Cationic zinc clusters with mean formula Zn5.46.9+ in the sodalite cavities of zeolite Y (FAU)

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 Zn5.46.9+ had formed in the sodalite cavities of zeolite Y (FAU), Znca.43Si137Al55O384 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 (Zn6) and a segment of a cycle (Zn5). The even, four-electron clusters cyclo-Zn68+ and Zn56+ are proposed. Each sodalite cavity may host one of these clusters. cyclo-Zn68+ would have three atoms at site I′ and three at site II′, alternating, with symmetry 3m. Zn56+ would be like cyclo-Zn68+ but with one atom at site I′ missing, and symmetry m.