Chapter 4 - Jacobs University

Chapter 9
Unpublished Results
9.2.4.2 Results and discussion
The polyanion [{Y(CH 3 COO)GeW 11 O 39 } 2 ] 12 - (18) (Figure 9.42) consists of two [a-GeW11 O 39 ] 8-
anion linked by a [{(CH 3 COO)(H 2 O) 2 Y} 2 ] 4+ group in head to head fashion which results in a
dimeric compound with C 2h symmetry. The compound 18a 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, 89 Y and
183 WNMR. The acetate molecules are bound to the Y 3+ ions in rather unexpected fashion. In this
polyanion, each Y 3+ ion has completed 8 coordination numbers by bonding with 8 oxygen atoms.
Out of these eight oxygen atoms four oxygen atoms are connected to the Keggin fragment. Other
three oxygen atoms are part of acetate groups and remaining one coordination bonds is occupied
with water molecule. The bond angle of ÐO-Y-O is 65.19° with the two oxygen atoms from two
different acetate acetate groups and bond angle of ÐO-Y-O is 53.43° with two oxygen atoms
from same acetyl group and the bond distance of 2.42 Å with one acetyl oxygen atoms, 2.46 Å
with two other acetyl oxygen atoms and has on an average 2.27 Å - 2.32 Å bond distance with
oxygen atoms from keggin fragments [a-GeW 11 O 39 ] 8- . Encapsulated Y 3+ atoms are also bonded
with one water molecule with bond distance of 2.39 Å. We performed TGA measurements on
17a (Figure 9.41) from room temperature to 900 °C which is fully consistent with the formula of
17a provided above.
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