Cationic zinc clusters with mean formula [formula omitted] in the sodalite cavities of zeolite Y (FAU)

Abstract

Now that the occurrence of monatomic Zn + at extraframework positions in zeolites has been established, a reevaluation of a crystal structure reported in 1992 indicates that cationic zinc clusters of mean formula Zn 5 . 4 6 . 9 + had formed in the sodalite cavities of zeolite Y (FAU), Zn ca.43Si 137Al 55O 384 per unit cell. Their mean Zn–Zn bond length is 3.14(2) Å, and their two mean Zn–Zn–Zn angles are 77.0(4)° and 101.6(4)°. To minimize the number of Zn–Zn intercationic approaches, and to distribute positive charge relatively evenly over the anionic zeolite framework, these clusters are likely to be cyclic (Zn 6) and a segment of a cycle (Zn 5). The even, four-electron clusters cyclo- Zn 6 8 + and Zn 5 6 + are proposed. Each sodalite cavity may host one of these clusters. cyclo- Zn 6 8 + would have three atoms at site I′ and three at site II′, alternating, with symmetry 3 m. Zn 5 6 + would be like cyclo- Zn 6 8 + but with one atom at site I′ missing, and symmetry m.