MgV4(CuS4)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a 8-coordinate geometry to one Cu(1), one Cu(2), one S(1), one S(3), two equivalent S(5), and two equivalent S(6) atoms. There are three inequivalent V sites. In the first V site, V(1) is bonded to one S(1), one S(3), two equivalent S(5), and two equivalent S(6) atoms to form edge-sharing VS6 octahedra. In the second V site, V(2) is bonded to one S(2), one S(4), two equivalent S(5), and two equivalent S(6) atoms to form edge-sharing VS6 octahedra. In the third V site, V(3) 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 edge-sharing VS6 octahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 5-coordinate geometry to one Mg(1), one S(1), one S(2), and two equivalent S(6) atoms. In the second Cu site, Cu(2) is bonded in a 5-coordinate geometry to one Mg(1), one S(3), one S(4), and two equivalent S(5) atoms. There are six inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), one V(1), two equivalent V(3), and one Cu(1) atom to form SMgV3Cu square pyramids that share corners with two equivalent S(4)V3Cu tetrahedra, corners with two equivalent S(5)MgV3Cu trigonal bipyramids, corners with four equivalent S(3)MgV3Cu trigonal bipyramids, edges with four equivalent S(6)MgV3Cu square pyramids, and edges with two equivalent S(5)MgV3Cu trigonal bipyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one V(2), two equivalent V(3), and one Cu(1) atom. In the third S site, S(3) is bonded to one Mg(1), one V(1), two equivalent V(3), and one Cu(2) atom to form SMgV3Cu trigonal bipyramids that share corners with two equivalent S(6)MgV3Cu square pyramids, corners with four equivalent S(1)MgV3Cu square pyramids,  a cornercorner with one S(4)V3Cu tetrahedra, edges with two equivalent S(6)MgV3Cu square pyramids,  an edgeedge with one S(4)V3Cu tetrahedra, and edges with four equivalent S(5)MgV3Cu trigonal bipyramids. In the fourth S site, S(4) is bonded to one V(2), two equivalent V(3), and one Cu(2) atom to form a mixture of corner and edge-sharing SV3Cu tetrahedra. In the fifth S site, S(5) is bonded to one Mg(1), one V(1), one V(2), one V(3), and one Cu(2) atom to form SMgV3Cu trigonal bipyramids that share  a cornercorner with one S(1)MgV3Cu square pyramid, corners with five equivalent S(6)MgV3Cu square pyramids,  a cornercorner with one S(4)V3Cu tetrahedra,  an edgeedge with one S(1)MgV3Cu square pyramid,  an edgeedge with one S(6)MgV3Cu square pyramid,  an edgeedge with one S(4)V3Cu tetrahedra, edges with two equivalent S(3)MgV3Cu trigonal bipyramids, and edges with two equivalent S(5)MgV3Cu trigonal bipyramids. In the sixth S site, S(6) is bonded to one Mg(1), one V(1), one V(2), one V(3), and one Cu(1) atom to form SMgV3Cu square pyramids that share corners with two equivalent S(4)V3Cu tetrahedra,  a cornercorner with one S(3)MgV3Cu trigonal bipyramid, corners with five equivalent S(5)MgV3Cu trigonal bipyramids, edges with two equivalent S(1)MgV3Cu square pyramids, edges with two equivalent S(6)MgV3Cu square pyramids,  an edgeedge with one S(3)MgV3Cu trigonal bipyramid, and  an edgeedge with one S(5)MgV3Cu trigonal bipyramid.
