Die Kristallstruktur und die diffuse Streuung von Dimethyl-[3-dimethylamino-2-azapropen-(2)-yliden]ammoniumtrijodid, C6H14N3I3

Abstract

Dimethyl-(3-dimethylamino-2-aza-propen(2)-yliden)ammonium triiodide, C6H14N313, crystallizes in the space group P2~/m with two formula units per cell. The lattice parameters are a = 10.095 (3), b = 7.120 (3), c= 10.168(3),/~= 104-85(5) °. The crystal structure was determined by the heavy-atom method and refined by the least-squares method with anisotropic temperature factors for iodine to R = 4-9 % using diffractometer data. The structure is built up of C6H14N3 cations and asymmetric I3 anions which lie on mirror planes at y=0.25 and 0.75. The I-I bond lengths are 2-972 and 2.886 ~. For a number of polyiodides diffuse scattering was observed on films taken with long exposures. In all these cases it could be shown that the form and intensity of the diffuse scattering are related to the structure by the molecular Fourier transform of the anions. In the case of C6H14N313 and C6H14N3ICI2 a possible explanation for the fine structure of the diffuse scattering is given.