MgCu6(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 4-coordinate geometry to one O(3), one F(1), one F(3), and one F(4) atom. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to one O(1), one O(4), one F(2), and one F(4) atom. In the second Cu site, Cu(2) is bonded in a distorted rectangular see-saw-like geometry to one O(2), one O(3), one F(1), and one F(2) atom. In the third Cu site, Cu(3) is bonded to one O(1), one O(2), one O(3), one F(2), one F(3), and one F(4) atom to form distorted edge-sharing CuO3F3 octahedra. In the fourth Cu site, Cu(4) is bonded to one O(1), one O(2), one O(4), one F(1), one F(2), and one F(4) atom to form distorted edge-sharing CuO3F3 octahedra. In the fifth Cu site, Cu(5) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one F(3), and one F(4) atom. In the sixth Cu site, Cu(6) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(4), and one F(2) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Cu(1), one Cu(3), one Cu(4), and one Cu(5) atom. In the second O site, O(2) is bonded to one Cu(2), one Cu(3), one Cu(4), and one Cu(6) atom to form OCu4 tetrahedra that share corners with two equivalent O(4)Cu4 tetrahedra,  a cornercorner with one O(3)MgCu4 trigonal bipyramid, and  an edgeedge with one O(3)MgCu4 trigonal bipyramid. In the third O site, O(3) is bonded to one Mg(1), one Cu(2), one Cu(3), one Cu(5), and one Cu(6) atom to form a mixture of edge and corner-sharing OMgCu4 trigonal bipyramids. In the fourth O site, O(4) is bonded to one Cu(1), one Cu(4), one Cu(5), and one Cu(6) atom to form distorted OCu4 tetrahedra that share corners with two equivalent O(2)Cu4 tetrahedra and corners with two equivalent O(3)MgCu4 trigonal bipyramids. There are four inequivalent F sites. In the first F site, F(1) is bonded in a 1-coordinate geometry to one Mg(1), one Cu(2), and one Cu(4) atom. In the second F site, F(2) is bonded in a 5-coordinate geometry to one Cu(1), one Cu(2), one Cu(3), one Cu(4), and one Cu(6) atom. In the third F site, F(3) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(3), and one Cu(5) atom. In the fourth F site, F(4) is bonded in a 5-coordinate geometry to one Mg(1), one Cu(1), one Cu(3), one Cu(4), and one Cu(5) atom.
MgCu6(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 4-coordinate geometry to one O(3), one F(1), one F(3), and one F(4) atom. The Mg(1)-O(3) bond length is 2.04 Å. The Mg(1)-F(1) bond length is 1.93 Å. The Mg(1)-F(3) bond length is 1.93 Å. The Mg(1)-F(4) bond length is 1.94 Å. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to one O(1), one O(4), one F(2), and one F(4) atom. The Cu(1)-O(1) bond length is 1.89 Å. The Cu(1)-O(4) bond length is 1.87 Å. The Cu(1)-F(2) bond length is 2.50 Å. The Cu(1)-F(4) bond length is 2.29 Å. In the second Cu site, Cu(2) is bonded in a distorted rectangular see-saw-like geometry to one O(2), one O(3), one F(1), and one F(2) atom. The Cu(2)-O(2) bond length is 1.86 Å. The Cu(2)-O(3) bond length is 1.99 Å. The Cu(2)-F(1) bond length is 2.30 Å. The Cu(2)-F(2) bond length is 2.22 Å. In the third Cu site, Cu(3) is bonded to one O(1), one O(2), one O(3), one F(2), one F(3), and one F(4) atom to form distorted edge-sharing CuO3F3 octahedra. The Cu(3)-O(1) bond length is 1.98 Å. The Cu(3)-O(2) bond length is 1.96 Å. The Cu(3)-O(3) bond length is 2.07 Å. The Cu(3)-F(2) bond length is 2.29 Å. The Cu(3)-F(3) bond length is 2.30 Å. The Cu(3)-F(4) bond length is 2.50 Å. In the fourth Cu site, Cu(4) is bonded to one O(1), one O(2), one O(4), one F(1), one F(2), and one F(4) atom to form distorted edge-sharing CuO3F3 octahedra. The Cu(4)-O(1) bond length is 1.94 Å. The Cu(4)-O(2) bond length is 1.90 Å. The Cu(4)-O(4) bond length is 2.25 Å. The Cu(4)-F(1) bond length is 2.38 Å. The Cu(4)-F(2) bond length is 2.38 Å. The Cu(4)-F(4) bond length is 2.32 Å. In the fifth Cu site, Cu(5) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one F(3), and one F(4) atom. The Cu(5)-O(1) bond length is 2.02 Å. The Cu(5)-O(3) bond length is 1.95 Å. The Cu(5)-O(4) bond length is 1.92 Å. The Cu(5)-F(3) bond length is 2.40 Å. The Cu(5)-F(4) bond length is 2.52 Å. In the sixth Cu site, Cu(6) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(4), and one F(2) atom. The Cu(6)-O(2) bond length is 1.96 Å. The Cu(6)-O(3) bond length is 2.11 Å. The Cu(6)-O(4) bond length is 1.94 Å. The Cu(6)-F(2) bond length is 2.07 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Cu(1), one Cu(3), one Cu(4), and one Cu(5) atom. In the second O site, O(2) is bonded to one Cu(2), one Cu(3), one Cu(4), and one Cu(6) atom to form OCu4 tetrahedra that share corners with two equivalent O(4)Cu4 tetrahedra,  a cornercorner with one O(3)MgCu4 trigonal bipyramid, and  an edgeedge with one O(3)MgCu4 trigonal bipyramid. In the third O site, O(3) is bonded to one Mg(1), one Cu(2), one Cu(3), one Cu(5), and one Cu(6) atom to form a mixture of edge and corner-sharing OMgCu4 trigonal bipyramids. In the fourth O site, O(4) is bonded to one Cu(1), one Cu(4), one Cu(5), and one Cu(6) atom to form distorted OCu4 tetrahedra that share corners with two equivalent O(2)Cu4 tetrahedra and corners with two equivalent O(3)MgCu4 trigonal bipyramids. There are four inequivalent F sites. In the first F site, F(1) is bonded in a 1-coordinate geometry to one Mg(1), one Cu(2), and one Cu(4) atom. In the second F site, F(2) is bonded in a 5-coordinate geometry to one Cu(1), one Cu(2), one Cu(3), one Cu(4), and one Cu(6) atom. In the third F site, F(3) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(3), and one Cu(5) atom. In the fourth F site, F(4) is bonded in a 5-coordinate geometry to one Mg(1), one Cu(1), one Cu(3), one Cu(4), and one Cu(5) atom.