Reactions of 3,5-Pyrazoledicarboxylic Acid with Organotin Chlorides

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Organometallics 2009, 28, 2096–2106

Reactions of 3,5-Pyrazoledicarboxylic Acid with Organotin Chlorides and Oxides. Coordination Polymers Containing Organotin Macrocycles Vadapalli Chandrasekhar* and Ramalingam Thirumoorthi Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India ReceiVed December 11, 2008

The reaction of 3,5-pyrazoledicarboxylic acid (LH3) with di- and triorganotin substrates has been investigated. The reaction of LH3 with (PhCH2)2SnCl2 afforded a macrocycle-containing coordination polymer [{((PhCH2)2Sn)6(µ-L)4(µ-OH)2}{((PhCH2)2SnCl)2}]n (1), which upon reaction treatment with pyridine (py) in the presence of water yielded a coordination polymer [{((PhCH2)2Sn)6(µ-L)4(µOH)2(py)2}{((PhCH2)2Sn)2(µ-O)(µ-OH)}2]n (2). Treatment of 1 with 2,4,6-collidine in the presence of water afforded [{(PhCH2Sn)12(µ-O)14(µ-OH)6}{((PhCH2)2Sn)6(µ-L)4(µ-OH)2}] · 2C4H8O · 2C2H5OH · 2H2O (3). The latter contains a dodecanuclear oxotin cage as a dication and a hexanuclear tin macrocycle as the dianion. O-H ··· O hydrogen-bonding interaction between the cation and the anion leads to the formation of a supramolecular 2D polymer containing large macrocyclic voids. In a slight variation, if the reaction of LH3 is carried out with Me2SnCl2 in the presence of KOH, a heterobimetallic compound [{(K)2(H2O)2(µ-H2O)3(EtOH)2}{((CH3)2Sn)4(µ-L)3(µ-OH)}]n · 2H2O (4) is formed. An interesting aspect of the structure of 4 is that the two potassium atoms present in this compound are bridged to each other by three water molecules. 4 is a 2D-coordination polymer, which is taken into a 3D supramolecular structure by solvent ethanol molecules. The reactions of LH3 with Ph2SnO lead to the formation of an insolubleproduct5a,whichcouldbedissolvedinhotN,N′-dimethylformamidetoafford[{(CH3)2NH2}2{(Ph2Sn)(µL)(H2O)}2] (5). An analogue of 5, [{(CH3)2NH2}2{(Ph2Sn)(µ-L)(CH3OH)}2] (6), was also prepared more directly by crystallization of 5a in the presence of dimethylamine or bis(dimethylamino)methane. Both 5 and 6 are dinuclear, and their structural integrity is retained in solution as shown by ESI-MS studies. The reaction of (nBu3Sn)2O with LH3 leads to an unusual Sn-alkyl bond cleavage affording a 2Dcoordination polymer [(nBu2Sn)2(µ-L)2(nBu3Sn)2]n (8) where dinuclear tin macrocycles are linked to each other by nBu3Sn bridges. In contrast, the reaction of (Ph3Sn)2O with LH3 affords a dinuclear compound [(Ph3Sn)2(µ-LH)(H2O)] · (H2O)2 (9) where the two tin atoms are coordinated by only the carboxylate oxygen atoms. However, the interaction of the coordinated water molecule along with lattice water leads to the formation of a chair-shaped (H2O)6 cluster, which acts as a bridge between two successive molecules. Introduction There has been significant research interest in the area of organotin chemistry in recent years.1 The remarkable structural diversity of organostannoxanes has been one important reason for this interest.1-9 In addition, recently it has been shown that * To whom correspondence should be addressed. Phone: (+91) 512259-7259. Fax: (+91) 521-259-0007/7436. E-mail: [email protected]. (1) (a) Chandrasekhar, V.; Sasikumar, P.; Singh, P.; Thirumoorthi, R.; Senapati, T. J. Chem. Sci. 2008, 120, 105–113. (b) Chandrasekhar, V.; Gopal, K.; Thilagar, P. Acc. Chem. Res. 2007, 40, 420–434. (c) Chandrasekhar, V.; Nagendran, S.; Baskar, V. Coord. Chem. ReV. 2002, 235, 1–52. (d) Holmes, R. R. Acc. Chem. Res. 1989, 22, 190–197. (e) Nicholson, J. W. Coord. Chem. ReV. 1982, 47, 263–282. (2) (a) Chandrasekhar, V.; Thirumoorthi, R. Eur. J. Inorg. Chem. 2008, 4578–4585. (b) Chandrasekhar, V.; Thirumoorthi, R. Organometallics 2007, 26, 5415–5422. (c) Kumar, M. S.; Upreti, S.; Gupta, H. P.; Elias, A. J. J. Organomet. Chem. 2006, 691, 4708–4716. (d) Henn, M.; Schu¨rmann, M.; Mahieu, B.; Zanello, P.; Cinquantini, A.; Jurkschat, K. J. Organomet. Chem. 2006, 691, 1560–1572. (e) Boshra, R.; Sundararaman, A.; Zakharov, L. N.; Incarvito, C. D.; Rheingold, A. L.; Ja¨kle, F. Chem. -Eur. J. 2005, 11, 2810– 2824. (f) Chandrasekhar, V.; Gopal, K.; Nagendran, S.; Singh, P.; Steiner, A.; Zacchini, S.; Bickley, J. F. Chem.-Eur. J. 2005, 11, 5437–5448. (g) Chandrasekhar, V.; Nagendran, S.; Banzal, S.; Kozee, M. A.; Powell, D. R. Angew. Chem., Int. Ed. 2000, 39, 1833–1835. (3) (a) Amini, M. M.; Azadmeher, A.; Khavasi, H. R.; Ng, S. W. J. Organomet. Chem. 2007, 692, 3922–3930. (b) Chandrasekhar, V.; Thilagar, P.; Steiner, A.; Bickley, J. F. Chem.-Eur. J. 2006, 12, 8847–8861.

