Synthesis of Au(I) Trifluoromethyl Complexes. Oxidation to Au(III) and Reductive Elimination of Halotrifluoromethanes

Au­(I) trifluoromethyl complexes [Au­(CF₃)­L] (L = <i>N</i>-heterocyclic carbene (NHC), isonitrile, phosphine, P­(OMe)₃) and [Au₂(CF₃)₂­(μ-dppe)] are prepared by reaction of [Au­(X)­L] (X = Cl, I) or [Au₂Cl₂­(μ-dppe)], respectively, with AgF and Me₃SiCF₃. The analogous reaction of PPN­[Au­(C₆F₅)­Cl] (PPN⁺ = [Ph₃PNPPh₃]⁺) gives a mixture of complexes of the type PPN­[Au­(CF₃)_<i>x</i>­(C₆F₅)_2–<i>x</i>] (<i>x</i> = 0, 1, 2). Single crystals of the new complex PPN­[Au­(CF₃)­(C₆F₅)] are obtained by liquid diffusion from this mixture, and its crystal structure was determined by X-ray diffraction. Acyclic diaminocarbene complexes [Au­(CF₃)­{C­(NEt₂)­(NHR)}] (R = ^<i>t</i>Bu, 2,6-dimethyl­phenyl) are obtained by reaction of [Au­(CF₃)­(CNR)] with NHEt₂. Oxidation of the NHC complex [Au­(CF₃)­(IPr)] (IPr = 1,3-bis­(2,6-diiso­propyl­phenyl)­imidazol-2-ylidene) with PhICl₂, Br₂, I₂ or ICl affords [Au­(CF₃)­(X)­(Y)­(IPr)] (X = Y = Cl, Br I; X = Cl, Y = I). The dicloro, dibromo, and chloro­(iodo) complexes are stable in solution in the dark. In contrast, the diiodo complex is unstable and decomposes to [AuI­(IPr)] and ICF₃. Under photoirradiation, complexes [Au­(CF₃)­(X)­(Y)­(IPr)] undergo reductive elimination to give YCF₃ and [AuX­(IPr)] (X = Y = Cl, Br; X = Cl, Y = I)