Interhalogen compounds

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An interhalogen compound ( Latin inter = between), also called interhalogen for short , is a chemical compound between two different halogens . The existing interhalogen compounds are very reactive under normal conditions .

General properties

In the case of interhalogen compounds, a more electropositive halogen X forms a compound with a more electronegative halogen Y. The types XY, XY 3 , XY 5 and XY 7 occur. The halogen X here accordingly has the oxidation states +1, +3, +5 and +7. The interhalogens are highly reactive oxidizing agents and can transfer halogens. The further the two halogens X and Y in the 7th group of the periodic table are from each other, the higher the tendency towards ionic splitting. The physical and chemical properties are mostly similar to those of the elemental halogens that make them up. All interhalogen compounds are produced by direct reaction of the two halogens, and the resulting product is determined by the proportions of the reactants.


Cl ClF , ClF 3 , ClF 5
Br BrF , BrF 3 , BrF 5 BrCl
I. IF , IF 3 , IF 5 , IF 7 ICl , ICl 3 IBr , IBr 3
F. Cl Br
  • All possible combinations of type XY (e.g .: iodine fluoride ) are known. With the exception of ICl 3 and IBr 3 , all other compounds are fluorine compounds , since otherwise the electronegativity difference is not great enough and halogens with larger atomic radii than fluorine interfere with one another.
  • The trihalides XY 3 are arranged in a T-shape. Iodine trichloride (ICl 3 ), chlorine trifluoride (ClF 3 ), bromine trifluoride (BrF 3 ) and iodine trifluoride (IF 3 ) were isolated . The dimer I 2 Cl 6 of the iodine trichloride ICl 3 is also known. The existence of iodine tribromide is also known.
  • The pentahalides XY 5 iodine pentafluoride (IF 5 ), bromine pentafluoride (BrF 5 ) and chlorine pentafluoride (ClF 5 ) have the geometry of square pyramids .
  • The only known stable heptahalide iodine heptafluoride (IF 7 ) has the structure of a pentagonal bipyramid .
  • Numerous interhalide anions with three, five or seven halogen atoms involved are also known (e.g. IBr 2 - , BrF 6 - or IF 6 - ). Interhalide cations (for example ICl 2 + ) are less common, but can also be isolated in stable compounds .
  • In a broader sense, combinations of halogens and pseudohalogens can also be counted among the interhalogens.

No d orbital is hybridized in any interhalogen compound . Rather, the fluorine atoms (in ICl 3 the chlorine atoms ) attach to free, unhybridized p orbitals and form a four-electron-three-center bond, in accordance with the octet rule .

Presentation and use

The interhalogens are made from the respective elements. Many compounds are used as halogenating agents , especially fluorinating agents. Halogen fluorides are weaker fluorinating agents than elemental fluorine, but the trifluorides ClF 3 and BrF 3 show a faster reaction rate.

Interhalofluorides are used in the production of uranium hexafluoride , which is used for uranium enrichment . However, other manufacturing processes also exist.

Iodine chloride and iodine trichloride are used to determine the iodine number of fats using the Wijs method (DIN 53241-1: 1995-05).


  • James E. Huheey: Inorganic Chemistry. Walter de Gruyter, Berlin, New York 1988, ISBN 3-11-008163-6 .
  • Duward F. Shriver, Peter Atkins , Cooper H. Langford: Inorganic Chemistry. A further textbook. Wiley-VCH, Weinheim 1992, ISBN 3-527-28105-3 .