Tetradecanuclear Rh-containing clusters

Detailed multinuclear ( H, Rh) NMR studies have been conducted on 

At room temperature, all the COs are fluxional in both clusters. Thus, H migration within the intact Rhi4 cluster occurs with a lower Ea than complete CO migration on the outside of the cluster they therefore occur independently of each other. This should be contrasted with [H3Rhi3(CO)24] which seems to have very similar values of Ea. for both interstitial H migration and CO migration.  

It should also be noted that both the Rhn- and Rhi4-metal frameworks remain intact whereas less well-packed polyhedral metal skeletons containing a main group interstitial atom (see Sections 3.3.6 and 3.3.7) are fluxional. 

A closely related cluster [Rhi4(CO)26] has been structurally characterized but, apart from a VT NMR study which suggested CO fluxionality, no well-defined NMR studies have been reported. 

The structure of the cluster [Rhi4C2(CO)33] , which results from addition of [Rh(CO)2(MeCN)2]+ to [Rh6C(CO)i5] , is interesting (Fig. 26). IR measurements suggest the involvement of Rh7/Rhg intermediates but no NMR data on this sequence of reactions has yet been reported. 

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