Mg(CoO2)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with two equivalent Co(3)O6 octahedra, corners with two equivalent Co(2)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and  a faceface with one Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-47°. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form CoO6 octahedra that share corners with two equivalent Co(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, and edges with two equivalent Co(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-55°. In the second Co site, Co(2) is bonded to one O(3), one O(8), and two equivalent O(6) atoms to form CoO4 tetrahedra that share  a cornercorner with one Co(4)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Co(2)O4 tetrahedra, and edges with two equivalent Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-62°. In the third Co site, Co(3) is bonded to one O(1), one O(6), two equivalent O(2), and two equivalent O(8) atoms to form distorted CoO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Co(1)O6 octahedra, corners with two equivalent Co(4)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, edges with two equivalent Co(2)O4 tetrahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-57°. In the fourth Co site, Co(4) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(7) atoms to form CoO6 octahedra that share corners with two equivalent Co(3)O6 octahedra,  a cornercorner with one Co(2)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, and edges with two equivalent Co(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-57°. 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 Co(3), and two equivalent Co(4) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1), one Co(1), and two equivalent Co(3) atoms to form distorted edge-sharing OMg2Co3 trigonal bipyramids. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1), one Co(2), and one Co(4) atom. In the fourth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Mg(1) and two equivalent Co(1) atoms. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Co(4) and two equivalent Co(1) atoms. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Co(3) and two equivalent Co(2) atoms. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Co(1) and two equivalent Co(4) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Co(2) and two equivalent Co(3) atoms.
Mg(CoO2)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with two equivalent Co(3)O6 octahedra, corners with two equivalent Co(2)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and  a faceface with one Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-47°. The Mg(1)-O(1) bond length is 2.11 Å. The Mg(1)-O(4) bond length is 1.97 Å. There is one shorter (2.16 Å) and one longer (2.20 Å) Mg(1)-O(2) bond length. There is one shorter (2.00 Å) and one longer (2.03 Å) Mg(1)-O(3) bond length. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form CoO6 octahedra that share corners with two equivalent Co(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, and edges with two equivalent Co(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-55°. The Co(1)-O(2) bond length is 1.95 Å. The Co(1)-O(7) bond length is 1.86 Å. There is one shorter (1.88 Å) and one longer (1.92 Å) Co(1)-O(4) bond length. There is one shorter (1.93 Å) and one longer (1.94 Å) Co(1)-O(5) bond length. In the second Co site, Co(2) is bonded to one O(3), one O(8), and two equivalent O(6) atoms to form CoO4 tetrahedra that share  a cornercorner with one Co(4)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Co(2)O4 tetrahedra, and edges with two equivalent Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-62°. The Co(2)-O(3) bond length is 1.85 Å. The Co(2)-O(8) bond length is 1.92 Å. There is one shorter (1.84 Å) and one longer (1.88 Å) Co(2)-O(6) bond length. In the third Co site, Co(3) is bonded to one O(1), one O(6), two equivalent O(2), and two equivalent O(8) atoms to form distorted CoO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Co(1)O6 octahedra, corners with two equivalent Co(4)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, edges with two equivalent Co(2)O4 tetrahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-57°. The Co(3)-O(1) bond length is 2.12 Å. The Co(3)-O(6) bond length is 2.11 Å. There is one shorter (1.92 Å) and one longer (2.42 Å) Co(3)-O(2) bond length. There is one shorter (1.88 Å) and one longer (1.97 Å) Co(3)-O(8) bond length. In the fourth Co site, Co(4) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(7) atoms to form CoO6 octahedra that share corners with two equivalent Co(3)O6 octahedra,  a cornercorner with one Co(2)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, and edges with two equivalent Co(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-57°. The Co(4)-O(3) bond length is 1.95 Å. The Co(4)-O(5) bond length is 1.86 Å. There is one shorter (1.88 Å) and one longer (1.97 Å) Co(4)-O(1) bond length. There is one shorter (1.91 Å) and one longer (1.92 Å) Co(4)-O(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 Co(3), and two equivalent Co(4) atoms. In the second O site, O(2) is bonded to two equivalent Mg(1), one Co(1), and two equivalent Co(3) atoms to form distorted edge-sharing OMg2Co3 trigonal bipyramids. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1), one Co(2), and one Co(4) atom. In the fourth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Mg(1) and two equivalent Co(1) atoms. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Co(4) and two equivalent Co(1) atoms. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Co(3) and two equivalent Co(2) atoms. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Co(1) and two equivalent Co(4) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Co(2) and two equivalent Co(3) atoms.