Crystal Structure of Fully Ag+-Exchanged Zeolite A
The Journal of Physical Chemistry, Vol. 82, No. 8, 1978 921
studied, one with T-' dependence and the other T-*: (b) W. D. Horrocks, Jr., and C. Wong, J. Am. Chem. Soc., 98, 7157 (1976); (c) J. F. Desreux and C. N. Reilley, ibid., 98, 2105 (1976). (29) W. E. Stewart and T. H. Siddall, 111, Chem. Rev., 70, 517 (1970). (30) J. K. M. Sanders, S. W. Hanson, and D. H. Williams, J . Am. Chem. Soc., 94,5325 (1972). (31) I. Armitage et ai., Can. J . Chem., 50, 2119 (1972). (32) B. L. Shaplro and M. D. Johnston, Jr., J. Am. Chem. Soc., 94,8185
(37) J. F. Desreaux, L. E. Fox, and C. N. Reiiley, Anal. Chem., 44,2217 (1972). (38) M. Rabinovitz and A. Pines, J. Chem. SOC.6 , 110 (1968). (39) J. Granot and D. Fiat, J. Magn. Reson., 19, 372 (1975). (40) W. D. Perry and R. S. Drago, J. Am. Chem. Soc., 93,2183 (1971), and references therein.
(41) R. E. Cramer, R. Dubois, and K. Seff, J . Am. Chem. Soc., 96,4125 (1974). (42) R. E. Cramer and R. C. Harris, Inorg. Chem., 13, 2208 (1974). (43) R. A. Bernheim, T. H. Brown, H. S. Gutowsky, and D. E. Woessner, J . Chem. Phys., 30, 950 (1959). (44) E. W. Stout and H. S. Gutowsky, J. Magn. Reson., 24,389 (1976). (45) A. L. Van Geet, Anal. Chem., 40,2227 (1968). (46) The program PROKL was written by S. Sykora. A listing can be found in B. W. Richardson, Ph.D. Thesis, University of Illinois, Urbana, 1972.
(1972). (33) J. Reuben, J . Am. Chem. Soc., 95, 3535 (1973). (34) C. S.Springer, Jr., et al. In ref l(d); A. H. Bruder, S. R. Tanny, H. A. Rockefeller, and C. S. Springer, Jr., Inorg. Chem., 12,187 (1973). (35) M. D. Johnston, Jr., et al., J . Am. Chem. Soc., 97,542 (1975). (36) R. Porter, T. J. Marks, and D. F. Schriver, J. Am. Chem. Soc., 95, 3548 (1973).
The Crystal Structure of Dehydrated Fully Agt-Exchanged Zeolite A Reduced by Hydrogen and Reoxidized by Oxygen, Both at 330 OC. The Loss of Long Range Order and Its Subsequent Return Yang Kim and Karl Seff * Chemistry Department, University of Hawaii, Honolulu, Hawaii 96822 (Received October 7, 1977) Publication costs assisted by the National Science Foundation
The crystal structure of fully Ag+-exchangedzeolite A, reduced by H2and then reoxidized by 02, both at 330 "C, has been determined from three-dimensional x-ray diffraction data gathered by counter methods. The structure was solved and refined in the cubic space group Pm3m; a = 12.3045(11) A at 24(1) "C. The crystal was prepared by partial dehydration at 250 "C and 8 X lo4 Torr for 16 h; oxygenation (100 Torr of 0 2 ) at 400 "C for 0.3 h; evacuation,decomposition, and complete dehydration at Torr and 400 "C for 1 h; hydrogenation (12 Torr of H,) at 330 "C for 0.5 h; and reoxygenation (100 Torr of 0,) at 330 "C for 1 h. The silver ions were reduced, at least partly, by the hydrogen treatment as evidenced by the uptake of hydrogen and the observation of powder diffraction lines from silver metal; and the zeolite was damaged as evidenced by the complete loss of its crystalline diffraction pattern. Perhaps one A1-0 bond at each A13+ion was broken by the H+ ions which were generated, to give Si-OH hydroxyl groups and three-coordinate A13+. Upon treatment with oxygen, the crystal was repaired as evidenced by the return of its single crystal diffraction pattern, and silver was reoxidized as evidenced by the loss of the silver powder diffraction lines, to the limit of eleven Ag+ ions per unit cell. The resulting structure shows eight equivalent Ag+ ions on threefold axes very near the planes of the 6-oxygen rings, and three equivalent Ag+ ions in the planes of the 8-oxygen rings but not at their centers. About 0.56 silver atoms are found at the neutral silver atom position, where they are expected to have formed Age clusters in about 9% of the sodalite units. The remaining 0.44 atoms per unit cell have remained outside the brown-black crystal, probably as the oxide. Altogether, one silver atom per unit cell did not return to the ionic state within the zeolite because a suitable coordination site is not available. Full-matrix least-squares refinement converged to a weighted R2 index (on F) of 0.058 using the 204 independent reflections for which I, > 3u(10).
