MgCu2(NiO2)4 crystallizes in the orthorhombic Imm2 space group. Mg(1) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(4) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NiO5 square pyramids that share corners with two equivalent Ni(2)O6 octahedra, corners with three equivalent Cu(2)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(1)O5 square pyramids. The corner-sharing octahedral tilt angles are 78°. In the second Ni site, Ni(2) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Ni(1)O5 square pyramids, corners with three equivalent Cu(2)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(1)O5 square pyramids. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 2-coordinate geometry to two equivalent O(1) and two equivalent O(3) atoms. In the second Cu site, Cu(2) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form distorted CuO4 tetrahedra that share corners with six equivalent Ni(2)O6 octahedra and corners with six equivalent Ni(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 54-80°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ni(1), two equivalent Ni(2), one Cu(1), and one Cu(2) atom to form distorted OCu2Ni3 trigonal bipyramids that share  a cornercorner with one O(1)Cu2Ni3 trigonal bipyramid, corners with two equivalent O(2)MgCuNi3 trigonal bipyramids, corners with two equivalent O(3)CuNi3 trigonal pyramids, edges with two equivalent O(2)MgCuNi3 trigonal bipyramids, edges with two equivalent O(3)CuNi3 trigonal pyramids, and  a faceface with one O(1)Cu2Ni3 trigonal bipyramid. In the second O site, O(2) is bonded to one Mg(1), one Ni(2), two equivalent Ni(1), and one Cu(2) atom to form distorted OMgCuNi3 trigonal bipyramids that share  a cornercorner with one O(2)MgCuNi3 trigonal bipyramid, corners with two equivalent O(1)Cu2Ni3 trigonal bipyramids, corners with five equivalent O(3)CuNi3 trigonal pyramids, edges with two equivalent O(1)Cu2Ni3 trigonal bipyramids, and  a faceface with one O(2)MgCuNi3 trigonal bipyramid. In the third O site, O(3) is bonded to one Ni(2), two equivalent Ni(1), and one Cu(1) atom to form distorted OCuNi3 trigonal pyramids that share corners with two equivalent O(1)Cu2Ni3 trigonal bipyramids, corners with five equivalent O(2)MgCuNi3 trigonal bipyramids,  a cornercorner with one O(3)CuNi3 trigonal pyramid, edges with two equivalent O(1)Cu2Ni3 trigonal bipyramids, and  an edgeedge with one O(3)CuNi3 trigonal pyramid. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(1) and two equivalent Ni(2) atoms.
MgCu2(NiO2)4 crystallizes in the orthorhombic Imm2 space group. Mg(1) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(4) atoms. Both Mg(1)-O(2) bond lengths are 2.02 Å. Both Mg(1)-O(4) bond lengths are 1.90 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NiO5 square pyramids that share corners with two equivalent Ni(2)O6 octahedra, corners with three equivalent Cu(2)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(1)O5 square pyramids. The corner-sharing octahedral tilt angles are 78°. The Ni(1)-O(1) bond length is 2.04 Å. Both Ni(1)-O(2) bond lengths are 2.08 Å. Both Ni(1)-O(3) bond lengths are 1.94 Å. In the second Ni site, Ni(2) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Ni(1)O5 square pyramids, corners with three equivalent Cu(2)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(1)O5 square pyramids. The Ni(2)-O(2) bond length is 2.13 Å. The Ni(2)-O(3) bond length is 2.11 Å. Both Ni(2)-O(1) bond lengths are 2.12 Å. Both Ni(2)-O(4) bond lengths are 1.99 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 2-coordinate geometry to two equivalent O(1) and two equivalent O(3) atoms. Both Cu(1)-O(1) bond lengths are 2.29 Å. Both Cu(1)-O(3) bond lengths are 1.83 Å. In the second Cu site, Cu(2) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form distorted CuO4 tetrahedra that share corners with six equivalent Ni(2)O6 octahedra and corners with six equivalent Ni(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 54-80°. Both Cu(2)-O(1) bond lengths are 2.07 Å. Both Cu(2)-O(2) bond lengths are 1.94 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ni(1), two equivalent Ni(2), one Cu(1), and one Cu(2) atom to form distorted OCu2Ni3 trigonal bipyramids that share  a cornercorner with one O(1)Cu2Ni3 trigonal bipyramid, corners with two equivalent O(2)MgCuNi3 trigonal bipyramids, corners with two equivalent O(3)CuNi3 trigonal pyramids, edges with two equivalent O(2)MgCuNi3 trigonal bipyramids, edges with two equivalent O(3)CuNi3 trigonal pyramids, and  a faceface with one O(1)Cu2Ni3 trigonal bipyramid. In the second O site, O(2) is bonded to one Mg(1), one Ni(2), two equivalent Ni(1), and one Cu(2) atom to form distorted OMgCuNi3 trigonal bipyramids that share  a cornercorner with one O(2)MgCuNi3 trigonal bipyramid, corners with two equivalent O(1)Cu2Ni3 trigonal bipyramids, corners with five equivalent O(3)CuNi3 trigonal pyramids, edges with two equivalent O(1)Cu2Ni3 trigonal bipyramids, and  a faceface with one O(2)MgCuNi3 trigonal bipyramid. In the third O site, O(3) is bonded to one Ni(2), two equivalent Ni(1), and one Cu(1) atom to form distorted OCuNi3 trigonal pyramids that share corners with two equivalent O(1)Cu2Ni3 trigonal bipyramids, corners with five equivalent O(2)MgCuNi3 trigonal bipyramids,  a cornercorner with one O(3)CuNi3 trigonal pyramid, edges with two equivalent O(1)Cu2Ni3 trigonal bipyramids, and  an edgeedge with one O(3)CuNi3 trigonal pyramid. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(1) and two equivalent Ni(2) atoms.