Studies of polyhalides. 38. On potassium-benzo-18-crown-6-polyiodides [K(benzo-18-crown-6)]I-n with n = 3, 4, 6: Preparation and crystal structures of a triiodide [K(benzo-18-crown-6)]I-3, an octaiodide [K(benzo-18-crown-6)](2)I-8 center dot(1)/2C2H5OH and a dodecaiodide [K(benzo-18-crown-6)](2)I-12

The new compounds [K(benzo-18-crown-6)]I-3, [K(benzo-18-crown-6)](2)I-8. 1/ 2 C2H5OH, and [K(benzo-18-crown-6)](2)I-12 have been prepared by the reacti on of benzols-crown-6 (B18K6, C16H24O6), potassium iodide KI and iodine I-2 in ethanol/dichlormethane. Their crystal structures have been determined b y single crystal X-ray diffraction methods. The triiodide consists of two c rystallographically different cations [K(benzo-18-crown-6)](+) and anions I -3(-) respectively, which can be regarded as isolated units. The octaiodide and the dodecaiodide achieve their structure by a decomposition into a I-3 (-)- and a I-5(-)-ion or a I-5(-)- and a I-7(-)-ion. The octaiodide builds a new type of chain with an additional twofold co-ordination via the middle iodine atom of the triiodide group. This type of chain has not been descri bed up to now. In the dodecaiodide the Z-shaped heptaiodide units form a he lix which is limited by the V-shaped pentaiodide units.