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.

Structure and synthesis
The cluster has D3h symmetry, consisting of an equilateral triangle of Ru atoms, each of which bears two axial and two equatorial CO ligands. Os3(CO)12 has the same structure, whereas Fe3(CO)12 is different, with two bridging CO ligands, resulting in C2v symmetry.

Ru3(CO)12 is prepared by heating a methanol solution of ruthenium trichloride under a high pressure of carbon monoxide at 250 °C. The stoichiometry of the reaction is uncertain, one possibility being the following:
 * 6 RuCl3 +  33 CO  &rarr;  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  &rarr;  3 Ru(CO)5  Keq = 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.

Upon warming under a pressure of hydrogen, Ru3(CO)12 converts to the tetrahedral cluster H4Ru4(CO)12. Ru3(CO)12 undergoes substitution reactions with Lewis bases:
 * Ru3(CO)12 +  n L  &rarr;  Ru3(CO)12-nLn  +  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)142- and the bioctahedral cluster [Ru10C2(CO)24]2-.