Sodium cyclopentadienide

Sodium cyclopentadienide
	; The cyclopentadienide anion
Names
	Other names sodium cyclopentadienylide, cyclopentadienylsodium
Identifiers
CAS Number	4984-82-1 ;
3D model (JSmol)	Interactive image;
ChemSpider	71032 ;
ECHA InfoCard	100.023.306
EC Number	225-636-8;
PubChem CID	78681;
CompTox Dashboard (EPA)	DTXSID9063665 ;
	InChI InChI=1S/C5H5.Na/c1-2-4-5-3-1;/h1-5H;/q-1;+1 Key: OHUVHDUNQKJDKW-UHFFFAOYSA-N ; 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	88.085 g·mol−1
Appearance	colorless solid
Solubility in water	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). verify (what is ?) 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.^[1] Sodium cyclopentadienide is a colorless solid, although samples often are pink owing to traces of oxidized impurities.^[2]

Preparation

Sodium cyclopentadienide is commercially available as a solution in THF. It is prepared by treating cyclopentadiene with sodium:^[3]

2 Na + 2 C₅H₆ → 2 NaC₅H₅ + H₂

Commonly, the conversion is conducted by heating a suspension of molten sodium in dicyclopentadiene.^[2] 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.^[4]^[5] Sodium hydride is a convenient base:^[6]

NaH + C₅H₆ → NaC₅H₅ + H₂

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.^[7] 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.^[8]

Applications

Sodium cyclopentadienide is a common reagent for the preparation of metallocenes. For example, the preparation of ferrocene^[4] and zirconocene dichloride:^[9]

2 NaC₅H₅ + FeCl₂ → Fe(C₅H₅)₂ + 2 NaCl

ZrCl₄(thf)₂ + 2 NaCp → Cp₂ZrCl₂ + 2 NaCl + 2 THF

References

^ International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. p. 262. Electronic version.
^ ^a ^b Tarun K. Panda, Michael T. Gamer, Peter W. Roesky "An Improved Synthesis of Sodium and Potassium Cyclopentadienide" Organometallics, 2003, 22, 877–878.doi:10.1021/om0207865
^ Cotton, F. Albert; Wilkinson, Geoffrey (1988), Advanced Inorganic Chemistry (5th ed.), New York: Wiley-Interscience, p. 139, ISBN 0-471-84997-9
^ ^a ^b Wilkinson, Geoffrey (1963). "Ferrocene". Organic Syntheses; Collected Volumes, vol. 4, p. 473.
^ 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.
^ Girolami, G. S.; Rauchfuss, T. B. and Angelici, R. J. (1999). Synthesis and Technique in Inorganic Chemistry. CA: University Science Books: Mill Valley. ISBN 0935702482.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ Robert E. Dinnebier, Ulrich Behrens, and Falk Olbrich (1997). "Solid State Structures of Cyclopentadienyllithium, -sodium, and -potassium. Determination by High-Resolution Powder Diffraction". Organometallics. 16: 3855–3858. doi:10.1021/om9700122.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Elschenbroich, C. (2006). Organometallics. Wiley-VCH: Weinheim. ISBN 978-3-527-29390-2.
^ Wilkinson, G.; Birmingham, J. G. (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". J. Am. Chem. Soc. 76 (17): 4281–84. doi:10.1021/ja01646a008.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[1] International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. p. 262. Electronic version.

[Roesky-2] Tarun K. Panda, Michael T. Gamer, Peter W. Roesky "An Improved Synthesis of Sodium and Potassium Cyclopentadienide" Organometallics, 2003, 22, 877–878.doi:10.1021/om0207865

[3] Cotton, F. Albert; Wilkinson, Geoffrey (1988), Advanced Inorganic Chemistry (5th ed.), New York: Wiley-Interscience, p. 139, ISBN 0-471-84997-9

[ferrocene-4] Wilkinson, Geoffrey (1963). "Ferrocene". Organic Syntheses; Collected Volumes, vol. 4, p. 473.

[5] 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.

[6] Girolami, G. S.; Rauchfuss, T. B. and Angelici, R. J. (1999). Synthesis and Technique in Inorganic Chemistry. CA: University Science Books: Mill Valley. ISBN 0935702482.{{cite book}}: CS1 maint: multiple names: authors list (link)

[7] Robert E. Dinnebier, Ulrich Behrens, and Falk Olbrich (1997). "Solid State Structures of Cyclopentadienyllithium, -sodium, and -potassium. Determination by High-Resolution Powder Diffraction". Organometallics. 16: 3855–3858. doi:10.1021/om9700122.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[8] Elschenbroich, C. (2006). Organometallics. Wiley-VCH: Weinheim. ISBN 978-3-527-29390-2.

[9] Wilkinson, G.; Birmingham, J. G. (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". J. Am. Chem. Soc. 76 (17): 4281–84. doi:10.1021/ja01646a008.{{cite journal}}: CS1 maint: multiple names: authors list (link)

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