Synthesis of One- and Two-Dimensional Coordination
Polymers Containing Organotin Macrocycles. Reactions of (<i>n</i>-Bu<sub>3</sub>Sn)<sub>2</sub>O with Pyridine Dicarboxylic Acids.
Structure-Directing Role of the Ancillary 4,4′-Bipyridine Ligand
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Abstract
The reaction of (<i>n</i>-Bu<sub>3</sub>Sn)<sub>2</sub>O with pyridine-2,6-dicarboxylic acid (<b>L1H</b><sub><b>2</b></sub>) in a 1:1 ratio resulted in the formation of
a one-dimensional
(1D) coordination polymer [(<i>n</i>-Bu<sub>3</sub>Sn)<sub>2</sub>(<i>n</i>-Bu<sub>2</sub>Sn)<sub>2</sub>(μ-L1)<sub>2</sub>(μ-OH)<sub>2</sub>]<sub><i>n</i></sub> (<b>1</b>). The formation of <b>1</b> is accompanied by a <i>Sn</i>–<i>butyl</i> bond cleavage reaction
involving half of the organotin units. The formation of the 1D coordination
polymer is facilitated by the multisite coordination capability of
the dianionic ligand L1. The reaction of (<i>n</i>-Bu<sub>3</sub>Sn)<sub>2</sub>O with pyridine-2,5-dicarboxylic acid (<b>L2H</b><sub><b>2</b></sub>) or pyridine-3,5-dicarboxylic
acid (<b>L3H</b><sub><b>2</b></sub>), on the other hand,
results in the generation of the two-dimensional (2D) coordination
polymers [(<i>n</i>-Bu<sub>3</sub>Sn)<sub>2</sub>(μ-L2)]<sub><i>n</i></sub> (<b>2</b>) and [(<i>n</i>-Bu<sub>3</sub>Sn)<sub>4</sub>(μ-L3)<sub>2</sub>]<sub><i>n</i></sub> (<b>3</b>), respectively. The formation of <b>2</b> and <b>3</b> emphasizes the importance of the relative
orientation of the coordinating units in the multisite coordination
ligand. Compounds <b>1</b>–<b>3</b> show a rich
supramolecular architecture in their solid state as a result of multiple
secondary interactions. Investigation of the fate of the reactions
of (<i>n</i>-Bu<sub>3</sub>Sn)<sub>2</sub>O with pyridine
dicarboxylic acids in the presence of a bridging ligand was carried
out. In all the cases when the reactions were carried out in the presence
of 4,4′-bipyridine (4,4′-bipy), 1D coordination polymers
[(<i>n</i>-Bu<sub>3</sub>Sn)<sub>2</sub>(μ-L1)(μ-4,4′-bipy)]<sub><i>n</i></sub> (<b>4</b>), [(<i>n</i>-Bu<sub>3</sub>Sn)<sub>2</sub>(μ-L3)(μ-4,4′-bipy)]<sub><i>n</i></sub> (<b>5</b>), and [(<i>n</i>-Bu<sub>3</sub>Sn)<sub>2</sub>(μ-L2)(μ-4,4′-bipy)]<sub><i>n</i></sub> (<b>6</b>) are formed. In these cases,
the 4,4′-bipyridine ligand serves as one of the connectors
that link the organotin units. Interestingly, in the presence of 4,4′-bipyridine, <i>Sn</i>–<i>butyl</i> bond cleavage does not
take place. While the 1D coordination polymers <b>4</b> and <b>5</b> form three-dimensional supramolecular architectures in their
solid state, compound <b>6</b> possesses a 2D supramolecular
architecture
