A Pentahydrated Diorganotin Cation. Cocrystallization of [{n-Bu2Sn

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Organometallics 2009, 28, 4974–4978 DOI: 10.1021/om9004803

A Pentahydrated Diorganotin Cation. Cocrystallization of [{n-Bu2Sn(H2O)5}][CF3SO3]2 and [{n-Bu2Sn(BPDO-II)2(H2O)2}][CF3SO3]2 Vadapalli Chandrasekhar and Puja Singh Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India Received June 7, 2009

A 1:2:1 reaction of [n-Bu2SnO]n, trifluoromethanesulfonic acid, and 4,40 -bipyridine N,N-dioxide (BPDO-II) afforded a cocrystal (1 3 H2O) of the unprecedented pentahydrated diorganotin cation [{nBu2Sn(H2O)5}][CF3SO3]2 (1A) and its coordination product [{n-Bu2Sn(BPDO-II)2(H2O)2}][CF3SO3]2 (1B). A variation in crystallization conditions led to the isolation of a coordination polymer, [{n-Bu2Sn(μ-BPDO-II)(H2O)2}{CF3SO3}2]n (2).

We have been interested, recently, in the isolation of hydrated organotin cations and their controlled substitution or condensation as a part of our longstanding research program on organostannoxanes.1 During our efforts in this direction we have been successful in preparing hydrated organotin cations in a one-pot reaction involving diorganotin precursors and weakly coordinating sulfonic acids.2-4 However, it is known that analogous reactions involving sulfonic acids such as CF3SO3H do not lead to fully hydrated organotin triflates,5,6 and consequently structural characterization of the latter has remained elusive, to date. Apart from the fact that hydrated organotin cations are possible intermediates en route to the formation of organostannoxanes,6,7 these can also be viewed as starting materials for organotin (1) (a) Chandrasekhar, V.; Gopal, K.; Thilagar, P. Acc. Chem. Res. 2007, 46, 420. (b) Chandrasekhar, V.; Sasikumar, P.; Singh, P.; Thirumoorthi, R.; Senapati, T. J. Chem. Sci. 2008, 120, 105. (c) Chandrasekhar, V.; Gopal, K.; Sasikumar, P.; Thirumoorthi, R. Coord. Chem. Rev. 2005, 249, 1745. (d) Chandrasekhar, V.; Nagendran, S.; Baskar, V. Coord. Chem. Rev. 2002, 235, 1. (2) (a) Chandrasekhar, V.; Boomishankar, R.; Singh, S.; Steiner, A.; Zacchini, S. Organometallics 2002, 21, 4575. (b) Chandrasekhar, V.; Boomishankar, R.; Steiner, A.; Bickley, J. F. Organometallics 2003, 22, 3342. (3) Chandrasekhar, V.; Boomishankar, R.; Kandasamy, G.; Sasikumar, P.; Singh, P.; Steiner, A.; Zacchini, S. Eur. J. Inorg. Chem. 2006, 4129. (4) Chandrasekhar, V.; Singh, P. Organometallics 2009, 28, 42. (5) (a) Beckmann, J.; Dakternieks, D.; Duthie, A.; Mitchell, C. Organometallics 2004, 23, 6150. (b) Beckmann, J.; Dakternieks, D.; Duthie, A.; Kuan, F. S. Organometallics 2003, 22, 4399. (c) Beckmann, J.; Dakternieks, D.; Duthie, A.; Jurkschat, K.; Mehring, M.; Mitchell, C.; Sch€ urmann, M. Eur. J. Inorg. Chem. 2003, 4356. (d) Beckmann, J.; Dakternieks, D.; Duthie, A.; Mitchell, C. Organometallics 2003, 22, 2161. (6) Sakamoto, K.; Ikeda, H.; Akashi, H.; Fukuyama, T.; Orita, A.; Otera, J. Organometallics 2000, 19, 3242. (7) (a) Rochow, E. G.; Seyferth, D. J. Am. Chem. Soc. 1953, 75, 2877. (b) Yasuda, K.; Okawara, R. J. Organomet. Chem. 1965, 3, 76. (c) Yasuda, K.; Matsumoto, H.; Okawara, R. J. Organomet. Chem. 1966, 6, 528. (d) Hilton, J.; Nunn, E. K.; Wallwork, S. C. J. Chem. Soc., Dalton Trans. 1973, 173. (e) Domingos, A. M.; Sheldrick, G. M. J. Chem. Soc., Dalton Trans. 1974, 475. (f ) Natsume, T.; Aizawa, S.; Hatano, K.; Funahashi, S. J. Chem. Soc., Dalton Trans. 1994, 2749. (g) Sakamoto, K.; Hamada, Y.; Akashi, H.; Orita, A.; Otera, J. Organometallics 1999, 18, 3555. (h) Orita, A.; Xiang, J.; Sakamoto, K.; Otera, J. J. Organomet. Chem. 2001, 624, 287. pubs.acs.org/Organometallics

