Cs3Fe2Cl9 crystallizes in the trigonal P-3m1 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 nine equivalent Cs(1)Cl12 cuboctahedra, faces with three equivalent Cs(1)Cl12 cuboctahedra, faces with three equivalent Cs(2)Cl12 cuboctahedra, and faces with five equivalent Fe(1)Cl6 octahedra. 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 Fe(1)Cl6 octahedra, faces with three equivalent Cs(2)Cl12 cuboctahedra, and faces with five equivalent Cs(1)Cl12 cuboctahedra. The corner-sharing octahedra are not tilted. 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 to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Fe(1) atoms to form a mixture of distorted face and corner-sharing ClCs4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°.
Cs3Fe2Cl9 crystallizes in the trigonal P-3m1 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 nine equivalent Cs(1)Cl12 cuboctahedra, faces with three equivalent Cs(1)Cl12 cuboctahedra, faces with three equivalent Cs(2)Cl12 cuboctahedra, and faces with five equivalent Fe(1)Cl6 octahedra. All Cs(1)-Cl(2) bond lengths are 3.65 Å. There are six shorter (3.69 Å) and three longer (3.74 Å) Cs(1)-Cl(1) bond lengths. 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 3.63 Å. All Cs(2)-Cl(2) bond lengths are 3.68 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 Fe(1)Cl6 octahedra, faces with three equivalent Cs(2)Cl12 cuboctahedra, and faces with five equivalent Cs(1)Cl12 cuboctahedra. The corner-sharing octahedra are not tilted. All Fe(1)-Cl(1) bond lengths are 2.29 Å. All Fe(1)-Cl(2) bond lengths are 2.70 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 to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Fe(1) atoms to form a mixture of distorted face and corner-sharing ClCs4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°.