Introduction Dispersions of silver ions and atoms are effective as catalysts. For example, catalysts containing both Ago and Ag+ are important in partial oxidation processes such as the formation of ethylene oxide from ethylene and 0xygen.l As another example, partially decomposed fully Ag+-exchanged zeolite A,' containing clusters of Ag, coordinated to eight Ag+ ions in a fraction of its sodalite units, was exposed to oxygen and then to ammonia; the ammonia was partially oxidized to form the saturated hydronitrogens, triazane (N3H5)and cyclotriazane (N3H3),3in high yield. As a third example, Ag+-exchanged zeolite Y can cleave water into hydrogen and oxygen4 by a photochemically induced reduction of Ag+, followed by the oxidative thermal desorption of hydrogen. Some metal ions in zeolites are known to be easily reduced by hydrogen gas. For example, the dipositive cations of the relatively volatile elements, Hg, Cd, and Zn, can be 0022-3654/78/2082-0921$01 .OO/O
removed as atoms from zeolite X by heating in h y d r ~ g e n . ~ Ni(II),, Cu(II),' Pd(II),8 and Pt(IIIQin zeolite Y can also be reduced to the metallic state by hydrogen. The reduced platinum atoms cluster in a cubic closest-packed manner,1° isostructural with bulk platinum metal, within the zeolite cavities. Ferrous ions in the zeolites X, Y, and A can be reduced to the atoms by sodium vapor.'l Mossbauer spectroscopy of the reduced sample showed that, although some large iron clusters 20-500 A had formed external to the zeolite, most of the reduced iron remained within the zeolite in the form of clusters with an "extremely narrow particle size distribution and diameters less than 13 A".ll The ions of the more noble elements can be reduced by oxide ions of residual water molecules or of the zeolite framework. Cu(I1) ions in CuNa-Y are reduced to Cu(1) by heating above 400 "C, and the reverse reaction occurs upon cooling in oxygen.12 Silver ions in fully Ag+-ex0 1978 American Chemical Society
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Y. Kim and K. Ssff
The Journal of Physical Chemistry, Vol. 82, No. 8, 1978
TABLE I: Positional, Thermal,a and Occupancy Parameters occuWyckoff
Dosition (Si,Al) 24( k )
pancy no.