organostannoxanes can function as supports for anchoring electroactive,2 photoactive,3 or coordination platforms.4 The (4) (a) Yin, H.; Wang, H.; Wang, D. J. Organomet. Chem. 2008, 693, 585–589. (b) Hernańdez-Ahuactzi, I. F.; Cruz-Huerta, J.; Barba, V.; Ho¨pfl, H.; Zamudio-Rivera, L. S.; Beltrań, H. I. Eur. J. Inorg. Chem. 2008, 1200– 1204. (c) Shankar, R.; Singh, A. P.; Jain, A.; Mahon, M. F.; Molloy, K. C. Inorg. Chem. 2008, 47, 5930–5935. (d) Song, S.-Y.; Ma, J.-F.; Yang, J.; Gao, L.-L.; Su, Z.-M. Organometallics 2007, 26, 2125–2128. (e) Chandrasekhar, V.; Thilagar, P.; Senapati, T. Eur. J. Inorg. Chem. 2007, 1004– 1009. (f) Zhang, R.; Zhang, Q.; Yang, S.; Ma, C. J. Organomet. Chem. 2006, 691, 1668–1672. (5) Murugavel, R.; Shanmugan, S. Organometallics 2008, 27, 2784– 2788. (b) Xie, Y.-P.; Yang, J.; Ma, J.-F.; Zhang, L.-P.; Song, S.-Y.; Su, Z.-M. Chem.-Eur. J. 2008, 14, 4093–4103. (c) Delavaux-Nicot, B.; Kaeser, A.; Hahn, U.; Ge´gout, A.; Brandli, P.-E.; Duhayon, C.; Coppel, Y.; Saquet, A.; Nierengarten, J.-F. J. Mater. Chem. 2008, 18, 1547–1554. (d) Chandrasekhar, V.; Sasikumar, P.; Thilagar, P. Organometallics 2007, 26, 4386– 4388. (e) Song, S.-Y.; Ma, J.-F.; Yang, J.; Gao, L.-L.; Su, Z.-M. Organometallics 2007, 26, 2125–2128. (f) Ma, C.; Zhang, Q.; Zhang, R.; Wang, D. Chem.-Eur. J. 2006, 12, 420–428. (g) Xu, G.-H.; Ma, J.-F.; Yu, H.-X.; Li, S.-L.; Liu, Y.-Y.; Yang, J.; Su, Z.-M.; Shi, C.-F. Organometallics 2006, 25, 5996–6006. (h) Beckmann, J.; Costantino, F.; Dakternieks, D.; Duthie, A.; Lenco, A.; Midollini, S.; Mitchell, C.; Orlandini, A.; Sorace, L. Inorg. Chem. 2005, 44, 9416–9423. (6) (a) Garcia-Zarracino, R.; Ho¨pfl, H. J. Am. Chem. Soc. 2005, 127, 3120–3130. (b) Garcia-Zarracino, R.; Ho¨pfl, H. Angew. Chem., Int. Ed. 2004, 43, 1507–1511. (c) Garcia-Zarracino, R.; Ramos-Quioˇnes, J.; Ho¨pfl, H. Inorg. Chem. 2003, 42, 3835–3845.

10.1021/om8011739 CCC: $40.75  2009 American Chemical Society Publication on Web 03/03/2009

Reactions of 3,5-Pyrazoledicarboxylic Acid

Organometallics, Vol. 28, No. 7, 2009 2097

Figure 1. The dodecanuclear dicationic cage [(PhCH2Sn)12(µ-O)14(µ-OH)6] and the hexanuclear dianion of [((PhCH2)2Sn)6(µ-L)4(µ-OH)2] (3). Benzyl groups, hydrogen atoms of pyrazole, and solvent molecules are omitted for clarity.

utility of organotin compounds in catalysis has been another reason for provoking interest in these compounds.10 Although many types of organotin compounds are now known,5 macrocyclic compounds containing tin are relatively few.6-9 Höpfl and co-workers have utilized a variety of synthetic strategies to generate organotin macrocycles.4b,6 These include reactions of diorganotin substrates with dicarboxylic acids.6 More recently, this group has reported the use of dithiocarbamate ligands to build large macrocycles containing organotin motifs.7 Some of these have also been used for simultaneous recognition of anions and cations.7a In a different strategy, Ma and co-workers have reported a 60-membered organotin macrocycle in a reaction involving 1-(carboxyphenyl)-5-mercapto-1Htetrazole with trimethyltin chloride.8 In a preliminary communication, we have reported that the reaction of 3,5pyrazoledicarboxylic acid (LH3) with dibenzyltin dichloride in the presence of potassium hydroxide afforded a 2D coordination polymer 1 containing macrocyclic hexatin building blocks (Chart 1).9 The latter upon treatment with pyridine in the presence of water afforded the one-dimensional polymer 2 (Chart 2). We now report the full details of this work, which deals with the investigation of the reactions of 3,5-pyrazoledicarboxylic acid with various di- and triorganotin substrates.

Results and Discussion Conversion of [{((PhCH2)2Sn)6(µ-L)4(µ-OH)2}{((PhCH2)2SnCl)2}]n (1) into [{(PhCH2Sn)12(µ-O)14(µ-OH)6}{((PhCH2)2Sn)6(µ-L)4(µ-OH)2}] · 2C4H8O · 2C2H5OH · 2H2O (3). We have reported earlier that the treatment of the 2D coordination polymer 1 with pyridine in the presence of water causes the conversion of the former into a polymeric tape 2.9 In this process, the hexatin macrocycle framework is retained in the product, while the bridging (PhCH2)2SnCl units are transformed (7) (a) Cruz-Huerta, J.; Carillo-Morales, M.; Santacruz-Jua´rez, E.; Hernańdez-Ahuactzi, I. F.; Escalante-Garcıá, J.; Godoy-Alcantat, C.; Guerrero-Alvarez, J. A.; Ho¨pfl, H.; Morales-Rojas, H.; Sańchez, M. Inorg. Chem. 2008, 47, 9874–9885. (b) Santacruz-Jua´rez, E.; Cruz-Huerta, J.; Hernańdez-Ahuactzi, I. F.; Reyes-Martıńez, R.; Tlahuext, H.; Morales-Rojas, H.; Ho¨pfl, H. Inorg. Chem. 2008, 47, 9804–9812. (8) Ma, C.; Wang, Q.; Zhang, R. Inorg. Chem. 2008, 47, 7060–7061.

