The Conformational Study of (Substitututed phenyl)ferrocenes by the Method of ¹H-NMR

Abstract

The preferential conformation of (o-substituted phenyl)ferrocenes were discussed by the method of 'H-NMR. On (o-hydroxy- and o-alkylphenyl)ferrocene, the bond between phenyl group and cyclopentadienyl group as twisted and steric conformation in which the substituent was situated on the endo position (Fig.2 and 4) was preferred. In the case of (o-chloroand o-nitrophenyl)ferrocene, exo position was preferred. On the other hand, the preferential conformation of (2-chloro-6-methyl- and 2-methyl-6-nitrophenyl)ferrocene was assumed to be twisted as well as (o-substituted phenyl)ferrocenes. But in the preferential conformation of (2, 6-dimethylphenyl)ferrocene, the steric hindrance was, avoided. by vent of bond angle between phenyl group and cyclopentadienyl group (Fig.5). The driving forces were considered as follows: (i) van der Waals repulsion between a-proton in cyclopentadienyl group and ortho-substituent (ii) interaction between the d electrons of iron atom in ferrocene and ortho-substituent.