text: The compounds are generally prepared by salt metathesis reactions of alkali-metal cyclopentadienyl compounds with transition metal chlorides.  Sodium cyclopentadienide (NaCp) and lithium cyclopentadienide are commonly used. Trimethylsilylcyclopentadiene cyclopentadienylthallium (CpTl) are alternative sources.  For the preparation of some particularly robust complexes, e.g. nickelocene, cyclopentadiene is employed in the presence of a conventional base such as KOH. When only a single Cp ligand is installed, the other ligands typically carbonyl, halogen, alkyl, and hydride.
  Most Cp complexes are prepared by substitution of preformed Cp complexes by replacement of halide, CO, and other simple ligands.