Thallium-Fluorides Revisited: Crystal Chemistry of TlHF 2 , Tl 2 [MF 6 ]·2TlF, and Tl 2 [MF 6 ]·TlCl (M = Si and Ge).

Although the formation of thallium hydrogen fluorides TlH x F x +1 ( x = 1, 1.5, 2, 3, 5, 6.5, and 7) from TlF and HF was reported in the 1970s, little is known about the corresponding crystal structures. To shed light on the crystal chemistry of the thallium fluorides, we reinvestigated the structure of α-TlHF 2 , which was obtained by crystallization of TlF from 50% HF at room temperature. We disclose that β-TlHF 2 is isostructural with α-MHF 2 (M = K, Rb, and Cs), γ-TlHF 2 is isostructural with β-MHF 2 (M = K and Rb), whereas α-TlHF 2 crystallizes in an unusual structure type. During the reaction of TlHF 2 with the glass of the microscope slide, crystals of the previously unknown compound Tl 2 [SiF 6 ]·2TlF were formed. We disclose that the related Tl 2 [GeF 6 ]·2TlF can be obtained by the crystallization of stoichiometric amounts of Tl 2 [GeF 6 ] with TlF from water at room temperature. The crystal structures of α-TlHF 2 , Tl 2 [SiF 6 ]·2TlF, Tl 2 [SiF 6 ]·TlCl, Tl 2 [GeF 6 ]·2TlF, Tl 2 [GeF 6 ]·TlCl, and Tl 2 [GeF 6 ] were determined by single-crystal X-ray diffraction analysis. The crystal structures of α-TlF and Tl 2 [SiF 6 ]· x TlF ( x = 0, 1) were redetermined at low temperatures.