Complex halides of transition metals. Part IX. Preparation and electronic and vibrational spectra of the mixed hexahalogenoniobates(V) and hexahalogenotantalates(V)[Et4N]MX5Y (X = Cl or Br, Y = Cl, Br, or I) including a vibrational analysis of the MX5Y– anions

Abstract

The crystalline complexes [Et₄N]MX₅Y (M = Nb or Ta; X = Cl or Br; and Y = Cl, Br, or l) have been prepared and their electronic and vibrational spectra recorded. The i.r. and Raman spectra of the NbCl₅Br^–, TaCl₅Br^–, and TaBr₅Cl^– anions and i.r. spectra of NbBr₅Cl^– and NbBr₅l^– are assigned on the basis of an approximately C_4v octahedral anion. Force-constant values for MX₅Y^– and MY₅X^– were transferred directly from the parent species MX₆^– and MY₆^–, and were used to calculate the vibrational frequencies of the mixed-halide complex anions. The salts [Et₄N]Ml₆(M = Nb or Ta) have also been prepared, their i.r. spectra measured, and ν₃ and ν₄ assigned for these octahedral anions.