z P 12 P 13 P 23 P11 P 22 P33 3720(4) 0 0 24(8) 1' 23(5) 25(6) 1/2 78( 23) -1( 14)d 0 0 0 1 O(1) 12(h) O(2) 12(i) 2933(12) 28( 17) 39( 12) 0 0 29(35) 1 O(3) 24(m) 3423(11) 37(8) ll(14) 1 34( 13) 6(23) l l ( 1 4 ) Ag( 1) 8(g) 1942( 2) 91(5) 1 68(2) 68(2) 91(5) 91(5) 6(e) 173 2( 4 ) 79(35) -8(40)d 0 0 0 0.09(1) Ad31 12(i) 4258(8) 333( 33) 0 0 -119(27) 0.25 W9) a Positional and anisotropic parameters are given X lo4. Numbers in parentheses are the estimated standard deviations in the units of the least significant figure given for the corresponding parameter. The anisotropic temperature factor is exp[-(pl,h2 t p,k2 t p,Z2 + P12hkt PI3hZt PZ3kZ)]. Rms displacements can be calculated from pii values using the formula, pi = O,225u(~ji)'",where u = 12.3045. Occupancy for (Si) = 1/2, occupancy for (Al) = 1/2. This physically unacceptable value was increased by l o in the preparation of Figure 1. x
Y
0 0 0 1103(8) 1942( 2) 0 0
1829(7) 2201(18) 2933(12) 1103(8) 1942( 2) 0 4258(8)
changed zeolite A are reduced to Ago upon heating above 400 oC.2 About 4 of the 12 Ag+ ions per unit cell are reduced upon heating at 425 "C and lom5 Torr for 10 days; Torr for upon more strenuous treatment, 475 "C and 7 days, approximately 10 of the 12 Ag+ ions are reduced. It was noted by B e ~ e that, r ~ ~although treatment of Agl,-A with hydrogen at 330 "C resulted in the complete loss of the crystalline diffraction pattern of the zeolite, subsequent oxygenation at 330 "C restored it. The crystal structure of dehydrated fully Ag+-exchanged zeolite A, reduced by H2 and reoxidized by 02,was determined to examine the structural aspects of this intrazeolitic redox process. Experimental Section A single crystal 0.08 mm on an edge was lodged in a fine glass capillary. AgN03 (0.05 M) was allowed to flow past the crystal at about 1 cm/s for 3 days; since the exchange of Ag+ for Na+ has been shown to be facile and complete after milder treatment,13 complete exchange was assured in this case. The clear, colorless, hydrated Ag+-exchanged crystal was dehydrated for 16 h at 250 "C and 8 X lo4 Torr. It was then treated with 100 Torr of oxygen at 400 "C for 20 min to oxidize any silver that might have been reduced (this oxidation is shown by this work to be necessarily incomplete), and then evacuated for 1 h to complete the deh~drati0n.l~ After cooling to 25 O C , the crystal was observed to be black or perhaps dark brown in color. The addition of 12 Torr of H2 did not affect the color of the crystal. The temperature was increased to 330 "C,and maintained there for 30 min, after which the remaining H2 gas was evacuated for 1 h at 330 "C. Then 100 Torr of O2 gas was added, maintained at 330 "C for 1 h, followed by evacuation for 15 min. The crystal was allowed to cool to 25 "C and was sealed off in its capillary. Its color remained black or dark brown. Two other crystals were also exchanged by the flow method, and dehydrated at 350 "C for 2 days. One crystal was treated with 100 Torr of H2 gas at 25 "C for 6 days. The second crystal was exposed to 400 Torr of H2 at 150 "C for 2 h. Both crystals were at least partially destroyed; neither retained a crystalline diffraction pattern. The cubic space group Pm3m (no systematic absences) was used throughout this work for reasons discussed previously.15J6 Diffraction data were collected on a four-circle computer-controlled diffractometer, equipped with a pulse-height analyzer and a graphite monochromator, using Mo K a radiation (Ka,, X 0.709 30 A, Kaz, h 0.713 59 A). The unit cell constant, as determined by a least-squares refinement of 15 intense reflections for which 20" < 28 < 24", is 12.3045(11) A at 24 "C. Data collection was done by methods described previo u ~ l yexcept , ~ ~ that only one unique region of reciprocal
