Sodium cyclopentadienide

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"NaCp" redirects here. For other uses, see NACP (disambiguation).
Sodium cyclopentadienide
NaCp synthesized in an inert atmosphere
Names
Preferred IUPAC name
Sodium cyclopentadienide
Other names
Sodium cyclopentadienylide, Cyclopentadienylsodium
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.023.306 Edit this at Wikidata
EC Number
  • 225-636-8
  • InChI=1S/C5H5.Na/c1-2-4-5-3-1;/h1-5H;/q-1;+1 checkY
    Key: OHUVHDUNQKJDKW-UHFFFAOYSA-N checkY
  • InChI=1S/C5H5.Na/c1-2-4-5-3-1;/h1-5H;/q-1;+1
  • Key: OHUVHDUNQKJDKW-UHFFFAOYSA-N
SMILES
  • [Na+].c1[cH-]ccc1
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
 flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

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]

Preparation

The first salt of cyclopentadienide to be reported was potassium cyclopentadienide, prepared by Johannes Thiele. In 1901 there was not much interest in the topic.[3]

Sodium cyclopentadienyl is prepared by treating cyclopentadiene with sodium:[4]

2 Na + 2 C5H6 → 2 NaC5H5 + H2

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.[5][6] Sodium hydride is a convenient base:[7]

NaH + C5H6 → NaC5H5 + H2

In early work, Grignard reagents were used as bases. With a pKa 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 metallocenes. For example, the preparation of ferrocene[5] and zirconocene dichloride:[8]

2 NaC5H5 + FeCl2 → Fe(C5H5)2 + 2 NaCl
ZrCl4(thf)2 + 2 NaCp → (C5H5)2ZrCl2 + 2 NaCl + 2 THF

Sodium cyclopentadienide is also used for the preparation of substituted cyclopentadienyl derivatives such as the ester and formyl derivatives:[9]

NaC5H5 + O=C(OEt)2 → NaC5H4CO2Et + NaOEt

These compounds are used to prepare substituted metallocenes such as 1,1'-ferrocenedicarboxylic acid.[10]

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 Na+
C
5H−
5. Crystalline solvent-free NaCp, which is rarely encountered, is a "polydecker"

tmeda)Cp.[12]

In contrast to alkali metal cyclopentadienides, tetrabutylammonium cyclopentadienide (Bu
4N+
C
5H−
5) was found to be supported entirely by ionic bonding and its structure is representative of the structure of the cyclopentadienide anion (C
5H−
5, 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°.[13]


See also

References

  1. ISBN 0-85404-438-8. p. 262. Electronic version.
  2. ^
    doi:10.1021/om0207865
  3. Wikidata Q126217369
    .
  4. ISBN 0-471-84997-9
  5. ^ a b Wilkinson, Geoffrey (1963). "Ferrocene". Organic Syntheses; Collected Volumes, vol. 4, p. 473.
  6. ^ Partridge, John J.; Chadha, Naresh K.; Uskokovic, Milan R. (1990). "An asymmetric hydroboration of 5-substituted cyclopentadienes: synthesis of methyl (1R,5R)-5-hydroxy-2-cyclopentene-1-acetate". Organic Syntheses{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 7, p. 339.
  7. ISBN 0935702482
    .
  8. doi:10.1021/ja01646a008
    .
  9. ISBN 9780120311217
    .
  10. doi:10.1021/om4004972
    .
  11. doi:10.1021/om9700122
    .
  12. ISBN 978-3-527-29390-2
    .
  13. S2CID 45791403
    .
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