Oligomerization of digoldacetylide complexes through angular head-to-tail aurophilic bonding

The concept of aurophilic bonding predicts an extended supramolecular chemistry of mono and dinuclear gold acetylide complexes, but examples of the type (R₃P)AuC=CAu(PR₃) reported in the literature were all found to be monomeric owing to the influence of the auxiliary phosphine ligands employed. Compounds prepared with small tertiary phosphines have now been shown to exhibit the expected oligomerization: Complexes of the type (R₃P)-AuC≡CAu(PR₃) with R₃P = Me ₃P and Me₂PhP were found to have one-dimensional zigzag chain structures in which the molecular units are linked head-to-tail through short α,ω Au- -Au contacts. By contrast, (Et ₃P)AuC≡CAu(PEt₃), with its more bulky phosphines, shows monomeric units of D₃ symmetry in the crystal. The mononuclear complex (MePh₂P)-AuC≡CH is a dimer in the solid state, with one short Au- -Au contact. This angular dimeric unit (C₂ symmetry) resembles the connectivity pattern in the zigzag chains of the aggregates of the dinuclear complexes. The compounds have also been characterized through their vibrational (IR/Raman), multinuclear NMR, and mass spectra.