Synthesis of K₄M₃Te₁₇ (M = Zr, Hf) and the Structure of K₄Hf₃Te₁₇, a New One-Dimensional Solid-State Ternary Polytelluride

The compounds K₄Zr₃Te₁₇ and K₄Hf₃Te₁₇ have been synthesized through the reaction at 900 °C of Zr or Hf with a K₂Te/Te melt as a reactive flux. The compounds crystallize in space group [formula omitted] of the monoclinic system with four formula units in cells: a = 10.148 (6) Å, b = 28.889 (17) Å, c = 11.626 (7) Å, β = 115.21 (2)° (T = 107 K) for K₄Hf₃Te₁₇; a = 10.146(2) Å, b = 29.98 (1) Å, c = 11.669 (4) Å, β = 115.01 (3)° (T = 153 K) for K₄Zr₃Te₁₇. The structure of K₄Hf₃Te₁₇ has been determined from single-crystal X-ray data. The structure comprises infinite, one-dimensional chains of Hf-centered polyhedra that extend along [101] and are separated from each other by K⁺ ions. Each Hf atom is eight-coordinate. If the Te-Te maximum bond length is taken to be 2.94 Å, then there are six [formula omitted] ligands, one [formula omitted] ligand, and a [formula omitted] ligand. The composition of the infinite chain is [formula omitted] with the Hf atoms present in the +4 oxidation state.