Pentamethylcyclopentadienyl-rhodium and -iridium complexes. Part VI. π-Arene, π-cyclohexadienyl, and π-pyrrolyl complexes

Abstract

A new method for the preparation of π-arene and π-pyrrolyl complexes is described. The trifluoroacetates [M(C₅Me₅)(OCOCF₃)₂, H₂O](M = Rh, Ir) in trifluoracetic acid react with a variety of methylated benzenes to give [M(C₅Me₅)(arene)]²⁺. The π-arene complexes of Ir^III are more stable than those of Rh^III and their stability increases with increasing methylation. The complex [Rh(C₅Me₅)(p-xylene)]²⁺ undergoes rapid displacement of p-xylene by dimethyl sulphoxide to give [Rh(C₅Me₅)(Me₂SO)₃]²⁺. The π-arene complexes react with nucleophiles (NaBH₄, MeLi) to give π-cyclohexadienyl complexes where the attacking group becomes the exo-substituent. The π-pyrrolyl complexes [M(C₅Me₅)(C₄H₄N)]⁺ are obtained in high yield from the trifluoroacetates and do not react with nucleophiles under these conditions.