Silylium ion-like reagents, R3Si δ+(carboraneδ-), are successful where silver salts fail in abstracting chloride ion from IrCl(CO)(PPh3) 2 in arene solvents. Replacement of chloride by a very weakly coordinating carborane anion such as CHB11H5Cl 6- promotes unusually facile oxidative addition of chlprobenzene, giving the coordinatively unsaturated IrCl(CO)(C 6H5)(PPh3)2]+ cation. Other arene solvents promote disproportionation with loss of aphosphme ligand to give labile Ir(I) cations of the type [Ir(arene)(CO)(PPh3)] +, having three latent vacant coordination sites. © 2008 American Chemical Society.

Using carboranes as counterions, fluorinated benzyl-type carbocations such as (p-FC(6)H(4))(2)CF(+), (p-FC(6)H(4))(CH(3))CF(+) and fluorinated trityl ions are readily isolated for X-ray and IR structural characterization.

Si(mply) rips it apart: C-F activation of fluorobenzene has been achieved using the extremely strong silyl Lewis acids [Et3Si(X)]+ (X=PhF or Et3SiH) and [(2,6-dixylyl-C6H 3)SiMe2] + paired with the anion CHB 11Cl11-. They abstract fluoride from unactivated fluorobenzene to give arylated products, consistent with phenyl-cation-like reactivity (see scheme). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.