Thallium-Fluorides Revisited: Crystal Chemistry of TlHF2, Tl2[MF6]·2TlF, and Tl2[MF6]·TlCl (M = Si and Ge).

Abstract

Although the formation of thallium hydrogen fluorides TlHxFx+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-TlHF2, which was obtained by crystallization of TlF from 50% HF at room temperature. We disclose that β-TlHF2 is isostructural with α-MHF2 (M = K, Rb, and Cs), γ-TlHF2 is isostructural with β-MHF2 (M = K and Rb), whereas α-TlHF2 crystallizes in an unusual structure type. During the reaction of TlHF2 with the glass of the microscope slide, crystals of the previously unknown compound Tl2[SiF6]·2TlF were formed. We disclose that the related Tl2[GeF6]·2TlF can be obtained by the crystallization of stoichiometric amounts of Tl2[GeF6] with TlF from water at room temperature. The crystal structures of α-TlHF2, Tl2[SiF6]·2TlF, Tl2[SiF6]·TlCl, Tl2[GeF6]·2TlF, Tl2[GeF6]·TlCl, and Tl2[GeF6] were determined by single-crystal X-ray diffraction analysis. The crystal structures of α-TlF and Tl2[SiF6]·xTlF (x = 0, 1) were redetermined at low temperatures.