MgV4(CuS4)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a 8-coordinate geometry to one Cu(1), one Cu(2), one S(1), one S(3), two equivalent S(5), and two equivalent S(6) atoms. The Mg(1)-Cu(1) bond length is 2.56 Å. The Mg(1)-Cu(2) bond length is 2.57 Å. The Mg(1)-S(1) bond length is 2.63 Å. The Mg(1)-S(3) bond length is 2.53 Å. Both Mg(1)-S(5) bond lengths are 2.53 Å. Both Mg(1)-S(6) bond lengths are 2.63 Å. There are three inequivalent V sites. In the first V site, V(1) is bonded to one S(1), one S(3), two equivalent S(5), and two equivalent S(6) atoms to form edge-sharing VS6 octahedra. The V(1)-S(1) bond length is 2.43 Å. The V(1)-S(3) bond length is 2.50 Å. Both V(1)-S(5) bond lengths are 2.50 Å. Both V(1)-S(6) bond lengths are 2.43 Å. In the second V site, V(2) is bonded to one S(2), one S(4), two equivalent S(5), and two equivalent S(6) atoms to form edge-sharing VS6 octahedra. The V(2)-S(2) bond length is 2.35 Å. The V(2)-S(4) bond length is 2.45 Å. Both V(2)-S(5) bond lengths are 2.52 Å. Both V(2)-S(6) bond lengths are 2.43 Å. In the third V site, V(3) 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 edge-sharing VS6 octahedra. The V(3)-S(1) bond length is 2.43 Å. The V(3)-S(2) bond length is 2.35 Å. The V(3)-S(3) bond length is 2.52 Å. The V(3)-S(4) bond length is 2.45 Å. The V(3)-S(5) bond length is 2.52 Å. The V(3)-S(6) bond length is 2.43 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 5-coordinate geometry to one Mg(1), one S(1), one S(2), and two equivalent S(6) atoms. The Cu(1)-S(1) bond length is 2.31 Å. The Cu(1)-S(2) bond length is 2.18 Å. Both Cu(1)-S(6) bond lengths are 2.31 Å. In the second Cu site, Cu(2) is bonded in a 5-coordinate geometry to one Mg(1), one S(3), one S(4), and two equivalent S(5) atoms. The Cu(2)-S(3) bond length is 2.42 Å. The Cu(2)-S(4) bond length is 2.23 Å. Both Cu(2)-S(5) bond lengths are 2.43 Å. There are six inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), one V(1), two equivalent V(3), and one Cu(1) atom to form SMgV3Cu square pyramids that share corners with two equivalent S(4)V3Cu tetrahedra, corners with two equivalent S(5)MgV3Cu trigonal bipyramids, corners with four equivalent S(3)MgV3Cu trigonal bipyramids, edges with four equivalent S(6)MgV3Cu square pyramids, and edges with two equivalent S(5)MgV3Cu trigonal bipyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one V(2), two equivalent V(3), and one Cu(1) atom. In the third S site, S(3) is bonded to one Mg(1), one V(1), two equivalent V(3), and one Cu(2) atom to form SMgV3Cu trigonal bipyramids that share corners with two equivalent S(6)MgV3Cu square pyramids, corners with four equivalent S(1)MgV3Cu square pyramids,  a cornercorner with one S(4)V3Cu tetrahedra, edges with two equivalent S(6)MgV3Cu square pyramids,  an edgeedge with one S(4)V3Cu tetrahedra, and edges with four equivalent S(5)MgV3Cu trigonal bipyramids. In the fourth S site, S(4) is bonded to one V(2), two equivalent V(3), and one Cu(2) atom to form a mixture of corner and edge-sharing SV3Cu tetrahedra. In the fifth S site, S(5) is bonded to one Mg(1), one V(1), one V(2), one V(3), and one Cu(2) atom to form SMgV3Cu trigonal bipyramids that share  a cornercorner with one S(1)MgV3Cu square pyramid, corners with five equivalent S(6)MgV3Cu square pyramids,  a cornercorner with one S(4)V3Cu tetrahedra,  an edgeedge with one S(1)MgV3Cu square pyramid,  an edgeedge with one S(6)MgV3Cu square pyramid,  an edgeedge with one S(4)V3Cu tetrahedra, edges with two equivalent S(3)MgV3Cu trigonal bipyramids, and edges with two equivalent S(5)MgV3Cu trigonal bipyramids. In the sixth S site, S(6) is bonded to one Mg(1), one V(1), one V(2), one V(3), and one Cu(1) atom to form SMgV3Cu square pyramids that share corners with two equivalent S(4)V3Cu tetrahedra,  a cornercorner with one S(3)MgV3Cu trigonal bipyramid, corners with five equivalent S(5)MgV3Cu trigonal bipyramids, edges with two equivalent S(1)MgV3Cu square pyramids, edges with two equivalent S(6)MgV3Cu square pyramids,  an edgeedge with one S(3)MgV3Cu trigonal bipyramid, and  an edgeedge with one S(5)MgV3Cu trigonal bipyramid.