Kaskel, Stefan Dong, Zhen-Chao Klem, Michael T. Corbett, John D. Synthesis and Structure of the Metallic K<sub>6</sub>Tl<sub>17</sub>:  A Layered Tetrahedral Star Structure Related to That of Cr<sub>3</sub>Si The title compound, the Tl-richest in the K−Tl system, has been synthesized in Ta containers via direct reaction of the elements at 400 °C followed by quenching to room temperature and subsequent annealing at 150 °C for 4 weeks. It crystallizes in the orthorhombic space group <i>Cccm</i> (No. 66) with <i>a</i> = 16.625(1) Å, <i>b</i> = 23.594(2) Å, <i>c</i> = 15.369(2) Å (22 °C), and <i>Z</i> = 8. Two different Tl<sub>12</sub> units consisting of augmented tetrahedral stars are condensed into layers of such tetrahedra, and further Tl<sub>2</sub> dumbbells and the potassium cations also interconnect the stars and layers into a three-dimensional network. The former anionic Tl<sub>8</sub> subunits clearly resemble those in the heteroatomic 3-D structure of cubic Cr<sub>3</sub>Si before their augmentation with bridging atoms. The compound is metallic (ρ<sub>270</sub> = 22.6 μΩ·cm, α = 0.0023 K<sup>-1</sup>) and shows Pauli-like paramagnetic susceptibility (χ<sub>296</sub> = 1.1 × 10<sup>-4</sup> emu/mol). EHTB calculations illustrate the importance of Tl p-orbital bonding, the positive Tl−Tl overlap populations up to <i>E</i><sub>F</sub>, and greater strengths of the Tl−Tl bonding between and about the surface of the augmented Tl<sub>12</sub> units. Cations between the thallium layers play specific and important roles in the structure. Tl 12 units;tetrahedral stars;title compound;Tl 8 subunits;Ta containers;space group Cccm;Tl 2 dumbbells;4 weeks;Layered Tetrahedral Star Structure Related;0.0023 K;E F;EHTB;potassium cations;Cr 3 Si;thallium layers;room temperature 2003-02-14
    https://acs.figshare.com/articles/journal_contribution/Synthesis_and_Structure_of_the_Metallic_K_sub_6_sub_Tl_sub_17_sub_A_Layered_Tetrahedral_Star_Structure_Related_to_That_of_Cr_sub_3_sub_Si/3606897
10.1021/ic020667h.s001