HYDRIDE AND CARBONYL FLUCTIONALITY IN [HM10C(CO)24]- (M = RU, OS)

The nature of the crystallographically isostructural hydrido-cluster anions [HOs10C(CO)24]- (1) and [HRu10C(CO)24]- (2) in solution has been probed by variable-temperature C-13-NMR and two-dimensional {H-1}C-13-EXSY spectroscopy. The results of the study are interpreted in terms of both localised and global intramolecular exchange of the carbonyl and hydrido ligands which appear to occur by the same mechanisms in both clusters. The significance of the derived model for the understanding of the dynamic behaviour of more complicated systems such as [H4Os10(CO)24]2- (4) is discussed. The latter is at present the best molecular model for the structural aspects of synthesis gas adsorption at high density on metal surfaces.