MgFe4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(4), one F(1), and one F(4) atom. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), two equivalent O(1), one F(2), and two equivalent F(3) atoms to form FeO3F3 octahedra that share corners with four equivalent Fe(3)O3F tetrahedra and edges with two equivalent Fe(1)O3F3 octahedra. In the second Fe site, Fe(2) is bonded to one O(3), one O(4), two equivalent F(1), and two equivalent F(4) atoms to form FeO2F4 octahedra that share  a cornercorner with one Fe(3)O3F tetrahedra and edges with two equivalent Fe(2)O2F4 octahedra. In the third Fe site, Fe(3) is bonded to one O(4), two equivalent O(2), and one F(3) atom to form FeO3F tetrahedra that share  a cornercorner with one Fe(2)O2F4 octahedra, corners with four equivalent Fe(1)O3F3 octahedra, and corners with two equivalent Fe(3)O3F tetrahedra. The corner-sharing octahedral tilt angles range from 47-60°. In the fourth Fe site, Fe(4) is bonded in a 6-coordinate geometry to one O(1), two equivalent O(3), one F(4), and two equivalent F(2) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Fe(2), and two equivalent Fe(4) atoms. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Fe(2), and one Fe(3) atom to form corner-sharing OMg2Fe2 tetrahedra. There are four inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(2) atoms. In the second F site, F(2) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a 3-coordinate geometry to one Fe(3) and two equivalent Fe(1) atoms. In the fourth F site, F(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(4), and two equivalent Fe(2) atoms.
MgFe4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(4), one F(1), and one F(4) atom. There is one shorter (2.28 Å) and one longer (2.51 Å) Mg(1)-O(3) bond length. There is one shorter (2.01 Å) and one longer (2.03 Å) Mg(1)-O(4) bond length. The Mg(1)-F(1) bond length is 1.93 Å. The Mg(1)-F(4) bond length is 2.03 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), two equivalent O(1), one F(2), and two equivalent F(3) atoms to form FeO3F3 octahedra that share corners with four equivalent Fe(3)O3F tetrahedra and edges with two equivalent Fe(1)O3F3 octahedra. The Fe(1)-O(2) bond length is 2.10 Å. Both Fe(1)-O(1) bond lengths are 2.04 Å. The Fe(1)-F(2) bond length is 2.21 Å. There is one shorter (2.29 Å) and one longer (2.31 Å) Fe(1)-F(3) bond length. In the second Fe site, Fe(2) is bonded to one O(3), one O(4), two equivalent F(1), and two equivalent F(4) atoms to form FeO2F4 octahedra that share  a cornercorner with one Fe(3)O3F tetrahedra and edges with two equivalent Fe(2)O2F4 octahedra. The Fe(2)-O(3) bond length is 2.05 Å. The Fe(2)-O(4) bond length is 2.09 Å. There is one shorter (2.15 Å) and one longer (2.16 Å) Fe(2)-F(1) bond length. There is one shorter (2.17 Å) and one longer (2.20 Å) Fe(2)-F(4) bond length. In the third Fe site, Fe(3) is bonded to one O(4), two equivalent O(2), and one F(3) atom to form FeO3F tetrahedra that share  a cornercorner with one Fe(2)O2F4 octahedra, corners with four equivalent Fe(1)O3F3 octahedra, and corners with two equivalent Fe(3)O3F tetrahedra. The corner-sharing octahedral tilt angles range from 47-60°. The Fe(3)-O(4) bond length is 1.90 Å. Both Fe(3)-O(2) bond lengths are 1.88 Å. The Fe(3)-F(3) bond length is 1.94 Å. In the fourth Fe site, Fe(4) is bonded in a 6-coordinate geometry to one O(1), two equivalent O(3), one F(4), and two equivalent F(2) atoms. The Fe(4)-O(1) bond length is 1.82 Å. Both Fe(4)-O(3) bond lengths are 2.09 Å. The Fe(4)-F(4) bond length is 2.38 Å. There is one shorter (2.12 Å) and one longer (2.15 Å) Fe(4)-F(2) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Fe(2), and two equivalent Fe(4) atoms. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Fe(2), and one Fe(3) atom to form corner-sharing OMg2Fe2 tetrahedra. There are four inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(2) atoms. In the second F site, F(2) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a 3-coordinate geometry to one Fe(3) and two equivalent Fe(1) atoms. In the fourth F site, F(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(4), and two equivalent Fe(2) atoms.