Recent studies on alkynyl complexes of the Group 11 and 12 metals

Although alkynyl complexes of Group 11 and 12 metals have been known for many years, recent crystallographic studies have revealed some interesting and novel structural features. These result from the combination of the alternative bonding modes available to the alkynyl ligand and the occurrence of weak metal–metal interactions. These come together to favour the formation of polynuclear ring and polyhedral structures. For example, the seemingly simple isoleptic compound [Au(C2tBu)] has a catenane structure based on two interweaving Au6 rings and within each ring the alkynyl ligands displaying a range of bonding modes which involve σ- and π-bonding. The study of the reactions of the corresponding silver compound has revealed the formation of a complex with a cation which has a regular rhombohedral structure which is based on a halide anion encapsulated by 14 silver atoms. This compound results from the incorporation of halide anions in the interstitial site in the work-up process. The reactions between the mercury–dialkynyl complexes [Hg(C2R)2] (R=Ph, Tol or tBu) and silver(I) and copper(I) ions have led to complexes where the Group 11 metal ions are π-coordinated to the alkynyl π-bonds. This leads to an interesting series of structures and, for example, {[Hg(C2Tol)2Ag][BF4]}n has a polymeric structure with helices cross linked by CH⋯π-interactions.