Self-assembly of diorganotin(IV) oxides (R = Me, nBu, Ph) and 2,5-pyridinedicarboxylic acid to polymeric and trinuclear macrocyclic hybrids with porous solid-state structures: Influence of substituents and solvent on the supramolecular structure

Article abstract of DOI:10.1021/ja0437095

2,5-Pyridinedicarboxylic acid has been reacted with three different diorganotin(IV) oxides (R = Me, nBu, Ph) to study the molecular and supramolecular structures of the resulting diorganotin(IV) 2,5- pyridinedicarboxylates. It has been found that coordinating solvent molecules can change the supramolecular structure completely. The molecular structures found are either polymeric (zigzag) or cyclotrimeric; the supramolecular arrangements include (i) systems having only loosely bound discrete molecules (van der Waals contacts), (ii) systems having a 2D or 3D hydrogen-bonded structure, and (iii) systems having a 3D polymeric coordination structure. Channels or cavities are formed in several cases. For a particular case, evidence has been provided that molecular aggregation to capsules through hydrogen bonding interactions is possible in solution.

Full text of DOI:10.1021/ja0437095

Published on Web 02/11/2005
Self-Assembly of Diorganotin(IV) Oxides (R ) Me, nBu, Ph)
and 2,5-Pyridinedicarboxylic Acid to Polymeric and Trinuclear
Macrocyclic Hybrids with Porous Solid-State Structures:
Influence of Substituents and Solvent on the
Supramolecular Structure
Reyes Garc´ıa-Zarracino and Herbert Ho¨pfl*
Contribution from the Centro de InVestigaciones Qu´ımicas, UniVersidad Auto´noma del Estado
de Morelos, AVenida UniVersidad 1001, C.P. 62210 CuernaVaca, Mexico
Received October 15, 2004; E-mail: hhopfl@buzon.uaem.mx
Abstract: 2,5-Pyridinedicarboxylic acid has been reacted with three different diorganotin(IV) oxides (R )
Me, nBu, Ph) to study the molecular and supramolecular structures of the resulting diorganotin(IV) 2,5-
pyridinedicarboxylates. It has been found that coordinating solvent molecules can change the supramolecular
structure completely. The molecular structures found are either polymeric (zigzag) or cyclotrimeric; the
supramolecular arrangements include (i) systems having only loosely bound discrete molecules (van der
Waals contacts), (ii) systems having a 2D or 3D hydrogen-bonded structure, and (iii) systems having a 3D
polymeric coordination structure. Channels or cavities are formed in several cases. For a particular case,
evidence has been provided that molecular aggregation to capsules through hydrogen bonding interactions
is possible in solution.
and host-guest chemistry3 or polymeric structures with voids
or channels available for the inclusion of guest molecules.4
Among them, porous materials have received special interest,
since they may function as catalysts with applications similar
to those known for zeolithes.5
Although considerable advance has been reached in the
development of this branch of supramolecular chemistry, there
are still some fields that have received little attention thus far
by the scientific community working in this area. One of them
is that in comparison to systems with transition metals and
lanthanides, few supramolecular aggregates containing main
group elements are known;6,7 besides, few organometallic
species have been involved in self-assembly processes.6f,k,7a-e,i-k
Considering that (i) there is a series of organometallic com-
pounds that have enhanced thermal and kinetic stability,
including toward corrosive substances such as oxygen or water,
and that (ii) organometallic reagents can carry a huge variety
1. Introduction
During the past few years metal-directed self-assembly has
become a powerful tool for the construction of systems having
cavities or possessing intrinsic physical properties that are
promising for the creation of new materials.1 More recently,
metal-ligand binding has been combined with hydrogen
bonding, thus allowing for the construction of an almost infinite
number of new supramolecular entities.2
Supramolecular systems with cavities can have either discrete
structures that may be explored in terms of molecular recognition
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Langley, P. J.; Hulliger, J. Chem. Soc. ReV. 1999, 28, 279. (c) Hagrman,
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McGrady, J. E.; Mingos, D. M. P. Chem. Soc. ReV. 1995, 329. (b) Munakata,
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3120
J. AM. CHEM. SOC. 2005, 127, 3120-3130
10.1021/ja0437095 CCC: $30.25 © 2005 American Chemical Society

Influence of Substituents and Solvent on Structure
A R T I C L E S
Chart 1. Organotin Carboxylates Can Have Cyclooligomeric
of different organic substituents, new possibilities arise for the
construction of supramolecular systems, especially with respect
to the fine-tuning of their chemical, physical, and structural
properties.
Structures Formed through (a) CdO f Sn Intermolecular
Interactions or (b) Sn-O Covalent Bonds, of Which the Latter
Withstand Dissociation in Solution
Herein we report on the formation and characterization of a
series of organometallic tin complexes, which have been derived
from three different diorganotin(IV) groups, namely dimethyl-,
di-n-butyl-, and diphenyltin, using 2,5-pyridinedicarboxylate,
the anion of 2,5-pyridinedicarboxylic acid, as ligand. Although
it is well-known that the combination of di-, tri-, or tetracar-
boxylate ligands with transition and lanthanide metal ions can
lead to the formation of thermally very stable polymeric
materials, which in some cases possess a microporous structure,1m
2,5-pyridinedicarboxylate has been used for this purpose only
in very few occasions.8
A large number of organotin(IV) carboxylates has been
prepared and structurally characterized during the last few
decades, and it is known that tin centers are frequently
susceptible to intermolecular CdO f Sn interactions or solvent
coordination.9 Although intermolecular CdO f Sn interactions
can give rise to either polymeric or cyclooligomeric structures
in the solid state that may have cavities or pores (Chart 1a),7a-e
these interactions are too weak to withstand dissociation in
solution, even in the presence of only weakly coordinating
solvents.7b,d,e,10-11 However, solution-stable cyclooligomeric
diorganotin(IV) complexes with macrocyclic cavities have been
recently prepared using aromatic dicarboxylates as ligands.7k
These ligands were chosen because of two reasons: first,
carboxylate groups form strong covalent bonds with diorganotin-
(IV) moieties and second, the spatial separation of two car-
boxylate groups attached to the same aromatic ring induces the
formation of either a polymeric chain or a cyclooligomeric ring
structure (Chart 1b).7k
Chart 2. Reaction of Diorganotin(IV) Moieties with 2,5-Pyridine-
dicarboxylate Can Give Rise to Complexes Having (a) a Zigzag or
Helicoidal Polymeric Structure or (b) a Cyclooligomeric Structure
From previous reports it is known that the reaction of
diorganotin(IV) groups with 2-pyridinecarboxylate and its
derivatives gives complexes with coordinative N f Sn bonds
(6) For some macrocyclic or porous carboxylates containing main group
elements other than tin, see: (a) Robl, C.; Weiss, A. Z. Naturforsch. B
1986, 41, 1485. (b) Robl, C.; Weiss A. Z. Naturforsch. B 1986, 41, 1490.
(c) Lee, C. R.; Wang, C. C.; Wang, Y. Acta Crystallogr., Sect. B 1996, 52,
966. (d) Roma´n, P.; Miralles, C. G.; Luque, A. J. Chem. Soc., Dalton Trans.
1996, 3985. (e) Plater, M. J.; Roberts, A. J.; Marr, J.; Lachowski, E. E.;
Howie, R. A. J. Chem. Soc., Dalton Trans. 1998, 797. (f) Rettig, S. J.;
Storr, A.; Trotter, J. Can. J. Chem. 1999, 77, 434. (g) Lightfoot, P.;
Lethbridge, Z. A. D.; Morris, R. E.; Wragg, D. S.; Wright, P. A.; Kvick,
A.; Vaughan, G. B. M. J. Solid State Chem. 1999, 143, 74. (h) Chen, C.
