Mg3Fe2H4(Se3O10)2 crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra and corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 62-65°. In the second Mg site, Mg(2) is bonded to one O(1), one O(10), one O(3), one O(7), one O(8), and one O(9) atom to form MgO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 65°. Fe(1) is bonded to one O(10), one O(4), one O(5), one O(7), and two equivalent O(6) atoms to form FeO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 62°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(8) and one O(9) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(4) and one O(9) atom. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(2), one O(3), and one O(4) atom. In the second Se site, Se(2) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(6), and one O(7) atom. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one O(10), one O(5), and one O(8) atom. There are ten inequivalent O sites. In the first O site, O(10) is bonded in a trigonal planar geometry to one Mg(2), one Fe(1), and one Se(3) atom. In the second O site, O(1) is bonded in a trigonal planar geometry to one Mg(1), one Mg(2), and one Se(2) atom. In the third O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one Se(1) atom. In the fourth O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(2) and one Se(1) atom. In the fifth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Fe(1), one H(2), and one Se(1) atom. In the sixth O site, O(5) is bonded in a trigonal planar geometry to one Mg(1), one Fe(1), and one Se(3) atom. In the seventh O site, O(6) is bonded in a distorted trigonal planar geometry to two equivalent Fe(1) and one Se(2) atom. In the eighth O site, O(7) is bonded in a trigonal planar geometry to one Mg(2), one Fe(1), and one Se(2) atom. In the ninth O site, O(8) is bonded in a distorted trigonal planar geometry to one Mg(2), one H(1), and one Se(3) atom. In the tenth O site, O(9) is bonded in a distorted trigonal planar geometry to one Mg(2), one H(1), and one H(2) atom.
Mg3Fe2H4(Se3O10)2 crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra and corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 62-65°. Both Mg(1)-O(1) bond lengths are 2.13 Å. Both Mg(1)-O(2) bond lengths are 2.00 Å. Both Mg(1)-O(5) bond lengths are 2.14 Å. In the second Mg site, Mg(2) is bonded to one O(1), one O(10), one O(3), one O(7), one O(8), and one O(9) atom to form MgO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 65°. The Mg(2)-O(1) bond length is 2.20 Å. The Mg(2)-O(10) bond length is 2.10 Å. The Mg(2)-O(3) bond length is 2.04 Å. The Mg(2)-O(7) bond length is 2.12 Å. The Mg(2)-O(8) bond length is 2.04 Å. The Mg(2)-O(9) bond length is 2.04 Å. Fe(1) is bonded to one O(10), one O(4), one O(5), one O(7), and two equivalent O(6) atoms to form FeO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 62°. The Fe(1)-O(10) bond length is 2.03 Å. The Fe(1)-O(4) bond length is 1.93 Å. The Fe(1)-O(5) bond length is 2.02 Å. The Fe(1)-O(7) bond length is 2.03 Å. There is one shorter (2.05 Å) and one longer (2.07 Å) Fe(1)-O(6) bond length. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(8) and one O(9) atom. The H(1)-O(8) bond length is 1.73 Å. The H(1)-O(9) bond length is 0.98 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(4) and one O(9) atom. The H(2)-O(4) bond length is 1.75 Å. The H(2)-O(9) bond length is 0.98 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(2), one O(3), and one O(4) atom. The Se(1)-O(2) bond length is 1.71 Å. The Se(1)-O(3) bond length is 1.67 Å. The Se(1)-O(4) bond length is 1.75 Å. In the second Se site, Se(2) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(6), and one O(7) atom. The Se(2)-O(1) bond length is 1.69 Å. The Se(2)-O(6) bond length is 1.75 Å. The Se(2)-O(7) bond length is 1.74 Å. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one O(10), one O(5), and one O(8) atom. The Se(3)-O(10) bond length is 1.73 Å. The Se(3)-O(5) bond length is 1.76 Å. The Se(3)-O(8) bond length is 1.68 Å. There are ten inequivalent O sites. In the first O site, O(10) is bonded in a trigonal planar geometry to one Mg(2), one Fe(1), and one Se(3) atom. In the second O site, O(1) is bonded in a trigonal planar geometry to one Mg(1), one Mg(2), and one Se(2) atom. In the third O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one Se(1) atom. In the fourth O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(2) and one Se(1) atom. In the fifth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Fe(1), one H(2), and one Se(1) atom. In the sixth O site, O(5) is bonded in a trigonal planar geometry to one Mg(1), one Fe(1), and one Se(3) atom. In the seventh O site, O(6) is bonded in a distorted trigonal planar geometry to two equivalent Fe(1) and one Se(2) atom. In the eighth O site, O(7) is bonded in a trigonal planar geometry to one Mg(2), one Fe(1), and one Se(2) atom. In the ninth O site, O(8) is bonded in a distorted trigonal planar geometry to one Mg(2), one H(1), and one Se(3) atom. In the tenth O site, O(9) is bonded in a distorted trigonal planar geometry to one Mg(2), one H(1), and one H(2) atom.