RbTl(SO4)2 crystallizes in the trigonal R32 space group. Rb(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form distorted RbO12 cuboctahedra that share corners with six equivalent Tl(1)O6 pentagonal pyramids, edges with six equivalent Rb(1)O12 cuboctahedra, and edges with six equivalent S(1)O4 tetrahedra. Tl(1) is bonded to six equivalent O(2) atoms to form distorted TlO6 pentagonal pyramids that share corners with six equivalent Rb(1)O12 cuboctahedra and corners with six equivalent S(1)O4 tetrahedra. S(1) is bonded to one O(1) and three equivalent O(2) atoms to form SO4 tetrahedra that share corners with three equivalent Tl(1)O6 pentagonal pyramids and edges with three equivalent Rb(1)O12 cuboctahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Rb(1) and one S(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Rb(1), one Tl(1), and one S(1) atom.
RbTl(SO4)2 crystallizes in the trigonal R32 space group. Rb(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form distorted RbO12 cuboctahedra that share corners with six equivalent Tl(1)O6 pentagonal pyramids, edges with six equivalent Rb(1)O12 cuboctahedra, and edges with six equivalent S(1)O4 tetrahedra. All Rb(1)-O(1) bond lengths are 2.98 Å. All Rb(1)-O(2) bond lengths are 3.38 Å. Tl(1) is bonded to six equivalent O(2) atoms to form distorted TlO6 pentagonal pyramids that share corners with six equivalent Rb(1)O12 cuboctahedra and corners with six equivalent S(1)O4 tetrahedra. All Tl(1)-O(2) bond lengths are 2.25 Å. S(1) is bonded to one O(1) and three equivalent O(2) atoms to form SO4 tetrahedra that share corners with three equivalent Tl(1)O6 pentagonal pyramids and edges with three equivalent Rb(1)O12 cuboctahedra. The S(1)-O(1) bond length is 1.45 Å. All S(1)-O(2) bond lengths are 1.49 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Rb(1) and one S(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Rb(1), one Tl(1), and one S(1) atom.