Quaternary chalcogenides of the IVa metals with layered structures: preparation and crystal structures of TlCuT(IV)Q3 (T=Zr,Hf; Q=S,Se) and their relation to the Re3B structure type

The new compounds TlCuT(IV)Q3 (T=Zr,Hf; Q=S,Se) were prepared by reacting intimate mixtures of Tl2S or TlSe with stoichiometric amounts of the corresponding Group IV metal, Cu and the corresponding chalcogen at 870?C. The four compounds are isostructural and crystallize in Cmcm, Z=4, with a=3.726(4)Ä, b=13.987(9)Ä, c=9.783(4)Ä for TlCuZrS3; a=3.847(1)Ä, b=14.381(6)Ä, c=10.150(1)Ä for TlCuZrSe3; a=3.694(1)Ä, b=14.030(3)Ä, c=9.750(3)Ä for TlCuHfS3; and a=3.831(1)Ä, b=14.409(9)Ä, c=10.124(2)Ä for TlCuHfSe3. Their crystal structures were determined from single crystal diffractometer data (MoK alpha radiation, ambient temperature) and refined to conventional R values of 0.016, 0.040, 0.019 and 0.031 respectively. An outstanding feature of their crystal structures is the formation of infinite anionic layers, 2-oo-[CuT(IV)Q3]- parallel to (010), which are separated by Tl(+) cations. These layers are built up by edge sharing TQ6 octahedra and distorted CuQ4 tetrahedra. Average T-Q distances are `d(Zr-S)=2.586(1)Ä, `d(Zr-Se)=2.707(1)Ä, `d(Hf-S)=2.569(2)Ä and `d(Hf-Se)=2.694(1)Ä. Cu-chalcogen distances are `d(Cu-S)=2.318(2)Ä and `d(Cu-Se)=2.432(3)Ä respectively. The thallium ions are in bicapped trigonal prismatic chalcogen coordinations. The atomic arrangement corresponds to that of KCuZrS3; based on the thallium-chalcogen partial structure it can be regarded as a filled variant of an anti-Re3B structure type.