Abstract
A8Tl11 (A = alkali metal) compounds have been known since the investigations of Corbett et al. in 1995 and still are matter of current discussions as the compound includes one extra electron referred to the charge of the Tl117− cluster. Attempts to substitute the charge by incorporation of a halide atom succeeded for the lightest homologue of the group, Cs8Ga11Cl, and powder diffraction experiments for the heavier homologues also suggested the formation of analogous compounds. However, X-ray single crystal studies on A8Tl11X to prove this substitution and to provide a deeper insight into the influence on the thallide substructure have not yet been performed, probably due to severe absorption combined with air and moisture sensitivity for this class of compounds. In our contribution we present single crystal X-ray analyses of the new compounds Cs8Tl11Cl0.8, Cs8Tl11Br0.9 and Cs5Rb3Tl11Cl0.5. It is shown that a (partial) incorporation of halide can also be indirectly determined by examination of the Tl-Tl distances for low resolved data sets, e.g., for Cs5.7K2.3Tl11Cl?. Mixed occupied sites by two different alkali metals indicate a dependence on the cesium content, the systems K/Rb–Tl–Br and K/Rb–Tl–Cl only gave rise to the formation of the higher reduced (K/Rb)8Tl11 and the less reduced by-product (K/Rb)15Tl27. We have not been able to prove the formation of halide including thallides in the absence of cesium.
Highlights
The largest thallide cluster is represented by the Tl117− cluster which is present in binary materials A8Tl11 [1,2] and A15Tl27 [3] (A = K, Rb, Cs)
The additional electron, referred to the charge of −7 of the cluster anion, is not necessary for the stability of the clusters [5] and can be replaced by halide atoms, which are located on a 3 void (Wyckoff position 6b) at the origin of the unit cell resulting in a diamagnetic character of the compounds
Halide incorporation was proven for the lighter homologue of the group, Cs8Ga11Cl by X-ray single crystal structure analysis
Summary
The A8Tr11 structure type was first described in 1991 for the lighter homologue indium in K8In11, [1,4] of which the crystal structure proved the presence of a naked, pentacapped trigonal prismatic shaped In11 cluster, which was assigned a charge of −7. One extra-electron per formula unit is present, which is responsible for the metallic character. The additional electron, referred to the charge of −7 of the cluster anion, is not necessary for the stability of the clusters [5] and can be replaced by halide atoms, which are located on a 3 void (Wyckoff position 6b) at the origin of the unit cell resulting in a diamagnetic character of the compounds. Halide incorporation was proven for the lighter homologue of the group, Cs8Ga11Cl by X-ray single crystal structure analysis. The formation of Rb8Tl11Cl was termed as doubtful due to the lack of a significant change in the lattice constants compared to Rb8Tl11
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
