Electride

An electride is an ionic compound in which an electron is the anion. [cite journal | author = Dye, J. L. | title = Electrons as Anions | journal = Science | year = 2003 | volume = 301 | pages = 607–608 | doi = 10.1126/science.1088103] The first electrides to be studied in depth were solutions of alkali metals in ammonia. [Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.] When sodium metal dissolves in ammonia, the result is a blue solution consisting of [Na(NH₃)₆] ⁺ and solvated electrons. Such solutions are powerfully reducing, as demonstrated by their use in Birch reductions. Evaporation of these blue solutions affords a mirror of Na. Such solutions slowly lose their colour as the electrons reduce ammonia:: [Na(NH₃)₆] ⁺e^- + NH₃ → NaNH₂ + H₂

Addition of 2,2,2-cryptand to a solution of [Na(NH₃)₆] ⁺e^- affords [Na(2,2,2-crypt)] ⁺e^-. Evaporation of "these" solutions yields a blue-black paramagnetic salt with the formula [Na(2,2,2-crypt)] ⁺e^-. Such salts decompose above 240 K. In these salts, the electron is delocalized between the cations. Electrides are paramagnetic and Mott insulators.

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