Quaternary chalcogenides of the IVa metals with layered structures: 1. Preparation and structural chacterization of Tl2Cu2Hf3Se8, Tl2Cu2Zr3S8 and Tl2Cu2Zr3Se8

Tl2Cu2Zr3S8, Tl2Cu2Zr3Se8 and Tl2Cu2Hf3Se8 were prepared by reacting stoichiometric mixtures of thallium chalcogenides, copper, the IVa metal and its corresponding chalcogen at 800?C. The compounds crystallize with a new structure type, mC30, space group C2/m (no.12), Z=2, with a=14.328(2)Ä, b=3.7870(8)Ä, c=14.250(2)Ä, ß=113.59(2)? (Tl2Cu2Hf3Se8); a=14.033(2)Ä, b=3.7008(6)Ä, c=13.874(3)Ä, ß=113.93(1)? (Tl2Cu2Zr3S8) and a=14.392(3)Ä, b=3.828(1)Ä, c=14.387(3)Ä, ß=113.69(2)? (Tl2Cu2Zr3Se8). The crystal structure of Tl2Cu2Hf3Se8 was determined from single crystal diffractometer data and refined to a conventional R value of 0.032 (717 Fo values, 48 variables). The probable isotopy of the zirconium chalcogenides was established from their powder diffraction diagrams. The characteristic feature of this new crystal structure is the formation of anionic layers 2-oo-[Cu2Hf3Se8](2-) which are separated by Tl(+) ions. The layers are built up by a corrugated network of edge- and corner-sharing HfSe6 octahedra with copper atoms occupying distorted tetrahedral niches. The Tl(+) ions are in a bicapped trigonal prismatic coordination through Se. the crystal structure is related to that of KCuZrS3.