The Energetic Significance of Metallophilic Interactions

Metallophilic interactions are increasingly recognized as playing an important role in molecular assembly, catalysis, and bio-imaging. However, present knowledge of these interactions is largely derived from solid-state structures and gas-phase computational studies rather than quantitative experimental measurements. Here, we have experimentally quantified the role of aurophilic (Au^I ⋅⋅⋅Au^I ), platinophilic (Pt^II ⋅⋅⋅Pt^II ), palladophilic (Pd^II ⋅⋅⋅Pd^II ), and nickelophilic (Ni^II ⋅⋅⋅Ni^II ) interactions in self-association and ligand-exchange processes. All of these metallophilic interactions were found to be too weak to be well-expressed in several solvents. Computational energy decomposition analyses supported the experimental finding that metallophilic interactions are overall weak, meaning that favorable dispersion and orbital hybridization contributions from M⋅⋅⋅M binding are largely outcompeted by electrostatic or dispersion interactions involving ligand or solvent molecules. This combined experimental and computational study provides a general understanding of metallophilic interactions and indicates that great care must be taken to avoid over-attributing the energetic significance of metallophilic interactions.