space was examined at a scan rate ( w ) of 4" min-l in 28. Standard deviations were assigned to individual reflections according to the formula
a ( I ) = [w2(CT
+ B1 t B,) + (p1)2]'/2
where w is the scan rate, CT is the total integrated count,
B1and B, are the background counts, and the intensity I = w(CT - B1- B2). A value of 0.0218was assigned to the empirical parameter p to account for the empirically observed reduced reliability of the more intense reflections. The intensities were corrected for Lorentz and polarization effects;l0the contribution of the monochromator crystal was calculated assuming it to be half-perfect and halfmosaic in character. An absorption correction was judged to be negligible and was not app1ied.l' All 888 reflections for which 28 < 70" were examined by counter methods. Of these, only the 204 for which I > 3a(n were used for structure solution and refinement. Structure Determination Full-matrix least-squares refinement was initiated using the atomic parameters of the framework atoms ((Si,Al), 0(1), 0(2), and O(3)) and of the silver positions from the structure of partidy decomposed vacuum-dehydratedfully Ag+-exchangedzeolite A.2 Anisotropic refinement of the framework atoms and isotropic refinement of the silver positions (Ag(1) and Ag(3) of Table I) converged to the error indices
R1 = Li IF, - IFcII/EFo= 0.146 and
R2 = ( Z w ( F , - IFc1)2/~~Fo2)1/2 = 0.133
A subsequent difference Fourier synthesis revealed three peaks (1.1-3.0 e A-3 in height, esd = 0.16 e A-3) at (0.0, 0.0, 0.16), (0.25, 0.5, 0.5))and (0.406, 0.5, 0.5). Only the first was stable in least-squares refinement. Simultaneous positional, occupancy, and anisotropic thermal parameter refinement converged to R1 = 0.070 and Rz = 0.053. The occupancies at Ag(1) and Ag(2) (see Table I) refined to 7.8(1) and 3.3(1) ions per unit cell; these values were reset and fixed at 8 and 3, the maximum number of ions at these sites. Anisotropic refinement with the occupancy parameter of Ag(2) varying, converged with the final error indices, R1 = 0.070 and Rz = 0.058. The goodness-of-fit, (Bw(F, - lFc1)2/(m- s ) ) ~ / is ~ ,2.05; m (204) is the number of observations, and s (32) is the number of variables in least squares. All shifts in the final cycles of refinement were less than 0.1% of their corresponding esd's. The largest peak on the final difference Fourier function, whose estimated standard deviation is 0.14 e A-3, was 2.8 e A-3 in height and was located just at Ag(1).
The Journal of Physical Chemistty, Vol. 82, No. 8, 1978 923
Crystal Structure of Fully Ag+-Exchanged Zeolite A
Y
V
Figure 1. A stereoview of the large cavity containing 8 Ag' ions at Ag( 1) and 3 Ag+ ions at Ag(3). The Ag(2) position (the Ag, cluster) is not shown in this figure. Ellipsoids of 2 0 % probability are used.
TABLE 11: Selected Interatomic Distances ( A ) and Angles (deg)a 109.2(9) 1.640(8) O(1)-(Si,Al)-O( 2) 111.1(8) 1.668(10) O(1)-(Si,Al)-O( 3) 108.0(7) 1.665(10) O(2)-(Si,Al)-O( 3) 109.2(10) 2.33(1) O(3)-(Si,Al)-O( 3) 2.95(1) (Si,Al)-O( 1 )-(Si,Al) 1 4 7 4 16) (Si,Al)-O( 2)-(Si,Al) 160.9(11) 2.83(4) (Si,Al)-O( 3)-(Si,Al) 145.7(10) 2.69( 2) 119.7(7 ) 2.30( 2) 0(3)-Ag( 1)-0(3) 57.3(6) 3.39(1) 0(3)-Ag( 2)-0(3) 89.7( 1 1 ) 3.01( 6) Ag(l)-Ag(2)-Ag(l) 129.7(5) o(1 3)-0(1) 64.8( 5 ) O(1 )-Ad 3)-0( 2) a The numbers in parentheses are the estimated standard deviations in the units of the least significant digit given for the corresponding parameter.
)-w
TABLE 111: Deviation ( A ) of Atoms from the (111) Plane at O( 3)a 0.16 O(2) 0.13 1) -2.76 21 a A negative deviation indicates that the atom lies on the same side of the plane as the origin.