Y.; Chu, P. P.; Lii, K. H. Chem. Commun. 1999, 1473. (i) Kedarnath, K.;
Choudhury, A.; Natarajan, S. J. Solid State Chem. 2000, 150, 324. (j) Hung,
L. C.; Kao, H. M.; Lii, K. H. Chem. Mater. 2000, 12, 2411. (k) Uhl, W.
Chem. Soc. ReV. 2000, 29, 259. (l) Choi, C. T. S.; Anokhina, E. V.; Day,
C. S.; Zhao, Y.; Taulelle, F.; Huguenard, C.; Gan, Z.; Lachgar, A. Chem.
Mater. 2002, 14, 4096. (m) Huang, Y. F.; Lii, K. H. J. Chem. Soc., Dalton
Trans. 1998, 4085.
(7) For macrocyclic or porous carboxylates containing tin, see: (a) Lockhart,
T. P. Organometallics 1988, 7, 1438. (b) Ng, S. W.; Das, V. G. K.; Pelizzi,
G.; Vitali, F. Heteroatom Chem. 1990, 1, 433. (c) Meunier-Piret, J.;
Boualam, M.; Willem, R.; Gielen M. Main Group Met. Chem. 1993, 16,
329. (d) Gielen, M.; Khloufi, A. E.; Biesemans, M.; Kayser, F.; Willem,
R. Organometallics 1994, 13, 2849. (e) Gajda-Schranz, K.; Nagy, L.;
Kuzmann, E.; Ve´rtes A.; Holecek, J.; Lycka, A. J. Chem. Soc., Dalton
Trans. 1997, 2201. (f) Natarajan, S.; Vaidhyanathan, R.; Rao, C. N. R.;
Ayyappan, S.; Cheetham, A. K. Chem. Mater. 1999, 11, 1633. (g) Salami,
T. O.; Zavilij, P. Y.; Oliver, S. R. J. Acta Crystallogr. 2001, E57, m111.
(h) Natarajan, S. J. Solid State Chem. 1998, 139, 200. (i) Ma, C.; Jiang,
Q.; Zhang, R.; Wang, D. J. Chem. Soc., Dalton Trans. 2003, 2975. (j) Ma,
C.; Jiang, Q.; Zhang, R. J. Organomet. Chem. 2003, 678, 148. (k) Garc´ıa-
Zarracino, R.; Ramos-Quin˜ones, J.; Ho¨pfl, H. Inorg. Chem. 2003, 42, 3835.
(8) Shiu, K.-B.; Chen, Z.-W.; Liao, F.-L.; Wang, S.-L. Acta Crystallogr., Sect.
E 2003, 59, m1072.
and five-membered C2NOSn chelate rings.11,12 From the reaction
of diorganotin(IV) moieties with 2,5-pyridinedicarboxylate,
complexes having a polymeric or a cyclooligomeric structure
may be expected (Chart 2).
Besides the conventional analysis of the molecular and
supramolecular structures as well as the host-guest chemistry
of the compounds described in what follows, this report
evaluates two additional parameters that are important for the
design of new supramolecular systems: (i) analysis of the
electronic and steric influence of the substituents attached to
the metal atoms, in this case organic groups, and (ii) evaluation
of the impact that solvent molecules can have on the structural
characteristics of supramolecular systems, especially if they are
(10) Wengrovius J. H.; Garbauskas, M. F. Organometallics 1992, 11, 1334.
(11) (a) Lockhart, T. P.; Davidson, F. Organometallics 1987, 6, 2471. (b)
Dakternieks, D.; Duthie, A.; Smyth, D. R.; Stapleton, C. P. D.; Tiekink, E.
R. T. Organometallics 2003, 22, 4599. (c) Ma, C.; Han, Y.; Zhang, R.;
Wang, D. J. Chem. Soc., Dalton Trans. 2004, 1832.
(12) (a) Aizawa, S.; Natsume, T.; Hatano, K.; Funahashi, S. Inorg. Chim. Acta
1996, 248, 215. (b) Huber, F.; Preut, H.; Hoffmann, E.; Gielen, M. Acta
Crystallogr. 1989, C45, 51. (c) Gielen, M.; Joosen, E.; Mancilla, T.;
Jurkschat, K.; Willem, R.; Roobol, C.; Bernheim, J.; Atassi, G.; Huber, F.;
Hoffmann, E.; Preut, H.; Mahieu, B. Main Group Met. Chem. 1987, 10,
147. (d) Ng, S. W.; Raj, S. S. S.; Razak, I. A.; Fun, H.-K. Main Group
Met. Chem. 2000, 23, 193.
(9) For reviews, see: (a) Tiekink, E. R. T. Appl. Organomet. Chem. 1991, 5,
1. (b) Chandrasekhar, V.; Nagendran, S.; Baskar, V. Coord. Chem. ReV.
2002, 235, 1.
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J. AM. CHEM. SOC. VOL. 127, NO. 9, 2005 3121

A R T I C L E S
Garc´ıa-Zarracino and Ho¨pfl
Table 1. Crystallographic Data for Compounds 1-H2O, 2-MeOH, 2-DMSO, 2-H2O/EtOH, and 3-DMSO
1-H2O
1-MeOHa
2-DMSO
2-H2O/PrOHa
3-DMSO
Crystal Datab
formula
C9H11NO5Sn,
EtOH
C45H63N3O12Sn3,
3 MeOH, H2O
0.23 × 0.11 × 0.08
1308.20
C51H81N3O15S3Sn3,
3 DMSO
0.11 × 0.11 × 0.21
1662.82
C45H69N3O15Sn3,
3 PrOH, 1.5 H2O
0.16 × 0.16 × 0.18
1455.41
C63H57N3O15S3Sn3,
5 DMSO
crystal size (mm3)
0.18 × 0.24 × 0.42
0.12 × 0.20 × 0.26
MW (g mol-1
)
377.95
1939.01
space group
P21/c
Cc
P63/m
I23
P1h
Cell Parameters
a (Å)
b (Å)
c (Å)
11.5608(11)
12.2314(12)
11.4007(11)
90
111.596(2)
90
1498.9(3)
4
1.724
26.594(4)
9.5792(14)
24.200(4)
90
114.730(3)
90
5599.6(14)
4
1.552
16.214(14)
16.214(14)
17.23(2)
90
90
120
3923(7)
2
1.167
1.408
25.1483(10)
25.1483(10)
25.1483(10)
90
90
90
15904.7(11)
8
0.991
17.878(3)
17.958(3)
18.053(3)
102.151(3)
104.815(4)
119.645(3)
4460.9(14)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
µ (mm-1
)
1.084
1.444
F
calcd (gcm-3
)
1.675
1.394
1.216
Data Collection
θ limits (deg)
hkl limits
2 < θ < 26
-14, 14; -15, 15;
-14, 14
2 < θ < 26
-25, 32; -11, 11;
-29, 26
2 < θ < 26
-20, 20; -20, 19;
-21, 21
2 < θ < 25.5
-30, 22; -27, 30;
-30, 30
2 < θ < 26
-22, 22; -22, 22;
-22, 22
No. collected reflns
No. indep. reflns (Rint
No. observed reflnsc
No. params
11452
14271
8077 (0.072)
6879
40873
40446
46940
)
2937 (0.033)
2644
183
2658 (0.099)
1762
181
4960 (0.071)
4859
215
17452 (0.117)
7604
862
384
Refinement
Rd
Rw
0.036
0.082
1.172
-0.60
1.10
0.075
0.151
1.086
-2.22
1.58
0.061
0.201
1.098
-0.91
1.51
0.092
0.228
1.280
-1.19
1.69
0.090
0.291
0.963
-0.75
1.11
e
GOF
∆Fmin (e Å-3
)
)
∆Fmax (e Å-3
a Data collection at 100 K. b Data collection on a Bruker Apex CCD diffractometer, T ) 293 K, Mo KR, monochromator: graphite. c Fo > 4σ(Fo). d R
2
2
2
2
2
2
) ∑(Fo - Fc )/∑Fo . e Rw ) [∑w(Fo - Fc )2/∑w(Fo )2]1/2
.
