Synthesis and Structural Characterization of ... - Jacobs University

Chapter 3
Published Results
Figure 3.8. IR spectra of the lanthanide-free [W 22 O 72 (OH) 2 ] 14- {W 22 } (blue curve),
paratungstate [H 2 W 12 O 42 ] 10- (green curve) and metatungstate [H 2 W 12 O 40 ] 6- (red curve).
Bond valence sum (BVS) calculations for 1–10 confirmed that all tungsten atoms are in
the +6 oxidation state, and that all lanthanide ions and yttrium are in the +3 oxidation state. 19
The main purpose of our BVS studies on 1–10 was indeed to check all polyanion oxygens for
possible protonation. As stated above, one monoprotonated oxygen was identified in the
asymmetric half-unit, namely the μ 3 -oxo bridge of the {W 3 } fragment connecting the three
tungsten atoms W5, W6 and W7 (see Figure 3.9). This results in two OH groups for the
dimeric form and a total charge of -8 for all polyanions 1–10. As usual, terminal W=O oxygen
BVS values are low (~ 1.5) but this is typical for the distorted W=O geometry and does not
indicate additional protonation.
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