Syntheses and structures of the quaternary alkali-metal bismuth coinage-metal chalcogenides K3Bi5Cu2S10, CsBi2CuS4, RbBi2.66CuSe5, and CsBiAg2S3

The four compounds K3Bi5Cu2S10, CsBi2CuS4, RbBi2.66CuSe5, and CsBiAg2S3 wer e synthesized at 873 K by reactions of the elements in the reactive fluxes of A(2)Q(3) (A=K, Rb, Cs; Q=S, Se). All crystallographic data were collecte d at 153 K. K3Bi5Cu2S10 crystallizes in the Rb3Bi5Cu2S10 structure type in space group Pnnm of the orthorhombic system with two formula units in a cel l of dimensions a=14.173(2) Angstrom, b=17.690(2) Angstrom, c=4.0362(5) Ang strom; CsBi2CuS4 crystallizes as a racemic twin in space group Cmc2(1) of t he orthorhombic system with four formula units in a cell of dimensions a=4. 0730(6) Angstrom, b=14.212(2) Angstrom, c=14.568(2) Angstrom; RbBi2.66CuSe5 crystallizes in a new structure type in space group Cmcm of the orthorhomb ic system with four formula units in a cell of dimensions a=4.1961(9) Angst rom, b=14.420(3) Angstrom, c=18.266(4) Angstrom; CsBiAg2S3 crystallizes in a new structure type in space group P2(1)/c of the monoclinic system with f our formula units in a cell of dimensions a=13.3523(14) Angstrom, b=8.1052( 8) Angstrom, c=6.9162(7) Angstrom, beta =99.766(2)degrees. K3Bi5Cu2S10, CsB i2CuS4, and RbBi2.66CuSe5 are related; they are all tunnel structures with the A atoms located in tunnels formed by BiQ(6) octahedra and CuQ(4) tetrah edra. CsBiAg2S3 is composed of two-dimensional (2)(infinity)[BiAg2S31-] lay ers separated by the Cs atoms. The (2)(infinity)[BiAg2S31-] layer is built from BiS6 octahedra, linear AgS2 groups, and AgS4 tetrahedra. (C) 2001 Else vier Science B.V. All rights reserved.