Dodecanuclear Rh-containing clusters

The distorted icosahedral arrangement found for [Rhi2Sb(CO)27] starts to approach a close-packing arrangement. In solution, however, it was not possible to obtain limiting low-temperature spectra and at room temperature the COs and Rhs are fluxional, probably via the well known icosahedral cube-octahedral pathway. 

Other clusters containing twelve rhodium atoms are all based on dicarbide derivatives in which the carbide occupies a Rhg trigonal prismatic site. Fig. 22 shows 

NMR measurements show that either [Rhi2C2(CO)24] or [Rhi2C2(CO)23] is formed on warming [HRh6C(CO)i3] and that there is independent CO migration around the outer and middle metal layers at room temperature.  

Rh]2-dicarbide [Rhi2C2(CO)25] has been described but this is insoluble and no NMR measurements have been described. 

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