Osmium(IV) chloride

Osmium(IV) chloride
IUPAC name Osmium(IV) chloride
Other names Osmium chloride, osmium tetrachloride
Identifiers
CAS number	10026-01-4
Properties
Molecular formula	OsCl4
Molar mass	332.041 g/mol
Appearance	red-black orthorhombic crystals
Density	4.38 g/cm³
Melting point	decomposes at 323°C
Solubility in water	reacts with water
Solubility	soluble in hydrochloric acid
Structure
Crystal structure	Orthorhombic, oS10
Space group	Cmmm, No. 65
Related compounds
Other anions	Osmium(IV) oxide
Other cations	Iron(III) chloride Ruthenium(III) chloride Osmium(III) chloride
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Osmium(IV) chloride or osmium tetrachloride is the inorganic compound composed of osmium and chlorine with the empirical formula 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.^[1] This route affords the high temperature polymorph:^[2]

Os + 2 Cl₂ → OsCl₄

This reddish-black polymorph is orthorhombic and adopts a structure in which osmium centres are octahedrally coordinated, sharing opposite edges of the OsCl₆ octahedra to form a chain.^[3] A brown, apparently cubic polymorph forms upon reduction of osmium tetroxide with thionyl chloride:^[4]

OsO₄ + 4 SOCl₂ → OsCl₄ + 2 Cl₂ + 4 SO₂

Osmium tetraoxide dissolves in hydrochloric acid to give the hexachloroosmate anion:

OsO₄ + 8 HCl → H₂OsCl₆ + Cl₂ + 4 H₂O

References

1. ^ Otto Ruff and Ferd. Bornemann (1910). "Über das Osmium, seine analytische Bestimmung, seine Oxyde und seine Chloride"". Zeitschrift für anorganische Chemie 65: 429–456. doi:10.1002/zaac.19100650126. 
2. ^ Cotton, S. A. (1997). Chemistry of Precious Metals. London: Chapman and Hall. ISBN 0751404136. 
3. ^ Wells A.F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford Science Publications. ISBN 0-19-855370-6. 
4. ^ Paul Machmer (1967). "On the polymorphism of osmium tetrachloride". Chem. Commun. (12): 610a–610a. doi:10.1039/C1967000610A.