The final structural parameters are presented in Table
I. Interatomic distances and angles are given in Table 11. A listing of observed and calculated structure factors is available; see the paragraph at the end of this paper regarding supplementary material. A likely atomic arrangement in a particular unit cell is shown in Figure 1. The quantity minimized in least squares is (Zw(F,, lFc1)2)and the weights (w)were the reciprocal squares of a(F,), the standard deviation of each observed structure factor. Atomic scattering factors20721 for 0- and (Si,Al)1.75+ (the average of Sio, Si4+,AlO,and AP+) and of Ag+,21were used. All scattering factors were modified to account for the real components (Af') of the anomalous dispersion correction.22
Discussion In the structure of dehydrated fully Ag+-exchanged zeolite A, reduced by Hz and then reoxidized by 02,eight Agt ions at Ag(1) lie on threefold axes of the unit cell, each ~ ~ vunit ~~ nearly at the center of one of the eight 6 - r i n g ~ per cell (see Figure 1). Each of these ions approaches three oxide ions of the zeolite framework at a distance of 2.33(1) A. On the surface of each sodalite unit, and consistent with its high symmetry, Oh,these eight Ag+ ions lie at the corners of a cube, 4.78 A on an edge (see Figure 1). Three Ag+ ions at Ag(3) lie in the planes of the 8rings,l6vZ3 but off their centers. Each of these is 2.30(2) A from the nearest framework oxide ion at O(2) and 2.69(2)
A from two oxide ions at O(1). This coordination environment is relatively unsatisfactory for the ion at Ag(3), partly because its three ligand atoms are all to one side, not arranged around it. Considering the sum of the Ag+ and 02-radii, 2.58 A,24the bonds between the Ag+ ions at Ag(1) and Ag(3) and oxide ions of the zeolite framework are quite short, and therefore quite covalent. The silver position at Ag(2) is the same as that found for silver atoms in the structures of dehydrated and perhaps partially decomposed fully Ag+-exchangedzeolite A.2 Also the same are the Ag(2)-Ag(2) and Ag(l)-Ag(2) bond lengths, and the magnitudes of the anisotropic thermal parameters of the Ag(2) position. In the structures of dehydrated (and perhaps partially decomposed) fully Ag+-exchangedzeolite A, the 6-ring Ag+ ions had not been reduced, while the 8-ring Agt ions were reduced progressively by heating for 4-10 days at 395-450 0C;25the resulting silver atoms formed Ag, molecules at the centers of the sodalite units where each could be stabilized by coordination to eight Ag+ ions at Ag(1). Hexasilver was present in up to two-thirds of the sodalite units, the remainder being empty of silver species. The Ag(2) occupancy in the present structure, about 0.56 atoms per unit cell, indicates that about 9% of the sodalite units contain hexasilver molecules. This cluster is closest-packed, and is like a piece of the structure of silver metal. Two dehydrated crystals of Ag12-A treated with 100 Torr of hydrogen at 24 "C for 6 days and 400 Torr of hydrogen at 150 "C for 2 h, respectively, gave no crystalline diffraction pattern; only powder lines from small crystals of silver metal could be observed. This indicates that at least some of the Ag+ ions in zeolite A were reduced according to the reaction 2 A g t H,
-+
2Ag0 t 2H+