Chart 1

into a tetranuclear ladder motif {((PhCH2)2Sn)2(µ-O)(µ-OH)}2 (Chart 2).9 We wondered about the fate of the reaction under slightly more forcing conditions. Accordingly, we treated 1 with 2,4,6-collidine in the presence of water at 50 °C. Under these conditions, we were able to isolate [{(PhCH2Sn)12(µ-O)14(µOH)6}{((PhCH2)2Sn)6(µ-L)4(µ-OH)2}] · 2C4H8O · 2C2H5OH · 2H2O (3) where the hexatin macrocycle present in the coordination polymer 1 is severed as a dianion. 3 contains (9) Chandrasekhar, V.; Thirumoorthi, R.; Azhakar, R. Organometallics 2007, 26, 26–29. (10) (a) An, D. L.; Peng, Z.; Orita, A.; Kurita, A.; Man-e, S.; Ohkubo, K.; Li, X.; Fukuzumi, S.; Otera, J. Chem.-Eur. J. 2006, 12, 1642–1647. (b) Chandrasekhar, V.; Boomishankar, R.; Gopal, K.; Sasikumar, P.; Singh, P.; Steiner, A.; Zacchini, S. Eur. J. Inorg. Chem. 2006, 4129–4136. (c) Deshayes, G.; Poelmans, K.; Verbruggen, I.; Camacho-Camacho, C.; Degée, P.; Pinoie, V.; Martins, J. C.; Piotto, M.; Biesemans, M.; Willem, R.; Dubois, P. Chem.-Eur. J. 2005, 11, 4552–4561. (d) Herve, A.; Rodriguez, A. L.; Fouquet, E. J. Org. Chem. 2005, 70, 1953–1956. (e) Otera, J. Acc. Chem. Res. 2004, 37, 288–296. (f) Abrantes, M.; Valente, A. A.; Pillinger, M.; Goncalves, I. S.; Rocha, J.; Romão, C. C. Chem.-Eur. J. 2003, 9, 2685– 2695. (g) Storey, R. F.; Hoffman, D. C. Macromolecules 1992, 25, 5369– 5382.

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Chandrasekhar and Thirumoorthi

Figure 2. O-H · · · O hydrogen-bonded crystal packing of 3. Benzyl groups are omitted for clarity.

the dicationic dodecanuclear oxo-tin cage as the counter cation (Figure 1). Thus, 3 represents a remarkable composition of a macrocyclic dianion together with a nanosized dicationic cage. The latter is a well-known structural motif in organostannoxanes but is generally prepared in the reactions involving nBuSn(O)(OH) with arenesulfonic acids.11 The structural features of the hexanuclear dianion are similar to the motifs found in the 2D (1) or 1D (2) polymers prepared earlier by us9 and hence are not discussed here. Hydrogen-bonding interactions between the macrocycle dianion and the dodecanuclear dication (O10-H101 · · · O2 1.723 Å, O11-H102 · · · O7 2.286 Å) lead to the generation of a 2D supramolecular structure containing two distinct macrocyclic voids (A and B) (Figure 2). Both A and B are lined with two units each of the dianion and the dication. While the voids in A are occupied by solvent molecules (tetrahydrofuran, ethanol, and water), B is filled with protruding benzyl substituents on tin. Reactions of Me2SnCl2, Ph2SnO, and (R3Sn)2O (R ) nBu, Ph) with LH3. The reaction of dimethyltin dichloride with LH3 in an ethanol/water mixture in the presence of potassium hydroxide afforded the heterobimetallic coordination polymer [{(K) 2 (H 2 O) 2 (µ-H 2 O) 3 (EtOH) 2 }{((CH 3 ) 2 Sn) 4 (µ-L) 3 (µOH)}]n · 2H2O (4) (Scheme 1). To the best of our knowledge, 4

represents the first example of a heterobimetallic Sn-K organostannoxane. Ionic conductivity of 4 in methanol (164 S cm2 mol-1) indicates that it is a 1:1 electrolyte,12suggesting that the coordination polymer breaks down in solution and at least one potassium ion is separated. The 119Sn{1H} NMR spectrum of 4 in dimethylsulfoxide reveals the presence of signals at -269.7 and -294.0 ppm, indicating two distinct tin environments. ESIMS of 4 in methanol, under positive ion conditions, shows peaks at 544.8177 (69), which can be assigned to [(Me2Sn)2(O)L + 2K]+. Under negative ion conditions, the highest peak observed is at 768.8336 (100) and is due to [(Me2Sn)3L2(OH)]-. These studies reveal that while the entire structural motif found in the solid state is not retained in solution, prominent components of it are still preserved. The reaction of diphenyltin oxide with LH3 afforded a solid 5a, which could not be characterized due its insoluble nature. However, attempts to crystallize it by dissolving it in hot N,N′dimethylformamide (DMF) afforded [{(CH3)2NH2}2{(Ph2Sn)(µ-L)(H2O)}2] (5) (Scheme 2). The dimethylammonium counter (11) (a) Eychenne-Baron, C.; Ribot, F.; Steunou, N.; Sanchez, C.; Fayon, F.; Biesemans, M.; Martins, J. C.; Willem, R. Organometallics 2000, 19, 1940–1949. (b) Eychenne-Baron, C.; Ribot, F.; Sanchez, C. J. Organomet. Chem. 1998, 567, 137–142. (12) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81–122.



