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Disproportionation of two elements, sulfur and iodine, upon sorption into fully dehydrated, fully Cd2+-exchanged zeolite X
1577 coordinates, thermal parameters, site occupancies, bond distances, and angles for the two crystals are given in Tables 1 through 4. Table 1. Positional, thermal, and occupancy parameters^ for Cd46-X-52S. atom Si Al 0(1) 0(2) 0(3) 0(4) Cd(l) Cd(2) Cd(3) Cd(4) Cd(5) S(l) S(2) S(3) S(4) S(5) S(6)
Wye. pos. 96(g) 96(g) 96(g) 96(g) 96(g) 96(g) 16(c) 32(e) 32(e) 32(e) 32(e) 32(e) 96(g) 96(g) 96(g) 96(g) 96(g)
Site
I II II IV
r ir
X
-523(1) -548(1) -1098(3) -15(4) -309(3) -661(3) 0 2322(1) 2213(1) 2055(2) 623(2) 1558(13) 2840(29) 4289(34) 3772(47) 4317(54) 3941(40)
y 1237(1) 376(1) 15(4) -14(4) 665(3) 807(3) 0 2322(1) 2213(1) 2055(2) 623(2) 1558(13) 3094(31) 1821(34) 2661(52) 3541(58) 3901(47)
z 348(1) 1223(2) 1049(3) 1461(3) 616(3) 1719(3) 0 2322(1) 2213(1) 2055(2) 623(2) 1558(13) 2338(34) 2533(46) 2619(54) 2499(62) 1699(32)
or'U,,o 133(14) 146(18) 268(48) 286(44) 314(46) 274(50) 90(6) 182(10) 56(14) 141(17) 508(25) 2215(333) 2821(249) 1416(330) 3321(520) 3968(520)^' 1799(497)
^occupancy varied fixed 96 96 96 96 96 96 12 12.3(1) 12 12.7(1) 7 7.3(1) 7 7.2(1) 7.9(1) 8 8 7.9(6) 12 12.7(1) 7.6(7) 8 8 7.6(7) 8 7.6(7) 7.6(7) 8
^Positional and anisotropic thermal parameters are given xlO'*. Numbers in parentheses are the esds in the units of the least significant digit given for the corresponding parameter. ^Ugq is defined as one-third of the trace of the orthogonalized U,j tensor. ''Occupancy factors are given as the number of atoms or ions per unit cell. '^B = STI^U. ^TO achieve convergence, the shift of the isotropic thermal parameter at S(5) was constrained to be that at 8(4).
Figure 1. Stereoview of a sodalite cavity with a tetrahedral sulfur cation, S/^. Each sulfur atom is near three framework oxygens (dashed lines). Altogether each S/^ cluster has 12 such S—O interactions. Ellipsoids of 20% probability are used for all figures.
