[2,4,6-tris(trifluoromethyl)phenyl]gold(I) and -gold(III) complexes

The complex [Au(Fmes)(tht)] (Fmes = 2,4,6-tris(trifluoromethyl)phenyl or nonafluoromesityl; tht = tetrahydrothiophene) was obtained by reaction of [AuCl(tht)] and Li(Fmes). Monoarylated complexes are readily obtained when the tht ligand is displaced by other neutral ligands, giving [Au(Fmes)L] (L = PPh3, P(o-tol)(3), 2,6-lutidine) or [Au(2)Fmes)(2)(mu-bipy)] (bipy = 2,2'-bipyridyl), the latter containing a bridging bipy ligand. tht can also be displaced by halides to give the gold anionic complexes NBu4[Au(Fmes)X] (X = Cl, Br, I). [Au(Fmes)(NCMe)] is obtained from the latter by treatment with TlBF4 in the presence of MeCN. The bis-arylated complexes NR4[Au(Fmes)(2)] (R = Et, Bu) were obtained by treatment of NR4[AuBr2] with excess Li(Fmes). They react with AgBF4 and 4-methylpyridine to give [Ag(4-Mepy)(2)][Au(Fmes)(2)]. Oxidative addition of halogens to the monoarylated NBu4[Au(Fmes)X] and the bis-arylated NR4[Au(Fmes)(2)] gives the gold(III) complexes NBu4[Au(Fmes)X-3] and NR4[trans-Au(Fmes)(2)X-2], respectively. The structures of the bis-arylated gold(I) and -(III) complexes NBu4[Au(Fmes)(2)] and NEt4[trans-Au(Fmes)(2)I-2] were determined by X-ray diffraction. An analysis of nonbonded distances and torsion angles suggests that steric repulsion of neighboring CF3 groups is reduced by mutual rotation of the Fmes rings in the former complex but by rotation of the CF3 groups themselves in the latter (in which the Fmes rings are exactly coplanar).