Nb12TlTe16 crystallizes in the monoclinic Cm space group. There are nine inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one Te(5), one Te(9), two equivalent Te(10), and two equivalent Te(3) atoms. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one Te(4), one Te(8), two equivalent Te(10), and two equivalent Te(3) atoms. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one Te(5), one Te(7), two equivalent Te(11), and two equivalent Te(3) atoms. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one Te(4), one Te(6), two equivalent Te(11), and two equivalent Te(3) atoms. In the fifth Nb site, Nb(5) is bonded in a 6-coordinate geometry to one Te(7), one Te(9), two equivalent Te(12), and two equivalent Te(3) atoms. In the sixth Nb site, Nb(6) is bonded in a 6-coordinate geometry to one Te(6), one Te(8), two equivalent Te(12), and two equivalent Te(3) atoms. In the seventh Nb site, Nb(7) is bonded in a 6-coordinate geometry to one Te(1), one Te(10), one Te(12), one Te(2), one Te(4), and one Te(5) atom. In the eighth Nb site, Nb(8) is bonded in a 6-coordinate geometry to one Te(1), one Te(10), one Te(11), one Te(2), one Te(6), and one Te(7) atom. In the ninth Nb site, Nb(9) is bonded in a 6-coordinate geometry to one Te(1), one Te(11), one Te(12), one Te(2), one Te(8), and one Te(9) atom. Tl(1) is bonded in a trigonal planar geometry to one Te(5), one Te(7), and one Te(8) atom. There are twelve inequivalent Te sites. In the first Te site, Te(1) is bonded to two equivalent Nb(7), two equivalent Nb(8), and two equivalent Nb(9) atoms to form distorted face-sharing TeNb6 pentagonal pyramids. In the second Te site, Te(2) is bonded to two equivalent Nb(7), two equivalent Nb(8), and two equivalent Nb(9) atoms to form distorted face-sharing TeNb6 pentagonal pyramids. In the third Te site, Te(3) is bonded to one Nb(1), one Nb(2), one Nb(3), one Nb(4), one Nb(5), and one Nb(6) atom to form distorted face-sharing TeNb6 pentagonal pyramids. In the fourth Te site, Te(4) is bonded in a 4-coordinate geometry to one Nb(2), one Nb(4), and two equivalent Nb(7) atoms. In the fifth Te site, Te(5) is bonded in a 5-coordinate geometry to one Nb(1), one Nb(3), two equivalent Nb(7), and one Tl(1) atom. In the sixth Te site, Te(6) is bonded in a 4-coordinate geometry to one Nb(4), one Nb(6), and two equivalent Nb(8) atoms. In the seventh Te site, Te(7) is bonded in a 5-coordinate geometry to one Nb(3), one Nb(5), two equivalent Nb(8), and one Tl(1) atom. In the eighth Te site, Te(8) is bonded in a 5-coordinate geometry to one Nb(2), one Nb(6), two equivalent Nb(9), and one Tl(1) atom. In the ninth Te site, Te(9) is bonded in a 4-coordinate geometry to one Nb(1), one Nb(5), and two equivalent Nb(9) atoms. In the tenth Te site, Te(10) is bonded in a 4-coordinate geometry to one Nb(1), one Nb(2), one Nb(7), and one Nb(8) atom. In the eleventh Te site, Te(11) is bonded in a 4-coordinate geometry to one Nb(3), one Nb(4), one Nb(8), and one Nb(9) atom. In the twelfth Te site, Te(12) is bonded in a 4-coordinate geometry to one Nb(5), one Nb(6), one Nb(7), and one Nb(9) atom.
