MgFe2(OF)2 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to two equivalent O(2), one F(1), and one F(2) atom to form MgO2F2 tetrahedra that share corners with two equivalent Mg(1)O2F2 tetrahedra and corners with four equivalent Fe(1)O2F2 tetrahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), and two equivalent F(2) atoms to form FeO2F2 tetrahedra that share corners with two equivalent Fe(1)O2F2 tetrahedra and corners with four equivalent Mg(1)O2F2 tetrahedra. In the second Fe site, Fe(2) is bonded in a 3-coordinate geometry to two equivalent O(1), two equivalent O(2), and one F(1) atom. There are two inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to one Fe(1) and two equivalent Fe(2) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1), one Fe(1), and two equivalent Fe(2) atoms to form distorted edge-sharing OMg2Fe3 square pyramids. There are two inequivalent F sites. In the first F site, F(1) is bonded in a bent 120 degrees geometry to one Mg(1) and one Fe(2) atom. In the second F site, F(2) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(1) atoms.
MgFe2(OF)2 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to two equivalent O(2), one F(1), and one F(2) atom to form MgO2F2 tetrahedra that share corners with two equivalent Mg(1)O2F2 tetrahedra and corners with four equivalent Fe(1)O2F2 tetrahedra. Both Mg(1)-O(2) bond lengths are 1.99 Å. The Mg(1)-F(1) bond length is 1.90 Å. The Mg(1)-F(2) bond length is 1.99 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), and two equivalent F(2) atoms to form FeO2F2 tetrahedra that share corners with two equivalent Fe(1)O2F2 tetrahedra and corners with four equivalent Mg(1)O2F2 tetrahedra. The Fe(1)-O(1) bond length is 1.88 Å. The Fe(1)-O(2) bond length is 2.10 Å. Both Fe(1)-F(2) bond lengths are 2.13 Å. In the second Fe site, Fe(2) is bonded in a 3-coordinate geometry to two equivalent O(1), two equivalent O(2), and one F(1) atom. Both Fe(2)-O(1) bond lengths are 1.97 Å. Both Fe(2)-O(2) bond lengths are 2.45 Å. The Fe(2)-F(1) bond length is 2.06 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to one Fe(1) and two equivalent Fe(2) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1), one Fe(1), and two equivalent Fe(2) atoms to form distorted edge-sharing OMg2Fe3 square pyramids. There are two inequivalent F sites. In the first F site, F(1) is bonded in a bent 120 degrees geometry to one Mg(1) and one Fe(2) atom. In the second F site, F(2) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1) and two equivalent Fe(1) atoms.