Ce3CI5 crystallizes in the triclinic P-1 space group. There are three inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to two equivalent C(1), one I(1), one I(2), one I(3), and two equivalent I(4) atoms to form distorted CeC2I5 pentagonal bipyramids that share  a cornercorner with one Ce(2)CI5 octahedra, corners with two equivalent Ce(3)C2I5 pentagonal bipyramids, edges with three equivalent Ce(2)CI5 octahedra, edges with two equivalent Ce(1)C2I5 pentagonal bipyramids, and faces with two equivalent Ce(3)C2I5 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 3°. In the second Ce site, Ce(2) is bonded to one C(1), one I(1), one I(4), one I(5), and two equivalent I(3) atoms to form distorted CeCI5 octahedra that share  a cornercorner with one Ce(1)C2I5 pentagonal bipyramid,  an edgeedge with one Ce(2)CI5 octahedra, edges with three equivalent Ce(1)C2I5 pentagonal bipyramids, and edges with three equivalent Ce(3)C2I5 pentagonal bipyramids. In the third Ce site, Ce(3) is bonded to two equivalent C(1), one I(1), one I(3), one I(5), and two equivalent I(2) atoms to form distorted CeC2I5 pentagonal bipyramids that share corners with two equivalent Ce(1)C2I5 pentagonal bipyramids, edges with three equivalent Ce(2)CI5 octahedra, edges with two equivalent Ce(3)C2I5 pentagonal bipyramids, and faces with two equivalent Ce(1)C2I5 pentagonal bipyramids. C(1) is bonded in a 6-coordinate geometry to one Ce(2), two equivalent Ce(1), two equivalent Ce(3), and one C(1) atom. There are five inequivalent I sites. In the first I site, I(1) is bonded in a distorted T-shaped geometry to one Ce(1), one Ce(2), and one Ce(3) atom. In the second I site, I(2) is bonded in a 3-coordinate geometry to one Ce(1) and two equivalent Ce(3) atoms. In the third I site, I(3) is bonded in a rectangular see-saw-like geometry to one Ce(1), one Ce(3), and two equivalent Ce(2) atoms. In the fourth I site, I(4) is bonded in a distorted T-shaped geometry to one Ce(2) and two equivalent Ce(1) atoms. In the fifth I site, I(5) is bonded in a distorted L-shaped geometry to one Ce(2) and one Ce(3) atom.
Ce3CI5 crystallizes in the triclinic P-1 space group. There are three inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to two equivalent C(1), one I(1), one I(2), one I(3), and two equivalent I(4) atoms to form distorted CeC2I5 pentagonal bipyramids that share  a cornercorner with one Ce(2)CI5 octahedra, corners with two equivalent Ce(3)C2I5 pentagonal bipyramids, edges with three equivalent Ce(2)CI5 octahedra, edges with two equivalent Ce(1)C2I5 pentagonal bipyramids, and faces with two equivalent Ce(3)C2I5 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 3°. There is one shorter (2.65 Å) and one longer (2.66 Å) Ce(1)-C(1) bond length. The Ce(1)-I(1) bond length is 3.21 Å. The Ce(1)-I(2) bond length is 3.21 Å. The Ce(1)-I(3) bond length is 3.35 Å. There is one shorter (3.24 Å) and one longer (3.50 Å) Ce(1)-I(4) bond length. In the second Ce site, Ce(2) is bonded to one C(1), one I(1), one I(4), one I(5), and two equivalent I(3) atoms to form distorted CeCI5 octahedra that share  a cornercorner with one Ce(1)C2I5 pentagonal bipyramid,  an edgeedge with one Ce(2)CI5 octahedra, edges with three equivalent Ce(1)C2I5 pentagonal bipyramids, and edges with three equivalent Ce(3)C2I5 pentagonal bipyramids. The Ce(2)-C(1) bond length is 2.36 Å. The Ce(2)-I(1) bond length is 3.39 Å. The Ce(2)-I(4) bond length is 3.19 Å. The Ce(2)-I(5) bond length is 3.11 Å. There is one shorter (3.28 Å) and one longer (3.30 Å) Ce(2)-I(3) bond length. In the third Ce site, Ce(3) is bonded to two equivalent C(1), one I(1), one I(3), one I(5), and two equivalent I(2) atoms to form distorted CeC2I5 pentagonal bipyramids that share corners with two equivalent Ce(1)C2I5 pentagonal bipyramids, edges with three equivalent Ce(2)CI5 octahedra, edges with two equivalent Ce(3)C2I5 pentagonal bipyramids, and faces with two equivalent Ce(1)C2I5 pentagonal bipyramids. There is one shorter (2.65 Å) and one longer (2.66 Å) Ce(3)-C(1) bond length. The Ce(3)-I(1) bond length is 3.21 Å. The Ce(3)-I(3) bond length is 3.39 Å. The Ce(3)-I(5) bond length is 3.17 Å. There is one shorter (3.20 Å) and one longer (3.51 Å) Ce(3)-I(2) bond length. C(1) is bonded in a 6-coordinate geometry to one Ce(2), two equivalent Ce(1), two equivalent Ce(3), and one C(1) atom. The C(1)-C(1) bond length is 1.42 Å. There are five inequivalent I sites. In the first I site, I(1) is bonded in a distorted T-shaped geometry to one Ce(1), one Ce(2), and one Ce(3) atom. In the second I site, I(2) is bonded in a 3-coordinate geometry to one Ce(1) and two equivalent Ce(3) atoms. In the third I site, I(3) is bonded in a rectangular see-saw-like geometry to one Ce(1), one Ce(3), and two equivalent Ce(2) atoms. In the fourth I site, I(4) is bonded in a distorted T-shaped geometry to one Ce(2) and two equivalent Ce(1) atoms. In the fifth I site, I(5) is bonded in a distorted L-shaped geometry to one Ce(2) and one Ce(3) atom.