MgFe8(OF)8 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), two equivalent O(4), one F(4), and two equivalent F(1) atoms to form MgO3F3 octahedra that share edges with two equivalent Mg(1)O3F3 octahedra and edges with two equivalent Fe(2)O6 octahedra. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(2), one F(7), and two equivalent F(8) atoms to form a mixture of edge and corner-sharing FeO3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-51°. 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(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, edges with two equivalent Mg(1)O3F3 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-54°. In the third Fe site, Fe(3) is bonded in a 6-coordinate geometry to one O(1), two equivalent O(3), one F(3), and two equivalent F(1) atoms. In the fourth Fe site, Fe(4) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(4), and two equivalent F(2) atoms. In the fifth Fe site, Fe(5) is bonded in a 6-coordinate geometry to one O(6), two equivalent O(5), one F(1), and two equivalent F(4) atoms. 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 FeF6 octahedra that share corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, and edges with two equivalent Fe(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 44-48°. In the seventh Fe site, Fe(7) is bonded to one O(5), two equivalent O(7), one F(8), and two equivalent F(6) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(7)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 44-54°. In the eighth Fe site, Fe(8) is bonded to one O(8), two equivalent O(6), one F(5), and two equivalent F(7) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(8)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-52°. There are eight inequivalent O sites. In the first O site, O(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 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 to two equivalent Mg(1), one Fe(2), and two equivalent Fe(4) atoms to form distorted edge-sharing OMg2Fe3 trigonal bipyramids. 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 planar geometry to one Fe(2) and two equivalent Fe(7) atoms. In the eighth O site, O(8) is bonded in a trigonal planar geometry to 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 5-coordinate geometry to two equivalent Mg(1), 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 T-shaped geometry to one Fe(3) and two equivalent Fe(6) atoms. In the fourth F site, F(4) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(5) atoms. In the fifth F site, F(5) is bonded in a distorted T-shaped geometry to one Fe(8) and two equivalent Fe(6) atoms. In the sixth F site, F(6) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(7) atoms. In the seventh F site, F(7) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(8) atoms. In the eighth F site, F(8) is bonded in a distorted T-shaped geometry to one Fe(7) and two equivalent Fe(1) atoms.
MgFe8(OF)8 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), two equivalent O(4), one F(4), and two equivalent F(1) atoms to form MgO3F3 octahedra that share edges with two equivalent Mg(1)O3F3 octahedra and edges with two equivalent Fe(2)O6 octahedra. The Mg(1)-O(1) bond length is 1.96 Å. There is one shorter (2.03 Å) and one longer (2.05 Å) Mg(1)-O(4) bond length. The Mg(1)-F(4) bond length is 1.95 Å. There is one shorter (2.12 Å) and one longer (2.17 Å) Mg(1)-F(1) bond length. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(2), one F(7), and two equivalent F(8) atoms to form a mixture of edge and corner-sharing FeO3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-51°. The Fe(1)-O(3) bond length is 1.95 Å. Both Fe(1)-O(2) bond lengths are 1.90 Å. The Fe(1)-F(7) bond length is 2.10 Å. There is one shorter (2.13 Å) and one longer (2.17 Å) Fe(1)-F(8) bond length. 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(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, edges with two equivalent Mg(1)O3F3 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-54°. The Fe(2)-O(4) bond length is 2.26 Å. The Fe(2)-O(7) bond length is 2.02 Å. There is one shorter (2.13 Å) and one longer (2.15 Å) Fe(2)-O(1) bond length. There is one shorter (1.99 Å) and one longer (2.00 Å) Fe(2)-O(8) bond length. In the third Fe site, Fe(3) is bonded in a 6-coordinate geometry to one O(1), two equivalent O(3), one F(3), and two equivalent F(1) atoms. The Fe(3)-O(1) bond length is 1.92 Å. There is one shorter (1.88 Å) and one longer (1.90 Å) Fe(3)-O(3) bond length. The Fe(3)-F(3) bond length is 2.04 Å. There is one shorter (2.45 Å) and one longer (2.62 Å) Fe(3)-F(1) bond length. In the fourth Fe site, Fe(4) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(4), and two equivalent F(2) atoms. The Fe(4)-O(2) bond length is 1.96 Å. There is one shorter (2.15 Å) and one longer (2.20 Å) Fe(4)-O(4) bond length. There is one shorter (2.15 Å) and one longer (2.19 Å) Fe(4)-F(2) bond length. In the fifth Fe site, Fe(5) is bonded in a 6-coordinate geometry to one O(6), two equivalent O(5), one F(1), and two equivalent F(4) atoms. The Fe(5)-O(6) bond length is 1.87 Å. Both Fe(5)-O(5) bond lengths are 1.91 Å. The Fe(5)-F(1) bond length is 2.50 Å. Both Fe(5)-F(4) bond lengths are 2.16 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 FeF6 octahedra that share corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, and edges with two equivalent Fe(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 44-48°. The Fe(6)-F(2) bond length is 2.06 Å. The Fe(6)-F(6) bond length is 2.09 Å. Both Fe(6)-F(3) bond lengths are 2.21 Å. There is one shorter (2.11 Å) and one longer (2.12 Å) Fe(6)-F(5) bond length. In the seventh Fe site, Fe(7) is bonded to one O(5), two equivalent O(7), one F(8), and two equivalent F(6) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(7)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 44-54°. The Fe(7)-O(5) bond length is 1.95 Å. Both Fe(7)-O(7) bond lengths are 1.93 Å. The Fe(7)-F(8) bond length is 2.06 Å. There is one shorter (2.17 Å) and one longer (2.22 Å) Fe(7)-F(6) bond length. In the eighth Fe site, Fe(8) is bonded to one O(8), two equivalent O(6), one F(5), and two equivalent F(7) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(8)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-52°. The Fe(8)-O(8) bond length is 1.93 Å. There is one shorter (1.95 Å) and one longer (1.96 Å) Fe(8)-O(6) bond length. The Fe(8)-F(5) bond length is 2.23 Å. There is one shorter (2.10 Å) and one longer (2.11 Å) Fe(8)-F(7) bond length. There are eight inequivalent O sites. In the first O site, O(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 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 to two equivalent Mg(1), one Fe(2), and two equivalent Fe(4) atoms to form distorted edge-sharing OMg2Fe3 trigonal bipyramids. 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 planar geometry to one Fe(2) and two equivalent Fe(7) atoms. In the eighth O site, O(8) is bonded in a trigonal planar geometry to 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 5-coordinate geometry to two equivalent Mg(1), 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 T-shaped geometry to one Fe(3) and two equivalent Fe(6) atoms. In the fourth F site, F(4) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(5) atoms. In the fifth F site, F(5) is bonded in a distorted T-shaped geometry to one Fe(8) and two equivalent Fe(6) atoms. In the sixth F site, F(6) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(7) atoms. In the seventh F site, F(7) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(8) atoms. In the eighth F site, F(8) is bonded in a distorted T-shaped geometry to one Fe(7) and two equivalent Fe(1) atoms.