Reactions of 3,5-Pyrazoledicarboxylic Acid with OrganotinChlorides 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 beeninvestigated. The reaction of LH3 with (PhCH2)2SnCl2 afforded a macrocycle-containing coordinationpolymer [{((PhCH2)2Sn)6(µ-L)4(µ-OH)2}{((PhCH2)2SnCl)2}]n (1), which upon reaction treatment withpyridine (py) in the presence of water yielded a coordination polymer [{((PhCH2)2Sn)6(µ-L)4(µ-OH)2(py)2}{((PhCH2)2Sn)2(µ-O)(µ-OH)}2]n (2). Treatment of 1 with 2,4,6-collidine in the presence ofwater 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 asthe dianion. O-H ··· O hydrogen-bonding interaction between the cation and the anion leads to theformation of a supramolecular 2D polymer containing large macrocyclic voids. In a slight variation, ifthe 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 aspectof the structure of 4 is that the two potassium atoms present in this compound are bridged to each otherby three water molecules. 4 is a 2D-coordination polymer, which is taken into a 3D supramolecularstructure by solvent ethanol molecules. The reactions of LH3 with Ph2SnO lead to the formation of aninsolubleproduct5a,whichcouldbedissolvedinhotN,N′-dimethylformamidetoafford[{(CH3)2NH2}2{(Ph2Sn)(µ-L)(H2O)}2] (5). An analogue of 5, [{(CH3)2NH2}2{(Ph2Sn)(µ-L)(CH3OH)}2] (6), was also prepared moredirectly by crystallization of 5a in the presence of dimethylamine or bis(dimethylamino)methane. Both5 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 2D-coordination polymer [(nBu2Sn)2(µ-L)2(nBu3Sn)2]n (8) where dinuclear tin macrocycles are linked to eachother 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 carboxylateoxygen atoms. However, the interaction of the coordinated water molecule along with lattice water leadsto 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 oforganotin chemistry in recent years.1 The remarkable structuraldiversity of organostannoxanes has been one important reasonfor this interest.1-9 In addition, recently it has been shown that

organostannoxanes can function as supports for anchoringelectroactive,2 photoactive,3 or coordination platforms.4 The

* To whom correspondence should be addressed. Phone: (+91) 512-259-7259. Fax: (+91) 521-259-0007/7436. E-mail: vc@iitk.ac.in.

(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) Chan-drasekhar, 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.; Schurmann, 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.; Jakle, 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.

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(4) (a) Yin, H.; Wang, H.; Wang, D. J. Organomet. Chem. 2008, 693,585–589. (b) Hernandez-Ahuactzi, I. F.; Cruz-Huerta, J.; Barba, V.; Hopfl,H.; Zamudio-Rivera, L. S.; Beltran, 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) Chan-drasekhar, 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.; Gegout, A.; Brandli, P.-E.; Duhayon, C.; Coppel, Y.; Saquet,A.; Nierengarten, J.-F. J. Mater. Chem. 2008, 18, 1547–1554. (d) Chan-drasekhar, 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. Organometallics2006, 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.

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Organometallics 2009, 28, 2096–21062096

10.1021/om8011739 CCC: $40.75 2009 American Chemical SocietyPublication on Web 03/03/2009

utility of organotin compounds in catalysis has been anotherreason for provoking interest in these compounds.10

Although many types of organotin compounds are nowknown,5 macrocyclic compounds containing tin are relativelyfew.6-9 Höpfl and co-workers have utilized a variety of syntheticstrategies to generate organotin macrocycles.4b,6 These includereactions of diorganotin substrates with dicarboxylic acids.6

More recently, this group has reported the use of dithiocarbamateligands to build large macrocycles containing organotin motifs.7

Some of these have also been used for simultaneous recognitionof anions and cations.7a In a different strategy, Ma andco-workers have reported a 60-membered organotin macrocyclein a reaction involving 1-(carboxyphenyl)-5-mercapto-1H-tetrazole with trimethyltin chloride.8 In a preliminary com-munication, we have reported that the reaction of 3,5-pyrazoledicarboxylic acid (LH3) with dibenzyltin dichloride inthe presence of potassium hydroxide afforded a 2D coordinationpolymer 1 containing macrocyclic hexatin building blocks (Chart1).9 The latter upon treatment with pyridine in the presence ofwater afforded the one-dimensional polymer 2 (Chart 2). Wenow report the full details of this work, which deals with theinvestigation of the reactions of 3,5-pyrazoledicarboxylic acidwith various di- and triorganotin substrates.