Figure 4. Repeating unit of [{(K)2(H2O)2(µ-H2O)3(EtOH)2}{((CH3)2Sn)4(µ-L)3(µ-OH)}]n · 2H2O (4). Methyl groups and solvent molecules are omitted for clarity. Chart 2

Figure 3. ESI-MS of 5. Scheme 1

cations present in 5 are generated from DMF.13 An analogue of 5, [{(CH3)2NH2}2{(Ph2Sn)(µ-L)(CH3OH)}2] (6), can be isolated more directly by crystallization of 5a in the presence (13) (a) Xu, Y.; Han, L.; Lin, Z.-Z.; Liu, C.-P.; Yuan, D.-Q.; Zhou, Y.-F.; Hong, M.-C. Eur. J. Inorg. Chem. 2004, 4457–4462. (b) Paulet, C.; Loiseau, T.; Fe´rey, G. J. Mater. Chem. 2000, 10, 1225–1229.

of dimethylamine or bis(dimethylamino)methane. The dinuclear structures of 5 and 6 observed in the solid state (vide infra) are retained in solution also. Thus, the ESI-MS studies on these compounds reveal peaks at 425.9662 (62) [(Ph2Sn)2L2]2 and 852.9622 (10) [(Ph2Sn)2L2+H]- (Figure 3). Solution conductivity studies of 5 and 6 (Experimental Section) reveal that it is a 1:2 electrolyte12 consistent with their chemical structures. The reaction of triorganotin oxide (nBu3Sn)2O with LH3 initially affords a dinuclear molecular compound [(nBu3Sn)2(LH)] (7). The latter was characterized by its ESI-MS (735.2385 [(Bu3Sn)2 + LH2]+) and 119Sn{1H} NMR (+113.4 (s)). However, attempts to crystallize this compound from ethanol at room temperature result in a facile Sn-C bond cleavage reaction to afford a coordination polymer [(nBu2Sn)2(µ-L)2(nBu3Sn)2]n (8) where dinuclear tin structural units containing diorganotin motifs are linked to each other by triorganotin units (Scheme 3). Although 8 could be characterized in the solid state, solution studies on this compound could not be done due to its insolubility. In contrast to the reaction of (nBu3Sn)2O, the reaction of (Ph3Sn)2O with LH3 gives a molecular dinuclear compound [(Ph3Sn)2(µ-LH)(H2O)] · (H2O)2 (9) (Scheme 4). 119Sn{1H} NMR of 9 shows a signal at -156.3 ppm, while its ESI-MS spectrum reveals peaks due to mono-, di-, and trinuclear species,


Chandrasekhar and Thirumoorthi Scheme 2

suggesting that in solution, several organotin species, in nearly similar chemical environments, are present. X-ray Crystal Structures of 3-6, 8, and 9. The solid-state structures of 3-6, 8, and 9 were determined by single-crystal X-ray analysis. The metric parameters for 3-6, 8, and 9 are given in the Supporting Information. In these compounds, seven different coordination modes are found for the deprotonated ligand [L]3- (Chart 3). An important difference in the coordination behavior of [L]3- vis-à-vis bis(pyrazolyl)acetate with reference to organotin substrates, is that the former is involved in a multiple coordination mode, which involves the two nitrogen atoms of the pyrazole ring along with the carboxylate oxygens. This cumulative coordination action from multiple sites results in the formation of tight structural units. In contrast, in organotin carboxylates containing bis(pyrazolyl)acetate, we have found that the pyrazole nitrogen atoms are not involved in coordination to tin.14 Compound 4 is a 2D coordination polymer containing a heterobimetallic (Sn/K) structural motif as its repeating unit (Figure 4). The latter contains four tin and two potassium atoms. Two of the four tin atoms (Sn1 and Sn1′) are linked to each other by the 3,5-pyrazoledicarboxylate ligand as well as a µ-OH. The central ditin motif thus generated is linked to two terminal (14) (a) Chandrasekhar, V.; Thilagar, P.; Sasikumar, P. J. Organomet. Chem. 2006, 691, 1681–1692. (b) Wen, Z.-K.; Song, H.-B.; Du, M.; Zhai, Y.-P.; Tang, L.-F. Appl. Organomet. Chem. 2005, 19, 1055–1059. (15) (a) Chen, Z.; Liang, F.; Tang, X.; Chen, M.; Song, L.; Hu, R. Z. Anorg. Allg. Chem. 2005, 631, 3092–3095. (b) Pan, L.; Frydel, T.; Sander, M. B.; Huang, X.; Li, J. Inorg. Chem. 2001, 40, 1271–1283.

tin atoms by the coordination action of [L]3- ligands (Scheme 1, Figure 4). The entire tetratin assembly is linked to two potassium atoms by the residual coordination action of the carboxylate part of [L]3- (Figure 4). Interestingly, the two potassium ions are bridged to each other by three water molecules. To the best of our knowledge, this is only the second example containing such a structural motif.15a The structural features of the hexanuclear heterobimetallic structural unit of 4 include the presence of several ring systems (labeled A-H, Scheme 1). The tin atoms Sn1 and Sn2 (Figure 4) are seven coordinate (2C, 2N, 3O) and have a pentagonal bipyramidal geometry (Supporting Information). The potassium atoms are eight coordinate (8O) in a distorted trigonal dodecahedron geometry (Supporting Information).15b The entire repeat unit (consisting of four tin atoms, two potassium atoms, as well as the pyrazoledicarboxylate ligands) is nearly planar except for the oxygen atoms of the coordinated water molecules, which deviate from this plane (Supporting Information). The repeat unit is extended into two dimensions as indicated in Scheme 1 and Figure 5, respectively. The general similarity of the structural units in 1, 2, and 4 is quite striking and is a consequence of the tight coordination mode of [L]3- as well as the presence of a Sn2(µ-OH) structural unit. Interestingly, the 2D coordinaton polymer 4 is taken into a 3D-supramolecular structure by solvent ethanol molecules. These occupy the macrocyclic voids present in 4 and extend the two-dimensional structure by further coordination interactions (Supporting Information).


Organometallics, Vol. 28, No. 7, 2009 2101 Scheme 3

Scheme 4

Chart 3. Coordination Modes of 3,5-Pyrazoledicarboxylate Found in 3-9a

a

The notation used is as per ref 21.

