Thallium-Fluorides\nRevisited: Crystal Chemistry of\nTlHF<sub>2</sub>, Tl<sub>2</sub>[MF<sub>6</sub>]·2TlF, and Tl<sub>2</sub>[MF<sub>6</sub>]·TlCl (M = Si and Ge)

Although the formation of thallium hydrogen fluorides\nTlH<sub><i>x</i></sub>F<sub><i>x</i>+1</sub> (<i>x</i> = 1, 1.5, 2, 3, 5, 6.5, and 7) from TlF and HF was reported\nin the\n1970s, little is known about the corresponding crystal structures.\nTo shed light on the crystal chemistry of the thallium fluorides,\nwe reinvestigated the structure of α-TlHF<sub>2</sub>, which\nwas obtained by crystallization of TlF from 50% HF at room temperature.\nWe disclose that β-TlHF<sub>2</sub> is isostructural with α-MHF<sub>2</sub> (M = K, Rb, and Cs), γ-TlHF<sub>2</sub> is isostructural\nwith β-MHF<sub>2</sub> (M = K and Rb), whereas α-TlHF<sub>2</sub> crystallizes in an unusual structure type. During the reaction\nof TlHF<sub>2</sub> with the glass of the microscope slide, crystals\nof the previously unknown compound Tl<sub>2</sub>[SiF<sub>6</sub>]·2TlF\nwere formed. We disclose that the related Tl<sub>2</sub>[GeF<sub>6</sub>]·2TlF can be obtained by the crystallization of stoichiometric\namounts of Tl<sub>2</sub>[GeF<sub>6</sub>] with TlF from water at\nroom temperature. The crystal structures of α-TlHF<sub>2</sub>, Tl<sub>2</sub>[SiF<sub>6</sub>]·2TlF, Tl<sub>2</sub>[SiF<sub>6</sub>]·TlCl, Tl<sub>2</sub>[GeF<sub>6</sub>]·2TlF, Tl<sub>2</sub>[GeF<sub>6</sub>]·TlCl, and Tl<sub>2</sub>[GeF<sub>6</sub>] were determined by single-crystal X-ray diffraction analysis. The\ncrystal structures of α-TlF and Tl<sub>2</sub>[SiF<sub>6</sub>]·<i>x</i>TlF (<i>x</i> = 0, 1) were redetermined\nat low temperatures.