Mg(ReO4)2 crystallizes in the trigonal P31m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent O(3) and three equivalent O(5) atoms to form MgO6 octahedra that share corners with three equivalent Re(1)O4 tetrahedra and corners with three equivalent Re(2)O4 tetrahedra. In the second Mg site, Mg(2) is bonded to three equivalent O(1) and three equivalent O(6) atoms to form MgO6 octahedra that share corners with three equivalent Re(1)O4 tetrahedra and corners with three equivalent Re(2)O4 tetrahedra. There are two inequivalent Re sites. In the first Re site, Re(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form ReO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra and corners with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-46°. In the second Re site, Re(2) is bonded to one O(4), one O(6), and two equivalent O(5) atoms to form ReO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra and corners with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 13-41°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Mg(2) and one Re(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Re(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one Re(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Re(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Mg(1) and one Re(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(2) and one Re(2) atom.
Mg(ReO4)2 crystallizes in the trigonal P31m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent O(3) and three equivalent O(5) atoms to form MgO6 octahedra that share corners with three equivalent Re(1)O4 tetrahedra and corners with three equivalent Re(2)O4 tetrahedra. All Mg(1)-O(3) bond lengths are 2.16 Å. All Mg(1)-O(5) bond lengths are 2.09 Å. In the second Mg site, Mg(2) is bonded to three equivalent O(1) and three equivalent O(6) atoms to form MgO6 octahedra that share corners with three equivalent Re(1)O4 tetrahedra and corners with three equivalent Re(2)O4 tetrahedra. All Mg(2)-O(1) bond lengths are 2.08 Å. All Mg(2)-O(6) bond lengths are 2.26 Å. There are two inequivalent Re sites. In the first Re site, Re(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form ReO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra and corners with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-46°. The Re(1)-O(1) bond length is 1.76 Å. The Re(1)-O(2) bond length is 1.72 Å. Both Re(1)-O(3) bond lengths are 1.77 Å. In the second Re site, Re(2) is bonded to one O(4), one O(6), and two equivalent O(5) atoms to form ReO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra and corners with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 13-41°. The Re(2)-O(4) bond length is 1.72 Å. The Re(2)-O(6) bond length is 1.77 Å. Both Re(2)-O(5) bond lengths are 1.76 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Mg(2) and one Re(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Re(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one Re(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Re(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Mg(1) and one Re(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(2) and one Re(2) atom.