The crystal structures of 5 and 6 are similar (Figure 6). Because of this, only the structure of 5 is discussed. The structure of 5 contains a dianionic dinuclear tin unit. The two diorganotin atoms are attached to each other by a simultaneous coordination of two L3- ligands. This mode of coordination generates an unprecedented, central, six-membered Sn2N4 ring system and four peripheral SnNC2O five-membered rings. Tin

is seven-coordinate and is present in a pentagonal bipyramidal geometry (Supporting Information). The entire dianionic structural unit of 5 is nearly planar (Supporting Information). Hydrogen-bonding interactions between the dimethylammonium cations and distannate dianion lead to the formation of a twodimensional network. Large 32-membered voids present in this supramolecular architecture are occupied by DMF molecules



Figure 5. Supramolecular structure of 4. Methyl groups and hydrogen atoms of pyrazole are omitted for clarity. Space filling model of ethanol molecules is shown, which are hydrogen bonded with pyrazole carboxylate (O4-H14A 2.676 Å, O6-H14B 2.610 Å).

Figure 6. ORTEP diagrams of (a) 5 and (b) 6 shown at 50% thermal ellipsoid. Dimethylammonium ions, solvent molecules, and hydrogen atoms have been omitted for clarity.

in 5. The supramolecular structure of 6 involves hydrogen bonding between the dimethylammonium cations and the carboxylate oxygen atoms of the ligand (Supporting Information). The crystal structure of 8 reveals that it is a two-dimensional coordination polymer, where dinuclear tin motifs, whose structure is similar to that found in 5 and 6, are linked to each other in two dimensions by nBu3Sn units (Scheme 3, Figure 7). The bridging tin atoms are five coordinate in a trigonal bipyramidal geometry. The assembly of the coordination polymer is accompanied by the formation of 32-membered macrocyclic voids (Figure 7). The crystal structure of 9 reveals that two tin atoms are linked to each other by the [LH]2- ligand (the pyrazole part of the ligand does not participate in coordination). One of the tin atoms

is capped by a water molecule and is five coordinate (3C, 2O), while the other is present in a pseudo five-coordinate geometry (Scheme 4). An interesting hydrogen-bonding situation is found in 9. First, intermolecular N-H · · · O hydrogen bonding occurs between the free pyrazole N-H and the carboxylate oxygen (N1-H42 · · · O3 1.929 Å) (Figure 8). In addition, the water molecule that is involved in coordination to tin is engaged in hydrogen bonding with other solvent water molecules to generate a hexameric water cluster, which is present in a chairshaped conformation (Figure 9, Table 1). Although hexameric clusters are known in the literature,16 this is only the second instance that such clusters are found in the crystal lattice involving organotin compounds.17 In the present instance, the (H2O)6 clusters are involved in bridging successive molecules



Figure 7. 2D-coordination polymeric structure of 8. Butyl groups are omitted for clarity.

Figure 8. 1D polymeric structure of 9 showing the presence of hexameric water clusters that bridge two tin centers.

generating a linear polymeric tape. Such a structural role for a water cluster appears to be unprecedented.

Conclusions Organotin macrocycles containing coordination polymers are quite sparse because of the paucity of good synthetic methods to assemble them. 3,5-Pyrazoledicarboxylate ligand with its multiple interaction sites and coordination modes appears to be (16) (a) Siddiqui, K. A.; Mehrotra, G. K.; Mrozinski, J.; Butcher, R. J. Eur. J. Inorg. Chem. 2008, 4166–4172. (b) Rodrı´guez-Cuamatzi, P.; VargasDıáz, G.; Ho¨pfl, H. Angew. Chem., Int. Ed. 2004, 43, 3041–3044. (c) Ye, B.-H.; Ding, B.-B.; Weng, Y.-Q.; Chen, X.-M. Inorg. Chem. 2004, 43, 6866– 6868. (d) Ghosh, S. K.; Bharadwaj, P. K. Inorg. Chem. 2003, 42, 8250– 8254. (e) Moorthy, J. N.; Natarajan, R.; Venugopalan, P. Angew. Chem., Int. Ed. 2002, 41, 3417–3420. (f) Custecean, R.; Afloroaei, C.; Vlassa, M.; Polverejan, M. Angew. Chem., Int. Ed. 2000, 39, 3094–3096. (17) Luna-Garcıá, R.; Damiań-Murillo, B. M.; Barba, V.; Ho¨pfl, H.; Beltrań, H. I.; Zamudio-Rivera, L. S. Chem. Commun. 2005, 5527–5529.

extremely effective in mediating the formation of such assemblies. A key structural motif that can be recognized in the various assemblies of diorganotin compounds reported in this work is a ditin unit linked to each other by a κ2(N2) coordination of the pyrazole nitrogen atoms. Each tin is further coordinated by one oxygen atom each of the two carboxylate ligands present in the ligand. This cumulative coordination mode is present in compounds 1-6 and 8. Depending on the reaction conditions and the availability of other bridging ligands, such a ditin motif is further bridged by a µ-OH (1-4). The residual coordination capability of the carboxylate oxygen atoms enhances the ability of the ditin structural motif to be elaborated into a variety of structures such as those discussed in this work. In the case of triorganotin compounds where a Sn-C cleavage reaction does not occur, the pyrazole nitrogen atoms are not involved in coordination, and only the two carboxylate groups present on either end of [LH]2- assist in binding to tin. Although the



Figure 9. Expanded view of the hexameric chair-shaped water clusters in 9. Table 1. Bond Distance and Bond Angle Data for the Hydrogen Bonds Found in 9 D-H · · · A

d(D-H), Å D(H · · · A), Å D(D · · · A), Å ∠(DHA), deg

O1-H44 · · · O6 0.8793 (697) 1.8416 (685) O1-H43 · · · O7 0.6948 (559) 2.0527 (561) O6-H45 · · · O7 0.7786 (877) 2.1364 (864)

2.7138 (76) 2.7469 (52) 2.9138 (69)

171.104 (5631) 177.314 (6614) 176.148 (9252)

reactions of LH3 with monoorganotin substrates are anticipated to be more complex, we are currently investigating this system with a hope to discover new structural types.

