Electride

Last updated
Cavities and channels in an electride Electride 01.jpg
Cavities and channels in an 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:

Contents

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. [3]

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. [4] In these salts, the electron is delocalized between the cations. Properties of these salts have been analyzed. [5]

ThI2 and ThI3 have also been proposed to be electride compounds. [6] Similarly, CeI
2
, LaI
2
, GdI
2
, and PrI
2
are all electride salts with a tricationic metal ion. [7] [8]

Organometallic electrides

Magnesium reduced nickel(II)-bipyridyl (bipy) complex have been labeled organic electrides. An example is [(THF)4Mg42-bipy)4], in which the electride is the singly occupied molecular orbital (SOMO) formed by the Mg-square cluster within the larger complex. [9]

"Inorganic electrides" have also been described. [10]

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. [11] 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. [12] Electride phases are typically semiconducting or have very low conductivity, [13] [14] [15] usually with a complex optical response. [16] A sodium compound called disodium helide has been created under 113 gigapascals (1.12×10^6 atm) of pressure. [17] It has been proven that the localized electron density in high-pressure electrides does not correspond to isolated electrons, but that it is generated by the formation of (multicenter) chemical bonds. [18] [19]

The intrinsic polarization between atomic nucleus and the electron anion in these high pressure electrides can lead to unique properties, such as the splitting of the longitudinal and transverse acoustic modes (i.e., LA-TA splitting, an analogue to the LO-TO splitting in ionic compound), [20] the universal but robust gapless surface state in insulating electride that forming a de facto real space topological distribution of charge carriers, [21] and the colossal charge state of some impurities in them. [22]

Layered electrides (Electrenes)

Layered electrides or electrenes are single-layer materials consisting of alternating atomically thin two-dimensional layers of electrons and ionized atoms. [23] [24] 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. [23]

See also

Related Research Articles

<span class="mw-page-title-main">Alkali metal</span> Group of highly reactive chemical elements

The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). Together with hydrogen they constitute group 1, which lies in the s-block of the periodic table. All alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having very similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour. This family of elements is also known as the lithium family after its leading element.

<span class="mw-page-title-main">Ammonium</span> Chemical compound

Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) molecular ion with the chemical formula NH+4 or [NH4]+. It is formed by the addition of a proton to ammonia. Ammonium is also a general name for positively charged (protonated) substituted amines and quaternary ammonium cations, where one or more hydrogen atoms are replaced by organic or other groups. Not only is ammonium a source of nitrogen and a key metabolite for many living organisms, but it is an integral part of the global nitrogen cycle. As such, human impact in recent years could have an effect on the biological communities that depend on it.

<span class="mw-page-title-main">Base (chemistry)</span> Type of chemical substance

In chemistry, there are three definitions in common use of the word "base": Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. Rouelle in the mid-18th century.

<span class="mw-page-title-main">Hydride</span> Molecule with a hydrogen bound to a more electropositive element or group

In chemistry, a hydride is formally the anion of hydrogen (H), a hydrogen atom with two electrons. The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are also called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. For inorganic chemists, hydrides refer to compounds and ions in which hydrogen is covalently attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed.

<span class="mw-page-title-main">Diborane</span> Chemical compound

Diborane(6), commonly known as diborane, is the chemical compound with the formula B2H6. It is a highly toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Given its simple formula, borane is a fundamental boron compound. It has attracted wide attention for its electronic structure. Several of its derivatives are useful reagents.

<span class="mw-page-title-main">Sodium azide</span> Chemical compound

Sodium azide is an inorganic compound with the formula NaN3. This colorless salt is the gas-forming component in some car airbag systems. It is used for the preparation of other azide compounds. It is an ionic substance, is highly soluble in water, and is acutely poisonous.

<span class="mw-page-title-main">Cryptand</span> Cyclic, multidentate ligands adept at encapsulating cations

In chemistry, cryptands are a family of synthetic, bicyclic and polycyclic, multidentate ligands for a variety of cations. The Nobel Prize for Chemistry in 1987 was given to Donald J. Cram, Jean-Marie Lehn, and Charles J. Pedersen for their efforts in discovering and determining uses of cryptands and crown ethers, thus launching the now flourishing field of supramolecular chemistry. The term cryptand implies that this ligand binds substrates in a crypt, interring the guest as in a burial. These molecules are three-dimensional analogues of crown ethers but are more selective and strong as complexes for the guest ions. The resulting complexes are lipophilic.

