The crystal structures of CsAu3S2, RbAu3Se2 and CsAu3Se2 and their relationship to the CsCu3S2 structure type

The new compounds CsAu3S2, RbAu3Se2 and CsAu3Se2 were prepared by high temperature reactions. They are isostructural and crystallize in P (3) over bar m1, Z = 1 with a = 6.192(1) Angstrom, c = 5.080(2) Angstrom for CsAu3S2, a = 6.112(4) Angstrom, c = 5.224(6) Angstrom for RbAu3Se2 and a = 6.281(1) Angstrom, c = 5.205(1) Angstrom for CsAu3Se2. Their crystal structures were determined by single crystal diffractometer data. They are characterized by the formation of corrugated chalcogenoaurate layers(infinity)(2)-[Au(3)Q(2)](-) separated by the alkali cations. Au is in a strictly linear coordination (d(Au-S) 2.32(1) Angstrom, d(Au-Se) 2.450(7) Angstrom and 2.434(4) Angstrom respectively), the bond angles of the chalcogens are close to 80 degrees. The shortest Au-Au distances (3.056(2) Angstrom) occur in the rubidium compound. The crystal structures are related to the CsCu3S2 type.