Results and Discussion

Conversionof[{((PhCH2)2Sn)6(µ-L)4(µ-OH)2}{((PhCH2)2-SnCl)2}]n (1) into [{(PhCH2Sn)12(µ-O)14(µ-OH)6}{((PhCH2)2-Sn)6(µ-L)4(µ-OH)2}] · 2C4H8O · 2C2H5OH · 2H2O (3). We havereported earlier that the treatment of the 2D coordinationpolymer 1 with pyridine in the presence of water causes theconversion of the former into a polymeric tape 2.9 In thisprocess, the hexatin macrocycle framework is retained in theproduct, while the bridging (PhCH2)2SnCl units are transformed

into a tetranuclear ladder motif {((PhCH2)2Sn)2(µ-O)(µ-OH)}2

(Chart 2).9 We wondered about the fate of the reaction underslightly more forcing conditions. Accordingly, we treated 1 with2,4,6-collidine in the presence of water at 50 °C. Under theseconditions, we were able to isolate [{(PhCH2Sn)12(µ-O)14(µ-OH)6}{((PhCH2)2Sn)6(µ-L)4(µ-OH)2}] · 2C4H8O · 2C2H5OH ·2H2O (3) where the hexatin macrocycle present in thecoordination polymer 1 is severed as a dianion. 3 contains

(7) (a) Cruz-Huerta, J.; Carillo-Morales, M.; Santacruz-Juarez, E.;Hernandez-Ahuactzi, I. F.; Escalante-Garcıa, J.; Godoy-Alcantat, C.;Guerrero-Alvarez, J. A.; Hopfl, H.; Morales-Rojas, H.; Sanchez, M. Inorg.Chem. 2008, 47, 9874–9885. (b) Santacruz-Juarez, E.; Cruz-Huerta, J.;Hernandez-Ahuactzi, I. F.; Reyes-Martınez, R.; Tlahuext, H.; Morales-Rojas,H.; Hopfl, H. Inorg. Chem. 2008, 47, 9804–9812.

(8) Ma, C.; Wang, Q.; Zhang, R. Inorg. Chem. 2008, 47, 7060–7061.

(9) Chandrasekhar, V.; Thirumoorthi, R.; Azhakar, R. Organometallics2007, 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.

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.

Chart 1

Reactions of 3,5-Pyrazoledicarboxylic Acid Organometallics, Vol. 28, No. 7, 2009 2097

the dicationic dodecanuclear oxo-tin cage as the countercation (Figure 1). Thus, 3 represents a remarkable composi-tion of a macrocyclic dianion together with a nanosizeddicationic cage. The latter is a well-known structural motifin organostannoxanes but is generally prepared in thereactions involving nBuSn(O)(OH) with arenesulfonic ac-ids.11 The structural features of the hexanuclear dianion aresimilar to the motifs found in the 2D (1) or 1D (2) polymersprepared earlier by us9 and hence are not discussed here.

Hydrogen-bonding interactions between the macrocycle di-anion and the dodecanuclear dication (O10-H101 · · · O2 1.723Å, O11-H102 · · · O7 2.286 Å) lead to the generation of a 2Dsupramolecular structure containing two distinct macrocyclicvoids (A and B) (Figure 2). Both A and B are lined with twounits each of the dianion and the dication. While the voids inA are occupied by solvent molecules (tetrahydrofuran, ethanol, andwater), 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 withLH3 in an ethanol/water mixture in the presence of potassiumhydroxide afforded the heterobimetallic coordination polymer[{(K)2(H2O)2(µ-H2O)3(EtOH)2}{((CH3)2Sn)4(µ-L)3(µ-OH)}]n · 2H2O (4) (Scheme 1). To the best of our knowledge, 4

represents the first example of a heterobimetallic Sn-K orga-nostannoxane.

