Using the Thallous Ion Exchange Method to

Article pubs.acs.org/JPCC

Using the Thallous Ion Exchange Method to Exchange Tin into High Alumina Zeolites. 1. Crystal Structure of |Sn2+5.3Sn4+0.8Cl−1.8|[Si12Al12O48]‑LTA Jean Marie Vianney Nsanzimana,† Cheol Woong Kim,† Nam Ho Heo,*,† and Karl Seff‡ †

Laboratory of Structural Chemistry, Department of Applied Chemistry, College of Engineering, Kyungpook National University, Daegu 702-701, Korea ‡ Department of Chemistry, University of Hawaii, 2545 The Mall, Honolulu, Hawaii 96822, United States S Supporting Information *

ABSTRACT: Sn2+ and Sn4+ ions have replaced all of the Tl+ ions in the zeolite Tl12-A (|Tl12|[Si12Al12O48]-LTA) by thallous ion exchange (TIE), a vapor phase ion exchange method: SnCl2(g) was allowed to react with Tl12-A under anhydrous conditions at 723 K for 48 h. The tin content of the product, |Sn2+5.3Sn4+0.8Cl−1.8|[Si12Al12O48]-LTA, is 32.6 wt %, much higher than previously reported for any zeolite. Its structure was determined by single-crystal crystallography at 294 K using synchrotron X-radiation (Pm3̅m, a = 12.075(1) Å, R1 = 0.069, R2 = 0.224), and its composition was confirmed by scanning electron microscopy energy-dispersive X-ray analysis. Sn2+ is found at four crystallographic positions, Sn4+ at two, and Cl− at two. Among the 5.3 Sn2+ ions per unit cell, 2.7 (3coordinate) lie opposite 6-rings in large cavities, 0.3 (4-coordinate) are opposite 6-rings in sodalite cavities, 1.5 are in 8-rings, and 0.7 approach a framework oxygen atom and two chloride ions in a trigonal planar manner. Among the 0.8 Sn4+ ions per unit cell (all 3-coordinate, from the disproportionation of Sn2+), 0.7 are opposite the intersection of a 4-, a 6-, and an 8-ring in large cavity, and 0.1 are in 6-rings. Most of the Cl− ions bridge between Sn2+ ions in the large cavity to form Sn3Cl24+. The rest, at the center of the sodalite cavity, bridge linearly between two Sn2+ ions to form Sn2Cl3+.

1. INTRODUCTION Zeolites are widely used in petrochemical and biomass processing.1,2 The regular pore structure and adjustable acidity of zeolites make them highly active catalysts for a large variety of reactions.3 It is usually the extraframework species,4 notably the cations,5 that are responsible for their sorption and catalytic properties. 1.1. Tin Containing Zeolites. Zeolites with extraframework tin cations are efficient catalysts in some organo- and biocatalytic reactions such as the synthesis of α-amino nitrile and the isomerization of sugars.6,7 They are also ion conductors, in particular for protons.8 These properties must be a consequence of the characteristic physicochemical properties of the zeolites and the unique chemistry of tin.9 Sn,H-beta zeolites with 1.4% and 2.4% tin by weight, introduced by conventional liquid phase ion exchange (LPIE) using aqueous SnCl2, were found to be extremely efficient catalysts for the synthesis of α-amino nitriles from various ketones and aldehydes (Strecker reactions10).6 When the reaction was done using just an H-beta catalyst, the yield was low and the reaction time long.6 Sn2+ synergistically accelerated the Strecker reactions for all substrates tested, especially ketones.6 The isomerization of sugars is important in the food industry. The conversion of glucose into fructose for the production of © 2015 American Chemical Society

high-fructose corn syrup (HFCS) has become the largest immobilized biocatalytic process in the world.11 It has recently been shown by Ricardo et al. that framework and “extraframework SnO2 particles” in the high silica zeolite beta react differently with glucose.7 The framework tin sites isomerize glucose to fructose by a Lewis acid mediated intramolecular hydride shift. The “SnO2 particles”, however, do this by a basecatalyzed proton transfer mechanism.7 Sn-exchanged zeolites have been extensively studied for their ionic conductivity.12 They were prepared by a series of steps beginning with SnCl2·2H2O and H-zeolites such as Hferrierite,8 H-mordenite,12 and H-Y.13 In all cases the proton conductivity increased after tin exchange. It was shown by Knudsen et al. that the framework structure of a ferrierite [Al4.12Si31.88O72]4.12− and a silicate [AlxSi96−xO192]x− (S-115) were not affected by this exchange.8 Sn-exchanged mordenites prepared using SnCl2·2H2O at elevated temperatures have the highest conductivity.12 X-ray powder diffraction work showed that the tin ions occupied several sites in its channels.12 The starting material was hydrogen mordenite (|H7.5Na0.5K0.05(H2O)28|[Al8Si40O96]-MOR); the products were Received: December 17, 2014 Revised: January 15, 2015 Published: January 16, 2015 3244

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The Journal of Physical Chemistry C |H 2 . 7 Na 0 . 5 K 0 . 0 5 Sn 2 . 4 (H 2 O) 2 7 . 5 |[Al 8 Si 4 0 O 9 6 ]−MOR and |Na0.5K0.05Sn3.9(SnO2)0.4(H2O)24.38|[Al8Si40O96]-MOR.12 Again the framework was not affected. Upon heating in oxygen (the last step in the preparation of Sn-exchanged mordenite), the excess SnCl2 was oxidized to SnO2 and SnCl4(g) (2SnCl2 + O2(g) → SnO2 + SnCl4(g)).8 By conventional LPIE, very little tin exchanged into H-beta (Si/Al = 12).6 Although the replacement of all H+ ions by tin cations was reported in the case of mordenite (Si/Al = 5.0),12 this was not true for zeolite Y (Si/Al = 3.0) and ferrierite (Si/Al = 7.7).13 This could be a consequence of the extensive hydrolysis of Sn2+ ions in aqueous solution,14 even at pHs as low as 1 or 2.14−16 At very low pH values, H+ concentrations are high enough to compete with Sn2+ in ion exchange. An attempt was made to prepare aqueous 0.1 M SnCl2. Its pH was 1.9 and the “solution” was white, indicating that extensive hydrolysis had occurred and that Sn(OH)2 was precipitating. This was also true for a 0.05 M SnCl2 solution whose pH was 2.0. At these pHs, a high alumina zeolite would suffer severe damage or be destroyed. This is probably why only high silica zeolites were used in the above studies.6,12,13 High alumina zeolites have higher ion exchange capacities, and zeolites with higher Sn2+ contents may be better catalysts and ion conductors. Vapor phase ion exchange (VPIE) is a promising method for the ion exchange of Sn2+ cations into high alumina zeolites. Unlike LPIE, VPIE does not require that the zeolite be acid stable.17−20 Also, because the process is anhydrous, the hydrolysis of Sn2+ to give H+ ions that could exchange into the zeolite and OH− ions that could coordinate to Sn2+ within the zeolite is entirely avoided. Thallous ion exchange (TIE),21 a kind of VPIE reaction, has the additional advantage that the zeolite may be the only solid product of the reaction; the other product of this metathesis reaction, a thallous halide, would have sublimed away. Quite generally, quantitative ion-exchange could be one of the most important advantages of VPIE and TIE. Although there are many important applications of Snexchanged zeolites, no detailed study of their structures has been reported. Clusters of average stoichiometry Sn4S64+ were found in zeolite Y by powder X-ray diffraction.22 1.2. Objectives and Methodology. The objectives of this work are (1) to achieve a high degree of Sn2+ exchange into a high alumina zeolite, and (2) to find the Sn2+ positions and see their coordination environments. Sn2+ would be introduced into zeolite LTA by the TIE method.21 Because the vapor pressure of SnCl 2(g) is appreciable, 5.3 kPa, at a temperature at which the zeolite is stable, 723 K,23 it was hoped that full Sn2+ exchange could be accomplished. In this work, zeolite LTA would first be fully exchanged with Tl+ by LPIE. After complete dehydration TIE could proceed as follows per unit cell: Tl12‐A + 6SnCl 2(g ) → Sn6‐A + 12TlCl(g )

