Synthesis and reactivity of bimetallic Au–Ag polyfluorophenyl complexes; crystal and molecular structures of [{AuAg(C₆F₅)₂(SC₄H₈)}_n] and [{AuAg(C₆F₅)₂(C₆H₆)}_n]

The reaction of [NBun4][AuR2](R = C6F5 or C6F3H2-2,4,6) with Ag[ClO4] leads to complexes [{AuAgR2}n], which react with neutral ligands to give complexes [{AuAgR2L}n](L = neutral O-, N-, S- or P-donor ligand, alkene, or alkyne). For R = C6F5 and L = diphenylacetylene, the product is [{AuAgR2·0.5L}n]; the 0.5L can be displaced by other ligands, such as acetone, arenes, or alkenes, to reform [{AuAgR2L}n]. An X-ray diffraction study of [{AuAgR2L}n](R = C6F5, L = tetrahydrothiophene) reveals (AuAg)2 rings with Au–Ag 2.726 and 2.718 Å(the first reported Au–Ag bond lengths), linked by Au ⋯ Au short contacts (2.889 Å) to form infinite metal-atom chains. This complex crystallizes in space group Pccn, with a= 11.185(3), b= 22.475(6), c= 14.802(4)Å, Z= 8, R= 0.041 for 2 005 reflections. The complex [{AuAgR2L}n](R = C6F5, L = benzene) crystallizes in space group C2/c, with a= 24.231(5), b= 7.570(1), c= 22.613(5)Å, β= 117.49(2)°, Z= 8, and R= 0.035 for 3 008 reflections; it shows the same type of metal-atom chain (Au ⋯ Au 3.013; Au–Ag 2.702 and 2.792 Å). The benzene ring is co-ordinated by one edge to silver. In both structures the gold atoms lie on a crystallographic two-fold axis.