MgCo4(CuO4)2 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Co(3)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Cu(1)O6 octahedra, and edges with two equivalent Cu(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the second Co site, Co(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CoO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, edges with two equivalent Cu(1)O6 octahedra, and edges with two equivalent Cu(2)O6 octahedra. In the third Co site, Co(3) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Cu(1)O6 octahedra, and edges with two equivalent Cu(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form CuO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and edges with two equivalent Cu(2)O6 octahedra. In the second Cu site, Cu(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form CuO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and edges with two equivalent Cu(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Co(1), one Co(2), one Cu(1), and one Cu(2) atom to form OCo2Cu2 tetrahedra that share corners with three equivalent O(4)MgCo2Cu2 square pyramids, corners with three equivalent O(2)MgCo3Cu square pyramids, corners with three equivalent O(3)MgCo3Cu square pyramids, corners with three equivalent O(1)Co2Cu2 tetrahedra,  an edgeedge with one O(4)MgCo2Cu2 square pyramid,  an edgeedge with one O(2)MgCo3Cu square pyramid, and  an edgeedge with one O(3)MgCo3Cu square pyramid. In the second O site, O(2) is bonded to one Mg(1), one Co(1), one Co(2), one Co(3), and one Cu(1) atom to form OMgCo3Cu square pyramids that share  a cornercorner with one O(4)MgCo2Cu2 square pyramid,  a cornercorner with one O(3)MgCo3Cu square pyramid, corners with four equivalent O(2)MgCo3Cu square pyramids, corners with three equivalent O(1)Co2Cu2 tetrahedra, edges with three equivalent O(4)MgCo2Cu2 square pyramids, edges with three equivalent O(3)MgCo3Cu square pyramids, and  an edgeedge with one O(1)Co2Cu2 tetrahedra. In the third O site, O(3) is bonded to one Mg(1), one Co(1), one Co(2), one Co(3), and one Cu(2) atom to form OMgCo3Cu square pyramids that share  a cornercorner with one O(4)MgCo2Cu2 square pyramid,  a cornercorner with one O(2)MgCo3Cu square pyramid, corners with four equivalent O(3)MgCo3Cu square pyramids, corners with three equivalent O(1)Co2Cu2 tetrahedra, edges with three equivalent O(4)MgCo2Cu2 square pyramids, edges with three equivalent O(2)MgCo3Cu square pyramids, and  an edgeedge with one O(1)Co2Cu2 tetrahedra. In the fourth O site, O(4) is bonded to one Mg(1), one Co(1), one Co(3), one Cu(1), and one Cu(2) atom to form OMgCo2Cu2 square pyramids that share  a cornercorner with one O(2)MgCo3Cu square pyramid,  a cornercorner with one O(3)MgCo3Cu square pyramid, corners with four equivalent O(4)MgCo2Cu2 square pyramids, corners with three equivalent O(1)Co2Cu2 tetrahedra, edges with three equivalent O(2)MgCo3Cu square pyramids, edges with three equivalent O(3)MgCo3Cu square pyramids, and  an edgeedge with one O(1)Co2Cu2 tetrahedra.
MgCo4(CuO4)2 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Co(3)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Cu(1)O6 octahedra, and edges with two equivalent Cu(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. Both Mg(1)-O(2) bond lengths are 2.12 Å. Both Mg(1)-O(3) bond lengths are 2.11 Å. Both Mg(1)-O(4) bond lengths are 2.10 Å. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Co(1)-O(1) bond length is 1.87 Å. The Co(1)-O(2) bond length is 2.03 Å. The Co(1)-O(3) bond length is 2.02 Å. The Co(1)-O(4) bond length is 2.02 Å. In the second Co site, Co(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CoO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, edges with two equivalent Cu(1)O6 octahedra, and edges with two equivalent Cu(2)O6 octahedra. Both Co(2)-O(1) bond lengths are 1.95 Å. Both Co(2)-O(2) bond lengths are 2.12 Å. Both Co(2)-O(3) bond lengths are 2.15 Å. In the third Co site, Co(3) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Cu(1)O6 octahedra, and edges with two equivalent Cu(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. Both Co(3)-O(2) bond lengths are 2.15 Å. Both Co(3)-O(3) bond lengths are 2.14 Å. Both Co(3)-O(4) bond lengths are 2.21 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form CuO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and edges with two equivalent Cu(2)O6 octahedra. Both Cu(1)-O(1) bond lengths are 1.92 Å. Both Cu(1)-O(2) bond lengths are 2.14 Å. Both Cu(1)-O(4) bond lengths are 2.15 Å. In the second Cu site, Cu(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form CuO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and edges with two equivalent Cu(1)O6 octahedra. Both Cu(2)-O(1) bond lengths are 1.92 Å. Both Cu(2)-O(3) bond lengths are 2.13 Å. Both Cu(2)-O(4) bond lengths are 2.14 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Co(1), one Co(2), one Cu(1), and one Cu(2) atom to form OCo2Cu2 tetrahedra that share corners with three equivalent O(4)MgCo2Cu2 square pyramids, corners with three equivalent O(2)MgCo3Cu square pyramids, corners with three equivalent O(3)MgCo3Cu square pyramids, corners with three equivalent O(1)Co2Cu2 tetrahedra,  an edgeedge with one O(4)MgCo2Cu2 square pyramid,  an edgeedge with one O(2)MgCo3Cu square pyramid, and  an edgeedge with one O(3)MgCo3Cu square pyramid. In the second O site, O(2) is bonded to one Mg(1), one Co(1), one Co(2), one Co(3), and one Cu(1) atom to form OMgCo3Cu square pyramids that share  a cornercorner with one O(4)MgCo2Cu2 square pyramid,  a cornercorner with one O(3)MgCo3Cu square pyramid, corners with four equivalent O(2)MgCo3Cu square pyramids, corners with three equivalent O(1)Co2Cu2 tetrahedra, edges with three equivalent O(4)MgCo2Cu2 square pyramids, edges with three equivalent O(3)MgCo3Cu square pyramids, and  an edgeedge with one O(1)Co2Cu2 tetrahedra. In the third O site, O(3) is bonded to one Mg(1), one Co(1), one Co(2), one Co(3), and one Cu(2) atom to form OMgCo3Cu square pyramids that share  a cornercorner with one O(4)MgCo2Cu2 square pyramid,  a cornercorner with one O(2)MgCo3Cu square pyramid, corners with four equivalent O(3)MgCo3Cu square pyramids, corners with three equivalent O(1)Co2Cu2 tetrahedra, edges with three equivalent O(4)MgCo2Cu2 square pyramids, edges with three equivalent O(2)MgCo3Cu square pyramids, and  an edgeedge with one O(1)Co2Cu2 tetrahedra. In the fourth O site, O(4) is bonded to one Mg(1), one Co(1), one Co(3), one Cu(1), and one Cu(2) atom to form OMgCo2Cu2 square pyramids that share  a cornercorner with one O(2)MgCo3Cu square pyramid,  a cornercorner with one O(3)MgCo3Cu square pyramid, corners with four equivalent O(4)MgCo2Cu2 square pyramids, corners with three equivalent O(1)Co2Cu2 tetrahedra, edges with three equivalent O(2)MgCo3Cu square pyramids, edges with three equivalent O(3)MgCo3Cu square pyramids, and  an edgeedge with one O(1)Co2Cu2 tetrahedra.