Mesitylgold(I) and silver(I) perfluorocarboxylates as precursors of supramolecular Au/Ag systems

Abstract

Reaction of [Ag(CF3CO2)] with tetrahydrothiophene (tht) (2:1) in dichloromethane leads to the synthesis of [Ag4(CF3CO2)4(tht)2] (1), which further reacts with mesitylgold(I) ([Au(mes)]) (1:1) to afford [AuAg4(mes)(CF3CO2)4(tht)]n (3). Treatment of [Au(mes)] with [Ag(RCO2)] (R = CF3, CF2CF3) and tht (molar ratio 1:4:1 or 1:4:3) leads to the new Au/Ag systems [AuAg4(mes)(RCO2)4(tht)x]n (x = 1, R = CF3 (3), CF2CF3 (4); x = 3, R = CF3 (5), CF2CF3 (6)). The crystal structures of 3, 4, and 6 have been established by X-ray diffraction, all of them displaying Au···Ag interactions supported by mesityl ligands that bridge three metal centers in an unprecedented situation in transition metal chemistry. Additional Au−S−Ag and Ag−O−Ag (3 and 4) or Ag−S−Ag (6) bonds result in two-dimensional polymers that contain both Au···Ag and Ag···Ag contacts. Treatment of 3 with water (1:2) in dichloromethane leads to {[AuAg4(mes)(CF3CO2)4(tht)(H2O)]·H2O·CH2Cl2}n (7), whose crystal structure shows the partial break of the cyclic [Ag2(μ-RCO2)2] dimer present in the structures of 3, 4, and 6, probably caused by the coordination of one molecule of water to one of the AgI centers. It also displays Au···Ag and Ag···Ag interactions, as well as Ag−C bonding interactions and additional Ag−O contacts, which result in a monodimensional polymer. The crystal structure of 1 has also been determined by X-ray diffraction.