Chart 3. Molecular Structures of Compounds 1-3
tin atoms has been shown by X-ray diffraction studies, which
are discussed below. All three compounds have high melting
or decomposition points (>270 °C) and are stable in the air.
While compound 1 is not soluble, compounds 2-H2O and 3-H2O
are slightly soluble in polar solvents such as methanol, dimethyl
sulfoxide, dimethoxyethane, and pyridine; these coordinating
solvents can contribute to the dissociation of intermolecular
interactions such as hydrogen bonds and coordinative bonds and
can coordinate to the tin atoms (vide infra).
2.2. Structural Characterization in the Solid State. To
obtain information on the molecular structures of compounds
1-3, X-ray crystallographic studies have been performed that
have shown that in all cases the solid-state coordination number
of the tin atoms is seven. A total of six different crystal structures
have been determined for the three compounds, showing that
the heptacoordination is achieved either by the coordination of
solvent molecules such as DMSO or H2O to the tin atoms or
by intermolecular CdO f Sn coordination between neighboring
molecules.
coordinated to the metal centers. Part of the results described
herein have been published in a previous communication.13
2. Results and Discussion
2.1. Synthetic Procedures. The equimolar reaction of di-
methyltin(IV) oxide with 2,5-pyridinedicarboxylic acid in a 5:1
solvent mixture of toluene and ethanol gave, according to
elemental analysis, a complex with the composition [{Me2Sn-
(2,5-pdc)}n] (1; 2,5-pdc ) 2,5-pyridinedicarboxylate) in 76%
yield. Using di-n-butyltin and diphenyltin(IV) oxide instead of
dimethyltin oxide, we obtained complexes with the composition
[{R2Sn(2,5-pdc)(H2O)}3] (2-H2O; R ) nBu, 3-H2O; R ) Ph)
in yields of 76 and 81% (Chart 3). That these complexes are
cyclotrimeric and contain solvent molecules coordinated to the
Crystals of [{[Me2Sn(2,5-pdc)(H2O)]‚EtOH}n] (1-H2O) could
be grown by slow diffusion of a solution of potassium 2,5-
pyridinedicarboxylate in ethanol into a solution of dimethyltin
dichloride in a mixture of ethanol and water. The most relevant
crystallographic and selected geometric data for 1-H2O have
been summarized in Tables 1 and 2. A fragment of the polymeric
molecular structure of 1-H2O is shown in Figure 1a.
As in all cases to be discussed in what follows, the
coordination environment of the tin atoms is distorted bipyra-
midal-pentagonal, the axial positions being occupied by the
organic substituents and the equatorial positions being shared
(13) Garc´ıa-Zarracino, R.; Ho¨pfl, H. Angew. Chem., Int. Ed. 2004, 43, 1507.
9
3122 J. AM. CHEM. SOC. VOL. 127, NO. 9, 2005

Influence of Substituents and Solvent on Structure
A R T I C L E S
Table 2. Selected Bond Lengths (Å) and Bond Angles (degrees) for Compounds 1-H2O, 2-MeOH, 2-DMSO, 2-H2O/EtOH, and 3-DMSO
1-H2O
2-MeOHa
2-DMSO
2-H2O/PrOH
3-DMSOa
Bond Lengths
Bond Angles
Sn-O1
Sn-O3
Sn-O4
Sn-OD
Sn-N1
Sn-Cc
2.253(2)
2.375(3)
2.372(3)
2.266(3)
2.397(3)
2.095(4)
2.247(9)
2.335(10)
2.442(9)
2.261(9)
2.425(11)
2.125(13)
2.182(6)
2.349(7)
2.609(7)
2.236(7)
2.396(7)
2.135(12)
2.222(8)
2.284(8)
2.475(9)
2.291(8)
2.373(10)
2.138(15)
2.167(9)
2.296(9)
2.548(9)
2.197(8)
2.431(10)
2.148(9)
b
O1-Sn-O3
O1-Sn-N1
O1-Sn-OD
O3-Sn-O4
O3-Sn-OD
O3-Sn-N1
O4-Sn-N1
147.9(1)
70.0(1)
78.6(1)
54.9(1)
133.5(1)
77.9(1)
132.8(1)
148.4(1)
89.7(2)
90.2(2)
91.9(2)
91.3(2)
178.6(2)
158.0(3)
69.9(3)
81.1(3)
54.6(3)
77.6(3)
131.6(3)
77.4(3)
150.7(3)
89.8(5)
89.8(5)
89.1(4)
90.8(5)
175.0(5)
156.0(2)
72.3(2)
80.0(2)
52.5(3)
76.0(3)
131.7(2)
79.1(3)
152.3(3)
95.1(3)
85.6(3)
91.6(3)
90.9(3)
169.7(6)
153.3(3)
70.8(3)
77.4(3)
55.2(3)
76.1(3)
135.8(3)
80.8(3)
148.1(3)
92.6(6)
89.7(6)
88.9(5)
91.5(5)
175.7(7)
157.5(3)
70.9(3)
77.4(3)
54.4(3)
80.2(3)
131.5(3)
77.2(3)
148.1(3)
91.3(4)
89.3(4)
91.3(4)
89.5(4)
176.6(4)
d
d
OD-Sn-N1b
C-Sn-O1d
C-Sn-O3d
b,d
C-Sn-OD
C-Sn-N1d
C-Sn-C
a Mean values for all three tin atoms. b D ) donor atom from Lewis base coordinated to the tin atoms: H2O for 1-H2O; CdO2 for 2-MeOH; DMSO for
2-DMSO, 2-H2O/PrOH, and 3-DMSO. c Mean values for all Sn-C bonds. d Mean values for all analogous bond angles involving Sn-C bonds.
Figure 1. (a) Fragment of the polymeric structure of compound 1-H2O in the solid state. (b) Intermolecular hydrogen-bonding interactions in the crystal
lattice of 1-H2O give rise to 34-membered hexanuclear macrocycles.
by the coordinating atoms of the ligand as well as an additional
Lewis base, which may be a solvent molecule or an intermo-
lecular CdOfSn bond. Because of the chelate ring formation
the carboxylate group in position 2 is monodentate, while the
one in position 5 is anisobidentate, as is commonly observed
for diorganotin(IV) dicarboxylates.9
The polymeric molecules of 1-H2O have a zigzag structure
with 21 symmetry. In the crystal lattice, neighboring polymeric
chains are related to each other by inversion centers, and a 2D
hydrogen-bonded layer is generated. For the formation of this
supramolecular structure, the tin-coordinated water molecules
play a crucial role, since each of them participates in an
intermolecular hydrogen bond to the oxygen atom O1 of a five-
membered chelate ring (1.92 Å, 2.77 Å, 171°). This intercon-
nection gives rise to eight-membered hydrogen-bonded rings
of the composition Sn2O4H2 and 34-membered hexanuclear
supramolecular macrocycles (Figure 1b). The dimensions of the
cavities of these macrocycles can be described by the schematic
representation outlined in Chart 4a. They are filled with four
ethanol molecules, half of which are located above and half of
which are located below each 2D hydrogen bonded layer (see
Supporting Information). Each ethanol molecule is involved in
two hydrogen bonds, one with a tin-coordinated water molecule
(1.81 Å, 2.66 Å, 171°) and the other one with the uncoordinated
oxygen atom O2 of the carboxylate group in position 2 (1.94
9
J. AM. CHEM. SOC. VOL. 127, NO. 9, 2005 3123

A R T I C L E S
Garc´ıa-Zarracino and Ho¨pfl
Chart 4. Schematic Representations Showing the Dimensions of
the Cavities Found in the Crystal Structures of (a) 1-H2O, (b) 2-
MeOH, and (c) 2-H2O/PrOHa
Figure 2. If the solvent guest molecules (EtOH) are omitted in the crystal
structure of 1-H2O, channels are detected along axis c.
