MgH12SeO9 crystallizes in the trigonal R3 space group. Mg(1) is bonded in an octahedral geometry to three equivalent O(2) and three equivalent O(3) atoms. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(2) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(1) and one O(2) atom. In the third H site, H(3) is bonded in a distorted single-bond geometry to one O(1) and one O(3) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(1) and one O(3) atom. Se(1) is bonded in a trigonal non-coplanar geometry to three equivalent O(1) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to one H(2), one H(3), one H(4), and one Se(1) atom to form distorted corner-sharing OH3Se tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one H(1), and one H(2) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to one Mg(1), one H(3), and one H(4) atom.
MgH12SeO9 crystallizes in the trigonal R3 space group. Mg(1) is bonded in an octahedral geometry to three equivalent O(2) and three equivalent O(3) atoms. All Mg(1)-O(2) bond lengths are 2.08 Å. All Mg(1)-O(3) bond lengths are 2.15 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(2) atom. The H(1)-O(2) bond length is 0.99 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(1) and one O(2) atom. The H(2)-O(1) bond length is 1.71 Å. The H(2)-O(2) bond length is 1.00 Å. In the third H site, H(3) is bonded in a distorted single-bond geometry to one O(1) and one O(3) atom. The H(3)-O(1) bond length is 1.64 Å. The H(3)-O(3) bond length is 1.01 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(1) and one O(3) atom. The H(4)-O(1) bond length is 1.70 Å. The H(4)-O(3) bond length is 1.00 Å. Se(1) is bonded in a trigonal non-coplanar geometry to three equivalent O(1) atoms. All Se(1)-O(1) bond lengths are 1.74 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to one H(2), one H(3), one H(4), and one Se(1) atom to form distorted corner-sharing OH3Se tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one H(1), and one H(2) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to one Mg(1), one H(3), and one H(4) atom.