Ammonium hexachloroosmate(IV)

Ammonium hexachloroosmate(IV)
Names
IUPAC name
Ammonium hexachloroosmate(IV)
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.977
EC Number
  • 235-188-5
UNII
  • InChI=1S/6ClH.2H3N.Os/h6*1H;2*1H3;/q;;;;;;;;+4/p-4
    Key: SRBXXQDKBKTWOC-UHFFFAOYSA-J
  • [NH4+].[NH4+].Cl[Os-2](Cl)(Cl)(Cl)(Cl)Cl
Properties
Cl6H8N2Os
Molar mass 439.01 g·mol−1
Appearance Dark red
Density 2.93 g/cm3
Melting point 170
poorly soluble
Hazards
GHS labelling:
[1]
Warning
Related compounds
Other anions
 Ammonium hexachloroplatinate,
Ammonium hexachloropalladate,
Ammonium hexachloroiridate,
Ammonium hexachlororhodate(III)
Other cations
 Sodium hexachloroosmate,
Potassium hexachloroosmate,
Hexachloroosmic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Ammonium hexachloroosmate(IV) is an inorganic chemical compound with the chemical formula (NH4)2OsCl6.[2][3]

Synthesis

Ammonium hexachloroosmate(IV) can be produced by the reduction of osmium tetroxide with iron dichloride in hydrochloric acid in the presence of ammonium ions:[4][5]

OsO4 + 4FeCl2 + 8HCl + 2NH4Cl → (NH4)2[OsCl6] + 3FeCl3 + 4H2O

It can also be prepared by addition of an ammonium chloride solution to hexachloroosmic acid,[6] or by addition of ammonium chloride to a solution of sodium hexachloroosmate.[7]

H2OsCl6 + 2NH4Cl → (NH4)2OsCl6 + 2HCl

Physical properties

Ammonium hexachloroosmate(IV) forms dark red crystals of the cubic system,[8] space group Fm3m, cell parameters a = 0.9729 nm, Z = 4.

It dissolves sparingly in water to form greenish-yellow solutions. It is insoluble in alcohol.[9][4][10]

Chemical properties

The compound is reduced by hydrogen to metallic osmium:[11][12]

3(NH4)2[OsCl6] → 3Os + 2N2 + 16HCl + 2NH4Cl
(NH4)2[OsCl6] + 2H2 → Os + NH4Cl + 4HCl

Ammonium hexachloroosmate is stable in hydrochloric acid, but it is oxidized by nitric acid, forming osmium tetroxide. When exposed to strong alkali, it reacts to produce osmium oxydiammine dihydroxide, OsO(NH3)2(OH)2.[7][13]

It can hydrolyze, whereby it forms osmium dioxide. It can also undergo a reversible aquation, producing the aquopentachloroosmate anion.[14]

[OsCl6]2- + H2O ⇌ [Os(OH2)Cl5]- + Cl-

Reactions

Ammonium hexachloroosmate reacts with triphenylphosphine to form various complexes in which osmium is divalent.

(NH4)2OsCl6 + 4PPh3 2-(2-methoxyethoxy)ethanol
———————————→ OsHCl(CO)(PPh3)3 + 2NH4Cl + 2PPh3Cl2

(NH4)2OsCl6 + 6PPh3 2-methoxyethanol
———————→ OsH2(CO)(PPh3)3 + 2NH4Cl + 3PPh3Cl2

It also reacts with triphenylphosphine in a solution of t-butyl alcohol and water to produce OsCl2(PPh3)3.[15]

When ammonium hexachloroosmate is refluxed with diethylphenylphosphine, OsCl3(PEt2Ph)3 is formed.[16]

It reacts with hydrazine hydrate to form a variety of different products, chief of which are [Os(NH3)5(N2)]Cl2 and [(NH3)5OsNOs(NH3)5]Cl5•H2O.[17]

Uses

The compound is used as a pharmaceutical, organic, and chemical intermediate.[18]

