Sodium cyclopentadienide

Sodium cyclopentadienide

The cyclopentadienide anion
Names
Other names sodium cyclopentadienylide, cyclopentadienylsodium
Identifiers
CAS Number	4984-82-1 Y
3D model (Jmol)	Interactive image
ChemSpider	71032 Y
ECHA InfoCard	100.023.306
EC Number	225-636-8
PubChem	78681
InChI InChI=1S/C5H5.Na/c1-2-4-5-3-1;/h1-5H;/q-1;+1 Y Key: OHUVHDUNQKJDKW-UHFFFAOYSA-N Y InChI=1S/C5H5.Na/c1-2-4-5-3-1;/h1-5H;/q-1;+1 Key: OHUVHDUNQKJDKW-UHFFFAOYSA-N
SMILES [Na+].c1[c-]ccc1
Properties
Chemical formula	C5H5Na
Molar mass	88.08 g·mol−1
Appearance	colorless solid
Solubility in water	decomposition
Solubility	THF
Hazards
Main hazards	flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Sodium cyclopentadienide is an organosodium compound with the formula C₅H₅Na. The compound is often abbreviated as NaCp, where Cp⁻ is the cyclopentadienide anion. Sodium cyclopentadienide is a colorless solid, although samples often are pink owing to traces of oxidized impurities.

Sodium cyclopentadienide is commercially available as a solution in THF. It is prepared by treating cyclopentadiene with sodium:

Commonly, the conversion is conducted by heating a suspension of molten sodium in dicyclopentadiene. In former times, the sodium was commonly provided in the form of "sodium wire" or "sodium sand", a fine dispersion of sodium prepared by melting sodium in refluxing xylene and rapidly stirring.Sodium hydride is a convenient base:

In early work, Grignard reagents were used as bases. With a pK_a of 15, cyclopentadiene can be deprotonated by many reagents.

The nature of NaCp depends strongly its medium and for the purposes of planning syntheses, the reagent is often represented as a salt Na⁺C₅H₅⁻. Crystalline solvent-free NaCp, which is rarely encountered, is a "polydecker" sandwich complex, consisting of an infinite chain of alternating Na⁺ centers sandwiched between μ-η⁵:η⁵-C₅H₅ ligands. As a solution in donor solvents, NaCp is highly solvated, especially at the alkali metal as suggested by the isolability of the adduct Na(tmeda)Cp.

Sodium cyclopentadienide is a common reagent for the preparation of metallocenes. For example, the preparation of ferrocene and zirconocene dichloride: