Hexadecacarbonylhexarhodium is a

metal carbonyl cluster In chemistry, a metal carbonyl cluster is a compound that contains two or more metals linked in part by metal-metal bonds and containing carbon monoxide (CO) as the exclusive or predominant ligand. The area is a subfield of metal carbonyl chemistry ...

with the formula Rh₆(CO)₁₆. It exists as purple-brown crystals that are slightly soluble in dichloromethane and chloroform. It is the principal binary carbonyl of rhodium.

Discovery and synthesis

Rh₆(CO)₁₆ was first prepared by Hieber in 1943 by carbonylation of RhCl₃·3H₂O at 80–230 °C and 200 atm carbon monoxide with silver or copper as a halide acceptor. Hieber correctly formulated the compound as a binary carbonyl, but suggested the formula Rh₄(CO)₁₁, i.e., CO/Rh ratio of 2.75. The correct formula and structure was subsequently established by Dahl et al. using X-ray crystallography. The correct CO/Rh ratio is 2.66. Relative to the original preparation, the carbonylation of a mixture of anhydrous

rhodium trichloride Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)''n'', where ''n'' varies from 0 to 3. These are diamagnetic solids featuring octahedral Rh(III) centres. Depending on the value of ''n'', the material is either a den ...

and iron pentacarbonyl was shown to give good yields of Rh₆(CO)₁₆. Other compounds of rhodium are also effective precursors such as CO)₂Rh(μ-Cl)sub>2 and rhodium(II) acetate: :3 Rh₂(O₂CCH₃)₄ + 22 CO + 6 H₂O → Rh₆(CO)₁₆ + 6 CO₂ + 12 CH₃COOH :3 CO)₂RhClsub>2 + 4 CO + 6 Cu → Rh₆(CO)₁₆ + 6 CuCl It also arises quantitatively by thermal decomposition of tetrarhodium dodecacarbonyl in boiling hexane: :

Reactions

At least some of the CO ligands can be displaced by donor ligands. Rh₆(CO)₁₆ catalyzes a number of organic reactions including hydrogenation and hydroformylation.

References

{{Rhodium compounds Carbonyl complexes Organorhodium compounds Chemical compounds containing metal–metal bonds