Crystal Structure of Zeolite LTA Containing Extraframework Tungsten(VI) Ions
journal contributionposted on 22.02.2018, 00:00 by Hyeon Seung Lim, Joon Young Kim, Nam Ho Heo, Karl Seff
Tungsten(VI) has been introduced into zeolite LTA (A) by the reaction of fully dehydrated Tl-A (|Tl12|[Si12Al12O48]-A) with WCl6 (g, 7.0 × 102 Pa) at 453 K for 48 h under anhydrous conditions. The crystal structure of the product, |(WCl)0.6(Tl7Cl6)0.5Tl8.5|[Si12Al12O48]-A, was determined by single-crystal crystallography using synchrotron X-radiation. Its composition was confirmed by energy dispersive X-ray analysis. It was refined in the space group Pm3̅m (a = 12.061(1) Å) using all data to the final error index R1 = 0.085 for the 628 unique reflections for which Fo > 4σ(Fo). WCl6 reacted with Tl+ ions in the zeolite to form WCl5+ and Tl7Cl6+. WCl5+ lies opposite 6-rings in half of the large cavities; its W6+ ion coordinates tetrahedrally to its Cl– ion and to three 6-ring oxygen atoms. The other half of the large cavities contain Tl7Cl6+; one Tl+ ion at the very center of a large cavity coordinates octahedrally to six Cl– ions, each of which bonds in turn to a Tl+ ion in an 8-ring. The remaining Tl+ ions occupy well established cation positions near 6-rings.