Hexadecacarbonylhexarhodium

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 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 iron pentacarbonyl 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 3 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 and hydroformylation.