MgFe8(OF)8 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one F(5), one F(8), two equivalent F(6), and two equivalent F(7) atoms to form distorted MgF6 octahedra that share corners with two equivalent Fe(1)O3F2 square pyramids, edges with two equivalent Mg(1)F6 octahedra, and edges with two equivalent Fe(6)F6 octahedra. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(2), and two equivalent F(8) atoms to form distorted FeO3F2 square pyramids that share corners with two equivalent Mg(1)F6 octahedra, corners with two equivalent Fe(3)O3F3 octahedra, corners with two equivalent Fe(4)O3F3 octahedra, and edges with two equivalent Fe(1)O3F2 square pyramids. The corner-sharing octahedral tilt angles range from 52-64°. In the second Fe site, Fe(2) is bonded to one O(4), one O(7), two equivalent O(1), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Fe(3)O3F3 octahedra, corners with two equivalent Fe(4)O3F3 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(7)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 53-55°. In the third Fe site, Fe(3) is bonded to one O(1), two equivalent O(3), one F(3), and two equivalent F(1) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(1)O3F2 square pyramids, and edges with two equivalent Fe(3)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. In the fourth Fe site, Fe(4) is bonded to one O(2), two equivalent O(4), one F(4), and two equivalent F(2) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(1)O3F2 square pyramids, and edges with two equivalent Fe(4)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 45-55°. In the fifth Fe site, Fe(5) is bonded to one O(6), two equivalent O(5), one F(1), and two equivalent F(4) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(3)O3F3 octahedra, corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(7)O4 trigonal pyramids, and edges with two equivalent Fe(5)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 45-49°. In the sixth Fe site, Fe(6) is bonded to one F(2), one F(6), two equivalent F(3), and two equivalent F(5) atoms to form distorted FeF6 octahedra that share corners with two equivalent Fe(3)O3F3 octahedra, corners with two equivalent Fe(4)O3F3 octahedra, edges with two equivalent Mg(1)F6 octahedra, and edges with two equivalent Fe(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 46-51°. In the seventh Fe site, Fe(7) is bonded to one O(5), one O(8), and two equivalent O(7) atoms to form distorted FeO4 trigonal pyramids that share corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(7)O4 trigonal pyramids, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 61°. In the eighth Fe site, Fe(8) is bonded in a 6-coordinate geometry to one O(8), two equivalent O(6), one F(5), and two equivalent F(7) atoms. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Fe(3) and two equivalent Fe(2) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(4) atoms. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(7) and two equivalent Fe(5) atoms. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Fe(5) and two equivalent Fe(8) atoms. In the seventh O site, O(7) is bonded in a trigonal non-coplanar geometry to one Fe(2) and two equivalent Fe(7) atoms. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Fe(7), one Fe(8), and two equivalent Fe(2) atoms. There are eight inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal planar geometry to one Fe(5) and two equivalent Fe(3) atoms. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a distorted trigonal planar geometry to one Fe(3) and two equivalent Fe(6) atoms. In the fourth F site, F(4) is bonded in a distorted T-shaped geometry to one Fe(4) and two equivalent Fe(5) atoms. In the fifth F site, F(5) is bonded to one Mg(1), one Fe(8), and two equivalent Fe(6) atoms to form distorted corner-sharing FMgFe3 trigonal pyramids. In the sixth F site, F(6) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(6) atom. In the seventh F site, F(7) is bonded in a 4-coordinate geometry to two equivalent Mg(1) and two equivalent Fe(8) atoms. In the eighth F site, F(8) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(1) atoms.
