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

Abstract

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 in the charged dimers and of 70-105 kJ mol in the corresponding neutral dimers. In the neutral dimers, pure aurophilic interactions account for 25-30 kJ mol, the dipole-dipole interactions for 30-45 kJ mol, and the L···L' "inter-ligand" dispersion interactions for 5-25 kJ mol. Energy of the aurophilic interactions is thus comparable or even larger than that of strong hydrogen bonds.

Proof of Concept for Hydrogen Bonding to Gold, Au⋅⋅⋅H−X

“…Forc rystallization, an anion exchange (OTf À vs.B (Ar F ) 4 À ;A r F = 3,5-(F 3 C) 2 C 6 H 3 )w as carried out, providing an ew environment in the crystal. [12] Fort his work, ac ationic gold(I) chloride complex of the type [L''(H)ÀAuÀCl] + (investigated previously in ad ifferent context) [13] was selected, where the metal atom is coordinated by an N-heterocyclic carbene (NHC) ligand L'' bearing ap rotonated 2-(dimethylaminomethyl)phenyl substituent (3a). Notably,there are several parallels to the seminal work by the group of van Koten on Pt II compounds.…”

“…It is therefore very fortunate that yet another recent study by Straka, Andris, Vícha, Rů žička, Roithovµ,a nd Ruližek (Prague and Pardubice (Czech Republic) and Nijmegen (The Netherlands)) has finally provided experimental data for the gas phase for which hitherto only computational results had been available (see above). [12] Fort his work, ac ationic gold(I) chloride complex of the type [L''(H)ÀAuÀCl] + (investigated previously in ad ifferent context) [13] was selected, where the metal atom is coordinated by an N-heterocyclic carbene (NHC) ligand L'' bearing ap rotonated 2-(dimethylaminomethyl)phenyl substituent (3a). This cation was identified by electrospray ionization mass spectrometry and further characterized in the gas phase by helium tagging infrared photodissociation (IRPD) spectroscopy.I Ra nd NMR spectroscopic studies in solution (methanol, HCl) gave no meaningful results owing to the limited stability under the acidic conditions required for protonation, and attempts to isolate the product by crystallization failed.…”

Enhanced Metallophilicity in Metal–Carbene Systems: Stronger Character of Aurophilic Interactions in Solution

“…Depending on the nature of solvents, ligands and counterions, binding energies betweenc losed-shellm etals have been estimated to be in the range 7-12 kcal mol À1 for gold and 5-15 kcal mol À1 for silver. [10,13,28,29] Although it could be assumed that aurophilicb onds are stronger than their argentophilic analogues, there is al ack of conclusive evidences to support this fact. [13] In the past, we discussed the effect of strong electron-donor ligandso nc losed-shell metal ions, and postulated that M-M interactions may surpass the van der Waals radii.…”

“…This methodh as proven to produce accurate resultsf or other Au-Au dimers. [29] Modelsw ere built deleting C31 and C61 bridges and replacing them by Ha toms (see detailsi nt he Supporting Information). Ta ble 4s hows the computed values for the interaction energies between the two resultingmonomers.…”

Erfolgreiche Machbarkeitsstudien für Wasserstoffbrücken zu Gold: Au⋅⋅⋅H‐X

“…Fürd iese Arbeiten wurde wieder ein Komplex mit einem Kation der Formel [L''(H)-Au-Cl] + ausgewählt, der früher in anderem Zusammenhang vorgestellt worden war. [13] L'' steht füre inen NHC-Liganden (NHC = N-heterocyclisches Carben), der einen protonierten 2-Dimethylaminomethyl-Substituenten trägt (3a). Dieses Kation wurde durch Elektronenspray-Massenspektrometrie identifiziert und in der Gasphase durch Helium-markierte Infrarot-Photodissoziations(IRPD)-Spektroskopie weiter studiert.…”