Abstract
The discovery of ferrocene (dicyclopentadienyliron) in 1951 [92,133] has provided access to the fascinating chemistry of a class of organo-metallic compounds commonly called metallocenes. This class, in the generally accepted terminology, comprises transition metal complexes with one or more π-cyclopentadienyl ligands; in a somewhat broader sense, complexes with other π-bonded aromatic ring systems as ligands may be included in this classification. The challenging synthetic and structural possibilities of the metallocenes, coupled with a highly attractive technological potential in areas such as radiation protection, combustion catalysis, rubber vulcanization, polymerization acceleration, and in a variety of reduction-oxidation reactions, have spurred considerable research activities, which are documented in an abundance of publications in the scientific, patent, and government report literature.