Tetrairidium dodecacarbonyl

Tetrairidium dodecacarbonyl is the chemical compound with the formula Ir₄(CO)₁₂. This tetrahedral cluster is the most common and most stable "binary" carbonyl of iridium. This air-stable species is only poorly soluble in organic solvents. It has been used to prepare bimetallic clusters and catalysts, e.g. for the water gas shift reaction, and reforming, but these studies are of purely academic interest.

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Structure

Each Ir center is octahedral, being bonded to 3 other iridium atoms and three CO ligands. Ir₄(CO)₁₂ has T_d symmetry. The related clusters Rh₄(CO)₁₂ and Co₄(CO)₁₂ have C_3v symmetry because of the presence of three bridging CO ligands in each.

Preparation

It is prepared in two steps by reductive carbonylation of hydrated iridium trichloride. The first step give [Ir(CO)₂Cl₂]^-.^[1]

IrCl₃ + 3 CO + H₂O → [Ir(CO)₂Cl₂]^- + HCl^- + CO² + H⁺

4 [Ir(CO)₂Cl₂]^- + 6 CO + 2 H₂O → Ir₄(CO)₁₂ + 2 CO₂ + 4 H⁺ + 8 Cl^-

References

1. ^ Pergola, R. D.; Garlaschelli, L.; Matinengo, S. (1990). "Dodecacarbonyltetrairidium: Ir₄(CO)₁₂". Inorganic Syntheses 28: 245-247. doi:10.1002/9780470132593.ch63.

http://www.webelements.com/webelements/compounds/text/Ir/C12Ir4O12-18827811.html
http://arjournals.annualreviews.org/