Is there a Covalent Au(I)–Au(I) Bond in the trans-(AuX)₂ (X = F, Cl, Br, I) Structure? A Post-Hartree–Fock and Density Functional Theory Study

Abstract

We present an exhaustive exploration of the driving forces dominating the interaction between gold atoms in the trans-(AuX) 2 , where X is a halogen ligand. This work provides insights into the nature of the gold−gold contact in the trans-(AuX) 2 . The geometries and energies were calculated at the MP2, CCSD(T), and DFT-D3(BJ) (B3LYP, PBE, and TPSS) levels of theory. The results show a short Au−Au distance, typical of a covalent bond, but with a weak interaction energy associated with noncovalent interactions. It is established that the physical contributions from polarization and the electronic correlation forces are the most relevant at the post-Hartree−Fock level of theory. Also, the electrostatic term is attractive but with low contribution. Finally, the Wiberg indices and NBO analysis exposed a small covalent character between the gold atoms, revealing that this contribution is insufficient to explain the stability of the dimers. It is concluded that a sum of contributions makes it possible to establish an attraction between the gold atoms in the dimers studied beyond a classical aurophilic interaction.

Unusually short unsupported Au(iii)⋯Au(iii) aurophilic contacts in emissive lanthanide tetracyanoaurate(iii) complexes

“…To further investigate whether the short Au( iii )⋯Au( iii ) contacts are the result of Au( iii ) aurophilicity or primarily a packing effect, ab initio calculations were conducted at the MP2 level using the def2TZVP basis set (details in ESI†). 28,43,44 To model the relativistic effect, a Douglas–Kroll–Hess 2nd order scalar relativistic correction was implemented. 45 A potential energy surface was constructed by varying the Au⋯Au distance between two [Au(CN) 4 ] − molecules, using the 1Lu crystal structure geometry.…”