An Unprecedented Phosphinamidic Gold(III) Metallocycle: Synthesis via Tin(IV) Precursors, Structure, and Multicomponent Catalysis

A straightforward method of synthesizing cycloaurated gold(III) phosphinamide-based molecules starting from their ortho-tin(IV) derivatives in excellent yields is described. The structure of the tin and gold complexes has been investigated by multinuclear magnetic resonance (1H, 13C, 15N,31P, 119Sn) and single-crystal X-ray diffraction. In solution and in the solid state the ortho-functionalized phosphinamide moiety acts as a new C−C−P−O pincer ligand with formation of asymmetric five-membered ring metallocycles. Intramolecular PO coordination to tin(IV) leads to a distorted trigonal-bipyramid configuration for the metal, while in the gold(III) metallocyclic complex the metal shows a square-planar geometry. The new Au(III) complex has been applied in multicomponent (A3) coupling processes, providing a variety of propargylamines in quantitative yields under very mild conditions without the use of any activator or additive. Diffusion NMR studies showed that the catalyst is present as a monomer in acetonitrile solution, while a slight charge-induced aggregation seems to take place in chloroform.