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KMID : 1059519910350030189
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Journal of the Korean Chemical Society
1991 Volume.35 No. 3 p.189 ~ p.195
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Crystal Structures of Dehydrated Ag+ and Zn2+ Exchanged Zeolite A, Ag2.8Zn4.6-A and of Its Ethylene Sorption Complex
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Jeong Mi-Suk
Park Jong-Yul
Kim Un-Sik
Kim Yang
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Abstract
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Two crystal structures of dehydrated Ag2.8Zn4.6-A and of its ethylene sorption complex have been determined by single-crystal X-ray diffraction techniques. The structures were solved and refined in the cubic space group Pm3m at 23(1)℃. Dehydration of two crystals studied were achieved at 400℃ and 2 × 10-6 Torr for 2 days and one crystal was treated with 250 Torr of ethylene at 25(1)℃. The structures of dehydrated Ag2.8Zn4.6-A (a = 12.137(2) Å and of its ethylene sorption complex (a = 12.106(2)Å) were refined to final error indices, R(weighted) = 0.044 with 237 reflections and R(weighted) = 0.050 with 301 reflections, respectively, for which I > 3σ(I). 2.8 Ag+ ions are recessed 0.922(2) Å from (111) plane of three 6-ring oxygens into the large cavity where each forms a lateral π complex with an ethylene molecule. These Ag+ ions are in 2.240(5)Å from three framework oxide ions and 2.290(5) Å from each carbon atom of an ethylene molecule. The Zn2+ ions occupy two different threefold axis positions of the unit cell. 2.8 Zn2+ ions are recessed 0.408(2) Å from (111) plane of the 6-ring oxygens and each Zn2+ ion forms a π complex with an C2H4 molecule. The distances between Zn2+ ions and carbon atom of ethylene molecule, Zn(2)-C = 2.78(4) Å are long. This indicates that this bond is relatively weak.
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