| Sodium cyclopentadienide | |
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| Other names | sodium cyclopentadienylide, cyclopentadienylsodium |
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| CAS number | [] |
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| Properties | |
| Molecular formula | C5H5Na |
| Molar mass | 88.08 g mol−1 |
| Solubility in water | Reacts |
| Solubility in tetrahydrofuran | Soluble |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Sodium cyclopentadienide is an organosodium compound. Its chemical formula is C5H5Na, but is often abbreviated to NaCp or CpNa, where Cp− is the cyclopentadienide anion. Cp is also used as an abbreviation for the cyclopentadienyl ligand in coordination chemistry.[1]
Preparation
Sodium cyclopentadienide is commercially available as a solution in THF. It can be prepared by treating cyclopentadiene with sodium:[2]
- 2 Na + 2 C5H6 → 2 NaC5H5 + H2
The use of "sodium sand", a fine dispersion of sodium prepared by melting sodium in refluxing xylene and rapidly stirring, is traditional.[3][4] Sodium hydride is a convenient base:[5]
- NaH + C5H6 → NaC5H5 + H2
In early work, Grignard reagents were used as bases. With a pKa of 15, cyclopentadiene can be deprotonated with 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.[6] 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.[7]
Applications
Sodium cyclopentadienide is a common reagent for the preparation of metallocenes. For example, the preparation of ferrocene[3] and zirconocene dichloride:[8]
- 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.
- ^ 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". Org. Synth.; Coll. Vol. 4: 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". Org. Synth.; Coll. Vol. 7: 339.
- ^ Girolami, G. S.; Rauchfuss, T. B. and Angelici, R. J., Synthesis and Technique in Inorganic Chemistry, University Science Books: Mill Valley, CA, 1999.ISBN 0935702482
- ^ 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:.
- ^ Elschenbroich, C. ”Organometallics” (2006) Wiley-VCH: Weinheim. ISBN 978-3-29390-6
- ^ 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:.
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