2. EXPERIMENTAL SECTION 2.1. Crystal Preparation. Large colorless single crystals of zeolite 4A (|Na12(H2O)x|[Si12Al12O48]-LTA, or Na12-A·xH2O, Na 12 -A, or Na-A) were synthesized by Charnell and Kokotailo.24 One of these (see Table 1) was lodged in a fine Table 1. Experimental and Crystallographic Data crystal cross-section (mm) Tl+ ion exchange (T (K), t (h), V (mL)) dehydration of Tl-A (T (K), t (h), P (Pa)) reaction of Tl-A with SnCl2 (T (K), t (h), P (kPa)) SEM-EDX beam energy, current (E (keV), I (μA)) X-ray source wavelength (Å) detector crystal-to-detector distance (mm) data collection temperature (T (K)) space group, No. unit cell constant, a (Å) maximum 2θ for data collection (deg) no. of reflections measured no. of unique reflections measured, m no. of reflections with Fo > 4σ(Fo) no. of variables, s data/parameter ratio, m/s weighting parameters: a, b final error indices: R1b, R2c goodness of fitd

0.08 294, 48, 10 673, 48, 1 × 10−4 723, 48, 5.3 20, 1 × 10−3 PF(BL-5A)a 0.8000 ADSC Quantum-315r 60 294(1) Pm3̅m, 221 12.075(1) 72.29 1014 593 546 54 11.0 0.1422, 1.9850 0.069, 0.224 1.18

Beamline BL-5A at the Photon Factory, Japan. bR1 = Σ|Fo − |Fc||/ ΣFo; R1 is calculated using only those reflections for which Fo > 4σ(Fo). cR2 = [Σw(Fo2 − Fc2)2/Σw(Fo2)2]1/2 is calculated using all unique reflections measured. dGoodness of fit = (Σw(Fo2 − Fc2)2/(m − s))1/2. a

Pyrex capillary. Hydrated |Tl12|[Si12Al12O48]-A (colorless) was prepared by the flow (dynamic) ion-exchange of Na-A with aqueous 0.1 M TlC2H3O2 (Puratrem, 99.999%; Cd, Cu, Mg, Pb, and Zn < 1 ppm). This and similar procedures had previously been successful.25−27 About 14 mg of slightly offwhite anhydrous SnCl2 (Sigma-Aldrich, ≥ 99.99%; Co 4.0 ppm, Pb 3.2 ppm, Li 3.0 ppm, Cs 2.3 ppm, Ce 1.4 ppm, Cd 1.0 ppm, Na 0.4 ppm) was placed in a small Pyrex test tube which was then put into the reaction vessel (a large Pyrex tube) above the capillary (a continuation of the capillary) containing the Tl12-A crystal. The crystal and the SnCl2 were then dehydrated (Table 1). As the temperature increased (25 K/h) toward 673 K, the SnCl2 all sublimed and condensed higher up on the inner surface of Pyrex tube (above the heater); it was now entirely white. Finally, after being allowed to cool to room temperature (−25 K/h), the reaction vessel containing the dry SnCl2 above the crystal-containing capillary was sealed off under a vacuum from the vacuum line. The isolated reaction vessel was maintained at 723 K for 48 h for the TIE reaction (Reaction 1). Afterward only the portion of the reaction vessel that contained the crystal was heated at 723 K for another 48 h to distill away any excess SnCl2 and TlCl that might be in or near the crystal. After being allowed to cool (−40 K/h) to room temperature, the resulting black crystal was sealed off under vacuum in its capillary by torch. Similar VPIE procedures had been utilized successfully to prepare indium-containing zeolite Y.20

(1)

The positions of the extraframework tin ions within the zeolite would be determined crystallographically, together with their coordination environments and oxidation states. The tin ions would be readily identifiable crystallographically because their ionic radii and scattering powers are very different from those of the preceding Tl+ ions. 3245

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The Journal of Physical Chemistry C

Figure 1. EDX spectrum (counts vs photon energy in keV) of |Sn6.1Cl1.8|[Si12Al12O48]-LTA. Note that the three largest Tl peaks (Tl Lα1 at 10.267 keV, Tl Lβ1 at 12.212 keV, and Tl Lβ2 at 12.269 keV) are absent.

2.2. X-ray Diffraction. Diffraction intensities were measured with synchrotron X-radiation via a silicon(111) double crystal monochromator. The ADSC Q315 ADX program28,29 was used for data collection which was done by the omega scan method. Highly redundant data sets were harvested by collecting 72 sets of frames with a 5° scan and an exposure time of 1 s per frame. The basic data files were prepared using the program HKL2000.28,29 The reflections were indexed by the automated indexing routine of the DENZO program.28 These were corrected for Lorentz and polarization effects; negligible corrections for crystal decay were also applied. The space group Pm3̅m, standard for zeolite A except for its most precise study, was determined by the program XPREP.30 Table 1 presents a summary of the experimental and crystallographic data. 2.3. SEM-EDX Analysis. After X-ray diffraction data collection, the single crystal was taken out of its capillary (exposed to the atmosphere) and attached to a sample holder with carbon tape for scanning electron microscopy energydispersive X-ray (SEM-EDX) analysis.31 The composition of the crystal was determined using a Versa 3D FIB (focused ion beam) within an Ametek EDX spectrometer and a field emission scanning electron microscope at 294 K. The results are presented in Figure 1 and Table 2.

