MgFe4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), two equivalent O(4), one F(3), and two equivalent F(1) atoms to form distorted MgO3F3 octahedra that share corners with three equivalent Fe(3)O3F2 trigonal bipyramids, edges with two equivalent Mg(1)O3F3 octahedra, edges with two equivalent Fe(2)O4F2 octahedra, and edges with two equivalent Fe(3)O3F2 trigonal bipyramids. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 5-coordinate geometry to two equivalent O(2), one F(1), one F(2), and two equivalent F(3) atoms. In the second Fe site, Fe(2) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent F(4) atoms to form FeO4F2 octahedra that share corners with two equivalent Fe(3)O3F2 trigonal bipyramids, corners with two equivalent Fe(4)O3F2 trigonal bipyramids, edges with two equivalent Mg(1)O3F3 octahedra, edges with two equivalent Fe(2)O4F2 octahedra, and edges with two equivalent Fe(3)O3F2 trigonal bipyramids. In the third Fe site, Fe(3) is bonded to one O(1), two equivalent O(4), one F(1), and one F(4) atom to form distorted FeO3F2 trigonal bipyramids that share corners with two equivalent Fe(2)O4F2 octahedra, corners with three equivalent Mg(1)O3F3 octahedra, corners with two equivalent Fe(3)O3F2 trigonal bipyramids, edges with two equivalent Mg(1)O3F3 octahedra, and edges with two equivalent Fe(2)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 15-76°. In the fourth Fe site, Fe(4) is bonded to one O(2), two equivalent O(3), and two equivalent F(2) atoms to form distorted FeO3F2 trigonal bipyramids that share corners with two equivalent Fe(2)O4F2 octahedra and edges with two equivalent Fe(4)O3F2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 51-52°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(3), and two equivalent Fe(2) atoms to form distorted OMgFe3 trigonal pyramids that share corners with two equivalent O(4)Mg2Fe3 square pyramids, corners with two equivalent O(1)MgFe3 trigonal pyramids, and edges with two equivalent O(4)Mg2Fe3 square pyramids. 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(2) and two equivalent Fe(4) atoms. 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 OMg2Fe3 square pyramids that share corners with two equivalent O(1)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 square pyramids, and edges with two equivalent O(1)MgFe3 trigonal pyramids. There are four inequivalent F sites. In the first F site, F(1) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Fe(1), and one Fe(3) atom. In the second F site, F(2) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(1) atoms. In the fourth F site, F(4) is bonded in a distorted T-shaped geometry to one Fe(3) and two equivalent Fe(2) atoms.
MgFe4(OF)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), two equivalent O(4), one F(3), and two equivalent F(1) atoms to form distorted MgO3F3 octahedra that share corners with three equivalent Fe(3)O3F2 trigonal bipyramids, edges with two equivalent Mg(1)O3F3 octahedra, edges with two equivalent Fe(2)O4F2 octahedra, and edges with two equivalent Fe(3)O3F2 trigonal bipyramids. The Mg(1)-O(1) bond length is 2.09 Å. There is one shorter (2.07 Å) and one longer (2.25 Å) Mg(1)-O(4) bond length. The Mg(1)-F(3) bond length is 1.94 Å. There is one shorter (2.01 Å) and one longer (2.05 Å) Mg(1)-F(1) bond length. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 5-coordinate geometry to two equivalent O(2), one F(1), one F(2), and two equivalent F(3) atoms. There is one shorter (1.99 Å) and one longer (2.01 Å) Fe(1)-O(2) bond length. The Fe(1)-F(1) bond length is 2.64 Å. The Fe(1)-F(2) bond length is 2.18 Å. There is one shorter (2.12 Å) and one longer (2.19 Å) Fe(1)-F(3) bond length. In the second Fe site, Fe(2) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent F(4) atoms to form FeO4F2 octahedra that share corners with two equivalent Fe(3)O3F2 trigonal bipyramids, corners with two equivalent Fe(4)O3F2 trigonal bipyramids, edges with two equivalent Mg(1)O3F3 octahedra, edges with two equivalent Fe(2)O4F2 octahedra, and edges with two equivalent Fe(3)O3F2 trigonal bipyramids. The Fe(2)-O(3) bond length is 1.91 Å. The Fe(2)-O(4) bond length is 2.12 Å. There is one shorter (2.00 Å) and one longer (2.04 Å) Fe(2)-O(1) bond length. There is one shorter (2.08 Å) and one longer (2.09 Å) Fe(2)-F(4) bond length. In the third Fe site, Fe(3) is bonded to one O(1), two equivalent O(4), one F(1), and one F(4) atom to form distorted FeO3F2 trigonal bipyramids that share corners with two equivalent Fe(2)O4F2 octahedra, corners with three equivalent Mg(1)O3F3 octahedra, corners with two equivalent Fe(3)O3F2 trigonal bipyramids, edges with two equivalent Mg(1)O3F3 octahedra, and edges with two equivalent Fe(2)O4F2 octahedra. The corner-sharing octahedral tilt angles range from 15-76°. The Fe(3)-O(1) bond length is 1.98 Å. There is one shorter (1.98 Å) and one longer (2.21 Å) Fe(3)-O(4) bond length. The Fe(3)-F(1) bond length is 2.31 Å. The Fe(3)-F(4) bond length is 2.26 Å. In the fourth Fe site, Fe(4) is bonded to one O(2), two equivalent O(3), and two equivalent F(2) atoms to form distorted FeO3F2 trigonal bipyramids that share corners with two equivalent Fe(2)O4F2 octahedra and edges with two equivalent Fe(4)O3F2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 51-52°. The Fe(4)-O(2) bond length is 1.83 Å. There is one shorter (1.96 Å) and one longer (1.98 Å) Fe(4)-O(3) bond length. There is one shorter (2.04 Å) and one longer (2.23 Å) Fe(4)-F(2) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(3), and two equivalent Fe(2) atoms to form distorted OMgFe3 trigonal pyramids that share corners with two equivalent O(4)Mg2Fe3 square pyramids, corners with two equivalent O(1)MgFe3 trigonal pyramids, and edges with two equivalent O(4)Mg2Fe3 square pyramids. 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(2) and two equivalent Fe(4) atoms. 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 OMg2Fe3 square pyramids that share corners with two equivalent O(1)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 square pyramids, and edges with two equivalent O(1)MgFe3 trigonal pyramids. There are four inequivalent F sites. In the first F site, F(1) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Fe(1), and one Fe(3) atom. In the second F site, F(2) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(1) atoms. In the fourth F site, F(4) is bonded in a distorted T-shaped geometry to one Fe(3) and two equivalent Fe(2) atoms.