The resulting silver atoms migrated out of the zeolite to form silver metal. These results are consistent with the observation that about 70% of the Ag' ions are reduced by hydrogen treatment at 150 "C, and 92% at 330 0C.34 More specifically, the 70% value is in general agreement with the reduction of 9 of the 12 Ag+ ions per unit cell, leaving the cyclic (Ag+J (H20), species14intact within the sodalite unit. The 92% value indicates that 11 of the 12 Ag+ ions were reduced at 330 "C. However, there appears to be no structural basis for this limit. The reduction may, in fact, be complete, having been affected initially by oxide ions of residual water molecules.26 The reoxygenated crystal yielded a sizeable single-crystal data set which indicated that this crystal, whose aluminosilicate framework had been damaged and which had lost silver initially, had repaired itself and had resorbed silver during the final oxygen treatment. The resulting
924
The Journal of Physical Chemistry, Vol. 82, No. 8, 1978
black-brown crystal contained 11Ag+ ions and about 0.56 Ago atoms per unit cell. The color of the crystal indicates that it is coated with silver oxide, to account for the remaining 0.44 silver atoms per unit cell. It is concluded that zeolite repair occurs only to a limited extent, only as long as suitable lattice sites are available for the newly oxidized Ag+ ions. After 11Ag+ ions have filled all of the 6-ring and 8-ring sites, the next available site, which would be near zero c o ~ r d i n a t eopposite ~ ~ * ~ ~a 4-ring,14or possibly zero c o ~ r d i n a t eis, ~not ~ ~filled, ~ even though silver atoms as hexasilver, oxygen gas, and H+ ions (vide infra) coexist at 330 “C. The same endpoint, to give 11monovalent ions per unit cell, was approached from the opposite side in another zeolite A structure, Ag6.5T15.5-A, which was prepared by complete aqueous exchange with Ag+ and T1+followed by evacuation at 440 “C for 6 days.32 The structure of the chlorine complex26of dehydrated Aglz-A showed that oxide ions of residual water molecules reduced Ag+ ions to silver atoms, at least for two Ago atoms per unit cell, leaving H+ ions in the structure. In the title structure, for similar reasons, eleven Ag+ ions and one H+ ion are likely to be present per unit cell. Additional water produced by the net reaction of Hz with O2 in the two “sorption” steps has apparently been successfully removed from the zeolite at 330 “C because three Ag+ ions bridged by three water molecules in the sodalite unit14are not seen in this structure. Presumably that (Ag+),(H,O), complex would have formed in the sodalite unit at 330 “C if 12 Ag+ ions were present per unit cell. The complete repair process which has occurred upon oxygen treatment is unusual in crystallography. Its occurrence is even more remarkable because the dehydrated zeolite is likely to be thermodynamically unstable. Zeolite A decomposes at 800 “C to give products, one of which is the SiOz phase ~ - c r i s t ~ b a l i t e . ~ ~ * ~ ~ ~ The ease with which long-range order is restored suggests that a simple reversible reaction has occurred at localized but not ordered sites within the zeolite lattice. It appears that the H+ ions which are generated by the reduction have attacked the zeolite framework, possibly to break Si-0 or A1-0 bonds. A likely reaction would be
which would have occurred in a disordered manner at approximately one of the four A1-0 bonds about each AP+ ion. Three-coordinate AI3+ ions and Si-OH hydroxyl groups would result. By this reaction, repeating units of the framework structure could be set somewhat askew and long-range order would be lost. If it is the O(1) oxide ions which react preferentially, as they have in previous s t r u ~ t u r e s , it2 ~would ~ ~ ~ be intact sodalite units which would be set askew. Acknowledgment. This work was supported by the National Science Foundation (Grant No. CHE76-81586).
Y. Kim and K. Seff
