MgFe(CoO3)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(6), and two equivalent O(5) atoms to form distorted MgO4 trigonal pyramids that share corners with three equivalent Fe(1)O6 octahedra, corners with four equivalent Co(1)O6 octahedra, and corners with two equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 49-59°. Fe(1) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with three equivalent Mg(1)O4 trigonal pyramids, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Co(1)O6 octahedra. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(6) atoms to form CoO6 octahedra that share corners with four equivalent Mg(1)O4 trigonal pyramids, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Co(1)O6 octahedra. In the second Co site, Co(2) is bonded in a 6-coordinate geometry to one O(2), one O(6), two equivalent O(3), and two equivalent O(5) atoms. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(1), and two equivalent Co(1) atoms to form distorted OMgFeCo2 trigonal pyramids that share corners with two equivalent O(1)MgFeCo2 trigonal pyramids, corners with three equivalent O(6)MgCo3 trigonal pyramids, and  an edgeedge with one O(6)MgCo3 trigonal pyramid. In the second O site, O(2) is bonded in a trigonal non-coplanar geometry to two equivalent Fe(1) and one Co(2) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Co(1) and two equivalent Co(2) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Fe(1) and one Co(1) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Fe(1), and two equivalent Co(2) atoms. In the sixth O site, O(6) is bonded to one Mg(1), one Co(2), and two equivalent Co(1) atoms to form OMgCo3 trigonal pyramids that share corners with two equivalent O(6)MgCo3 trigonal pyramids, corners with three equivalent O(1)MgFeCo2 trigonal pyramids, and  an edgeedge with one O(1)MgFeCo2 trigonal pyramid.
MgFe(CoO3)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(6), and two equivalent O(5) atoms to form distorted MgO4 trigonal pyramids that share corners with three equivalent Fe(1)O6 octahedra, corners with four equivalent Co(1)O6 octahedra, and corners with two equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 49-59°. The Mg(1)-O(1) bond length is 1.94 Å. The Mg(1)-O(6) bond length is 2.06 Å. Both Mg(1)-O(5) bond lengths are 2.00 Å. Fe(1) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with three equivalent Mg(1)O4 trigonal pyramids, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Co(1)O6 octahedra. The Fe(1)-O(1) bond length is 2.02 Å. The Fe(1)-O(5) bond length is 1.97 Å. Both Fe(1)-O(2) bond lengths are 2.05 Å. Both Fe(1)-O(4) bond lengths are 2.09 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(6) atoms to form CoO6 octahedra that share corners with four equivalent Mg(1)O4 trigonal pyramids, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Co(1)O6 octahedra. The Co(1)-O(3) bond length is 1.85 Å. The Co(1)-O(4) bond length is 1.78 Å. There is one shorter (2.06 Å) and one longer (2.07 Å) Co(1)-O(1) bond length. Both Co(1)-O(6) bond lengths are 2.05 Å. In the second Co site, Co(2) is bonded in a 6-coordinate geometry to one O(2), one O(6), two equivalent O(3), and two equivalent O(5) atoms. The Co(2)-O(2) bond length is 1.82 Å. The Co(2)-O(6) bond length is 1.98 Å. Both Co(2)-O(3) bond lengths are 1.97 Å. There is one shorter (2.41 Å) and one longer (2.42 Å) Co(2)-O(5) bond length. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(1), and two equivalent Co(1) atoms to form distorted OMgFeCo2 trigonal pyramids that share corners with two equivalent O(1)MgFeCo2 trigonal pyramids, corners with three equivalent O(6)MgCo3 trigonal pyramids, and  an edgeedge with one O(6)MgCo3 trigonal pyramid. In the second O site, O(2) is bonded in a trigonal non-coplanar geometry to two equivalent Fe(1) and one Co(2) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Co(1) and two equivalent Co(2) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Fe(1) and one Co(1) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Fe(1), and two equivalent Co(2) atoms. In the sixth O site, O(6) is bonded to one Mg(1), one Co(2), and two equivalent Co(1) atoms to form OMgCo3 trigonal pyramids that share corners with two equivalent O(6)MgCo3 trigonal pyramids, corners with three equivalent O(1)MgFeCo2 trigonal pyramids, and  an edgeedge with one O(1)MgFeCo2 trigonal pyramid.