Crystal structure of the mixed-metal tris-ulfide BaCu(1/3)Ta(2/3)S(3).

The mixed-metal title compound, BaCu(1/3)Ta(2/3)S(3) [barium copper(II) tantalum(V) tris-ulfide], was prepared through solid-state reactions. The crystal structure adopts the BaTaS(3) structure type and consists of face-sharing [MS(6)] (M = Ta,Cu) octa-hedra (point-group symmetry -3m.) that are condensed into infinite chains along [001]. Adjacent chains are linked through the barium cations (site symmetry -6m2), which exhibit a coordination number of twelve. The M site is occupied by 2/3 of Ta(V) and 1/3 of Cu(II), whereby the average M-S distances are slightly longer than those of ordered BaTaS(3). The classical charge balance of the title compound can be represented by [Ba(2+)] [(Ta/Cu)(4+)] [S(2-)](3).