MgCo4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(2), one O(3), one O(4), one F(1), one F(2), and one F(3) atom to form MgO3F3 octahedra that share corners with four equivalent Co(4)O3F3 octahedra,  a cornercorner with one Co(1)O3F2 trigonal bipyramid, and  an edgeedge with one Co(1)O3F2 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 29-55°. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(3), one O(4), one F(1), and one F(4) atom to form distorted CoO3F2 trigonal bipyramids that share  a cornercorner with one Mg(1)O3F3 octahedra, corners with three equivalent Co(4)O3F3 octahedra, and  an edgeedge with one Mg(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-71°. In the second Co site, Co(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one F(1), one F(3), and one F(4) atom. In the third Co site, Co(3) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one F(2), and one F(3) atom. In the fourth Co site, Co(4) 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 CoO3F3 octahedra that share corners with four equivalent Mg(1)O3F3 octahedra and corners with three equivalent Co(1)O3F2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 29-55°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one Co(4) atom. In the second O site, O(2) is bonded to one Mg(1), one Co(2), one Co(3), and one Co(4) atom to form a mixture of distorted corner and edge-sharing OMgCo3 trigonal pyramids. 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(3), and one Co(4) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Co(1), one Co(2), and one Co(3) atom to form a mixture of corner and edge-sharing OMgCo3 tetrahedra. There are four inequivalent F sites. In the first F site, F(1) is bonded in a 3-coordinate geometry to one Mg(1), one Co(1), and one Co(2) atom. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Mg(1), one Co(3), and one Co(4) atom. In the third F site, F(3) is bonded in a 4-coordinate geometry to one Mg(1), one Co(2), one Co(3), and one Co(4) atom. In the fourth F site, F(4) is bonded in a 3-coordinate geometry to one Co(1), one Co(2), and one Co(4) atom.
MgCo4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(2), one O(3), one O(4), one F(1), one F(2), and one F(3) atom to form MgO3F3 octahedra that share corners with four equivalent Co(4)O3F3 octahedra,  a cornercorner with one Co(1)O3F2 trigonal bipyramid, and  an edgeedge with one Co(1)O3F2 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 29-55°. The Mg(1)-O(2) bond length is 2.08 Å. The Mg(1)-O(3) bond length is 2.13 Å. The Mg(1)-O(4) bond length is 2.02 Å. The Mg(1)-F(1) bond length is 1.94 Å. The Mg(1)-F(2) bond length is 2.02 Å. The Mg(1)-F(3) bond length is 2.03 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(3), one O(4), one F(1), and one F(4) atom to form distorted CoO3F2 trigonal bipyramids that share  a cornercorner with one Mg(1)O3F3 octahedra, corners with three equivalent Co(4)O3F3 octahedra, and  an edgeedge with one Mg(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-71°. The Co(1)-O(1) bond length is 2.05 Å. The Co(1)-O(3) bond length is 2.03 Å. The Co(1)-O(4) bond length is 2.00 Å. The Co(1)-F(1) bond length is 2.19 Å. The Co(1)-F(4) bond length is 2.02 Å. In the second Co site, Co(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one F(1), one F(3), and one F(4) atom. The Co(2)-O(1) bond length is 1.79 Å. The Co(2)-O(2) bond length is 2.06 Å. The Co(2)-O(4) bond length is 1.98 Å. The Co(2)-F(1) bond length is 2.08 Å. The Co(2)-F(3) bond length is 2.54 Å. The Co(2)-F(4) bond length is 2.03 Å. In the third Co site, Co(3) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one F(2), and one F(3) atom. The Co(3)-O(2) bond length is 1.87 Å. The Co(3)-O(3) bond length is 1.87 Å. The Co(3)-O(4) bond length is 1.92 Å. The Co(3)-F(2) bond length is 1.98 Å. The Co(3)-F(3) bond length is 2.19 Å. In the fourth Co site, Co(4) 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 CoO3F3 octahedra that share corners with four equivalent Mg(1)O3F3 octahedra and corners with three equivalent Co(1)O3F2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 29-55°. The Co(4)-O(1) bond length is 2.07 Å. The Co(4)-O(2) bond length is 2.05 Å. The Co(4)-O(3) bond length is 2.07 Å. The Co(4)-F(2) bond length is 2.17 Å. The Co(4)-F(3) bond length is 2.12 Å. The Co(4)-F(4) bond length is 2.35 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one Co(4) atom. In the second O site, O(2) is bonded to one Mg(1), one Co(2), one Co(3), and one Co(4) atom to form a mixture of distorted corner and edge-sharing OMgCo3 trigonal pyramids. 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(3), and one Co(4) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Co(1), one Co(2), and one Co(3) atom to form a mixture of corner and edge-sharing OMgCo3 tetrahedra. There are four inequivalent F sites. In the first F site, F(1) is bonded in a 3-coordinate geometry to one Mg(1), one Co(1), and one Co(2) atom. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Mg(1), one Co(3), and one Co(4) atom. In the third F site, F(3) is bonded in a 4-coordinate geometry to one Mg(1), one Co(2), one Co(3), and one Co(4) atom. In the fourth F site, F(4) is bonded in a 3-coordinate geometry to one Co(1), one Co(2), and one Co(4) atom.