NEW POLYANIONIC SELENOAURATES: THE CRYSTAL STRUCTURES OF Cs₂Au₂Se₃, CsAuSe₃ AND Na₅AuSe₁₂. Claudia Weithaler, Kurt O. Klepp, Dept. Of Inorg. Chemistry, Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria

Cs₂Au₂Se₃ (1) and CsAuSe₃ (2) are characterized by pseudo-one dimensional structures. The seleno anions are helical chains with the sequence ...Au-Se-Au-Se₂-Au...and ...Au-Se₃-Au..., resp. Au is in almost linear chalcogen coordination characteristic for Au(I). Se-Au-Se bond angles are 175.4(1)deg. (1) and 173.3(4)deg. (2), the bond angles on the Se atoms vary between 83.6(1)deg. and 103.5(4)deg.. Au-Se bond lengths are close to 2.40 Å.

In contrast to (1) and (2) the coordination of gold in Na₅AuSe₁₂ (3) is almost square planar, in accord of an oxidation state of +3 for the gold atoms. The compound is characterized by discrete anionic species where four triselenido chains act as monodentate ligands on the central Au atom. Au-Se bond lengths are close to 2.50 Å, Se-Se bonds vary between 2.346(2) Å and 2.362(2) Å, the bond angles on the central selenium atoms of the four crystallographically different chains are close to 102deg..

The crystal structures were determined from CAD4-data obtained with MoK[[alpha]]-radiation. All atoms were refined anisotropically to conventional R- values of 0.042 (1), 0.079 (2) and 0.032 (3), respectively. The crystal structures will be published in J. Alloys Comp.

Crystal Data:

Formula s.g. a (Å) b (Å) c (Å) [[beta]](deg.) Z

Cs₂Au₂Se₃ C2/c 9.769(5) 13.44(1) 7.178(3) 90.69(2) 4

CsAuSe₃ C2/c 6.466(3) 13.75(1) 7.624(5) 112.16(2) 4

Na5AuSe₁₂ P21 7.145(1) 16.790(6) 8.291(1) 107.13(1) 2