Lithium naphthalenide
 A solution of lithium naphthalenide in tetrahydrofuran | |
| Names | |
|---|---|
| Preferred IUPAC name
Lithium naphthalenide | |
| Other names
LN | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
PubChem CID |
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| Properties | |
| Li+[C10H8]− | |
| Molar mass | 135.11 g·mol−1 |
| Appearance | Dark green crystals |
| Solubility | Soluble in ether, benzene, THF[1] |
| Related compounds | |
Other cations |
sodium naphthalenide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Lithium naphthalenide is an organic salt with the chemical formula Li+[C10H8]−. In the research laboratory, it is used as a reductant in the synthesis of organic, organometallic, and inorganic chemistry. It is usually generated in situ. Lithium naphthalene crystallizes with ligands bound to Li+.[2] The anion is a well-known example of an organic radical.
Preparation and properties
[edit]The compound is prepared by stirring the metallic lithium with naphthalene in an ethereal solvent, usually as tetrahydrofuran or dimethoxyethane. The resulting salt is dark green.[3] The reaction of naphthalene with lithium can be accelerated by sonication. Methods for assaying lithium naphthalene have been developed as well.[4] As a radical, its solutions show a strong EPR signal near g = 2.0.[5] Its deep green color arises from absorptions at 463 and 735 nm.[6]
Several solvates of lithium naphthalene have been characterized by X-ray crystallography. The effects are subtle, the outer pair of HC–CH bonds contract by 3 pm and the other nine C–C bonds elongate by 2–3 pm. Net reduction weakens the bonding.[7]
Reactions
[edit]Reductant
[edit]With a reduction potential near −2.5 V versus the normal hydrogen electrode, the naphthalene radical anion is a strong reducing agent.[6] Lithium naphthalene has often been used to cleave carbon-heteroatom bonds.[8][1]
Protonation
[edit]The anion is strongly basic, and a typical degradation pathway involves reaction with water and related protic sources such as alcohols. These reactions give dihydronaphthalene:[9]
As a ligand precursor
[edit]Alkali metal salts of the naphthalene radical anion are used to prepare complexes of naphthalene.[10]
Related compounds
[edit]Many related radical anions are known such as those derived from anthracene, with other alkali metals (especially sodium), and with diverse ligands attached to the alkali metal cations such as [Li+(tmeda)2]2[C10H8]2−.[11][2]
References
[edit]- 1 2 Short, Kevin M.; Wei, Alexander; Padungros, Panuwat (2014). "Lithium Naphthalenide". Encyclopedia of Reagents for Organic Synthesis. pp. 1–6. doi:10.1002/047084289X.rl131.pub2. ISBN 978-0-470-84289-8.
- 1 2 Melero, Cristóbal; Guijarro, Albert; Yus, Miguel (2009). "Structural Characterization and Bonding Properties of Lithium Naphthalene Radical Anion, Li+(TMEDA)2C
10H−
8, and Lithium Naphthalene Dianion (Li+TMEDA)2C
10H2−
8". Dalton Transactions (8): 1286–1289. doi:10.1039/b821119c. PMID 19462646. - ↑ David G. Hilmey; Leo A. Paquette (2007). "1,3-Dichloroacetone as a Cyclopropanone Equivalent: 5-Oxaspiro[3.4]Octan-1-one". Organic Syntheses. 84: 156. doi:10.15227/orgsyn.084.0156.
- ↑ Nicholas A. Morra and Brian L. Pagenkopf (2008). "Direct Synthesis of 2,5-Dihalosiloles". Organic Syntheses. 85: 53. doi:10.15227/orgsyn.085.0053.
- ↑ Cotton, F. Albert; Wilkinson, Geoffrey (1988), Advanced Inorganic Chemistry (5th ed.), New York: Wiley-Interscience, p. 139, ISBN 0-471-84997-9
- 1 2 Connelly, Neil G.; Geiger, William E. (1996). "Chemical Redox Agents for Organometallic Chemistry". Chemical Reviews. 96 (2): 877–910. doi:10.1021/cr940053x. PMID 11848774.
- ↑ Castillo, Maximiliano; Metta-Magaña, Alejandro J.; Fortier, Skye (2016). "Isolation of Gravimetrically Quantifiable Alkali Metal Arenides Using 18-Crown-6". New Journal of Chemistry. 40 (3): 1923–1926. doi:10.1039/C5NJ02841H.
- ↑ Gao, Jian-Wu (2012). "Lithium Naphthalenide". Synlett (2): 317–318. doi:10.1055/s-0031-1290127.
- ↑ Elliott, M.C.; Hewitt, N.L. (2014). "8.19 Partial Reduction of Benzenoid Aromatic Rings by Dissolving Metals and by Other Methods". Comprehensive Organic Synthesis II. pp. 639–672. doi:10.1016/B978-0-08-097742-3.00821-1. ISBN 978-0-08-097743-0.
- ↑ Ellis, John E. (2019). "The Chatt Reaction: Conventional Routes to homoleptic Arenemetalates of d-Block Elements". Dalton Transactions. 48 (26): 9538–9563. doi:10.1039/C8DT05029E. PMID 30724934. S2CID 73436073.
- ↑ Brooks, J. J.; Rhine, Wendell; Stucky, G. D. (1972). "π-Groups in Ion Pair Bonding. Stabilization of the Dianion of Naphthalene by Lithium Tetramethylethylenediamine". Journal of the American Chemical Society. 94 (21): 7346–7351. Bibcode:1972JAChS..94.7346B. doi:10.1021/ja00776a014.