Table 1) R1 = 0.386 and R2 = 0.801. The further steps of structure determination, as subsequent peaks are found on difference Fourier functions and identified as extraframework atoms, are presented in Table 3. The final weights were assigned using the formula w = 1/[σ2(Fo2) + (aP)2 + bP] where P = [max(Fo2,0) + 2Fc2]/3 with a and b as refined parameters. Their final values are given in Table 1. At one point (Table 3, step 13), the occupancy at Sn11 was almost double that of the chlorine atoms at Cl1 to which they bond, indicating the presence of a linear bridged Sn2Cl3+ cluster. When their occupancies were constrained to be Cl1:Sn11 = 1:2, the error indices did not increase. The Sn21 position was not refined anisotropically because the absolute value of the correlation coefficient between its x and U11 parameters was large (−0.963). The thermal parameter at Cl2 (U11 = 0.21 Å2) was unreasonably large, as was the esd of its occupancy (2.0(9)). The thermal and occupancy parameters at an atomic position often correlate highly and positively in least-squares refinement, so it appeared that both were refining to values that were too high. Considering this and a plausible geometry, the constraint Sn32:Cl2:Sn21 = 1:2:2 was applied (Table 3, step 14). The final structural parameters are presented in Table 4 and selected interatomic distances and angles are given in Table 5. Atomic scattering factors for Sn0, Cl0, O0, and T (Al0 and Si0) were used. All scattering factors were modified to account for anomalous dispersion.33,34 Additional crystallographic details are given in Table 1.

Table 2. Crystal Composition (Atomic %) by Crystallographic (SXRD) and SEM-EDX Analysesa element

SXRDb

SEM-EDX

Si Al O Sn Cl

15.25 15.25 61.10 7.65 2.04

15.4(9) 15.0(9) 59(5) 8.34(14) 1.45(9)

4. DESCRIPTION OF THE STRUCTURE 4.1. Framework Geometry. Among the three T−Oi bonds, i = 1−3, the T−O3 bond length, 1.6947(24) Å, is noticeably longer than the others (see Table 5). This is often seen in dipositive cation exchanged zeolites35−37 and is a consequence of the coordination of these cations to O3 (Table 6). For monopositive cations in zeolite A, this trend is weak or absent (Table 6).25,38−40 For the similar reasons, the T−O3−T angle is the smallest (Table 5). 4.2. Extraframework Ions: Sn2+, Sn4+, and Cl−. Per unit cell, 5.27(9) Sn2+, 0.83(9) Sn4+, and 1.64(6) Cl− ions are found at 4, 2, and 2 crystallographically distinct positions, respectively. The oxidation states of the tin ions were assigned primarily on the basis of their ionic radii, obtained by subtracting the conventional ionic radius of O2− (1.32 Å)41 from their shortest Sn−O bond lengths (Table 7). Among the resulting radii for the six tin cation positions, two are sharply smaller than the rest and in close agreement with the conventional ionic radius of

a

The zeolite crystal can be expected to have suffered some surface decomposition upon exposure to the electron beam. This can be a significant source of error. bSingle-crystal X-ray diffraction.

3. STRUCTURE DETERMINATION Full-matrix least-squares refinement (SHELXL2013)32 was done on F2 using all unique reflections. It was initiated with the atomic parameters of the framework atoms [(Si,Al), O1, O2, and O3] in dehydrated |Tl12|[Si12Al12O48]-LTA.25 Fixed weights were used initially. The initial refinements with anisotropic thermal parameters for all framework atoms converged to the high error indices (defined in footnotes of 3246

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The Journal of Physical Chemistry C Table 3. Steps of Structure Determination as Nonframework Atomic Positions Were Found number of ions or atoms per unit cella step

Sn11

Sn12

Sn13

0.19(3) 0.20(3) 0.12(3) 0.13(3) 0.13(3) 0.12(3) 0.14(3) 0.14(3) 0.12(3) 0.15(3)

3.02(15) 3.09(11) 2.93(8) 2.86(8) 2.71(8) 2.74(8) 2.79(8) 2.71(5) 2.71(5) 2.71(5) 2.74(5) 2.75(5) 2.73(5) 2.74(5)

Sn21

Sn31

error indicesb Sn32

Cl1

Cl2

R1

R2

2.0(9) 2.1(9) 0.77(14) 1.49(6)

0.386 0.161 0.114 0.100 0.098 0.092 0.086 0.084 0.068 0.069 0.069 0.068 0.068 0.067 0.069

0.801 0.528 0.419 0.402 0.369 0.352 0.341 0.323 0.222 0.225 0.222 0.221 0.221 0.216 0.224

c

1 2 3 4 5 6 7 8 9d 10e 11f 12 13g 14h 15i

0.23(3) 0.244(22) 0.37(3) 0.43(3) 0.37(3) 0.29(3) 0.30(3) 0.32(3) 0.32(3) 0.32(3) 0.33(3) 0.296(24)

1.23(7) 1.20(7) 1.37(7) 1.42(7) 1.44(6) 1.26(6) 1.53(6) 1.53(6) 1.53(6) 1.56(6) 1.56(6) 1.55(6) 1.49(6)

0.46(7) 0.53(9) 0.35(7) 0.42(7) 0.61(8) 0.61(8) 0.60(8) 0.65(8) 0.65(8) 0.64(8) 0.68(9)

0.24(5) 0.41(7) 0.33(6) 0.34(6) 0.33(7) 0.37(7) 0.37(7) 0.38(7) 0.74(3)

0.26(5) 0.24(5) 0.24(5) 0.24(5) 0.17(4) 0.160(10) 0.163(12) 0.148(12)

a

Scattering factors used are Sn0 for all Sn positions. Numbers in parentheses are the estimated standard deviations (esds) in the units of the least significant figure given for the corresponding parameter. bDefined in footnotes to Table 1. cThe framework atoms were refined anisotropically. dA two-parameter weighting system (see Table 1) was applied. eAn extinction parameter (EXTI) was introduced and refined. fSn11, Sn13, and Sn32 were refined anisotropically. gThe occupancy constraint Sn11:Cl1 = 2:1 was applied to the Sn2Cl3+ cluster. hThe occupancy constraint Sn32:Cl2 = 1:2 was applied. iThe occupancy constraint Sn32:Cl2:Sn21 = 1:2:2 was applied to the Sn3Cl24+ cluster.

