Preparation and structures of halidelon complexes of carbon tetrahalides and tetrahalogenoethylenes

Abstract

The preparation is reported of 33 crystalline compounds of tetra-alkylammonium halides with carbon tetrahalides and with tetrabromo- and tetraiodo-ethylene. The Raman and i.r. spectra are discussed, in conjunction with X-ray data, in terms of the site symmetries of the halogenocarbon molecules in these molecular complexes, and lattice force constants and vibrational amplitudes are calculated. The halide ion–carbon tetrahalide distances are considerably less than the sum of the ionic and van der Waals' radii by an amount which increases in the same order, Cl^– < Br^– < l^–, as the halide ion–CBr₄ lattice force constant. This together with Raman intensities of the lattice vibrations strongly indicates that the compounds should be regarded as donor–acceptor complexes.