Published on Web 08/11/2009

supramolecular assemblies.8 In this regard, we have been interested in generating hydrated organotin cations in situ and utilizing them for further reactions. We reasoned that the coordinated water molecules on tin can undergo condensation or substitution reactions, depending on the reaction conditions. Efforts to steer the reaction toward replacement of water molecules must be based on the use of ligands that are only mildly basic. Beckmann and co-workers, for example, have shown that phosphine oxides can effectively replace water molecules on hydrated organotin cations without any condensation.9 We have reasoned that the bifunctional reagent 4,40 -bipyridine-N,N-dioxide (abbreviated as BPDO-II) would be an ideal ligand to generate coordination polymers/molecular squares upon reactions with hydrated tin cations. While these expectations were not completely belied, in a reaction involving [n-Bu2SnO]n, CF3SO3H, and BPDO-II we were able to isolate the interesting cocrystal [{n-Bu2Sn(H2O)5}{CF3SO3}2] 3 [{n-Bu2SnH2O)2(BPDO-II)2}{CF3SO3}2] 3 H2O (1 3 H2O) that contained an unusual hydrated diorganotin cation possessing five coordinated water molecules along with another diorganotin cation that possessed two water molecules and two BPDO-II molecules of coordination. Evidence from the literature suggests that the existence of pentahydrated metal cations is infrequent10 among transition- and lanthanide-metal ions and is also rare among maingroup-metal ions. In the current instance a strong hydrogen-bonding interaction between the pentaaquatin motif [n-Bu2Sn(H2O)5][CF3SO3]2 (1A) and its coordination product [n-Bu2Sn(BPDO-II)2(H2O)2][CF3SO3]2 (1B) appears to be the driving force for the stabilization of the former. 1A also represents the first example of a fully hydrated organotin triflate. In addition to 1 3 H2O, we also report the formation of a coordination polymer, [{nBu2Sn(μ-BPDO-II)(H2O)2}{CF3SO3}2]n (2). Interestingly, (8) Chandrasekhar, V.; Singh, P. Organometallics 2007, 26, 2833. (9) Beckmann, J.; Dakternieks, D.; Duthie, A.; Mitchell, C. Dalton Trans. 2003, 3258. (10) Shivaiah, V.; Das, S. K. Angew. Chem., Int. Ed. 2006, 45, 245. r 2009 American Chemical Society

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Figure 1. ORTEP representation of the two dications of 1 3 H2O. Hydrogen atoms have been omitted for clarity. Scheme 1. Synthesis of 1 and 2

BPDO-II binds to tin in 1B in a monodentate manner, leaving one coordination site free. On the other hand, in 2 the coordination mode of BPDO-II is bidentate, which results in the formation of a polymeric structure.

