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DOI:10.1002/anie.201100095

24 Recent Progress in Organometallic Chemistry

RS]<sup>2</sup>

[NO]<sup>4</sup>

nprot.2007.22

DOI:10.1021/ic0607336

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.68952

#### **Abstract**

[μ-

[tpm]]+-

A special class of sandwich complexes is the metallocenes. The best-known members are the metallocenes of the formula M(C5 H5 )2 , where M = zirconium, zinc, titanium, hafnium, vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, osmium, cobalt, rhodium, and nickel. Besides the two cyclopentadienyl rings, the metal can have additional ligands depending on its valence state. These species are also called bis(cyclopentadienyl)metal complexes. Bis(cyclopentadienyl) complexes are called metallocenes or sandwich compounds. Metal-centred radical and cyclopentadienyl radical structures can occur in the metallocene. The anion and cation radicals can also be formed by charge transfer transition.

**Keywords:** metallocenes, sandwich compound, organometallic compounds, cyclopentadienyl complex, π-complexes, σ-complexes, ionic complexes
