CRYSTAL-STRUCTURE OF AN ETHYLENE SORPTION COMPLEX OF CD2-EXCHANGED ZEOLITE-X, CD46SI100AL92O384-CENTER-DOT-29.5C(2)H(4)()

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.