La3CI5 crystallizes in the triclinic P-1 space group. There are three inequivalent La sites. In the first La site, La(1) is bonded to one C(1), one I(1), one I(3), one I(4), and two equivalent I(5) atoms to form distorted LaCI5 octahedra that share  a cornercorner with one La(3)C2I5 pentagonal bipyramid,  an edgeedge with one La(1)CI5 octahedra, edges with three equivalent La(2)C2I5 pentagonal bipyramids, and edges with three equivalent La(3)C2I5 pentagonal bipyramids. In the second La site, La(2) is bonded to two equivalent C(1), one I(1), one I(4), one I(5), and two equivalent I(2) atoms to form distorted LaC2I5 pentagonal bipyramids that share corners with two equivalent La(3)C2I5 pentagonal bipyramids, edges with three equivalent La(1)CI5 octahedra, edges with two equivalent La(2)C2I5 pentagonal bipyramids, and faces with two equivalent La(3)C2I5 pentagonal bipyramids. In the third La site, La(3) is bonded to two equivalent C(1), one I(1), one I(2), one I(5), and two equivalent I(3) atoms to form distorted LaC2I5 pentagonal bipyramids that share  a cornercorner with one La(1)CI5 octahedra, corners with two equivalent La(2)C2I5 pentagonal bipyramids, edges with three equivalent La(1)CI5 octahedra, edges with two equivalent La(3)C2I5 pentagonal bipyramids, and faces with two equivalent La(2)C2I5 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 4°. C(1) is bonded in a 6-coordinate geometry to one La(1), two equivalent La(2), two equivalent La(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 La(1), one La(2), and one La(3) atom. In the second I site, I(2) is bonded in a distorted T-shaped geometry to one La(3) and two equivalent La(2) atoms. In the third I site, I(3) is bonded in a distorted T-shaped geometry to one La(1) and two equivalent La(3) atoms. In the fourth I site, I(4) is bonded in a distorted L-shaped geometry to one La(1) and one La(2) atom. In the fifth I site, I(5) is bonded in a rectangular see-saw-like geometry to one La(2), one La(3), and two equivalent La(1) atoms.
La3CI5 crystallizes in the triclinic P-1 space group. There are three inequivalent La sites. In the first La site, La(1) is bonded to one C(1), one I(1), one I(3), one I(4), and two equivalent I(5) atoms to form distorted LaCI5 octahedra that share  a cornercorner with one La(3)C2I5 pentagonal bipyramid,  an edgeedge with one La(1)CI5 octahedra, edges with three equivalent La(2)C2I5 pentagonal bipyramids, and edges with three equivalent La(3)C2I5 pentagonal bipyramids. The La(1)-C(1) bond length is 2.37 Å. The La(1)-I(1) bond length is 3.45 Å. The La(1)-I(3) bond length is 3.21 Å. The La(1)-I(4) bond length is 3.14 Å. There is one shorter (3.32 Å) and one longer (3.35 Å) La(1)-I(5) bond length. In the second La site, La(2) is bonded to two equivalent C(1), one I(1), one I(4), one I(5), and two equivalent I(2) atoms to form distorted LaC2I5 pentagonal bipyramids that share corners with two equivalent La(3)C2I5 pentagonal bipyramids, edges with three equivalent La(1)CI5 octahedra, edges with two equivalent La(2)C2I5 pentagonal bipyramids, and faces with two equivalent La(3)C2I5 pentagonal bipyramids. There is one shorter (2.70 Å) and one longer (2.73 Å) La(2)-C(1) bond length. The La(2)-I(1) bond length is 3.21 Å. The La(2)-I(4) bond length is 3.19 Å. The La(2)-I(5) bond length is 3.41 Å. There is one shorter (3.21 Å) and one longer (3.51 Å) La(2)-I(2) bond length. In the third La site, La(3) is bonded to two equivalent C(1), one I(1), one I(2), one I(5), and two equivalent I(3) atoms to form distorted LaC2I5 pentagonal bipyramids that share  a cornercorner with one La(1)CI5 octahedra, corners with two equivalent La(2)C2I5 pentagonal bipyramids, edges with three equivalent La(1)CI5 octahedra, edges with two equivalent La(3)C2I5 pentagonal bipyramids, and faces with two equivalent La(2)C2I5 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 4°. There is one shorter (2.69 Å) and one longer (2.71 Å) La(3)-C(1) bond length. The La(3)-I(1) bond length is 3.21 Å. The La(3)-I(2) bond length is 3.20 Å. The La(3)-I(5) bond length is 3.37 Å. There is one shorter (3.25 Å) and one longer (3.52 Å) La(3)-I(3) bond length. C(1) is bonded in a 6-coordinate geometry to one La(1), two equivalent La(2), two equivalent La(3), and one C(1) atom. The C(1)-C(1) bond length is 1.41 Å. There are five inequivalent I sites. In the first I site, I(1) is bonded in a distorted T-shaped geometry to one La(1), one La(2), and one La(3) atom. In the second I site, I(2) is bonded in a distorted T-shaped geometry to one La(3) and two equivalent La(2) atoms. In the third I site, I(3) is bonded in a distorted T-shaped geometry to one La(1) and two equivalent La(3) atoms. In the fourth I site, I(4) is bonded in a distorted L-shaped geometry to one La(1) and one La(2) atom. In the fifth I site, I(5) is bonded in a rectangular see-saw-like geometry to one La(2), one La(3), and two equivalent La(1) atoms.