Sn4+.41 Thus, the ions at those positions are assigned the 4+ oxidation state; the remainder are Sn2+ ions. 4.2.1. Sn2+ Ions. At Sn13 2.74(6) Sn2+ ions per unit cell lie opposite 6-rings on 3-fold axes. Each is 3-coordinate, bonding to three O3 framework oxygens at 2.410(7) Å (Table 5), and extends 1.30 Å into large cavity from the (111) plane of its O3 oxygen atoms (Figure 2). At Sn11, also opposite 6-rings on 3-fold axes but in sodalite cavities, 0.30(2) Sn2+ ions bond to three O3 framework oxygen atoms at 2.366(13) Å and to a Cl− ion at Cl1 at 2.65(3) Å (Figure 2). Each extends 1.22 Å into the sodalite cavity from the (111) plane of its O3 oxygen atoms. At Sn21 1.49(6) Sn2+ ions lie near 8-ring planes (Figures 4 and 5). Each is 3-coordinate, bonding to two framework oxygen atoms at 2.297(10) Å and 2.425(12) Å and to a Cl− ion at Cl2 at 2.51(12) Å. Finally, 0.74(3) Sn2+ ions at Sn32 are found in the large cavity (Figures 4 and 5). Each bonds in a trigonal planar manner to one O3 framework oxygen at 2.40(4) Å and to two Cl− ions at Cl2 at 2.50(10) Å. 4.2.2. Sn4+ Ions. At Sn31 0.68(9) Sn4+ ions per unit cell were found in the large cavity opposite the intersections of 4-, 6-, and 8-rings (Figure 4). Each bonds to an O1 oxygen atom at 2.17(3) Å, an O2 at 2.13(3) Å, and an O3 at 2.03(3) Å. The remaining 0.15(3) Sn4+ ions are at Sn12, nearly at the centers of 6-ring planes (Figure 2). Each bonds to the three O3 framework oxygen atoms of its 6-ring at 2.075(10) Å with O3− Sn12−O3 bond angles of 116.1(7)o (Table 5). Each extends only 0.45 Å into the large cavity from the (111) plane at O3. 4.2.3. Cl− Ions. At Cl1 0.148(12) Cl− ions per unit cell lie at the centers of sodalite cavities (Figure 2). Each bridges linearly between two Sn2+ ions at Sn11. The Sn11−Cl1 bond length, 2.65(3) Å, is close to the sum of the ionic radii of Sn2+ and Cl−, 0.93 + 1.81 = 2.74 Å, respectively.41 Halide ions often bridge between Sn2+ ions.42,43 In the large cavity 1.49(6) Cl− ions per unit cell were found at Cl2 (Figure 4). They bridge between the Sn2+ ions at Sn21 and Sn32 with bond lengths of 2.51(12) Å and 2.50(10) Å to

form Sn3Cl24+ (see Figure 4). To write a balanced net reaction (see Section 5), the number of Cl− ions per unit cell is increased from 1.64(6) to 1.86. Within the low occupancy positions involved, a reasonable 2.447(11) Å Sn31−Cl2 distance appeared. This bonding possibility was dismissed, however, because it would require a 3.03(5) Å Sn31···Sn32 (Sn4+···Sn2+) approach with both tin ions coordinating at an acute angle, Sn31−Cl2−Sn32 = 76(3)o, to the same chloride ion. Furthermore, the occupancy at Sn31 is sufficient for it to bond to only one Cl2 of the Sn3Cl24+ cluster; this would be expected to introduce a distortion that is not indicated by the thermal parameter at Cl2. 4.2.4. Sn31···T Distance. The present structure model contains a Sn4+···T3+or4+ distance, Sn31···T = 1.99(3) Å (Table 5), that seems to be impossibly short. The Sn31 position is well established in this work: it appears as a large and persistent peak on Fourier functions, it refines well in leastsquares (Table 4), and it is responsible for a significant lowering of the error indices (Table 3). Perhaps the structure is simply distorted locally so that this distance is inaccurately short. The possibility that some framework Al atoms have been lost as Al2Cl6(g) was considered, but that leads to a severe shortage of positive charge in the structure. Omitting Sn31 from the structure model would do the same. Other seemingly less likely explanations are possible. The possibility that some T atoms have been replaced by tin ions does not overcome the 1.99 Å distance problem, nor does the possibility that the framework had lost Al2Cl6(g) and reorganized itself to become silicon rich.

5. DISCUSSION No Tl+ was found in the product crystal. Thus, the TIE reaction performed in this study had successfully gone to completion, but not as simply as hoped for in Reaction 1. Some Cl− ions were retained and some Sn2+ ions had disproportionated. Nonetheless, TIE has allowed much more tin to be exchanged into a zeolite than had previously been possible. 3247

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Positional parameters ×105 and thermal parameters ×104 are given. Numbers in parentheses are the estimated standard deviations (esds) in the units of the least significant figure given for the corresponding parameter. bThe anisotropic temperature factor is exp[−2π2a−2(U11h2 + U22k2 + U33l2 + 2U12hk + 2U13hl + 2U23kl)]. cOccupancy factors are given as the number of atoms or ions per unit cell. dExactly, by symmetry. eThe occupancy constraint Sn11:Cl1 = 2:1 was applied to the Sn2Cl3+ cluster. fThe occupancy constraint Sn32:Cl2:Sn21 = 1:2:2 was applied to the Sn3Cl24+ cluster.

24(k) 12(h) 12(i) 24(m) 8(g) 8(g) 8(g) 48(n) 48(n) 24(m) 1(a) 48(n) T O1 O2 O3 Sn11 Sn12 Sn13 Sn21 Sn31 Sn32 Cl1 Cl2

Table 5. Selected Interatomic Distances (Å) and Angles (deg)a distances

angles

T−O1 T−O2 T−O3 mean

1.6336(17) 1.6594(21) 1.6947(24) 1.663

Sn11−O3 Sn12−O3 Sn13−O3

2.366(13) 2.075(10) 2.410(7)

Sn21−O1 Sn21−O2

2.425(12) 2.297(10)

Sn31−O1 Sn31−O2 Sn31−O3 Sn32−O3

2.17(3) 2.13(3) 2.03(3) 2.40(4)

Sn11−Cl1 Sn21−Cl2 Sn32−Cl2

2.65(3) 2.51(12) 2.50(10)

Sn31···T

1.99(3)

O1−T−O2 O1−T−O3 O2−T−O3 O3−T−O3 mean

108.3(4) 112.27(21) 106.01(22) 111.6(4) 109.5b

T−O1−T T−O2−T T−O3−T mean

163.0(6) 143.6(4) 132.4(4) 146.3

O3−Sn11−O3 O3−Sn12−O3 O3−Sn13−O3 O1−Sn21−O2 O1−Sn31−O2 O1−Sn31−O3 O2−Sn31−O3

96.2(7) 116.1(7) 93.8(4) 68.9(18) 76.4(8) 82.1(9) 80.0(9)

Sn11−Cl1−Sn11 Cl1−Sn11−O3

180c 120.7(5)

Cl2−Sn32−O3 Cl2−Sn32−Cl2 Sn32−Cl2−Sn21 Cl2−Sn21−O1 Cl2−Sn21−O2

121(3) 119(6) 103(4) 75.3(22) 81.0(17)

a

The numbers in parentheses are the estimated standard deviations (esds) in the units of the least significant digit given for the corresponding value. bVery nearly the tetrahedral angle, 109.47°. c Exactly by symmetry.

