Rhodium carbidocarbonyl clusters

A similar effect was observed with mixed iron-rhodium carbidocarbonyl clusters on oxide supports [14]. Trzeciak and Ziotkowski added Fe(CO)5 to Rh(acac)(CO)L (acac = acetylacetonate) [L=PPh3, P(OPh)3, P(N(C4H4)3)] and achieved in the hydroformylation of 1-hexene at a syngas pressure of 10 atm and 80 C an increase of up to 70% in the yield of the aldehyde [15]. The... 

The chemistry of the carbidocarbonyl clusters of cobalt and rhodium (none is known for iridium) is predominantly the work of Italian school of the late Paolo Chini and colleagues. The first rhodium cluster of this type to be reported was [Rh6C(CO)ls]2, 24 (59), isolated as a minor by-product in the synthesis of [Rh7(CO)t6]3- (and originally misformulated as [Rh3(CO)l0]-). The formation of 24 resulted from the reaction of [Rh7(CO)l6]3- with chloroform (the source of the carbon atom), present as an impurity in the reaction solvent, and 24 is now synthesized by this reaction [Eq. (17)]. 

In the case of rhodium, however, it was demonstrated early that in the synthesis of [Rh6C(CO)l5]2 the encapsulated carbon atom originated as chloroform, which had reacted with the rhodium carbonyl anion [Rh7(CO)l6]3- (59). In the cobalt analog, [Co6C(CO)l5]2-, the carbon atom is derived indirectly from carbon tetrachloride [via Co3(CO)9CCl] (60) Both these syntheses are performed under mild conditions, and there are apparently no examples of carbidocarbonyl clusters of cobalt or rhodium prepared directly from the metal carbonyls under pyrolysis conditions. 

---