Thiophenyl and Benzothiophenyl Gold Isocyanide Complexes: Synthesis, Structures, Aurophilic and Gold-involving Chalcogen Bonding Interactions

Abstract

We report the synthesis, structural characterization, and theoretical analysis of a series of thiophenyl and benzothiophenyl gold(I) isocyanide complexes using air-stable boronic acids as precursors. Single-crystal X-ray diffraction revealed the formation of multiple polymorphic forms, including supramolecular dimers, tetramers, nonamers, and polymers, stabilized by aurophilic interactions. Detailed computational studies were performed to investigate the nature of these interactions, with a focus on identifying and characterizing Au···S contacts as potential chalcogen bonding interactions. Molecular electrostatic potential (MEP) surface analyses confirmed the presence of σ-holes at the sulfur atoms and nucleophilic character at the gold centers, supporting a donor–acceptor model of interaction. Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) analyses further corroborated the existence and energetic contributions of these noncovalent contacts. Aurophilic interactions were found to be the primary driving force for supramolecular assembly, while weaker Au···S contacts fine-tune the molecular organization.