Crystalline and Glassy Phases in the Ternary System Tl/Bi/Cl: Synthesis and Crystal Structures of the Thallium(I) Chloridobismutates(III) Tl₃BiCl₆ and TlBi₂Cl₇ 

Abstract

Abstract. Slow cooling of melts composed of TlCl and BiCl 3 allows for the isolation of the compounds Tl 3 BiCl 6 (1) and TlBi 2 Cl 7 (2). 1 is formed by sublimation at 480 °C from the black melt of 3 TlCl + 1 BiCl 3 as colourless crystals. The crystal structure determination (tetragonal, P4 2 /m) consists of nearly regular octahedral [BiCl 6 ] 3-anions and two independent Tl + cations which have coordination number 8 in form of a slightly distorted cube and 10 in form of an Edshamar polyhedron, respectively. The structure is not isotypic with the recently reported naturally occurring form of Tl 3 BiCl 6, the mineral steropesite. 2 is obtained from a dark brown melt of composition TlCl + 2 BiCl 3 . On rapid cooling, this melt solidifies to a metastable dark red glass which at ambient temperature crystallizes to a light amber crystalline powder within some weeks. The structure of 2 was determined by powder diffraction (triclinic, P 1 ). A distinct lone pair effect is present causing an irregular coordination on the two independent Bi atoms. Taking Bi-Cl bonds up to 3.5 Å into account, both Bi atoms gain coordination number seven. 203 Tl and 205 Tl solid state NMR and XANES spectra on the Bi and Tl-L III edges of both glassy and crystalline TlBi 2 Cl 7 show that a close structural similarity exists between both forms. In contrast, the Raman spectra show distinct differences in the bands of the Bi-Cl vibrations region.

The Polymorphic Nature of M3BiBr6 Halides (M=Cs, Rb) and their Reversible Intercalation with Water to Isomorphous Hydrates at Room Temperature

“…Beck et al. described a phase transition of the isostructural thallium compound tP ‐Tl 3 BiCl 6 at 189 °C into a monoclinic phase similar to mC ‐Cs 3 BiBr 6 before it melts at 378 °C [22] . Yet, samples of the mixture tP / oP ‐Cs 3 BiBr 6 showed no DSC signals that would indicate such a phase transition.…”

“…4.435 tP-Cs 3 BiBr 6 at 296 K (Tl 3 BiCl 6 type [22] ) types of alternating layers but differ in stacking sequence (Figure 3). Their asymmetric units, including the displacement parameters of the atoms, are very similar (Figures S9 and S10).…”

“…mC-Cs 3 BiBr 6 • 1 = 2 H 2 O at 296 K (mC-Cs 3 BiCl 6 type[25] )C2/c 8 a = 2812.2(6) b = 867.7(2) c = 1363.3(3) ß = 99.24(3) V = 3283(1)4.435tP-Cs 3 BiBr 6 at 296 K (Tl 3 BiCl 6 type[22] )P4 2 /m 2 a = 983.98(2) c = 805.54(3) V = 779.9(4) 4.629…”

Metal Nitrides Grown from Ca/Li Flux: Ca6Te3N2 and New Nitridoferrate(I) Ca6(LixFe1–x)Te2N3

“…This Ca 6 MTe 2 N 3 (M = Fe/Li) structure can be viewed as a stuffed anti-type of the Tl 3 BiCl 6 structure (which is a simpler variant of the (NH 4 ) 3 MoCl 6 structure type). 44 The calcium cations of Ca 6 (Li x Fe 1−x )Te 2 N 3 occupy the chloride sites of Tl 3 BiCl 6 , and one of the nitride sites (on the 2c Wyckoff site) occupies the bismuth position. The tellurium anions are in the 4j Wyckoff site, in the same position as one of the thallium sites in Tl 3 BiCl 6 .…”