Tetrairidium dodecacarbonyl
Encyclopedia
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.
. The related clusters Rh4(CO)12
and Co4(CO)12 have C3v symmetry because of the presence of three bridging CO ligands in each.
. The first step give [Ir(CO)2Cl2]−.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
Ir4(CO)12. This tetrahedral cluster
Cluster (physics)
In physics, the term clusters denotes small, multiatom particles. As a rule of thumb, any particle of somewhere between 3 and 3x107 atoms is considered a cluster. Two-atom particles are sometimes considered clusters as well....
is the most common and most stable "binary" carbonyl
Metal carbonyl
Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. These complexes may be homoleptic, that is containing only CO ligands, such as nickel carbonyl , but more commonly metal carbonyls contain a mix of ligands, such as Re3Cl...
of iridium
Iridium
Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
. 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 gas shift reaction
The water-gas shift reaction is a chemical reaction in which carbon monoxide reacts with water vapor to form carbon dioxide and hydrogen:The water-gas shift reaction is an important industrial reaction. It is often used in conjunction with steam reforming of methane or other hydrocarbons, which is...
, 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 CO ligands. Ir4(CO)12 has Td symmetrySymmetry group
The symmetry group of an object is the group of all isometries under which it is invariant with composition as the operation...
. The related clusters Rh4(CO)12
Tetrarhodium dodecacarbonyl
Tetrarhodium dodecacarbonyl is the chemical compound with the formula Rh412. This dark-red crystalline solid is the smallest stable binary rhodium carbonyl. It is used as a catalyst in organic synthesis.-Structure, synthesis, reactions:...
and Co4(CO)12 have C3v 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 trichlorideIridium(III) chloride
Iridium chloride is the inorganic compound with the formula IrCl3. This material 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 give [Ir(CO)2Cl2]−.
- IrCl3 + 3 CO + H2O → [Ir(CO)2Cl2]− + CO2 + 2 H+ + Cl−
- 4 [Ir(CO)2Cl2]− + 6 CO + 2 H2O → Ir4(CO)12 + 2 CO2 + 4 H+ + 8 Cl−