MgHg2(BiO3)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form MgO4 tetrahedra that share corners with two equivalent Bi(1)O6 octahedra and  an edgeedge with one Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 18-57°. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a 3-coordinate geometry to one O(2), one O(3), and one O(6) atom. In the second Hg site, Hg(2) is bonded in a 3-coordinate geometry to one O(1), one O(4), and one O(5) atom. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted BiO6 octahedra that share corners with two equivalent Mg(1)O4 tetrahedra and  an edgeedge with one Mg(1)O4 tetrahedra. In the second Bi site, Bi(2) is bonded in a distorted T-shaped geometry to one O(1), one O(2), and one O(3) atom. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Hg(2), one Bi(1), and one Bi(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Hg(1), one Bi(1), and one Bi(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Hg(1), one Bi(1), and one Bi(2) atom. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Mg(1), one Hg(2), and one Bi(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mg(1), one Hg(2), and one Bi(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Hg(1), and one Bi(1) atom.
MgHg2(BiO3)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form MgO4 tetrahedra that share corners with two equivalent Bi(1)O6 octahedra and  an edgeedge with one Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 18-57°. The Mg(1)-O(1) bond length is 1.98 Å. The Mg(1)-O(4) bond length is 1.99 Å. The Mg(1)-O(5) bond length is 2.01 Å. The Mg(1)-O(6) bond length is 1.99 Å. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a 3-coordinate geometry to one O(2), one O(3), and one O(6) atom. The Hg(1)-O(2) bond length is 2.16 Å. The Hg(1)-O(3) bond length is 2.15 Å. The Hg(1)-O(6) bond length is 2.34 Å. In the second Hg site, Hg(2) is bonded in a 3-coordinate geometry to one O(1), one O(4), and one O(5) atom. The Hg(2)-O(1) bond length is 2.58 Å. The Hg(2)-O(4) bond length is 2.11 Å. The Hg(2)-O(5) bond length is 2.07 Å. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted BiO6 octahedra that share corners with two equivalent Mg(1)O4 tetrahedra and  an edgeedge with one Mg(1)O4 tetrahedra. The Bi(1)-O(1) bond length is 2.65 Å. The Bi(1)-O(2) bond length is 2.59 Å. The Bi(1)-O(3) bond length is 2.49 Å. The Bi(1)-O(4) bond length is 2.31 Å. The Bi(1)-O(5) bond length is 2.30 Å. The Bi(1)-O(6) bond length is 2.21 Å. In the second Bi site, Bi(2) is bonded in a distorted T-shaped geometry to one O(1), one O(2), and one O(3) atom. The Bi(2)-O(1) bond length is 2.10 Å. The Bi(2)-O(2) bond length is 2.16 Å. The Bi(2)-O(3) bond length is 2.12 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Hg(2), one Bi(1), and one Bi(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Hg(1), one Bi(1), and one Bi(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Hg(1), one Bi(1), and one Bi(2) atom. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Mg(1), one Hg(2), and one Bi(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mg(1), one Hg(2), and one Bi(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Hg(1), and one Bi(1) atom.