Benchmark studies on the large errors of calculated binding energies in metallophilic interactions

Anisotropic Metal-Metal Pauli Repulsion in Polynuclear d10 Metal Clusters

Metallophilicity has been widely considered to be the driving force for self-assembly of closed-shell d10 metal complexes, but this view has been challenged by recent studies showing that metallophilicity in linear d10-d10 dimers is repulsive. This is due to strong metal-metal (M-M') Pauli repulsion (Wan, Q., Proc. Natl. Acad. Sci. U. S. A. 2021, 118, e2019265118). Here, we study M-M' Pauli repulsion in d10 metal clusters. Our results show that M-M' Pauli repulsion in d10 polynuclear clusters is 6-52% weaker than in similar linear d10 complexes due to the anisotropic shape of (n+1)s-nd hybridized orbitals. The overall M-M' interactions in closed-shell d10 polynuclear metal clusters remain repulsive. The effects of coordination geometry, relativistic effects, and the ligand's electronegativity on M-M' Pauli repulsion in polynuclear d10 clusters have been explored. These findings provide valuable guidance for the design and development of ligands and coordination geometries that alleviate M-M' Pauli repulsion in d10 metal cluster systems.

Deciphering the Primary Role of Au⋅⋅⋅H-X Hydrogen Bonding in Gold Catalysis

Au⋅⋅⋅H-X (X=N or C) hydrogen bonding is gaining increasing interest, both in the study of its intrinsic nature and in their operability in different fields. While the role of these interactions has been studied in the stabilization of gold(I) complexes, their role during the minimum free energy reaction pathway of a given catalytic process remains unexplored. We report herein that complex [Au(C≡CPh)(pip)] (pip=piperidine) catalyses the A3 -coupling reaction for the synthesis of propargylamines, thanks to the ability of Au(I) to promote weak hydrogen bonding interactions with the reactants along the free energy profile. Density Functional Theory (DFT) calculations show that these Au⋅⋅⋅H-X interactions play a directing role in the catalysed A3 -coupling. Topological non-covalent interactions (NCI), interaction region indicator (IRI) and quantum theory of atoms in molecules (QTAIM) analysis in real space of the electron density provide a description of these interactions accurately.

Dynamic Au-C σ-Bonds Leading to an Efficient Synthesis of [n]Cycloparaphenylenes (n = 9-15) by Self-Assembly

The transmetalation of the digold(I) complex [Au₂Cl₂(dcpm)] (1) (dcpm = bis(dicyclohexylphosphino)methane) with oligophenylene diboronic acids gave the triangular macrocyclic complexes [Au₂(C₆H₄) _x (dcpm)]₃ (x = 3, 4, 5) with yields of over 70%. On the other hand, when the other digold(I) complex [Au₂Cl₂(dppm)] (1') (dppm = bis(diphenylphosphino)methane) was used, only a negligible amount of the triangular complex was obtained. The control experiments revealed that the dcpm ligand accelerated an intermolecular Au(I)-C σ-bond-exchange reaction and that this high reversibility is the origin of the selective formation of the triangular complexes. Structural analyses and theoretical calculations indicate that the dcpm ligand increases the electrophilicity of the Au atom in the complex, thus facilitating the exchange reaction, although the cyclohexyl group is an electron-donating group. Furthermore, the oxidative chlorination of the macrocyclic gold complexes afforded a series of [n]cycloparaphenylenes (n = 9, 12, 15) in 78-88% isolated yields. The reorganization of two different macrocyclic Au complexes gave a mixture of macrocyclic complexes incorporating different oligophenylene linkers, from which a mixture of [n]cycloparaphenylenes with various numbers of phenylene units was obtained in good yields.