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BaCu 6 Ge 2 S 8 -Ein Thiogermanat als Variante der Li 3 Bi-Struktur / BaCu 6 Ge 2 S 8 -A Thiogermanate as a Variant of the Li 3 Bi Structure

1998; De Gruyter; Volume: 53; Issue: 12 Linguagem: Inglês

10.1515/znb-1998-1210

1865-7117

Markus Tampier, Dirk Johrendt,

Organometallic Compounds Synthesis and Characterization

Abstract BaCu6Ge2 S8 was synthesized by direct reaction of the elements at 750°C and characterized by X-ray single crystal techniques. The thiogermanate crystallizes in a new orthorhombic structure type (a = 6.122(1) Å, b = 12.084(3) Å, c = 17.614(5) Å; Pbcm, Z = 4). Isolated [GeS 4 ] 4- tetrahedra form a slightly distorted cubic face-centered (fee) arrangement. Baand Cu-atoms each occupy half the octahedral gaps (OG) of this “tetrahedra packing” . Further Cu atoms fill the tetrahedral gaps ( TG) completely. The compound can be written as Ba 2 (1/2OG) (Cu 2 ) 2 (1/2OG) Cu 8 (TG) (GeS 4 ) 4 . Thus the structure of BaCu 6 Ge 2 S 8 can be derived from the Li 3 Bi type. The sulfur coordination of the metal atoms (Cu tetrahedral or trigonal, Ba with CN 8) are realized by the spatial orientation of the [GeS 4 ] 4- tetrahedra. Their centers nearly maintain the fcc-arrangement. This structure interpretation of BaCu 6 Ge 2 S 8 from the viewpoint of a “filled tetrahedra packing” is discussed for further known thiogermanate compounds.