[{Au(IPr)}₂(μ-OH)]X complexes: Synthetic, structural and catalytic studies

The synthesis of a series of dinuclear gold hydroxide complexes has been achieved. These complexes of type [{Au(IPr)}₂(Iμ-OH)]X (X=BF ₄, NTf₂, OTf, FABA, SbF₆; IPr=2,6- bis(disopropylphenyl)imidazol-2-ylidene; NTf₂= bis(trifluoromethanesulfonyl)imidate; OTf=trifluoromethanesulfonate; FABA=tetrakis(pentafluorophenyl)borate) are easily formed in the presence of water and prove highly efficient in the catalytic hydration of nitriles. Their facile formation in aqueous media suggests they are of relevance in gold-catalyzed reactions involving water. Additionally, a series of [Au(IPr)(NCR)][BF₄] (R=alkyl, aryl) complexes was synthesized as they possibly occur as intermediates in the catalytic reaction mechanism. ¹H and ¹³C NMR data as well as key bond lengths obtained by X-ray diffraction studies are compared and reveal an interesting structure-activity relationship. The collected data indicate a negligible effect of the nature of the nitrile on the reactivity of [Au(L)(NCR)][X] complexes in catalysis.