Chapter 4 - Jacobs University

Chapter 9
Unpublished Results
9.1.4.2 Results and discussion
The polyanion [Co 4 (H 2 O) 16 P 8 W 48 O 184 ] 32- (9) (Figure 9.11) contains two pairs of cobalt ions
which are incorporated in the cavity but on opposite sides (K-3 and K-7) in figure 9.12.
Additionally two disordered cobalt ions in K-4 and K-5 position are occupied by 15%.
Interestingly, this difference in coordination is accompanied by a distortion of the P 8 W 48
structure and this kind of distortion observed before in other transition metal complexes. The
bond distances between two terminal oxygen of two P 2 W 12 units increase to 3.81 Å from their
usual bond distance 2.93 Å. There are also two extra cobalt ions linked to the outside of the
polyanion in K-4 and K-5 position bridging to neighboring polyanions, form a 2D network. We
also performed TGA measurements on 9a from room temperature to 900 °C in order to confirm
the number of crystal waters (Figure 9.10).
Figure 9.11 Polyhedral/ball and stick type structural representation of 9. Color scheme: K, Co, P and WO 6 units are
shown by orange, pink, blue and red respectively.
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