Sodium cyclopentadienide is an
organosodium compound with the
formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...
C
5H
5Na. 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.
[
]
Preparation
The first salt of cyclopentadienide to be reported was potassium cyclopentadienide, prepared by Johannes Thiele Johannes Thiele may refer to:
*Johannes Thiele (zoologist)
*Johannes Thiele (chemist)
{{hndis, Thiele, Johannes ...
. In 1901 there was not much interest in the topic.
Sodium cyclopentadienyl is prepared by treating cyclopentadiene
Cyclopentadiene is an organic compound with the chemical formula, formula C5H6. It is often abbreviated CpH because the cyclopentadienyl anion is abbreviated Cp−.
This colorless liquid has a strong and unpleasant odor. At room temperature, ...
with sodium
Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
:
:
The conversion can be conducted by heating a suspension of molten sodium in dicyclopentadiene
Dicyclopentadiene, abbreviated DCPD, is a chemical compound with formula . At room temperature, it is a white brittle wax, although lower purity samples can be straw coloured liquids. The pure material smells somewhat of soy wax or camphor, with ...
.[Tarun K. Panda, Michael T. Gamer, Peter W. Roesky "An Improved Synthesis of Sodium and Potassium Cyclopentadienide" Organometallics, 2003, 22, 877–878.] In former times, the sodium was provided in the form of "sodium wire" or "sodium sand", a fine dispersion of sodium prepared by melting sodium in refluxing xylene
In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are su ...
and rapidly stirring.Grignard reagent
Grignard reagents or Grignard compounds are chemical compounds with the general formula , where X is a halogen and R is an organic group, normally an alkyl or aryl. Two typical examples are methylmagnesium chloride and phenylmagnesium bromi ...
s were used as bases. With a p''K''a of 15, cyclopentadiene can be deprotonated by many reagents.
Sodium cyclopentadienide is commercially available as a solution in THF.
Applications
Sodium cyclopentadienide is a common reagent for the preparation of metallocene
A metallocene is a compound typically consisting of two cyclopentadienyl anions (, abbreviated Cp) bound to a metallic element, metal center (M) in the oxidation state II, with the resulting general formula Closely related to the metallocenes are ...
s. For example, the preparation of ferrocene
Ferrocene is an organometallic chemistry, organometallic compound with the formula . The molecule is a Cyclopentadienyl complex, complex consisting of two Cyclopentadienyl anion, cyclopentadienyl rings sandwiching a central iron atom. It is an o ...
[ and ]zirconocene dichloride
Zirconocene dichloride is an organozirconium compound composed of a zirconium central atom, with two cyclopentadienyl and two chloro ligands. It is a colourless diamagnetic solid that is somewhat stable in air.
Preparation and structure
Zircono ...
:
:
:
Sodium cyclopentadienide is also used for the preparation of substituted cyclopentadienyl derivatives such as the ester and formyl derivatives:
:
These compounds are used to prepare substituted metallocenes such as 1,1'-ferrocenedicarboxylic acid.
Structure
The nature of NaCp depends strongly on its medium and for the purposes of planning syntheses; the reagent is often represented as a salt . 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''- ''η''5:''η''5-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
In chemistry, an adduct (; alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is ...
Na(tmeda
Tetramethylethylenediamine (TMEDA or TEMED) is a chemical compound with the formula (CH3)2NCH2CH2N(CH3)2. This species is derived from ethylenediamine by replacement of the four amine hydrogens with four methyl groups. It is a colorless liquid, ...
)Cp.
In contrast to alkali metal cyclopentadienides, tetrabutylammonium cyclopentadienide () was found to be supported entirely by ionic bonding and its structure is representative of the structure of the cyclopentadienide anion (, Cp−) in the solid state. However, the anion deviates somewhat from a planar, regular pentagon, with C–C bond lengths ranging from 138.0 -140.1 pm and C–C–C bond angles ranging from 107.5-108.8°.
See also
* Lithium cyclopentadienide
* Potassium cyclopentadienyl
References
{{Cyclopentadiene complexes
Organosodium compounds
Cyclopentadienyl complexes
Non-benzenoid aromatic carbocycles