Templating effect of neutral dithiane ligands on the self-assembly of cationic Au(I)-phosphine units

The interactions between the dinuclear Au(I) precursor (dppm)Au₂Cl₂ and neutral sulfur-containing dithianes (specifically 1,3- and 1,4-dithiane) were examined in the presence of NH₄PF₆. Although these sulfur-based ligands were initially employed to facilitate the formation of mixed phosphine/sulfur Au(I) complexes, single-crystal X-ray diffraction analysis revealed the unexpected generation of multinuclear Au(I) assemblies exclusively coordinated by phosphine ligands. When 1,3-dithiane was present, a trinuclear Au(I) complex was isolated, characterized by a central four-coordinate Au(I) center exhibiting a distorted see-saw geometry, flanked by two terminal Au(I) centers with T-shaped coordination environments. Importantly, the dithiane ligand did not coordinate directly to the gold centers in the final complex; rather, it functioned as a neutral structural template that directed the self-assembly of the trinuclear aggregate. Conversely, in the absence of dithiane, a structurally distinct trinuclear Au(I) isomer was obtained, underscoring the significant influence of donor additives in modulating aggregation pathways and determining the ultimate molecular geometries. The observed short Au(I)···Au(I) distances suggest the presence of substantial intramolecular aurophilic interactions, which play a crucial role in stabilizing these assemblies. Collectively, these findings illustrate that minor variations in reaction parameters, as well as the inclusion or exclusion of weak, noncoordinating donor ligands, can markedly affect the self-assembly processes and structural diversity of multinuclear Au(I) complexes.