Organometallic synthesis in ambient temperature chloroaluminate(III) ionic liquids. Ligand exchange reactions of ferrocene

Abstract

The ambient temperature ionic liquid system [bmim]Cl–AlCl₃ (where [bmim]⁺ = 1-butyl-3-methylimidazolium cation) has been used to prepare a number of arene(cyclopentadienyl)iron(II) complexes of the type [Fe(C₅H₅)(arene)]⁺ from ferrocene. The ionic liquid acts as both solvent and Lewis acid source ([Al₂Cl₇]^–). The products were only formed on addition of a proton source, [bmim][HCl₂], confirming mechanistic formulations involving a combination of Lewis and Brønsted acid activity. The X-ray crystal structure analysis of [Fe(η⁵-C₅H₅)(η⁶-C₆H₅C₆H₄Br)][PF₆] is also reported. The structure clearly shows both π–π stacking interactions between neighbouring cations and hydrogen bonds between the cations and anions.