Cs3Fe2F9 crystallizes in the hexagonal P-62c space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to six equivalent F(1) and six equivalent F(2) atoms to form distorted CsF12 cuboctahedra that share corners with six equivalent Cs(1)F12 cuboctahedra and faces with six equivalent Fe(1)F6 octahedra. In the second Cs site, Cs(2) is bonded in a 12-coordinate geometry to three equivalent F(1) and nine equivalent F(2) atoms. Fe(1) is bonded to three equivalent F(1) and three equivalent F(2) atoms to form distorted FeF6 octahedra that share faces with three equivalent Cs(1)F12 cuboctahedra and  a faceface with one Fe(1)F6 octahedra. There are two inequivalent F sites. In the first F site, F(1) is bonded in a distorted L-shaped geometry to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Fe(1) atoms. In the second F site, F(2) is bonded in a single-bond geometry to one Cs(1), three equivalent Cs(2), and one Fe(1) atom.
Cs3Fe2F9 crystallizes in the hexagonal P-62c space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to six equivalent F(1) and six equivalent F(2) atoms to form distorted CsF12 cuboctahedra that share corners with six equivalent Cs(1)F12 cuboctahedra and faces with six equivalent Fe(1)F6 octahedra. There are three shorter (3.22 Å) and three longer (3.26 Å) Cs(1)-F(1) bond lengths. All Cs(1)-F(2) bond lengths are 3.12 Å. In the second Cs site, Cs(2) is bonded in a 12-coordinate geometry to three equivalent F(1) and nine equivalent F(2) atoms. All Cs(2)-F(1) bond lengths are 3.63 Å. There are a spread of Cs(2)-F(2) bond distances ranging from 3.19-3.34 Å. Fe(1) is bonded to three equivalent F(1) and three equivalent F(2) atoms to form distorted FeF6 octahedra that share faces with three equivalent Cs(1)F12 cuboctahedra and  a faceface with one Fe(1)F6 octahedra. All Fe(1)-F(1) bond lengths are 2.08 Å. All Fe(1)-F(2) bond lengths are 1.89 Å. There are two inequivalent F sites. In the first F site, F(1) is bonded in a distorted L-shaped geometry to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Fe(1) atoms. In the second F site, F(2) is bonded in a single-bond geometry to one Cs(1), three equivalent Cs(2), and one Fe(1) atom.