Rb2CoI4 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 10-coordinate geometry to one Co(1), one I(2), four equivalent I(1), and four equivalent I(3) atoms. In the second Rb site, Rb(2) is bonded in a 8-coordinate geometry to one I(1), three equivalent I(2), and four equivalent I(3) atoms. Co(1) is bonded to one Rb(1), one I(1), one I(2), and two equivalent I(3) atoms to form CoRbI4 tetrahedra that share corners with four equivalent I(3)Rb4Co square pyramids. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 6-coordinate geometry to one Rb(2), four equivalent Rb(1), and one Co(1) atom. In the second I site, I(2) is bonded in a 5-coordinate geometry to one Rb(1), three equivalent Rb(2), and one Co(1) atom. In the third I site, I(3) is bonded to two equivalent Rb(1), two equivalent Rb(2), and one Co(1) atom to form distorted IRb4Co square pyramids that share corners with four equivalent I(3)Rb4Co square pyramids, corners with two equivalent Co(1)RbI4 tetrahedra, edges with three equivalent I(3)Rb4Co square pyramids, and  a faceface with one I(3)Rb4Co square pyramid.
Rb2CoI4 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 10-coordinate geometry to one Co(1), one I(2), four equivalent I(1), and four equivalent I(3) atoms. The Rb(1)-Co(1) bond length is 4.06 Å. The Rb(1)-I(2) bond length is 3.65 Å. There are a spread of Rb(1)-I(1) bond distances ranging from 3.78-4.26 Å. There are two shorter (3.75 Å) and two longer (3.84 Å) Rb(1)-I(3) bond lengths. In the second Rb site, Rb(2) is bonded in a 8-coordinate geometry to one I(1), three equivalent I(2), and four equivalent I(3) atoms. The Rb(2)-I(1) bond length is 3.86 Å. There is one shorter (3.76 Å) and two longer (4.18 Å) Rb(2)-I(2) bond lengths. There are two shorter (3.79 Å) and two longer (3.82 Å) Rb(2)-I(3) bond lengths. Co(1) is bonded to one Rb(1), one I(1), one I(2), and two equivalent I(3) atoms to form CoRbI4 tetrahedra that share corners with four equivalent I(3)Rb4Co square pyramids. The Co(1)-I(1) bond length is 2.60 Å. The Co(1)-I(2) bond length is 2.59 Å. Both Co(1)-I(3) bond lengths are 2.58 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 6-coordinate geometry to one Rb(2), four equivalent Rb(1), and one Co(1) atom. In the second I site, I(2) is bonded in a 5-coordinate geometry to one Rb(1), three equivalent Rb(2), and one Co(1) atom. In the third I site, I(3) is bonded to two equivalent Rb(1), two equivalent Rb(2), and one Co(1) atom to form distorted IRb4Co square pyramids that share corners with four equivalent I(3)Rb4Co square pyramids, corners with two equivalent Co(1)RbI4 tetrahedra, edges with three equivalent I(3)Rb4Co square pyramids, and  a faceface with one I(3)Rb4Co square pyramid.