and selected geometric data are outlined in Tables 1 and 2. The
molecular structures for 2-MeOH, 2-DMSO, 3-DMSO, and
2-H2O/PrOH are shown in Figures 3-6. For clarity, in Figures
3, 4, and 6 the â, γ, and δ carbon atoms of the Sn-butyl groups
have been omitted. The molecular and crystal structure of
2-H2O/EtOH is very similar to that found for 2-H2O/PrOH and
has been described in a previous communication.13
In the crystal structures of 2-MeOH, 2-DMSO, 3-DMSO, and
2-H2O/PrOH trinuclear tin complexes are present, which are
characterized by an 18-membered C9N3O3Sn3 macrocyclic ring
containing three NfSn coordinative bonds. It should be noticed
that the overall macrocyclic structure is held together by covalent
Sn-O bonds, thus providing sufficient thermodynamic stability
for existence in solution (vide infra). The cavities of these
macrocyclic rings are hydrophobic, consisting of three oxygen
atoms and three pyridine-CH hydrogens (Chart 5). The
intraannular O‚‚‚O bond distances are 4.65-4.78, 4.58, 4.57-
4.65, and 4.63 Å for 2-MeOH, 2-DMSO, 3-DMSO, and 2-H2O/
PrOH, respectively; the corresponding Sn‚‚‚Sn distances are
8.31-8.51, 8.54, 8.50-8.57, and 8.37 Å. The hydrophobic
character of this cavity is enhanced by the organic groups
attached to the tin atoms, which are oriented almost perpen-
dicular to the pentagonal NO4 plane surrounding the tin atoms,
C-Sn-C ) 172.4(6)-176.6(6)° for 2-MeOH, 169.7(6)° for
2-DMSO, 173.2(4)-178.5(4)° for 3-DMSO, and 175.7(7)° for
2-H2O/PrOH. The distances between the C-H hydrogen atoms
and the neighboring oxygen atoms in the interior of the
macrocyclic cavity are significantly shorter than the sum of the
van der Waals radii of hydrogen and oxygen (2.70 Å), 2.39-
2.63 Å for 2-MeOH, 2.47-2.54 Å for 2-DMSO, 2.40-2.56 Å
for 3-DMSO, and 2.47-2.52 Å for 2-H2O/PrOH. Thus, an
interesting cyclic H3O3 system with a total of three bifurcated
hydrogen bridges is generated (Chart 5).
According to the X-ray crystallographic data, the trinuclear
molecular structures in 2-MeOH and 3-DMSO are asymmetric
(point group C1), while they possess crystallographic C3h point
group symmetry in 2-DMSO and 2-H2O/PrOH. The macrocycles
in 2-DMSO and 2-H2O/PrOH are perfectly planar, and those
in 3-DMSO are almost planar, having OCCC torsion angles
close to zero, -6.6(17) to +4(2)°. Only the macrocyclic
structure of 2-MeOH has a significant nonplanar conformation
(Figure 3b), with the carboxylate-pyridine torsion angles varying
from -20(2) to +13(2)°. Upon analyzing the molecular and
crystal structures with respect to the conformational variation
of the macrocyclic ring structures, we detected that the steric
bulk of the tin-coordinated Lewis base plays a significant role.
In contrast to 2-DMSO, 3-DMSO, and 2-H2O/PrOH, where
solvent molecules are coordinated to the tin atoms, in 2-MeOH
a In 2-H2O/PrOH, the trinuclear macrocycles are organized in form of a
truncated octahedron (for clarity, only one pair of macrocycles has been
marked).
Å, 2.74 Å, 167°). Since these hydrogen bonds are formed to
donor/acceptor atoms of two different 2D layers, an overall 3D
hydrogen-bonded network is resulting. If the ethanol molecules
are omitted, channels crossing the whole crystal lattice are
detected along axis c (Figure 2).
For compounds 2 and 3, three different types of supramo-
lecular structures have been identified. Crystals grown from a
solution of 2-H2O in methanol gave a polymeric coordination
network of the composition [{[(nBu)2Sn(2,5-pdc)]‚3MeOH‚
H2O}n] (2-MeOH), crystals grown from solutions of 2-H2O and
3-H2O in dimethyl sulfoxide gave crystal lattices containing
discrete molecules of the composition [{R2Sn(2,5-pdc)(DMSO)}3‚
nDMSO] (2-DMSO with R ) nBu, n ) 3 and 3-DMSO with
R ) Ph, n ) 5), and crystals grown from a solution of 2 in
solvent mixtures of EtOH/H2O and PrOH/H2O gave 3D
hydrogen-bonded networks of the composition [{[(nBu)2Sn(2,5-
pdc)(H2O)]3‚1.5H2O‚3ROH}n] (2-H2O/EtOH with R ) Et and
2-H2O/PrOH with R ) Pr). The most relevant crystallographic
9
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Influence of Substituents and Solvent on Structure
A R T I C L E S
Figure 3. (a) Top and (b) lateral view of the cyclotrimer found in the crystal structure of 2-MeOH; for clarity the somewhat disordered â, γ, and δ carbon
atoms of the Sn-butyl groups have been omitted. (c) Twelve-membered C3O6Sn3 heterocyclic rings formed through CdO f Sn interactions in 2-MeOH. (d)
Hydrogen-bonded helices containing methanol and water molecules in a proportion of 3:1 are found in the channels of 2-MeOH.
Figure 4. (a) Molecular structure of compound 2-DMSO; for clarity the somewhat disordered â, γ, and δ carbon atoms of the Sn-butyl groups have been
omitted. (b) Space-filling model of the crystal lattice showing the channels found for 2-DMSO.
intermolecular CdOfSn interactions are occurring between
neighboring macrocycles, Sn-O ) 2.213(9)-2.329(9) Å.
Because of the conformational distortion caused by this
coordination (Figure 3b), a 3D coordination polymer has been
formed.
Besides the already described C9N3O3Sn3 macrocycles, one
further type of heterocyclic ring is present in the crystal lattice
of 2-MeOH (Figure 3c). Each of these 12-membered C3O6Sn3
heterocycles is surrounded by three 18-membered C9O3N3Sn3
macrocycles and vice versa. The cavities of the two heterocycles
have diameters of 0.5 and 2.3 Å and are schematically described
in Chart 4b. The crystal lattice of this 3D polymer possesses
channels corresponding to 19.5% of the total volume,14 in which
hydrogen-bonded helices of uncoordinated solvent molecules
are located. Interestingly, these helices contain simultaneously
methanol and water molecules in a proportion of 3:1 (Figure
3d). Such mixed hydrogen-bonded systems are almost unknown
thus far and are interesting from a biochemical point of view.15
In 2-DMSO (Figure 4), 3-DMSO (Figure 5), and 2-H2O/PrOH
(Figure 6), solvent molecules (DMSO and H2O) are strongly
coordinated to the tin atoms, Sn-O ) 2.236(7) Å for 2-DMSO,
(14) PLATON, version 210103. Spek, A. L. Acta Crystallogr. 1990, A46, C-34.
