Nb6TlSe8 crystallizes in the trigonal P-3 space group. Nb(1) is bonded in a 6-coordinate geometry to two equivalent Se(2) and four equivalent Se(1) atoms. Tl(1) is bonded in a 6-coordinate geometry to six equivalent Se(1) atoms. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded to six equivalent Nb(1) atoms to form distorted face-sharing SeNb6 pentagonal pyramids. In the second Se site, Se(1) is bonded in a 5-coordinate geometry to four equivalent Nb(1) and one Tl(1) atom.
Nb6TlSe8 crystallizes in the trigonal P-3 space group. Nb(1) is bonded in a 6-coordinate geometry to two equivalent Se(2) and four equivalent Se(1) atoms. There is one shorter (2.75 Å) and one longer (2.76 Å) Nb(1)-Se(2) bond length. There are a spread of Nb(1)-Se(1) bond distances ranging from 2.60-2.86 Å. Tl(1) is bonded in a 6-coordinate geometry to six equivalent Se(1) atoms. All Tl(1)-Se(1) bond lengths are 3.34 Å. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded to six equivalent Nb(1) atoms to form distorted face-sharing SeNb6 pentagonal pyramids. In the second Se site, Se(1) is bonded in a 5-coordinate geometry to four equivalent Nb(1) and one Tl(1) atom.