Lithium cyclopentadienide

Lithium cyclopentadienide is an organolithium compound with the formula C5H5Li. The compound is often abbreviated as LiCp, where Cp&minus; is the cyclopentadienide anion. Lithium cyclopentadienide is a colorless solid, although samples often are pink owing to traces of oxidized impurities.

Preparation, structure and reactions
Lithium cyclopentadienide is commercially available as a solution in tetrahydrofuran. It is prepared by treating cyclopentadiene with butyllithium:
 * C5H6 + LiC4H9 → LiC5H5 + C4H10

Because lithium cyclopentadienide is usually handled as a solution, the solvent-free solid is rarely encountered. According to X-ray crystallography, LiCp is a "polydecker" sandwich complex, consisting of an infinite chain of alternating Li+ centers sandwiched between μ-η5:η5-C5H5 ligands. In the presence of amines or ethers, LiCp gives adducts, e.g. (η5-Cp)Li(TMEDA). LiCp is a common reagent for the preparation of cyclopentadienyl complexes.