Solid-state NMR studies of interstitial phosphorus atoms in rhodium carbonyl clusters

Pure samples and as-prepared mixtures of Rh9 and Rh10 carbonyl clusters with interstitial P atoms have been studied quantitatively by 31P MAS and 1H-31P CP/MAS NMR. Information on the 31P chemical shift tensor of the Rh9 and Rh10 clusters has been derived from spinning sideband simulations. The chemical shift anisotropy is slightly larger in the Rh10 clusters (340-400 ppm) than in the Rh9 clusters (230-300 ppm), while the asymmetry parameters are similar (eta = 0.1-0.4). The results contribute to the understanding of the relationship between the shielding anisotropy and the structure of the cluster cavity.