SYNTHESIS AND CRYSTAL-STRUCTURE OF ALKALI-METAL-GOLD CHALCOGENIDES AAUX, WHERE A=NA, K, RB OR CS AND X=S, SE OR TE

The alkali metal gold(I) chalcogenides RbAuS, CsAuS, RbAuSe, CsAuSe, NaAuTe, KAuTe, RbAuTe and CsAuTe have been synthesized by fusion reactions of the elements in an ampoule at 600-degrees-C. NaAuTe and KAuTe crystallize with a layered structure which can be derived from the AlB2-type (space group P6(3)/mmc; Z = 2). The gold and tellurium atoms form planar layers of hexagons infinity 2 [AuTe-], each kind of atom coordinated with three of the other kind. The atomic arrangements in RbAuTe and CsAuTe exhibit a new structure type (space group Pmma; Z = 2) containing zigzag chains infinity 1 [AuTe-], in which the gold atoms are linearly coordinated by the tellurium atoms. Short gold-gold distances, of 2.968(1) angstrom in the rubidium and 3.106(1) angstrom in the caesium compound indicate possible interactions between the gold atoms with their d10 configuration. The sulphides and selenides RbAuS, CsAuS, RbAuSe and CsAuSe (space group Cmcm; Z = 4) also contain zigzag chains infinity 1 [AuX-] (X = S or Se). The gold-gold distances, between 3.298(1) angstrom in RbAuS and 3.431(1) angstrom in CsAuSe, are considerably longer than those in the corresponding tellurides.