Chapter 4 - Jacobs University

Chapter 9
Unpublished Results
9.2.2.2 Results and discussion
The polyanion [{Y(B-a -SbW 9 O 33 )} 3 (CH 3 COO) 3 (WO 4 )] 23- (16) (Figure 9.29) is composed of
three units of [a-SbW 9 O 33 ] 9- , three Y 3+ ions and one tetrahedral tungsten. Each unit of [a-
SbW 9 O 33 ] 9-
is connected through yttrium ion. The compound 16a has C 3v symmetry. The
compound 16a was fully characterized in the solid state by single-crystal XRD, TGA-DSC, and
IR as well as in solution by 1 H, 13 C and 89 Y NMR . Each yttrium is bound to two [a-SbW 9 O 33 ] 9-
via Y-O(W) bonds involving a oxygen of each unit of [a-SbW 9 O 33 ] 9- . The inner coordination
sphere of each yttrium center is completed by a acetate ligand, a water molecule (Y-OH 2 =
2.319(6) and 2.329(4) Å; Y-O(W) = 2.296(23), 2.332(26), 2.371(23) and 2.357(23) Å) and a
tetrahedral atom which may be tungsten (Y-O(W) = 2.299(3) and 2.244(4) Å) but in that case the
site is not fully occupied. The identity of this atom is not clear from the X-ray results. The
structural geometry of the yttrium resembles distorted pentagonal bipyramidal; one of the axial
oxygens of an acetate is split into two planes (Figure 9.29). The charge of the compound is
balanced by sodium. Furthermore, for calculation of available crystal water, we performed TGA
measurements on 16 (Figure 9.28) from room temperature to 900 °C which is fully consistent
with the formula of 16 provided above.
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