Osmium(IV) chloride or osmium tetrachloride is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

composed of

osmium Osmium () is a chemical element; it has Symbol (chemistry), symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a Abundance of elements in Earth's crust, trace element in a ...

and

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

with the

empirical formula In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulfur monoxide, or SO, is simply SO, as is the empir ...

OsCl₄. It exists in two polymorphs (crystalline forms). The compound is used to prepare other osmium complexes.

Preparation, structure, reactions

It was first reported in 1909 as the product of chlorination of osmium metal. This route affords the high temperature polymorph: :Os + 2 Cl₂ → OsCl₄ This reddish-black polymorph is

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...

and adopts a structure in which osmium centres are octahedrally coordinated, sharing opposite edges of the OsCl₆ octahedra to form a chain. A brown, apparently cubic polymorph forms upon reduction of

osmium tetroxide Osmium tetroxide (also osmium(VIII) oxide) is the chemical compound with the formula OsO4. The compound is noteworthy for its many uses, despite its toxicity and the rarity of osmium. It also has a number of unusual properties, one being that the ...

with

thionyl chloride Thionyl chloride is an inorganic compound with the chemical formula . It is a moderately Volatility (chemistry), volatile, colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a Halogenation, chlorinating reagen ...

: :OsO₄ + 4 SOCl₂ → OsCl₄ + 2 Cl₂ + 4 SO₂ Osmium tetraoxide dissolves in

hydrochloric acid Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...

to give the hexachloroosmate anion: :OsO₄ + 10 HCl → H₂OsCl₆ + 2 Cl₂ + 4 H₂O

References

{{Chlorides Osmium compounds Chlorides Platinum group halides