MgCo6(O2F)4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(5), two equivalent O(3), and one F(3) atom to form distorted MgO3F tetrahedra that share  a cornercorner with one Co(3)O3F3 octahedra, corners with two equivalent Co(1)O3F3 octahedra,  a cornercorner with one Co(2)O4F trigonal bipyramid,  an edgeedge with one Co(1)O3F3 octahedra, and  an edgeedge with one Co(5)O4F square pyramid. The corner-sharing octahedral tilt angles range from 2-58°. There are six inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(5), two equivalent O(3), one F(1), one F(2), and one F(3) atom to form CoO3F3 octahedra that share corners with three equivalent Co(5)O4F square pyramids, corners with two equivalent Mg(1)O3F tetrahedra,  a cornercorner with one Co(2)O4F trigonal bipyramid,  an edgeedge with one Co(3)O3F3 octahedra, and  an edgeedge with one Mg(1)O3F tetrahedra. In the second Co site, Co(2) is bonded to one O(1), one O(5), two equivalent O(2), and one F(4) atom to form distorted CoO4F trigonal bipyramids that share  a cornercorner with one Co(1)O3F3 octahedra, corners with three equivalent Co(6)O5 square pyramids,  a cornercorner with one Mg(1)O3F tetrahedra, and  an edgeedge with one Co(3)O3F3 octahedra. The corner-sharing octahedral tilt angles are 67°. In the third Co site, Co(3) is bonded to one O(1), two equivalent O(4), one F(2), one F(3), and one F(4) atom to form CoO3F3 octahedra that share corners with three equivalent Co(5)O4F square pyramids, corners with three equivalent Co(6)O5 square pyramids,  a cornercorner with one Mg(1)O3F tetrahedra,  an edgeedge with one Co(1)O3F3 octahedra, and  an edgeedge with one Co(2)O4F trigonal bipyramid. In the fourth Co site, Co(4) is bonded in a 5-coordinate geometry to two equivalent O(2), two equivalent O(3), and one F(1) atom. In the fifth Co site, Co(5) is bonded to two equivalent O(3), two equivalent O(4), and one F(2) atom to form distorted CoO4F square pyramids that share corners with three equivalent Co(1)O3F3 octahedra, corners with three equivalent Co(3)O3F3 octahedra,  an edgeedge with one Co(6)O5 square pyramid, and  an edgeedge with one Mg(1)O3F tetrahedra. The corner-sharing octahedral tilt angles range from 45-51°. In the sixth Co site, Co(6) is bonded to one O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted CoO5 square pyramids that share corners with three equivalent Co(3)O3F3 octahedra, corners with three equivalent Co(2)O4F trigonal bipyramids, and  an edgeedge with one Co(5)O4F square pyramid. The corner-sharing octahedral tilt angles range from 49-51°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Co(2), one Co(3), and one Co(6) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(2), one Co(4), and one Co(6) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Co(1), one Co(4), and one Co(5) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Co(3), one Co(5), and one Co(6) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Mg(1), one Co(1), and one Co(2) atom. There are four inequivalent F sites. In the first F site, F(3) is bonded in a T-shaped geometry to one Mg(1), one Co(1), and one Co(3) atom. In the second F site, F(4) is bonded in an L-shaped geometry to one Co(2) and one Co(3) atom. In the third F site, F(1) is bonded in a bent 150 degrees geometry to one Co(1) and one Co(4) atom. In the fourth F site, F(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one Co(5) atom.
