Electride

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As electrides refers to chemical compounds in which the negative charge is not as anion , but as a free electron is present. The first such compound, the structure of which was clarified by X-ray crystallography, is the cesium -electride Cs + (18C6) 2  · e - (18C6 = 18-crown-6 ). The compounds are closely related to the alkalides .

Appearance and properties

Sodium dissolved in liquid ammonia

The synthesis is usually carried out by dissolving the corresponding alkali metal in liquid ammonia or an alkylamine in the presence of a suitable cryptand or crown ether. A classic experiment for generating electrides is, for example, the dissolution of sodium metal in liquid ammonia. This creates a paramagnetic and electrically conductive dark blue solution in which the electrons are solvated by the solvent . A key aspect in the representation of electrides in the solid state is, as with the alkalides , the use of irreducible crown ethers or cryptands to complex the alkali metal cations. At the compound Cs + (18C6) 2  · e - it could be shown that the electrical conductivity in the solid body of the electride is low, which confirms the localization of the electrons. Electrides are very reactive and strong reducing agents and usually decompose at temperatures above −40 ° C. In 2003, however, Hosono et al . from the first chemically and thermally stable electride compound [Ca 24 Al 28 O 64 ] 4+ (4e - ), a nanoporous oxide with the structure of mayenite .

Further examples

A large number of different electrides with different alkali metal cations and different complexing agents were synthesized. For example, the preparation of lithium electride [Li + (cryptand [2.1.1]) e - ], potassium electride [K + (cryptand [2.2.2]) e - ], rubidium electride [Rb + (cryptand [2.2.2]) e - ] and a sodium electride stable at room temperature .

Individual evidence

  1. ↑ a b c Steven B. Dawes, Donald L. Ward, Rui He Huang, James L. Dye: First Electride Crystal Structure. In: J. Am. Chem. Soc. Volume 108, 1986, pp. 3535-3537.
  2. ↑ James L. Dye: Electrides: Ionic Salts with Electrons as the Anions. In: Science. Volume 247, 1990, pp. 663-668.
  3. ↑ James L. Dye: Electrons as Anions. In: Science. Volume 301, 2003, pp. 607-608.
  4. ↑ Satoru Matsuishi, Yoshitake Toda, Masashi Miyakawa, Katsuro Hayashi, Toshio Kamiya, Masahiro Hirano, Isao Tanaka, Hideo Hosono: High-Density Electron Anions in a Nanoporous Single Crystal: [Ca24Al28O64] 4+ (4e-) . In: Science . tape 301 , 2003, p. 626-629 , doi : 10.1126 / science.1083842 .
  5. ↑ Rui H. Huang, Michael J. Wagner, Deborah J. Gilbert, Kerry A. Reidy-Cedergren, Donald L. Ward, Margaret K. Faber, James L. Dye: Structure and Properties of Li + (Cryptand [2.1.1 ]) e - , an Electride with a 1D “Spin-Ladder-like” Cavity-Channel Geometry. In: J. Am. Chem. Soc. Volume 119, 1997, pp. 3765-3772.
  6. ↑ Donald L. Ward, Rui H. Huang, James L. Dye: Structures of Alkalides and Electrides. I. Structure of Potassium Cryptand [2.2.2] * Electride. In: Acta Cryst. Volume C44, 1988, pp. 1374-1376.
  7. ↑ Qingshan Xie, Rui H. Huang, Andrew S. Ichimura, Richard C. Phillips, William P. Pratt, Jr., James L. Dye: Structure and Properties of a New Electride, Rb + (cryptand [2.2.2]) e - . In: J. Am. Chem. Soc. Vol. 122, 2000, pp. 6971-6978.
  8. ↑ Mikhail Y. Redko, James E. Jackson, Rui H. Huang, James L. Dye: Design and Synthesis of a Thermally Stable Organic Electride. In: J. Am. Chem. Soc. Volume 127, 2005, pp. 12416-12422.