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

Preparation, Crystal Structure, and Thermal Stability of the Cadmium Sulfide Nanoclusters Cd6S44+ and Cd2Na2S4+ in the Sodalite Cavities of Zeolite A (LTA)

The crystal structure and thermal stability of two cadmium sulfide nanoclusters prepared in zeolite A (LTA) have been studied by XPS, TGA, and single-crystal and powder XRD. The crystal structures of Cd2.4Na3.2(Cd6S4)0.4(Cd2Na2S)0.6(H2O)> or =5.8[Si12Al12O48]-LTA (a = 12.2919(7) A, crystal 1 (hydrated)) and /Cd4Na2(Cd2O)(Na2O)/[Si12Al12O48]-LTA (a = 12.2617(4) A, crystal 2 (dehydrated)) were determined by single-crystal methods in the cubic space group Pm3m at 294(1) K. Crystal 1 was prepared by ion exchange of Na12-LTA in an aqueous stream 0.05 M in Cd2+, followed by washing in a stream of water, followed by reaction in an aqueous stream 0.05 M in Na2S. Crystal 2 was made by dehydrating crystal 1 at 623 K and 1 x 10(-6) Torr for 3 days. In crystal 1, Cd6S4(4+) nanoclusters were found in and extending out of about 40% of the sodalite cavities. Central to each Cd6S4(4+) cluster is a Cd4S4 unit (interpenetrating Cd2+ and S2- tetrahedra with near Td symmetry, Cd-S = 2.997(24) A, Cd-S-Cd = 113.8(12) degrees, and S-Cd-S = 58.1(24) degrees). Each of the two remaining Cd2+ ions bonds radially through a 6-ring of the zeolite framework to a sulfide ion of this Cd4S4 unit (Cd-S = 2.90(8) A). In each of the remaining 60% of the sodalite cavities of crystal 1, a planar Cd2Na2S4+ cluster was found (Cd-S/Na-S = 2.35(5)/2.56(14) A and Cd-S-Cd/Na-S-Na = 122(5)/92(7) degrees). Cd6S4(4+) and Cd2Na2S4+ are stable within the zeolite up to about 700 K in air. Upon vacuum dehydration at 623 K, all sulfur was lost (crystal 2). Instead as anions, only two oxide ions remain per sodalite unit. One bridges between two Cd2+ ions (Cd2O2+, Cd-O = 2.28(3) A) and the other between two Na+ ions (Na2O, Na-O = 2.21(10) A).

Crystal Structure of an Ethylene Sorption Complex of Fully Vacuum-Dehydrated Fully Ag+-Exchanged Zeolite X (FAU). Silver Atoms Have Reduced Ethylene To Give CH22- Carbanions at Framework Oxide Vacancies

The crystal structure of an ethylene sorption complex of fully vacuum-dehydrated fully Ag(+)-exchanged zeolite X (FAU), a = 24.865(2) A, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd at 21 degrees C. It is very different from the ethylene complex of Ag(92)-X that had been dehydrated at 400 degrees C in flowing oxygen, as were the two dehydrated structures. The crystal was prepared by ion exchange in a flowing stream of aqueous 0.05 M AgNO(3) for 3 days, followed by dehydration at 400 degrees C and 2 x 10(-6) Torr for 2 days, followed by exposure to 300 Torr of zeolitically dry ethylene gas for 2 h at 21 degrees C. The structure was determined in this atmosphere and was refined using all data to the final error indices (based upon the 534 reflections for which F(o) > 4sigma(F(o))) R(1) = 0.062 and wR(2) = 0.135. In this structure, per unit cell, 14 Ag(+) ions were found at the octahedral site I (Ag-O = 2.611(9) A), and 32 partially reduced Ag(+) ions fill two different site I' positions deep in the sodalite cavities (Ag-O = 2.601(13) and 2.618(12) A). The sodalite cavities host two different cationic silver clusters. In about 47% of sodalite units, eight silver atoms form interpenetrating tetrahedra, Ag(8)(n+) (n = 4 is suggested), with T(d)() symmetry. The other 53% of the sodalite units host cyclo-Ag(4)(m+) (m = 2 is suggested) cations with near S(4) symmetry. These clusters are very similar to those in vacuum-dehydrated Ag(92)-X. Thirty-two Ag(+) ions fill the single 6-rings, 15 at site II' (Ag-O = 2.492(10) A), and 17 at site II (Ag-O = 2.460(9) A). The latter 17 lie in supercages where each forms a lateral pi-complex with an ethylene molecule. In turn, each C(2)H(4) molecule forms two cis electrostatic hydrogen bonds to framework oxygens. The remaining 14 Ag+ ions occupy three different II' sites. Vacuum dehydration had caused substantial decomposition: per unit cell, 30 of the 92 Ag(+) ions were reduced and 15 of the 384 framework oxide ions were oxidized to O2(g), leaving lattice vacancies. The sorption of C(2)H(4) at 21 degrees C reoxidized about 7 of the 30 Ag(0) atoms to Ag(+) and reduced 1.75 ethylene molecules to give CH(2)(2-) groups which refilled 3.5 of these 15 lattice vacancies. The remaining vacancies may have been filled with H(2)C=C(2-) ions. The unit cell formula, which originally contained 384 oxygen atoms, may be |Ag(92)(C2H4)17|[Si(100)Al(92)O(369)(CH2)3.5] or |Ag(92)H(23)(C2H4)17|[Si(100)Al(92)O(369)(CH2)3.5(C2H2)11.5].

Crystal Structures of the NO and N2O4 Sorption Complexes of Fully Dehydrated Fully Cd2+-Exchanged Zeolite X (FAU): Coordination of Neutral NO and N2O4 to Cd2+

The structures of the nitric oxide and dinitrogen tetroxide sorption complexes of dehydrated fully Cd2+-exchanged zeolite X (FAU) have been determined using single-crystal X-ray diffraction in the cubic space group Fdm at 21(1) degrees C. Ion exchange was accomplished by allowing an aqueous stream 0.05 M in Cd2+ to flow past each crystal for 5 days. Each crystal was then dehydrated at 500 degrees C and 2 x 10(-6) Torr for 2 days, followed by exposure to 100 Torr of zeolitically dry NO or NO2/N2O4 gas. The structures were determined in these atmospheres. The unit cell constants at 21(1) degrees C are 24.877(2) A for the dark-yellow NO complex, |Cd46(NO)16|[Si100Al92O384]-FAU, and 24.735(2) A for the black N2O4 complex, |Cd46(N2O4)25.5|[Si100Al92O384]-FAU. The structure of the NO complex was refined to R1 = 0.072 and wR2 = 0.134. In this structure, Cd2+ ions occupy four crystallographic sites. Fifteen Cd2+ ions occupy site I (at the centers of the double 6-rings (D6Rs)), and one occupies site I' (in the sodalite cavity opposite a D6R). The remaining 30 Cd2+ ions occupy two different sites II (near 6-rings in the supercages): 16 coordinate to nitric oxide molecules and 14 do not. Sixteen NO molecules lie in the supercage where each interacts weakly with a Cd2+ ion: Cd-N = 2.57(22) A. The observed N-O bond distance is 1.28(25) A and Cd-N-O is 118(10) degrees. The structure of the N2O4 complex was refined to R1 = 0.084 and wR2 = 0.216. In this structure, Cd2+ ions occupy only three crystallographic sites. The 16 D6Rs per unit cell are filled with 11.5 Cd2+ ions at site I and 9 Cd2+ ions at site I': 11.5 + 9/2 = 16. The remaining 25.5 Cd2+ ions occupy site II where each coordinates at 2.43(8) A to a nitrogen atom of a N2O4 molecule. At the coordinating nitrogen atom, O-N-O is 147(10) degrees and the N-O bond lengths are 1.07(9) and 1.23(10) A. At the second nitrogen atom, O-N-O is 140(10) degrees, and the N-O bond lengths are 1.03(13) and 1.42(12) A. The imprecisely determined N-N bond length, 2.74(17) A, appears to be very much lengthened by coordination to Cd2+. The Cd-N-N angle is 144(10) degrees. This appears to be the first crystallographic report of the coordination of N2O4 to a cation.