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

Slow cooling of melts composed of TlCl and BiCl₃ allows for the isolation of the compounds Tl₃BiCl₆ ( 1 ) and TlBi₂Cl₇ ( 2 ). Compound 1 is formed by sublimation at 480 °C from the black melt of 3 TlCl + 1 BiCl₃ as colourless crystals. The crystal structure determination (tetragonal, P4₂/m) consists of nearly regular octahedral [BiCl₆]^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 Tl₃BiCl₆, the mineral steropesite. Compound 2 is obtained from a dark red melt of composition TlCl + 2 BiCl₃. On rapid cooling, this melt solidifies to a metastable dark red glass which at ambient temperature crystallises to a light amber crystalline powder within some weeks. The structure of 2 was determined by powder diffraction (triclinic, P\bar{1} ). A distinct lone pair effect is present causing an irregular coordination on the two independent bismuth atoms. Taking Bi–Cl bonds up to 3.5 Å into account, both bismuth atoms gain coordination number seven. ²⁰³Tl and ²⁰⁵Tl solid state NMR and XANES spectra on the Bi and Tl‐L_III edges of both glassy and crystalline TlBi₂Cl₇ 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 Bicyclic Polyselenium Cation Se102+ in the Structure of Se10[Bi4Cl14]

In the ternary system Se/Bi/Cl a new polycation containing phase besides the already known Se₄[Bi₄Cl₁₄], Se₈[Bi₄Cl₁₄], and Se₁₀[Bi₅Cl₁₇] was discovered. Red, transparent, plate shaped crystals of Se₁₀[Bi₄Cl₁₄] were formed by reaction of Se/SeCl₄/BiCl₃ in 15:1:8 molar ratio in evacuated glass ampoules applying a temperature gradient from 90 to 80 °C. The crystal structure consists of bicyclic Se₁₀²⁺ cations and of layered chloridobismutate anions with the cations located between the anionic planes. The atoms of the cation form a six membered ring with a Se₄ chain bridging over the 1,4 positions of the Se₆ ring. The anions are made up of BiCl₇ polyhedra connected by common edges to layers all contain an anion of identical formula and two‐dimensional connectivity, but these polymeric chloridobismutates are not isostructural. The structural differences are discussed on basis of the different topologies of the nets made up by the bismuth atoms.