P,N-Chelated Gold(III) Complexes: Structure and Reactivity

Gold­(III) complexes are versatile catalysts offering a growing number of new synthetic transformations. Our current understanding of the mechanism of homogeneous gold­(III) catalysis is, however, limited, with that of phosphorus-containing complexes being hitherto underexplored. The ease of phosphorus oxidation by gold­(III) has so far hindered the use of phosphorus ligands in the context of gold­(III) catalysis. We present a method for the generation of P,N-chelated gold­(III) complexes that circumvents ligand oxidation and offers full counterion control, avoiding the unwanted formation of AuCl₄^–. On the basis of NMR spectroscopic, X-ray crystallographic, and density functional theory analyses, we assess the mechanism of formation of the active catalyst and of gold­(III)-mediated styrene cyclopropanation with propargyl ester and intramolecular alkoxycyclization of 1,6-enyne. P,N-chelated gold­(III) complexes are demonstrated to be straightforward to generate and be catalytically active in synthetically useful transformations of complex molecules.