Y4CI5 crystallizes in the monoclinic C2/m space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 6-coordinate geometry to one C(1), two equivalent I(1), and three equivalent I(2) atoms. In the second Y site, Y(2) is bonded in a 6-coordinate geometry to two equivalent C(1), one I(1), one I(2), and two equivalent I(3) atoms. C(1) is bonded to two equivalent Y(1) and four equivalent Y(2) atoms to form edge-sharing CY6 octahedra. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 3-coordinate geometry to one Y(2) and two equivalent Y(1) atoms. In the second I site, I(2) is bonded in a 4-coordinate geometry to one Y(2) and three equivalent Y(1) atoms. In the third I site, I(3) is bonded in a distorted rectangular see-saw-like geometry to four equivalent Y(2) atoms.
Y4CI5 crystallizes in the monoclinic C2/m space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 6-coordinate geometry to one C(1), two equivalent I(1), and three equivalent I(2) atoms. The Y(1)-C(1) bond length is 2.40 Å. Both Y(1)-I(1) bond lengths are 3.05 Å. There are two shorter (3.08 Å) and one longer (3.70 Å) Y(1)-I(2) bond length. In the second Y site, Y(2) is bonded in a 6-coordinate geometry to two equivalent C(1), one I(1), one I(2), and two equivalent I(3) atoms. Both Y(2)-C(1) bond lengths are 2.57 Å. The Y(2)-I(1) bond length is 3.11 Å. The Y(2)-I(2) bond length is 3.16 Å. Both Y(2)-I(3) bond lengths are 3.32 Å. C(1) is bonded to two equivalent Y(1) and four equivalent Y(2) atoms to form edge-sharing CY6 octahedra. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 3-coordinate geometry to one Y(2) and two equivalent Y(1) atoms. In the second I site, I(2) is bonded in a 4-coordinate geometry to one Y(2) and three equivalent Y(1) atoms. In the third I site, I(3) is bonded in a distorted rectangular see-saw-like geometry to four equivalent Y(2) atoms.