Lithium cyclopentadienide explained

Lithium cyclopentadienide is an organolithium compound with the formula C₅H₅Li. The compound is often abbreviated as LiCp, where Cp^- 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:^[1]

C₅H₆ + LiC₄H₉ → LiC₅H₅ + C₄H₁₀Because 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.^[2] In the presence of amines or ethers, LiCp gives adducts, e.g. (η⁵-Cp)Li(TMEDA).^[1] LiCp is a common reagent for the preparation of cyclopentadienyl complexes.

See also

• Sodium cyclopentadienide

Notes and References

1. Revealing Coordination Patterns in C₅-Cyclic Lithium Organics. Reent Michel . Regine Herbst-Irmer . Dietmar Stalke . Organometallics. 2011. 30. 16. 4379–4386. 10.1021/om200471e.
2. Robert E. Dinnebier . Ulrich Behrens . Falk Olbrich . amp . Solid State Structures of Cyclopentadienyllithium, -sodium, and -potassium. Determination by High-Resolution Powder Diffraction . . 1997 . 16 . 17 . 3855–3858 . 10.1021/om9700122.