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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 15, Number 11
BKCSDE 15(11)
November 20, 1994 

 
Title
The Crystal Structure of Dehydrated Fully Ag+-Exchanged Zeolite A Successively Treated with Ethylene and Bromine Vapor
Author
Mi Suk Jeong, Se Bok Jang, Yang Kim*
Keywords
Abstract
The crystal structure of an ethylene sorption complex of dehydrated Ag12-A reacted with bromine vapor has determined by single-crystal X-ray diffraction techniques in the cubic space group of Pm3m at 22(l)℃ (a=12.180(2) Å). The crystal was prepared by dehydration of Ag12-A at 400 ℃ and 2 X lO-6 Torr for 2 days, followed by exposure to 200 Torr of ethylene gas at 24(l) ℃ for 1 hr. After the ethylene gas was evacuated for 1 hr, the crystal was exposed to 180 Torr of bromine vapor at 24(l) ℃ for 1.5 h. The structure was refined to the final error indices, R1=0.066 and R2 (weighted)=O.055, using 137 independent reflections for which I>3σI. About 55% of the sodalite unit contain two 6-ring Ag+ ions and the remaining 45% contain Ag6 molecules complexed to 2 Ag+ ions at 6-ring sites to give (Ag+)2(Ag6). Upon sorption of ethylene, 4.75 ethylene molecules were sorbed per unit cell and of these, only 1.25 ethylene molecules were brominated by treatment of dibromine because of the limitation of the available space for the reaction products in the large cavity. In the large cavity, each of 3.5 Ag+ ions forms a lateral π complex with an ethylene molecule. About 2.5 8-ring Ag+ ions per unit cell interact with 1.25 1,2-dibromoethane and each of ca. 1.25 6-ring Ag+ ions also interacts with one of bromine atoms of 1,2-dibromoethane. Each bromine atom approaches a carbon atom with C-Br(l)=2.07(20) Å and C-Br(2)=2.07(10) Å, respectively.
Page
940 - 944
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