Syntheses and crystal structures of novel ternary alkali metal gold acetylides (MAuC2)-Au-I (M-I = Li, Na, K, Rb, Cs)

By the reaction of AuI with alkali metal hydrogen acetylides (MC2H)-C-I (M- I = Li-Cs) in liquid ammonia and subsequent heating of the remaining residu e in refluxing pyridine (M-I = Li, Na, K) or as a solid phase at about 110 degrees C in vacuum (M-I = Rb, Cs) ternary alkali metal gold acetylides (MA uC2)-Au-I were obtained. Their crystal structures were investigated by the means of X-ray powder diffraction. (1)(infinity)[Au(C-2)(2/2)(-)] chains ar e the characteristic structural motif which are packed in a hexagonal (LiAg C2) and tetragonal arrangement (NaAuC2-CsAuC2), respectively. Simple calcul ations based on the close packing of rods and spheres can explain these dif ferent arrangements. The existence of C-C triple bonds in the title compoun ds is confirmed by Raman spectroscopic investigations.