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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 7, Number 3
BKCSDE 7(3)
March 20, 1986 

 
Title
Crystal Structurre of Fully Dehydrated Partially Ag+-Exchanged Zeolite 4A, Ag7.6Na4.4-A. Ag+ Ions Prefer 6-Ring Sites. One Ag+ Ion is Reduced
Author
Yang Kim*, Young Wook Han, Karl Seff
Keywords
Abstract
The structure of partially Ag+-exchanged zeolite 4A, Ag7.6Na4.4-A, vacuum dehydrated at 370℃, has been determined by single-crystal x-ray diffraction techniques in the cubic space group, Pm3m (a = 12.311(1)Å) at 24(1)℃. The structure was refined to the final error indices R1 = R2 (weighted) = 0.064 using 266 independent reflections for which I0 > 3σ(I0). Three Na+ ions occupy the 3 8-ring sites, and the remaining ions, 1.4 Na+ and 6.6 Ag+, fill the 8 6-ring sites; each Ag+ ion is nearly in the [111] plane of its 3 O(3) ligands, and each Na+ ion is 0.9Å from its corresponding plane, on the large-cavity side. One reduced silver atom per unit cell was found inside the sodalite unit. It was presumably formed from the reduction of a Ag+ ion by an oxide ion of a residual water molecule or of the zeolite framework. It may be present as a hexasilver cluster in 1/6 of the sodalite units, or, most attractively among several alternatives, as an isolated Ag atom coordinated to 4 Ag ions in each sodalite unit to give (Ag5)4+, symmetry 4mm.
Page
190 - 193
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