Results and Discussion Synthesis of 1 3 H2O and 2. A 1:2:1 reaction of [n-Bu2SnO]n, CF3SO3H, and BPDO-II, under ambient conditions, afforded a cream-colored solid (1a), found to be soluble in methanol. While recrystallization of 1a from methanol/diethyl ether afforded crystals of 1 3 H2O within 1 week, slow evaporation of a solution of 1a in a mixture of methanol and dimethylformamide, over a relatively longer time period, resulted in the crystallization of 2 (Scheme 1). The Sn:L ratio (L=BPDO-II) in both 1 3 H2O and 2 is 1:1, suggesting that the species formed in this reaction follows the sequence 1A f 1B f 2. The 119Sn NMR of 1a in CD3OD and (CD3)2SO showed single peaks at 353.7 and -391.9 ppm, respectively, indicating possible ligand exchange in solution. ESI-MS spectrum of 1 3 H2O in absolute methanol reveals the highest observable peak at m/z 1649.26 (0.2%), which may be assigned to the species [(n-Bu2Sn)2(BPDO-II)2(CF3SO3)4(MeOH)6(H2O) þ H]þ; this species is formed under the conditions of the ESI-MS experiment in positive ionization mode, as a result of the exchange of water molecules with methanol (Figure S1a, Supporting Information). In addition, two intense peaks at m/z 807.13 and 821.15 are observed which could be assigned as arising due to [{n-Bu2Sn}3(OMe)2(O)(HCOO)]þ and [{n-Bu2Sn}3(OMe)(OH)(O)(HCOO)]þ, respectively. The presence of other intense peaks at m/z 279.03, 467.10, 527.08, and 631.03 also indicate the generation of formate ions in solution (Figures S1b and S2, Supporting Information). The ESI-MS spectrum of 1 3 H2O,

Table 1. Selected Bond Distances and Bond Angles for 1 3 H2O Sn1-C1 Sn1-O1 Sn1-O2 Sn1-O3

C1-Sn1-C1* O3-Sn1-O3* O3*-Sn1-O2* O2*-Sn1-O1 O1-Sn1-O2 O2-Sn1-O3 O1-Sn1-O3 O1-Sn1-O3* O2-Sn1-O2* O2-Sn1-O3

Bond Distances (A˚) 2.111(4) Sn2-C5 2.523(4) Sn2-O4 2.334(3) Sn2-O5 2.292(3) N1-O5 Bond Angles (deg) 173.9(2) O3-Sn1-O2* 77.32(15) C5-Sn2-C5* 72.46(10) O4-Sn2-O4* 69.37(7) O5-Sn2-O5* 69.36(7) O5-Sn2-O4 72.46(10) O5*-Sn2-O4 141.34(7) C5-Sn2-O4 141.34(7) C5-Sn2-O5 138.73(14) C5-Sn2-O4* 148.41(10) C5-Sn2-O5*

2.129(4) 2.262(3) 2.210(3) 1.347(4)

148.41(10) 180.0(2) 180.0 180.0(1) 90.67(10) 89.33(10) 92.51(13) 84.83(13) 87.49(13) 95.17(13)

when recorded under negative ionization mode, shows a peak at m/z 1576.9623 (3.1%) which may be assigned to the species [(BPDO-II)2 (n-Bu2Sn)2 (H 2O)5(CF3SO3 )4 (MeOH)(OH)](Figure S3, Supporting Information). Species containing formate ion are also detected in the ESI-MS spectrum recorded under negative ionization conditions (Figure S4, Supporting Information). The source of the formate anion is believed to be atmospheric carbon dioxide. Fixation of carbon dioxide by organostannoxanes and hybrid stannoxanes/telluroxanes has been reported earlier.11 Such a phenomenon has also been observed for β-diketiminate tin(II) hydride.12 In the present (11) (a) Beckmann, J.; Dakternieks, D.; Duthie, A.; Lewcenko, N. A.; Mitchell, C. Angew. Chem., Int. Ed. 2004, 43, 6683. (b) Jousseaume, B. Mikrochim. Acta 1992, 109, 5. (12) Jana, A.; Roesky, H. W.; Schulzke, C.; Doring, A. Angew. Chem., Int. Ed. 2008, 47, 1.

