Synthesis and crystal structure of Ag4I4 nanoclusters in the sodalite cavities of fully K+-exchanged zeolite A

Ag 4 I 4 nanoclusters have been synthesized in half of the sodalite cavities of fully K + -exchanged zeolite A. An additional KI molecule is retained in each large cavity as part of a near square planar K 4 I 3 + cation. A single crystal of Ag 1 2 -A, prepared by the dynamic ion-exchange of Na 1 2 -A (LTA) with aqueous 0.05 M AgNO 3 and washed with CH 3 OH, was placed in a stream of flowing 0.05 M KI in CH 3 OH at 294 K for 2 days. The crystal structure of the product, K 9 Si 1 2 Al 1 2 O 4 8 .(Ag 4 I 4 ) 0 . 5 .K 4 I 3 + , a = 12.290(1) A, was determined by single-crystal X-ray diffraction in the cubic space group Pm3m. It was refined with all measured reflections to the final error index R 1 = 0.077 (based on the 264 reflections for which F o > 4σ(F o )). The thirteen K + ions per unit cell are found at three crystallographically distinct positions: eight K + ions in the large cavity fill the 6-ring site, three K + ions fill the 8-rings, and two K + ions are opposite 4-rings in the large cavity. One iodide ion per unit cell lies opposite a 4-ring in the large cavity, held there by two 8-ring and the two 6-ring K + ions (K 4 I 3 + ). Two Ag + and two I - ions per unit cell are found on 3-fold axes in the sodalite cavity, indicating the formation of Age clusters (interpenetrating tetrahedra; symmetry T d ; diameter ca. 8.0 A) in half of the sodalite units. Each cluster (Ag-I = 2.97(2) A) is held in place by the coordination of its four Ag + ions to the zeolite framework (each Ag + cation is 2.48(1) A from three 6-ring oxygens) and by the coordination of its four I - ions to large-cavity K + ions through 6-rings (I-K = 2.72(6) A).