K2Mg(FeO2)2 crystallizes in the monoclinic Cm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second K site, K(2) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(2) atoms. Mg(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form MgO4 tetrahedra that share corners with two equivalent Mg(1)O4 tetrahedra and edges with two equivalent Fe(2)O4 tetrahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a trigonal planar geometry to one O(4) and two equivalent O(3) atoms. In the second Fe site, Fe(2) is bonded to one O(1), one O(4), and two equivalent O(2) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Fe(2)O4 tetrahedra and edges with two equivalent Mg(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one K(1), two equivalent K(2), two equivalent Mg(1), and one Fe(2) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to one K(1), two equivalent K(2), one Mg(1), and two equivalent Fe(2) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent K(1), one Mg(1), and two equivalent Fe(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent K(1), one Fe(1), and one Fe(2) atom.
K2Mg(FeO2)2 crystallizes in the monoclinic Cm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms. The K(1)-O(1) bond length is 2.83 Å. The K(1)-O(2) bond length is 2.90 Å. Both K(1)-O(3) bond lengths are 2.86 Å. Both K(1)-O(4) bond lengths are 2.52 Å. In the second K site, K(2) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(2) atoms. Both K(2)-O(1) bond lengths are 3.04 Å. Both K(2)-O(2) bond lengths are 2.86 Å. Mg(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form MgO4 tetrahedra that share corners with two equivalent Mg(1)O4 tetrahedra and edges with two equivalent Fe(2)O4 tetrahedra. The Mg(1)-O(2) bond length is 2.01 Å. The Mg(1)-O(3) bond length is 2.01 Å. Both Mg(1)-O(1) bond lengths are 2.00 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a trigonal planar geometry to one O(4) and two equivalent O(3) atoms. The Fe(1)-O(4) bond length is 1.86 Å. Both Fe(1)-O(3) bond lengths are 1.99 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(4), and two equivalent O(2) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Fe(2)O4 tetrahedra and edges with two equivalent Mg(1)O4 tetrahedra. The Fe(2)-O(1) bond length is 2.14 Å. The Fe(2)-O(4) bond length is 1.97 Å. Both Fe(2)-O(2) bond lengths are 2.08 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one K(1), two equivalent K(2), two equivalent Mg(1), and one Fe(2) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to one K(1), two equivalent K(2), one Mg(1), and two equivalent Fe(2) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent K(1), one Mg(1), and two equivalent Fe(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent K(1), one Fe(1), and one Fe(2) atom.