Tetrairidium dodecacarbonyl is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

Ir₄(CO)₁₂. This tetrahedral

cluster may refer to: Science and technology Astronomy * Cluster (spacecraft), constellation of four European Space Agency spacecraft * Asteroid cluster, a small asteroid family * Cluster II (spacecraft), a European Space Agency mission to study t ...

is the most common and most stable "binary"

carbonyl In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a ...

iridium Iridium is a chemical element with the symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal (after osmium) with a density of ...

. 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 Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a s ...

, and reforming, but these studies are of purely academic interest.

Structure

Each Ir center is octahedral, being bonded to 3 other iridium atoms and three terminal CO ligands. Ir₄(CO)₁₂ has T_d

symmetry Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...

with an average Ir-Ir distances of 2.693 Å. 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 Iridium(III) chloride is the inorganic compound with the formula IrCl3. The anhydrous compound is relatively rare, but the related hydrate is useful for preparing other iridium compounds. The anhydrous salt is a dark green crystalline solid. ...

. The first step gives r(CO)₂Cl₂sup>−. :IrCl₃ + 3 CO + H₂O → r(CO)₂Cl₂sup>− + CO₂ + 2 H⁺ + Cl⁻ :4 r(CO)₂Cl₂sup>− + 6 CO + 2 H₂O → Ir₄(CO)₁₂ + 2 CO₂ + 4 H⁺ + 8 Cl⁻

References

{{Iridium compounds Carbonyl complexes Organoiridium compounds