MgCo6(O2F)4 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(5), two equivalent O(3), and one F(3) atom to form distorted MgO3F tetrahedra that share  a cornercorner with one Co(3)O3F3 octahedra, corners with two equivalent Co(1)O3F3 octahedra,  a cornercorner with one Co(2)O4F trigonal bipyramid,  an edgeedge with one Co(1)O3F3 octahedra, and  an edgeedge with one Co(5)O4F square pyramid. The corner-sharing octahedral tilt angles range from 2-58°. The Mg(1)-O(5) bond length is 1.92 Å. Both Mg(1)-O(3) bond lengths are 2.01 Å. The Mg(1)-F(3) bond length is 1.89 Å. There are six inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(5), two equivalent O(3), one F(1), one F(2), and one F(3) atom to form CoO3F3 octahedra that share corners with three equivalent Co(5)O4F square pyramids, corners with two equivalent Mg(1)O3F tetrahedra,  a cornercorner with one Co(2)O4F trigonal bipyramid,  an edgeedge with one Co(3)O3F3 octahedra, and  an edgeedge with one Mg(1)O3F tetrahedra. The Co(1)-O(5) bond length is 1.93 Å. Both Co(1)-O(3) bond lengths are 1.92 Å. The Co(1)-F(1) bond length is 1.92 Å. The Co(1)-F(2) bond length is 2.04 Å. The Co(1)-F(3) bond length is 2.10 Å. In the second Co site, Co(2) is bonded to one O(1), one O(5), two equivalent O(2), and one F(4) atom to form distorted CoO4F trigonal bipyramids that share  a cornercorner with one Co(1)O3F3 octahedra, corners with three equivalent Co(6)O5 square pyramids,  a cornercorner with one Mg(1)O3F tetrahedra, and  an edgeedge with one Co(3)O3F3 octahedra. The corner-sharing octahedral tilt angles are 67°. The Co(2)-O(1) bond length is 1.79 Å. The Co(2)-O(5) bond length is 1.85 Å. Both Co(2)-O(2) bond lengths are 1.93 Å. The Co(2)-F(4) bond length is 1.95 Å. In the third Co site, Co(3) is bonded to one O(1), two equivalent O(4), one F(2), one F(3), and one F(4) atom to form CoO3F3 octahedra that share corners with three equivalent Co(5)O4F square pyramids, corners with three equivalent Co(6)O5 square pyramids,  a cornercorner with one Mg(1)O3F tetrahedra,  an edgeedge with one Co(1)O3F3 octahedra, and  an edgeedge with one Co(2)O4F trigonal bipyramid. The Co(3)-O(1) bond length is 2.05 Å. Both Co(3)-O(4) bond lengths are 1.98 Å. The Co(3)-F(2) bond length is 2.12 Å. The Co(3)-F(3) bond length is 2.16 Å. The Co(3)-F(4) bond length is 2.01 Å. In the fourth Co site, Co(4) is bonded in a 5-coordinate geometry to two equivalent O(2), two equivalent O(3), and one F(1) atom. Both Co(4)-O(2) bond lengths are 1.92 Å. Both Co(4)-O(3) bond lengths are 2.16 Å. The Co(4)-F(1) bond length is 1.97 Å. In the fifth Co site, Co(5) is bonded to two equivalent O(3), two equivalent O(4), and one F(2) atom to form distorted CoO4F square pyramids that share corners with three equivalent Co(1)O3F3 octahedra, corners with three equivalent Co(3)O3F3 octahedra,  an edgeedge with one Co(6)O5 square pyramid, and  an edgeedge with one Mg(1)O3F tetrahedra. The corner-sharing octahedral tilt angles range from 45-51°. Both Co(5)-O(3) bond lengths are 1.96 Å. Both Co(5)-O(4) bond lengths are 1.86 Å. The Co(5)-F(2) bond length is 2.19 Å. In the sixth Co site, Co(6) is bonded to one O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted CoO5 square pyramids that share corners with three equivalent Co(3)O3F3 octahedra, corners with three equivalent Co(2)O4F trigonal bipyramids, and  an edgeedge with one Co(5)O4F square pyramid. The corner-sharing octahedral tilt angles range from 49-51°. The Co(6)-O(1) bond length is 2.06 Å. Both Co(6)-O(2) bond lengths are 1.87 Å. Both Co(6)-O(4) bond lengths are 1.85 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Co(2), one Co(3), and one Co(6) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(2), one Co(4), and one Co(6) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Co(1), one Co(4), and one Co(5) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Co(3), one Co(5), and one Co(6) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Mg(1), one Co(1), and one Co(2) atom. There are four inequivalent F sites. In the first F site, F(3) is bonded in a T-shaped geometry to one Mg(1), one Co(1), and one Co(3) atom. In the second F site, F(4) is bonded in an L-shaped geometry to one Co(2) and one Co(3) atom. In the third F site, F(1) is bonded in a bent 150 degrees geometry to one Co(1) and one Co(4) atom. In the fourth F site, F(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one Co(5) atom.