MgFe4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(3), two equivalent O(4), one F(2), and two equivalent F(1) atoms to form distorted MgO3F3 octahedra that share corners with two equivalent Fe(1)O4F2 octahedra,  a cornercorner with one Fe(2)O2F2 tetrahedra, edges with two equivalent Mg(1)O3F3 octahedra, edges with four equivalent Fe(3)O3F3 octahedra, and  a faceface with one Fe(1)O4F2 octahedra. The corner-sharing octahedral tilt angles are 35°. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1), two equivalent O(4), one F(2), and one F(3) atom to form distorted FeO4F2 octahedra that share corners with two equivalent Mg(1)O3F3 octahedra, corners with four equivalent Fe(3)O3F3 octahedra, corners with four equivalent Fe(4)O3F3 octahedra, edges with two equivalent Fe(1)O4F2 octahedra, and  a faceface with one Mg(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 35-56°. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), and two equivalent F(4) atoms to form FeO2F2 tetrahedra that share  a cornercorner with one Mg(1)O3F3 octahedra, corners with two equivalent Fe(3)O3F3 octahedra, corners with four equivalent Fe(4)O3F3 octahedra, and corners with two equivalent Fe(2)O2F2 tetrahedra. The corner-sharing octahedral tilt angles range from 46-64°. In the third Fe site, Fe(3) is bonded to one O(4), two equivalent O(3), one F(1), and two equivalent F(2) atoms to form FeO3F3 octahedra that share corners with four equivalent Fe(1)O4F2 octahedra, corners with two equivalent Fe(2)O2F2 tetrahedra, edges with two equivalent Fe(3)O3F3 octahedra, and edges with four equivalent Mg(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 43-56°. In the fourth Fe site, Fe(4) is bonded to one O(1), two equivalent O(2), one F(4), and two equivalent F(3) atoms to form FeO3F3 octahedra that share corners with four equivalent Fe(1)O4F2 octahedra, corners with four equivalent Fe(2)O2F2 tetrahedra, and edges with two equivalent Fe(4)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-51°. 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(2) and two equivalent Fe(4) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(2), and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Fe(3), and two equivalent Fe(1) atoms to form distorted edge-sharing OMg2Fe3 trigonal bipyramids. There are four inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(3) atom. In the second F site, F(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(1), and two equivalent Fe(3) atoms. In the third F site, F(3) is bonded in a distorted T-shaped geometry to one Fe(1) and two equivalent Fe(4) atoms. In the fourth F site, F(4) is bonded in a distorted T-shaped geometry to one Fe(4) and two equivalent Fe(2) atoms.
MgFe4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(3), two equivalent O(4), one F(2), and two equivalent F(1) atoms to form distorted MgO3F3 octahedra that share corners with two equivalent Fe(1)O4F2 octahedra,  a cornercorner with one Fe(2)O2F2 tetrahedra, edges with two equivalent Mg(1)O3F3 octahedra, edges with four equivalent Fe(3)O3F3 octahedra, and  a faceface with one Fe(1)O4F2 octahedra. The corner-sharing octahedral tilt angles are 35°. The Mg(1)-O(3) bond length is 1.97 Å. There is one shorter (2.24 Å) and one longer (2.27 Å) Mg(1)-O(4) bond length. The Mg(1)-F(2) bond length is 2.06 Å. There is one shorter (1.96 Å) and one longer (1.97 Å) Mg(1)-F(1) bond length. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1), two equivalent O(4), one F(2), and one F(3) atom to form distorted FeO4F2 octahedra that share corners with two equivalent Mg(1)O3F3 octahedra, corners with four equivalent Fe(3)O3F3 octahedra, corners with four equivalent Fe(4)O3F3 octahedra, edges with two equivalent Fe(1)O4F2 octahedra, and  a faceface with one Mg(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 35-56°. Both Fe(1)-O(1) bond lengths are 1.97 Å. There is one shorter (2.09 Å) and one longer (2.10 Å) Fe(1)-O(4) bond length. The Fe(1)-F(2) bond length is 2.33 Å. The Fe(1)-F(3) bond length is 2.09 Å. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), and two equivalent F(4) atoms to form FeO2F2 tetrahedra that share  a cornercorner with one Mg(1)O3F3 octahedra, corners with two equivalent Fe(3)O3F3 octahedra, corners with four equivalent Fe(4)O3F3 octahedra, and corners with two equivalent Fe(2)O2F2 tetrahedra. The corner-sharing octahedral tilt angles range from 46-64°. The Fe(2)-O(2) bond length is 1.97 Å. The Fe(2)-O(3) bond length is 1.93 Å. There is one shorter (2.11 Å) and one longer (2.12 Å) Fe(2)-F(4) bond length. In the third Fe site, Fe(3) is bonded to one O(4), two equivalent O(3), one F(1), and two equivalent F(2) atoms to form FeO3F3 octahedra that share corners with four equivalent Fe(1)O4F2 octahedra, corners with two equivalent Fe(2)O2F2 tetrahedra, edges with two equivalent Fe(3)O3F3 octahedra, and edges with four equivalent Mg(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 43-56°. The Fe(3)-O(4) bond length is 2.15 Å. There is one shorter (2.02 Å) and one longer (2.10 Å) Fe(3)-O(3) bond length. The Fe(3)-F(1) bond length is 2.20 Å. There is one shorter (2.13 Å) and one longer (2.22 Å) Fe(3)-F(2) bond length. In the fourth Fe site, Fe(4) is bonded to one O(1), two equivalent O(2), one F(4), and two equivalent F(3) atoms to form FeO3F3 octahedra that share corners with four equivalent Fe(1)O4F2 octahedra, corners with four equivalent Fe(2)O2F2 tetrahedra, and edges with two equivalent Fe(4)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-51°. The Fe(4)-O(1) bond length is 1.96 Å. Both Fe(4)-O(2) bond lengths are 1.92 Å. The Fe(4)-F(4) bond length is 2.11 Å. There is one shorter (2.18 Å) and one longer (2.22 Å) Fe(4)-F(3) 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(2) and two equivalent Fe(4) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(2), and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Fe(3), and two equivalent Fe(1) atoms to form distorted edge-sharing OMg2Fe3 trigonal bipyramids. There are four inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(3) atom. In the second F site, F(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(1), and two equivalent Fe(3) atoms. In the third F site, F(3) is bonded in a distorted T-shaped geometry to one Fe(1) and two equivalent Fe(4) atoms. In the fourth F site, F(4) is bonded in a distorted T-shaped geometry to one Fe(4) and two equivalent Fe(2) atoms.