1578 Table 2. Selected Interatomic Distances (pm) and Angles (deg)^ for Cd46-X-52S.
162.9(9) Si-O(l) 0(l)-Si-0(2) 112.7(5) Si-0(2) 165.5(9) 0(l)-Si-0(3) 107.4(4) 166.3(9) Si-0(3) 0(l)-Si-0(4) 110.6(4) Si-0(4) 160.6(8) 0(2)-Si-0(3) 105.2(4) 0(2)-Si-0(4) 107.0(4) 163.8 mean 0(3)-Si-0(4) Al-O(l) 169.6(8) 113.9(4) Al-0(2) 175.0(9) 0(l)-Al-0(2) 114.0(4) 177.9(9) 105.6(4) Al-0(3) 0(l)-Al-0(3) Al-0(4) 166.2(9) 0(l)-Al-0(4) 113.4(4) 0(2)-Al-0(3) 105.0(4) 172.2 mean 238.7(8) 0(2)-Al-0(4) 103.5(4) Cd(l)-0(3) Cd(2)-0(2) 225.1(7) 0(3)-Al-0(4) 115.3(4) 215.5(7) Si-0(1)-Al Cd(3)-0(2) 132.2(5) Cd(2)-S(2) 232(8) Si-0(2)-Al 136.5(5) 217(2) Si-0(3)-Al S(l)-S(l) 125.6(5) 338.0(9) Si-0(4)-Al S(l)-0(2) 157.3(5) 247(15) S(3)-S(4) 89.1 (3 )/90.9(3)/l 80.(0) 0(3)-Cd(l)-0(3) 260(19) 0(2)-Cd(2)-0(2) 111.2(3) S(4)-S(5) 238(17) 0(2)-Cd(3)-0(2) 119.0(3) S(5)-S(6) 258(8) 0(2)-Cd(4)-0(2) 115.6(3) S(3)-0(l) 300(9) 0(3)-Cd(5)-0(3) 92.2(3) S(6)-0(l) 273(14) S(l)-S(l)-S(l) 60.0(8) S(4)-S(2) 139(6) 0(2)-S(l)-0(2) 66.7(3) S(2)-S(4)-S(3) 103(7) S(l)-S(l)-0(2) 116.6(4)7116.6(11)7175.89(14) S(2)-S(4)-S(5) 116(6) 0(2)-Cd(2)-S(2) 74(2)7111(2)7132(2) S(3)-S(4)-S(5) 102(6) S(4)-S(5)-S(6) 114(8) 1 S(3)-S(4)-S(5)-S(6) * Numbers in parentheses are the estimated standard deviations in the units of the least significant digit given for the corresponding values.
Figure 2. Stereoview of a supercage in Cd46-X-52S. A cationic sulfur cluster, S(3)-S(4)-S(5)-S(6), n-S/^ with a torsion angle of 114(8)°, is shown. Each terminal sulfur of each electron-deficient n-S4^^ cluster has a polar covalent interaction with an 0(1) framework oxygen. Also shown are two Cd^^ ions at Cd(2) (site II), one at Cd(3) (site II), one at Cd(4) (site IF), and two sulfurs at S(2). Each Cd^^ ion at Cd(2) coordinates to three framework oxygens at 0(2) and to a sulfide ion at S(2).
1579 Table 3. Positional, Thermal, and Occupancy Parameters^ for Cd46-X-89.6I. Atom
(Si,Al) 0(1) 0(2) 0(3) 0(4) Cd(l) Cd(2) Cd(3) Cd(4)
Wye. pos. 192(i) 96(h) 96(g) 96(g) 96(g) 16(c) 32(e) 32(e) 32(e) 192(i) 32(e) 192(i) 48(f)
Site
X
y
z or Uiso
I II
ir
r
1(1) 1(2) 1(3) 1(4) ' See captions to Table 1.
-538(1) -1074(2) -27(3) -642(2) 1691(2) 0 2309(1) 2059(6) 668(7) 1885(4) 2956(1) 2919(4) 1957(6)
1224(1) 1074(2) -27(3) -642(2) 1691(2) 0 2309(1) 2059(6) 668(7) 2961(4) 2956(1) 3863(5) 3750
359(1) 0 1472(3) 313(3) 3145(3) 0 2309(1) 2059(6) 668(7) 4820(4) 2956(1) 2492(6) 3750
164(14) 295(42) 238(33) 302(44) 310(45) 152(7) 219(5) 210(66) 806(62) 1983(115) 2151(22) 2588(111) 5393(131)
occupancy varied with varied constraints fixed
14.2(1) 27.1(2) 2.4(2) 4.2(2) 27.3(4) 26.3(3) 25.4(3) 10.8(3)
14.1(1) 26.0(1) 2.0(1) 3.9(1) 26.0(1) 26.0(1) 26.0(1) 13.0(1)
14.0 25.6 2.4 4.0 25.6 25.6 25.6 12.8
Figure 3. Stereoview of a supercage in Cd46-X-89.6I with four Cd^^ ions at Cd(2) and two n-ls' anions. Each n-Is" anion, I(2)-I(3)-I(4)-I(3)-I(2), has symmetry 2 and bridges between two Cd^^ ions at Cd(2) (site II). Each Cd^^ ion at Cd(2) coordinates to three framework oxygens at 0(2) and to a terminal 1(2) ion. Up to 80% (6.4/8) of the supercages have this arrangement.
