Chemistry of polynuclear metal halides. II. Preparation of polynuclear niobium chloride and bromide

Article abstract of DOI:10.1021/ic50047a001

Improved preparations leading to the compounds Nb₆X₁₄·8H₂O (X = Cl, Br) are described. High yields of Nb₆Cl₁₂²⁺ were obtained by the high-temperature reaction of KCl and Nb₃Cl₈ which proceeds via 14KCl + 5Nb₃Cl₈ = 2K₄Nb₆Cl₁₈ + 3K₂-NbCl₆. Extraction of this reaction mixture with water provides a convenient route to Nb₆Cl₁₄·8H₂O. The attempted formation of Nb₆Cl₁₄ via direct reduction of NbCl₅ with aluminum was unsuccessful. However, aluminum reduction of NbBr₅ provided an unidentified anhydrous product from which yields of up to 35% Nb₆Br₁₂²⁺ were extracted. Equilibration reactions involving niobium and Nb₃Br₈ at temperatures up to 975° gave no evidence for phases having Br: Nb < 2.67. Spectra and extinction coefficients for aqueous Nb₆Cl₁₂²⁺ and Nb₆Br₁₂²⁺ are given. Copyright 1967 by the American Chemical Society.