<span class="mw-page-title-main">Lithium nitride</span> Chemical compound

Lithium nitride is an inorganic compound with the chemical formula Li3N. It is the only stable alkali metal nitride. It is a reddish-pink solid with a high melting point.

<span class="mw-page-title-main">Borazine</span> Boron compound

Borazine, also known as borazole, is an inorganic compound with the chemical formula B3H6N3. In this cyclic compound, the three BH units and three NH units alternate. The compound is isoelectronic and isostructural with benzene. For this reason borazine is sometimes referred to as “inorganic benzene”. Like benzene, borazine is a colourless liquid with an aromatic odor.

<span class="mw-page-title-main">Graphite intercalation compound</span> Class of chemical compounds

In the area of solid state chemistry, graphite intercalation compounds are a family of materials prepared from graphite. In particular, the sheets of carbon that comprise graphite can be pried apart by the insertion (intercalation) of ions. The graphite is viewed as a host and the inserted ions as guests. The materials have the formula (guest)Cn where n can range from 8 to 40's. The insertion of the guests increases the distance between the carbon sheets. Common guests are reducing agents such as alkali metals. Strong oxidants also intercalate into graphite. Intercalation involves electron transfer into or out of the carbon sheets. So, in some sense, graphite intercalation compounds are salts. Intercalation is often reversible: the inserted ions can be removed and the sheets of carbon collapse to a graphite-like structure.

A solvated electron is a free electron in a solution, in which it behaves like an anion. An electron's being solvated in a solution means it is bound by the solution. The notation for a solvated electron in formulas of chemical reactions is "e". Often, discussions of solvated electrons focus on their solutions in ammonia, which are stable for days, but solvated electrons also occur in water and many other solvents – in fact, in any solvent that mediates outer-sphere electron transfer. The solvated electron is responsible for a great deal of radiation chemistry.

Sodium atoms have 11 electrons, one more than the stable configuration of the noble gas neon. As a result, sodium usually forms ionic compounds involving the Na+ cation. Sodium is a reactive alkali metal and is much more stable in ionic compounds. It can also form intermetallic compounds and organosodium compounds. Sodium compounds are often soluble in water.

<span class="mw-page-title-main">Borohydride</span>

Borohydride refers to the anion [BH4], which is also called tetrahydridoborate, and its salts. Borohydride or hydroborate is also the term used for compounds containing [BH4−nXn], where n is an integer from 0 to 3, for example cyanoborohydride or cyanotrihydroborate [BH3(CN)] and triethylborohydride or triethylhydroborate [BH(CH2CH3)3]. Borohydrides find wide use as reducing agents in organic synthesis. The most important borohydrides are lithium borohydride and sodium borohydride, but other salts are well known. Tetrahydroborates are also of academic and industrial interest in inorganic chemistry.

An alkalide is a chemical compound in which alkali metal atoms are anions with a charge or oxidation state of −1. Until the first discovery of alkalides in the 1970s, alkali metals were known to appear in salts only as cations with a charge or oxidation state of +1. These types of compounds are of theoretical interest due to their unusual stoichiometry and low ionization potentials. Alkalide compounds are chemically related to the electrides, salts in which trapped electrons are effectively the anions.

Lithium superoxide is an unstable inorganic salt with formula LiO2. A radical compound, it can be produced at low temperature in matrix isolation experiments, or in certain nonpolar, non-protic solvents. Lithium superoxide is also a transient species during the reduction of oxygen in a lithium–air galvanic cell, and serves as a main constraint on possible solvents for such a battery. For this reason, it has been investigated thoroughly using a variety of methods, both theoretical and spectroscopic.

<span class="mw-page-title-main">Sodium perrhenate</span> Chemical compound

Sodium perrhenate (also known as sodium rhenate(VII)) is the inorganic compound with the formula NaReO4. It is a white salt that is soluble in water. It is a common precursor to other rhenium compounds. Its structure resembles that of sodium perchlorate and sodium permanganate.

<span class="mw-page-title-main">Birch reduction</span> Organic reaction used to convert arenes to cyclohexadienes

The Birch reduction is an organic reaction that is used to convert arenes to 1,4-cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch and involves the organic reduction of aromatic rings in an amine solvent with an alkali metal and a proton source. Unlike catalytic hydrogenation, Birch reduction does not reduce the aromatic ring all the way to a cyclohexane.