Figure 4. Stereoview of a supercage in Cd46-X-89.6I with a square cyclo-^^^ ion in each of its four 12-rings. Each bonded pair of atoms of each U^^ cation has a near linear polar covalent (charge transfer) interaction with an 0(1) framework oxygen. Up to 20% of the supercages may have this particular arrangement. Supercages with one n-Is' and two cyclo-U^^ ions are likely to occur also.
1580 Table 4. Selected Interatomic Distances (pm), Angles (deg), and a Torsion Angle^ for Cd46-X-89.6I. 112.3(2) 0(l)-(Si,Al)-0(2) 107.3(3) 0(l).(Si,Al)-0(3) 112.8(2) 0(l)-(Si,Al)-0(4) 107.1(3) 0(2)-(Si,Al)-0(3) 104.4(4) 0(2)-(Si,Al)-0(4) 0(3)-(Si,Ai)-0(4) 111.9(2) 131.4(3) (Si,Al)-0(l)-(Si,Al) 134.9(4) (Si,Al)-0(2)-(Si,Al) 111.9(4) (Si,Al)-0(3)-(Si,Al) 115.4(3) (Si,Al)-0(4)-(Si,Al) 89.3(2)/90.7(2)/l 80.(0) 0(3)-Cd(l)-0(3) 113.5(2) 0(2)-Cd(2)-0(2) 114.9(2) 0(2)-Cd(3)-0(2) 86.93(14) 0(3)-Cd(4)-0(3) 105.10(13) 0(2)-Cd(2)-I(2) 103.3(3) Cd(2)-I(2)-I(3) 96.6(4) I(2)-I(3)-I(4) 114.8(7) I(3)-I(4)-I(3) 159.4(4) 0(1)-I(1)-I(1) 90.0(5) I(l)-I(l)-l(l) 0 I(l)-I(l)-I(l)-I(l) ^Numbers in parentheses are the estimated standard deviations in the units of the least significant digit given for the corresponding value. (Si,Al)-0(l) (Si,Al)-0(2) (Si,Al)-0(3) (Si,Al)-0(4) mean Cd(l)-0(3) Cd(2)-0(2) Cd(3)-0(2) Cd(4)-0(3) Cd(2)-I(2) I(2)-I(3) I(3)-I(4) I(l)-I(l) I(l)-0(1)
164.5(3) 170.7(5) 170.3(6) 163.5(5) 167.3 238.9(5) 221.8(7) 220.0(9) 244.1(8) 278.3(2) 253.4(13) 247.3(14) 275.7(14)7279.6(13) 316.7(10)
RESULTS AND DISCUSSION Per unit cell, either 6.5 Sg or 44.8 I2 were sorbed and had disproportionated. Because of the way the two crystals were prepared, no elemental material was found within either zeolite single crystal. The net reactions upon sorption per unit cell are: 6.5 Sg -> 12 S^- + 2 S/^ + 8 n-S4^^ and 44.8 I2 -^ 12.8 n-Is" + 6.4 cyclo-l4^^ For both reactions, the principle driving force appears to be the formation of an anion that coordinates tightly to a cation that had been severely coordinatively unsaturated. For the two structures reported here, the cations are three-coordinate near trigonal planar Cd^^ ions. The anions are S^" and T (viewing Is" as r-Is^-F) to give, respectively, Cd(tetrahedral)^^-S^' and Cd(tetrahedral)^^-F. The four polyatomic ions new to chemistry from these two reactions are tetrahedral (84)^^ (see Fig. 1), n-S4^^ (an electron deficient species) (see Fig. 2), n-Is" (all bonds shorter than the 267 pm bonds in 12(g)) (see Fig. 3 and Table 4), and square cyclo-l4^^ (see Fig. 4). Both reactions proceeded until the site for one or more products was full. For the sulfur complex, sorption ends when each of the eight supercages per unit cell contains an n-S4^^ anion; there is no room for another equivalent anion (see Fig. 2). For the iodine complex, because each supercage can hold only two nI5" (see the packing in Fig. 3) or four cyclo-14^^ (see the packing in Fig. 4), the