[{Au(NHC)}2(μ-OH)][BF4]: Silver-Free and Acid-Free Catalysts for Water-Inclusive Gold-Mediated Organic Transformations

The synthesis of a series of digold hydroxide complexes is reported. These diaurated species, of the formula [{Au(NHC)}2(μ-OH)][BF4] (where NHC = IPrCl, IPr*, IPent), were easily prepared via the cationic species [Au(NHC)(NCCH3)][BF4] in aqueous media. The catalytic activity of these novel complexes was tested and compared to that of the previously reported IPr and SIPr derivatives. These digold hydroxide species are highly active in water-inclusive organic transformations, such as the alkyne and nitrile hydration reactions, and the Meyer–Schuster rearrangement. One salient feature of these systems is the lack of any additive to induce catalytic activity.