Cadmium-113, chemical shift determination

Figure 3. Chemical shift ranges of cadmium metalloproteins are compared here with chemical shifts determined for cadmium complexes. The shift ranges for the complexes are for pure ligand type, taken from...

The uppermost horizontal portion of Figure 2 depicts the chemical shift range of cadmium with oxygen ligands, originally determined by Maciel and Borzo (13) and soon thereafter extended by Kostelnik and Bothner-by (14) and Cardin et al. (15). The solution species have been determined by Ohtaki et al. (16a),... 

In principle, the shifts of the individual species in rapid equilibrium may be extracted by the application of known equilibrium constants to the results from solutions covering a range of compositions. This has been done for zinc and cadmium halide systems. Such treatments assume that the shift of an individual species is independent of the concentrations of the other species present. However, results for the nonlabile complexes of group VIII metals suggest that there will be some dependency but it is difficult to estimate the possible magnitude for metals such as cadmium. The accuracy of a determined chemical shift is poor if the species does not have a large concentration in at least one solution measured. Finally, considerable errors may be involved if the NMR measurements are made under different conditions (e.g., higher concentration) from those for which the equilibrium constants were evaluated. 

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