MgFe4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to two equivalent O(3), two equivalent O(4), one F(1), and one F(4) atom to form distorted MgO4F2 octahedra that share corners with two equivalent Fe(3)O4F2 octahedra, corners with two equivalent Fe(4)O3F2 trigonal bipyramids, edges with two equivalent Mg(1)O4F2 octahedra, edges with four equivalent Fe(2)O2F4 octahedra,  an edgeedge with one Fe(4)O3F2 trigonal bipyramid, and  a faceface with one Fe(3)O4F2 octahedra. The corner-sharing octahedral tilt angles are 38°. 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)O4F2 octahedra, corners with four equivalent Fe(4)O3F2 trigonal bipyramids, and edges with two equivalent Fe(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 45-51°. 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 corners with four equivalent Fe(3)O4F2 octahedra, corners with two equivalent Fe(4)O3F2 trigonal bipyramids, edges with two equivalent Fe(2)O2F4 octahedra, and edges with four equivalent Mg(1)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 44-56°. In the third Fe site, Fe(3) is bonded to two equivalent O(2), two equivalent O(4), one F(1), and one F(3) atom to form distorted FeO4F2 octahedra that share corners with two equivalent Mg(1)O4F2 octahedra, corners with four equivalent Fe(2)O2F4 octahedra, corners with four equivalent Fe(1)O3F3 octahedra, edges with two equivalent Fe(3)O4F2 octahedra, and  a faceface with one Mg(1)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 38-56°. In the fourth Fe site, Fe(4) is bonded to one O(1), two equivalent O(3), and two equivalent F(2) atoms to form distorted FeO3F2 trigonal bipyramids that share corners with two equivalent Mg(1)O4F2 octahedra, corners with two equivalent Fe(2)O2F4 octahedra, corners with four equivalent Fe(1)O3F3 octahedra,  an edgeedge with one Mg(1)O4F2 octahedra, and edges with two equivalent Fe(4)O3F2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 26-68°. 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 to two equivalent Mg(1), one Fe(2), and two equivalent Fe(4) atoms to form a mixture of distorted corner and edge-sharing OMg2Fe3 trigonal bipyramids. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Fe(2), and two equivalent Fe(3) atoms to form a mixture of distorted corner and edge-sharing OMg2Fe3 trigonal bipyramids. There are four inequivalent F sites. In the first F site, F(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(3), and two equivalent Fe(2) atoms. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Fe(1) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a distorted T-shaped geometry to one Fe(3) and two equivalent Fe(1) atoms. In the fourth F site, F(4) is bonded in a distorted T-shaped geometry to one Mg(1) and two equivalent Fe(2) atoms.
MgFe4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to two equivalent O(3), two equivalent O(4), one F(1), and one F(4) atom to form distorted MgO4F2 octahedra that share corners with two equivalent Fe(3)O4F2 octahedra, corners with two equivalent Fe(4)O3F2 trigonal bipyramids, edges with two equivalent Mg(1)O4F2 octahedra, edges with four equivalent Fe(2)O2F4 octahedra,  an edgeedge with one Fe(4)O3F2 trigonal bipyramid, and  a faceface with one Fe(3)O4F2 octahedra. The corner-sharing octahedral tilt angles are 38°. Both Mg(1)-O(3) bond lengths are 2.06 Å. There is one shorter (2.23 Å) and one longer (2.25 Å) Mg(1)-O(4) bond length. The Mg(1)-F(1) bond length is 2.01 Å. The Mg(1)-F(4) bond length is 1.93 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)O4F2 octahedra, corners with four equivalent Fe(4)O3F2 trigonal bipyramids, and edges with two equivalent Fe(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 45-51°. The Fe(1)-O(2) bond length is 1.99 Å. Both Fe(1)-O(1) bond lengths are 1.91 Å. The Fe(1)-F(2) bond length is 2.06 Å. Both Fe(1)-F(3) bond lengths are 2.21 Å. 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 corners with four equivalent Fe(3)O4F2 octahedra, corners with two equivalent Fe(4)O3F2 trigonal bipyramids, edges with two equivalent Fe(2)O2F4 octahedra, and edges with four equivalent Mg(1)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 44-56°. The Fe(2)-O(3) bond length is 2.07 Å. The Fe(2)-O(4) bond length is 2.08 Å. There is one shorter (2.16 Å) and one longer (2.17 Å) Fe(2)-F(1) bond length. Both Fe(2)-F(4) bond lengths are 2.13 Å. In the third Fe site, Fe(3) is bonded to two equivalent O(2), two equivalent O(4), one F(1), and one F(3) atom to form distorted FeO4F2 octahedra that share corners with two equivalent Mg(1)O4F2 octahedra, corners with four equivalent Fe(2)O2F4 octahedra, corners with four equivalent Fe(1)O3F3 octahedra, edges with two equivalent Fe(3)O4F2 octahedra, and  a faceface with one Mg(1)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 38-56°. Both Fe(3)-O(2) bond lengths are 1.94 Å. There is one shorter (2.12 Å) and one longer (2.14 Å) Fe(3)-O(4) bond length. The Fe(3)-F(1) bond length is 2.32 Å. The Fe(3)-F(3) bond length is 2.07 Å. In the fourth Fe site, Fe(4) is bonded to one O(1), two equivalent O(3), and two equivalent F(2) atoms to form distorted FeO3F2 trigonal bipyramids that share corners with two equivalent Mg(1)O4F2 octahedra, corners with two equivalent Fe(2)O2F4 octahedra, corners with four equivalent Fe(1)O3F3 octahedra,  an edgeedge with one Mg(1)O4F2 octahedra, and edges with two equivalent Fe(4)O3F2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 26-68°. The Fe(4)-O(1) bond length is 1.99 Å. Both Fe(4)-O(3) bond lengths are 2.20 Å. Both Fe(4)-F(2) bond lengths are 2.16 Å. 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 to two equivalent Mg(1), one Fe(2), and two equivalent Fe(4) atoms to form a mixture of distorted corner and edge-sharing OMg2Fe3 trigonal bipyramids. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Fe(2), and two equivalent Fe(3) atoms to form a mixture of distorted corner and edge-sharing OMg2Fe3 trigonal bipyramids. There are four inequivalent F sites. In the first F site, F(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(3), and two equivalent Fe(2) atoms. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Fe(1) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a distorted T-shaped geometry to one Fe(3) and two equivalent Fe(1) atoms. In the fourth F site, F(4) is bonded in a distorted T-shaped geometry to one Mg(1) and two equivalent Fe(2) atoms.