Effective core potential DFT calculations of nuclear shielding as a tool for the prediction and assignment of the tungsten chemical shift in mono- and polynuclear complexes

The shielding of the 183W nucleus in mononuclear tungsten complexes and in the Keggin heteropolyoxotungstate PW12O403− has been investigated by a density functional theory (DFT) method with effective core potentials. Calculated shieldings correlate with experimental data, although they are one order of magnitude lower than the experimental values, which is reflected in low slopes (<0.1) of the correlation lines. The influence of molecular geometry (semi-empirical vs. DFT) on the nuclear shielding is examined. There is a fair correlation between atomic charges at W and nuclear shielding only for species sharing the same formal oxidation state.