Au...Au interactions: Z ' > 1 behavior and structural analysis.

The tendency of molecules containing an Au...Au interaction to crystallize with more than one molecule in the asymmetric unit (i.e., Z ' > 1) and the geometry of the Au...Au interaction in X-Au-Y species have been investigated. Au-containing compounds exhibiting Au...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...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...Au interaction is also analyzed, taking into account the steric and electronic characteristics of the ligands.