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Table 2. Hydrogen-Bonding Parameters for 1 3 H2O D-H 3 3 3 A O4-H58 3 3 O3-H55 3 3 O2-H53 3 3 O13-H59 3 O2-H54 3 3 O4-H57 3 3 O3-H56 3 3 O1-H51 3 3 O1-H51 3 3

3 O8 3 O6 3 O13 3 3 O11 3 O6 3 O9 3 O10 3 O6 3 O11

D-H (A˚)

H 3 3 3 A (A˚)

D 3 3 3 A (A˚)

D-H 3 3 3 A (deg)

0.796(4) 0.796(3) 0.806(4) 0.941(6) 0.793(5) 0.798(4) 0.791(3) 0.778(4) 0.778(4)

1.872(4) 1.923(3) 1.971(4) 1.840(6) 1.894(5) 1.891(4) 1.935(3) 2.435(4) 2.480(5)

2.664(4) 2.700(4) 2.769(4) 2.763(4) 2.681(4) 2.678(4) 2.724(4) 3.053(2) 3.107(5)

172.41(35) 165.36(32) 170.26(40) 166.1(5) 171.33(49) 168.53(40) 175.99(29) 137.36(43) 138.61(43)

instance, however, we were unable to obtain a crystalline product involving the incorporation of CO2. Molecular and Crystal Structures of 1 3 H2O and 2. The asymmetric unit of 1 3 H2O (Figure S5, Supporting Information) contains half of both the building blocks (two tin atoms each having a structure occupancy factor of 0.5) and half of one lattice water molecule. Figure 1 illustrates [{n-Bu2Sn(H2O)5}{n-Bu2Sn(BPDO-II)2(H2O)2}]4þ, which contains two subunits, [n-Bu2Sn(H2O)5]2þ (1A) and [n-Bu2Sn(BPDO-II)2(H2O)2]2þ (1B). 1A consists of the heptacoordinated tin center Sn1 (2C, 5O), exhibiting a pentagonal-bipyramidal geometry (Figure S6a, Supporting Information). The five oxygen atoms of the coordinated water molecules occupy the vertices of a pentagon, while the two carbon atoms of the two trans n-butyl groups occupy the two axial positions. The Sn1-Ow distances range from 2.29 to 2.52 A˚, among which Sn1-O1 is the longest while Sn1-O3 is the shortest (Sn1-O1 = 2.523(4) A˚, Sn1-O2 = 2.334(3) A˚, Sn1-O3 = 2.292(3) A˚; average Sn1-Ow = 2.382(3) A˚, Table 1). The C-Sn-C and OSn-O bond angles are as follows: C1-Sn1-C1*=173.9(2)°, O1-Sn1-O2 = 69.36(7)°, O2-Sn1-O3 = 72.46(10)°, O3Sn1-O3*=77.32°, O3*-Sn1-O2=72.46(10)°, O2*-Sn1-O1 = 69.37(7)° (Table 1). The subunit 1B contains the hexacoordinated tin center Sn2 (2C, 4O), whose octahedral coordination environment is completed by two oxygen atoms of two trans-BPDO-II molecules (O5 and O5*), two oxygen atoms of coordinated water molecules (O4 and O4*), and two carbon atoms from two trans n-butyl groups. In this case the SnOw(O4) distance is 2.262(3) A˚ (Table 1), which is relatively shorter than that found in the [n-Bu2Sn(H2O)5]2þ motif. The crystal structure of 1 3 H2O shows the presence of an intricate supramolecular structure resulting from detailed hydrogen-bonding interactions. The water molecules coordinated to the tin atom of the subunit 1A (Sn1) participate in strong intermolecular hydrogen-bonding interactions with those present on adjacent tin centers and the lattice water molecule as well as the first set of triflate ions (O10-O12) to form a two-dimensional sheet (Figures S6b and S7, Supporting Information). A closer look at this supramolecular sheet, formed by intermolecular hydrogen bonding among the [n-Bu2Sn(H2O)5]2þ motifs, reveals its resemblance to the supramolecular architecture found in [n-Bu2Sn(H2O)4][2,5Me2-C6H3SO3]2.8 As in the latter, in the current instance also each tin atom is surrounded by six neighboring tin atoms (Figure S8, Supporting Information). The subunits 1B are present above and below the supramolecular sheet of 1A and are connected to the latter through strong O-H 3 3 3 O contacts (O3 3 3 3 O6 = 2.700(4) A˚, O2 3 3 3 O6 = 2.681(4) A˚, O1 3 3 3 O6=3.053(2) A˚ (Table 2) that occur between the free oxygen atom (O6) of BPDO-II coordinated to the tin center (Sn2) of subunit 1B and water molecules (O1, O2, and O3)

