Synthesis and Structural Characterization of ... - Jacobs University

Chapter 3
Unpublished Results
We also decided to investigate the solution properties of the diamagnetic derivatives (Lu
and Y analogues) by 183 W and 89 Y NMR spectroscopy. The experiments were carried out on
Na-16, Na-17, Na-19, and Na-20 redissolved in H 2 O/D 2 O. Many attempts were made to
produce solution NMR spectra of the diamagnetic derivatives 16, 17, 19 and 20 (Lu and Y
analogues). The major difficulty was the low solubility of the compounds, since a high
concentration of the polyanion (> 0.1 M) is needed in order to get good signals in the 183 W
NMR spectrum. Attempts to dissolve the compounds by heating eventually lead to partial
decomposition of the polyanions and showed a less number (< 12) for both 16 and 17 (Figure
3.35 (a)), and a large number (> 6) peaks in the 183 W NMR spectra of Na-19 (Figure 3.35 (b)),
probably arising from a mixture of species in the solution. On the other hand, the 89 Y NMR
spectrum for 17 showed a singlet at 19 ppm (Figure 3.36) which could not be assigned
whether for the mono- or di-yttrium derivative of {Sb 2 W 22 }.
We also tried ion exchange using Li + loaded resin, which led eventually to the total
dissolution of the compounds due to the replacement of the countercations with lithium.
However, the 183 W NMR spectra for 16, 17, 19 and 20 were not conclusive and gave a less
number (< 6) peaks. We speculate that the ion exchange method may have stripped the Lu 3+
and Y 3+ from the polyanion framework and thus lead to partial decomposition to various side
products.
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