Au•••Au interactions:: Z′>1 behavior and structural analysis

The tendency of molecules containing an Au center dot center dot center dot Au interaction to crystallize with more than one molecule in the asymmetric unit (i.e., Z ' > 1) and the geometry of the Au center dot center dot center dot Au interaction in X-Au-Y species have been investigated. Au-containing compounds exhibiting Au center dot center dot center dot Au interactions are shown to form Z ' > 1 structures in 25.0% of cases, compared with 7.8% for Au-containing species where no Au center dot center dot center dot Au interactions exist and 8.8% for the Cambridge Structural Database as a whole. This propensity toward high Z ' behavior is investigated by considering the nature of the packing of the compounds as well as the characteristics of the ligands and, in particular, the difference in sizes of the X and Y ligands. The geometry and conformation of molecules linked by an Au center dot center dot center dot Au interaction is also analyzed, taking into account the steric and electronic characteristics of the ligands.