sym 1.5 - x, 0.5 - y, 1 - z 1.5 - x, -0.5 þ y, 1.5 - z -x, y, 1.5 - z -x, y, 1.5 - z 1 þ x, y, z -1 þ x, y, z x, y, z 2 - x, y, 1.5 - z 0.5 - x, 0.5 þ y, 1.5 - z

Figure 2. ORTEP representation of the asymmetric unit of 2 with 30% probability displacement ellipsoids. Atoms Sn1 and Sn2 have an occupancy of 0.5. Hydrogen atoms have been omitted for the sake of clarity. Table 3. Selected Bond Parameters for 2 Sn1-C1 Sn1-O1 Sn1-O3

Bond Distances (A˚) 2.156(7) 2.237(4) 2.285(4)

C1-Sn1-C1 O1-Sn1-O1 O3-Sn1-O3 C1-Sn1-O1 C1-Sn1-O1* C1-Sn1-O3 C1-Sn1-O3* O1-Sn1-O3 O1-Sn1-O3*

Bond Angles (deg) 180.0(4) 180.0(1) 180.0(1) 94.2(2) 85.8(2) 84.9(2) 95.1(2) 89.68(16) 90.32(16)

Sn2-C5 Sn2-O2 Sn2-O4

2.114(5) 2.237(4) 2.258(5)

C5-Sn2-C5* 180.0(2) O2-Sn2-O2* 180.0(1) O4-Sn2-O4* 180.0(1) O2-Sn2-O4 93.77(19) O2-Sn2-O4* 86.23(18) C5-Sn2-O(2) 94.36(19) C5-Sn2-O2* 85.64(19) C5-Sn2-O4 86.6(2) C5-Sn2-O4* 93.4(2)

coordinated to the tin atom (Sn1) of subunit 1A (Figure S9, Supporting Information). Two adjacent units of 1B are further linked by O-H 3 3 3 O contacts that occur between water molecules (O4 and O4*) coordinated to Sn2 and another set of the triflate ions (O7-O9). As illustrated in Figure S9, subunits 1B act as pillars (parallel to the c axis), joining two consecutive sheets of 1A and leading to the

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Figure 3. Thermogravimetric curves for 1 3 H2O and 2.

