Chromium (IV) fluoride

Crystal structure
Crystal structure of α-chromium tetrafluoride __ F -
General
Surname	Chromium (IV) fluoride
other names	Chromium tetrafluoride
Ratio formula	CrF 4
Brief description	green-black solid (α-chromium tetrafluoride) dark purple, crystalline solid (β-chromium tetrafluoride)
External identifiers / databases
CAS number 10049-11-3 (β-chromium tetrafluoride) PubChem 57346073 ChemSpider 52082975 Wikidata Q1087524
properties
Molar mass	127.99 g mol −1
Physical state	firmly
Melting point	100 ° C (α-chromium tetrafluoride, sublimation ) 227 ° C (β-chromium tetrafluoride)
solubility	Hydrolysis in water (α-chromium tetrafluoride)
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Chromium (IV) fluoride , also known as chromium tetrafluoride , is a chemical compound of the elements chromium and fluorine , in which chromium has the + IV oxidation state . There are two forms of this compound: α-chromium tetrafluoride (green-black solid that sublimes at 100 ° C) and β-chromium tetrafluoride (dark purple, crystalline solid that melts at 227 ° C).

Extraction and presentation

At higher temperatures, α-chromium tetrafluoride can be obtained from the elements:

${\displaystyle \mathrm {Cr+2\ F_{2}\ {\xrightarrow {300-350\,{}^{\circ }C}}\ CrF_{4}} }$

Further possibilities are the reaction of fluorine with chromium (III) fluoride or chromium (III) chloride :

${\displaystyle \mathrm {2\ CrF_{3}+F_{2}\longrightarrow 2\ CrF_{4}} }$

${\displaystyle \mathrm {2\ CrCl_{3}+4\ F_{2}\longrightarrow 2\ CrF_{4}+3\ Cl_{2}} }$

Chromium (III) fluoride and chloride react with fluorine to form α-chromium tetrafluoride even at room temperature.

β-chromium tetrafluoride is obtained by long-term thermolysis of chromium (V) fluoride :

${\displaystyle \mathrm {2\ CrF_{5}\ {\xrightarrow[{5Monate}]{130\,{}^{\circ }C}}\ 2\ CrF_{4}+F_{2}} }$

The 5-month long-term thermolysis of chromium pentafluoride results in β-chromium tetrafluoride.

properties

Physical Properties

α-Chromium tetrafluoride is made up of chains of trans-edge-linked CrF ₆ octahedra. β-Chromium tetrafluoride is made up of rings of 4 cis-corner-linked CrF ₆ octahedra, which are linked to tubes via common trans fluorine atoms, with each CrF ₆ octahedron remaining two cis free fluorine atoms.

Chemical properties

Chromium tetrafluoride forms several anionic fluorocomplexes with fluorides : CrF ₅ ^- , which are built up from CrF ₆ octahedral chains with common fluorine atoms; CrF ₆ ²⁻ , which are octahedral and CrF ₇ ³⁻ .

Individual evidence

1. ↑ ^{a b c d e f g h} A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1571.
2. ↑ β-chromium tetrafluoride on webelements.com
3. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .
4. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.