Ionic conductivity of 4 in methanol (164 S cm2 mol-1)indicates that it is a 1:1 electrolyte,12suggesting that thecoordination polymer breaks down in solution and at least onepotassium ion is separated. The 119Sn{1H} NMR spectrum of 4in dimethylsulfoxide reveals the presence of signals at -269.7and -294.0 ppm, indicating two distinct tin environments. ESI-MS of 4 in methanol, under positive ion conditions, shows peaksat 544.8177 (69), which can be assigned to [(Me2Sn)2(O)L +2K]+. Under negative ion conditions, the highest peak observedis at 768.8336 (100) and is due to [(Me2Sn)3L2(OH)]-. Thesestudies reveal that while the entire structural motif found in thesolid state is not retained in solution, prominent components ofit are still preserved.

The reaction of diphenyltin oxide with LH3 afforded a solid5a, 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 2. O-H · · · O hydrogen-bonded crystal packing of 3. Benzyl groups are omitted for clarity.

2098 Organometallics, Vol. 28, No. 7, 2009 Chandrasekhar and Thirumoorthi

cations present in 5 are generated from DMF.13 An analogueof 5, [{(CH3)2NH2}2{(Ph2Sn)(µ-L)(CH3OH)}2] (6), can beisolated more directly by crystallization of 5a in the presence

of dimethylamine or bis(dimethylamino)methane. The dinuclearstructures of 5 and 6 observed in the solid state (vide infra) areretained in solution also. Thus, the ESI-MS studies on thesecompounds reveal peaks at 425.9662 (62) [(Ph2Sn)2L2]2 and852.9622 (10) [(Ph2Sn)2L2+H]- (Figure 3). Solution conductiv-ity studies of 5 and 6 (Experimental Section) reveal that it is a1:2 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)). How-ever, attempts to crystallize this compound from ethanol at roomtemperature result in a facile Sn-C bond cleavage reaction toafford a coordination polymer [(nBu2Sn)2(µ-L)2(nBu3Sn)2]n (8)where dinuclear tin structural units containing diorganotin motifsare linked to each other by triorganotin units (Scheme 3).Although 8 could be characterized in the solid state, solutionstudies on this compound could not be done due to itsinsolubility.

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} NMRof 9 shows a signal at -156.3 ppm, while its ESI-MS spectrumreveals peaks due to mono-, di-, and trinuclear species,

(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.; Ferey, G. J. Mater. Chem. 2000, 10, 1225–1229.

Figure 3. ESI-MS of 5.

Scheme 1

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 solventmolecules are omitted for clarity.

Chart 2

Reactions of 3,5-Pyrazoledicarboxylic Acid Organometallics, Vol. 28, No. 7, 2009 2099

suggesting that in solution, several organotin species, in nearlysimilar chemical environments, are present.

X-ray Crystal Structures of 3-6, 8, and 9. The solid-statestructures of 3-6, 8, and 9 were determined by single-crystalX-ray analysis. The metric parameters for 3-6, 8, and 9 aregiven in the Supporting Information. In these compounds, sevendifferent coordination modes are found for the deprotonatedligand [L]3- (Chart 3). An important difference in the coordina-tion behavior of [L]3- vis-à-vis bis(pyrazolyl)acetate withreference to organotin substrates, is that the former is involvedin a multiple coordination mode, which involves the twonitrogen atoms of the pyrazole ring along with the carboxylateoxygens. This cumulative coordination action from multiple sitesresults in the formation of tight structural units. In contrast, inorganotin carboxylates containing bis(pyrazolyl)acetate, we havefound that the pyrazole nitrogen atoms are not involved incoordination to tin.14

Compound 4 is a 2D coordination polymer containing aheterobimetallic (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 eachother by the 3,5-pyrazoledicarboxylate ligand as well as a µ-OH.The central ditin motif thus generated is linked to two terminal

