Acta Cryst. (2005). E61, i208-i210  [ doi:10.1107/S1600536805026930 ]

K₄Nb_0.96Ta_1.04S₁₁

Y. Wu, C. Näther and W. Bensch

Abstract: The reaction of K₂S₃, Nb, Ta and S yields single crystals of non-stoichiometric tetrapotassium niobium tantalum undecasulfide, K₄Nb_0.96Ta_1.04S₁₁. The compound is isotypic with K₄Nb₂S₁₁ and the orthorhombic modification of K₄Ta₂S₁₁. The structure consists of discrete K⁺ cations and complex [M₂S₁₁]^4- (M = Nb and Ta) anions, in which the Nb and Ta atoms occupy the same Wyckoff positions statistically. Both M atoms are sevenfold coordinated by S₂^2- and S^2- anions. The coordination polyhedra can be described as distorted pentagonal bipyramids. Two such bipyramids share a common face, thus forming the [M₂S₁₁]^4- anion.

Online 31 August 2005

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