MgCo2(NiS2)4 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent Ni(1), two equivalent S(2), and four equivalent S(3) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent S(1) and four equivalent S(3) atoms to form CoS6 octahedra that share edges with two equivalent Co(2)S6 octahedra and edges with four equivalent Ni(2)S6 octahedra. In the second Co site, Co(2) is bonded to two equivalent S(2) and four equivalent S(3) atoms to form CoS6 octahedra that share edges with two equivalent Co(1)S6 octahedra and edges with four equivalent Ni(2)S6 octahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 5-coordinate geometry to one Mg(1), one S(1), one S(2), and two equivalent S(3) atoms. In the second Ni site, Ni(2) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form NiS6 octahedra that share edges with two equivalent Co(1)S6 octahedra, edges with two equivalent Co(2)S6 octahedra, and edges with two equivalent Ni(2)S6 octahedra. There are three inequivalent S sites. In the first S site, S(1) is bonded to one Co(1), one Ni(1), and two equivalent Ni(2) atoms to form distorted SCoNi3 trigonal pyramids that share corners with three equivalent S(2)MgCoNi3 square pyramids, corners with six equivalent S(3)MgCo2Ni2 square pyramids, corners with three equivalent S(1)CoNi3 trigonal pyramids,  an edgeedge with one S(2)MgCoNi3 square pyramid, and edges with two equivalent S(3)MgCo2Ni2 square pyramids. In the second S site, S(2) is bonded to one Mg(1), one Co(2), one Ni(1), and two equivalent Ni(2) atoms to form SMgCoNi3 square pyramids that share corners with two equivalent S(3)MgCo2Ni2 square pyramids, corners with four equivalent S(2)MgCoNi3 square pyramids, corners with three equivalent S(1)CoNi3 trigonal pyramids, edges with six equivalent S(3)MgCo2Ni2 square pyramids, and  an edgeedge with one S(1)CoNi3 trigonal pyramid. In the third S site, S(3) is bonded to one Mg(1), one Co(1), one Co(2), one Ni(1), and one Ni(2) atom to form SMgCo2Ni2 square pyramids that share  a cornercorner with one S(2)MgCoNi3 square pyramid, corners with five equivalent S(3)MgCo2Ni2 square pyramids, corners with three equivalent S(1)CoNi3 trigonal pyramids, edges with three equivalent S(3)MgCo2Ni2 square pyramids, edges with three equivalent S(2)MgCoNi3 square pyramids, and  an edgeedge with one S(1)CoNi3 trigonal pyramid.
MgCo2(NiS2)4 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent Ni(1), two equivalent S(2), and four equivalent S(3) atoms. Both Mg(1)-Ni(1) bond lengths are 2.41 Å. Both Mg(1)-S(2) bond lengths are 2.54 Å. All Mg(1)-S(3) bond lengths are 2.53 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent S(1) and four equivalent S(3) atoms to form CoS6 octahedra that share edges with two equivalent Co(2)S6 octahedra and edges with four equivalent Ni(2)S6 octahedra. Both Co(1)-S(1) bond lengths are 2.24 Å. All Co(1)-S(3) bond lengths are 2.32 Å. In the second Co site, Co(2) is bonded to two equivalent S(2) and four equivalent S(3) atoms to form CoS6 octahedra that share edges with two equivalent Co(1)S6 octahedra and edges with four equivalent Ni(2)S6 octahedra. Both Co(2)-S(2) bond lengths are 2.27 Å. All Co(2)-S(3) bond lengths are 2.26 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 5-coordinate geometry to one Mg(1), one S(1), one S(2), and two equivalent S(3) atoms. The Ni(1)-S(1) bond length is 2.16 Å. The Ni(1)-S(2) bond length is 2.26 Å. Both Ni(1)-S(3) bond lengths are 2.30 Å. In the second Ni site, Ni(2) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form NiS6 octahedra that share edges with two equivalent Co(1)S6 octahedra, edges with two equivalent Co(2)S6 octahedra, and edges with two equivalent Ni(2)S6 octahedra. Both Ni(2)-S(1) bond lengths are 2.25 Å. Both Ni(2)-S(2) bond lengths are 2.36 Å. Both Ni(2)-S(3) bond lengths are 2.36 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded to one Co(1), one Ni(1), and two equivalent Ni(2) atoms to form distorted SCoNi3 trigonal pyramids that share corners with three equivalent S(2)MgCoNi3 square pyramids, corners with six equivalent S(3)MgCo2Ni2 square pyramids, corners with three equivalent S(1)CoNi3 trigonal pyramids,  an edgeedge with one S(2)MgCoNi3 square pyramid, and edges with two equivalent S(3)MgCo2Ni2 square pyramids. In the second S site, S(2) is bonded to one Mg(1), one Co(2), one Ni(1), and two equivalent Ni(2) atoms to form SMgCoNi3 square pyramids that share corners with two equivalent S(3)MgCo2Ni2 square pyramids, corners with four equivalent S(2)MgCoNi3 square pyramids, corners with three equivalent S(1)CoNi3 trigonal pyramids, edges with six equivalent S(3)MgCo2Ni2 square pyramids, and  an edgeedge with one S(1)CoNi3 trigonal pyramid. In the third S site, S(3) is bonded to one Mg(1), one Co(1), one Co(2), one Ni(1), and one Ni(2) atom to form SMgCo2Ni2 square pyramids that share  a cornercorner with one S(2)MgCoNi3 square pyramid, corners with five equivalent S(3)MgCo2Ni2 square pyramids, corners with three equivalent S(1)CoNi3 trigonal pyramids, edges with three equivalent S(3)MgCo2Ni2 square pyramids, edges with three equivalent S(2)MgCoNi3 square pyramids, and  an edgeedge with one S(1)CoNi3 trigonal pyramid.