tin atoms by the coordination action of [L]3- ligands (Scheme1, Figure 4). The entire tetratin assembly is linked to twopotassium atoms by the residual coordination action of thecarboxylate part of [L]3- (Figure 4). Interestingly, the twopotassium ions are bridged to each other by three watermolecules. To the best of our knowledge, this is only the secondexample containing such a structural motif.15a The structuralfeatures of the hexanuclear heterobimetallic structural unit of 4include the presence of several ring systems (labeled A-H,Scheme 1). The tin atoms Sn1 and Sn2 (Figure 4) are sevencoordinate (2C, 2N, 3O) and have a pentagonal bipyramidalgeometry (Supporting Information). The potassium atoms areeight coordinate (8O) in a distorted trigonal dodecahedrongeometry (Supporting Information).15b The entire repeat unit(consisting of four tin atoms, two potassium atoms, as well asthe pyrazoledicarboxylate ligands) is nearly planar except forthe oxygen atoms of the coordinated water molecules, whichdeviate from this plane (Supporting Information). The repeatunit is extended into two dimensions as indicated in Scheme 1and Figure 5, respectively. The general similarity of thestructural units in 1, 2, and 4 is quite striking and is aconsequence of the tight coordination mode of [L]3- as well asthe presence of a Sn2(µ-OH) structural unit. Interestingly, the2D coordinaton polymer 4 is taken into a 3D-supramolecularstructure by solvent ethanol molecules. These occupy themacrocyclic voids present in 4 and extend the two-dimensionalstructure by further coordination interactions (Supporting In-formation).

(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.

Scheme 2

2100 Organometallics, Vol. 28, No. 7, 2009 Chandrasekhar and Thirumoorthi

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

is seven-coordinate and is present in a pentagonal bipyramidalgeometry (Supporting Information). The entire dianionic struc-tural unit of 5 is nearly planar (Supporting Information).Hydrogen-bonding interactions between the dimethylammoniumcations and distannate dianion lead to the formation of a two-dimensional network. Large 32-membered voids present in thissupramolecular architecture are occupied by DMF molecules

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.

Reactions of 3,5-Pyrazoledicarboxylic Acid Organometallics, Vol. 28, No. 7, 2009 2101

in 5. The supramolecular structure of 6 involves hydrogenbonding between the dimethylammonium cations and thecarboxylate oxygen atoms of the ligand (Supporting Informa-tion).

The crystal structure of 8 reveals that it is a two-dimensionalcoordination polymer, where dinuclear tin motifs, whosestructure is similar to that found in 5 and 6, are linked to eachother in two dimensions by nBu3Sn units (Scheme 3, Figure7). The bridging tin atoms are five coordinate in a trigonalbipyramidal geometry. The assembly of the coordinationpolymer is accompanied by the formation of 32-memberedmacrocyclic voids (Figure 7).

The crystal structure of 9 reveals that two tin atoms are linkedto each other by the [LH]2- ligand (the pyrazole part of theligand 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 foundin 9. First, intermolecular N-H · · · O hydrogen bonding occursbetween the free pyrazole N-H and the carboxylate oxygen(N1-H42 · · · O3 1.929 Å) (Figure 8). In addition, the watermolecule that is involved in coordination to tin is engaged inhydrogen bonding with other solvent water molecules togenerate a hexameric water cluster, which is present in a chair-shaped conformation (Figure 9, Table 1). Although hexamericclusters are known in the literature,16 this is only the secondinstance that such clusters are found in the crystal latticeinvolving organotin compounds.17 In the present instance, the(H2O)6 clusters are involved in bridging successive molecules

Figure 5. Supramolecular structure of 4. Methyl groups and hydrogen atoms of pyrazole are omitted for clarity. Space filling model ofethanol 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 hydrogenatoms have been omitted for clarity.

2102 Organometallics, Vol. 28, No. 7, 2009 Chandrasekhar and Thirumoorthi

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

Conclusions

Organotin macrocycles containing coordination polymers arequite sparse because of the paucity of good synthetic methodsto assemble them. 3,5-Pyrazoledicarboxylate ligand with itsmultiple interaction sites and coordination modes appears to be

extremely effective in mediating the formation of such as-semblies. A key structural motif that can be recognized in thevarious assemblies of diorganotin compounds reported in thiswork is a ditin unit linked to each other by a κ2(N2) coordinationof the pyrazole nitrogen atoms. Each tin is further coordinatedby one oxygen atom each of the two carboxylate ligands presentin the ligand. This cumulative coordination mode is present incompounds 1-6 and 8. Depending on the reaction conditionsand the availability of other bridging ligands, such a ditin motifis further bridged by a µ-OH (1-4). The residual coordinationcapability of the carboxylate oxygen atoms enhances the abilityof the ditin structural motif to be elaborated into a variety ofstructures such as those discussed in this work. In the case oftriorganotin compounds where a Sn-C cleavage reaction doesnot occur, the pyrazole nitrogen atoms are not involved incoordination, and only the two carboxylate groups present oneither end of [LH]2- assist in binding to tin. Although the

(16) (a) Siddiqui, K. A.; Mehrotra, G. K.; Mrozinski, J.; Butcher, R. J.Eur. J. Inorg. Chem. 2008, 4166–4172. (b) Rodrıguez-Cuamatzi, P.; Vargas-Dıaz, G.; Hopfl, 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.

