Types of Cyclopentadienyl Complexes

CHAPTER 3 COVALENT (x-TYPE) LIGANDS BOUND THROUGH METAL-CARBON AND METAL-HYDROGEN BONDS 

With a few exceptions,most tris(cyclopentadienyl) complexes contain lanthanides (Ln) or actinides as the central metal. CpjLn have polymeric structures, with chains of (ri -CpljLn units linked by cyclopentadienides that are bound in an T) -fashion toward one or both of the metals they bridge. Cp Ln and Cp U are monomeric. The Sm(III) complex has been prepared from Sm(II) and Cp jPb (Equation 3.83) the U(III) complex was prepared from the U(III) hydride and tetramethylfulvene (Equation 3.84).  

Many people consider the discovery in 1951 and subsequent characterization of Cp Fe to be the beginning of modem organotransition metal chemistry. Certainly, the binding of an aromatic group to a metal through the face of the ligand was a new bonding mode, and thousands of papers, and even commercial asymmetric catalytic processes, are based upon derivatives of ferrocene. 

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