We are also indebted to the University of Hawaii Computing Center. We thank Hermann K. Beyer of the Central Research Institute of Chemistry, Hungarian Academy of Sciences, Budapest 11, Pusztaszeri, Hungary, for sharing some of his results with us prior to their publication. Supplementary Material Available: Listings of the observed and calculated structure factors, Supplementary Table I (2 pages). Ordering information is available on any current masthead page. References and Notes P. A. Kllty and W. M. H. Sachtler, Cat. Rev., 10(1), 1 (1974). Y. Kim and K. Seff, J . Am. Chem. Soc.,99, 7055 (1977). Y. Kim, J. Gilje, and K. Seff, J . Am. Chem. Soc., 99, 7057 (1977). P. A. Jacobs, J. B. Uytterhoeven, and H. K. Beyer, J. Chem. Soc., Chem. Commun., 128 (1977). (5) D. J. C. Yates, J . Phys. Chem., 69, 1676 (1965). (6) J. A. Rabo, C. L. Angeil, D. H. Kasai, and V. Schomaker, Discuss. Faraday Soc., 41, 328 (1966). (7) C. M. Naccache and Y. Ben Taarit, J . Catal., 22, 171 (1971). (8) P. Gallezot and B. Imellk, Adv. Chem. Ser., No. 121, 66 (1973). (93 P. Gallezot, A. Aiacon-Diaz, J-A. Dalmon, A. J. Renouprez, and B. Imelik, J . Cafal., 39,334 (1975). (10) P. A. Gallezot and M. Boudart, private communication. (11) F. Schmidt, W. Gunsser, and J. Adolpf, ACS Symp. Ser., No. 40, 291-301 (1977). (12) L. J. Vandamme, P. A. Jacobs, and J. B. Uytterhoeven, International Conference on Molecular Sieve Zeolites 4th, Chicago, 1977. (13) (a) D. W. Breck, W. G. Eversoie, R. M. Milton, T. B. Reed, and T. L. Thomas, J. Am. Chem. Sm., 78, 5963 (1956); (b) H. S. Sherry, J . Phys. Chem., 71, 1457 (1967); (c) M. Nitta, K. Aomura, and S. Matsumoto, J . Catal., 35, 317 (1974). (14) Y. Kim and K. Seff, J . Phys. Chem., In press (AgIP-A, hydrated). (15) K. Seff, J . Phys. Chem., 76, 2601 (1972). (16) R. Y. Yanagida, A. A. Amaro, and K. Seff, J. Phys. Chem., 77, 805 (1973). (17) Y. Kim and K. Seff, J . Am. Chem. Soc., 100, 175 (1978). (18) S. W. Peterson and H. A. Levy, Acta Crysta//ogr.,10, 70 (1957). (19) Principal computer programs used in this study: T. Ottersen, LP-76 data reductlon program, University of Hawail, 1976; full-matrix least-squares, P. K. Gantzei, R. A. Sparks, and K. N. Trueblood, UCLA LS4, Amerlcan Crystallographic Association Program Library (old) No. 317 (revised 1976); Fourier program, C. R. Hubbard, C. 0. Quicksall, and R. A. Jacobson, Ames Laboratory Fast Fourier, Iowa State University, 1971; C. K. Johnson, ORTEP, Report No. ORNL-3794, Oak Ridge National Laboratory, Oak Ridge, Tenn., 1965. (20) P. A. Doyle and P. S. Turner, Acta Crysfallogr., Sect. A , 24, 390 (1968). (21) “Internatbnai Tables for X-ray Ciystallography”, Vol. IV, Kynoch Press, Birmingham, England, 1974, pp 73-87. (22) “International Tables for X-ray Ciystallography”, Vol. IV, Kynoch Press, Birmingham, England, 1974, pp 149-150. (23) A discusslon of zeolite nomenclature is available: (a) L. Broussard and D. P. Shoemaker, J . Am. Chem. Soc., 82, 1041 (1960); (b) K. Seff, Acc. Chem. Res., 9, 121 (1976). (24) “Handbook of Chemistry and Physics”, The Chemical Rubber Company, Cleveland, Ohio, 1974, p F-198. (25) Y. Kim and K. Seff, J. Am. Chem. Soc., submitted for publicatlon. (Ag12-A, partially decomposed to give Ag,.) (26) Y. Kim and K. Seff, J. Am. Chem. Soc.,in press (chlorine complex). (27) R. L. Firor and K. Seff, J . Am. Chem. Soc.,99, 4039 (1977). (28) V. Subramanian and K. Seff, J . Phys. Chem., 81, 2249 (1977). (29) P. C. W. Leung, K. B. Kunz, I.E. Maxwell, and K. Seff,J. phys. Chem., 79, 2157 (1975). (30) R. L. Firor and K. Seff, J . Am. Chem. Soc., 98, 5031 (1976). (31) R. L. Firor and K. Seff, J . Am. Chem. Soc., 99, 1112 (1977). (32) Y. Kim and K. Seff, J . Phys. Chem., in press. (Age.5Tls,5-A). (33) D. W. Breck, “Zeolite Molecular Sieves”, Wiley, New Yo&, N.Y., 1973, p 494. (34) H. K. Beyer, private communication. (1) (2) (3) (4)