formation of a 3D hydrogen-bonded architecture. Successive sheets of 1A contain regular voids (Figure S6c, Supporting Information) that eclipse each other. These serve as points of connection by 1B. The crystal structure of 2 reveals that it is a one-dimensional coordination polymer, the asymmetric unit of which contains a cationic part (comprising two crystallographically independent tin atoms Sn1 and Sn2 each with a structure occupancy factor of 0.5) (Figure 2) and two charge-balancing triflate anions. Each tin center possesses a 2C, 4O coordination. The trans angles found in 2 are clearly suggestive of a near-perfect octahedral geometry (Table 3). The backbone of this coordination polymer consists of diaqua diorganotin units bridged by linear BPDO-II ligands that are disposed trans with respect to each other (Figure S10 (Supporting Information), Table 3). The Sn-Ow distance of 2.258(5) A˚ found here is similar to that observed in 1B. Two adjacent polymeric chains are joined through hydrogen bonds between coordinated water molecules and triflate anions. These interactions result in twodimensional wavy sheets (Figures S10 and S11, Supporting Information) that are stacked together with the help of CH 3 3 3 O (2.571 A˚, 131.35(31)°) and π 3 3 3 π (3.673(1) A˚) interactions, eventually forming a three-dimensional supramolecular assembly (Figure S11, Supporting Information). For O 3 3 3 O bond distances involving the O-H 3 3 3 O hydrogen bonding interactions, as well as metric parameters defining C-H 3 3 3 O contacts, see Tables S1 and S2 of the Supporting Information. Thermogravimetric Analysis of 1 3 H2O and 2. Heating 1 3 H2O (9 °C/min) until 232 °C revealed an initial weight loss of ∼10%, corresponding to the removal of noncoordinated and coordinated water molecules (theoretical 9.0%), followed by loss of 54.4% until 500 °C (BPDO-II, 2n-Bu, 2CF3; theoretical 55.5%) (Figure 3a). The final char yield at ∼500 °C is 35.6%. The thermogravimetric curve of 2 (Figure 3b) illustrates a drop in weight percent (4.8%) on heating the sample until 242 °C (9 °C/min), which may be attributed to the loss of water molecules (theoretical 4.7%). This followed eventual loss of BPDO-II, two “n-butyl” groups, and two “trifluoromethyl” groups (58.6%, theoretical 58.2%). The final char yield at 460 °C is 36.5%.

Conclusion In summary, we have been able to structurally characterize an unprecedented pentahydrated diorganotin cation which

cocrystallizes in the form of a supramolecular adduct along with its coordination complex, affording the three-dimensional supramolecular assembly 1 3 H2O. In the latter, twodimensional sheets formed by intermolecular hydrogen bonding between different [n-Bu2Sn(H2O)5]2þ units are pillared by [n-Bu2Sn(H2O)2(BPDO-II)2]2þ as a result of further hydrogen-bonding interactions. The isolation of the coordination polymer 2 in the same reaction, albeit under different crystallization conditions, points out the possibility of 1 3 H2O being an intermediate en route to the formation of the former.

Experimental Section General Remarks. Solvents were distilled and dried prior to use according to standard procedures. [n-Bu2SnO]n, trifluoromethanesulfonic acid, and 4,40 -bipyridine (Aldrich) were purchased and used without any further purification. 4,40 Bipyridine N,N0 -dioxide (BPDO-II) was prepared according to the literature procedure reported for 2,20 -bipyridine N,N-dioxide.13 Melting points were measured using a JSGW melting point apparatus and are uncorrected. Elemental analyses were carried out using a Thermoquest CE instruments Model EA/110 CHNS-O elemental analyzer. Infrared spectra were recorded as KBr pellets on a FT-IR Bruker-Vector model. 1H and 119Sn NMR spectra were obtained on a JEOL-DELTA2 500 model spectrometer using CD3OD and (CD3)2SO solution with shifts referenced to tetramethylsilane (for 1H NMR) and tetramethyltin (for 119Sn NMR). 119Sn NMR spectra were recorded under broadband-decoupled conditions. ESI-MS spectra were recorded on a MICROMASS QUATTRO II triple-quadrupole mass spectrometer. The ionization mechanism used was electrospray in positive and negative ion full scan mode using 100% methanol as solvent and nitrogen gas for desolvation. The capillary voltage was maintained at 3 kV, and the cone voltage was kept at 30 V. Thermogravimetric analysis was carried out on a Perkin-Elmer Pyris 6 thermogravimetric analyzer. Synthesis of [{n-Bu2Sn(H2O)5}][CF3SO3]2 3 [{n-Bu2Sn(BPDO-II)2(H2O)2}][CF3SO3]2 3 H2O (1 3 H2O) and [{n-Bu2Sn(μ-BPDO-II)(H2O)2}{CF3SO3}2]n (2). To a suspension of [n-Bu2SnO]n (0.37 g, 1.5 mmol) in 15 mL of acetonitrile was added trifluoromethanesulfonic acid (0.26 mL, 3.0 mmol). The reaction mixture was stirred at room temperature for 10 h. A clear solution was obtained. To this was added 1 equiv of BPDO-II in 5 mL of methanol (0.32 g, 1.5 mmol). The reaction contents were further stirred for 30 h. The solution was filtered and evaporated (13) Simpson, P. G.; Vinciguerra, A.; Quagliano, J. V. Inorg. Chem. 1963, 2, 282.

