Au(I)-complexes ligated by hybrid P,S,N-ligands as the efficient catalysts for hydration of phenylacetylene

The incorporation of -PPh₂ group in the parent molecule of 1-(thiazol-2′-yl)-imidazole afforded the hybrid P,S,N-ligands of 1 and 2 respectively. The former was quarternized by MeOTf to give the ionic hybrid P,S-ligand of 1′. The single crystal X-ray diffraction analyses of the corresponding mono-nuclear Au(I)-complexes of 1A and 2A indicate that the Au(I)-centered vectors in each are in a slightly distorted linear configuration, in which Au(I) center is diagonally coordinated by one Cl^- and one phosphine without the coordinating interaction to N (or S)-donors. When the mono-nuclear Au(I)-complexes of 1A, 1′A, and 2A were employed as the catalysts for hydrations of phenylacetylene in aqueous-methanol media with the involvement of AgOTf and H₂SO₄, the reactions over 1A proceeded selectively according to Markovnikov's rule with much high yields of acetophenone than those over 1′A and 2A, indicating that the available additional S-, and N-donors in 1A with less steric hindrance synergetically protected the active Au(I)-complex species against deactivation during the catalytic cycle.