With the exception of the 4-coordinate Sn2+ ions at Sn11 in the sodalite cavities, all Sn2+ and Sn4+ ions are 3-coordinate. As is common for exchangeable cations in dehydrated zeolites, these coordination numbers are unusually low, and the coordination geometries are unique. The net reaction per unit cell based on the composition determined by this study can be written as follows: Tl12‐A + 6.93SnCl 2(g ) → Sn 2 +5.27Sn 4 +0.83Cl−1.86‐A + 12TlCl(g ) + 0.83Sn 0 (s , surface)

(2)

Reaction 2 is written without esds and contains a somewhat excessive number of significant figures. Also, to achieve charge balance, the chloride content of the zeolite has been increased from 1.64(6) to 1.86 ions per unit cell. The black color of the crystal studied is attributed to finely divided tin metal on its surface (see Reaction 2). 5.1. Sn2+ Ions. The average Sn2+−O bond length found in this study, 2.37 Å, is much like those found in other compounds of Sn2+. It is 2.22(2) Å in blue-black SnO(s) where Sn2+ is regular square-pyramidal.44 It is 2.398(20) Å in zeolite Y containing (proposed) Sn4S64+ clusters.22 The average Sn2+−O bond length is 2.302 Å in Na2Sn(C2O4)2,45 2.312 Å in SnC 2 O 4 , 46 and 2.288 Å in β-SnWO 4 . 47 In tritin(II) tetrahydroxide dinitrate they ranged from 2.14 to 2.35 Å.48 In

a

−531(222) 82(124) 1567(383) 1443(225)

82(124)

408(9) 408(9)

2(3)

2(3)

2(3)

0.296(24)e 0.15(3) 2.74(5) 1.49(6)f 0.68(9) 0.74(3)f 0.148(12)e 1.49(6)f 0.32(3) 0.14(3) 2.74(5) 1.56(6) 0.65(8) 0.37(7) 0.17(4) 2.0(9)

24 12 12 24

constrained varied

0d 0d 0d 451(29) 143(53)

U12 U13

0d 0d 0d −57(20) 143(53) 23(4) 0d 94(19) −57(20) 143(53)

U23 U33

343(7) 385(24) 465(16) 628(26) 603(63)

U22

397(8) 863(47) 465(16) 891(25) 603(63)

406(8) 739(37) 660(32) 891(25) 603(63) 496(114) 408(9) 639(32) 634(81) 1443(225) 580(106) 1507(332) 36621(9) 50000d 30429(33) 32224(41) 12692(115) 20477(182) 24666(8) 46832(61) 40368(208) 34474(461) 0d 45665(841) 18161(10) 20164(68) 30429(33) 11605(39) 12692(115) 20477(182) 24666(8) 39932(76) 26150(190) 25553(199) 0d 32861(850)

U11 or Uisob z y x

d

Wyckoff position atom position

Table 4. Positional, Thermal, and Occupancy Parametersa

0 0d 0d 11605(39) 12692(115) 20477(182) 24666(8) 1551(100) 13958(202) 25553(199) 0d 21105(957)

occupancyc

fixed

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Table 6. Comparison of Bond Lengths and Bond Angles for Some Mono- and Dipositive Cation Exchanged Forms of Zeolite A bond lengths

a

Mn+-exchanged zeolite A

T−O1

T−O2

Tl12-Aa Na12-Ab K12-Ac Cs12-A·0.5Csd

1.635(8) 1.659(2) 1.676(5) 1.686(32)

1.660(18) 1.654(2) 1.660(3) 1.651(29)

Sn6.1Cl1.8-Ae Ca6-Af Sr6-Ag Cd6-Ah

1.6336(17) 1.640(4) 1.640(6) 1.624(4)

bond angles T−O3

monopositive cations 1.685(11) 1.668(1) 1.668(2) 1.654(18) dipositive cations 1.6594(21) 1.6947(24) 1.649(3) 1.676(3) 1.659(4) 1.679(4) 1.640(8) 1.694(5)

T−O1−T

T−O2−T

T−O3−T

161.1(20) 142.1(4) 128.5(6) 141.3(40)

146.5(10) 164.2(4) 178.4(5) 162.0(65)

136.9(9) 145.6(2) 153.7(5) 143.9(28)

163.0(6) 148.4(8) 144(1) 165.2(9)

143.6(4) 166.7(7) 172 (1) 156.0(4)

132.4(4) 142.5(5) 143.6(8) 137.6(4)

Ref 25. bRef 38. cRef 39. dRef 40. eThis work. fRef 35. gRef 36. hRef 37.

Table 7. Unit Cell Charge Budget atom position Sn11 Sn12 Sn13 Sn21 Sn31 Sn32 Cl1 Cl2 Σ Sn2+ = 5.27(9)e a

occupancya

Sn−O,b Å

r,c Å

NCd

charge

0.296(24) 0.15(3) 2.74(5) 1.49(6) 0.68(9) 0.74(3) 0.148(12) 1.49(6)

2.366(13) 2.075(10) 2.410(7) 2.297(10) 2.03(3) 2.40(4)

1.05 0.75 1.09 0.97 0.71 1.09

3 3 3 2 3 3 2 2

2+ 4+ 2+ 2+ 4+ 2+ 1− 1−

Σ Cl− = 1.64(6)e

Σ Sn4+ = 0.83(9)e

charge × occ.

0.59(5)+ 0.61(12)+ 5.48(11)+ 2.98(11)+ 2.7(3)+ 1.49(6)+ 0.148(12)− 1.49(6)− Σ charges = 12.2(3)+f

b

Occupancy, ions per unit cell. Shortest M−O (metal ion to framework oxygen) bond lengths. cRadii of Sn ions obtained by subtracting 1.32 Å (the conventional radius of the oxide ion, ref 41) from the shortest Sn−O bond lengths. The conventional ionic radius of Sn2+ is 0.93 Å, Sn4+ 0.71 Å (ref 41). dCoordination numbers. eNumber of ions per unit cell. fTotal charge per unit cell. Within experimental error this balances the expected charge of the zeolite framework per unit cell (Si12Al12O48), 12−.

Figure 2. A stereoview of a sodalite cavity with Sn2+ (Sn11 and Sn13) and Sn4+ (Sn12) ions on 3-fold axes. About one in seven sodalite cavities contains the linear Sn11−Cl1−Sn11 cluster. The zeolite A framework is drawn with open bonds; solid bonds are used to show the coordination about the Snn+ and Cl− ions. Ellipsoids of 20% probability are shown.

a series of tin(II) halide sulfates, the average Sn2+−O bond was 2.52 Å.49 The Sn2+ ion at Sn32, at the center of Sn3Cl24+ cluster (Figure 4, Section 5.3), is nearly trigonal planar with bond angles Cl2−Sn32−Cl2 = 119(6)° and O3−Sn32−Cl2 = 121(3)°. Trigonal planar coordination about tin had been seen in organometallic complexes like Pd[Sn{N(SiMe3)2}2]3,9,50,51 which have bulky ligands, but it is generally not seen in conventional inorganic compounds. 5.2. Sn4+ Ions. The average Sn4+−O bond length, 2.05 Å, is normal. It is the same as the mean bond length in SnO2(s), 2.053(5) Å.52 The Sn4+−O bond lengths in Li2[Sn(OH)6],53 Na2Sn(OH)6,54 K2Sn(OH)6,54 Sr2Sn(OH)8,55 and Ba[Sn-

Figure 3. A stereoview showing the Sn4+ ion at Sn31 opposite the intersection of a 4-, 6-, and 8-ring. See the caption to Figure 2 for other details. 3249

