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.