(15) Cheruzel, L. E.; Pometun, M. S.; Cecil, M. R.; Mashuta, M. S.; Wittebort,
R. J.; Buchanan, R. M. Angew. Chem., Int. Ed. 2003, 42, 5452.
9
J. AM. CHEM. SOC. VOL. 127, NO. 9, 2005 3125

A R T I C L E S
Garc´ıa-Zarracino and Ho¨pfl
Figure 5. Molecular structure of compound 3-DMSO. (a) ORTEP type presentation. (b) Space-filling model.
Figure 6. (a) Molecular structure of compound 2-H2O/PrOH; for clarity the somewhat disordered â, γ, and δ carbon atoms of the Sn-butyl groups have
been omitted. (b) The unit cell of 2-H2O/PrOH viewed along the [111] direction showing one of the capsules present in the crystal lattice; nBu groups and
uncoordinated solvent molecules have been omitted for clarity.
Chart 5. Schematic Representation of the Cyclic
the macrocyclic rings are organized in a hexagonal packing
mode along axis c, so that porous channels are formed
throughout the crystal lattice (Figure 4b). The diameter of the
Hydrogen-Bonding System Present in the Macrocyclic Cavities of
2-MeOH, 2-DMSO, 3-DMSO, and 2H2O/PrOH
channels is determined by the diameter of the cyclotrimeric
molecules; however, there are larger voids (180 Å3) in the space
between them,14 which are occupied by solvent molecules. Such
cavities exist also in 3-DMSO.
As for 2-H2O/EtOH,13 the crystal lattice of 2-H2O/PrOH
consists of a chiral, highly symmetrical 3D hybrid network
containing trinuclear complex molecules (Figure 6a), in which
each tin atom is strongly coordinated by one water molecule,
Sn-O ) 2.291(8) Å. The macrocycles are arranged such that
large spherical cavities are formed (Figure 6b) whose centers
are located at the 0,0,0 and /2, /2, /2 positions in the cubic
unit cell (space group I23). These capsules are formed through
C-H‚‚‚O and O-H‚‚‚O hydrogen-bonding interactions between
eight of the cyclotrimeric molecules and have diameters of
nanodimensions (∼3.5 nm).16 Each capsule consists of 24 nBu2-
Sn units and 24 ligand molecules, giving a total of 48 starting
components, which are held together by covalent coordination
bonds to form eight cyclotrimeric units of the composition
[{(nBu)2Sn(2,5-pdc)(H2O)}3] and a total of 36 hydrogen bonds
1
1
1
2.190(9)-2.207(7) Å for 3-DMSO, and 2.291(8) Å for 2-H2O/
PrOH. Interestingly, the coordinative OfSn bonds formed with
the solvent molecules are equal in length or shorter than the
covalent Sn-O bonds formed with the carboxylate groups in
position 5, 2.349(7) T 2.236(7) Å for 2-DMSO, 2.283(8)-
2.305(9) T 2.190(9)-2.207(7) Å for 3-DMSO and 2.284(8)
T 2.291(8) Å for 2-H2O/PrOH. The only intermolecular
interactions found in the crystal lattices of 2-DMSO and
3-DMSO are van der Waals contacts. In the case of 2-DMSO,
9
3126 J. AM. CHEM. SOC. VOL. 127, NO. 9, 2005

Influence of Substituents and Solvent on Structure
A R T I C L E S
Table 3. Selected Chemical 1H (400 MHz) and 119Sn (149 MHz) NMR Chemical Shifts of 2,5-Pyridindedicarboxylic Acid,
[{nBu2Sn(2,5-pdc)(solv)}3] (2) and [{Ph2Sn(2,5-pdc)(solv)}3] (3)
H3
H4
H6
H
R
/H-o
H
â/H-m
H
γ/H-p
H
δ
119Sn
−NMR
Ligand
-
DMSO-d6
8.13 (dd)
8.41 (dd)
9.14 (dd)
-
-
-
-
Compound 2
1.31 (m)
DMSO-d6
methanol-d4
pyridine-d5
8.38 (d)
8.53 (d)
8.87 (d)
8.81 (dd)
9.01 (dd)
9.16 (d)
9.71 (dd)
9.83 (d)
10.80 (s)
1.28 (m)
1.27 (m)
1.42 (m)
1.08 (m)
1.17 (m)
1.04 (m)
0.62 (t)
0.68 (t)
0.53 (t)
-444
-412
-426
1.52 (m)
1.84 (m)
Compound 3
DMSO-d6
8.45 (d)
8.92 (dd)
9.72 (s)
7.40 (m)
7.17 (m)
7.17 (m)
-
-554
to form the sphere. The eight trinuclear molecules of each
capsule occupy the hexagonal faces of a truncated octahedron,
in which the centers of two opposite faces are separated by a
distance of 21.8 Å (Chart 4c). In comparison to 2-H2O/EtOH,
a volume increase of 1.3% is observed, indicating that the
hydrogen-bonding network allows for some expansion in the
presence of more voluminous alcohol molecules.
It should be noticed that these spherical supramolecular
arrangements are not isolated capsules, unlike for fullerenes,
but share faces with eight neighboring aggregates. Thus, the
overall crystal structure can be described as a 3D network built
up from the 3D union of truncated octahedra sharing all of their
eight hexagonal faces with neighboring polyhedra. Each tri-
nuclear complex () each hexagonal face of the truncated
octahedron) is involved in a total of 24 hydrogen bonds, of
which 18 are required for the formation of the 3D network and
six are used for connections to three propanol and three water
molecules (O‚‚‚O ) 2.71-2.81 Å, C-H‚‚‚O ) 2.56-2.72 Å),
which strengthen the union between the capsules in the 3D
hybrid structure.
Because of the 3D arrangement described above, half of the
48 butyl groups of one capsule are oriented into its interior,
while the other half contributes to the filling of another eight
neighboring capsules. Although in each capsule 24 butyl groups
are oriented into the interior of the cavity, large voids that have
a volume of 1940 Å3 14 still remain in the center; cavities with
such a large volume are very rare.17 This space is filled most
probably by disordered water molecules, since only smears of
electron density could be detected. It should be mentioned that
this is the only type of void present in the crystal structure and
that their combined volumes form 24% of the crystal lattice
volume. For 2-H2O/EtOH, it has been shown that this void can
be occupied by hydrophobic guest molecules such as diphen-
ylmethane (2.5 molecules in average), triphenylmethane (1.5
molecules), triptycene (3 molecules), and sodium tetraphenylbo-
rate (1 molecule).13
2.3. Structural Characterization in Solution. Since com-
pounds 2-H2O and 3-H2O were slightly soluble (3-H2O only in
DMSO), NMR spectroscopic and mass spectrometric analyses
could be carried out to obtain some information on their
solution-state structures. The existence of the cyclotrimeric
molecules could be shown by FAB+ mass spectrometric studies.
In both cases, it could be evidenced that the tin-coordinated
water molecules can dissociate in solution, since no peaks for
solvent-coordinated species were detected. For 2, peaks corre-
sponding to the molecular ion of a trinuclear complex and the
ion formed through loss of a nBu group have been detected at
m/z ) 1194.22 and m/z ) 1136.15, respectively. For 3, the
analogous peaks appear at m/z ) 1314.02 and m/z ) 1235.96.
Interestingly, in the mass spectrum of 2, but not in the one of
3, there are also peaks of minor intensity for a tetranuclear and
pentanuclear species, however, with a much smaller intensity
than for the trinuclear complex. The most probable explanation
is that fragments of the initially trinuclear complex have
recombined to higher nuclear species having the zigzag structure
outlined in Chart 2 and found in the solid state for 1-H2O.
