Triruthenium dodecacarbonyl

Triruthenium dodecarbonyl is the chemical compound with the formula Ru₃(CO)₁₂. This orange-colored metal carbonyl cluster is an important precursor to organo-ruthenium compounds.

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Structure and synthesis

The cluster has D_3h symmetry, consisting of an equilateral triangle of Ru atoms, each of which bears two axial and two equatorial CO ligands.^[1] Os₃(CO)₁₂ has the same structure, whereas Fe₃(CO)₁₂ is different, with two bridging CO ligands, resulting in C_2v symmetry.

Ru₃(CO)₁₂ is prepared by heating a methanol solution of ruthenium trichloride under a high pressure of carbon monoxide at 250 °C.^[2] The stoichiometry of the reaction is uncertain, one possibility being the following:

6 RuCl₃ + 33 CO → 2 Ru₃(CO)₁₂ + 9 COCl₂

Reactions

The chemical properties of Ru₃(CO)₁₂ have been well developed and this species can be converted to hundreds of derivatives.

High pressures of CO convert the cluster to the monomeric pentacarbonyl, that reverts back to the parent cluster upon standing.

Ru₃(CO)₁₂ + 3 CO → 3 Ru(CO)₅ K_eq = 3.3 x 10^-7 mol dm^–3 at room temperature

The instability of Ru(CO)₅ contrasts sharply with the robustness of the corresponding Fe(CO)₅. The condensation of Ru(CO)₅ into Ru₃(CO)₁₂ proceeds via initial, rate-limiting loss of CO to give the unstable, coordinatively unsaturated species Ru(CO)₄. This tetracarbonyl binds Ru(CO)₅, initiating the condensation.^[3]

Upon warming under a pressure of hydrogen, Ru₃(CO)₁₂ converts to the tetrahedral cluster H₄Ru₄(CO)₁₂.^[4] Ru₃(CO)₁₂ undergoes substitution reactions with Lewis bases:

Ru₃(CO)₁₂ + n L → Ru₃(CO)_12-nL_n + n CO

where L is a tertiary phosphine or an isonitrile.

Ru-carbido clusters

At high temperatures, Ru₃(CO)₁₂ converts to a series of clusters that contain interstitial carbido ligands. These include Ru₆C(CO)₁₇ and Ru₅C(CO)₁₅. Anionic carbido clusters are also known, including Ru₅C(CO)₁₄^2- and the bioctahedral cluster [Ru₁₀C₂(CO)₂₄]^2-.^[5]

References

1. ^ Slebodnick, C.; Zhao, J.; Angel, R.; Hanson, B. E.; Song, Y.; Liu, Z.; Hemley, R. J., "High Pressure Study of Ru₃(CO)₁₂ by X-ray Diffraction, Raman, and Infrared Spectroscopy", Inorg Chem., 2004, 43, 5245-52.
2. ^ Bruce, M. I.; Jensen, C. M.; Jones, N. L. “Dodecacarbonyltriruthenium, Ru₃(CO)₁₂” Inorganic Syntheses, 1989, volume 26, pages 259-61. ISBN 0-471-50485-8.
3. ^ Hastings, W. R.; Roussel, M. R.; Baird, M. C. “Mechanism of the conversion of [Ru(CO)₅] into [Ru₃(CO)₁₂]” Journal of the Chemical Society, Dalton Transactions, 1990, pages 203-205. DOI: 10.1039/DT9900000203
4. ^ Bruce, M. I.; Williams, M. L. “Dodecacarbonyl(tretrahydrido)tetraruthenium, Ru₄(μ-H)₄(CO)₁₂” Inorganic Syntheses, 1989, volume 26, pages 262-63. ISBN 0-471-50485-8.
5. ^ Nicholls, J. N.; Vargas, M. D. “Carbido-Carbonyl Ruthenium Cluster Complexes” Inorganic Syntheses, 1989, volume 26, pages 280-85. ISBN 0-471-50485-8ISBN.