CsNb6I11 crystallizes in the hexagonal P6_322 space group. Cs(1) is bonded to six equivalent I(1) and six equivalent I(2) atoms to form CsI12 cuboctahedra that share corners with twelve equivalent Nb(1)I5 square pyramids, faces with two equivalent Cs(1)I12 cuboctahedra, and faces with six equivalent Nb(1)I5 square pyramids. Nb(1) is bonded to one I(2), one I(3), and three equivalent I(1) atoms to form distorted NbI5 square pyramids that share corners with two equivalent Cs(1)I12 cuboctahedra,  a cornercorner with one Nb(1)I5 square pyramid, edges with four equivalent Nb(1)I5 square pyramids, and  a faceface with one Cs(1)I12 cuboctahedra. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 4-coordinate geometry to one Cs(1) and three equivalent Nb(1) atoms. In the second I site, I(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Cs(1) and two equivalent Nb(1) atoms. In the third I site, I(3) is bonded in a 3-coordinate geometry to three equivalent Nb(1) atoms.
CsNb6I11 crystallizes in the hexagonal P6_322 space group. Cs(1) is bonded to six equivalent I(1) and six equivalent I(2) atoms to form CsI12 cuboctahedra that share corners with twelve equivalent Nb(1)I5 square pyramids, faces with two equivalent Cs(1)I12 cuboctahedra, and faces with six equivalent Nb(1)I5 square pyramids. All Cs(1)-I(1) bond lengths are 4.26 Å. All Cs(1)-I(2) bond lengths are 4.42 Å. Nb(1) is bonded to one I(2), one I(3), and three equivalent I(1) atoms to form distorted NbI5 square pyramids that share corners with two equivalent Cs(1)I12 cuboctahedra,  a cornercorner with one Nb(1)I5 square pyramid, edges with four equivalent Nb(1)I5 square pyramids, and  a faceface with one Cs(1)I12 cuboctahedra. The Nb(1)-I(2) bond length is 3.07 Å. The Nb(1)-I(3) bond length is 2.87 Å. There are a spread of Nb(1)-I(1) bond distances ranging from 2.89-2.94 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 4-coordinate geometry to one Cs(1) and three equivalent Nb(1) atoms. In the second I site, I(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Cs(1) and two equivalent Nb(1) atoms. In the third I site, I(3) is bonded in a 3-coordinate geometry to three equivalent Nb(1) atoms.