MgFe6(O5F)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(6), two equivalent O(3), and one F(2) atom to form distorted MgO3F tetrahedra that share  a cornercorner with one Fe(3)O4F2 octahedra,  a cornercorner with one Fe(2)O5F octahedra, corners with two equivalent Fe(1)O5F octahedra, and  an edgeedge with one Fe(1)O5F octahedra. The corner-sharing octahedral tilt angles range from 6-64°. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(6), two equivalent O(3), and one F(2) atom to form distorted FeO5F octahedra that share corners with two equivalent Mg(1)O3F tetrahedra,  an edgeedge with one Fe(3)O4F2 octahedra,  an edgeedge with one Fe(2)O5F octahedra, and  an edgeedge with one Mg(1)O3F tetrahedra. In the second Fe site, Fe(2) is bonded to one O(1), one O(6), one O(7), two equivalent O(4), and one F(1) atom to form FeO5F octahedra that share  a cornercorner with one Mg(1)O3F tetrahedra,  an edgeedge with one Fe(3)O4F2 octahedra, and  an edgeedge with one Fe(1)O5F octahedra. In the third Fe site, Fe(3) is bonded to one O(2), one O(7), two equivalent O(5), one F(1), and one F(2) atom to form FeO4F2 octahedra that share  a cornercorner with one Mg(1)O3F tetrahedra,  an edgeedge with one Fe(1)O5F octahedra, and  an edgeedge with one Fe(2)O5F octahedra. In the fourth Fe site, Fe(4) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(3), and two equivalent O(4) atoms. In the fifth Fe site, Fe(5) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(3), and two equivalent O(5) atoms. In the sixth Fe site, Fe(6) is bonded in a 5-coordinate geometry to one O(7), two equivalent O(4), and two equivalent O(5) atoms. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Fe(1), one Fe(2), and one Fe(4) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(1), one Fe(3), and one Fe(5) atom. In the third O site, O(3) is bonded to one Mg(1), one Fe(1), one Fe(4), and one Fe(5) atom to form a mixture of distorted corner and face-sharing OMgFe3 trigonal pyramids. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(2), one Fe(4), and one Fe(6) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(3), one Fe(5), and one Fe(6) atom. In the sixth O site, O(6) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Fe(2), one Fe(3), and one Fe(6) atom. There are two inequivalent F sites. In the first F site, F(1) is bonded in an L-shaped geometry to one Fe(2) and one Fe(3) atom. In the second F site, F(2) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one Fe(3) atom.
MgFe6(O5F)2 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(6), two equivalent O(3), and one F(2) atom to form distorted MgO3F tetrahedra that share  a cornercorner with one Fe(3)O4F2 octahedra,  a cornercorner with one Fe(2)O5F octahedra, corners with two equivalent Fe(1)O5F octahedra, and  an edgeedge with one Fe(1)O5F octahedra. The corner-sharing octahedral tilt angles range from 6-64°. The Mg(1)-O(6) bond length is 1.90 Å. Both Mg(1)-O(3) bond lengths are 1.99 Å. The Mg(1)-F(2) bond length is 1.89 Å. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(6), two equivalent O(3), and one F(2) atom to form distorted FeO5F octahedra that share corners with two equivalent Mg(1)O3F tetrahedra,  an edgeedge with one Fe(3)O4F2 octahedra,  an edgeedge with one Fe(2)O5F octahedra, and  an edgeedge with one Mg(1)O3F tetrahedra. The Fe(1)-O(1) bond length is 1.91 Å. The Fe(1)-O(2) bond length is 1.93 Å. The Fe(1)-O(6) bond length is 1.94 Å. Both Fe(1)-O(3) bond lengths are 2.02 Å. The Fe(1)-F(2) bond length is 2.30 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(6), one O(7), two equivalent O(4), and one F(1) atom to form FeO5F octahedra that share  a cornercorner with one Mg(1)O3F tetrahedra,  an edgeedge with one Fe(3)O4F2 octahedra, and  an edgeedge with one Fe(1)O5F octahedra. The Fe(2)-O(1) bond length is 2.08 Å. The Fe(2)-O(6) bond length is 1.92 Å. The Fe(2)-O(7) bond length is 2.01 Å. Both Fe(2)-O(4) bond lengths are 1.96 Å. The Fe(2)-F(1) bond length is 2.04 Å. In the third Fe site, Fe(3) is bonded to one O(2), one O(7), two equivalent O(5), one F(1), and one F(2) atom to form FeO4F2 octahedra that share  a cornercorner with one Mg(1)O3F tetrahedra,  an edgeedge with one Fe(1)O5F octahedra, and  an edgeedge with one Fe(2)O5F octahedra. The Fe(3)-O(2) bond length is 2.05 Å. The Fe(3)-O(7) bond length is 1.98 Å. Both Fe(3)-O(5) bond lengths are 1.95 Å. The Fe(3)-F(1) bond length is 1.96 Å. The Fe(3)-F(2) bond length is 2.04 Å. In the fourth Fe site, Fe(4) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(3), and two equivalent O(4) atoms. The Fe(4)-O(1) bond length is 1.87 Å. Both Fe(4)-O(3) bond lengths are 2.16 Å. Both Fe(4)-O(4) bond lengths are 1.95 Å. In the fifth Fe site, Fe(5) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(3), and two equivalent O(5) atoms. The Fe(5)-O(2) bond length is 1.92 Å. Both Fe(5)-O(3) bond lengths are 2.11 Å. Both Fe(5)-O(5) bond lengths are 1.94 Å. In the sixth Fe site, Fe(6) is bonded in a 5-coordinate geometry to one O(7), two equivalent O(4), and two equivalent O(5) atoms. The Fe(6)-O(7) bond length is 1.98 Å. Both Fe(6)-O(4) bond lengths are 1.98 Å. Both Fe(6)-O(5) bond lengths are 2.01 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Fe(1), one Fe(2), and one Fe(4) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(1), one Fe(3), and one Fe(5) atom. In the third O site, O(3) is bonded to one Mg(1), one Fe(1), one Fe(4), and one Fe(5) atom to form a mixture of distorted corner and face-sharing OMgFe3 trigonal pyramids. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(2), one Fe(4), and one Fe(6) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(3), one Fe(5), and one Fe(6) atom. In the sixth O site, O(6) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Fe(2), one Fe(3), and one Fe(6) atom. There are two inequivalent F sites. In the first F site, F(1) is bonded in an L-shaped geometry to one Fe(2) and one Fe(3) atom. In the second F site, F(2) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one Fe(3) atom.