MgTi(CuS)4 crystallizes in the tetragonal I-4 space group. Mg(1) is bonded to two equivalent Cu(1), four equivalent Cu(2), and four equivalent S(1) atoms to form distorted MgCu6S4 tetrahedra that share corners with four equivalent Mg(1)Cu6S4 tetrahedra, edges with four equivalent Cu(2)Mg2TiS4 tetrahedra, and faces with four equivalent Ti(1)Cu6S4 tetrahedra. Ti(1) is bonded to two equivalent Cu(2), four equivalent Cu(1), and four equivalent S(1) atoms to form distorted TiCu6S4 tetrahedra that share corners with four equivalent Ti(1)Cu6S4 tetrahedra, corners with four equivalent Cu(2)Mg2TiS4 tetrahedra, edges with two equivalent Cu(2)Mg2TiS4 tetrahedra, and faces with four equivalent Mg(1)Cu6S4 tetrahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 7-coordinate geometry to one Mg(1), two equivalent Ti(1), and four equivalent S(1) atoms. In the second Cu site, Cu(2) is bonded to two equivalent Mg(1), one Ti(1), and four equivalent S(1) atoms to form distorted CuMg2TiS4 tetrahedra that share corners with two equivalent Ti(1)Cu6S4 tetrahedra, corners with three equivalent Cu(2)Mg2TiS4 tetrahedra,  an edgeedge with one Ti(1)Cu6S4 tetrahedra, edges with two equivalent Mg(1)Cu6S4 tetrahedra, and edges with four equivalent Cu(2)Mg2TiS4 tetrahedra. S(1) is bonded in a 6-coordinate geometry to one Mg(1), one Ti(1), two equivalent Cu(1), and two equivalent Cu(2) atoms.
MgTi(CuS)4 crystallizes in the tetragonal I-4 space group. Mg(1) is bonded to two equivalent Cu(1), four equivalent Cu(2), and four equivalent S(1) atoms to form distorted MgCu6S4 tetrahedra that share corners with four equivalent Mg(1)Cu6S4 tetrahedra, edges with four equivalent Cu(2)Mg2TiS4 tetrahedra, and faces with four equivalent Ti(1)Cu6S4 tetrahedra. Both Mg(1)-Cu(1) bond lengths are 2.77 Å. All Mg(1)-Cu(2) bond lengths are 2.79 Å. All Mg(1)-S(1) bond lengths are 2.45 Å. Ti(1) is bonded to two equivalent Cu(2), four equivalent Cu(1), and four equivalent S(1) atoms to form distorted TiCu6S4 tetrahedra that share corners with four equivalent Ti(1)Cu6S4 tetrahedra, corners with four equivalent Cu(2)Mg2TiS4 tetrahedra, edges with two equivalent Cu(2)Mg2TiS4 tetrahedra, and faces with four equivalent Mg(1)Cu6S4 tetrahedra. Both Ti(1)-Cu(2) bond lengths are 2.83 Å. All Ti(1)-Cu(1) bond lengths are 2.79 Å. All Ti(1)-S(1) bond lengths are 2.41 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 7-coordinate geometry to one Mg(1), two equivalent Ti(1), and four equivalent S(1) atoms. There are two shorter (2.37 Å) and two longer (2.46 Å) Cu(1)-S(1) bond lengths. In the second Cu site, Cu(2) is bonded to two equivalent Mg(1), one Ti(1), and four equivalent S(1) atoms to form distorted CuMg2TiS4 tetrahedra that share corners with two equivalent Ti(1)Cu6S4 tetrahedra, corners with three equivalent Cu(2)Mg2TiS4 tetrahedra,  an edgeedge with one Ti(1)Cu6S4 tetrahedra, edges with two equivalent Mg(1)Cu6S4 tetrahedra, and edges with four equivalent Cu(2)Mg2TiS4 tetrahedra. There are two shorter (2.37 Å) and two longer (2.44 Å) Cu(2)-S(1) bond lengths. S(1) is bonded in a 6-coordinate geometry to one Mg(1), one Ti(1), two equivalent Cu(1), and two equivalent Cu(2) atoms.