Tetrarhodium 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 betwe ...

Rh₄(CO)₁₂. This dark-red crystalline solid is the smallest binary rhodium carbonyl that can be handled as a solid under ambient conditions. It is used as a catalyst in

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

Structure, synthesis, reactions

According to X-ray crystallography, features a tetrahedral array of four Rh

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with nine terminal CO

ligands In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ...

and three bridging CO ligands. The structure can be expressed as Rh₄(CO)₉(μ-CO)₃. is prepared by treatment of an aqueous solution of rhodium trichloride with activated

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

metal under an atmosphere of CO. :4 RhCl₃(H₂O)₃ + 8 Cu + 22 CO → + 2 CO₂ + 8 Cu(CO)Cl + 4 HCl + 10 H₂O Alternatively, the compound can be prepared by treatment of a

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

ic solution of RhCl₃(H₂O)₃ with CO to afford H hCl₂(CO)₂ followed by carbonylation in the presence of

sodium citrate Sodium citrate may refer to any of the sodium salts of citric acid (though most commonly the third): * Monosodium citrate * Disodium citrate * Trisodium citrate The three forms of salt are collectively known by the E number E331. Applications ...

. The cluster undergoes thermal

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with phosphine ligands, L: :Rh₄(CO)₁₂ + ''n'' L → Rh₄(CO)_12-''n''L_''n'' + ''n'' CO Tetrarhodium dodecacarbonyl quantitatively decomposes in boiling hexane to afford hexadecacarbonylhexarhodium: :

Related metal carbonyls

Because of their relevance to

hydroformylation In organic chemistry, hydroformylation, also known as oxo synthesis or oxo process, is an industrial process for the production of aldehydes () from alkenes (). This chemical reaction entails the net addition of a formyl group () and a hydrogen ...

catalysis, rhodium carbonyls have 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: : + 4 CO → Unlike Co₂(CO)₈ which features bridging carbonyls, 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.

References

General reading

* King, R. B., "Rhodium: Organometallic Chemistry" Encyclopedia of Inorganic Chemistry 1994, 7, 3494. {{Rhodium compounds Organorhodium compounds Carbonyl complexes Chemical compounds containing metal–metal bonds Rhodium(0) compounds