Aurophilic Interactions in [(L)AuCl]...[(L′)AuCl] Dimers: Calibration by Experiment and Theory

Attractive metallophilic (aurophilic, argentophilic, cuprophilic, etc.) interactions play an important role in arrangement and stabilization of oligonuclear metal ion complexes. We report a combined experimental and theoretical assessment of aurophilic interactions in closed-shell gold­(I) dimers. The experimental binding energies were obtained for charged [(LH)­AuCl]+...[(L′)­AuCl] dimers (L is either a phosphine or an N-heterocyclic carbene ligand) in the gas phase. These energies served for benchmarking of correlated quantum chemical calculations (CCSD­(T)-calibrated SCS-MP2/CBS method) that were then applied to neutral [(L)­AuCl]...[(L′)­AuCl] dimers. The overall attractive interactions between monomeric units are in the order of 100–165 kJ mol–1 in the charged dimers and of 70–105 kJ mol–1 in the corresponding neutral dimers. In the neutral dimers, pure aurophilic interactions account for 25–30 kJ mol–1, the dipole–dipole interactions for 30–45 kJ mol–1, and the L···L′ “inter-ligand” dispersion interactions for 5–25 kJ mol–1. Energy of the aurophilic interactions is thus comparable or even larger than that of strong hydrogen bonds.