Experimental Section Reagents and General Procedures. Solvents and other general reagents used in this work were purified according to standard procedures.18 Dimethyltin dichloride, diphenyltin oxide, bis(tributyltin) oxide, bis(triphenyltin) oxide, and 2,4,6-collidine were purchased from Aldrich and were used as such. Potassium hydroxide (RANKEM) was purchased from RFCL Limited, New Delhi, India, and was used as such. Dimethylamine was purchased from s.d. Fine. Chem. Ltd., Mumbai, India, and was purified by well-known procedures.18 Compound 1,9 3,5-pyrazoledicarboxylic acid,19a and bis(dimethylamino)methane19b were synthesized according to literature procedures. Instrumentation. Melting points were measured using a JSGW melting point apparatus and are uncorrected. Elemental analyses of the compounds were obtained using a Thermoquest CE instrument CHNS-O, EA/110 model. 1H and 119Sn NMR spectra were obtained on a JEOL-JNM Lambda model 400 spectrometer/JEOL DELTA2 500 model spectrometer operating at 400/500 (1H) and 149 MHz (119Sn), respectively. IR spectra were recorded from 4000 to 400 cm-1 on a Bruker FT-IR vector 22 model using KBr pellets. The chemical shifts were referenced with respect to tetramethylsilane (1H) and tetramethyltin (119Sn), respectively. ESI-MS analyses were performed on a Waters Micromass Quattro Micro triple quadrupole mass spectrometer. Electrospray ionization (positive and (18) Vogel, A. I. Vogel’s Textbook of Practical Organic Chemistry, 5th ed.; Longman: London, 1989. (19) (a) Lee, H. H.; Cain, B. F.; Denny, W. A.; Buckleton, J. S.; Clark, G. R. J. Org. Chem. 1989, 54, 428–431. (b) Baumgarten, H. E. Org. Synth. Coll. 1973, 5, 434. (20) (a) SMART & SAINT Software Reference manuals, Version 6.45; Bruker Analytical X-ray Systems, Inc.: Madison, WI, 2003. (b) Sheldrick, G. M. SADABS, a software for empirical absorption correction, Ver. 2.05; University of Go¨ttingen: Go¨ttingen, Germany, 2002. (c) SHELXTL Reference Manual, Ver. 6.1; Bruker Analytical X-ray Systems, Inc.: Madison, WI, 2000. (d) Sheldrick, G. M. SHELXTL Ver. 6.12; Bruker AXS Inc.: Madison, WI, 2001. (e) Bradenburg, K. Diamond, ver. 3.1d; Crystal Impact GbR: Bonn, Germany, 2006. (21) Coxall, R. A.; Harris, S. G.; Henderson, D. K.; Parsons, S.; Tasker, P. A.; Winpenny, R. E. P. J. Chem. Soc., Dalton Trans. 2000, 2349–2356.

negative ion, full scan mode) mass spectra were obtained for compounds 4-7, 9 (methanol) with cone voltage at 28-36 kV. Conductivity measurements were done on a Systronics conductivity meter model 304. Cell constants were obtained against a standard KCl (0.01 M) solution. Synthesis. [{(PhCH2Sn)12(µ-O)14(µ-OH)6}{((PhCH2)2Sn)6(µL)4(µ OH)2}] · 2C4H8O · 2C2H5OH · 2H2O (3). To a suspension of 0.1 g (32 µmol) of 1 and 25 mL of 98% methanol mixture was added collidine (8 mg, 66 µmol) dropwise. The reaction mixture was heated to 50 °C and was stirred for 2 h. After it was allowed to come to room temperature, the reaction mixture was filtered and the filtrate kept for slow evaporation. Block-shaped crystals of 3 were obtained, which were found to be unsuitable for X-ray crystallography. These were then ground, washed several times with diethylether and dichloromethane, dried, and redissolved in a mixture of hot tetrahydrofuran/ethanol/methanol(1:1:1). Slow crystallization resulted in the formation of needle-shaped crystals of 3. Yield: (0.009 g, 11%). Mp: >300 °C dec. Anal. Calcd for C200H212N8O44Sn18 (3): C, 43.14; H, 3.84; N, 2.01. Found: C, 42.98; H, 3.79; N, 1.96. IR (KBr,cm-1): 3360 (br), 3023 (sh), 2927 (sh), 1571 (s), 1498 (s), 1454 (sh), 1345 (w). [{(K) 2 (H 2 O) 2 (µ-H 2 O) 3 (EtOH) 2 }{((CH 3 ) 2 Sn) 4 (µ-L) 3 (µOH)}]n · 2H2O (4). To a mixture of ethanol/water (2:1) (30 mL) were added 3,5-pyrazoledicarboxylic acid (0.21 g, 1.21 mmol) and potassium hydroxide (0.21 g, 3.74 mmol). A clear solution was obtained when the solution was stirred for 10 min. Dimethyltin dichloride (0.27 g, 1.23 mmol) was now added all at once, and the reaction mixture was heated under reflux for 2 h. Cooling the solution to room temperature resulted in the crystallization of 4. Yield: (0.3 g, 71%). Mp: >300 °C dec. Anal. Calcd for C27H54K2N6O22Sn4 (4): C, 23.71; H, 3.98; N, 6.14. Found: C, 23.55; H, 3.89; N, 6.05. 1H NMR (500 MHz, C2D6SO, ppm): 0.38 (s, 12H, -CH3), 0.76 (s, 12H, -CH3), 6.56 (s, 2H, -CH(pz)), 6.74 (s, 1H, -CH(pz)). 119Sn NMR (149 MHz, C2D6SO, ppm): -269.7, -294.0 (s). ESI-MS: m/z (%) 466.8869 [(Me2Sn)2O(L)]- (20), 604.8937 [(Me2Sn)2L2 + H]- (31), 768.8336 [(Me2Sn)3OH(L)2](100). ESI-MS: m/z (%) 506.8632 [(Me2Sn)2OH(L) + K]+ (22), 544.8177 [(Me2Sn)2O(L) + 2K]+ (69). ΛM (CH3OH, 10-3 M): 105 S cm2 mol-1. [{(CH3)2NH2}2{(Ph2Sn)(µ-L)(H2O)}2] (5). Diphenyltin oxide (0.30 g, 1.04 mmol) and 3,5-pyrazoledicarboxylic acid (0.18 g, 1.03 mmol) were added to 75 mL of a toluene/methanol mixture (15:1) in a 100 mL round bottomed flask. The mixture was well stirred and then refluxed using a Dean-stark apparatus for 6 h. After being cooled, a precipitate 5a was obtained. This was washed with diethyl ether and subsequently dried in air. Yield: 0.39 g. 5a was taken in 50 mL of methanol, DMF (5 mL) was added at 50 °C, the mixture was cooled, filtered, and the filtrate was kept for slow evaporation to afford needle-shaped crystals of 5. Yield: (0.32 g, 55%). Mp: >300 °C dec. Anal. Calcd for C44H56N8O12Sn2 (5): C, 46.92; H, 5.01; N, 9.95. Found: C, 46.70; H, 4.94; N, 9.80. 1H NMR (400 MHz, CD3OD, ppm): 2.66 (s, 12H, -CH3), 7.02 (t, 4H, J ) 7.55 Hz, aromatic), 7.11-7.15 (m, 8H, aromatic), 7.31-7.33 (m, 8H, aromatic), 7.97 (s, 2H, pyrazolyl). ESI-MS: m/z (%) 425.9662 [(Ph2Sn)2L2]2- (62), 852.9622 [(Ph2Sn)2L2 + H]- (10). [{(CH3)2NH2}2{(Ph2Sn)(µ-L)(CH3OH)}2] (6). 0.39 g of 5a was suspended in 50 mL of methanol followed by dropwise addition of dimethylamine (0.05 g) or bis(dimethylamino)methane (0.1 g). This resulted in a clear solution, which was allowed to crystallize to afford block-shaped crystals of 6. Yield: (0.38 g, 73%). Mp: >300 °C dec. Anal. Calcd for C40H46N6O10Sn2 (6): C, 47.65; H, 4.60; N, 8.34. Found: C, 47.46; H, 4.56; N, 8.25. ΛM (CH3OH, 10-3 M): 164 S cm2 mol-1. [(nBu3Sn)2(LH)] (7) and [(nBu2Sn)2(µ-L)2(nBu3Sn)2]n (8). Bis(tri-n-butyltin) oxide (0.41 g, 0.69 mmol) and 3,5-pyrazoledicarboxylic acid (0.12 g, 0.69 mmol) were added to 80 mL of toluene