Previous 1H and 119Sn NMR studies on diorganotin dipicoli-
nates have shown that NfSn coordinative bonds that are
involved in five-membered quelate rings resist dissociation in
solution.11 With respect to the coordination of Lewis bases to
the tin atoms in this type of complexes, it is known that
coordinating solvent molecules interact with the tin atoms in
rapid exchange equilibria.11 As expected, this is also the case
1
for compounds 2 and 3 as shown by their H, 13C, and 119Sn
NMR spectra. Since these spectra have been recorded in a
coordinating solvent (DMSO-d6) it can be expected that the
water molecules, which are coordinated to the tin atoms in the
initially prepared complexes (vide supra), are displaced by
DMSO molecules.
In the 1H NMR spectra, all three signals of the central,
disubstituted pyridine rings are shifted to lower fields in com-
parison to the ligand: ∆δ ) 0.25/0.32 ppm for H3, ∆δ ) 0.40/
0.51 ppm for H4, and ∆δ ) 0.57/0.58 ppm for H6, whereby it
should be noticed that the chemical shift is largest for the
hydrogen atom in the R-position to the pyridine nitrogen H6
(Table 3). In the 13C NMR spectra recorded in pyridine-d5 for
2 and DMSO-d6 for 3, the signal of the C4 carbon atom in para
orientation to the nitrogen atom is significantly downfield shift-
ed: ∆δ ) 4.6 ppm for 2 and ∆δ ) 4.0 ppm for 3 (Table 4).
Both data give evidence for the existence of the NfSn bond.
The coordination numbers of the tin atoms in compounds 2
and 3 can be derived from their 119Sn NMR spectra.18 According
to the spectra measured in DMSO-d6, the coordination number
is seven in both cases, δ ) -444 ppm for 2, and δ ) -554
ppm for 3 (Table 3),19 thus proving (i) the existence of the
NfSn bond and the presence of the C2NOSn chelate ring, (ii)
an anisobidentate coordination mode of the carboxylate group
in position 5 of the pyridine ring, and (iii) the coordination of
one solvent molecule to each tin atom. In any other case the
(18) Wrackmeyer, B. Annu. Rep. NMR Spectrosc. 1985, 16, 73.
(19) The shift differences observed for the di-n-butyltin and diphenyltin species
are due to the different electronic properties of the substituents, and similar
differences have been observed for other diorganotin(IV) complexes. The
chemical shift displacements between nBu2SnCl2 (δ ) 122 ppm) and Ph2-
SnCl2 (δ ) -32 ppm) can be taken as reference to evaluate the influence
of the n-butyl and phenyl groups on the 119Sn NMR shift displacements:
Smith, P. J.; Tupciauskas, A. P. Annu. Rep. NMR Spectrosc. 1978, 8, 291.
(16) For details, see ref 13 and Supporting Information.
(17) For reviews, see: (a) MacGillivray, L. R.; Atwood, J. L. Angew. Chem.
Int. Ed. 1999, 38, 1018. (b) Hof, F.; Craig, S. L.; Nuckolls, C.; Rebek, J.,
Jr. Angew. Chem., Int. Ed. 2002, 41, 1489.
9
J. AM. CHEM. SOC. VOL. 127, NO. 9, 2005 3127

A R T I C L E S
Garc´ıa-Zarracino and Ho¨pfl
Figure 7. Cold electrospray mass spectrum showing the existence of the hydrogen-bonded capsule [{nBu2Sn(2,5-pdc)(H2O)}3]8 in solution (CH2Cl2-
MeOH, 2:1).
Table 4. Selected Chemical 13C (100 MHz, DMSO-d6) NMR
Chemical Shifts of 2,5-Pyridindedicarboxylic Acid,
[nBu2Sn(2,5-C6H4(COO)2)]3 (2) and [Ph2Sn(2,5-C6H4(COO)2)]3 (3)
H6. In methanol-d4 (δ ) -412 ppm) and pyridine-d5 (δ ) -426
ppm), the signals in the 119Sn NMR spectra of 2 are low-field
shifted when compared to the spectra recorded in DMSO-d6 (δ
) -444 ppm), thus indicating a somewhat weaker coordination
of these solvents to the tin atoms.
ligand
complex 2a
complex 3
C-2
C-3
C-4
C-5
C-6
C-7
C-8
C-R/C-i
C-â/C-o
C-γ/C-m
C-δ/C-p
151.4
124.4
138.3
129.0
149.9
165.5
165.5
-
152.6
126.0
143.6
133.6
149.3
166.2
172.9
34.4
150.8
125.3
143.3
131.2
147.3
163.9
171.7
150.1
133.1
128.2
128.4
Interestingly, when the 1H NMR spectrum of compound
2-H2O was recorded in CDCl3, two signals with a proportion
of 1:1 were observed instead of one for each hydrogen atom of
the pyridine ring and each methylene/methyl group of the
diorganotin moieties. At first sight one might suppose that the
interchange of the tin-coordinated water molecules is slower in
this less polar solvent, thus giving signals for [{nBu2Sn(2,5-
pdc)}3] and [{nBu2Sn(2,5-pdc)(H2O)}3]; however, a closer
analysis of the structures determined by X-ray crystallography
reveals that the presence or absence of tin-coordinated water
molecules would hardly affect the methyl groups of the nBu2-
Sn moieties. The formation of intermolecular CdOfSn interac-
tions can also be excluded on the basis of previous reports on
diorganotin dipicolinates, which have shown that these bonds
are too weak to withstand dissociation in solution, even in
unpolar solvents such as chloroform.11
-
28.2
26.6
13.8
-
-
a Data in pyridine-d5.
coordination number would be less than seven. For the related
monomeric [Me2Sn(picolinate)2] complex, a 119Sn NMR chemi-
cal shift of δ ) -451 ppm has been reported (in DMSO-d6)
and solvent coordination to the tin atoms has been proved.11a
The signals in the 119Sn NMR spectra of 2 and 3 are broad,
confirming that the solvent molecules interact with the tin atoms
in rapid exchange equilibria. The difference in the coordination
mode of the two carboxylate groups present in the ligand
(anisobidentate versus monodentate coordination mode) is
confirmed by the fact that the 13C NMR shifts of the corre-
sponding signals are quite different from each other. While in
comparison to the ligand there is only a slight shift difference
for the carboxylate moieties in position 2, ∆δ ) 0.7 ppm for 2
and ∆δ ) -1.6 ppm for 3, the shifts are more significant for
the carboxylate groups in position 5, ∆δ ) 7.4 ppm for 2 and
∆δ ) 6.2 ppm for 3, indicating a stronger anisobidentate
interaction with the diorganotin(IV) group.
For the more soluble complex 2-H2O, the 1H and 119Sn NMR
spectra have been also measured in pyridine-d5 and methanol-
d4 to determine solvent-induced changes. Both pyridine and
methanol are also coordinating solvents so that a concentration-
induced substitution of the water molecules by these solvent
molecules can be expected. As can be seen from Table 3, the
magnetic shielding in the 1H NMR spectrum is decreased
significantly in the presence of pyridine, especially for hydrogen
The X-ray crystallographic studies have shown that eight
cyclotrimeric molecules with the composition [{nBu2Sn(2,5-
pdc)(H2O)}3] can associate to capsules through hydrogen-
bonding interactions (Figure 6b). One could expect that the
hydrogen-bonding interactions found in these aggregates do not
withstand dissociation in solution; however, in this case each
trimeric molecule participates in nine hydrogen bonds at a time,
so that a significant cooperative factor can be expected. A mass
spectrometric study using the cold electrospray technique proved
the existence of [{nBu2Sn(2,5-pdc)(H2O)}3]8 in solution. From
the mass spectrum shown in Figure 7, it can be seen that in
solution species are present that have molecular weights
corresponding to aggregates resulting form a step-by-step
association/dissociation of the capsule. Therefore, it is important
to note that the peak corresponding to the entire capsule has a
local maximum intensity.
