Mg3MnH7 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to six equivalent H(1) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one H(2) and nine equivalent H(1) atoms. Mn(1) is bonded in an octahedral geometry to six equivalent H(1) atoms. There are two inequivalent H sites. In the first H site, H(1) is bonded in a 5-coordinate geometry to one Mg(1), three equivalent Mg(2), and one Mn(1) atom. In the second H site, H(2) is bonded in a linear geometry to two equivalent Mg(2) atoms.
Mg3MnH7 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to six equivalent H(1) atoms. All Mg(1)-H(1) bond lengths are 2.07 Å. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one H(2) and nine equivalent H(1) atoms. The Mg(2)-H(2) bond length is 1.88 Å. There are three shorter (2.12 Å) and six longer (2.34 Å) Mg(2)-H(1) bond lengths. Mn(1) is bonded in an octahedral geometry to six equivalent H(1) atoms. All Mn(1)-H(1) bond lengths are 1.62 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a 5-coordinate geometry to one Mg(1), three equivalent Mg(2), and one Mn(1) atom. In the second H site, H(2) is bonded in a linear geometry to two equivalent Mg(2) atoms.