CRYSTAL-STRUCTURES OF VACUUM DEHYDRATED FULLY CD-2+-EXCHANGED ZEOLITE-A AND ITS ETHYLENE SORPTION COMPLEX

The crystal structure of dehydrated fully Cd2+-exchanged zeolite A evacuated at 2 x 10(-6) Torr and 450-degrees-C (a = 12.225(2) angstrom) and of its ethylene sorption complex (a = 12.219(2) angstrom) have been determined by single crystal X-ray diffraction techniques in the cubic space group Pm3m at 21(1)degrees-C. The structures were refined to final error indices, R1 = 0.063 and R2 = 0.065 with 266 reflections and R1 = 0.055 and R2 = 0.062 with 260 reflections, respectively, for which I > 3-sigma(I). In both structures, six Cd2+ ions lie at two distinguished three-fold axes of unit cell. Dehydrated Cd6-A sorbs 4 ethylene molecules per unit cell at 25-degrees-C (vapor pressure of ethylene is ca. 100 Torr). Each Cd2+ ion forms a lateral pi complex with an ethylene molecule. Four Cd2+ ions exist in a nearly tetrahedral environment, 2.210(7) angstrom apart from three framework oxygen ions (considering ethylene molecule as a monodentate ligand) and 2.67(6) angstrom from each carbon atom of ethylene molecule.