Synthesis and characterization of new perfluoroalkylated side-chain ferrocenes and ferricinium salts

Abstract

The synthesis and characterization of various mono- and 1,1′-bis-[ ω-( F-alkyl)acyl]ferrocenes, 1,1′-bis-[ ω-( F-alkyl)alkyl]ferrocenes and 1,1′-bis-[ ω-( F-alkyl)- α-(hydroxy)-alkyl]ferrocenes are described (where F-alkyl denotes perfluoroalkylation). The [( F-alkyl)acyl]ferrocenes were obtained by Friedel-Crafts acylation of ferrocene with ( F-alkyl)acyl chlorides. The ( F-alkyl)alkyl and ( F-alsyl)- α-(hydroxyl)alkyl analogues were selectively prepared by reduction of the acyl derivatives with LiAlH 4AlCl 3 and LiAlH 4 respectively. These reactions illustrate the chemical inertness of ( F-alkyl)acyl and ( F-alkyl)alkyl chains under strongly reducing conditions. When the acylation of ferrocene was performed with ω-[2-( F-alkyl)ethenyl]acyl chlorides, acylferrocenes were obtained but their side chains contained the (Z)CFCHCH(CL)- sequence. Formation of these chains resulted from a highly stereospecific (E)CF 2CHCH- to (Z)CFCHCH(Cl) transformation, which involves an FCl exchange and a double-bond migration in the [2-( F-alkyl)ethenyl]acyl chain. The 1,1′-bis-[11-( F-alkyl)undecanoy]ferrocenes were found to be most effectively oxidized to the corresponding ferricinium species by HBF 4- p-benzoquinone, while their hydrocarbon analogue, 1,1′-bis-[undecanoy]ferrocene underwent a Michael addition to give benzofuranylferrocenes.