CsTaI6 crystallizes in the monoclinic C2/c space group. Cs(1) is bonded to four equivalent I(1), four equivalent I(2), and four equivalent I(3) atoms to form CsI12 cuboctahedra that share corners with four equivalent Cs(1)I12 cuboctahedra, corners with two equivalent Ta(1)I6 octahedra, edges with four equivalent Cs(1)I12 cuboctahedra, edges with two equivalent Ta(1)I6 octahedra, and faces with two equivalent Ta(1)I6 octahedra. The corner-sharing octahedral tilt angles are 46°. Ta(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form TaI6 octahedra that share corners with two equivalent Cs(1)I12 cuboctahedra, edges with two equivalent Cs(1)I12 cuboctahedra, and faces with two equivalent Cs(1)I12 cuboctahedra. There are three inequivalent I sites. In the first I site, I(1) is bonded in a distorted single-bond geometry to two equivalent Cs(1) and one Ta(1) atom. In the second I site, I(2) is bonded in a distorted single-bond geometry to two equivalent Cs(1) and one Ta(1) atom. In the third I site, I(3) is bonded in a distorted single-bond geometry to two equivalent Cs(1) and one Ta(1) atom.
CsTaI6 crystallizes in the monoclinic C2/c space group. Cs(1) is bonded to four equivalent I(1), four equivalent I(2), and four equivalent I(3) atoms to form CsI12 cuboctahedra that share corners with four equivalent Cs(1)I12 cuboctahedra, corners with two equivalent Ta(1)I6 octahedra, edges with four equivalent Cs(1)I12 cuboctahedra, edges with two equivalent Ta(1)I6 octahedra, and faces with two equivalent Ta(1)I6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are two shorter (4.11 Å) and two longer (4.30 Å) Cs(1)-I(1) bond lengths. All Cs(1)-I(2) bond lengths are 4.11 Å. There are two shorter (4.13 Å) and two longer (4.15 Å) Cs(1)-I(3) bond lengths. Ta(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form TaI6 octahedra that share corners with two equivalent Cs(1)I12 cuboctahedra, edges with two equivalent Cs(1)I12 cuboctahedra, and faces with two equivalent Cs(1)I12 cuboctahedra. Both Ta(1)-I(1) bond lengths are 2.77 Å. Both Ta(1)-I(2) bond lengths are 2.77 Å. Both Ta(1)-I(3) bond lengths are 2.75 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded in a distorted single-bond geometry to two equivalent Cs(1) and one Ta(1) atom. In the second I site, I(2) is bonded in a distorted single-bond geometry to two equivalent Cs(1) and one Ta(1) atom. In the third I site, I(3) is bonded in a distorted single-bond geometry to two equivalent Cs(1) and one Ta(1) atom.