Yh. Yeom et al., CRYSTAL-STRUCTURE OF AN ETHYLENE SORPTION COMPLEX OF CD2-EXCHANGED ZEOLITE-X, CD46SI100AL92O384-CENTER-DOT-29.5C(2)H(4)(), JOURNAL OF PHYSICAL CHEMISTRY B, 101(12), 1997, pp. 2138-2142
The crystal structure of an ethylene sorption complex of anhydrous ful
ly Cd2(+)-exchanged zeolite X, Cd-46-Si100Al92O384. 29.5C(2)H(4) (a =
24.864(6) Angstrom, has been determined by single-crystal X-ray diffra
ction techniques in the cubic space group Fd(3) over bar at 21(1)degre
es C. A crystal of Cd-46-X was dehydrated at 450 degrees C and 2 x 10(
-6) Torr for 2 days followed by exposure to ca. 150 Torr of dry ethyle
ne gas at 21(1)degrees C. The structure was determined in this atmosph
ere and refined to the final error indices R(1) = 0.046 and R(w) = 0.0
54 with 740 reflections for which I > 3 sigma(I). At site I (at the ce
nters of the double six-rings), 15.5 octahedrally coordinated Cd2+ ion
s are found per unit cell (Cd-O = 2.350(6) Angstrom). Only one Cd2+ io
n (trigonal) is found at site I' (Cd-O = 2.503(6) Angstrom). At site I
I (in the supercage), 29.5 Cd2+ ions are found (Cd-O = 2.221(6) Angstr
om). Each of these site-II Cd2+ ions is recessed 0.50(1) Angstrom into
the supercage from the plane of the three oxygens to which it is boun
d. To complete its distorted tetrahedral coordination, each coordinate
s laterally (symmetrically) to an ethylene molecule (counted as monode
ntate) in the supercage (Cd-C = 2.70(4) Angstrom and C=C = 1.26(5) Ang
strom). No other ethylene molecules are sorbed.