This tetrahedral cluster is the most common and most stable "binary" carbonyl of iridium.

[1][2][3] 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.

Each Ir center is octahedral, being bonded to 3 other iridium atoms and three terminal CO ligands.

Ir4(CO)12 has Td symmetry with an average Ir-Ir distances of 2.693 Å.

It is prepared in two steps by reductive carbonylation of hydrated iridium trichloride.