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Organometallics, Vol. 28, No. 17, 2009

in vacuo to afford an oily residue. The residue was coevaporated twice with diethyl ether to obtain a creamy white solid (1a), soluble in methanol and dimethyl sulfoxide. 119Sn NMR (500 MHz, CD3OD): δ -353.7 (s). 119Sn NMR (500 MHz, (CD3)2SO): δ -391.9 (s). Crystallization of 1 3 H2O. Single crystals of 1 3 H2O were obtained from a slow (∼1 week) evaporation of a solution of 1a in methanol/diethyl ether at room temperature, in open air. Yield (recrystallized): 0.25 g (21%). Mp: 220 °C dec. Anal. Calcd for C40H68F12N4O24S4Sn2 (1584.1): C, 30.30; H, 4.33; N, 3.54. Found: C, 30.51; H, 4.60; N, 3.60. IR (KBr, cm-1): 3433 (br, ν(H2O)); 1173 (s, ν(SO3) asym str); 1037 (s, ν(SO3) sym str); 637 (m, ν(C-S) str); 3125 (m), 2959 (m), 1477 (m), 1260 (vs, b) 838 (s), 763 (w), 699 (w), 551 (m) (BPDO-II). 1H NMR (500 MHz, CD3OD): δ 0.85-0.89 (t, 6H, Me), 1.32-1.35 (m, 4H, SnCH2), 1.60 (b, 8H, CH2CH2), 8.13 (t, 4H, BPDO-II CH), 8.58 (t, 4H, BPDO-II CH). 119Sn NMR (500 MHz, CD3OD): δ -351.3 (s). ESI-MS under positive ionization mode (m/z (%) (100% methanol)): 1649.26 (0.2) [(n-Bu2Sn)2(BPDO-II)2(CF3SO3)4(MeOH)6(H2O) þ H]þ; 1635.26 [(nBu2Sn)2(BPDO-II)2(CF3SO3)4(MeOH)5(H2O)2 þ H]þ; 821.1465 (100) [{n-Bu2Sn}3(OMe)(OH)(O)(HCOO)]þ; 807.1340 (65.7) [{nBu2Sn}3(OMe)2(O)(HCOO)]þ, 631.03 (19.2) [{n-Bu2Sn}2(HCOO)(OH)2(MeOH)(H2O)]þ, 527.0796 (37.8) [{(n-Bu)2Sn}2(O)(HCOO)]þ, 467.101 (24.2) [BPDO-IIþ[(n-Bu)2Sn(HCOO)]þ, 381.0011 (14.6), 279.0256 (85) [n-Bu2Sn(HCOO)]þ, 189.0866 (43.8) [BPDO-II þ Hþ]þ. ESI-MS under negative ionization mode (m/z (%) (100% methanol)): 1576.9623 (3.08) [(BPDO-II)2(n-Bu2Sn)2(H2O)5(CF3SO3)4(MeOH)(OH)]-; 148.9458 (100) [CF3SO3]-; 343.983 (31.95) [(CF3SO3)2(HCOOH)]-; 486.9692 (8.12) [(CF3SO3H)(CF3SO3)(HCOOH)3(MeOH)(H2O)]-; 548.9492 (6.99) [(BPDO-II)(n-Bu2Sn)(HCOO)(OMe)(H2O)]; 566.9142 (5.69) [(n-Bu2Sn)2(O)(OMe)(OH)(HO)]-; 636.9268 (6.1) [BPDO-II þ (CF3SO3)3þ 2Hþ]-; 680.8956 (11.9) [(n-Bu2Sn)(CF3SO3)3]-; 928.9298 (23.75) [(n-Bu2Sn)2(O)(CF3SO3)3]-; 1194.9714 (86.73) [(CF3SO3)(BPDO-II)(n-Bu2Sn)3(O)(HCOO)(OH)(MeO)2(H2O) þ H]-; 1176.9656 (24.59) [(CF3SO3)(BPDO-II)(n-Bu2Sn)3(O)(HCOO)(OH)(MeO)2 þ H]-. Crystallization of 2. Slow (∼2 months) evaporation of a solution of 1a from a mixture of methanol/dimethylformamide, at room temperature, afforded crystals of 2. Yield (recrystallized): 0.55 g (46%). Mp: 246 °C dec. Anal. Calcd for C20H30F6N2O10S2Sn (756.03): C, 31.74; H, 4.00; N, 3.70. Found: C, 31.84; H, 4.09; N, 3.81. IR (KBr, cm-1): 3376 (br, ν(H2O)); 3125

