Cyclopentadienyl complexes

This chapter evaluates cyclopentadienyl complexes. In 1948, Miller, Tebboth, and Tremaine, attempting to synthesize amines from olefins and nitrogen in the presence of iron catalysts, found that with cyclopentadiene, an iron-containing compound was formed. The new compound, bis-(cyclopentadienyl)iron, was named ‘ferrocene’ in the realization that it behaves much like a three dimensional arene. Soon afterwards, a whole series of bis-(cyclopentadienyl)metal complexes were prepared; by analogy these have become known as metallocenes. The chapter then looks at the synthesis of metallocenes and bonding in metallocene complexes, as well as the properties of metallocenes and bent sandwich complexes. It also considers cyclopentadienyl as a non-spectator ligand, studying ring slippage and fluxionality. Finally, the chapter explores mono-cyclopentadienyl (half-sandwich) complexes.