Anion⋅⋅⋅Anion Coinage Bonds: The Case of Tetrachloridoaurate

Abstract

Interactions in crystalline tetrachloridoaurates of acetylcholine and dimethylpropiothetine are characterized by Au⋅⋅⋅Cl and Au⋅⋅⋅O short contacts. The former interactions assemble the AuCl4− units into supramolecular anionic polymers, while the latter interactions append the acetylcholine and propiothetine units to the polymer. The distorted octahedral geometry of the bonding pattern around the gold center is rationalized on the basis of the anisotropic distribution of the electron density, which enables gold to behave as an electrophile (π‐hole coinage‐bond donor). Computational studies prove that gold atoms in negatively charged species can function as acceptors of electron density. The attractive nature of the Au⋅⋅⋅Cl/O interactions described here complement the known aurophilic bonds involved in gold‐centered interactions.

σ-Hole Interactions Involving a Group 7 Metal: Close Contacts in Neutral and Anionic Rhenium Derivatives

“…Interestingly, the rhenium atom of a perrhenate unit engages in a short contact with a nucleophile (in most cases an oxygen atom) in 123 systems, corresponding roughly to 25% of the total (the van der Waals radius used to calculate this statistic is 2.05 Å). 36 Of note, these contacts have been recently rationalized as σ-hole interactions 29 similarly to those described above for neutral HReO 4 derivatives. While the data set may be too limited to make statistically meaningful generalizations, it may be worth mentioning that in these systems the mean value for the O− Re•••O angle is 165.78°, close to linearity.…”

“…The interaction is linear (the computed O−Re•••N angle is 180.0°), fully consistent with an attractive σ-hole interaction involving a group 7 metal acting as the electrophilic site, which was recently named a matere bond (MaB). 29 A common criterion for characterizing noncovalent interactions is that the interatomic separation be less than the sum of the van der Waals radii of the respective atoms. Under this light, the normalized contact (Nc) is a useful tool to evaluate noncovalent interactions as it allows for a meaningful comparison of interactions involving different atomic species.…”

“…In this context, recently some of us investigated the propensity of group 7 elements in forming σ-hole interactions. 29 In detail, crystallographic and theoretical investigations focused on studying the nature of short contacts at rhenium in ReO 4 − . 29 Even more recently, Gomila and Frontera have investigated three case studies from the Cambridge Structural Database (CSD), showing the similarity between σhole bonds involving rhenium and those involving hypervalent chalcogen and halogen bonds.…”

“…29 In detail, crystallographic and theoretical investigations focused on studying the nature of short contacts at rhenium in ReO 4 − . 29 Even more recently, Gomila and Frontera have investigated three case studies from the Cambridge Structural Database (CSD), showing the similarity between σhole bonds involving rhenium and those involving hypervalent chalcogen and halogen bonds. 30 In this Article, we focus on close contacts involving a variety of neutral perrhenate molecules, specifically focusing on the computed interaction energies associated with some of these.…”

Anion···Anion [AuI4]−···[AuI2]− Complex Trapped in the Solid State by Tetramethylammonium Cations

“…More recently, such approach has been extended to rationalize interactions involving post-transition metals (groups 11 6 and 12 7 ) and also other groups of the d-block of elements. For instance, theoretical and experimental evidence has been recently reported for elements of groups 7 8 (matere bonds) and 8 9 (osme bonds).…”