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spontaneously; ΔG0298 = −5.9 kJ mol−1 for 2SnO(s) → SnO2(s) + Sn(l).63 Giefers et al. reported the kinetics of the disproportionation of SnO to SnO2 and Sn0 using ex- and in situ X-ray powder diffraction.64 In this report, the disproportionation of Sn2+ presumably occurred during the reaction of Tl-A with SnCl2 at 723 K. 5.5. Charge Balance. As summarized in Table 7, the sum of the charges of the extraframework cations and anions is 12.2(3)+, nicely balancing the expected charge of the zeolite framework 12−.38 This supports the reliability of the crystallographically determined occupancies, the assignments of oxidation states at the six tin equipoints, and the assignments of atom identities at the chloride positions. 5.6. Verification of the Atomic Composition by SEMEDX Analysis. The atomic composition of Sn6.1Cl1.8-A was confirmed using SEM−EDX (see Table 2). Considering the relatively large esds in the EDX analysis, due in part to the zeolite decomposition to be expected in the electron beam and the possible decomposition of the zeolite upon exposure to atmosphere, acceptable agreement is seen for each element. No Tl peaks were observed, indicating that the crystal studied is a tin aluminosilicate free of thallium. Finally, as is often the case, a Na peak is present at 1.04 keV in the EDX analysis although it was not found crystallographically. It cannot be from the SnCl2 reagent because NaCl (0.4 ppm) is not volatile at 723 K.

Figure 4. A stereoview of the Sn3Cl24+ cluster in a large cavity. See the caption to Figure 2 for other details.

(OH)6]·5H2O56 are 2.052(11) Å, 2.071(4) Å, 2.060(1) Å, 2.059(8) Å, and 2.055(8) Å, respectively. 5.3. Sn3Cl24+ and Sn2Cl3+ Clusters. The Sn2+−Cl− bond lengths in the Sn3Cl24+ cluster, 2.51(12) Å, and 2.50(10) Å, are reasonable. The three shortest bonds in SnCl2(s), where Sn2+ is irregularly octahedral, are 2.67 Å, 2.78 Å, and 2.78 Å.57 Sn2+− Cl− is 2.54(3) and 2.63(3) Å in K2SnCl4·H2O,57 and it is 2.431(2) Å in 2,6-(Me2NCH2)2C6H3SnCl.58 The Sn2+−Cl− bond lengths in W(CO) 5 [SnCl 2 (OC 4 H 8 )] and W(CO)5[(SnCl2(OC4H8)2)] range from 2.352(3) to 2.375(2) Å.59 In the linear Sn2Cl3+ cluster, the Sn2+−Cl− bond lengths are a little longer, 2.65(3) Å, suggesting that this cluster has been stretched to fit this site. The zigzag Sn3Cl24+ cluster (Figure 4) looks like a segment of the infinite −Sn−Cl−Sn−Cl− chains in the crystal structure of SnCl2,57 and the angle at Cl2, 103(4)°, is the same as that in SnCl2(s), 105°. The three central ions of the Sn3Cl24+ cluster may be viewed as a reagent SnCl2 molecule, Cl2−Sn32−Cl2, that has been retained by the tin exchanged zeolite. Its bond lengths and angle, 2.50(10) Å and 119(6)°, can be compared to those in SnCl2(g), 2.335(3) Å and 98.1°.60 The lone pair of electrons at Sn2+, responsible for the very bent angle in SnCl2(g), is apparently more delocalized in this intrazeolitic complex, allowing the angle to increase appreciably.61 The Sn2+ ions at Sn13 and Sn21 can also be expected to each have a lone pair of electrons in their coordination spheres. 5.4. Disproportionation of Sn2+. Sn2+ ions can disproportionate into Sn4+ and Sn0. This was first noted using tartrates by Johan Gadolin in 1788.62 Moreno et al. used Mössbauer spectroscopy to study the disproportionation of SnO at 723 K.63 SnO is not very stable at 723 K; it disproportionates

6. SUMMARY The extraframework cations Sn2+ and Sn4+ were introduced into zeolite A, |Na12|[Si12Al12O48]-LTA, by thallous ion exchange (TIE), a vapor phase ion exchange method. The structure of |Sn2+5.3Sn4+0.8Cl−1.8|[Si12Al12O48]-LTA was determined crystallographically. SnCl2(g) reacted with Tl-A to replace all of the Tl+ ions in the zeolite, but 1.8 Cl− ions were retained per unit cell. The resulting tin ions, 5.3 Sn2+ and 0.8 Sn4+ per unit cell, occupy four and two crystallographically distinct positions, respectively. There are 3.04 Sn2+ and 0.15 Sn4+ ions on 3-fold axes associated with 6-rings. Another 1.49 Sn2+ ions associate with 8-rings. The remaining 0.74 Sn2+ ions in the large cavity participate in Sn3Cl24+ clusters. Opposite the intersections of 4-, 6-, and 8-rings in the large cavity, 0.68 Sn4+ ions are found. The remaining Cl− ions bridge linearly between Sn2+ ions in the sodalite cavity to form Sn2Cl3+.

Figure 5. A stereoview of the large cavity showing all extraframework Snn+ and Cl− ions. See the caption to Figure 2 for other details. 3250

