Mg(BiO2)4 crystallizes in the monoclinic Cm 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 MgO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Bi(1)O6 octahedra, and edges with two equivalent Bi(4)O6 octahedra. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form distorted BiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Bi(1)O6 octahedra, and edges with two equivalent Bi(4)O6 octahedra. In the second Bi site, Bi(2) is bonded in a 3-coordinate geometry to one O(4), one O(8), and two equivalent O(6) atoms. In the third Bi site, Bi(3) is bonded in a 4-coordinate geometry to one O(1), one O(6), and two equivalent O(8) atoms. In the fourth Bi site, Bi(4) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(7) atoms to form BiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Bi(1)O6 octahedra, and edges with two equivalent Bi(4)O6 octahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Bi(3), and two equivalent Bi(4) atoms to form corner-sharing OMgBi3 trigonal pyramids. In the second O site, O(2) is bonded in a distorted T-shaped geometry to two equivalent Mg(1) and one Bi(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Mg(1) and one Bi(4) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Bi(2), and two equivalent Bi(1) atoms. In the fifth O site, O(5) is bonded in a trigonal non-coplanar geometry to one Bi(4) and two equivalent Bi(1) atoms. In the sixth O site, O(6) is bonded in a trigonal non-coplanar geometry to one Bi(3) and two equivalent Bi(2) atoms. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Bi(1) and two equivalent Bi(4) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Bi(2) and two equivalent Bi(3) atoms.
Mg(BiO2)4 crystallizes in the monoclinic Cm 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 MgO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Bi(1)O6 octahedra, and edges with two equivalent Bi(4)O6 octahedra. The Mg(1)-O(1) bond length is 2.09 Å. The Mg(1)-O(4) bond length is 2.03 Å. Both Mg(1)-O(2) bond lengths are 2.19 Å. Both Mg(1)-O(3) bond lengths are 2.25 Å. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form distorted BiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Bi(1)O6 octahedra, and edges with two equivalent Bi(4)O6 octahedra. The Bi(1)-O(2) bond length is 2.21 Å. The Bi(1)-O(7) bond length is 2.65 Å. Both Bi(1)-O(4) bond lengths are 2.39 Å. Both Bi(1)-O(5) bond lengths are 2.40 Å. In the second Bi site, Bi(2) is bonded in a 3-coordinate geometry to one O(4), one O(8), and two equivalent O(6) atoms. The Bi(2)-O(4) bond length is 2.22 Å. The Bi(2)-O(8) bond length is 2.49 Å. Both Bi(2)-O(6) bond lengths are 2.20 Å. In the third Bi site, Bi(3) is bonded in a 4-coordinate geometry to one O(1), one O(6), and two equivalent O(8) atoms. The Bi(3)-O(1) bond length is 2.39 Å. The Bi(3)-O(6) bond length is 2.35 Å. Both Bi(3)-O(8) bond lengths are 2.18 Å. In the fourth Bi site, Bi(4) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(7) atoms to form BiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Bi(1)O6 octahedra, and edges with two equivalent Bi(4)O6 octahedra. The Bi(4)-O(3) bond length is 2.10 Å. The Bi(4)-O(5) bond length is 2.12 Å. Both Bi(4)-O(1) bond lengths are 2.32 Å. Both Bi(4)-O(7) bond lengths are 2.18 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Bi(3), and two equivalent Bi(4) atoms to form corner-sharing OMgBi3 trigonal pyramids. In the second O site, O(2) is bonded in a distorted T-shaped geometry to two equivalent Mg(1) and one Bi(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Mg(1) and one Bi(4) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Bi(2), and two equivalent Bi(1) atoms. In the fifth O site, O(5) is bonded in a trigonal non-coplanar geometry to one Bi(4) and two equivalent Bi(1) atoms. In the sixth O site, O(6) is bonded in a trigonal non-coplanar geometry to one Bi(3) and two equivalent Bi(2) atoms. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Bi(1) and two equivalent Bi(4) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Bi(2) and two equivalent Bi(3) atoms.