A Trinuclear Au I Complex with Different R 3 P–Au Centers: Synthesis, Characterization, and Synergetic Catalysis for Hydration of Phenylacetylene

Abstract

A trinuclear AuI complex (3A) was synthesized and fully characterized relative to mononuclear (1A) and dinuclear (2A) complexes. The single-crystal X-ray diffraction analyses show that the AuI-centered vectors in each of the AuI complexes (1A–3A) are all in a slightly distorted linear configuration, in which the AuI center is diagonally coordinated by one Cl– and one phosphine ligand. In 3A each P–Au–Cl vector is radially attached to the core of 1-(thiazol-2′-yl)imidazolyl, which does not allow the short contact between the Au atoms to develop an aurophilic AuI–AuI interaction. Every P–Au–Cl moiety in 3A is different to each other in terms of Au–P and Au–Cl bond lengths, P–Au–Cl bond angles, and P–Au–Cl configurable orientation owing to the different coordinating ability of the involved phosphines. When 1A–3A were employed as the precatalysts for the hydration of phenylacetylene in aqueous methanol media without the involvement of any auxiliary additive, and at the same benchmark Au concentration, the reaction over 3A proceeded selectively according to Markovnikov's rule with the highest yield of acetophenone relative to those over 2A and 1A. This indicates that the catalytic performance of 3A is the outcome of the synergetic effect of the three different R3P–Au centers, in which each R3P–Au site plays an individual role in activating the substrate molecule.