Theoretical studies on an unusual [Ag]+⋯[Au]−⋯[Au]−⋯[Ag]+ metallophilic pattern: Dispersive forces vs. classical coulomb forces

We have studied theoretically the organometallic compound [{Au(C6Cl5)2}Ag([9]aneS3)]2, which displays an unprecedented [Ag]+–[Au]−–[Au]−–[Ag]+ sequence of metals, formed by unsupported Au(I)⋯Au(I) and Au(I)⋯Ag(I) interactions and weaker Cipso⋯Ag and C6Cl5⋯C6Cl5 π-stacking interactions. Density Functional Theory calculations using the pbe functional (DFT/pbe), Hartree–Fock (HF), and second-order Møller Plesset perturbation theory (MP2) calculations have been performed on five model systems based on the X-ray structure. Two dinuclear models (A1 and A2) have been used to estimate the BSSE-corrected interaction energy at HF and MP2 levels between one Ag(I) and one Au(I) fragment and permit to separate the Cipso⋯Ag(I) and Au(I)⋯Ag(I) contribution to the interaction. Three tetranuclear models (B1–B3) have been used to determine the Cipso⋯Ag(I), Au(I)⋯Ag(I), Au(I)⋯Au(I) and π-stacking interactions present in the molecule. The HF level accounts for the ionic component of the interactions and the MP2 level also account for the dispersive contribution; both permits to study the nature and strength of all different types of interactions present in the molecule.