References

  1. ^ "Ammonium hexachloroosmate(IV)". Sigma Aldrich. Retrieved 17 October 2024.
  2. ^ "Ammonium Hexachloroosmate". American Elements. Retrieved 17 October 2024.
  3. ^ Brauer, Georg (2 December 2012). Handbook of Preparative Inorganic Chemistry V2. Elsevier. p. 1603. ISBN 978-0-323-16129-9. Retrieved 17 October 2024.
  4. ^ a b Dwyer, F. P.; Hogarth, J. W.; Rhoda, Richard N. (January 1957). "Ammonium Hexachloroosmate(IV)". Inorganic Syntheses. Inorganic Syntheses. Vol. 5. pp. 206–207. doi:10.1002/9780470132364.ch60. ISBN 978-0-470-13164-0. Retrieved 17 October 2024. {{cite book}}: ISBN / Date incompatibility (help)
  5. ^ Inorganic Syntheses, Volume 5. John Wiley & Sons. 22 September 2009. p. 206. ISBN 978-0-470-13268-5. Retrieved 17 October 2024.
  6. ^ Gilchrist, Raleigh (1931). "A method for the separation and gravimetric determination of osmium" (PDF). J Res Bur Stand. 6 (3): 428. doi:10.6028/jres.006.028. Retrieved 15 July 2025.
  7. ^ a b J. Newton Friend (1920). "Osmium and its compounds". A textbook of inorganic chemistry, vol.IX Part I Cobalt, Nickel, and The Elements of The Platinum Group (PDF). London: Charles Griffin and Company, Limited. p. 216. Retrieved 3 July 2025.
  8. ^ Armarego, W. L. F. (27 August 2022). Purification of Laboratory Chemicals: Part 2 Inorganic Chemicals, Catalysts, Biochemicals, Physiologically Active Chemicals, Nanomaterials. Butterworth-Heinemann. p. 7. ISBN 978-0-323-95828-8. Retrieved 17 October 2024.
  9. ^ Comey, Arthur Messinger (1896). A Dictionary of chemical solubilities, inorganic (PDF). London: MacMillan and Co. p. 115. Retrieved 12 May 2026.
  10. ^ Haynes, William M. (19 April 2016). CRC Handbook of Chemistry and Physics, 94th Edition. CRC Press. p. 4-46. ISBN 978-1-4665-7115-0. Retrieved 17 October 2024.
  11. ^ Lay, Peter A.; Magnuson, Roy H.; Taube, Henry; Vassilian, Asbed (January 1986). "Pentaammineosmium(III) and Hexaammineosmium(III) Complexes". Inorganic Syntheses. Vol. 24. pp. 269–277. doi:10.1002/9780470132555.ch73. ISBN 978-0-471-83441-0. Retrieved 17 October 2024.
  12. ^ Meyer, Gerd; Möller, Angela (30 June 1991). "Thermolysis of ternary ammonium chlorides of rhenium and the noble metals". Journal of the Less Common Metals. 170 (2): 327–331. doi:10.1016/0022-5088(91)90336-3. ISSN 0022-5088. Retrieved 17 October 2024.
  13. ^ Gaines, Paul; Kozikowski, Thomas; Alexander, Brian (2021). "Tracing an Osmium Solution Standard to the International System of Units". Analytical Chemistry. 93: 15642–15650. Retrieved 15 July 2025.
  14. ^ Miano, Ralph R.; Garner, Clifford S. (1965). "Kinetics of Aquation of Hexachloroosmate(IV) and Chloride Anation of Aquopentachloroosmate(IV) Anions". Inorganic Chemistry. 4 (4): 337–342. Retrieved 27 May 2026.
  15. ^ Chiririwa, Haleden; Muzenda, Edison (November 2014). "The Preparation and Characterisation of Osmium (IV), Osmium (II), and Osmium (0) Complexes from Refinery Materials" (PDF). International Conference on Chemical Engineering & Advanced Computational Technologies: 31–33. Retrieved 15 July 2025.
  16. ^ Buckingham, D.A. (1961). Preparation and Oxidation-Reduction Potentials of Some Osmium Compounds (PhD thesis). Australian National University. p. 12.
  17. ^ Lay, Peter A.; Taube, Henry (1989). "Reactions of Hexachloroosmate(IV) with Hydrazine Hydrate: Syntheses and Properties of Pentaammine(dinitrogen)osmium(II) Chloride, and Decaammine(μ-nitrido)diosmium(IV) chloride". Inorganic Chemistry. 28 (18): 3561–3564. Retrieved 27 May 2026.
  18. ^ "Ammonium hexachloroosmate(IV), 99.9% (metals basis), Os 42.5% min, Thermo Scientific Chemicals". Fisher Scientific. Retrieved 17 October 2024.
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