Halide Anion Templated Synthesis and Structural Characterization of Rhombic Dodecahedron Silver-Alkynyl Cage Complexes

Abstract

A series of silver alkynyl cages were synthesized using ligand 3,5-di-tert-butyl-phenylethynide and were structurally characterized. Reaction with [Ag(ArC≡C)]_n polymer and (ⁿBu₄N)X (X = F, Cl, Br) gave compounds incorporating different halogen anions (F⁻, Cl⁻, Br⁻) and a hollow compound, namely [Ag₁₄(ArC≡C)₁₂(MeCN)₆](OTf)₂ · 4MeCN (I), [Ag₁₄(ArC≡C)₁₂(EtOH)₂F]F · EtOH (II), [Ag₁₄(ArC≡C)₁₂(THF)₂Cl]OH · THF (III) and [Ag₁₄(ArC≡C)₁₂(MeCN)₄Br]OH (IV) (ArC≡C = 3,5-di-tert-butyl-phenylethynide). Direct synthesis of anion containing cages and indirect synthesis from the hollow cage were achieved. Structural studies (CCDC nos. 1831128 (I), 1831129 (II), 1831130 (III), and 1831131 (IV)) revealed that the incorporation of anions reduced the mean Ag−Ag bond length and therefore the cage size, giving the order of F@Ag₁₄ ≈ Cl@Ag₁₄ < Br@Ag₁₄ < halogen-free. The cage size was larger than those of similar Ag₁₄ clusters reported previously, which is likely due to the use of bulky alkynyl ligands.