Rb4Mg3H10 crystallizes in the orthorhombic Cmce space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 10-coordinate geometry to one H(1), two equivalent H(3), three equivalent H(2), and four equivalent H(4) atoms. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to one H(2), two equivalent H(1), and four equivalent H(4) atoms. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent H(2) and four equivalent H(4) atoms to form face-sharing MgH6 octahedra. In the second Mg site, Mg(2) is bonded to one H(1), one H(2), two equivalent H(3), and two equivalent H(4) atoms to form a mixture of corner and face-sharing MgH6 octahedra. The corner-sharing octahedral tilt angles are 9°. There are four inequivalent H sites. In the first H site, H(2) is bonded to one Rb(2), three equivalent Rb(1), one Mg(1), and one Mg(2) atom to form a mixture of distorted corner and edge-sharing HRb4Mg2 octahedra. The corner-sharing octahedral tilt angles range from 0-8°. In the second H site, H(3) is bonded in a distorted linear geometry to two equivalent Rb(1) and two equivalent Mg(2) atoms. In the third H site, H(4) is bonded in a 2-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), one Mg(1), and one Mg(2) atom. In the fourth H site, H(1) is bonded in a distorted single-bond geometry to one Rb(1), two equivalent Rb(2), and one Mg(2) atom.
Rb4Mg3H10 crystallizes in the orthorhombic Cmce space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 10-coordinate geometry to one H(1), two equivalent H(3), three equivalent H(2), and four equivalent H(4) atoms. The Rb(1)-H(1) bond length is 2.85 Å. Both Rb(1)-H(3) bond lengths are 3.01 Å. There is one shorter (2.92 Å) and two longer (3.00 Å) Rb(1)-H(2) bond lengths. There are two shorter (2.93 Å) and two longer (3.05 Å) Rb(1)-H(4) bond lengths. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to one H(2), two equivalent H(1), and four equivalent H(4) atoms. The Rb(2)-H(2) bond length is 3.09 Å. Both Rb(2)-H(1) bond lengths are 3.05 Å. There are two shorter (2.95 Å) and two longer (3.08 Å) Rb(2)-H(4) bond lengths. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent H(2) and four equivalent H(4) atoms to form face-sharing MgH6 octahedra. Both Mg(1)-H(2) bond lengths are 1.97 Å. All Mg(1)-H(4) bond lengths are 1.96 Å. In the second Mg site, Mg(2) is bonded to one H(1), one H(2), two equivalent H(3), and two equivalent H(4) atoms to form a mixture of corner and face-sharing MgH6 octahedra. The corner-sharing octahedral tilt angles are 9°. The Mg(2)-H(1) bond length is 1.89 Å. The Mg(2)-H(2) bond length is 2.11 Å. Both Mg(2)-H(3) bond lengths are 1.96 Å. Both Mg(2)-H(4) bond lengths are 2.06 Å. There are four inequivalent H sites. In the first H site, H(2) is bonded to one Rb(2), three equivalent Rb(1), one Mg(1), and one Mg(2) atom to form a mixture of distorted corner and edge-sharing HRb4Mg2 octahedra. The corner-sharing octahedral tilt angles range from 0-8°. In the second H site, H(3) is bonded in a distorted linear geometry to two equivalent Rb(1) and two equivalent Mg(2) atoms. In the third H site, H(4) is bonded in a 2-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), one Mg(1), and one Mg(2) atom. In the fourth H site, H(1) is bonded in a distorted single-bond geometry to one Rb(1), two equivalent Rb(2), and one Mg(2) atom.