Directing role of anions in the syntheses of the silver–alkynyl cages [Ag14(CCtBu)12X][BF4] (X=F, Cl, Br) and silver–alkynyl polymers [Ag3(CCtBu)2(X)]n (X=Tos, NO3)

The reactions between silver(I) salts and tert-butylacetylene in the presence of different anions (i.e. F−, Cl−, Br−, BF4− Tos− and NO3−) are reported. When fluoride, chloride or bromide salts are present, AgBF4 reacts with tert-butylacetylene to yield the rhombic dodecahedral silver-alkynyl cages [Ag14(CCtBu)12X][BF4] (X=Cl, 1; Br, 2; F, 3). The crystal structure of the fluoride-containing cage is presented in this paper and compared to the previously reported structures of the chloride and bromide-containing cages. In the three structures, the silver atoms are held together by a combination of bridging alkynyl groups and Ag⋯Ag metallophilic interactions. A remarkable feature in the syntheses of these cages is the templating role played by the halide anions. Solution IR spectroscopy and ESI mass spectrometry experiments have demonstrated that the cage structure of compounds 1–3 is retained in solution. When AgTos (Tos=p-toluenesulfonate) and AgNO3 are reacted with tert-butylacetylene (in the absence of halides) the formation of the organometallic polymers [Ag3(CCtBu)2X]n (X=Tos, 4; NO3, 5) is observed. The crystal structure of 4 is here reported.