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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.

Reactions of 3,5-Pyrazoledicarboxylic Acid Organometallics, Vol. 28, No. 7, 2009 2103

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

Experimental Section

Reagents and General Procedures. Solvents and other generalreagents used in this work were purified according to standardprocedures.18 Dimethyltin dichloride, diphenyltin oxide, bis(tribu-tyltin) oxide, bis(triphenyltin) oxide, and 2,4,6-collidine werepurchased from Aldrich and were used as such. Potassiumhydroxide (RANKEM) was purchased from RFCL Limited, NewDelhi, India, and was used as such. Dimethylamine was purchasedfrom s.d. Fine. Chem. Ltd., Mumbai, India, and was purified bywell-known procedures.18 Compound 1,9 3,5-pyrazoledicarboxylicacid,19a and bis(dimethylamino)methane19b were synthesized ac-cording to literature procedures.

Instrumentation. Melting points were measured using a JSGWmelting point apparatus and are uncorrected. Elemental analysesof the compounds were obtained using a Thermoquest CE instru-ment CHNS-O, EA/110 model. 1H and 119Sn NMR spectra wereobtained on a JEOL-JNM Lambda model 400 spectrometer/JEOLDELTA2 500 model spectrometer operating at 400/500 (1H) and149 MHz (119Sn), respectively. IR spectra were recorded from 4000to 400 cm-1 on a Bruker FT-IR vector 22 model using KBr pellets.The chemical shifts were referenced with respect to tetramethyl-silane (1H) and tetramethyltin (119Sn), respectively. ESI-MS analyseswere performed on a Waters Micromass Quattro Micro triplequadrupole mass spectrometer. Electrospray ionization (positive and

negative ion, full scan mode) mass spectra were obtained forcompounds 4-7, 9 (methanol) with cone voltage at 28-36 kV.Conductivity measurements were done on a Systronics conductivitymeter model 304. Cell constants were obtained against a standardKCl (0.01 M) solution.

Synthesis. [{(PhCH2Sn)12(µ-O)14(µ-OH)6}{((PhCH2)2Sn)6(µ-L)4(µ OH)2}] · 2C4H8O · 2C2H5OH · 2H2O (3). To a suspension of0.1 g (32 µmol) of 1 and 25 mL of 98% methanol mixture wasadded collidine (8 mg, 66 µmol) dropwise. The reaction mixturewas heated to 50 °C and was stirred for 2 h. After it was allowedto come to room temperature, the reaction mixture was filtered andthe filtrate kept for slow evaporation. Block-shaped crystals of 3were obtained, which were found to be unsuitable for X-raycrystallography. These were then ground, washed several times withdiethylether and dichloromethane, dried, and redissolved in amixture of hot tetrahydrofuran/ethanol/methanol(1:1:1). Slow crys-tallization resulted in the formation of needle-shaped crystals of 3.

Yield: (0.009 g, 11%). Mp: >300 °C dec. Anal. Calcd forC200H212N8O44Sn18 (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(H2O)2(µ-H2O)3(EtOH)2}{((CH3)2Sn)4(µ-L)3(µ-OH)}]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) andpotassium hydroxide (0.21 g, 3.74 mmol). A clear solution wasobtained when the solution was stirred for 10 min. Dimethyltindichloride (0.27 g, 1.23 mmol) was now added all at once, and thereaction mixture was heated under reflux for 2 h. Cooling thesolution to room temperature resulted in the crystallization of 4.

Yield: (0.3 g, 71%). Mp: >300 °C dec. Anal. Calcd forC27H54K2N6O22Sn4 (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): 105S 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, 1.03mmol) were added to 75 mL of a toluene/methanol mixture (15:1)in a 100 mL round bottomed flask. The mixture was well stirredand then refluxed using a Dean-stark apparatus for 6 h. After beingcooled, a precipitate 5a was obtained. This was washed with diethylether and subsequently dried in air. Yield: 0.39 g. 5a was taken in50 mL of methanol, DMF (5 mL) was added at 50 °C, the mixturewas cooled, filtered, and the filtrate was kept for slow evaporationto afford needle-shaped crystals of 5.

