Ammonium hexachloroosmate(IV)

Ammonium hexachloroosmate(IV)
Microcrystals of ammonium hexachloroosmate
Microcrystals of ammonium hexachloroosmate
Names
IUPAC name
Ammonium hexachloroosmate(IV)
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.977
EC Number
  • 235-188-5
  • 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 red crystals
Density 2.93 g/cm3
Melting point 170
poorly soluble
Hazards
GHS labelling:
GHS07: Exclamation mark[1]
Warning
NFPA 704 (fire diamond)
[2]
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
0
0
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.[3][4]

Synthesis

Ammonium hexachloroosmate(IV) can be produced by the reduction of osmium tetroxide or potassium osmate with iron dichloride in hydrochloric acid in the presence of ammonium ions:[5][6][7]

OsO4 + 4FeCl2 + 8HCl + 2NH4Cl → (NH4)2[OsCl6] + 3FeCl3 + 4H2O
K2[OsO2(OH)4] + FeCl2 + 2NH4Cl conc hcl
———→ (NH4)2OsCl6 + FeCl3 + 4H2O + 2KCl

It can also be prepared by addition of an ammonium chloride solution to hexachloroosmic acid,[8] or by addition of ammonium chloride to a solution of sodium hexachloroosmate.[9]

Physical properties

Ammonium hexachloroosmate(IV) forms dark red crystals of the cubic system,[10] space group Fm3m, cell parameters a = 0.9729 nm, Z = 4.

It is poorly soluble in cold water.[11]

Chemical properties

The compound is reduced by hydrogen to metallic osmium:[12][13]

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

Similar to sodium hexachloroosmate, ammonium hexachloroosmate decomposes to osmium dioxide when exposed to strong alkali, and reacts with ammonia to produce osmium diammine hydroxide, OsO(NH3)2(OH)2.[9]

Ammonium hexachloroosmate is stable in hydrochloric acid, but it is oxidized by nitric acid, forming osmium tetroxide.[14]

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.[7]

When ammonium hexachloroosmate is refluxed with diethylphenylphosphine, OsCl3(PEt2Ph)3 is formed.[15]

Uses

The compound is used as a pharmaceutical, organic, and chemical intermediate.[16]

References

  1. ^ "Ammonium hexachloroosmate(IV)". Sigma Aldrich. Retrieved 17 October 2024.
  2. ^ "AMMONIUM HEXACHLOROOSMATE(IV)". Chemical Book. Retrieved 16 July 2025.
  3. ^ "Ammonium Hexachloroosmate". American Elements. Retrieved 17 October 2024.
  4. ^ Brauer, Georg (2 December 2012). Handbook of Preparative Inorganic Chemistry V2. Elsevier. p. 1603. ISBN 978-0-323-16129-9. Retrieved 17 October 2024.
  5. ^ 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)
  6. ^ Inorganic Syntheses, Volume 5. John Wiley & Sons. 22 September 2009. p. 206. ISBN 978-0-470-13268-5. Retrieved 17 October 2024.
  7. ^ a b 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 (ICCEACT): 31–33. Retrieved 15 July 2025.
  8. ^ 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.
  9. ^ 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.
  10. ^ 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.
  11. ^ 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.
  12. ^ 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.
  13. ^ 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.
  14. ^ 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.
  15. ^ Buckingham, D.A. (1961). Preparation and Oxidation-Reduction Potentials of Some Osmium Compounds (PhD thesis). Australian National University. p. 12.
  16. ^ "Ammonium hexachloroosmate(IV), 99.9% (metals basis), Os 42.5% min, Thermo Scientific Chemicals". Fisher Scientific. Retrieved 17 October 2024.
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