The crystal structure of some rhenium and technetium dichalcogenides

The crystal structures of ReSe2,ReS2, ReSSe and TcS2 are determined using single crystal X-ray diffraction. The compounds are triclinic with space group P (1) over bar. ReSe2, Res(2) and ReSSe have a distorted CdCl2-type structure; TcS2 has a distorted Cd(OH)(2)-type structure. In the case of Res, there are two sandwiches in the unit cell, related by symmetry centers. The other compounds have one sandwich per unit cell and the centers of symmetry are within the Re (Tc)-layer, In all compounds the Re (Tc) atoms in each layer form parallelogram-shaped connected clusters with Re-Re (Tc-Tc) distances of ca. 2.7-2.8 Angstrom, in the cluster and ca. 2.9 Angstrom, between clusters. The chains of clusters run along the a-axis. Unit cell dimensions and structure of Res(2) differ from the one reported recently by Murray et al. (Inorg. Chem., 33 (1994) 4418) where only one sandwich is present and the centers of symmetry are in the Re layer. The structure of ReSe2 differs from that reported by Alcock and Kjekshus (Acta Chem. Scand., 19 (1965) 79), in the sense that these authors interchanged inversion-centers and pseudo-centers.