Disproportionation of an Element in a Zeolite. I. Crystal Structure of a Sulfur Sorption Complex of Dehydrated, Fully Cd2+-Exchanged Zeolite X. Synthesis of Tetrahedral S44+ and n-S42+, Two New Polyatomic Cations of Sulfur

The crystal structure of a sulfur sorption complex of fully dehydrated, fully Cd 2+ -exchanged zeolite X, Cd 46 Si 100 Al 92 O 384 ·52S per unit cell ( a = 24.925(7) Å), has been determined by single-crystal X-ray diffraction methods in the cubic space group Fd 3̄ at 21(1) °C. The crystal was prepared by ion exchange in an aqueous stream 0.05 M in Cd 2+, followed by dehydration at 450 °C and 2 × 10 -6 Torr and then exposure in situ to zeolitically dry sulfur vapor. The structure was refined to the final error indices R 1 = 0.051 and R 2 = 0.043 with 362 reflections for which I > 3σ( I ). Forty-six Cd 2+ ions are found at five crystallographic sites: 12 at site I at the centers of the hexagonal prisms (Cd−O = 2.387(8)), 8 at site I‘ in the sodalite cavities near the hexagonal prisms (Cd−O = 2.325(7) Å), 7 at site II‘ in the sodalite cavities (Cd−O = 2.195(8) Å), and the remaining 19 at two different site II positions, near single six-oxygen rings in the supercages, with occupancies of 7 and 12 (Cd−O = 2.155(7) and 2.251(7) Å, respectively). All fifty-two sulfur atoms disproportionated upon sorption to give sulfide anions and two new tetrasulfur cations, S 4 4+ and n -S 4 2+ . Each of 12 sulfide ions coordinates to a site II Cd 2+ ion in the supercage. S 4 4+ is tetrahedral with S−S = 2.17(2) Å, a quantum mechanical calculation gives 2.21 Å, and two of the eight sodalite cavities per unit cell are centered by one. In S 4 4+, each sulfur atom is 3.380(9) Å from three framework oxygens; with those 12 contacts, S 4 4+ is hosted and stabilized by an anionic sodalite cavity. Each supercage holds a zigzag n -S 4 2+ cluster with a torsion angle of 114(8)°. n -S 4 2+ is electron deficient, bridges covalently between two zeolite oxygens, and has a predominantly ionic interaction with a sulfide ion.