New Compounds Containing the Complex Anion [Ta₂S₁₁]^4-; A₄Ta₂S₁₁ (A = Rb, Cs)

The new tetra(alkali metal) ditantalum undecasulfides A₄Ta₂S₁₁ (A = Rb, Cs) were prepared at low temperature via the molten-flux method. The crystal structures consist of well separated A⁺ and [Ta₂S₁₁]^4- ions. Within the anions, the Ta atoms display a sevenfold coordination by S₂^2- units and S^2- anions; the coordination polyhedra can be described as distorted pentagonal bipyramids. Two such bipyramids share common faces, thus forming the [Ta₂S₁₁]^4- anion.

-1