Hexadecacarbonylhexarhodium is a metal carbonyl cluster with the formula Rh₆(CO)₁₆. It exists as black crystals that are soluble in organic solvents.

Discovery and synthesis

Rh₆(CO)₁₆ was first prepared by Heiber in 1943 by carbonylation of RhCl₃•3H₂O at 80-230 °C and 200 atm carbon monoxide

Carbon monoxide

Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 with silver or copper as a halide acceptor. It was incorrectly formulated as Rh₄(CO)₁₁. Subsequently, the carbonylation of a mixture of anhydrous rhodium trichloride and pentacarbonyliron was shown to give good yields of Rh₆(CO)₁₆. Other compounds of rhodium are also effective precursors such as Rh₂Cl₂(CO)₄ and rhodium(II) acetate:

3 Rh₂(O₂CCH₃)₄ + 22 CO + 6 H₂O → Rh₆(CO)₁₆ + 6 CO₂ + 12 CH₃CO₂H

Rh₂Cl₂(CO)₄ + 4 CO + 6 Cu → Rh₆(CO)₁₆ + 6 CuCl

Reactions and applications

Rh₆(CO)₁₆ catalyzes a number of organic reactions including hydrogenation

Hydrogenation

Hydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...

 and hydroformylation

Hydroformylation

Hydroformylation, also known as oxo synthesis or oxo process, is an important industrial process for the production of aldehydes from alkenes. This chemical reaction entails the addition of a formyl group and a hydrogen atom to a carbon-carbon double bond...

.