<span class="mw-page-title-main">Metal amides</span>

Metal amides (systematic name metal azanides) are a class of coordination compounds composed of a metal center with amide ligands of the form NR2. Amido complexes of the parent amido ligand NH2 are rare compared to complexes with diorganylamido ligand, such as dimethylamido. Amide ligands have two electron pairs available for bonding.

<span class="mw-page-title-main">Pentaamine(dinitrogen)ruthenium(II) chloride</span> Chemical compound

Pentaamine(nitrogen)ruthenium(II) chloride is an inorganic compound with the formula [Ru(NH3)5(N2)]Cl2. It is a nearly white solid, but its solutions are yellow. The cationic complex is of historic significance as the first compound with N2 bound to a metal center. [Ru(NH3)5(N2)]2+ adopts an octahedral structure with C4v symmetry.

<span class="mw-page-title-main">Transition metal nitrite complex</span> Chemical complexes containing one or more –NO₂ ligands

In organometallic chemistry, transition metal complexes of nitrite describes families of coordination complexes containing one or more nitrite ligands. Although the synthetic derivatives are only of scholarly interest, metal-nitrite complexes occur in several enzymes that participate in the nitrogen cycle.

References

  1. Dye, J. L. (2003). "Electrons as Anions". Science . 301 (5633): 607–608. doi:10.1126/science.1088103. PMID   12893933. S2CID   93768664.
  2. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN   0-12-352651-5
  3. Zurek, Eva; Edwards, Peter P.; Hoffmann, Roald (2009-10-19). "A Molecular Perspective on Lithium–Ammonia Solutions". Angewandte Chemie International Edition. 48 (44): 8198–8232. doi:10.1002/anie.200900373. ISSN   1433-7851.
  4. Buchammagari, H.; et al. (2007). "Room Temperature-Stable Electride as a Synthetic Organic Reagent: Application to Pinacol Coupling Reaction in Aqueous Media". Org. Lett. 9 (21): 4287–4289. doi:10.1021/ol701885p. PMID   17854199.
  5. Wagner, M. J.; Huang, R. H.; Eglin, J. L.; Dye, J. L. (1994). "An electride with a large six-electron ring". Nature. 368 (6473): 726–729. Bibcode:1994Natur.368..726W. doi:10.1038/368726a0. S2CID   4242499.{{cite journal}}: CS1 maint: multiple names: authors list (link).
  6. Wickleder, Mathias S.; Fourest, Blandine; Dorhout, Peter K. (2006). "Thorium". In Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (PDF). Vol. 3 (3rd ed.). Dordrecht, the Netherlands: Springer. pp. 78–94. doi:10.1007/1-4020-3598-5_3. Archived from the original (PDF) on 2016-03-07.
  7. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1240–2. ISBN   978-0-08-037941-8.
  8. Nief, F. (2010). "Non-classical divalent lanthanide complexes". Dalton Trans. 39 (29): 6589–6598. doi:10.1039/c001280g. PMID   20631944.
  9. Day, Craig S.; Do, Cuong Dat; Odena, Carlota; Benet-Buchholz, Jordi; Xu, Liang; Foroutan-Nejad, Cina; Hopmann, Kathrin H.; Martin, Ruben (13 July 2022). "Room-Temperature-Stable Magnesium Electride via Ni(II) Reduction". J. Am. Chem. Soc. 144 (29): 13109–13117. doi:10.1021/jacs.2c01807. hdl: 10037/32484 .
  10. Hosono, Hideo; Kitano, Masaaki (2021). "Advances in Materials and Applications of Inorganic Electrides". Chemical Reviews. 121 (5): 3121–3185. doi:10.1021/acs.chemrev.0c01071. PMID   33606511.
  11. Greenlee, K. W.; Henne, A. L. (1946). "Sodium Amide". Inorganic Syntheses. Vol. 2. pp. 128–135. doi:10.1002/9780470132333.ch38. ISBN   9780470132333.
  12. Postils, Verònica; Garcia-Borràs, Marc; Solà, Miquel; Luis, Josep M.; Matito, Eduard (2015-03-05). "On the existence and characterization of molecular electrides". Chemical Communications. 51 (23): 4865–4868. doi:10.1039/C5CC00215J. ISSN   1364-548X.
