New tantalum polychalcogenides with infinite anionic chains: K12Ta6Se35 and KTaTe3

The new compounds K₁₂Ta₆Se₃₅ and KTaTe₃ have been synthesized through the reaction of Ta metal with a K₂Q_n(Q = Se, Te) flux. K₁₂Ta₆Se₃₅, crystallizes with 4 formula units in space group Pbcn of the orthorhombic system in a cell of dimensions a = 8.3390(17) Å, b = 13.259(3) Å, c = 56.023(11) Å (t = −120 °C). KTaTe₃ crystallizes with 20 formula units (or 4 formula units of K₅Ta₅Te₁₅) in the monoclinic space group P2₁/c in a cell of dimension a = 7.7177(15) Å, b= 13.826(3) Å, c = 30.981(6) Å, and β = 90.11(3)° (t = −120 °C). Each structure consists of infinite anionic chains of Ta-containing polyhedra well separated by K⁺ cations. In K₁₂Ta₆Se₃₅ there are Ta₂Se₁₁ units formed by the face sharing of two TaSe₇ elongated bipyramids. These Ta₂Se₁₁ units are in turn interconnected by Se₂ and Se₃ units to form _α¹Ta₆Se₃Se₃₅¹²⁻]infinite chains. In KTaTe₃, the _α¹TaTe₃⁻] infinite chains arise from the face sharing of distorted TaTe₆ octahedra.