Sodium cyclopentadienide is an organosodium compound with the formula C5H5Na. The compound is often abbreviated as NaCp, where Cp− is the cyclopentadienide anion.[1] Sodium cyclopentadienide is a colorless solid, although samples often are pink owing to traces of oxidized impurities.[2]
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The cyclopentadienide anion
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Names | |||
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Preferred IUPAC name
Sodium cyclopentadienide | |||
Other names
Sodium cyclopentadienylide, Cyclopentadienylsodium
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Identifiers | |||
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3D model (JSmol)
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ChemSpider |
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ECHA InfoCard | 100.023.306 | ||
EC Number |
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PubChem CID
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CompTox Dashboard (EPA)
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Properties | |||
C5H5Na | |||
Molar mass | 88.085 g·mol−1 | ||
Appearance | colorless solid | ||
Density | 1.113 g/cm3 | ||
decomposition | |||
Solubility | THF | ||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards
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flammable | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
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Sodium cyclopentadienide is commercially available as a solution in THF. It is prepared by treating cyclopentadiene with sodium:[3]
The conversion can be conducted by heating a suspension of molten sodium in dicyclopentadiene.[2] 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 and rapidly stirring.[4][5] Sodium hydride is a convenient base:[6]
In early work, Grignard reagents were used as bases. With a pKa of 15, cyclopentadiene can be deprotonated by many reagents.
Sodium cyclopentadienide is a common reagent for the preparation of metallocenes. For example, the preparation of ferrocene[4] and zirconocene dichloride:[7]
Sodium cyclopentadienide is also used for the preparation of substituted cyclopentadienyl derivatives such as the ester and formyl derivatives:[8]
These compounds are used to prepare substituted metallocenes such as 1,1'-ferrocenedicarboxylic acid.[9]
The nature of NaCp depends strongly on its medium and for the purposes of planning syntheses; the reagent is often represented as a salt Na+
C
5H−
5. 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.[10] 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.[11]
In contrast to alkali metal cyclopentadienides, tetrabutylammonium cyclopentadienide (Bu4N+C5H5−) was found to be supported entirely by ionic bonding and its structure is representative of the structure of the cyclopentadienide anion (C5H5−, 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°.[12]
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: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 7, p. 339.