Arene Displacement Reactions of (η⁶−Arene)chromium(0) Carbonyl Compounds

Abstract

The development of organometallic chemistry over the past 25 years has led to extremely selective catalytic systems and to a greater understanding of their mechanisms. One area of particular interest has been the study of hydrogenation reactions (e.g. dienes to monoenes) using (η⁶−arene)tricarbonylchromium(0) complexes as catalysts. ^1–4 The possibility of the catalytic liberation of functionalized arenes from the chromium centers in such compounds has also attracted the attention of synthetic organic chemists.⁵−⁶

The mechanisms involved in catalytic hydrogenation by (η⁶−arene)tricarbonylchromium compounds are only just becoming understood despite the fact that these reactions have been investigated since the early sixties. The first step is believed to be partial (or complete) displacement of the arene ring from the chromiummetal center.¹−⁷ Moreover, the catalytic rate is highly dependent on the nature of the arene involved, i.e. on the strength of the arene-Cr bond.² In this Comment, the work that has been reported on arene displacement reactions of (η⁶−arene)chromium(0) carbonyl compounds is discussed together with its relevance to the mechanism of catalytic hydrogenation.