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(16) Davies, C. G.; Donaldson, J. D. Basic Tin(II) Sulphates. J. Chem. Soc. A 1967, 1790−1793. (17) Sen, D.; Heo, N. H.; Kang, H.-C.; Seff, K. Using InCl Vapor to Ion Exchange Indium into Zeolite Na-Y. Single-Crystal Structure of |In25.8Cl0.8Na37.0|[Si121Al71O384]-FAU Containing In+, In3+, and In57+Cl−-In57+. J. Phys. Chem. C 2011, 115, 23470−23479. (18) Sen, D.; Heo, N. H.; Seff, K. Using InCl Vapor to Ion Exchange Indium into Zeolite Na−X. Single Crystal Structure of |In34Na50| [Si100Al92O384]−FAU Containing In57+ and In+. J. Phys. Chem. C 2012, 116, 14445−14453. (19) Peapples-Montgometry, B. P.; Seff, K. Synthesis of Fully Dehydrated Fully Zn2+-Exchanged Zeolite Y and Its Crystal Structure Determined by Pulsed-Neutron Diffraction. J. Phys. Chem. 1992, 96, 5962−5965. (20) Kim, J. Y.; Kim, C. W.; Park, Y. K.; Kang, N.-Y.; Heo, N. H.; Seff, K. First Successful Application of the Thallous Ion Exchange (TIE) Method. Preparation of Fully Indium-Exchanged Zeolite Y (FAU, Si/Al = 1.69). J. Phys. Chem. C 2014, 118, 24655−24661. (21) Seff, K. A General Method for the Ion Exchange of Zeolites Utilizing the Volatility of Thallous Compounds as Leaving Products. J. Phys. Chem. C 2010, 114, 13295−13299. (22) Bowes, C. L.; Ozin, G. A. Tin Sulfide Clusters in Zeolite Y, Sn4S6-Y. J. Mater. Chem. 1998, 8, 1281−1289. (23) Handbook of Chemistry and Physics, 91st ed.; Haynes, W. M., Ed.; CRC Press: Boca Raton, FL, 2011; pp 6−89. (24) Charnell, J. F. Gel Growth of Large Crystals of Sodium A and Sodium X Zeolites. J. Cryst. Growth 1971, 8, 291−294. (25) Heo, N. H.; Choi, H. C.; Jung, S. W.; Park, M.; Seff, K. Complete Redox Exchange of Indium for Tl+ in Zeolite A. Crystal Structures of Anhydrous Tl12-A and In10-A·In. Indium Appears as In2+, In+, and In0. The Clusters (In5)8+ and (In3)2+ Are Proposed. J. Phys. Chem. B 1997, 101, 5531−5539. (26) Heo, N. H.; Chun, C. W.; Park, J. S.; Lim, W. T.; Park, M.; Li, S. L.; Zhou, L. P.; Seff, K. Reaction of Fully Indium-Exchanged Zeolite A with Hydrogen Sulfide. Crystal Structures of Indium-Exchanged Zeolite A Containing In2S, InSH, Sorbed H2S, and (In5)7+. J. Phys. Chem. B 2002, 106, 4578−4587. (27) Heo, N. H.; Kim, S. H.; Choi, H. C.; Jung, S. W.; Seff, K. Crystal Structure of Indium-Exchanged Zeolite A Containing Sorbed Disulfur. J. Phys. Chem. B 1998, 102, 17−23. (28) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data Collected in Oscillation Mode. Methods Enzymol. 1997, 276, 307−326. (29) Arvai, A. J.; Nielsen, C. ADSC Quantum-210 ADX Program, Area Detector; Poway, CA, USA, 1983. (30) XPREP, Version 6.12, Program for Automatic Space Group Determination; Bruker AXS Inc.: Madison, WI, 2001. (31) Kim, C. W.; Kang, H.-C.; Heo, N. H.; Seff, K. Encapsulating Photoluminescent Materials in Zeolites. Crystal Structure of Fully Dehydrated Zeolite Y (Si/Al = 1.69) Containing Eu3+. J. Phys. Chem. C 2014, 118, 11014−11025. (32) Sheldrick, G. M. A Short History of SHELX. Acta Crystallogr., Sect. A 2008, 64, 112−122. (33) Cromer, D. T. Anomalous Dispersion Corrections Computed from Self-Consistent Field Relativistic Dirac-Slater Wave Functions. Acta Crystallogr. 1965, 18, 17−23. (34) International Tables for X-ray Crystallography; Kynoch Press: Birmingham, 1974; Vol. IV, p 71. (35) Pluth, J. J.; Smith, J. V. Crystal Structure of Dehydrated CaExchanged Zeolite A. Absence of Near-Zero-Coordinate Ca2+. Presence of Al Complex. J. Am. Chem. Soc. 1983, 105, 1192−1195. (36) Pluth, J. J.; Smith, J. V. Crystal Structure of Dehydrated SrExchanged Zeolite A. Absence of Near-Zero-Coordinate Sr2+. Presence of Al Complex. J. Am. Chem. Soc. 1982, 104, 6977−6982. (37) Koh, K. N.; Kim, U. S.; Kim, D. S.; Kim, Y. Crystal Structures of Vacuum Dehydrated Fully Cd2+-Exchanged Zeolite A and its Ethylene Sorption Complex. Bull. Korean Chem. Soc. 1991, 12, 178−181. (38) Pluth, J. J.; Smith, J. V. Accurate Redetermination of Crystal Structure of Dehydrated Zeolite A. Absence of Near Zero

ASSOCIATED CONTENT

S Supporting Information *

Observed and calculated structure factors squared with esds. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Tel: +82 53 950 5589. Fax: +82 53 950 6594. E-mail: nhheo@ knu.ac.kr. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge the Photon Factory, High Energy Accelerator Research Organization, KEK, Tsukuba, Japan, for the use of their diffractometer and computing facilities. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (No. NRF-2014R1A2A1A11054075).

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REFERENCES

(1) Corma, A. From Microporous to Mesoporous Molecular Sieve Materials and Their Use in Catalysis. Chem. Rev. 1997, 97, 2373− 2419. (2) Davis, M. E. Ordered Porous Materials for Emerging Applications. Nature 2002, 417, 813−821. (3) Vjunov, A.; Fulton, J. L.; Huthwelker, T.; Pin, S.; Mei, D.; Schenter, G. K.; Govind, N.; Camaioni, D. M.; Hu, J. Z.; Lercher, J. A. Quantitatively Probing the Al Distribution in Zeolites. J. Am. Chem. Soc. 2014, 136, 8296−8306. (4) Dempsey, E. In Molecular Sieves. Soc. Chem. Industry: London 1968, 293−305. (5) Frising, T.; Leflaive, P. Extraframework Cation Distributions in X and Y Faujasite Zeolites: A Review. Microporous Mesoporous Mater. 2008, 114, 27−63. (6) Shah, A. K.; Khan, N. H.; Sethia, G.; Saravanan, S.; Kureshy, I. R.; Abdi, S. H. R.; Bajaj, H. C. Tin Exchanged Zeolite as Catalyst for Direct Synthesis of α-Amino Nitriles under Solvent-free Conditions. Appl. Catal. A: General 2012, 419−420, 22−30. (7) Bermejo-Deval, R.; Gounder, R.; Davis, M. E. Framework and Extraframework Tin Sites in Zeolite Beta React Glucose Differently. ACS Catal. 2012, 2, 2705−2713. (8) Knudsen, N.; Krogh Andersen, E.; Krogh Andersen, I. G.; Norby, P.; Skou, E. Tin-zeolites, Synthesis and Ionic Conductivity. Solid State Ionics 1993, 61, 153−161. (9) Tin Chemistry; Fundamentals, Frontiers, and Applications; Gielen, M.; Davies, A.; Pannell, K.; and Tiekink, E., Eds.; Wiley: New York, 2008; pp 241−250. (10) Shibasaki, M.; Kanai, M.; Mita, T. In Organic Reactions: The Catalytic Asymmetric Strecker Reaction; Querman, L. E., Ed.; Wiley: New York, 2008; Vol. 70, pp 1−5. (11) Moliner, M.; Roman-Leshkov, Y.; Davis, M. E. Tin-containing Zeolites are Highly Active Catalysts for the Isomerization of Glucose in Water. Proc. Natl. Acad. Sci. U. S. A. 2010, 107, 6164−6168. (12) Knudsen, N.; Krogh Andersen, E.; Krogh Andersen, I. G.; Skou, E. Tin-mordenites, Synthesis and Ionic Conductivity. Solid State Ionics 1989, 35, 51−55. (13) Krogh Andersen, I. G.; Krogh Andersen, E.; Knudsen, N.; Skou, E. Study of Preparation and ac/dc Conductivity of Tin-Zeolite-Y Materials. Solid State Ionics 1991, 46, 89−93. (14) Baes, C. F. Jr.; Mesmer, R. E. The Hydrolysis of Cations; Wiley: New York, 1976; pp 319−323. (15) Tobias, S. R. Studies on the Hydrolysis of Metal Ions 21. The Hydrolysis of the Tin(II) Ion, Sn2+. Acta Chem. Scand. 1958, 12, 198− 223. 3251

