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Osmium pentacarbonyl
Identifiers
CAS Number	16406-49-8;
3D model (JSmol)	Interactive image;
ChemSpider	65793451;
PubChem CID	10892861;
CompTox Dashboard (EPA)	DTXSID901336738 ;
	InChI InChI=1S/5CO.Os/c5*1-2; Key: RLUHVGZGDXPTEM-UHFFFAOYSA-N;
	SMILES C(=O)=[Os](=C=O)(=C=O)(=C=O)=C=O;
Properties
Chemical formula	C5O5Os
Molar mass	330.28 g·mol−1
Appearance	colorless liquid
Melting point	2–2.5 °C (35.6–36.5 °F; 275.1–275.6 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Osmium pentacarbonyl is the organoosmium compound with the formula Os(CO)₅. It is the simplest isolatable carbonyl complex of osmium. Osmium pentacarbonyl is a colorless volatile liquid that is obtained by treating solid triosmium dodecacarbonyl under 200 atmospheres of carbon monoxide at 280-290 °C. In contrast, also at 200 atm of CO, solid Ru₃(CO)₁₂ converts to Ru(CO)₅ at milder temperature of 160 °C.^[1]

Reactions

Samples of Os(CO)₅ convert back to the trioosmium cluster upon heating to 80 °C. The analogous conversion of Ru(CO)₅ back to Ru₃(CO)₁₂ occurs at room temperature.^[1] Chlorination of the pentacarbonyl gives a cationic pentacarbonyl complex:^[1]

Os(CO)₅ + Cl₂ → [Os(CO)₅Cl]⁺Cl⁻

Upon UV irradiation, hexane solutions of the pentacarbonyl react with ethylene to give mono-, di-, and trisubstituted derivatives:^[3]

Os(CO)₅ + n C₂H₄ → Os(CO)_5-n(C₂H₄)_n + n CO (n = 1,2,3)

References

^ ^a ^b ^c Rushman, Paul; Van Buuren, Gilbert N.; Shiralian, Mahmoud; Pomeroy, Roland K. (1983). "Properties of the Pentacarbonyls of Ruthenium and Osmium". Organometallics. 2 (5): 693–694. doi:10.1021/om00077a026.
^ Moss, John R.; Graham, William A. G. (1977). "The Enneacarbonyls of Ruthenium and Osmium". Journal of the Chemical Society, Dalton Transactions: 95. doi:10.1039/DT9770000095.
^ Kiel, Gong Yu; Takats, Josef; Grevels, Friedrich Wielhelm (1987). "Multisubstitution of Os(CO)₅ by ethylene: Isomeric Os(CO)₂(C₂H₄)₃ and a Derivative of Os(CO)(C₂H₄)₄". Journal of the American Chemical Society. 109 (7): 2227–2229. doi:10.1021/ja00241a075.