Studies of polyhalides .27. On tetra(n-propyl)ammonium polyiodides (n-Pr4N)I-n with n=3, 5, 7: Preparation and crystal structures of a triiodide (n-Pr4N)I-3, a pentaiodide (n-Pr4N)I-5, and a heptaiodide (n-Pr4N)I-7

[(n-C3H7)(4)N]I-3, [(n-C3H7)(4)N]I-5 and [(n-C3H7)(4)N]I-7 have been prepared by the reaction of tetra(n-propyl)ammoniumiodide [(n-C3H7)4N]I with iodine It in ethanol. Their crystal structures have been determined by single crystal X-ray diffraction methods. The triiodide is built up from layers of the quarternary ammonium ions n-Pr4N+ and from two independent differently packed centrosymmetric triiodide ions I-3(-) which alternate with each other along [100]. The pentaiodide ion forms slightly puckered almost squared nets perpendicular [001] of iodide ions which are connected with four iodine molecules by secondary bonds. The meshes from twelve iodine atoms include the cations. The centrosymmetric Z-shaped heptaiodide ion is built up from a linear symmetric triiodide ion and two iodine molecules forming twisted rope ladders along [001] which are separated by stacks of cations.