[Tl₇]^7– Clusters in Mixed Alkali Metal Thallides Cs_7.29K_5.71Tl₁₃ and Cs_3.45K_3.55Tl₇

Abstract

Investigations in the ternary system Cs−K−Tl resulted in the unexpected formation of new ternary thallides Cs 7.29 K 5.71 Tl 13 and Cs 3.45 K 3.55 Tl 7 . Single crystal X-ray structure analyses of both compounds reveal the presence of isolated Tl cluster units. Cs 7.29 K 5.71 Tl 13 crystallizes in the monoclinic space group C2/c (a = 30.7792(9) Å, b = 11.000(2) Å, c = 14.0291(4) Å, β = 112.676(4)°, Z = 4) and contains [Tl 6 ] 6− and [Tl 7 ] 7− clusters as thallium subunits. Cs 3.45 K 3.55 Tl 7 crystallizes in the tetragonal space group I4 1 /a (a = 13.6177(2) Å, c = 25.5573(8) Å, Z = 8) and contains [Tl 7 ] 7− clusters exclusively. The formation of Cs 7.29 K 5.71 Tl 13 is obtained after slow cooling in addition to that of Cs 3.45 K 3.55 Tl 7 and can be suppressed by quenching the stoichiometric mixture. First dissolution experiments in liquid ammonia suggest thallium and amide as final oxidation products. Full relativistic band structure calculations of Cs 4 K 3 Tl 7 and Cs 8 K 5 Tl 13 showed a (pseudo) band gap around E F for both compounds. * sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.3c04034.Experimental and DFT calculation details, crystallographic data, additional structure description, powder diffraction patterns, and dissolution experiment in liquid ammonia (PDF)Accession Codes CCDC 2295683 and 2296130 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk