THE CRYSTAL-STRUCTURE OF A SULFUR SORPTION COMPLEX OF THE DEHYDRATED PARTIALLY CO2-EXCHANGED ZEOLITE-A()

The crystal structure of a sulfur sorption complex of the dehydrated p artially Co2+ exchanged zeolite A (a=12.058(2) Angstrom) has been dete rmined by single-crystal X-ray techniques. The crystal structure was s olved and refined in cubic space group Pm (3) over bar m at 21(1) degr ees C. Ion Exchange with aqueous 0.05 M Co(NO3)(2) was done by the sta tic method. The crystal of Na4Co4-A was dehydrated at 380 degrees C an d 2X10(-6) Torr for 2 days, followed by exposure to about 100 Torr of sulfur at 330 degrees C for 72 h Full matrix least-squares refinement converged to R(1)=0.084 and R(w)=0.074 with 102 reflections for which 1>3 sigma Q. Crystallographic analysis shows that 2.8 Co2+ ions and 4 Na+ ions per unit cell occupy 6-ring sites on the threefold axes. 1.2 Co2+ ions occupy the 8-ring sites on fourfold axes. 2.8 Co2+ ions at C o(1) are recessed 0.66 Angstrom into the large cavity and 4 Na+ ion at Na(1) are recessed 0.77 Angstrom into the sodalite cavity from the (1 11) plane of O(3)'s. Approximately 16 sulfur atoms were sorbed per uni t cell. Two S-8 rings, each in a butterfly form, are found in the larg e cavity. The bond length between S and its adjacent S is 2.27(3) Angs trom. The distance between 6-ring Co2+ ion and its adjacent sulfur is 2.53 (2) Angstrom and that between 8-ring Co2+ ions and its adjacent s ulfur is 2.72(9) Angstrom. The angles of S-S'-S and S'-S-S' in octasul fur rings are 119.0(2)degrees and 113.0(2)degrees, respectively.