Cs2PbTa6Cl18 crystallizes in the trigonal R-3 space group. Cs(1) is bonded to three equivalent Cl(1), three equivalent Cl(2), and six equivalent Cl(3) atoms to form CsCl12 cuboctahedra that share corners with three equivalent Pb(1)Cl6 octahedra, corners with six equivalent Ta(1)Cl5 square pyramids, edges with three equivalent Cs(1)Cl12 cuboctahedra, edges with three equivalent Ta(1)Cl5 square pyramids, and faces with three equivalent Ta(1)Cl5 square pyramids. The corner-sharing octahedral tilt angles are 56°. Ta(1) is bonded to one Cl(2), two equivalent Cl(1), and two equivalent Cl(3) atoms to form distorted TaCl5 square pyramids that share corners with two equivalent Cs(1)Cl12 cuboctahedra,  a cornercorner with one Pb(1)Cl6 octahedra, corners with four equivalent Ta(1)Cl5 square pyramids,  an edgeedge with one Cs(1)Cl12 cuboctahedra, and  a faceface with one Cs(1)Cl12 cuboctahedra. The corner-sharing octahedral tilt angles are 44°. Pb(1) is bonded to six equivalent Cl(2) atoms to form PbCl6 octahedra that share corners with six equivalent Cs(1)Cl12 cuboctahedra and corners with six equivalent Ta(1)Cl5 square pyramids. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a 2-coordinate geometry to one Cs(1) and two equivalent Ta(1) atoms. In the second Cl site, Cl(2) is bonded in a 3-coordinate geometry to one Cs(1), one Ta(1), and one Pb(1) atom. In the third Cl site, Cl(3) is bonded in a 2-coordinate geometry to two equivalent Cs(1) and two equivalent Ta(1) atoms.
Cs2PbTa6Cl18 crystallizes in the trigonal R-3 space group. Cs(1) is bonded to three equivalent Cl(1), three equivalent Cl(2), and six equivalent Cl(3) atoms to form CsCl12 cuboctahedra that share corners with three equivalent Pb(1)Cl6 octahedra, corners with six equivalent Ta(1)Cl5 square pyramids, edges with three equivalent Cs(1)Cl12 cuboctahedra, edges with three equivalent Ta(1)Cl5 square pyramids, and faces with three equivalent Ta(1)Cl5 square pyramids. The corner-sharing octahedral tilt angles are 56°. All Cs(1)-Cl(1) bond lengths are 3.72 Å. All Cs(1)-Cl(2) bond lengths are 3.59 Å. There are three shorter (3.73 Å) and three longer (3.78 Å) Cs(1)-Cl(3) bond lengths. Ta(1) is bonded to one Cl(2), two equivalent Cl(1), and two equivalent Cl(3) atoms to form distorted TaCl5 square pyramids that share corners with two equivalent Cs(1)Cl12 cuboctahedra,  a cornercorner with one Pb(1)Cl6 octahedra, corners with four equivalent Ta(1)Cl5 square pyramids,  an edgeedge with one Cs(1)Cl12 cuboctahedra, and  a faceface with one Cs(1)Cl12 cuboctahedra. The corner-sharing octahedral tilt angles are 44°. The Ta(1)-Cl(2) bond length is 2.65 Å. Both Ta(1)-Cl(1) bond lengths are 2.47 Å. There is one shorter (2.48 Å) and one longer (2.49 Å) Ta(1)-Cl(3) bond length. Pb(1) is bonded to six equivalent Cl(2) atoms to form PbCl6 octahedra that share corners with six equivalent Cs(1)Cl12 cuboctahedra and corners with six equivalent Ta(1)Cl5 square pyramids. All Pb(1)-Cl(2) bond lengths are 2.97 Å. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a 2-coordinate geometry to one Cs(1) and two equivalent Ta(1) atoms. In the second Cl site, Cl(2) is bonded in a 3-coordinate geometry to one Cs(1), one Ta(1), and one Pb(1) atom. In the third Cl site, Cl(3) is bonded in a 2-coordinate geometry to two equivalent Cs(1) and two equivalent Ta(1) atoms.