The vibrational spectra of titanium tetrachloride–hydrochloric acid and titanium tetrachloride–tri-n-butyl phosphate systems and the hexachloro-anions of zirconium(IV), hafnium(IV), niobium(V), and tantalum(V)

Abstract

The Raman spectra of solutions of titanium tetrachloride in hydrochloric acid have been reinvestigated. These solutions probably contain oxyhalide species of the type [TiO₂Cl₄]^4– or [TiOCl₅]^3– and not [TiCl₆]^2– as was thought previously. Raman-spectroscopic studies of the titanium tetrachloride–tri-n-butyl phosphate (TBP) system show that both a 1 : 1 complex of symmetry C_2v, and a 1 : 2 complex, TiCl₄,2TBP (probably cis, of symmetry C_2v) are formed. The Raman spectra of solutions of the tetrachlorides of zirconium(IV) and of hafnium(IV) in hydrochloric acid show that the hexachloro-anions are present in these solutions. The vibrational spectra of NbCl₆^– and TaCl₆^– were obtained by studying the Raman spectra of solutions of the tetraethylammonium salts in acetonitrile and nitromethane respectively.