Synthese, Kristallstruktur und elektronische Bandstruktur der isotypen Sulfidchloride CuBiSCl2 und AgBiSCl2

Black, platelet crystals Of MBiSCl2 (M = Cu, Ag) were synthesized by heating stoichiometric amounts of MCl and BiSCl X-ray diffraction on powders and single-crystals revealed that the compounds crystallize isostructural with space group Cmcm (Cu/Ag: a = 396.9(l)/397.1(l); b = 1278.6(3)/1371.2(3); c = 859.7(2)/882.4(2) pm). In the crystal structures the Bi-III. cations have a bi-capped trigonal prismatic coordination of two sulfide and six chloride ions. The polyhedra constitute layers (2)(infinity)[BiS2/2Cl6/3-] by sharing common edges and faces. The layers are separated by transition metal cations M-1. Their distorted octahedral coordination comprises two short bonds M-S in trans position and four M-Cl bonds that are about 50 pm longer. From relativistic band structure calculations (DFT) is deduced that AgBiSCl2 is an indirect semiconductor with a band gap of about 1.0 eV.