eight supercages per unit cell are full when there are 12.8 n-Is" and 6.4 cyclo-l4^^ per unit cell: 12.8/2 + 6.4/4 = 6.4 + 1.6 = 8.0. If the n-Is" anion is alternatively considered to be a n-h^ cation that bonds ionically at each end to an T anion, then all anions resulting from the disproportionation will have been monoatomic (sulfide or iodide), and all cations will have been polyatomic. The polyatomic cations would then all associate multiply either with oxygen anions of the zeolite framework or with monoatomic guest anions coordinated to Cd^^. The I(3)-I(4)-I(3) bond angle, 114.8(7)°, by being very far from linear (Table 4), is indicative of n-Is^. Polyatomic cations are often found stabilized in the anionic cavities and rings of zeolites.
1581 A density functional theory (DFT) calculation using a 6-3IG* basis set and a B3LYP hybrid functional yielded a 220.6 pm bond length for S/^, in good agreement with 217(2) pm, the value determined crystallographically here. 84"^^, P4, and 814"^" are isoelectronic and isostructural. As a test of the calculational method, the corresponding values for the P4 molecule are 221.6 pm as compared to 221 pm (gas phase). It may reasonably be expected that many more polyatomic cations that will be new to chemistry will be synthesized by disproportionation within zeolites.
REFERENCES 1. 2. 3. 4.
Rabo, J.A., Zeolite Chemistry and Catalysis; Am. Chem. 80c: Washington, D.C., 1976. Chao, C.-C; Lunsford, J.H., J. Phys. Chem., 93 (1971) 6794. Rabo, J.A. Private Communication with Ref [2] in mind. 8ong, M.K.; Kim, Y.; 8eff, K., J. Phys. Chem. B, 107 (2003) 3117.
Wye. pos. 96(g) 96(g) 96(g) 96(g) 96(g) 96(g) 16(c) 32(e) 32(e) 32(e) 32(e) 32(e) 96(g) 96(g) 96(g) 96(g) 96(g)
Site
I II II IV
r ir
X
-523(1) -548(1) -1098(3) -15(4) -309(3) -661(3) 0 2322(1) 2213(1) 2055(2) 623(2) 1558(13) 2840(29) 4289(34) 3772(47) 4317(54) 3941(40)
y 1237(1) 376(1) 15(4) -14(4) 665(3) 807(3) 0 2322(1) 2213(1) 2055(2) 623(2) 1558(13) 3094(31) 1821(34) 2661(52) 3541(58) 3901(47)
z 348(1) 1223(2) 1049(3) 1461(3) 616(3) 1719(3) 0 2322(1) 2213(1) 2055(2) 623(2) 1558(13) 2338(34) 2533(46) 2619(54) 2499(62) 1699(32)
or'U,,o 133(14) 146(18) 268(48) 286(44) 314(46) 274(50) 90(6) 182(10) 56(14) 141(17) 508(25) 2215(333) 2821(249) 1416(330) 3321(520) 3968(520)^' 1799(497)
^occupancy varied fixed 96 96 96 96 96 96 12 12.3(1) 12 12.7(1) 7 7.3(1) 7 7.2(1) 7.9(1) 8 8 7.9(6) 12 12.7(1) 7.6(7) 8 8 7.6(7) 8 7.6(7) 7.6(7) 8
^Positional and anisotropic thermal parameters are given xlO'*. Numbers in parentheses are the esds in the units of the least significant digit given for the corresponding parameter. ^Ugq is defined as one-third of the trace of the orthogonalized U,j tensor. ''Occupancy factors are given as the number of atoms or ions per unit cell. '^B = STI^U. ^TO achieve convergence, the shift of the isotropic thermal parameter at S(5) was constrained to be that at 8(4).