Yield: (0.32 g, 55%). Mp: >300 °C dec. Anal. Calcd forC44H56N8O12Sn2 (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 wassuspended in 50 mL of methanol followed by dropwise additionof dimethylamine (0.05 g) or bis(dimethylamino)methane (0.1 g).This resulted in a clear solution, which was allowed to crystallizeto afford block-shaped crystals of 6.

Yield: (0.38 g, 73%). Mp: >300 °C dec. Anal. Calcd forC40H46N6O10Sn2 (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-pyrazoledi-carboxylic acid (0.12 g, 0.69 mmol) were added to 80 mL of toluene

(18) Vogel, A. I. Vogel’s Textbook of Practical Organic Chemistry, 5thed.; 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 Gottingen: Gottingen, Germany, 2002. (c) SHELXTL ReferenceManual, 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.

Figure 9. Expanded view of the hexameric chair-shaped waterclusters in 9.

Table 1. Bond Distance and Bond Angle Data for the HydrogenBonds 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) 2.7138 (76) 171.104 (5631)O1-H43 · · · O7 0.6948 (559) 2.0527 (561) 2.7469 (52) 177.314 (6614)O6-H45 · · · O7 0.7786 (877) 2.1364 (864) 2.9138 (69) 176.148 (9252)

2104 Organometallics, Vol. 28, No. 7, 2009 Chandrasekhar and Thirumoorthi

in a 100 mL round bottomed flask. This mixture was well stirredand then refluxed using a Dean-stark apparatus for 6 h. After beingcooled, the solution was filtered and evaporated to afford an oil,which was identified as 7.

119Sn 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-shapedcrystals of 8. Yield: (0.31 g, 67%). Mp: >300 °C dec. Anal. Calcdfor 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 30min, cooled to room temperature, filtered, and the filtrate wasevaporated to obtain an oil. An insoluble portion was recovered,which was dissolved in hot DMF and crystallized to afford 5 (0.05g, 15%). The oil was dissolved in chloroform and then slowlyevaporated to get block-shaped crystals of 9.

Yield: (0.15 g, 56%). Mp: 224-225 °C. Anal. Calcd forC41H38N2O7Sn2 (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). ESI-MS: 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 forcompounds 3-6, 8, and 9 are given in Tables 2 and 3. Single

Table 2. X-ray Crystallographic Data for 3-5

parameters 3 4 5

empirical formula C200H212N8O44Sn18 C27H54K2N6O22Sn4 C44H56N8O12Sn2

formula weight 5568.20 1367.72 1126.35temperature [K] 100(2) 100(2) 153(2)wavelength [ Å] 0.71069 0.71073 0.71073crystal system monoclinic orthorhombic monoclinicspace group P2(1)/n Pnma P2(1)/na [Å] 21.680(5) 12.277(3) 9.4989(7)b [ Å] 16.662(5) 22.523(5) 16.8578(13)c [ Å] 30.386(5) 17.092(3) 15.0246(12)R [deg] 90.00 90.00 90.00� [deg] 104.570(5) 90.00 108.004(2)γ [deg] 90.00 90.00 90.00V [ Å3] 10623(4) 4726.4(16) 2288.1(3)Z 2 4 2crystal size [mm] 0.3 × 0.2 × 0.2 0.2 × 0.2 × 0.2 0.3 × 0.2 × 0.2Dcalcd [g cm-3] 1.741 1.922 1.635µ [mm-1] 2.146 2.346 1.163F(000) 5440 2688 1144θ range [deg] 2.92-25.03 4.09-25.03 3.02-25.02limiting indices -25 e h e 21, -19 e k e 16,

-35 e l e 36-14 e h e 14, -26 e k e 26,-20 e l e 14

-11 e h e 11, -20 e k e 19,17 e l e 10

reflections collected 55 284 23 673 11 869independent reflections 18 723 (Rint ) 0.0647) 4279 (Rint ) 0.0711) 4016 (Rint ) 0.0459)refinement method full-matrix least-squares on F2 full-matrix least-squares on F2 full-matrix least-squares on F2

data/restraints/parameters 18 723/1131/1211 4279/0/291 4016/2/310GOF on F2 1.069 1.052 1.054final R indices [I > 2σ(I)] R1 ) 0.0606, wR2 ) 0.1410 R1 ) 0.0410, wR2 ) 0.0947 R1 ) 0.0353, wR2 ) 0.0732R indices [all data] R1 ) 0.0824, wR2 ) 0.1515 R1 ) 0.0503, wR2 ) 0.0993 R1 ) 0.0451, wR2 ) 0.0763