The existence of the capsule structure can be corroborated
1
further by the following arguments concerning the H NMR
data: (i) Two different signals are observed for each hydrogen
9
3128 J. AM. CHEM. SOC. VOL. 127, NO. 9, 2005

Influence of Substituents and Solvent on Structure
A R T I C L E S
1
Figure 8. Variable temperature H NMR experiment of the hydrogen-bonded capsule [{nBu2Sn(2,5-pdc)(H2O)}3]8 in solution (CDCl3).
atom of the pyridine ring, since the cyclotrimeric molecules
participate alternately in two different hydrogen patterns; half
of the molecules act as 6-fold C-H‚‚‚O and 3-fold O-H‚‚‚O
donors, and the second half act as 6-fold C-H‚‚‚O and 3-fold
O-H‚‚‚O acceptors (Figure 6b). (ii) The n-butyl groups attached
to the tin atoms are in two different coordination environments;
half is directed to the interior of the capsule and the other half
is directed to the exterior, which explains the observation of
signals with different chemical shifts for the n-butyl hydrogen
atoms, especially for the methyl groups (∆δ ≈ 0.2 ppm). A
variable temperature 1H NMR experiment showed furthermore
that there is a dynamic equilibrium occurring in solution (Figure
8), indicating a continuous exchange of cyclotrimeric molecules
(coalescence of the signals for the methyl groups) and probably
also a fluctuation of the whole hydrogen-bonding system
(coalescence of the signals of the pyridine hydrogens).
to arrangements with cavities large enough for the inclusion of
guest molecules, whereby the size can be varied significantly.
1H NMR and cold electrospray mass spectrometric studies
proved that spherical aggregates formed through hydrogen-
bonding interactions can exist in unpolar solvents, but are
involved in dynamic processes.
In the case of the supramolecular structure with spherical
cavities, it should be possible to modulate the diameter of the
voids, varying the size of the organic substituents in the
diorganotin groups. These compounds could then be further
exploited for the selective trapping of labile reactive species
and for conducting chemical reactions by using the cavities as
reaction vessels.
4. Experimental Section
Instrumental. NMR studies were carried out with a Varian Inova
1
400 instrument. Standards were TMS (internal, H, 13C) and SnMe4
(external, 119Sn). Chemical shifts are stated in parts per million; they
are positive when the signal is shifted to higher frequencies than the
standard. COSY and HETCOR experiments have been carried out to
assign the 1H and 13C spectra completely. IR spectra have been recorded
on a Bruker Vector 22 FT spectrophotometer. The FAB mass spectra
of 2 and 3 were obtained on a Kratos Concept IH equipment. Cold
electrospray mass spectrometric measurements were realized on a JEOL
JMS 700 equipment cooling the supply tube with dry ice.
Preparative Part. Poly[dimethyl-µ2-(2,5-pyridinedicarboxylato-
O,O′,N)tin] (1). A solution of 2,5-pyridinedicarboxylic acid (0.152 g,
0.910 mmol) and dimethyltin(IV) oxide (0.15 g, 0.910 mmol) in toluene/
ethanol (5:1) was refluxed for 8 h using a Dean-Stark trap. After
cooling to room temperature, the solvent mixture was removed under
vacuum, giving 1 as a light yellow product that was washed with hot
ethanol. Yield: 76%. mp 270 °C (dec). Crystals of [{[Me2Sn(2,5-pdc)-
(H2O)]‚EtOH}n] (1-H2O) were obtained upon slow diffusion of a
dimethyltin(IV) dichloride solution in EtOH into a solution of potassium
2,5-pyridinedicarboxylate in EtOH/H2O.
3. Conclusions
In conclusion, this contribution has shown that the reaction
of 2,5-pyridinedicarboxylate with dimethyl-, di-n-butyl, and
diphenyltin moieties gives either polymeric (R ) Me) or discrete
cyclotrimeric structures (R ) nBu, Ph). The tin atoms in these
complexes are Lewis acid and can form additional bonds to
coordinating solvent molecules such as water, dimethyl sulfox-
ide, and pyridine; alternatively, they are involved in
CdOfSn intermolecular interactions.
It could be shown that both the volume of the organic
substituents attached to the tin atoms and the type of solvent
coordinated to them have an influence on the molecular structure
and the supramolecular arrangement of the complexes. There-
fore, the molecular structure can either be polymeric (zigzag)
or cyclotrimeric, and the supramolecular arrangements observed
include (i) systems having only loosely bound discrete molecules
(van der Waals contacts), (ii) systems having a 2D or 3D
hydrogen-bonded structure, and (iii) systems having a 3D
polymeric coordination structure. If tin-coordinated water
molecules are present, intermolecular hydrogen bonds are
formed, which, because of the size of the complexes, give rise
Spectroscopic Data for 1: IR (KBr): v˜max: 3120 (w), 3065 (w),
2984 (w), 2922 (w), 1722 (m), 1686 (s), 1625 (s), 1575 (m), 1484 (w),
1403 (m), 1327 (m), 1291 (m), 1168 (m), 1136 (m), 1041 (m), 877
(w), 795 (m), 753 (w), 690 (w), 656 (w), 583 (w), 521 (w), 510 (w),
447 (w) cm-1. Anal. Calcd. (%) for C9H9SnNO4: C, 34.44; H, 2.87;
N, 4.46. Found: C, 35.01; H, 3.01; N, 4.73.
9
J. AM. CHEM. SOC. VOL. 127, NO. 9, 2005 3129

A R T I C L E S
Garc´ıa-Zarracino and Ho¨pfl
Spectroscopic data for 1-H2O: IR (KBr): v˜max: 3471 (br, w), 3132
(w), 2925 (w), 1697 (m), 1633 (s), 1484 (w), 1402 (m), 1327 (m),
1284 (w), 1162 (w), 1040 (w), 880 (w), 838 (m), 801 (m), 751 (w),
Anal. Calcd. (%) for C57H39Sn3N3O12‚3H2O: C, 50.04; H, 3.32; N, 3.07.
Found: C, 49.40; H, 3.56; N, 3.26.
NMR Data in DMSO-d6: 1H NMR (400 MHz, DMSO-d6, 20 °C,
TMS) δ ) 7.17 (m, 18H, m-C6H5, p-C6H5), 7.40 (m, 12H, o-C6H5),
8.45 (d, 3H, H3), 8.92 (dd, 3H, H4), 9.72 (s, br, 3H, H6) ppm; 13C
NMR (100 MHz, DMSO-d6, 20 °C, TMS) δ ) 125.3 (C3), 128.2 (m-
680 (w), 574 (w), 534 (w), 458 (w) cm-1
.
Tris[aqua-di-n-butyl-µ2-(2,5-pyridinedicarboxylato-O,O′,N)tin]
(2-H2O). A solution of 2,5-pyridinedicarboxylic acid (0.25 g, 1.50
mmol) and di-n-butyltin(IV) oxide (0.37 g, 1.50 mmol) in toluene/
ethanol (5:1) was refluxed for 8 h using a Dean-Stark trap. After
cooling to room temperature, the solvent mixture was removed under
vacuum, giving 2-H2O as a light yellow product that was washed with
hot ethanol. Yield: 76%. mp 305-307 °C (dec). Crystals of [{(nBu)2Sn-
(2,5-pdc)(DMSO)}3‚3DMSO] (2-DMSO), [{[(nBu)2Sn(2,5-pdc)]‚3MeOH‚
H2O}n] (2-MeOH), [{[(nBu)2Sn(2,5-pdc)(H2O)]3‚1.5H2O‚3EtOH}n] (2-
H2O/EtOH), and [{[(nBu)2Sn(2,5-pdc)(H2O)]3‚1.5H2O‚3PrOH}n] (2-
H2O/PrOH) were obtained after recrystallization of 2 from DMSO,
MeOH, H2O/EtOH,13 and H2O/PrOH, respectively.
