Thio-iso-phthalamide Pincer Ligands Driven Oxidative Addition of a C-Br Bond to Gold(I): Synthesis and Studies of SCS-Gold(III) Pincer Complexes

Abstract

The chelating effect of thio-iso-phthalamide was utilized to facilitate the oxidative addition of the aryl Csp²-Br bond into the SMe₂Au(I)Cl salt, leading to the isolation of stable SCS·Au(III)X (X = Br, Cl) complexes. The subsequent displacement of bromide with silver triflate, followed by the addition of phosphine/phosphite ligands, afforded a series of neutral, highly stable organogold(III) complexes. The thioamide pincer ligand acts as a trianionic species due to iminothiolate formation. The isolated complexes were thoroughly characterized by NMR, mass spectrometry, IR spectroscopy, and single-crystal X-ray diffraction techniques. The redox potential of the complexes was measured by cyclic voltammetry, revealing that the reduction of Au(III) to Au(I) to Au(0) is an irreversible redox process. The pathway of gold(III) complex formation was investigated using DFT analysis, which suggested that the bi-chelation of the thioamide groups facilitated the oxidative addition of C-Br bonds to the Au(I) centre.