Polynuclear gold(I) complexes of functionalized thiols and dithiols

Treatment of 2-mercaptoaniline with {[(Ph₃P)Au]₃O)⁺ BFj leads to a regioselective auration to give the (2-aminophenyljsulfonium complex {{2-H₂NC₆H₄)S[Au(PPh₃)] ₂)⁺ BFJ (I) as the sole product. With the same reagent, 4-mercaptophenol affords the corresponding (4-hydroxyphenyl)sulfonium salt 2, and 2-mercaptopyridine is converted into the 2-pyridylsulfonium salt 3. Dinuclear auration of the thiol functions is thus clearly favoured over the reaction at any of the other functional groups (-NH2, -py, -OH). As shown in earlier work, this is also true for HS-functional carboxylic acids. With an excess of the oxonium reagent, however, 2-mercaptosuccinic acid was now found to be converted into a tetranuclear complex with a doubly aurated sulfonium group and monoau-rated carboxylate functions (4). Bis(2-mercaptoethyl) ether and thioether react with the oxonium salt to give tetranuclear bisfsulfonium salts) 5, 6, with bifurcated {-S[Au(PPh₃)]₂}⁺ groups at both ends. Structural studies of compounds 1, 5 and 6 showed the cations to be aggregated into centrosymmetrical dimers through short Au-Au contacts. Compound 5 forms one-dimensional infinite chains through a similar aggregation via the two bifurcated sulfonium end groups of each individual dicationic unit. The dications of compound 6 are associated only into centrosymmetrical dimers leaving one of the two sulfonium groups of each unit without auriophilic contacts to neighbouring dications, probably owing to an internal Au-S contact with the thioether function.