Crystal structure of Mn 46Si 100Al 92O 384 · 89H 2S, a hydrogen sulfide sorption complex of fully dehydrated Mn 2+-exchanged zeolite X

Abstract

The structure of Mn 46Si 100Al 92O 384 · 89H 2S ( a=24.628(7) Å), a hydrogen sulfide sorption complex of fully dehydrated, fully Mn 2+-exchanged zeolite X, has been determined by single-crystal X-ray diffraction methods in the cubic space group Fd 3 at 21(1) °C. A crystal of Mn 46-X, dehydrated at 380 °C and 2 × 10 −6 Torr for 2 days, was treated with 300 Torr of zeolitically dry H 2S(g) at ambient temperature, and its structure was determined in this atmosphere. The final error indices for the 217 reflections for which I>3 σ( I) are R 1=0.065 and R 2=0.055. In the final refinement, the 645 reflections with I>0 were used. Mn 2+ ions occupy four crystallographic sites, two more than in empty Mn 46-X. Sixteen Mn 2+ ions fill site I, at the centers of the double six-rings (Mn(octahedral)–O=2.285(9) Å). Each of 25 Mn 2+ ions at site II extends 0.49 Å into the supercage and coordinates to three six-ring oxygens and one H 2S molecule deeper in the supercage (Mn–S=2.454(8) Å). Fifty-six H 2S molecules are found at two III ′ sites where each ‘hydrogen bonds’ to two framework oxygens (S–O=3.51(4)/3.50(4) and 3.46(4)/3.52(3) Å). Altogether 81 H 2S molecules are sorbed in the eight supercages per unit cell. Of the eight sodalite cavities, 2.5 have a Mn 2+ ion at site I ′, another at site II ′, and a sulfur atom (likely HS −) bridging between them (Mn–S=2.49(2) and 2.43(3) Å, respectively, with Mn–S–Mn=94.9(9)°). The Mn 2+ ions at site I ′ are recessed deeply, 1.40 Å into their sodalite cavities from their six-rings to maximize an Mn 2+⋯Mn 2+ contact, 2.70(3) Å, through a six-ring. In contrast, the Mn 2+ ions at site II ′ are only 0.43 Å from their planes. The remaining 5.5 sodalite cavities each hold an H 2S molecule or an H 3S + ion that associates only with framework oxygen atoms by ‘hydrogen bonding’ (S–O=3.551(11) Å).