Organometallics, Vol. 28, No. 7, 2009 2105 Table 2. X-ray Crystallographic Data for 3-5

parameters empirical formula formula weight temperature [K] wavelength [ Å] crystal system space group a [Å] b [ Å] c [ Å] R [deg] β [deg] γ [deg] V [ Å3] Z crystal size [mm] Dcalcd [g cm-3] µ [mm-1] F(000) θ range [deg] limiting indices reflections collected independent reflections refinement method data/restraints/parameters GOF on F2 final R indices [I > 2σ(I)] R indices [all data]

3

4

5

C200H212N8O44Sn18 5568.20 100(2) 0.71069 monoclinic P2(1)/n 21.680(5) 16.662(5) 30.386(5) 90.00 104.570(5) 90.00 10623(4) 2 0.3 × 0.2 × 0.2 1.741 2.146 5440 2.92-25.03 -25 e h e 21, -19 e k e 16, -35 e l e 36 55 284 18 723 (Rint ) 0.0647) full-matrix least-squares on F2 18 723/1131/1211 1.069 R1 ) 0.0606, wR2 ) 0.1410 R1 ) 0.0824, wR2 ) 0.1515

C27H54K2N6O22Sn4 1367.72 100(2) 0.71073 orthorhombic Pnma 12.277(3) 22.523(5) 17.092(3) 90.00 90.00 90.00 4726.4(16) 4 0.2 × 0.2 × 0.2 1.922 2.346 2688 4.09-25.03 -14 e h e 14, -26 e k e 26, -20 e l e 14 23 673 4279 (Rint ) 0.0711) full-matrix least-squares on F2 4279/0/291 1.052 R1 ) 0.0410, wR2 ) 0.0947 R1 ) 0.0503, wR2 ) 0.0993

C44H56N8O12Sn2 1126.35 153(2) 0.71073 monoclinic P2(1)/n 9.4989(7) 16.8578(13) 15.0246(12) 90.00 108.004(2) 90.00 2288.1(3) 2 0.3 × 0.2 × 0.2 1.635 1.163 1144 3.02-25.02 -11 e h e 11, -20 e k e 19, 17 e l e 10 11 869 4016 (Rint ) 0.0459) full-matrix least-squares on F2 4016/2/310 1.054 R1 ) 0.0353, wR2 ) 0.0732 R1 ) 0.0451, wR2 ) 0.0763

Table 3. X-ray Crystallographic Data for 6, 8, and 9 parameters empirical formula formula weight temperature [K] wavelength [ Å] crystal system space group a [Å] b [ Å] c [ Å] R [deg] β [deg] γ [deg] V [ Å3] Z crystal size [mm] Dcalcd [g cm-3] µ [mm-1] F(000) θ range [deg] limiting indices reflections collected independent reflections refinement method data/restraints/parameters GOF on F2 final R indices [I > 2σ(I)] R indices [all data]

6

8

9

C40H46N6O10Sn2 1008.21 153(2) 0.71073 monoclinic P2(1)/c 9.1103(10) 12.3499(13) 18.287(2) 90.00 96.569(2) 90.00 2044.0(4) 2 0.2 × 0.2 × 0.2 1.638 1.287 1016 1.99-27.00 -10 e h e 11, -15 e k e 13, -23 e l e 22 12 329 4465 (Rint ) 0.0610) full-matrix least-squares on F2 4465/0/269 1.013 R1 ) 0.0422, wR2 ) 0.0811 R1 ) 0.0628, wR2 ) 0.0920

