Beryllium fluoride

Structural formula
General
Surname	Beryllium fluoride
other names	Beryllium (II) fluoride Beryllium difluoride
Molecular formula	BeF 2
Brief description	colorless, glass-like mass.
External identifiers / databases
CAS number 7787-49-7 EC number 232-118-5 ECHA InfoCard 100.029.198 PubChem 24589 ChemSpider 22992 Wikidata Q416310
properties
Molar mass	47.01 g mol −1
Physical state	firmly
density	1.99 g cm −3
Melting point	555 ° C
solubility	soluble in water, slightly soluble in alcohols
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 350i-330-301-372-319-335-315-317-411 P: 260-301 + 310-305 + 351 + 338-320-405-501
MAK	repealed because it is carcinogenic
Toxicological data	98 mg kg −1 ( LD 50 ,  rat ,  oral )
Thermodynamic properties
ΔH f 0	−1026.8 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Beryllium (II) fluoride is a chemical compound of beryllium and fluorine with the formula BeF ₂ .

Extraction and presentation

Beryllium fluoride can be obtained by thermolysis of ammonium tetrafluoridoberyllate (II) (a beryllium complex compound that can be obtained by reacting beryllium oxide (BeO) with ammonium fluoride (NH ₄ F)) at ~ 900 ° C.

${\displaystyle \mathrm {(NH_{4})_{2}BeF_{4}\longrightarrow \ BeF_{2}+2\ NH_{4}F} }$

properties

Beryllium fluoride has strong covalent bond components, which is why it does not form an ion lattice , but rather has a polymeric structure in the solid that is isotypic with α-quartz (<430 ° C) or β- cristobalite (> 516 ° C). Each beryllium core is tetrahedral surrounded by four fluorine cores. This is in contrast to isoelectronic carbon dioxide (CO ₂ ), but is consistent with isoelectronic silicon dioxide (SiO ₂ ). In the polymer structure, each fluorine core bridges two beryllium cores. Here, the oblique relationship between beryllium and aluminum becomes clear, which shows similar behavior.

Gaseous beryllium fluoride exists as a linear monomer . It forms a weak π bond from fluorine to beryllium to compensate for its lack of electrons. The Be-F distance is 143 pm .

Monomeric beryllium fluoride

As with all beryllium (II) halides, beryllium fluoride is a Lewis acid , so that it can form fluoroberyllates such as BeF ₄ ²⁻ with fluorides .

hydrolysis

In contrast to the other Berylliumhalogeniden which dissociate in water directly in hydrated beryllium and the corresponding anion, which is hydrolysis of beryllium a complex sequence of reactions based on starting with an adduct formation followed by autoionization .

${\displaystyle \mathrm {BeF_{2}+2\ H_{2}O\ \rightleftharpoons \ [BeF_{2}(H_{2}O)_{2}]} }$ ${\displaystyle \mathrm {2\ [BeF_{2}(H_{2}O)_{2}]\ \rightleftharpoons \ [BeF_{3}(H_{2}O)]^{-}+[BeF(H_{2}O)_{3}]^{+}} }$ ${\displaystyle \mathrm {2\ [BeF_{3}(H_{2}O)]^{-}\ \rightleftharpoons \ [BeF_{4}]^{2-}+[BeF_{2}(H_{2}O)_{2}]} }$ ${\displaystyle \mathrm {2\ [BeF(H_{2}O)_{3}]^{+}\ \rightleftharpoons \ [BeF_{2}(H_{2}O)_{2}]+[Be(H_{2}O)_{4}]^{2+}} }$

The aqueous solution ultimately reacts acidic because of the deprotonation of the aqua complex:

${\displaystyle \mathrm {[Be(H_{2}O)_{4}]^{2+}+H_{2}O\ \rightleftharpoons \ H_{3}O^{+}+[Be(H_{2}O)_{3}(OH)]^{+}} }$

use

Beryllium fluoride is used as the starting material for the production of pure beryllium, which can be obtained by reducing beryllium fluoride with magnesium at 1300 ° C.

${\displaystyle \mathrm {BeF_{2}+\ Mg\longrightarrow \ Be+\ MgF_{2}} }$

It is also used for the manufacture of glasses and in reactor technology.

safety instructions

Like all beryllium compounds, beryllium fluoride is highly toxic and is classified as carcinogenic.

Individual evidence

1. ↑ Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 242.
2. ↑ ^{a b c d e f} Entry on beryllium fluoride in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
3. ↑ National Institute of Environmental Health Sciences , 13th Report on Carcinogens (RoC): Beryllium and Beryllium Compounds ( Memento of the original dated November 29, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed November 18, 2014. 
4. ↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the specified labeling it falls under the group entry beryllium compounds, with the exception of beryllium alumina silicates, and with the exception of those named in this annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on January 9, 2017. Manufacturers or distributors can expand the harmonized classification and labeling .
5. ↑ Data sheet Beryllium fluoride at AlfaAesar, accessed on May 5, 2016 ( PDF )(JavaScript required) .
6. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-6.
7. ↑ Beryllium fluoride at Webelements .
8. ↑ G. Brauer (Ed.), Handbook of Preparative Inorganic Chemistry. 2nd Edition. vol. 1, Academic Press 1963, pp. 231-232.
9. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , pp. 1108-1109.
10. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1216.
11. ↑ Entry on beryllium compounds. In: Römpp Online . Georg Thieme Verlag, accessed on July 15, 2014.