Tetrarhodium dodecacarbonyl

Tetrarhodium dodecacarbonyl

Names
IUPAC names tri-μ-carbonyl-1:2κ2C;1:3κ2C;2:3κ2C-nonacarbonyl- 1κ2C,2κ2C,3κ2C,4κ3C-[Td-(13)-Δ4-closo]- tetrarhodium(6 Rh—Rh)
Other names rhodium(0) carbonyl; rhodium carbonyl; rhodium dodecacarbonyl
Identifiers
CAS Number	19584-30-6 Y
ECHA InfoCard	100.039.232
Properties
Chemical formula	Rh4(CO)12
Molar mass	747.743 g/mol
Appearance	Red crystals
Solubility	Chlorocarbons, toluene, tetrahydrofuran
Related compounds
Related compounds	Rhodium(III) chloride, Rh6(CO)16, Rh2(CO)4Cl2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Tetrarhodium dodecacarbonyl is the chemical compound with the formula Rh₄(CO)₁₂. This dark-red crystalline solid is the smallest stable binary rhodium carbonyl. It is used as a catalyst in organic synthesis.

The structure of Rh₄(CO)₁₂ is described by a tetrahedral array of four Rh atoms with nine terminal CO ligands and three bridging CO ligands. The structure can be expressed as Rh₄(CO)₉(µ-CO)₃.

It is prepared by treatment of an aqueous solution of rhodium trichloride with activated copper metal under an atmosphere of CO.

Alternatively, the compound can be prepared by treatment of a methanolic solution of RhCl₃(H₂O)₃ with CO to afford H[RhCl₂(CO)₂], followed by carbonylation in the presence of sodium citrate.

The cluster undergoes thermal substitution with phosphorus ligands:

Because of their relevance to hydroformylation catalysis, the metal carbonyls has been systematically studied to a high degree. The instability of Rh₂(CO)₈ has been a source of curiosity. The analogous binary carbonyl of cobalt, Co₂(CO)₈, is well known. Solutions of Rh₄(CO)₁₂ under high pressures of CO convert to the dirhodium compound:

Unlike Co2(CO)8, the main isomer of Rh₂(CO)₈ features only terminal CO ligands. The relative instability of Rh₂(CO)₈ is analogous to the tendency of Ru(CO)₅ to convert to Ru₃(CO)₁₂.