Rb2CdI4 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one I(1), one I(3), and four equivalent I(2) atoms to form distorted RbI6 pentagonal pyramids that share corners with four equivalent Rb(2)I6 pentagonal pyramids, corners with two equivalent Cd(1)I4 tetrahedra, edges with two equivalent Rb(1)I6 pentagonal pyramids, edges with two equivalent Cd(1)I4 tetrahedra, and faces with two equivalent Rb(2)I6 pentagonal pyramids. In the second Rb site, Rb(2) is bonded to one I(1), one I(3), and four equivalent I(2) atoms to form distorted RbI6 pentagonal pyramids that share corners with four equivalent Rb(1)I6 pentagonal pyramids, corners with four equivalent Cd(1)I4 tetrahedra, edges with two equivalent Rb(2)I6 pentagonal pyramids,  an edgeedge with one Cd(1)I4 tetrahedra, and faces with two equivalent Rb(1)I6 pentagonal pyramids. Cd(1) is bonded to one I(1), one I(3), and two equivalent I(2) atoms to form CdI4 tetrahedra that share corners with two equivalent Rb(1)I6 pentagonal pyramids, corners with four equivalent Rb(2)I6 pentagonal pyramids,  an edgeedge with one Rb(2)I6 pentagonal pyramid, and edges with two equivalent Rb(1)I6 pentagonal pyramids. There are three inequivalent I sites. In the first I site, I(1) is bonded in a distorted T-shaped geometry to one Rb(1), one Rb(2), and one Cd(1) atom. In the second I site, I(2) is bonded to two equivalent Rb(1), two equivalent Rb(2), and one Cd(1) atom to form a mixture of distorted face, corner, and edge-sharing IRb4Cd square pyramids. In the third I site, I(3) is bonded in a distorted T-shaped geometry to one Rb(1), one Rb(2), and one Cd(1) atom.
Rb2CdI4 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one I(1), one I(3), and four equivalent I(2) atoms to form distorted RbI6 pentagonal pyramids that share corners with four equivalent Rb(2)I6 pentagonal pyramids, corners with two equivalent Cd(1)I4 tetrahedra, edges with two equivalent Rb(1)I6 pentagonal pyramids, edges with two equivalent Cd(1)I4 tetrahedra, and faces with two equivalent Rb(2)I6 pentagonal pyramids. The Rb(1)-I(1) bond length is 3.74 Å. The Rb(1)-I(3) bond length is 3.69 Å. There are two shorter (3.74 Å) and two longer (3.80 Å) Rb(1)-I(2) bond lengths. In the second Rb site, Rb(2) is bonded to one I(1), one I(3), and four equivalent I(2) atoms to form distorted RbI6 pentagonal pyramids that share corners with four equivalent Rb(1)I6 pentagonal pyramids, corners with four equivalent Cd(1)I4 tetrahedra, edges with two equivalent Rb(2)I6 pentagonal pyramids,  an edgeedge with one Cd(1)I4 tetrahedra, and faces with two equivalent Rb(1)I6 pentagonal pyramids. The Rb(2)-I(1) bond length is 3.74 Å. The Rb(2)-I(3) bond length is 3.71 Å. There are two shorter (3.79 Å) and two longer (3.81 Å) Rb(2)-I(2) bond lengths. Cd(1) is bonded to one I(1), one I(3), and two equivalent I(2) atoms to form CdI4 tetrahedra that share corners with two equivalent Rb(1)I6 pentagonal pyramids, corners with four equivalent Rb(2)I6 pentagonal pyramids,  an edgeedge with one Rb(2)I6 pentagonal pyramid, and edges with two equivalent Rb(1)I6 pentagonal pyramids. The Cd(1)-I(1) bond length is 2.80 Å. The Cd(1)-I(3) bond length is 2.79 Å. Both Cd(1)-I(2) bond lengths are 2.82 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded in a distorted T-shaped geometry to one Rb(1), one Rb(2), and one Cd(1) atom. In the second I site, I(2) is bonded to two equivalent Rb(1), two equivalent Rb(2), and one Cd(1) atom to form a mixture of distorted face, corner, and edge-sharing IRb4Cd square pyramids. In the third I site, I(3) is bonded in a distorted T-shaped geometry to one Rb(1), one Rb(2), and one Cd(1) atom.