Evidence for Cluster Orbital Formation in CsSn2X5 Compounds (X=Cl, Br)

✍ Scribed by I. Abrahams; D.Z. Demetriou; R.T. Kroemer; H. Taylor; M. Motevalli

• Book ID: 102611194
• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 407 KB
• Volume: 160
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2001.9251

✦ Synopsis

The formation of cluster orbitals in CsSn 2 Br 5 is discussed and related more generally to tetragonal compounds of the type AB 2 X 5 (A ‫؍‬ monovalent cation; B ‫؍‬ Sn, Pb; X ‫؍‬ Cl, Br, I). The crystal structures of CsSn 2 Cl 5 and CsSn 2 Br 5 have been solved by single-crystal X-ray di4raction. These compounds are isostructural with each other and a range of AB 2 X 5 structural analogues. In many AB 2 X 5 compounds where B is a subvalent main group metal a tetragonal cell is observed with space group I4/mcm. The structures of CsSn 2 Br 5 and CsSn 2 Cl 5 are layered with polymeric sheets of [Sn 2 X 5 ] n؊ n separated by the Cs ؉ cations. Stereochemical considerations suggest that stabilization of this structural form, rather than the more ionic NH 4 Pb 2 Cl 5 or NaSn 2 Cl 5 structures, is through interaction of the 99nonbonding:: valence electron pairs on tin with low-lying empty d-orbitals on neighboring X atoms. Electronic structure calculations based on the structural data con5rm the likelihood of cluster orbital formation. Crystal data: