RbMgAs(H6O5)2 crystallizes in the orthorhombic Pmn2_1 space group. Rb(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(3), and two equivalent O(4) atoms. Mg(1) is bonded in an octahedral geometry to one O(6), one O(7), two equivalent O(3), and two equivalent O(4) atoms. As(1) is bonded in a tetrahedral geometry to one O(1), one O(2), and two equivalent O(5) atoms. There are seven inequivalent H sites. In the first H site, H(1) is bonded in a distorted single-bond geometry to one O(3) and one O(5) atom. In the second H site, H(2) is bonded in a distorted single-bond geometry to one O(1) and one O(4) atom. In the third H site, H(3) is bonded in a distorted linear geometry to one O(2) and one O(7) atom. In the fourth H site, H(4) is bonded in a distorted linear geometry to one O(2) and one O(3) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one O(7) atom. In the sixth H site, H(6) is bonded in a distorted single-bond geometry to one O(5) and one O(6) atom. In the seventh H site, H(7) is bonded in a distorted single-bond geometry to one O(4) and one O(5) atom. There are seven inequivalent O sites. In the first O site, O(3) is bonded in a 3-coordinate geometry to one Rb(1), one Mg(1), one H(1), and one H(4) atom. In the second O site, O(4) is bonded in a distorted water-like geometry to one Rb(1), one Mg(1), one H(2), and one H(7) atom. In the third O site, O(5) is bonded to one As(1), one H(1), one H(6), and one H(7) atom to form distorted OAsH3 tetrahedra that share  a cornercorner with one O(2)AsH3 tetrahedra,  a cornercorner with one O(5)AsH3 tetrahedra, and  a cornercorner with one O(1)RbAsH2 tetrahedra. In the fourth O site, O(6) is bonded in a distorted water-like geometry to one Mg(1) and two equivalent H(6) atoms. In the fifth O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one H(3), and one H(5) atom. In the sixth O site, O(1) is bonded to one Rb(1), one As(1), and two equivalent H(2) atoms to form distorted corner-sharing ORbAsH2 tetrahedra. In the seventh O site, O(2) is bonded to one As(1), one H(3), and two equivalent H(4) atoms to form OAsH3 tetrahedra that share  a cornercorner with one O(1)RbAsH2 tetrahedra and corners with two equivalent O(5)AsH3 tetrahedra.
RbMgAs(H6O5)2 crystallizes in the orthorhombic Pmn2_1 space group. Rb(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(3), and two equivalent O(4) atoms. The Rb(1)-O(1) bond length is 2.97 Å. Both Rb(1)-O(3) bond lengths are 3.18 Å. Both Rb(1)-O(4) bond lengths are 3.05 Å. Mg(1) is bonded in an octahedral geometry to one O(6), one O(7), two equivalent O(3), and two equivalent O(4) atoms. The Mg(1)-O(6) bond length is 2.16 Å. The Mg(1)-O(7) bond length is 2.12 Å. Both Mg(1)-O(3) bond lengths are 2.10 Å. Both Mg(1)-O(4) bond lengths are 2.12 Å. As(1) is bonded in a tetrahedral geometry to one O(1), one O(2), and two equivalent O(5) atoms. The As(1)-O(1) bond length is 1.72 Å. The As(1)-O(2) bond length is 1.73 Å. Both As(1)-O(5) bond lengths are 1.73 Å. There are seven inequivalent H sites. In the first H site, H(1) is bonded in a distorted single-bond geometry to one O(3) and one O(5) atom. The H(1)-O(3) bond length is 1.00 Å. The H(1)-O(5) bond length is 1.67 Å. In the second H site, H(2) is bonded in a distorted single-bond geometry to one O(1) and one O(4) atom. The H(2)-O(1) bond length is 1.67 Å. The H(2)-O(4) bond length is 1.01 Å. In the third H site, H(3) is bonded in a distorted linear geometry to one O(2) and one O(7) atom. The H(3)-O(2) bond length is 1.63 Å. The H(3)-O(7) bond length is 1.01 Å. In the fourth H site, H(4) is bonded in a distorted linear geometry to one O(2) and one O(3) atom. The H(4)-O(2) bond length is 1.63 Å. The H(4)-O(3) bond length is 1.01 Å. In the fifth H site, H(5) is bonded in a single-bond geometry to one O(7) atom. The H(5)-O(7) bond length is 0.98 Å. In the sixth H site, H(6) is bonded in a distorted single-bond geometry to one O(5) and one O(6) atom. The H(6)-O(5) bond length is 1.64 Å. The H(6)-O(6) bond length is 1.01 Å. In the seventh H site, H(7) is bonded in a distorted single-bond geometry to one O(4) and one O(5) atom. The H(7)-O(4) bond length is 1.00 Å. The H(7)-O(5) bond length is 1.68 Å. There are seven inequivalent O sites. In the first O site, O(3) is bonded in a 3-coordinate geometry to one Rb(1), one Mg(1), one H(1), and one H(4) atom. In the second O site, O(4) is bonded in a distorted water-like geometry to one Rb(1), one Mg(1), one H(2), and one H(7) atom. In the third O site, O(5) is bonded to one As(1), one H(1), one H(6), and one H(7) atom to form distorted OAsH3 tetrahedra that share  a cornercorner with one O(2)AsH3 tetrahedra,  a cornercorner with one O(5)AsH3 tetrahedra, and  a cornercorner with one O(1)RbAsH2 tetrahedra. In the fourth O site, O(6) is bonded in a distorted water-like geometry to one Mg(1) and two equivalent H(6) atoms. In the fifth O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one H(3), and one H(5) atom. In the sixth O site, O(1) is bonded to one Rb(1), one As(1), and two equivalent H(2) atoms to form distorted corner-sharing ORbAsH2 tetrahedra. In the seventh O site, O(2) is bonded to one As(1), one H(3), and two equivalent H(4) atoms to form OAsH3 tetrahedra that share  a cornercorner with one O(1)RbAsH2 tetrahedra and corners with two equivalent O(5)AsH3 tetrahedra.