Many transition metals have been applied as catalysts for organic reactions [1].
So far, iron has not played a dominant role in catalytic processes. Organoiron
chemistry was started by the discovery of pentacarbonyliron in 1891, independently
by Mond [2] and Berthelot [3]. A further milestone was the report of
ferrocene in 1951 [4]. Iron catalysis came into focus by the Reppe synthesis [5].
Kochi and coworkers published in 1971 their results on the iron-catalyzed crosscoupling
of Grignard reagents with organic halides [6]. However, cross-coupling
reactions became popular by using the late transition metals nickel and palladium.
More recently, the increasing number of reactions using catalytic amounts of iron
complexes indicates a renaissance of this metal in catalysis. This chapter describes
applications of iron complexes in organic chemistry and thus paves the way for an
understanding of iron catalysis.