Mg(NiS2)4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form MgS4 tetrahedra that share corners with three equivalent Ni(2)S6 octahedra, corners with three equivalent Ni(3)S6 octahedra, and corners with six equivalent Ni(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 61-62°. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one S(1), one S(2), one S(3), one S(4), one S(5), and one S(6) atom to form NiS6 octahedra that share corners with three equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(1)S6 octahedra, edges with two equivalent Ni(2)S6 octahedra, and edges with two equivalent Ni(3)S6 octahedra. In the second Ni site, Ni(2) is bonded to one S(2), one S(6), two equivalent S(1), and two equivalent S(4) atoms to form NiS6 octahedra that share corners with three equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(3)S6 octahedra, and edges with four equivalent Ni(1)S6 octahedra. In the third Ni site, Ni(3) is bonded to one S(3), one S(5), two equivalent S(1), and two equivalent S(4) atoms to form NiS6 octahedra that share corners with three equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(2)S6 octahedra, and edges with four equivalent Ni(1)S6 octahedra. There are six inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), one Ni(1), one Ni(2), and one Ni(3) atom to form a mixture of distorted corner and edge-sharing SMgNi3 tetrahedra. In the second S site, S(2) is bonded to one Mg(1), one Ni(2), and two equivalent Ni(1) atoms to form a mixture of distorted corner and edge-sharing SMgNi3 tetrahedra. In the third S site, S(3) is bonded to one Mg(1), one Ni(3), and two equivalent Ni(1) atoms to form a mixture of corner and edge-sharing SMgNi3 tetrahedra. In the fourth S site, S(4) is bonded in a distorted T-shaped geometry to one Ni(1), one Ni(2), and one Ni(3) atom. In the fifth S site, S(5) is bonded in a distorted T-shaped geometry to one Ni(3) and two equivalent Ni(1) atoms. In the sixth S site, S(6) is bonded in a distorted T-shaped geometry to one Ni(2) and two equivalent Ni(1) atoms.
Mg(NiS2)4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form MgS4 tetrahedra that share corners with three equivalent Ni(2)S6 octahedra, corners with three equivalent Ni(3)S6 octahedra, and corners with six equivalent Ni(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 61-62°. The Mg(1)-S(2) bond length is 2.39 Å. The Mg(1)-S(3) bond length is 2.39 Å. Both Mg(1)-S(1) bond lengths are 2.39 Å. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one S(1), one S(2), one S(3), one S(4), one S(5), and one S(6) atom to form NiS6 octahedra that share corners with three equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(1)S6 octahedra, edges with two equivalent Ni(2)S6 octahedra, and edges with two equivalent Ni(3)S6 octahedra. The Ni(1)-S(1) bond length is 2.33 Å. The Ni(1)-S(2) bond length is 2.34 Å. The Ni(1)-S(3) bond length is 2.33 Å. The Ni(1)-S(4) bond length is 2.26 Å. The Ni(1)-S(5) bond length is 2.25 Å. The Ni(1)-S(6) bond length is 2.26 Å. In the second Ni site, Ni(2) is bonded to one S(2), one S(6), two equivalent S(1), and two equivalent S(4) atoms to form NiS6 octahedra that share corners with three equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(3)S6 octahedra, and edges with four equivalent Ni(1)S6 octahedra. The Ni(2)-S(2) bond length is 2.33 Å. The Ni(2)-S(6) bond length is 2.25 Å. Both Ni(2)-S(1) bond lengths are 2.33 Å. Both Ni(2)-S(4) bond lengths are 2.25 Å. In the third Ni site, Ni(3) is bonded to one S(3), one S(5), two equivalent S(1), and two equivalent S(4) atoms to form NiS6 octahedra that share corners with three equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(2)S6 octahedra, and edges with four equivalent Ni(1)S6 octahedra. The Ni(3)-S(3) bond length is 2.33 Å. The Ni(3)-S(5) bond length is 2.25 Å. Both Ni(3)-S(1) bond lengths are 2.34 Å. Both Ni(3)-S(4) bond lengths are 2.25 Å. There are six inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), one Ni(1), one Ni(2), and one Ni(3) atom to form a mixture of distorted corner and edge-sharing SMgNi3 tetrahedra. In the second S site, S(2) is bonded to one Mg(1), one Ni(2), and two equivalent Ni(1) atoms to form a mixture of distorted corner and edge-sharing SMgNi3 tetrahedra. In the third S site, S(3) is bonded to one Mg(1), one Ni(3), and two equivalent Ni(1) atoms to form a mixture of corner and edge-sharing SMgNi3 tetrahedra. In the fourth S site, S(4) is bonded in a distorted T-shaped geometry to one Ni(1), one Ni(2), and one Ni(3) atom. In the fifth S site, S(5) is bonded in a distorted T-shaped geometry to one Ni(3) and two equivalent Ni(1) atoms. In the sixth S site, S(6) is bonded in a distorted T-shaped geometry to one Ni(2) and two equivalent Ni(1) atoms.