Cs3CoI5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one I(1), one I(4), two equivalent I(3), and four equivalent I(2) atoms. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to two equivalent I(1), two equivalent I(3), two equivalent I(4), and three equivalent I(2) atoms. Co(1) is bonded in a tetrahedral geometry to one I(1), one I(4), and two equivalent I(2) atoms. There are four inequivalent I sites. In the first I site, I(1) is bonded to one Cs(1), four equivalent Cs(2), and one Co(1) atom to form distorted ICs5Co octahedra that share corners with five equivalent I(3)Cs6 octahedra,  an edgeedge with one I(3)Cs6 octahedra, edges with two equivalent I(1)Cs5Co octahedra, and  a faceface with one I(3)Cs6 octahedra. The corner-sharing octahedral tilt angles range from 35-48°. In the second I site, I(2) is bonded in a 6-coordinate geometry to two equivalent Cs(1), three equivalent Cs(2), and one Co(1) atom. In the third I site, I(3) is bonded to two equivalent Cs(1) and four equivalent Cs(2) atoms to form ICs6 octahedra that share corners with five equivalent I(1)Cs5Co octahedra,  an edgeedge with one I(1)Cs5Co octahedra,  a faceface with one I(1)Cs5Co octahedra, and faces with two equivalent I(3)Cs6 octahedra. The corner-sharing octahedral tilt angles range from 35-48°. In the fourth I site, I(4) is bonded in a distorted single-bond geometry to one Cs(1), four equivalent Cs(2), and one Co(1) atom.
Cs3CoI5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one I(1), one I(4), two equivalent I(3), and four equivalent I(2) atoms. The Cs(1)-I(1) bond length is 3.94 Å. The Cs(1)-I(4) bond length is 4.02 Å. There is one shorter (3.83 Å) and one longer (4.05 Å) Cs(1)-I(3) bond length. There are two shorter (3.81 Å) and two longer (3.92 Å) Cs(1)-I(2) bond lengths. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to two equivalent I(1), two equivalent I(3), two equivalent I(4), and three equivalent I(2) atoms. There is one shorter (3.95 Å) and one longer (4.04 Å) Cs(2)-I(1) bond length. There is one shorter (3.85 Å) and one longer (3.95 Å) Cs(2)-I(3) bond length. There is one shorter (4.12 Å) and one longer (4.25 Å) Cs(2)-I(4) bond length. There are a spread of Cs(2)-I(2) bond distances ranging from 4.14-4.34 Å. Co(1) is bonded in a tetrahedral geometry to one I(1), one I(4), and two equivalent I(2) atoms. The Co(1)-I(1) bond length is 2.59 Å. The Co(1)-I(4) bond length is 2.59 Å. Both Co(1)-I(2) bond lengths are 2.59 Å. There are four inequivalent I sites. In the first I site, I(1) is bonded to one Cs(1), four equivalent Cs(2), and one Co(1) atom to form distorted ICs5Co octahedra that share corners with five equivalent I(3)Cs6 octahedra,  an edgeedge with one I(3)Cs6 octahedra, edges with two equivalent I(1)Cs5Co octahedra, and  a faceface with one I(3)Cs6 octahedra. The corner-sharing octahedral tilt angles range from 35-48°. In the second I site, I(2) is bonded in a 6-coordinate geometry to two equivalent Cs(1), three equivalent Cs(2), and one Co(1) atom. In the third I site, I(3) is bonded to two equivalent Cs(1) and four equivalent Cs(2) atoms to form ICs6 octahedra that share corners with five equivalent I(1)Cs5Co octahedra,  an edgeedge with one I(1)Cs5Co octahedra,  a faceface with one I(1)Cs5Co octahedra, and faces with two equivalent I(3)Cs6 octahedra. The corner-sharing octahedral tilt angles range from 35-48°. In the fourth I site, I(4) is bonded in a distorted single-bond geometry to one Cs(1), four equivalent Cs(2), and one Co(1) atom.