Figure 1. Stereoview of a sodalite cavity with a tetrahedral sulfur cation, S/^. Each sulfur atom is near three framework oxygens (dashed lines). Altogether each S/^ cluster has 12 such S—O interactions. Ellipsoids of 20% probability are used for all figures.
1578 Table 2. Selected Interatomic Distances (pm) and Angles (deg)^ for Cd46-X-52S.
162.9(9) Si-O(l) 0(l)-Si-0(2) 112.7(5) Si-0(2) 165.5(9) 0(l)-Si-0(3) 107.4(4) 166.3(9) Si-0(3) 0(l)-Si-0(4) 110.6(4) Si-0(4) 160.6(8) 0(2)-Si-0(3) 105.2(4) 0(2)-Si-0(4) 107.0(4) 163.8 mean 0(3)-Si-0(4) Al-O(l) 169.6(8) 113.9(4) Al-0(2) 175.0(9) 0(l)-Al-0(2) 114.0(4) 177.9(9) 105.6(4) Al-0(3) 0(l)-Al-0(3) Al-0(4) 166.2(9) 0(l)-Al-0(4) 113.4(4) 0(2)-Al-0(3) 105.0(4) 172.2 mean 238.7(8) 0(2)-Al-0(4) 103.5(4) Cd(l)-0(3) Cd(2)-0(2) 225.1(7) 0(3)-Al-0(4) 115.3(4) 215.5(7) Si-0(1)-Al Cd(3)-0(2) 132.2(5) Cd(2)-S(2) 232(8) Si-0(2)-Al 136.5(5) 217(2) Si-0(3)-Al S(l)-S(l) 125.6(5) 338.0(9) Si-0(4)-Al S(l)-0(2) 157.3(5) 247(15) S(3)-S(4) 89.1 (3 )/90.9(3)/l 80.(0) 0(3)-Cd(l)-0(3) 260(19) 0(2)-Cd(2)-0(2) 111.2(3) S(4)-S(5) 238(17) 0(2)-Cd(3)-0(2) 119.0(3) S(5)-S(6) 258(8) 0(2)-Cd(4)-0(2) 115.6(3) S(3)-0(l) 300(9) 0(3)-Cd(5)-0(3) 92.2(3) S(6)-0(l) 273(14) S(l)-S(l)-S(l) 60.0(8) S(4)-S(2) 139(6) 0(2)-S(l)-0(2) 66.7(3) S(2)-S(4)-S(3) 103(7) S(l)-S(l)-0(2) 116.6(4)7116.6(11)7175.89(14) S(2)-S(4)-S(5) 116(6) 0(2)-Cd(2)-S(2) 74(2)7111(2)7132(2) S(3)-S(4)-S(5) 102(6) S(4)-S(5)-S(6) 114(8) 1 S(3)-S(4)-S(5)-S(6) * Numbers in parentheses are the estimated standard deviations in the units of the least significant digit given for the corresponding values.
Figure 2. Stereoview of a supercage in Cd46-X-52S. A cationic sulfur cluster, S(3)-S(4)-S(5)-S(6), n-S/^ with a torsion angle of 114(8)°, is shown. Each terminal sulfur of each electron-deficient n-S4^^ cluster has a polar covalent interaction with an 0(1) framework oxygen. Also shown are two Cd^^ ions at Cd(2) (site II), one at Cd(3) (site II), one at Cd(4) (site IF), and two sulfurs at S(2). Each Cd^^ ion at Cd(2) coordinates to three framework oxygens at 0(2) and to a sulfide ion at S(2).
