Triosmium dodecacarbonyl

Triosmium dodecacarbonyl is a chemical compound with the formula Os₃(CO)₁₂. This yellow-colored metal carbonyl cluster is an important precursor to organo-osmium compounds. Many of the advances in cluster chemistry have arisen from studies on derivatives of Os₃(CO)₁₂ and its lighter analogue Ru₃(CO)₁₂.

Triosmium dodecacarbonyl

Names
IUPAC name cyclo-tris(tetracarbonylosmium)(3 Os—Os)
Other names Osmium carbonyl
Identifiers
CAS Number	15696-40-9 Y
3D model (JSmol)	Interactive image
ChemSpider	452847
ECHA InfoCard	100.036.157
PubChem CID	6096995
CompTox Dashboard (EPA)	DTXSID50166160
InChI InChI=1S/12CO.3Os/c12*1-2;;; Key: VUBLMKVEIPBYME-UHFFFAOYSA-N
SMILES [C-]#[O+].[C-]#[O+].[C-]#[O+].[C-]#[O+].[C-]#[O+].[C-]#[O+].[C-]#[O+].[C-]#[O+].[C-]#[O+].[C-]#[O+].[C-]#[O+].[C-]#[O+].[Os].[Os].[Os]
Properties
Chemical formula	C12O12Os3
Molar mass	906.81 g/mol
Appearance	yellow solid
Density	3.48 g/cm3
Melting point	224 °C (435 °F; 497 K)
Boiling point	sublimes in vacuum
Solubility in water	insoluble
Solubility in other solvents	slightly in organic solvents
Structure
Dipole moment	0 D (0 C·m)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	CO source
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H302, H315, H319, H330, H335
Precautionary statements	P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P340, P305+P351+P338, P312, P321, P330, P332+P313, P337+P313, P362, P403+P233, P405, P501
Related compounds
Related compounds	Fe3(CO)12 Ru3(CO)12 Decacarbonyldihydridotriosmium
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Structure and synthesis

The cluster has D_3h symmetry, consisting of an equilateral triangle of Os atoms, each of which bears two axial and two equatorial CO ligands. Each of the three osmium centers has an octahederal structure with four CO ligands and the other two osmium atoms.

The Os–Os bond distance is 2.88 Å (288 pm).^[1][2] Ru₃(CO)₁₂ has the same structure, whereas Fe₃(CO)₁₂ is different, with two bridging CO ligands resulting in C_2v symmetry. In solution, Os₃(CO)₁₂ is fluxional as indicated by ¹³C NMR measurements. The barrier is estimated at 70 kJ/mol^[3]

Os₃(CO)₁₂ is prepared by the direct reaction of OsO₄ with carbon monoxide at 175 °C under high pressures:^[4]

3 OsO₄ + 24 CO → Os₃(CO)₁₂ + 12 CO₂

The yield is nearly quantitative.

Reactions

Many chemical reactions of Os₃(CO)₁₂ have been examined. Direct reactions of ligands with the cluster often lead to complex product distributions. Os₃(CO)₁₂ converts to more labile derivatives such as Os₃(CO)₁₁(MeCN) and Os₃(CO)₁₀(MeCN)₂ using Me₃NO as a decarbonylating agent:^[5]

Os₃(CO)₁₂ + (CH₃)₃NO + CH₃CN → Os₃(CO)₁₁(CH₃CN) + CO₂ + (CH₃)₃N

Os₃(CO)₁₁(CH₃CN) + (CH₃)₃NO + CH₃CN → Os₃(CO)₁₀(CH₃CN)₂ + CO₂ + (CH₃)₃N

Os₃(CO)₁₁(MeCN) reacts with a variety of even weakly basic ligands to form adducts.

Purging a solution of triosmium dodecacarbonyl in boiling octane (or similar inert solvent of similar boiling point) with H₂ gives the dihydride Os₃H₂(CO)₁₀:^[6]

Os₃(CO)₁₂ + H₂ → Os₃H₂(CO)₁₀ + 2 CO

Osmium pentacarbonyl is obtained by treating solid triosmium dodecacarbonyl with 200 atmospheres of carbon monoxide at 280-290 °C.^[7]

Os₃(CO)₁₂ + 3 CO → 3 Os(CO)₅

References

1. Corey, E. R.; Dahl, L. F. "The Molecular and Crystal Structure of Os₃(CO)₁₂" Inorganic Chemistry 1962, volume 1, pages 521–526; doi:10.1021/ic50003a016.
2. Churchill, Melvyn Rowen; DeBoer, Barry G. (1977). "Structural studies on polynuclear osmium carbonyl hydrides. 1. Crystal structures of the isomorphous species H₂Os₃(CO)₁₁ and Os₃(CO)₁₂. Role of an equatorial μ₂-bridging hydride ligand in perturbing the arrangement of carbonyl ligands in a triangular cluster". Inorg. Chem. 16 (4): 878–884. doi:10.1021/ic50170a032.
3. Farrugia, Louis J. (1997). "Dynamics and Fluxionality in Metal Carbonyl Clusters: Some Old and New Problems". Journal of the Chemical Society, Dalton Transactions (11): 1783–1792. doi:10.1039/A608514H.
4. Drake, S. R.; Loveday, P. A. "Dodecarbonyltriosmium" Inorganic Syntheses, 1990, volume 28, pages 230–231. ISBN 0-471-52619-3.
5. Nicholls, J. N.; Vargas, M. D. "Some Useful Derivatives of Dodecarbonyltriosmium" Inorganic Syntheses, 1990, volume 28, pages 232–235. ISBN 0-471-52619-3.
6. Kaesz, H. D. (1990). "Decacarbonyldi-μ-Hydridotriosmium: Os ₃ (μ-H) ₂ (Co) ₁₀". Decacarbonyldi-μ-Hydridotriosmium: Os₃(μ-H)₂(CO)₁₀. Inorganic Syntheses. Vol. 28. pp. 238–39. doi:10.1002/9780470132593.ch60. ISBN 9780471526193.
7. 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.