Synthesis, Structure and Spectroscopy of a New Polyiodide in the ,-Diazaniumalkane Iodide/Iodine System

The reaction of 1,4-diaminobutane with hydroiodic acid in the presence of iodine yields the title compound 1,4-diazaniumbutane tetraiodide, C4H14N2I4 (1). The title compound has been structurally characterized by crystallographic and spectroscopic methods (Raman and IR). 1 is built up by centrosymmetric 1,4-diazaniumbutane cations in all-trans conformation and linear I4 anions. Both, cations and anions are located on centers of inversion (2/m) in the monoclinic space group C2/m. The hydrogen bonds between the azanium groups and the terminal iodine atoms of the I4 anions lead to a three-dimensional framework. The structural parameters of the tetraiodide anion, derived from X-ray crystallographic data are in excellent agreement with the results from Raman spectroscopy. The Raman and IR data for the analogous α ,ω-diazaniumalkane tetraiodide salts (H3N-(CH2)6-NH3)I4 (2) and (H3N-(CH2)7-NH3)I4 (3) are reported, and the structures of 1, 2 and 3 are compared.