Synthesis and Structural Characterization of ... - Jacobs University

Chapter 2
Experimental
gentle stirring. After 15 min., the product was collected by filtration on a sintered glass filter
and air dried. 7
2.3.6 Synthesis of K8[γ‐GeW10O36]·6H2O
15.2 g (4.63 mmol) of K 8 [β 2 -GeW 11 O 39 ]·14H 2 O were dissolved in 150 mL of water. A small
amount of insoluble material was removed by rapid filtration on a fine frit or through Celite.
The pH of the solution was quickly adjusted to 8.7 – 8.9 by addition of 2 M K 2 CO 3 solution.
The pH was kept at this value by addition of the K 2 CO 3 solution for 16 min. The product was
then precipitated by addition of 40 g solid KCl. During the precipitation, the pH was
maintained at 8.8 by addition of small amounts of the K 2 CO 3 solution or diluted HCl as
needed for 10 min. Then, the solid was filtered off and air-dried. 7
2.3.7 Synthesis of K8Na2[A‐‐GeW9O34]·25H2O
To prepare K 8 Na 2 [A--GeW 9 O 34 ]·25H 2 O, at first K 6 Na 2 [-GeW 11 O 39 ]·13H 2 O precusor
should be prepared: A solution of 72.6 g of Na 2 WO 4·2H 2 O in 120 mL of water was added to a
solution of 2.05 g of GeO 2 in 40 mL of 1 M NaOH solution. The mixture was stirred and
heated. After dropwise addition of 80-mL of 4 M HCl to the hot solution under vigorous
stirring, the solution was boiled for about 1 h and cooled to room temperature. A white salt
was precipitated upon addition of 30 g of solid potassium chloride. The salt was recrystallized
from hot water, then filtered off and air-dried. 8a
In order to obtain K 8 Na 2 [A--GeW 9 O 34 ]·25H 2 O, 43.5 g (13.5 mmol) sample of K 6 Na 2 [-
GeW 11 O 39 ]·13H 2 O was dissolved in 400 mL of water with stirring. Then 22.5 g (162.8 mmol)
of K 2 CO 3 was added in small portions to this solution. After stirring for about 30 min.
(pH∼9.5), a white precipitate appeared slowly. After an additional 20 min. of stirring, the
white solid product was collected on a sintered glass frit, washed with saturated KCl solution
(20 mL), and air dried. 8b
45