Anion···Anion Coinage Bond: the Case of Tetrachloridoaurate.

The interactional landscape in crystalline tetrachloridoaurates of acetylcholine and dimethyl-propiothetine is characterized by Au ∙∙∙ Cl and Au ∙∙∙ O short contacts. Former interactions assemble the AuCl 4 - units into supramolecular anionic polymers, and latter interactions append the acetylcholine and propiothetine units to the polymer. The distorted octahedral geometry of the bonding pattern around gold is rationalized based on the anisotropic distribution of the electron density enabling gold to behave as an electrophile (π-hole coinage bond donor). Computation proves that gold in negatively charged species can function as acceptor of electron density. The attractive nature of Au ∙∙∙ Cl/O interactions described here complement aurophilic bonds in the toolbox of gold centered interactions.