| Abstract
| - The crystal structure of a sulfur sorption complex of fully dehydrated, fully Cd2+-exchanged zeolite X, Cd46Si100Al92O384·52S per unit cell (a = 24.925(7) Å), has been determined by single-crystal X-ray diffractionmethods in the cubic space group Fd3̄ at 21(1) °C. The crystal was prepared by ion exchange in an aqueousstream 0.05 M in Cd2+, followed by dehydration at 450 °C and 2 × 10-6 Torr and then exposure in situ tozeolitically dry sulfur vapor. The structure was refined to the final error indices R1 = 0.051 and R2 = 0.043with 362 reflections for which I> 3σ(I). Forty-six Cd2+ ions are found at five crystallographic sites: 12 atsite I at the centers of the hexagonal prisms (Cd−O = 2.387(8)), 8 at site I‘ in the sodalite cavities near thehexagonal prisms (Cd−O = 2.325(7) Å), 7 at site II‘ in the sodalite cavities (Cd−O = 2.195(8) Å), and theremaining 19 at two different site II positions, near single six-oxygen rings in the supercages, with occupanciesof 7 and 12 (Cd−O = 2.155(7) and 2.251(7) Å, respectively). All fifty-two sulfur atoms disproportionatedupon sorption to give sulfide anions and two new tetrasulfur cations, S44+ and n-S42+. Each of 12 sulfide ionscoordinates to a site II Cd2+ ion in the supercage. S44+ is tetrahedral with S−S = 2.17(2) Å, a quantummechanical calculation gives 2.21 Å, and two of the eight sodalite cavities per unit cell are centered by one.In S44+, each sulfur atom is 3.380(9) Å from three framework oxygens; with those 12 contacts, S44+ is hostedand stabilized by an anionic sodalite cavity. Each supercage holds a zigzag n-S42+ cluster with a torsionangle of 114(8)°. n-S42+ is electron deficient, bridges covalently between two zeolite oxygens, and has apredominantly ionic interaction with a sulfide ion.
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