Substituent Effect on Oxidative Decomposition of Acylferrocenes

Yutaka Okada,Motoi Sakai

doi:10.5539/ijc.v11n2p31

Abstract

Acylferrocenes are oxidized by iron(III) chloride in methanol and then immediately decomposed. In this study, the oxidative decomposition of some alkanoyl- and aroylferrocenes was performed and the substituent effect on the reaction rate was investigated. It was found that the reaction was governed by the accessibility of the oxidizing agent to the iron atom and the degree of electron-withdrawing effect of the carbonyl group towards the ferrocene nucleus.

Highlights

In recent years, ferrocenes have been extensively studied as catalysts in asymmetric synthesis and as functional materials (Zora, Kokturk, & Eralp, 2006)(Zora, Tumay, & Bueyuekguengoer, 2007)
It was found that the reaction was governed by the accessibility of the oxidizing agent to the iron atom and the degree of electron-withdrawing effect of the carbonyl group towards the ferrocene nucleus
When acylferrocenes are reacted in methanol under the same conditions, the color of the reaction solution changes to pale purple, rather than blue, indicating that this reaction proceeds via a mechanism different from that in the earlier case (Okada, & Hayashi, 1989)

Summary

Introduction

Ferrocenes have been extensively studied as catalysts in asymmetric synthesis and as functional materials (Zora, Kokturk, & Eralp, 2006)(Zora, Tumay, & Bueyuekguengoer, 2007). Under acidic conditions, it is oxidized in air, resulting in a blue-colored ferrocenium ion. When alkyl ferrocenes are reacted in 1,2-dichloroethane in the presence of trichloroacetic acid, the color of the reaction solution changes from yellow to blue, indicating the generation of the ferrocenium ion (Scheme 1 (a)). When acylferrocenes are reacted in methanol under the same conditions, the color of the reaction solution changes to pale purple, rather than blue, indicating that this reaction proceeds via a mechanism different from that in the earlier case (Okada, & Hayashi, 1989). Fe3+, which is a strong oxidizing agent, oxidizes the iron atom in the ferrocene nucleus In other words, this step is the oxidation reaction of ferrocenes by Fe3+ (Scheme 1(b)). The ferrocene nucleus decomposes, so that the intensity of the fourth band absorption decreases (Scheme 2) (Hayashi, Okada, & Hukuchi, 1994)

Methods

Results

Conclusion