Web Release Date: September 11,
Crystal Structure of a Methylamine Sorption Complex of
Fully Dehydrated Fully Ca2+-Exchanged Zeolite X,
Ca46(CH3NH2)16[Si100Al92O384]-FAU
Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Pusan 609-735, Korea
Department of Chemistry, University of Hawaii, Honolulu, Hawaii 96822
Received May 10, 2004
In Final Form: July 14, 2004
Abstract:
The structure of a methylamine sorption complex of fully dehydrated fully Ca2+-exchanged zeolite X,
Ca46(CH3NH2)16[Si100Al92O384]-FAU, has been determined in the cubic space group Fd
at 21(1) 
C
(a = 24.994(4) Å) by single-crystal X-ray diffraction techniques. The crystal was prepared by ion exchange
in a flowing stream of 0.05 M aqueous Ca(NO3)2 for 3 days, followed by dehydration at 480 C and
2 × 10-6 Torr for 2 days, and exposure to 160 Torr of zeolitically dry methylamine gas at 21(1) C. The
structure was determined in this atmosphere and was refined, using the 739 reflections for which I > 0,
to the final error indices R1 = 0.152 and R2 = 0.061. In this structure, Ca2+ ions occupy three crystallographic
sites. Sixteen Ca2+ ions fill the octahedral site at the centers of hexagonal prisms (Ca-O = 2.429(7) Å).
The remaining 30 Ca2+ ions are found at two nonequivalent sites II (in the supercages) with occupancies
of 14 and 16 ions. Each of these Ca2+ ions coordinates to three framework oxygens, either at 2.296(7) or
2.334(7) Å, respectively. Sixteen methylamine molecules have been sorbed per unit cell, two per supercage.
Each coordinates to one of the latter 16 site-II Ca2+ ions: N-Ca = 2.30(9) Å. The imprecisely determined
N-C bond length, 1.48(23) Å, differs insignificantly from that in methylamine(g), 1.474(5) Å. The positions
of the hydrogen atoms were calculated. One of the amino hydrogen atoms hydrogen bonds to a 6-ring
oxygen, and the other forms a bifurcated hydrogen bond to two other 6-ring oxygens. The methyl group
does not hydrogen bond to anything.
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