1579 Table 3. Positional, Thermal, and Occupancy Parameters^ for Cd46-X-89.6I. Atom
(Si,Al) 0(1) 0(2) 0(3) 0(4) Cd(l) Cd(2) Cd(3) Cd(4)
Wye. pos. 192(i) 96(h) 96(g) 96(g) 96(g) 16(c) 32(e) 32(e) 32(e) 192(i) 32(e) 192(i) 48(f)
Site
X
y
z or Uiso
I II
ir
r
1(1) 1(2) 1(3) 1(4) ' See captions to Table 1.
-538(1) -1074(2) -27(3) -642(2) 1691(2) 0 2309(1) 2059(6) 668(7) 1885(4) 2956(1) 2919(4) 1957(6)
1224(1) 1074(2) -27(3) -642(2) 1691(2) 0 2309(1) 2059(6) 668(7) 2961(4) 2956(1) 3863(5) 3750
359(1) 0 1472(3) 313(3) 3145(3) 0 2309(1) 2059(6) 668(7) 4820(4) 2956(1) 2492(6) 3750
164(14) 295(42) 238(33) 302(44) 310(45) 152(7) 219(5) 210(66) 806(62) 1983(115) 2151(22) 2588(111) 5393(131)
occupancy varied with varied constraints fixed
14.2(1) 27.1(2) 2.4(2) 4.2(2) 27.3(4) 26.3(3) 25.4(3) 10.8(3)
14.1(1) 26.0(1) 2.0(1) 3.9(1) 26.0(1) 26.0(1) 26.0(1) 13.0(1)
14.0 25.6 2.4 4.0 25.6 25.6 25.6 12.8
Figure 3. Stereoview of a supercage in Cd46-X-89.6I with four Cd^^ ions at Cd(2) and two n-ls' anions. Each n-Is" anion, I(2)-I(3)-I(4)-I(3)-I(2), has symmetry 2 and bridges between two Cd^^ ions at Cd(2) (site II). Each Cd^^ ion at Cd(2) coordinates to three framework oxygens at 0(2) and to a terminal 1(2) ion. Up to 80% (6.4/8) of the supercages have this arrangement.
Figure 4. Stereoview of a supercage in Cd46-X-89.6I with a square cyclo-^^^ ion in each of its four 12-rings. Each bonded pair of atoms of each U^^ cation has a near linear polar covalent (charge transfer) interaction with an 0(1) framework oxygen. Up to 20% of the supercages may have this particular arrangement. Supercages with one n-Is' and two cyclo-U^^ ions are likely to occur also.
1580 Table 4. Selected Interatomic Distances (pm), Angles (deg), and a Torsion Angle^ for Cd46-X-89.6I. 112.3(2) 0(l)-(Si,Al)-0(2) 107.3(3) 0(l).(Si,Al)-0(3) 112.8(2) 0(l)-(Si,Al)-0(4) 107.1(3) 0(2)-(Si,Al)-0(3) 104.4(4) 0(2)-(Si,Al)-0(4) 0(3)-(Si,Ai)-0(4) 111.9(2) 131.4(3) (Si,Al)-0(l)-(Si,Al) 134.9(4) (Si,Al)-0(2)-(Si,Al) 111.9(4) (Si,Al)-0(3)-(Si,Al) 115.4(3) (Si,Al)-0(4)-(Si,Al) 89.3(2)/90.7(2)/l 80.(0) 0(3)-Cd(l)-0(3) 113.5(2) 0(2)-Cd(2)-0(2) 114.9(2) 0(2)-Cd(3)-0(2) 86.93(14) 0(3)-Cd(4)-0(3) 105.10(13) 0(2)-Cd(2)-I(2) 103.3(3) Cd(2)-I(2)-I(3) 96.6(4) I(2)-I(3)-I(4) 114.8(7) I(3)-I(4)-I(3) 159.4(4) 0(1)-I(1)-I(1) 90.0(5) I(l)-I(l)-l(l) 0 I(l)-I(l)-I(l)-I(l) ^Numbers in parentheses are the estimated standard deviations in the units of the least significant digit given for the corresponding value. (Si,Al)-0(l) (Si,Al)-0(2) (Si,Al)-0(3) (Si,Al)-0(4) mean Cd(l)-0(3) Cd(2)-0(2) Cd(3)-0(2) Cd(4)-0(3) Cd(2)-I(2) I(2)-I(3) I(3)-I(4) I(l)-I(l) I(l)-0(1)
164.5(3) 170.7(5) 170.3(6) 163.5(5) 167.3 238.9(5) 221.8(7) 220.0(9) 244.1(8) 278.3(2) 253.4(13) 247.3(14) 275.7(14)7279.6(13) 316.7(10)
