On the Nature of the Bonding in Coinage Metal Halides

Abstract

This article analyzes the nature of the chemical bond in coinage metal halides using high-level ab initio Valence Bond (VB) theory. It is shown that these bonds display a large Charge-Shift Bonding character, which is traced back to the large Pauli pressure arising from the interaction between the bond pair with the filled semicore d shell of the metal. The gold-halide bonds turn out to be pure Charge-Shift Bonds (CSBs), while the copper halides are polar-covalent bonds and silver halides borderline cases. Among the different halogens, the largest CSB character is found for fluorine, which experiences the largest Pauli pressure from its σ lone pair. Additionally, all these bonds display a secondary but non-negligible π bonding character, which is also quantified in the VB calculations.

On the nature of inter-anion coinage bonds

“…Elucidating the nature of chemical bonds involving transition metals is also challenging due to their specific electronic structures. [76][77][78][79][80][81][82][83][84] The history of CiBs may date back to the year 2000, when the Gerry lab studied the microwave spectra of RgÁ Á ÁM-X complexes, where Rg, M and X stand for rare gas, group 11 and halogen atoms respectively. [85][86][87][88][89][90] Complexes formed between M-X and a series of Lewis bases have been determined in experimental studies ever since.…”

“…Elucidating the nature of chemical bonds involving transition metals is also challenging due to their specific electronic structures. 76–84…”

Synthesis, structural studies, and photophysical properties of heteroleptic inverse-coordination clusters

“…Understanding the nature of coinage metal and halide interactions is of crucial significance. 15 Most coinage metal halides are considered to have ionic bonding properties, but specific gold halides have been credited with more substantial covalent bonding properties. 16 Moreover, there has been increasing interest in figuring out how a coinage metal and halide within molecules stick together in an assortment of non-covalent interactions, such as van der Waals interactions.…”

Equivalent and Complement of the ω-Bonding Model and Charge-Shift Bonding Model: A Natural Bond Orbital/Natural Resonance Theory/Atoms in Molecules Investigation via Cu/Ag/Au Bonding in BMX (B = H2O, H2S, NH3, and PH3; M = Cu, Ag, and Au; and X = F, Cl, Br, and I)

“…Therefore, further testing is necessary to establish its validity across more cases. Here, we take free MX as an example, because the CS nature of the M–X bond has been identified by Shaik et al in the VB theory . The calculated results of ρ­( r ) and ∇ 2 ρ­( r ) for Cu–X, Ag–X, and Au–X bonds in free MX are presented in panels d, e, and f of Figure , respectively.…”

“…However, we anticipate that CS bonding should also be important in understanding Cu/Ag/Au bonding based on some studies by Shaik et al. − The CS bond belongs to a new class of chemical bonds, emerging from the valent bond (VB) theory, and it is supported by the atoms in molecules (AIM) theory. − Since 1992, this model has been successfully applied to understand the bonding in diatomic halogen molecules (e.g., F 2 ), hypermolecules (e.g., Cl 3 – and XeF 2 ), , transition metal species (e.g., Au 2 and MX), , etc. Our recent study on xenon hydrides using NBO/NRT analyses demonstrated that the H–Xe bonds in all studied molecules exhibit a CS bonding character .…”