent Pr(1) atoms to form edge-sharing SPr2Mg2 tetrahedra.
MgPrS3 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form MgS6 octahedra that share corners with eight equivalent Pr(1)S4 tetrahedra and edges with three equivalent Mg(1)S6 octahedra. Both Mg(1)-S(2) bond lengths are 2.51 Å. There are two shorter (2.54 Å) and two longer (2.92 Å) Mg(1)-S(1) bond lengths. Pr(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form distorted PrS4 tetrahedra that share corners with eight equivalent Mg(1)S6 octahedra and  an edgeedge with one Pr(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-72°. Both Pr(1)-S(1) bond lengths are 2.73 Å. There is one shorter (2.71 Å) and one longer (2.72 Å) Pr(1)-S(2) bond length. There are two inequivalent S sites. In the first S site, S(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Pr(1) atom. In the second S site, S(2) is bonded to two equivalent Mg(1) and two equivalent Pr(1) atoms to form edge-sharing SPr2Mg2 tetrahedra.