MgCu2(O2F)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(4), two equivalent O(1), one F(1), and two equivalent F(2) atoms to form MgO3F3 octahedra that share  a cornercorner with one Cu(1)O3F tetrahedra, edges with two equivalent Mg(1)O3F3 octahedra, and edges with four equivalent Cu(2)O3F3 octahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(2), two equivalent O(3), and one F(1) atom to form distorted CuO3F tetrahedra that share  a cornercorner with one Mg(1)O3F3 octahedra, corners with two equivalent Cu(2)O3F3 octahedra,  a cornercorner with one O(1)Mg2CuO tetrahedra, corners with two equivalent Cu(1)O3F tetrahedra, and corners with two equivalent O(4)MgCu2O tetrahedra. The corner-sharing octahedral tilt angles range from 46-74°. In the second Cu site, Cu(2) is bonded to one O(1), two equivalent O(4), one F(2), and two equivalent F(1) atoms to form distorted CuO3F3 octahedra that share corners with two equivalent Cu(1)O3F tetrahedra, edges with two equivalent Cu(2)O3F3 octahedra, and edges with four equivalent Mg(1)O3F3 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), one Cu(2), and one O(2) atom to form distorted OMg2CuO tetrahedra that share  a cornercorner with one Cu(1)O3F tetrahedra, corners with two equivalent O(1)Mg2CuO tetrahedra, and corners with four equivalent O(4)MgCu2O tetrahedra. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Cu(1) and one O(1) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Cu(1) and one O(4) atom. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Cu(2), and one O(3) atom to form distorted OMgCu2O tetrahedra that share corners with two equivalent Cu(1)O3F tetrahedra, corners with two equivalent O(4)MgCu2O tetrahedra, and corners with four equivalent O(1)Mg2CuO tetrahedra. There are two inequivalent F sites. In the first F site, F(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Cu(1), and two equivalent Cu(2) atoms. In the second F site, F(2) is bonded in a trigonal non-coplanar geometry to two equivalent Mg(1) and one Cu(2) atom.
MgCu2(O2F)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(4), two equivalent O(1), one F(1), and two equivalent F(2) atoms to form MgO3F3 octahedra that share  a cornercorner with one Cu(1)O3F tetrahedra, edges with two equivalent Mg(1)O3F3 octahedra, and edges with four equivalent Cu(2)O3F3 octahedra. The Mg(1)-O(4) bond length is 2.09 Å. Both Mg(1)-O(1) bond lengths are 2.13 Å. The Mg(1)-F(1) bond length is 1.98 Å. Both Mg(1)-F(2) bond lengths are 2.10 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(2), two equivalent O(3), and one F(1) atom to form distorted CuO3F tetrahedra that share  a cornercorner with one Mg(1)O3F3 octahedra, corners with two equivalent Cu(2)O3F3 octahedra,  a cornercorner with one O(1)Mg2CuO tetrahedra, corners with two equivalent Cu(1)O3F tetrahedra, and corners with two equivalent O(4)MgCu2O tetrahedra. The corner-sharing octahedral tilt angles range from 46-74°. The Cu(1)-O(2) bond length is 1.87 Å. Both Cu(1)-O(3) bond lengths are 1.94 Å. The Cu(1)-F(1) bond length is 2.05 Å. In the second Cu site, Cu(2) is bonded to one O(1), two equivalent O(4), one F(2), and two equivalent F(1) atoms to form distorted CuO3F3 octahedra that share corners with two equivalent Cu(1)O3F tetrahedra, edges with two equivalent Cu(2)O3F3 octahedra, and edges with four equivalent Mg(1)O3F3 octahedra. The Cu(2)-O(1) bond length is 1.96 Å. Both Cu(2)-O(4) bond lengths are 2.06 Å. The Cu(2)-F(2) bond length is 2.06 Å. Both Cu(2)-F(1) bond lengths are 2.43 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), one Cu(2), and one O(2) atom to form distorted OMg2CuO tetrahedra that share  a cornercorner with one Cu(1)O3F tetrahedra, corners with two equivalent O(1)Mg2CuO tetrahedra, and corners with four equivalent O(4)MgCu2O tetrahedra. The O(1)-O(2) bond length is 1.42 Å. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Cu(1) and one O(1) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Cu(1) and one O(4) atom. The O(3)-O(4) bond length is 1.45 Å. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Cu(2), and one O(3) atom to form distorted OMgCu2O tetrahedra that share corners with two equivalent Cu(1)O3F tetrahedra, corners with two equivalent O(4)MgCu2O tetrahedra, and corners with four equivalent O(1)Mg2CuO tetrahedra. There are two inequivalent F sites. In the first F site, F(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Cu(1), and two equivalent Cu(2) atoms. In the second F site, F(2) is bonded in a trigonal non-coplanar geometry to two equivalent Mg(1) and one Cu(2) atom.