C25H46N2O4Sn2 676.02 153(2) 0.71073 monoclinic P2(1)/n 9.5940(6) 18.4331(12) 16.7185(10) 90.00 98.3810(10) 90.00 2925.0(3) 4 0.2 × 0.2 × 0.1 1.535 1.737 1368 2.21-26.00 -8 e h e 11, -22 e k e 22, -20 e l e 20 16 316 5726 (Rint ) 0.0388) full-matrix least-squares on F2 5726/0/301 1.050 R1 ) 0.0344, wR2 ) 0.0760 R1 ) 0.0477, wR2 ) 0.0845

C41H38N2O7Sn2 908.11 153(2) 0.71073 triclinic P1j 10.7938(10) 13.0634(12) 15.3001(14) 76.496(2) 70.7480(10) 72.021(2) 1916.3(3) 2 0.2 × 0.2 × 0.2 1.574 1.355 908 2.02-27.00 -11 e h e 13, -15 e k e 16, -19 e l e 18 11 420 8036 (Rint ) 0.0184) full-matrix least-squares on F2 8036/0/497 1.047 R1 ) 0.0417, wR2 ) 0.0978 R1 ) 0.0498, wR2 ) 0.1025

in a 100 mL round bottomed flask. This mixture was well stirred and then refluxed using a Dean-stark apparatus for 6 h. After being cooled, the solution was filtered and evaporated to afford an oil, which was identified as 7. 119 Sn NMR (149 MHz, CDCl3, ppm): +113.4 (s). ESI-MS: m/z (%) 291.1095 [Bu3Sn]+ (40), 597.2284 [(Bu3Sn)2OH]+ (11), 625.2087 [(Bu3Sn)2(HCOO)]+ (100), 735.2385 [(Bu3Sn)2LH2]+ (10), 1023.3308 [(Bu3Sn)3 + LH]+ (48), 1757.5811 [(Bu3Sn)5 + (LH)2]+ (9). 7 was dissolved in 50 mL of 98% ethanol, filtered, and the filtrate was kept for slow evaporation to afford block-shaped crystals of 8. Yield: (0.31 g, 67%). Mp: >300 °C dec. Anal. Calcd for C50H92N4O8Sn4 (8): C, 44.41; H, 6.86; N, 4.14. Found: C, 44.30; H, 6.82; N, 4.08. IR (KBr, cm-1): 2956 (s), 2924 (s), 2871 (sh), 2856 (sh), 1590 (br, s), 1363 (w), 1315(s), 1079 (sh), 836 (sh). [(Ph3Sn)2(µ-LH)(H2O)] · (H2O)2 (9). Bis(triphenyltin) oxide (0.21 g, 0.29 mmol) and 3,5-pyrazoledicarboxylic acid (0.05 g, 0.29

mmol) were added to 80 mL of toluene, heated under reflux for 30 min, cooled to room temperature, filtered, and the filtrate was evaporated to obtain an oil. An insoluble portion was recovered, which was dissolved in hot DMF and crystallized to afford 5 (0.05 g, 15%). The oil was dissolved in chloroform and then slowly evaporated to get block-shaped crystals of 9. Yield: (0.15 g, 56%). Mp: 224-225 °C. Anal. Calcd for C41H38N2O7Sn2 (9): C, 54.22; H, 4.22; N, 3.08. Found: C, 54.17; H, 4.16; N, 3.03. 1H NMR (400 MHz, CDCl3, ppm): 7.31 (s, 1H, pz), 7.36-7.40 (m, 18H, -CH(o and p)), 7.69-7.71 (m, 12H, -CH(m)). 119Sn NMR (149 MHz, CDCl3, ppm): -156.3 (s). ESIMS: m/z (%) 351.0106 [Ph3Sn]+ (100), 745.0231 [(Ph3Sn)2(HCOO)]+ (92), 855.0507 [(Ph3Sn)2LH2]+ (2), 1203.0631 [(Ph3Sn)3LH]+ (3). X-ray Crystallography. Important crystallographic data for compounds 3-6, 8, and 9 are given in Tables 2 and 3. Single

2106 Organometallics, Vol. 28, No. 7, 2009 crystals of 3-6, 8, and 9 suitable for X-ray crystallography were obtained by the slow evaporation from solutions of tetrahydrofuran/ ethanol/methanol (3), ethanol/water (4), DMF (5), methanol (6), ethanol (8), and chloroform (9). Data were collected on a CCD Bruker SMART APEX diffractometer using a Mo KR sealed tube. The program SMART20a was used for collecting frames of data, indexing reflection, and determining lattice parameters, SAINT20a for integration of the intensity of reflections and scaling, SADABS20b for absorption correction, and SHELXTL20c,d for space group and structure determination and least-squares refinements on F2. All non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were fixed in geometrically calculated positions using a riding model and were refined isotropically. The figures were created using Diamond 3.1d software.20e In the crystal structure of 3, the phenyl group (C89-C94) was positionally disordered over two positions. This could be refined with an occupancy of 50:50. Similarly, in compound 8, one of the

Chandrasekhar and Thirumoorthi butyl carbon atoms (C23) was disordered over two positions with occupancy of 80:20. We were unable to locate the hydrogen atoms for the water molecules found in compound 4.

Acknowledgment. V.C. is a Lalit Kapoor Professor of Chemistry. V.C. is thankful to the Department of Science and Technology for a J. C. Bose fellowship. R.T. thanks the Council of Scientific and Industrial Research, India, for a Senior Research Fellowship. We thank Dr. R. Azhakar and Mr. P. Sasikumar for their help in solving the crystal structures. Supporting Information Available: Tables of bond lengths and angles for compound 3-6, 8, and 9, and additional figures. This material is available free of charge via the Internet at http://pubs.acs.org. OM8011739

Reactions of 3,5-Pyrazoledicarboxylic Acid with Organotin Chlorides

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