Ammonium hexachloroosmate(IV)

Ammonium hexachloroosmate(IV)

Microcrystals of ammonium hexachloroosmate
Names
IUPAC name Ammonium hexachloroosmate(IV)
Identifiers
CAS Number	12125-08-5
3D model (JSmol)	Interactive image
ChemSpider	145801
ECHA InfoCard	100.031.977
EC Number	235-188-5
PubChem CID	11729867
CompTox Dashboard (EPA)	DTXSID70923737
InChI InChI=1S/6ClH.2H3N.Os/h6*1H;2*1H3;/q;;;;;;;;+4/p-4 Key: SRBXXQDKBKTWOC-UHFFFAOYSA-J
SMILES [NH4+].[NH4+].Cl[Os-2](Cl)(Cl)(Cl)(Cl)Cl
Properties
Chemical formula	Cl6H8N2Os
Molar mass	439.01 g·mol−1
Appearance	red crystals
Density	2.93 g/cm3
Melting point	170
Solubility in water	poorly soluble
Hazards
GHS labelling:
Pictograms	[1]
Signal word	Warning
NFPA 704 (fire diamond)	[2] 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.
6. Inorganic Syntheses, Volume 5. John Wiley & Sons. 22 September 2009. p. 206. ISBN   978-0-470-13268-5 . Retrieved 17 October 2024.
7. 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. 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.