Spectroscopic Data for 2-H2O: IR (KBr): v˜max: 3403 (br, w), 3052
(w), 2957 (m), 2926 (m), 2864 (m), 1642 (s), 1604 (s), 1486 (w), 1458
(w), 1404 (s), 1361 (m), 1284 (m), 1161 (w), 1089 (w), 1036 (w), 962
(w), 875 (w), 840 (m), 766 (w), 688 (w), 656 (s), 572 (w), 517 (w)
cm-1. MS (FAB+): m/z (%): 1933.3 (Mpentanuc.-nBu, 0.7), 1595.3
(Mtetranuc., 1.7), 1533.2 (Mtetranuc.-Ph, 2), 1194.22 (Mtrinuc., 3.5), 1136.15
(Mtrinuc.-nBu, 7), 797.2 (Mdinuc., 29), 400.1 (Mmononuc., 100). Anal. Calcd.
(%) for C45H63Sn3N3O12‚3H2O: C, 43.30; H, 5.57; N, 3.37. Found: C,
43.82; H, 5.54; N, 3.61.
NMR Data in DMSO-d6: 1H NMR (400 MHz, DMSO-d6, 20 °C,
TMS) δ ) 0.62 (t, 18H, CH3), 1.08 (m, 12H, γ-CH2), 1.31 (m, 24H,
R-CH2, â-CH2), 8.38 (d, 3H, H3), 8.81 (dd, 3H, H4), 9.71 (dd, 3H,
H5) ppm; 119Sn NMR (149 MHz, DMSO-d6, 20 °C, TMS) δ ) -444
ppm. NMR data in methanol-d4: 1H NMR (400 MHz, MeOD, 20
°C, TMS) δ ) 0.69 (t, 18H, CH3), 1.17 (m, 24H, γ-CH2), 1.53 (m,
12H, R-CH2, â-CH2), 8.53(d, 3H, H3), 9.01 (dd, 3H, H4), 9.83 (dd,
3H, H6) ppm; 119Sn NMR (74.5 MHz, DMSO-d6, 20 °C, TMS) δ )
-412 ppm. NMR data in pyridine-d5: 1H NMR (400 MHz, pyridine-
d5, 20 °C, TMS) δ ) 0.53 (t, 18H, CH3), 1.04 (m, 12H, γ-CH2), 1.44
(m, 12H, â-CH2), 1.84 (m, 12H, R-CH2), 8.87 (dd, 3H, H3), 9.16 (d,
3H, H4), 10.80 (s, 3H, H6) ppm; 13C NMR (100 MHz, pyridine-d5, 20
°C, TMS) δ ) 13.8 (Cδ), 26.6 (Cγ), 28.8 (Câ), 34.4 (CR), 126.0 (C3),
133.6 (C5), 143.6 (C4), 149.3 (C6), 152.6 (C2), 166.2 (C7), 172.9 (C8)
ppm; 119Sn NMR (149 MHz, pyrdidine-d5, 20 °C, TMS) δ ) -426
(br) ppm.
2
C6H5), 128.4 (p-C6H5), 131.2 (C5), 133.1 (o-C6H5, JSn-C ) 70 Hz),
143.3 (C4), 147.3 (C6), 150.1 (i-C6H5), 150.8 (C2), 163.9 (C7), 171.7
(C8) ppm; 119Sn NMR (149 MHz, DMSO-d6, 20 °C, TMS) δ ) -554
ppm.
X-ray Crystallography. X-ray diffraction studies were performed
on a BRUKER-AXS APEX diffractometer with a CCD area detector
(λΜïΚR ) 0.71073 Å, monochromator: graphite). Frames were collected
at T ) 100 K (2-MeOH, 2-H2O/PrOH) and T ) 293 K (1-H2O,
2-DMSO, 3-DMSO) via ω- and Φ-rotation at 10 s per frame
(SMART20a). The measured intensities were reduced to F2 and corrected
for absorption with SADABS (SAINT-NT20b). Structure solution,
refinement, and data output were carried out with the SHELXTL-NT
program package.20c The organic substituents of the R2Sn moieties in
the structures of 2-DMSO, 2-H2O/PrOH, and 3-DMSO are disordered
so that restraints (DFIX and DANG) had to be introduced to obtain
reasonable structural data. Furthermore, more or less disordered solvent
molecules are present in the crystal lattices, which have been also
restrained as far as necessary. In the case of 3-DMSO, the disorder of
the Sn-phenyl groups and especially of the five DMSO molecules
present in the asymmetric unit are responsible for the somewhat high
R values. Non-hydrogen atoms were refined anisotropically, while
hydrogen atoms were placed in geometrically calculated positions using
a riding model. The molecular and crystal structures were created by
the BRUKER SHELXTL and MERCURY software packages.20c,21
Crystallographic data for the structures reported in this article have
been deposited with the Cambridge Crystallographic Data Centre as
supplementary publications no. CCDC-242933-242937. Copies of the
data can be obtained free of charge on application to CCDC, 12 Union
Road, Cambridge CB2 1EZ, U.K. (fax: (+44)1223-336-033; e-
mail: deposit@ccdc.cam.ac.uk; Web: www: http://www.ccdc.
cam.ac.uk).
Acknowledgment. This work was supported by CONACyT.
We thank Dr. Chip Cody from JEOL Company for his assistance
in the realization of the mass spectra.
Supporting Information Available: Additional figures and
tables giving the crystal data and structure refinement informa-
tion, bond lengths and angles, atomic coordinates as well as
isotropic and anisotropic displacement coordinates for all
compounds that have been characterized by X-ray crystal-
lography (PDF, CIF). This material is available free of charge
via the Internet at http://pubs.acs.org.
Tris[aqua-diphenyl-µ2-(2,5-pyridinedicarboxylato-O,O′,N)tin] (3-
H2O). A solution of 2,5-pyridinedicarboxylic acid (0.100 g, 0.598
mmol) and diphenyltin(IV) oxide (0.17 g, 0.598 mmol) in toluene/
ethanol (5:1) was refluxed for 8 h using a Dean-Stark trap. After
cooling to room temperature, the solvent mixture was removed under
vacuum, giving 3-H2O as a light yellow product that was washed with
hot ethanol. Yield: 81%. mp > 300 °C (dec). Crystals of [{(Ph2Sn-
(2,5-pdc)(DMSO)}3‚5DMSO] (3-DMSO) were obtained after recrys-
tallization of 3 from DMSO.
JA0437095
Spectroscopic Data for 3-H2O: IR (KBr): v˜max: 3430 (br, w), 3057
(w), 1645 (s), 1605 (s), 1486 (w), 1406 (s), 1364 (m), 1286 (w), 1158
(w), 1115 (w), 1039 (w), 992 (w), 877 (w), 844 (m), 766 (m), 733
(m), 693 (m), 578 (w), 520 (w), 457 (w) cm-1. MS (FAB+): m/z (%):
1314.02 (Mtrinuc.), 1235.96 (Mtrinuc.-Ph), 877.0 (Mdinuc.), 438.1 (Mmononuc.).
(20) (a) SMART: Bruker Molecular Analysis Research Tool, version 5.618;
Bruker AXS: Madison, WI, 2000. (b) SAINT + NT, version 6.04; Bruker
AXS: Madison, WI, 2001. (c) SHELXTL-NT, version 6.10; Bruker AXS:
Madison, WI, 2000.
(21) Mercury, version 1.1.2; Cambridge Crystallographic Data Centre: Cam-
bridge, U.K., 2002.
9
3130 J. AM. CHEM. SOC. VOL. 127, NO. 9, 2005