  13. Marques M.; et al. (2009). "Potassium under Pressure: A Pseudobinary Ionic Compound". Physical Review Letters . 103 (11): 115501. Bibcode:2009PhRvL.103k5501M. doi:10.1103/PhysRevLett.103.115501. PMID   19792381.
  14. Gatti M.; et al. (2010). "Sodium: A Charge-Transfer Insulator at High Pressures". Physical Review Letters . 104 (11): 216404. arXiv: 1003.0540 . Bibcode:2010PhRvL.104u6404G. doi:10.1103/PhysRevLett.104.216404. PMID   20867123. S2CID   18359072.
  15. Marques M.; et al. (2011). "Crystal Structures of Dense Lithium: A Metal-Semiconductor-Metal Transition" (PDF). Physical Review Letters . 106 (9): 095502. Bibcode:2011PhRvL.106i5502M. doi:10.1103/PhysRevLett.106.095502. PMID   21405633.
  16. Yu, Zheng; Geng, Hua Y.; Sun, Y.; Chen, Y. (2018). "Optical properties of dense lithium in electride phases by first-principles calculations". Scientific Reports . 8 (1): 3868. arXiv: 1803.05234 . Bibcode:2018NatSR...8.3868Y. doi:10.1038/s41598-018-22168-1. PMC   5832767 . PMID   29497122.
  17. Wang, Hui-Tian; Boldyrev, Alexander I.; Popov, Ivan A.; Konôpková, Zuzana; Prakapenka, Vitali B.; Zhou, Xiang-Feng; Dronskowski, Richard; Deringer, Volker L.; Gatti, Carlo (May 2017). "A stable compound of helium and sodium at high pressure". Nature Chemistry. 9 (5): 440–445. arXiv: 1309.3827 . Bibcode:2017NatCh...9..440D. doi:10.1038/nchem.2716. ISSN   1755-4349. PMID   28430195. S2CID   20459726.
  18. Racioppi, Stefano; Storm, Christian V.; McMahon, Malcolm I.; Zurek, Eva (2023-11-27). "On the Electride Nature of Na‐hP4". Angewandte Chemie International Edition. 62 (48). doi:10.1002/anie.202310802. ISSN   1433-7851.
  19. Neaton, J. B.; Ashcroft, N. W. (2001-03-26). "On the Constitution of Sodium at Higher Densities". Physical Review Letters. 86 (13): 2830–2833. doi:10.1103/PhysRevLett.86.2830.
  20. Zhang, Leilei; Geng, Hua Y.; Wu, Q. (2021-04-16). "Prediction of anomalous LA-TA splitting in electrides". Matter and Radiation at Extremes. 6 (3): 038403. arXiv: 2104.13151 . doi:10.1063/5.0043276. ISSN   2468-2047.
  21. Wang, Dan; Song, Hongxing; Zhang, Leilei; Wang, Hao; Sun, Yi; Wu, Fengchao; Chen, Ying; Chen, Xiangrong; Geng, Hua Y. (2024-02-01). "Universal Metallic Surface States in Electrides". The Journal of Physical Chemistry C. 128 (4): 1845–1854. arXiv: 2402.15798 . doi:10.1021/acs.jpcc.3c07496. ISSN   1932-7447.
  22. Zhang, Leilei; Wu, Qiang; Li, Shourui; Sun, Yi; Yan, Xiaozhen; Chen, Ying; Geng, Hua Y. (2021-02-10). "Interplay of Anionic Quasi-Atoms and Interstitial Point Defects in Electrides: Abnormal Interstice Occupation and Colossal Charge State of Point Defects in Dense fcc-Lithium". ACS Applied Materials & Interfaces. 13 (5): 6130–6139. arXiv: 2103.07605 . doi:10.1021/acsami.0c17095. ISSN   1944-8244.
  23. 1 2 Druffel, Daniel L.; Kuntz, Kaci L.; Woomer, Adam H.; Alcorn, Francis M.; Hu, Jun; Donley, Carrie L.; Warren, Scott C. (2016). "Experimental Demonstration of an Electride as a 2D Material". Journal of the American Chemical Society. 138 (49): 16089–16094. arXiv: 1706.02774 . doi:10.1021/jacs.6b10114. PMID   27960319. S2CID   19062953 . Retrieved 12 October 2021.
  24. Druffel, Daniel L.; Woomer, Adam H.; Kuntz, Kaci L.; Pawlik, Jacob T.; Warren, Scott C. (2017). "Electrons on the surface of 2D materials: from layered electrides to 2D electrenes" . Journal of Materials Chemistry C. 5 (43): 11196–11213. doi:10.1039/C7TC02488F . Retrieved 11 October 2021.

Further reading