Electride

Solutions of alkali metals in ammonia are electride salts. In the case of sodium, these blue solutions consist of [Na(NH3)6]+ and solvated electrons: :Na + 6 NH3 → [Na(NH3)6]+ + e− The cation [Na(NH3)6]+ is an octahedral coordination complex. Despite the name, the electron does not leave the sodium-ammonia complex, but it is transferred from Na to the vacant orbitals of the coordinated ammonia molecules. Similar solutions exist in hexamethylphosphoramide. ==Solid salts==

Many "inorganic electrides" have been described. Addition of a complexant like crown ether or 2.2.2-Cryptand|[2.2.2]-cryptand to a solution of [Na(NH3)6]+e− affords [Na (crown ether)]+e− or [Na(2,2,2-crypt)]+e−. Evaporation of these solutions yields a blue-black paramagnetic solid with the formula [Na(2,2,2-crypt)]+e−. Many early crystalline organic electrides decompose above 240 K, whereas the mayenite-derived calcium aluminate electride C12A7:e− is stable at room temperature. C12A7:e− has been used as a low-work-function electron donor and as a catalyst support, for example in ruthenium-catalyzed ammonia synthesis. In electride salts, the electron is delocalized between the cations. Properties of these salts have been analyzed. ThI2 and ThI3 have also been proposed to be electride compounds. Similarly, CeI2|, Lanthanum diiodide|, Gadolinium diiodide|, and PrI2| are all electride salts with a tricationic metal ion. Organometallic electrides Magnesium reduced nickel(II)-bipyridyl (bipy) complex have been labeled organic electrides. An example is [(THF)4Mg4(μ2-bipy)4]–, in which the electride is the singly occupied molecular orbital (SOMO) formed by the Mg-square cluster within the larger complex.{{cite journal|last1=Day|first1=Craig S. ==Reactions==

Electride salts are powerful reducing agents, as demonstrated by their use in the Birch reduction. Evaporation of these blue solutions affords a mirror of Na metal. If not evaporated, such solutions slowly lose their colour as the electrons reduce ammonia: :2[Na(NH3)6]+e− → 2NaNH2 + 10NH3 + H2 This conversion is catalyzed by various metals. An electride, [Na(NH3)6]+e−, is formed as a reaction intermediate. ==High-pressure elements==

In quantum chemistry, an electride is identified by a maximum of the electron density, characterized by a non-nuclear attractor, a large and negative Laplacian at the critical point, and an electron localization function isosurface close to 1. Electride phases are typically semiconducting or have very low conductivity, the universal but robust gapless surface state in insulating electride that forming a de facto real space topological distribution of charge carriers, and the colossal charge state of some impurities in them. ==Layered electrides (Electrenes)==

Layered electrides or electrenes are single-layer materials consisting of alternating atomically thin two-dimensional layers of electrons and ionized atoms. The first example was Ca2N, in which the charge (+4) of two calcium ions is balanced by the charge of a nitride ion (−3) in the ion layer plus a charge (−1) in the electron layer. ==See also==