Darstellung und spektroskopische Charakterisierung der reinen Bindungsisomeren [ReX5(NCS)]2− und [ReX5(SCN)]2−, X = Cl,Br

Preparation and Spectroscopic Characterization of the Pure Bondisomers ReX₅(NCS)]^2? and ReX₅(SCN)]^2?, X = Cl, Br The treatment of (TBA)₂ReBr₆] with NaSCN in acetone or of (TBA)₂ReCl₅I] with AgSCN in CH₂Cl₂ yields mixtures of the bondisomers ReBr₅(NCS)]^2?/ReBr₅(SCN)]^2? or ReCl₅(NCS)]^2?/ReCl₅(SCN)]^2?, which are isolated as pure compounds by ion exchange chromatography on DEAE-Cellulose. The i.r. and Raman spectra are assigned according to local symmetry C_4v. The bondisomers are significantly distinguished by the frequencies of inner ligand vibrations: ν_CN(S) > ν_CN(N), ν_CS(N) > ν_CS(S), δ_NCS > δ_SCN. The electronic absorption spectra measured at 10 K exhibit in the region 6000 to 16000 cm^?1 all intraconfigurational transitions (t) splitted into Kramers dubletts by lowered symmetry (C_4v) and spin orbit coupling. The O? O transitions are deduced from vibrational fine structure. The charge transfer spectra of the bondisomers in the UV/VIS region are similar to those of the corresponding hexahalorhenates(IV).