EXAFS Studies of Cd2(AlCl4)2: Structure of the Cd22+Ion

Homopolyatomic ions of metals [1] are of considerable interest since they are among the simplest examples of isolated metal-metal bonding. The Hg22+ cation is well known. Recently compounds containing the Hg32+ and Hg42+ cations have been prepared and structurally characterized [2]. Compounds containing the analogous Cd22+ species are much less stable and the structure of Cd22+ has not yet been determined in any simple system. Cd22+ was first postulated to explain the properties of Cd/CdCl2 melts. Raman [3] and magnetic measurements indicate that Cd22+(A1C14−)2 is produced in fused mixtures of Cd, CdCl2 and A1C13. Since crystals of the micaceous Cd2(AlCl4)2 suitable for single crystal studies have not yet been obtained, we have used Cd K-shell EXAFS to investigate the structure of this species.