Nb12TlTe16 crystallizes in the monoclinic Cm space group. There are nine inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one Te(5), one Te(9), two equivalent Te(10), and two equivalent Te(3) atoms. The Nb(1)-Te(5) bond length is 2.78 Å. The Nb(1)-Te(9) bond length is 3.01 Å. Both Nb(1)-Te(10) bond lengths are 2.80 Å. Both Nb(1)-Te(3) bond lengths are 2.94 Å. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one Te(4), one Te(8), two equivalent Te(10), and two equivalent Te(3) atoms. The Nb(2)-Te(4) bond length is 2.79 Å. The Nb(2)-Te(8) bond length is 3.07 Å. Both Nb(2)-Te(10) bond lengths are 2.81 Å. Both Nb(2)-Te(3) bond lengths are 2.94 Å. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one Te(5), one Te(7), two equivalent Te(11), and two equivalent Te(3) atoms. The Nb(3)-Te(5) bond length is 3.05 Å. The Nb(3)-Te(7) bond length is 2.79 Å. Both Nb(3)-Te(11) bond lengths are 2.80 Å. Both Nb(3)-Te(3) bond lengths are 2.94 Å. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one Te(4), one Te(6), two equivalent Te(11), and two equivalent Te(3) atoms. The Nb(4)-Te(4) bond length is 3.03 Å. The Nb(4)-Te(6) bond length is 2.79 Å. Both Nb(4)-Te(11) bond lengths are 2.80 Å. Both Nb(4)-Te(3) bond lengths are 2.93 Å. In the fifth Nb site, Nb(5) is bonded in a 6-coordinate geometry to one Te(7), one Te(9), two equivalent Te(12), and two equivalent Te(3) atoms. The Nb(5)-Te(7) bond length is 3.05 Å. The Nb(5)-Te(9) bond length is 2.80 Å. Both Nb(5)-Te(12) bond lengths are 2.81 Å. Both Nb(5)-Te(3) bond lengths are 2.94 Å. In the sixth Nb site, Nb(6) is bonded in a 6-coordinate geometry to one Te(6), one Te(8), two equivalent Te(12), and two equivalent Te(3) atoms. The Nb(6)-Te(6) bond length is 3.02 Å. The Nb(6)-Te(8) bond length is 2.78 Å. Both Nb(6)-Te(12) bond lengths are 2.79 Å. Both Nb(6)-Te(3) bond lengths are 2.94 Å. In the seventh Nb site, Nb(7) is bonded in a 6-coordinate geometry to one Te(1), one Te(10), one Te(12), one Te(2), one Te(4), and one Te(5) atom. The Nb(7)-Te(1) bond length is 2.92 Å. The Nb(7)-Te(10) bond length is 2.80 Å. The Nb(7)-Te(12) bond length is 3.07 Å. The Nb(7)-Te(2) bond length is 2.95 Å. The Nb(7)-Te(4) bond length is 2.79 Å. The Nb(7)-Te(5) bond length is 2.81 Å. In the eighth Nb site, Nb(8) is bonded in a 6-coordinate geometry to one Te(1), one Te(10), one Te(11), one Te(2), one Te(6), and one Te(7) atom. The Nb(8)-Te(1) bond length is 2.93 Å. The Nb(8)-Te(10) bond length is 3.07 Å. The Nb(8)-Te(11) bond length is 2.80 Å. The Nb(8)-Te(2) bond length is 2.93 Å. The Nb(8)-Te(6) bond length is 2.80 Å. The Nb(8)-Te(7) bond length is 2.79 Å. In the ninth Nb site, Nb(9) is bonded in a 6-coordinate geometry to one Te(1), one Te(11), one Te(12), one Te(2), one Te(8), and one Te(9) atom. The Nb(9)-Te(1) bond length is 2.95 Å. The Nb(9)-Te(11) bond length is 3.07 Å. The Nb(9)-Te(12) bond length is 2.80 Å. The Nb(9)-Te(2) bond length is 2.92 Å. The Nb(9)-Te(8) bond length is 2.80 Å. The Nb(9)-Te(9) bond length is 2.79 Å. Tl(1) is bonded in a trigonal planar geometry to one Te(5), one Te(7), and one Te(8) atom. The Tl(1)-Te(5) bond length is 3.42 Å. The Tl(1)-Te(7) bond length is 3.41 Å. The Tl(1)-Te(8) bond length is 3.41 Å. There are twelve inequivalent Te sites. In the first Te site, Te(1) is bonded to two equivalent Nb(7), two equivalent Nb(8), and two equivalent Nb(9) atoms to form distorted face-sharing TeNb6 pentagonal pyramids. In the second Te site, Te(2) is bonded to two equivalent Nb(7), two equivalent Nb(8), and two equivalent Nb(9) atoms to form distorted face-sharing TeNb6 pentagonal pyramids. In the third Te site, Te(3) is bonded to one Nb(1), one Nb(2), one Nb(3), one Nb(4), one Nb(5), and one Nb(6) atom to form distorted face-sharing TeNb6 pentagonal pyramids. In the fourth Te site, Te(4) is bonded in a 4-coordinate geometry to one Nb(2), one Nb(4), and two equivalent Nb(7) atoms. In the fifth Te site, Te(5) is bonded in a 5-coordinate geometry to one Nb(1), one Nb(3), two equivalent Nb(7), and one Tl(1) atom. In the sixth Te site, Te(6) is bonded in a 4-coordinate geometry to one Nb(4), one Nb(6), and two equivalent Nb(8) atoms. In the seventh Te site, Te(7) is bonded in a 5-coordinate geometry to one Nb(3), one Nb(5), two equivalent Nb(8), and one Tl(1) atom. In the eighth Te site, Te(8) is bonded in a 5-coordinate geometry to one Nb(2), one Nb(6), two equivalent Nb(9), and one Tl(1) atom. In the ninth Te site, Te(9) is bonded in a 4-coordinate geometry to one Nb(1), one Nb(5), and two equivalent Nb(9) atoms. In the tenth Te site, Te(10) is bonded in a 4-coordinate geometry to one Nb(1), one Nb(2), one Nb(7), and one Nb(8) atom. In the eleventh Te site, Te(11) is bonded in a 4-coordinate geometry to one Nb(3), one Nb(4), one Nb(8), and one Nb(9) atom. In the twelfth Te site, Te(12) is bonded in a 4-coordinate geometry to one Nb(5), one Nb(6), one Nb(7), and one Nb(9) atom.