MgFe8(OF)8 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one F(5), one F(8), two equivalent F(6), and two equivalent F(7) atoms to form distorted MgF6 octahedra that share corners with two equivalent Fe(1)O3F2 square pyramids, edges with two equivalent Mg(1)F6 octahedra, and edges with two equivalent Fe(6)F6 octahedra. The Mg(1)-F(5) bond length is 2.01 Å. The Mg(1)-F(8) bond length is 1.91 Å. Both Mg(1)-F(6) bond lengths are 1.97 Å. Both Mg(1)-F(7) bond lengths are 2.17 Å. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(2), and two equivalent F(8) atoms to form distorted FeO3F2 square pyramids that share corners with two equivalent Mg(1)F6 octahedra, corners with two equivalent Fe(3)O3F3 octahedra, corners with two equivalent Fe(4)O3F3 octahedra, and edges with two equivalent Fe(1)O3F2 square pyramids. The corner-sharing octahedral tilt angles range from 52-64°. The Fe(1)-O(3) bond length is 1.86 Å. Both Fe(1)-O(2) bond lengths are 1.93 Å. Both Fe(1)-F(8) bond lengths are 2.19 Å. In the second Fe site, Fe(2) is bonded to one O(4), one O(7), two equivalent O(1), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Fe(3)O3F3 octahedra, corners with two equivalent Fe(4)O3F3 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(7)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 53-55°. The Fe(2)-O(4) bond length is 1.96 Å. The Fe(2)-O(7) bond length is 2.06 Å. Both Fe(2)-O(1) bond lengths are 1.99 Å. Both Fe(2)-O(8) bond lengths are 2.21 Å. In the third Fe site, Fe(3) is bonded to one O(1), two equivalent O(3), one F(3), and two equivalent F(1) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(1)O3F2 square pyramids, and edges with two equivalent Fe(3)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. The Fe(3)-O(1) bond length is 1.89 Å. Both Fe(3)-O(3) bond lengths are 1.99 Å. The Fe(3)-F(3) bond length is 2.21 Å. Both Fe(3)-F(1) bond lengths are 2.10 Å. In the fourth Fe site, Fe(4) is bonded to one O(2), two equivalent O(4), one F(4), and two equivalent F(2) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(1)O3F2 square pyramids, and edges with two equivalent Fe(4)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 45-55°. The Fe(4)-O(2) bond length is 1.99 Å. Both Fe(4)-O(4) bond lengths are 1.94 Å. The Fe(4)-F(4) bond length is 1.99 Å. Both Fe(4)-F(2) bond lengths are 2.21 Å. In the fifth Fe site, Fe(5) is bonded to one O(6), two equivalent O(5), one F(1), and two equivalent F(4) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(3)O3F3 octahedra, corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(7)O4 trigonal pyramids, and edges with two equivalent Fe(5)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 45-49°. The Fe(5)-O(6) bond length is 2.11 Å. Both Fe(5)-O(5) bond lengths are 2.03 Å. The Fe(5)-F(1) bond length is 2.22 Å. Both Fe(5)-F(4) bond lengths are 2.22 Å. In the sixth Fe site, Fe(6) is bonded to one F(2), one F(6), two equivalent F(3), and two equivalent F(5) atoms to form distorted FeF6 octahedra that share corners with two equivalent Fe(3)O3F3 octahedra, corners with two equivalent Fe(4)O3F3 octahedra, edges with two equivalent Mg(1)F6 octahedra, and edges with two equivalent Fe(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 46-51°. The Fe(6)-F(2) bond length is 2.07 Å. The Fe(6)-F(6) bond length is 2.24 Å. Both Fe(6)-F(3) bond lengths are 2.05 Å. Both Fe(6)-F(5) bond lengths are 2.16 Å. In the seventh Fe site, Fe(7) is bonded to one O(5), one O(8), and two equivalent O(7) atoms to form distorted FeO4 trigonal pyramids that share corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(7)O4 trigonal pyramids, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 61°. The Fe(7)-O(5) bond length is 1.82 Å. The Fe(7)-O(8) bond length is 2.07 Å. Both Fe(7)-O(7) bond lengths are 1.88 Å. In the eighth Fe site, Fe(8) is bonded in a 6-coordinate geometry to one O(8), two equivalent O(6), one F(5), and two equivalent F(7) atoms. The Fe(8)-O(8) bond length is 1.90 Å. Both Fe(8)-O(6) bond lengths are 1.88 Å. The Fe(8)-F(5) bond length is 2.38 Å. Both Fe(8)-F(7) bond lengths are 2.53 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Fe(3) and two equivalent Fe(2) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(4) atoms. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(7) and two equivalent Fe(5) atoms. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Fe(5) and two equivalent Fe(8) atoms. In the seventh O site, O(7) is bonded in a trigonal non-coplanar geometry to one Fe(2) and two equivalent Fe(7) atoms. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Fe(7), one Fe(8), and two equivalent Fe(2) atoms. There are eight inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal planar geometry to one Fe(5) and two equivalent Fe(3) atoms. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a distorted trigonal planar geometry to one Fe(3) and two equivalent Fe(6) atoms. In the fourth F site, F(4) is bonded in a distorted T-shaped geometry to one Fe(4) and two equivalent Fe(5) atoms. In the fifth F site, F(5) is bonded to one Mg(1), one Fe(8), and two equivalent Fe(6) atoms to form distorted corner-sharing FMgFe3 trigonal pyramids. In the sixth F site, F(6) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(6) atom. In the seventh F site, F(7) is bonded in a 4-coordinate geometry to two equivalent Mg(1) and two equivalent Fe(8) atoms. In the eighth F site, F(8) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(1) atoms.