Studies on some selective and competitive substitution reactions of cyclopentadienyliron complexed chloronitrobenzenes with amines as nucleophiles

Nucleophilic substitution reactions of the (η6-o-, -m-, or -p-chloronitrobenzene)(η5-cyclopentadienyl)iron cation (2a, 2b, or 2c, respectively) with aniline, n-butylamine, or pyrrolidine as nucleophile were investigated. It was found that only selective displacement of the nitro group occurred for reactions with aniline. For reaction with n-butylamine or pyrrolidine, o-isomer 2a resulted in the selective displacement of only the chloro group, giving rise to the (η6-o-n-butylaminonitrobenzene)(η5-cyclo-pentadienyl)iron cation (5a) or the (η6-o-nitro-N-pyrrolidinylbenzene)(η5-cyclopentadienyl)iron cation (7a), respectively. With the m- or p-isomer 2b or 2c, reaction with n-butylamine or pyrrolidine gave a mixture of substitution products from competitive displacements of both chloro and nitro groups, the major product from the m-isomer being derived from displacement of the chloro group while the major product from the p-isomer resulted from displacement of the nitro group. Possible interpretations of these results on the basis that the basicity of the nucleophile and the combined inductive effects of the nitro and chloro substituents would play important roles are presented. Keywords: (η6-o-, -m-, and -p-chloronitrobenzene)(η5-cyclopentadienyl)iron cations, nucleophilic substitution reactions, aniline, n-butylamine, pyrrolidine.