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.

Homobimetallic metallophilic interactions between copper, silver, and gold-based [(NHC)MX]-type complexes (NHC=N-heterocyclic carbene, i.e, 1,3,4-trimethyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene; X=F, Cl, Br, I) were investigated by means of ab initio interaction energies, Ziegler-Rauk-type energy-decomposition analysis, the natural orbital for chemical valence (NOCV) framework, and the noncovalent interaction (NCI) index. It was found that the dimers of these complexes predominantly adopt a head-to-tail arrangement with typical M⋅⋅⋅M distance of 3.04-3.64 Å, in good agreement with the experimental X-ray structure determined for [{(NHC)AuCl}2 ], which has an Au⋅⋅⋅Au distance of 3.33 Å. The interaction energies between silver- and gold-based monomers are calculated to be about -25 kcal mol(-1) , whereas that for the Cu congener is significantly lower (-19.7 kcal mol(-1) ). With the inclusion of thermal and solvent contributions, both of which are destabilizing, by about 15 and 8 kcal mol(-1) , respectively, an equilibrium process is predicted for the formation of dimer complexes. Energy-decomposition analysis revealed a dominant electrostatic contribution to the interaction energy, besides significantly stabilizing dispersion and orbital interactions. This electrostatic contribution is rationalized by NHC(δ(+) )⋅⋅⋅halogen(δ(-) ) interactions between monomers, as demonstrated by electrostatic potentials and derived charges. The dominant NOCV orbital indicates weakening of the π backdonation in the monomers on dimer formation, whereas the second most dominant NOCV represents an electron-density deformation according to the formation of a very weak M⋅⋅⋅M bond. One of the characteristic signals found in the reduced density gradient versus electron density diagram corresponds to the noncovalent interactions between the metal centers of the monomers in the NCI plots, which is the manifestation of metallophilic interaction.

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Generating monovalent pnictogens within NCN pincers has resulted in the isolation of three distinct types of 1,2-azaheteroles, highly aromatic nitrogen analogues like pyrazole-based 5, aromatic yet fluxional P- and As-derived bell-clappers 1 and 2, and hypervalent Sb and Bi derivatives 3 and 4, which are supported by 3-center, 4-electron N–E–N bonds. Careful analysis of the solid-state structures of 1–5/[5-Me]­[OTf] in combination with NICS calculations (at the GIAO/M06/cc-pVTZ­(-PP) level) and other computational methods (NBO) suggest that simpler NC chelates may support new phosphorus- and arsenic-containing heterocycles. Indeed, reduction of ECl2 (E = P or As) derivatives supported by N-Dipp (Dipp = 2,6-diisopropylphenyl) substituted NC bidentate ligands produced 1,2-benzoazaphosphole 11 and 1,2-benzoazaarsole 12. NICS calculations revealed 11 and 12 had aromatic character on par with that of pyrazole-based 5.

The drive to develop maximal atom‐efficient catalysts coupled to the continuous striving for more sustainable reactions has led to an ever‐increasing interest in single‐atom catalysis. Based on a periodic conceptual density functional theory (cDFT) approach, fundamental insights into the reactivity and adsorption of single late transition metal atoms supported on a fully hydroxylated amorphous silica surface have been acquired. In particular, this investigation revealed that the influence of van der Waals dispersion forces is especially significant for a silver (98 %) or gold (78 %) atom, whereas the oxophilicity of the Group 8–10 transition metals plays a major role in the interaction strength of these atoms on the irreducible SiO2 support. The adsorption energies for the less‐electronegative row 4 elements (Fe, Co, Ni) ranged from −1.40 to −1.92 eV, whereas for the heavier row 5 and 6 metals, with the exception of Pd, these values are between −2.20 and −2.92 eV. The deviating behavior of Pd can be attributed to a fully filled d‐shell and, hence, the absence of the hybridization effects. Through a systematic analysis of cDFT descriptors determined by using three different theoretical schemes, the Fermi weighted density of states approach was identified as the most suitable for describing the reactivity of the studied systems. The main advantage of this scheme is the fact that it is not influenced by fictitious Coulomb interactions between successive, charged reciprocal cells. Moreover, the contribution of the energy levels to the reactivity is simultaneously scaled based on their position relative to the Fermi level. Finally, the obtained Fermi weighted density of states reactivity trends show a good agreement with the chemical characteristics of the investigated metal atoms as well as the experimental data.