Английская Википедия:Electride
An electride is an ionic compound in which an electron serves the role of the anion.[1] Solutions of alkali metals in ammonia are electride salts.[2] 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.
Solid salts
Addition of a complexant like crown ether or [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−.
Most solid electride salts decompose above 240 K, although [Ca24Al28O64]4+(e−)4 is stable at room temperature.[3] In these salts, the electron is delocalized between the cations. Electrides are paramagnetic, and are Mott insulators. Properties of these salts have been analyzed.[4]
ThI2 and ThI3 have also been reported to be electride compounds.[5] Similarly, [[Cerium#Chemistry|Шаблон:Chem]], Шаблон:Chem, Шаблон:Chem, and Шаблон:Chem are all electride salts with a tricationic metal ion.[6][7]
Reactions
Solutions of 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.[8] An electride, [Na(NH3)6]+e−, is formed as a reaction intermediate.
High-pressure elements
Theoretical evidence supports electride behaviour in insulating high-pressure forms of potassium, sodium, and lithium. Here the isolated electron is stabilized by efficient packing, which reduces enthalpy under external pressure. The electride is identified by a maximum in the electron localization function, which distinguishes the electride from pressure-induced metallization. Electride phases are typically semiconducting or have very low conductivity,[9][10][11] usually with a complex optical response.[12] A sodium compound called disodium helide has been created under Шаблон:Convert of pressure.[13]
Layered electrides (Electrenes)
Layered electrides or electrenes are single-layer materials consisting of alternating atomically thin two-dimensional layers of electrons and ionized atoms.[14][15] 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.[14]
See also
References
Further reading
- ↑ Шаблон:Cite journal
- ↑ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. Шаблон:ISBN
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal.
- ↑ Шаблон:Cite book
- ↑ Шаблон:Greenwood&Earnshaw2nd
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ 14,0 14,1 Шаблон:Cite journal
- ↑ Шаблон:Cite journal