Chandrasekhar and Singh (m), 2959 (s), 1470 (s), 1242 (vs, b), 838 (s), 757 (w), 699 (w), 548 (s) (BPDO-II); 1028 (s, ν(SO3) sym str); 1179 (s, ν(SO3) asym str), 639 (m, ν(C-S) str). 1H NMR (500 MHz, CD3OD): δ 0.94 (t, 6H, Me), 1.38-1.42 (m, 4H, SnCH2), 1.68 (b, 8H, CH2CH2), 8.21 (d, 4H, BPDO-II CH), 8.65 (d, 4H, BPDO-II CH). 119Sn NMR (500 MHz, CD3OD): δ -353.3(s). X-ray Crystallographic Study. The crystal data for compounds 1 3 H2O and 2 were collected on a Bruker SMART APEX CCD diffractometer. The SMART software package (version 5.628) was used for collecting data frames and the SAINT software package (version 6.45) for integration of the intensity and scaling, and SADABS was used for absorption correction. Details pertaining to the data collection and refinement for the crystals are as follows. For 1 3 H2O: size 0.2  0.2  0.2 mm3; monoclinic, C2/c; a=9.122(5) A˚, b=14.892(5) A˚, c=45.691(5) A˚; R=90.000(5)°, β=92.835(5)°, γ=90.000(5)°; V=6199(4) A˚3; T=100(2) K; Z=8; Dcalcd=1.696 Mg m-3; θ range 2.62-26.00°; 17 043 reflections collected; 6092 independent reflections (Rint=0.0432); R1=0.0433, wR2=0.1018 (for I > 2σ(I)); R1=0.0507, wR2=0.1069 (for all data); GOF= 1.028. For 2: size 0.2  0.2  0.2 mm3; triclinic; P1; a=9.814(5) A˚, b=10.619(5) A˚, c=15.246(5) A˚; R=103.273(5)°, β=95.276(5)°, γ= 98.804(5)°; V=1514.8(12) A˚3; T=293(2) K; Z=2; Dcalcd=1.656 Mg m-3; θ range 2.13-25.00°; 7813 reflections collected; 5254 independent reflections (Rint=0.0226); R1=0.0479, wR2=0.1342 (for I > 2σ(I)); R1=0.0618, wR2=0.1512 (for all data); GOF= 1.048. The structures were solved and refined by full-matrix least squares on F2 using the SHELXTL software package.14 Nonhydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms of coordinated and noncoordinated water molecules were located from the difference Fourier map, and their positions were refined isotropically. All other hydrogen atoms were included in idealized positions, and a riding model was used. In the case of 1 3 H2O the highest residual electron density is 1.54. This may be due to unresolved disorder of carbon atoms (C3 and C4) of one of the n-butyl chains. However, it does not affect the percentage convergence (99.8% at θ = 26°). Supporting Information Available: Figures giving mass spectral data and additional views of the crystal structures and tables giving additional crystal data. This material is available free of charge via the Internet at http://pubs.acs.org. (14) Sheldrick, G. M. SHELXTL version 6.14; Bruker AXS Inc., Madison, WI, 2003.