CARBONATE ISOSTRUCTURAL ANIONS [SNX3]5- I N THE COMPOUNDS RB6[SNX3]O0.5 AND CS6[SNX3]O0.5 WITH X=AS, SB, AND BI

The metallic shining compounds Rb6[SnX3]O0.5 and Cs6[SnX3]O0.5 with X = As, Sb, and Bi were prepared from the melt starting from adequate mi xtures of the elements and SnO2. They crystallize in the hexagonal sys tem (space group P6(3)/mmc, No. 194, Z = 2) with the lattice constants mentioned in ''Inhaltsubersicht''. In the structures of the isotypic compounds tin and the main group(V) elements build up trigonal planar anions [SnX3]5- with X = As, Sb, and Bi isostructural to the carbonate anion, oxygen forms isolated O2- ions. The bond lengths Sn-X are sign ificantly shortened with respect to the sums of Pauling covalent radii . The atoms of the units [SnX3]5- are coordinated by alkali metal cati ons forming trigonal prisms and the O2- anions occupy octahedral holes .