Cs3Fe2Cl9 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to three equivalent Cl(2) and nine equivalent Cl(1) atoms to form CsCl12 cuboctahedra that share corners with three equivalent Cs(2)Cl12 cuboctahedra, corners with six equivalent Cs(1)Cl12 cuboctahedra, corners with three equivalent Fe(1)Cl6 octahedra, faces with three equivalent Cs(2)Cl12 cuboctahedra, faces with four equivalent Cs(1)Cl12 cuboctahedra, and faces with four equivalent Fe(1)Cl6 octahedra. The corner-sharing octahedral tilt angles are 9°. In the second Cs site, Cs(2) is bonded to six equivalent Cl(1) and six equivalent Cl(2) atoms to form CsCl12 cuboctahedra that share corners with six equivalent Cs(1)Cl12 cuboctahedra, corners with six equivalent Cs(2)Cl12 cuboctahedra, faces with six equivalent Cs(1)Cl12 cuboctahedra, and faces with six equivalent Fe(1)Cl6 octahedra. Fe(1) is bonded to three equivalent Cl(1) and three equivalent Cl(2) atoms to form FeCl6 octahedra that share corners with three equivalent Cs(1)Cl12 cuboctahedra, faces with three equivalent Cs(2)Cl12 cuboctahedra, faces with four equivalent Cs(1)Cl12 cuboctahedra, and  a faceface with one Fe(1)Cl6 octahedra. There are two inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a distorted single-bond geometry to one Cs(2), three equivalent Cs(1), and one Fe(1) atom. In the second Cl site, Cl(2) is bonded in a distorted L-shaped geometry to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Fe(1) atoms.
Cs3Fe2Cl9 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to three equivalent Cl(2) and nine equivalent Cl(1) atoms to form CsCl12 cuboctahedra that share corners with three equivalent Cs(2)Cl12 cuboctahedra, corners with six equivalent Cs(1)Cl12 cuboctahedra, corners with three equivalent Fe(1)Cl6 octahedra, faces with three equivalent Cs(2)Cl12 cuboctahedra, faces with four equivalent Cs(1)Cl12 cuboctahedra, and faces with four equivalent Fe(1)Cl6 octahedra. The corner-sharing octahedral tilt angles are 9°. All Cs(1)-Cl(2) bond lengths are 3.88 Å. All Cs(1)-Cl(1) bond lengths are 3.75 Å. In the second Cs site, Cs(2) is bonded to six equivalent Cl(1) and six equivalent Cl(2) atoms to form CsCl12 cuboctahedra that share corners with six equivalent Cs(1)Cl12 cuboctahedra, corners with six equivalent Cs(2)Cl12 cuboctahedra, faces with six equivalent Cs(1)Cl12 cuboctahedra, and faces with six equivalent Fe(1)Cl6 octahedra. All Cs(2)-Cl(1) bond lengths are 3.70 Å. All Cs(2)-Cl(2) bond lengths are 3.75 Å. Fe(1) is bonded to three equivalent Cl(1) and three equivalent Cl(2) atoms to form FeCl6 octahedra that share corners with three equivalent Cs(1)Cl12 cuboctahedra, faces with three equivalent Cs(2)Cl12 cuboctahedra, faces with four equivalent Cs(1)Cl12 cuboctahedra, and  a faceface with one Fe(1)Cl6 octahedra. All Fe(1)-Cl(1) bond lengths are 2.29 Å. All Fe(1)-Cl(2) bond lengths are 2.57 Å. There are two inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a distorted single-bond geometry to one Cs(2), three equivalent Cs(1), and one Fe(1) atom. In the second Cl site, Cl(2) is bonded in a distorted L-shaped geometry to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Fe(1) atoms.