DOI: 10.1021/jp512600h J. Phys. Chem. C 2015, 119, 3244−3252

Article

The Journal of Physical Chemistry C

Function of SnCl2, SnBr2, SnI2, Ga2O and Tl2O. J. Mol. Struct. 1985, 119, 263−270. (61) Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochmann, M. Advanced Inorganic Chemistry; 6th ed.; Wiley: New York, 1999; p 265. (62) Gadolin, J. Om Kopparens formaga at falla Tenn utur defs Uplosning i Vinftens-fyra. Kongl. Sv. Vet. Acad. Handl. 1788, 9, 186− 197. (63) Moreno, M. S.; Punte, G.; Rigotti, G.; Mercader, R. C.; Weisz, A. D.; Blesa, M. A. Kinetic Study of the Disproportionation of Tin Monoxide. Solid State Ionics 2001, 144, 81−86. (64) Giefers, H.; Porsch, F.; Wortmann, G. Kinetics of the Disproportionation of SnO. Solid State Ionics 2005, 176, 199−207.

Coordination of Sodium. Refinement of Si,Al-Ordered Superstructure. J. Am. Chem. Soc. 1980, 102, 4704−4708. (39) Leung, P. C. W.; Kunz, K. B.; Seff, K.; Maxwell, I. E. Crystal Structures of Hydrated and Dehydrated Potassium-Exchanged Zeolite A. J. Phys. Chem. 1975, 79, 2158−2162. (40) Heo, N. H.; Seff, K. The reactions of Cesium with Dehydrated Calcium Zeolite A: Crystal Structures of Cs6Ca3-A, Cs11Ca0.5-A·0.5Cs, and Cs12-A·0.5Cs. Zeolites 1992, 12, 819−825. (41) Handbook of Chemistry and Physics, 64th ed.; Weast, R. C., Ed.; CRC Press: Cleveland, OH, 1983; p F−170. (42) Housecroft, C.; Sharpe, A. G. Inorganic Chemistry, 2nd ed.; Prentice Hall: Upper Saddle River, NJ, 2004; p 522. (43) Donaldson, J. D. The Chemistry of Bivalent Tin. In Progress in Inorganic Chemistry; Wiley: New York, 1967; Vol. 8, pp 287−356. (44) Pannetier, G.; Denes, G. Tin(II) Oxide: Structure Refinement and Thermal Expansion. Acta Crystallogr., Sect. B 1980, 36, 2763− 2765. (45) Donaldson, J. D.; Donoghue, M. T.; Smith, C. H. The Crystal Structure of Disodium Bisoxalatostannate(II), Na2Sn(C2O4)2. Acta Crystallogr., Sect. B 1976, 32, 2098−2101. (46) Gleizes, A.; Galy, J. Polyèdre de coordination de l′etain(II) dans SnC2O4: Relations structurales entre SnC2O4, Na2C2O4 et Na2Sn(C2O4)2. J. Solid State Chem. 1979, 30, 23−33. (47) Jeitschko, W.; Sleight, A. W. Synthesis, Properties and Crystal Structure of β-SnWO4. Acta Crystallogr., Sect. B 1972, 28, 3174−3178. (48) Donaldson, J. D.; Grimes, S. M.; Johnston, S. R.; Abrahams, I. Characterisation of the Tin(II) Hydroxide Cation [Sn3(OH)4]2+, and Crystal Structure of Tritin(II) Tetrahydroxide Dinitrate. J. Chem. Soc., Dalton Trans. 1995, 2273−2276. (49) Donaldson, J. D.; Grimes, S. M. Novel Tin(II) Sites in X-Ray Crystal Structures of the Tin(II) Halide Sulphates K3Sn2(SO4)3X (X = Br or Cl). J. Chem. Soc., Dalton Trans. 1984, 1301−1305. (50) Hitchcock, P. B.; Lappert, M. F.; Misra, M. C. Homoleptic, Three-coordinate Group 8c Noble Metal(0) Complexes Having Ge or ″Sn″ Ligands, [M{M′(NR2)2}3] (M = Pd or Pt, M′ = Ge or Sn, R = SiMe3), and the X-Ray Structure of One of Them (M = Pd, M″ = Sn). J. Chem. Soc., Chem. Commun. 1985, 863−864. (51) Tin Chemistry: Fundamentals, Frontiers, and Applications; Gielen, M.; Davies, A.; Pannell, K.; Tiekink, E., Eds.; Wiley: New York, 2008; p 243. (52) Baur, W. H. Uber die Verfeinerung der Kristallstrukturbestimmung einiger Vertreter des Rutiltyps: TiO2, SnO2, GeO2, und MgF2. Acta Crystallogr. 1956, 9, 515−520. (53) Yang, S.; Zavalij, P. Y.; Whittingham, M. S. Li2Sn(OH)6. Acta Crystallogr., Sect. C 2000, 57, 228−229. (54) Jacobs, H.; Stahl, R. Redetermination of the Crystal Structures of the Hexahydroxometallates Na2Sn(OH)6, K2Sn(OH)6, and K2Pb(OH)6. Z. Anorg. Allg. Chem. 2000, 626, 1863−1866. (55) Wu, M.; Li, X.; Shen, G.; Li, J.; Xu, R.; Proserpio, D. M. Hydrothermal Synthesis and Structural Characterization of a Novel Hydroxo Stannate: Sr2Sn(OH)8. J. Solid State Chem. 2000, 151, 56− 60. (56) Kamaha, S.; Reuter, H. Ternary Hydroxides II. Synthesis and Crystal Structure of the Layered Barium Hexahydroxidostannate(IV) Pentahydrate, Ba[Sn(OH)6]·5H2O. Z. Anorg. Allg. Chem. 2009, 635, 2058−2064. (57) Rundle, R. E.; Olson, D. H. The Crystal Chemistry of Divalent Tin. Inorg. Chem. 1964, 3, 596−598. (58) Martincova, J.; Dostal, L.; Ruzicka, A.; Taraba, J.; Jambor, R. Palladium(II) Complexes of the (N,C,N)SnCl Stannylene. Organometallics 2007, 26, 4102−4104. (59) Balch, A. L.; Oram, D. E. Four- and Five-Coordinate Tin(II) (Stannylene) Compounds: Crystal and Molecular Structures of W(CO)5{SnCl2(OC4H8)} and W(CO)5{SnCl2(OC4H8)2}. Organometallics 1988, 7, 155−158. (60) Nasarenko, A. Ya.; Spiridonov, V. P.; Butayev, B. S.; Zasorin, E. Z. Second-order Perturbation Approach to Anharmonic Analysis of Molecules by Electron Diffraction: Part III. Morse-like Potential 3252

DOI: 10.1021/jp512600h J. Phys. Chem. C 2015, 119, 3244−3252