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

Abstract

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).