LOW-TEMPERATURE FOURIER-TRANSFORM INFRARED-SPECTRA OF TETRACHLOROZINCATE, TETRACHLORONICKELATE AND TETRACHLOROCUPRATE WITH DIFFERENT COUNTER IONS

Room-temperature infrared (IR) and Raman and low-temperature (100 and 77 K) IR spectra of R2MCl4 have been recorded in the 4000-50 cm-1 freq uency range. The metal ions Zn(II), Ni(II) and Cu(II) form a series of increasing ionic radius, while the counter ions [Bu4N]+, [Et4N]+, Rb, and Cs+ reflect the order of decreasing bulkiness. According to the IR and Raman spectra, the [ML4]2- units are a distorted tetrahedron, t he distortion away from the tetrahedral structure increasing with the increasing size of the counter ion. Additional splittings due to the v ibration-electronic coupling (Jahn-Teller coupling) was observed for t he Cu(II) and Ni(II) compounds.