Chapter 4 - Jacobs University

Chapter 5
Organoruthenium POM
interesting and rather unexpected, as this polyanion had in general been considered as a rigid and
(maybe for this reason) unreactive entity. However, the results reported here combined with our
unpublished work (vide supra) show that this is not exactly true. On the contrary, the crownshaped
P 8 W 48 nano object uniquely combines high solution stability over a wide pH range with
intricate reactivity on its inner surface with an unexpected structural flexibility able to adapt
“intelligently” to the shape, size, charge etc. of the electrophile (e.g. d-block metal ion,
lanthanide, organometallic unit). It appears that Müller’s recently suggested analogies between
super-large polyoxomolybdates and biological systems (e.g. cells) can perhaps be extended to
polyoxotungstate chemistry.
5.4.2 Solution NMR
We have also performed 31 P and 13 C solution NMR studies on 3a redissolved in D 2 O, but the
results are somewhat difficult to interpret. For example, in 31 P NMR we see several signals with
different intensities in the expected ppm range (-6.7 to -7.8) (Figure 5.6). This result is probably
due to the disorder of W25 and K6, which can result in different positional isomers with slightly
different NMR spectra. Furthermore, the presence of four potassium ions grafted inside 3
complicates the situation further. In addition, the line broadening somewhat resembles that of our
recently reported [{Ru(C 6 H 6 )(H 2 O)}{Ru(C 6 H 6 )}(g-XW 10 O 36 )] 4- (X = Si, Ge) for which we also
noticed complex NMR behavior, including the possibility of in situ formed paramagnetic Ru 3+
impurities. 14e
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