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

Au­(I) trifluoromethyl complexes [Au­(CF3)­L] (L = N-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)x­(C6F5)2–x] (x = 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 = tBu, 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).