Table 3. X-ray Crystallographic Data for 6, 8, and 9

parameters 6 8 9

empirical formula C40H46N6O10Sn2 C25H46N2O4Sn2 C41H38N2O7Sn2

formula weight 1008.21 676.02 908.11temperature [K] 153(2) 153(2) 153(2)wavelength [ Å] 0.71073 0.71073 0.71073crystal system monoclinic monoclinic triclinicspace group P2(1)/c P2(1)/n P1ja [Å] 9.1103(10) 9.5940(6) 10.7938(10)b [ Å] 12.3499(13) 18.4331(12) 13.0634(12)c [ Å] 18.287(2) 16.7185(10) 15.3001(14)R [deg] 90.00 90.00 76.496(2)� [deg] 96.569(2) 98.3810(10) 70.7480(10)γ [deg] 90.00 90.00 72.021(2)V [ Å3] 2044.0(4) 2925.0(3) 1916.3(3)Z 2 4 2crystal size [mm] 0.2 × 0.2 × 0.2 0.2 × 0.2 × 0.1 0.2 × 0.2 × 0.2Dcalcd [g cm-3] 1.638 1.535 1.574µ [mm-1] 1.287 1.737 1.355F(000) 1016 1368 908θ range [deg] 1.99-27.00 2.21-26.00 2.02-27.00limiting indices -10 e h e 11, -15 e k e 13,

-23 e l e 22-8 e h e 11, -22 e k e 22,-20 e l e 20

-11 e h e 13, -15 e k e 16,-19 e l e 18

reflections collected 12 329 16 316 11 420independent reflections 4465 (Rint ) 0.0610) 5726 (Rint ) 0.0388) 8036 (Rint ) 0.0184)refinement method full-matrix least-squares on F2 full-matrix least-squares on F2 full-matrix least-squares on F2

data/restraints/parameters 4465/0/269 5726/0/301 8036/0/497GOF on F2 1.013 1.050 1.047final R indices [I > 2σ(I)] R1 ) 0.0422, wR2 ) 0.0811 R1 ) 0.0344, wR2 ) 0.0760 R1 ) 0.0417, wR2 ) 0.0978R indices [all data] R1 ) 0.0628, wR2 ) 0.0920 R1 ) 0.0477, wR2 ) 0.0845 R1 ) 0.0498, wR2 ) 0.1025

Reactions of 3,5-Pyrazoledicarboxylic Acid Organometallics, Vol. 28, No. 7, 2009 2105

crystals of 3-6, 8, and 9 suitable for X-ray crystallography wereobtained 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 CCDBruker 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 spacegroup and structure determination and least-squares refinements onF2. All non-hydrogen atoms were refined with anisotropic displace-ment parameters. Hydrogen atoms were fixed in geometricallycalculated positions using a riding model and were refined isotro-pically. The figures were created using Diamond 3.1d software.20e

In the crystal structure of 3, the phenyl group (C89-C94) waspositionally disordered over two positions. This could be refinedwith an occupancy of 50:50. Similarly, in compound 8, one of the

butyl carbon atoms (C23) was disordered over two positions withoccupancy of 80:20. We were unable to locate the hydrogen atomsfor the water molecules found in compound 4.

Acknowledgment. V.C. is a Lalit Kapoor Professor ofChemistry. V.C. is thankful to the Department of Scienceand Technology for a J. C. Bose fellowship. R.T. thanks theCouncil of Scientific and Industrial Research, India, for aSenior Research Fellowship. We thank Dr. R. Azhakar andMr. P. Sasikumar for their help in solving the crystalstructures.

Supporting Information Available: Tables of bond lengths andangles for compound 3-6, 8, and 9, and additional figures. Thismaterial isavailablefreeofchargevia theInternetathttp://pubs.acs.org.

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2106 Organometallics, Vol. 28, No. 7, 2009 Chandrasekhar and Thirumoorthi