MgCu2(NiO2)4 crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Ni(2)O6 octahedra and edges with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form NiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. In the second Ni site, Ni(2) is bonded to six equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra and edges with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. Cu(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1) and three equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ni(1) and one Cu(1) atom to form distorted OCuNi3 tetrahedra that share corners with nine equivalent O(2)MgCuNi3 square pyramids, corners with three equivalent O(1)CuNi3 tetrahedra, and edges with three equivalent O(2)MgCuNi3 square pyramids. In the second O site, O(2) is bonded to one Mg(1), one Ni(2), two equivalent Ni(1), and one Cu(1) atom to form OMgCuNi3 square pyramids that share corners with six equivalent O(2)MgCuNi3 square pyramids, corners with three equivalent O(1)CuNi3 tetrahedra, edges with six equivalent O(2)MgCuNi3 square pyramids, and  an edgeedge with one O(1)CuNi3 tetrahedra.
MgCu2(NiO2)4 crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Ni(2)O6 octahedra and edges with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. All Mg(1)-O(2) bond lengths are 2.08 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form NiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. Both Ni(1)-O(1) bond lengths are 1.93 Å. All Ni(1)-O(2) bond lengths are 2.06 Å. In the second Ni site, Ni(2) is bonded to six equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra and edges with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. All Ni(2)-O(2) bond lengths are 2.15 Å. Cu(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1) and three equivalent O(2) atoms. The Cu(1)-O(1) bond length is 1.83 Å. All Cu(1)-O(2) bond lengths are 2.06 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ni(1) and one Cu(1) atom to form distorted OCuNi3 tetrahedra that share corners with nine equivalent O(2)MgCuNi3 square pyramids, corners with three equivalent O(1)CuNi3 tetrahedra, and edges with three equivalent O(2)MgCuNi3 square pyramids. In the second O site, O(2) is bonded to one Mg(1), one Ni(2), two equivalent Ni(1), and one Cu(1) atom to form OMgCuNi3 square pyramids that share corners with six equivalent O(2)MgCuNi3 square pyramids, corners with three equivalent O(1)CuNi3 tetrahedra, edges with six equivalent O(2)MgCuNi3 square pyramids, and  an edgeedge with one O(1)CuNi3 tetrahedra.