MgCo4(O3F)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(3), one O(5), one O(6), one F(1), and one F(2) atom to form distorted MgO4F2 octahedra that share corners with four equivalent Co(1)O4F2 octahedra,  a cornercorner with one Co(3)O4F square pyramid,  a cornercorner with one Co(4)O5 trigonal bipyramid,  an edgeedge with one Co(3)O4F square pyramid,  an edgeedge with one Co(4)O5 trigonal bipyramid, and faces with two equivalent Co(2)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 38-51°. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(2), one O(4), one O(6), one F(1), and one F(2) atom to form CoO4F2 octahedra that share corners with four equivalent Mg(1)O4F2 octahedra, corners with three equivalent Co(3)O4F square pyramids, corners with three equivalent Co(4)O5 trigonal bipyramids, and edges with two equivalent Co(2)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 38-51°. In the second Co site, Co(2) is bonded to one O(1), one O(3), one O(5), one O(6), one F(1), and one F(2) atom to form CoO4F2 octahedra that share corners with three equivalent Co(3)O4F square pyramids, corners with three equivalent Co(4)O5 trigonal bipyramids, edges with two equivalent Co(1)O4F2 octahedra, and faces with two equivalent Mg(1)O4F2 octahedra. In the third Co site, Co(3) is bonded to one O(2), one O(3), one O(4), one O(5), and one F(1) atom to form distorted CoO4F square pyramids that share  a cornercorner with one Mg(1)O4F2 octahedra, corners with three equivalent Co(1)O4F2 octahedra, corners with three equivalent Co(2)O4F2 octahedra,  an edgeedge with one Mg(1)O4F2 octahedra, and edges with two equivalent Co(4)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 42-80°. In the fourth Co site, Co(4) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form distorted CoO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O4F2 octahedra, corners with three equivalent Co(1)O4F2 octahedra, corners with three equivalent Co(2)O4F2 octahedra,  an edgeedge with one Mg(1)O4F2 octahedra, and edges with two equivalent Co(3)O4F square pyramids. The corner-sharing octahedral tilt angles range from 38-63°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Co(1), one Co(2), and one Co(4) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one Co(4) atom. In the third O site, O(3) is bonded to one Mg(1), one Co(2), one Co(3), and one Co(4) atom to form a mixture of corner and edge-sharing OMgCo3 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one Co(4) atom. In the fifth O site, O(5) 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 tetrahedra. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Mg(1), one Co(1), and one Co(2) atom. There are two inequivalent F sites. In the first F site, F(1) is bonded in a 4-coordinate geometry to one Mg(1), one Co(1), one Co(2), and one Co(3) atom. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Mg(1), one Co(1), and one Co(2) atom.
MgCo4(O3F)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(3), one O(5), one O(6), one F(1), and one F(2) atom to form distorted MgO4F2 octahedra that share corners with four equivalent Co(1)O4F2 octahedra,  a cornercorner with one Co(3)O4F square pyramid,  a cornercorner with one Co(4)O5 trigonal bipyramid,  an edgeedge with one Co(3)O4F square pyramid,  an edgeedge with one Co(4)O5 trigonal bipyramid, and faces with two equivalent Co(2)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 38-51°. The Mg(1)-O(1) bond length is 2.19 Å. The Mg(1)-O(3) bond length is 2.07 Å. The Mg(1)-O(5) bond length is 1.99 Å. The Mg(1)-O(6) bond length is 2.02 Å. The Mg(1)-F(1) bond length is 2.07 Å. The Mg(1)-F(2) bond length is 1.99 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(2), one O(4), one O(6), one F(1), and one F(2) atom to form CoO4F2 octahedra that share corners with four equivalent Mg(1)O4F2 octahedra, corners with three equivalent Co(3)O4F square pyramids, corners with three equivalent Co(4)O5 trigonal bipyramids, and edges with two equivalent Co(2)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 38-51°. The Co(1)-O(1) bond length is 2.03 Å. The Co(1)-O(2) bond length is 1.92 Å. The Co(1)-O(4) bond length is 1.91 Å. The Co(1)-O(6) bond length is 1.87 Å. The Co(1)-F(1) bond length is 2.20 Å. The Co(1)-F(2) bond length is 2.16 Å. In the second Co site, Co(2) is bonded to one O(1), one O(3), one O(5), one O(6), one F(1), and one F(2) atom to form CoO4F2 octahedra that share corners with three equivalent Co(3)O4F square pyramids, corners with three equivalent Co(4)O5 trigonal bipyramids, edges with two equivalent Co(1)O4F2 octahedra, and faces with two equivalent Mg(1)O4F2 octahedra. The Co(2)-O(1) bond length is 2.00 Å. The Co(2)-O(3) bond length is 1.94 Å. The Co(2)-O(5) bond length is 1.95 Å. The Co(2)-O(6) bond length is 1.83 Å. The Co(2)-F(1) bond length is 2.05 Å. The Co(2)-F(2) bond length is 2.07 Å. In the third Co site, Co(3) is bonded to one O(2), one O(3), one O(4), one O(5), and one F(1) atom to form distorted CoO4F square pyramids that share  a cornercorner with one Mg(1)O4F2 octahedra, corners with three equivalent Co(1)O4F2 octahedra, corners with three equivalent Co(2)O4F2 octahedra,  an edgeedge with one Mg(1)O4F2 octahedra, and edges with two equivalent Co(4)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 42-80°. The Co(3)-O(2) bond length is 1.84 Å. The Co(3)-O(3) bond length is 1.86 Å. The Co(3)-O(4) bond length is 1.83 Å. The Co(3)-O(5) bond length is 1.89 Å. The Co(3)-F(1) bond length is 2.52 Å. In the fourth Co site, Co(4) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form distorted CoO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O4F2 octahedra, corners with three equivalent Co(1)O4F2 octahedra, corners with three equivalent Co(2)O4F2 octahedra,  an edgeedge with one Mg(1)O4F2 octahedra, and edges with two equivalent Co(3)O4F square pyramids. The corner-sharing octahedral tilt angles range from 38-63°. The Co(4)-O(1) bond length is 1.92 Å. The Co(4)-O(2) bond length is 1.97 Å. The Co(4)-O(3) bond length is 2.02 Å. The Co(4)-O(4) bond length is 1.94 Å. The Co(4)-O(5) bond length is 2.01 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Co(1), one Co(2), and one Co(4) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one Co(4) atom. In the third O site, O(3) is bonded to one Mg(1), one Co(2), one Co(3), and one Co(4) atom to form a mixture of corner and edge-sharing OMgCo3 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one Co(4) atom. In the fifth O site, O(5) 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 tetrahedra. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Mg(1), one Co(1), and one Co(2) atom. There are two inequivalent F sites. In the first F site, F(1) is bonded in a 4-coordinate geometry to one Mg(1), one Co(1), one Co(2), and one Co(3) atom. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Mg(1), one Co(1), and one Co(2) atom.