RESULTS AND DISCUSSION Per unit cell, either 6.5 Sg or 44.8 I2 were sorbed and had disproportionated. Because of the way the two crystals were prepared, no elemental material was found within either zeolite single crystal. The net reactions upon sorption per unit cell are: 6.5 Sg -> 12 S^- + 2 S/^ + 8 n-S4^^ and 44.8 I2 -^ 12.8 n-Is" + 6.4 cyclo-l4^^ For both reactions, the principle driving force appears to be the formation of an anion that coordinates tightly to a cation that had been severely coordinatively unsaturated. For the two structures reported here, the cations are three-coordinate near trigonal planar Cd^^ ions. The anions are S^" and T (viewing Is" as r-Is^-F) to give, respectively, Cd(tetrahedral)^^-S^' and Cd(tetrahedral)^^-F. The four polyatomic ions new to chemistry from these two reactions are tetrahedral (84)^^ (see Fig. 1), n-S4^^ (an electron deficient species) (see Fig. 2), n-Is" (all bonds shorter than the 267 pm bonds in 12(g)) (see Fig. 3 and Table 4), and square cyclo-l4^^ (see Fig. 4). Both reactions proceeded until the site for one or more products was full. For the sulfur complex, sorption ends when each of the eight supercages per unit cell contains an n-S4^^ anion; there is no room for another equivalent anion (see Fig. 2). For the iodine complex, because each supercage can hold only two nI5" (see the packing in Fig. 3) or four cyclo-14^^ (see the packing in Fig. 4), the eight supercages per unit cell are full when there are 12.8 n-Is" and 6.4 cyclo-l4^^ per unit cell: 12.8/2 + 6.4/4 = 6.4 + 1.6 = 8.0. If the n-Is" anion is alternatively considered to be a n-h^ cation that bonds ionically at each end to an T anion, then all anions resulting from the disproportionation will have been monoatomic (sulfide or iodide), and all cations will have been polyatomic. The polyatomic cations would then all associate multiply either with oxygen anions of the zeolite framework or with monoatomic guest anions coordinated to Cd^^. The I(3)-I(4)-I(3) bond angle, 114.8(7)°, by being very far from linear (Table 4), is indicative of n-Is^. Polyatomic cations are often found stabilized in the anionic cavities and rings of zeolites.
1581 A density functional theory (DFT) calculation using a 6-3IG* basis set and a B3LYP hybrid functional yielded a 220.6 pm bond length for S/^, in good agreement with 217(2) pm, the value determined crystallographically here. 84"^^, P4, and 814"^" are isoelectronic and isostructural. As a test of the calculational method, the corresponding values for the P4 molecule are 221.6 pm as compared to 221 pm (gas phase). It may reasonably be expected that many more polyatomic cations that will be new to chemistry will be synthesized by disproportionation within zeolites.
REFERENCES 1. 2. 3. 4.
Rabo, J.A., Zeolite Chemistry and Catalysis; Am. Chem. 80c: Washington, D.C., 1976. Chao, C.-C; Lunsford, J.H., J. Phys. Chem., 93 (1971) 6794. Rabo, J.A. Private Communication with Ref [2] in mind. 8ong, M.K.; Kim, Y.; 8eff, K., J. Phys. Chem. B, 107 (2003) 3117.