POLYNUCLEAR GOLD(I) COMPLEXES OF MERCAPTOCARBOXYLIC ACIDS

In a search for air-stable and water-soluble mercapto compounds of gol d with a high gold content, benzylthiol, alpha-mercapto-acetic acid, b eta-mercapto-propionic acid, and thiosalicylic acid were converted int o aurated sulfonium salts by treatment with reagents of the type [(R(3 )P)Au]O-3(+) BF4- or [(R(3)P)Au](+) BF4-. -BzSH served as a mono-funct ional model thiol, which was converted into BzS[Au(PMe(3))](2+) BF4- ( 1). The small tertiary phosphine was chosen in order to minimize steri c effects. In the crystal the cations are associated into centrosymmet rical dimers through short Au-Au contacts (auriophilicity). - The two carboxylic acids with thiol functions, HSCH2COOH and HSCH2CH2COOH, gav e triply aurated species of the type {[(Ph(3)P)Au]S-2(CH2)(n)COOAu(PPh (3))}(+) BF4- (2: n = 2, 3: n = 3). The crystal structure analysis sis of the representative compound 2 showed again the presence of centros ymmetrical cation dimers with geometrical details of the sulfonium par t of the molecules very similar to those of the reference compound 1. In addition, the carboxyl groups in 2 and 3 bear a (phosphine)gold uni t mono-hapto bound at one of the oxygen atoms. -2-HS-C6H4-COOH was con verted into a sulfonium salt {[(Ph(3)P)Au]S-2-C6H4-COOH}(+) BF4- (4). which crystallizes free of solvent from dry dichloromethane, and as a monohydrate with one mole of dichloromethane (4a = 4 . H2O . CH2Cl2) f rom hydrous CH2Cl2. In the solvent-free crystalline phase (4) the cati ons are associated into dimers with the usual intermolecular double Au -Au contacts, but in 4a there are monomeric cations with the water mol ecule hydrogen-bonded to the carboxylic acid function.