MgCu2(RhO2)4 crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent Rh(2)O6 octahedra and edges with six equivalent Rh(1)O6 octahedra. The corner-sharing octahedral tilt angles are 6°. There are two inequivalent Rh sites. In the first Rh site, Rh(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form RhO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Rh(2)O6 octahedra, and edges with four equivalent Rh(1)O6 octahedra. In the second Rh site, Rh(2) is bonded to six equivalent O(1) atoms to form RhO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra and edges with six equivalent Rh(1)O6 octahedra. The corner-sharing octahedral tilt angles are 6°. Cu(1) is bonded in a 4-coordinate geometry to one O(2) and three equivalent O(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Rh(2), two equivalent Rh(1), and one Cu(1) atom to form OMgCuRh3 square pyramids that share corners with six equivalent O(1)MgCuRh3 square pyramids, corners with three equivalent O(2)CuRh3 trigonal pyramids, edges with six equivalent O(1)MgCuRh3 square pyramids, and  an edgeedge with one O(2)CuRh3 trigonal pyramid. In the second O site, O(2) is bonded to three equivalent Rh(1) and one Cu(1) atom to form distorted OCuRh3 trigonal pyramids that share corners with nine equivalent O(1)MgCuRh3 square pyramids, corners with three equivalent O(2)CuRh3 trigonal pyramids, and edges with three equivalent O(1)MgCuRh3 square pyramids.
MgCu2(RhO2)4 crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent Rh(2)O6 octahedra and edges with six equivalent Rh(1)O6 octahedra. The corner-sharing octahedral tilt angles are 6°. All Mg(1)-O(1) bond lengths are 2.22 Å. There are two inequivalent Rh sites. In the first Rh site, Rh(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form RhO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Rh(2)O6 octahedra, and edges with four equivalent Rh(1)O6 octahedra. Both Rh(1)-O(2) bond lengths are 2.02 Å. All Rh(1)-O(1) bond lengths are 2.11 Å. In the second Rh site, Rh(2) is bonded to six equivalent O(1) atoms to form RhO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra and edges with six equivalent Rh(1)O6 octahedra. The corner-sharing octahedral tilt angles are 6°. All Rh(2)-O(1) bond lengths are 2.17 Å. Cu(1) is bonded in a 4-coordinate geometry to one O(2) and three equivalent O(1) atoms. The Cu(1)-O(2) bond length is 1.86 Å. All Cu(1)-O(1) bond lengths are 2.19 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Rh(2), two equivalent Rh(1), and one Cu(1) atom to form OMgCuRh3 square pyramids that share corners with six equivalent O(1)MgCuRh3 square pyramids, corners with three equivalent O(2)CuRh3 trigonal pyramids, edges with six equivalent O(1)MgCuRh3 square pyramids, and  an edgeedge with one O(2)CuRh3 trigonal pyramid. In the second O site, O(2) is bonded to three equivalent Rh(1) and one Cu(1) atom to form distorted OCuRh3 trigonal pyramids that share corners with nine equivalent O(1)MgCuRh3 square pyramids, corners with three equivalent O(2)CuRh3 trigonal pyramids, and edges with three equivalent O(1)MgCuRh3 square pyramids.