Pentaiodide komplexer Alkalimetall-Kronenether-Kationen: Darstellung und strukturelle Charakterisierung der Verbindungen [M(Benzo-15-Krone-5)2]I5 mit M = Na, K, Rb, Cs

The isotypic compounds [M(benzo-15-crown-5)(2)]I-5, M = Na, K, Rb and Cs are obtained as single crystals via the reaction of benzo-15-crown-5, MI and iodine (2 : 1 : 2) from ethanol/dichloromethane (1 : 1). These compounds crystallize in the monoclinic space group P2(1)/n with four formula units in the unit cell. The cations form typical sandwich complexes. The volume of the unit cell increases by 4,3%, from the sodium to the caesium compound, corresponding to the increasing space required by the cations. The pentaiodide units consist of a elongated triiodide unit and two iodine half-molecules. These iodine molecules are completed by centres of symmetry. The interconnection between the pentaiodide units leads to the formation of zig-zag chains that run along [001]. Considering the strongly different ionic radii of the alkali-metal cations, the existence of this number of isotypic structures is rather surprising.