Self-Assembly of Polymer and Sheet Structures in Palladium(II) Complexes Containing Carboxylic Acid Substituents
dataset
posted on 2002-09-10, 00:00 authored by Zengquan Qin, Michael C. Jennings, Richard J. Puddephatt, Kenneth W. MuirA series of complexes <i>trans-</i>[PdCl<sub>2</sub>L<sub>2</sub>] has been prepared by the reaction of [PdCl<sub>2</sub>(PhCN)<sub>2</sub>] and/or Na<sub>2</sub>[PdCl<sub>4</sub>] with
L = pyridine or quinoline ligands having one or two carboxylic acid groups. These complexes can form 1-D polymers
through O−H···O hydrogen bonding between the carboxylic acid groups, as demonstrated by structure determinations
of [PdCl<sub>2</sub>(NC<sub>5</sub>H<sub>4</sub>-4-COOH)<sub>2</sub>], [PdCl<sub>2</sub>(NC<sub>5</sub>H<sub>4</sub>-3-COOH)<sub>2</sub>], and [PdCl<sub>2</sub>(2-Ph-NC<sub>9</sub>H<sub>5</sub>-4-COOH)<sub>2</sub>]. In some cases, solvation
breaks down the O−H···O hydrogen-bonded structures, as in the structures of [PdCl<sub>2</sub>(NC<sub>5</sub>H<sub>4</sub>-3-COOH)<sub>2</sub>]·2DMSO
and [PdCl<sub>2</sub>(2-Ph-NC<sub>9</sub>H<sub>5</sub>-4-COOH)<sub>2</sub>]·4DMF, while pyridine-2-carboxylic acid underwent deprotonation to give the
chelate complex [Pd{NC<sub>5</sub>H<sub>4</sub>-2-C(O)O)<sub>2</sub>]. The complexes <i>trans-</i>[PdCl<sub>2</sub>L<sub>2</sub>], L = pyridine-3,5-dicarboxylic acid or 2,6-dimethyl pyridine-3,5-dicarboxylic acid, self-assembled to give 2-D sheet structures, with hydrogen bonding between
the carboxylic acid groups mediated by solvate methanol or water molecules. In the cationic complexes [PdL‘<sub>2</sub>L<sub>2</sub>]<sup>2+</sup>
(L‘<sub>2</sub> = Ph<sub>2</sub>PCH<sub>2</sub>PPh<sub>2</sub>, Ph<sub>2</sub>P(CH<sub>2</sub>)<sub>3</sub>PPh<sub>2</sub>; L = pyridine carboxylic acid; anions X<sup>-</sup> = CF<sub>3</sub>SO<sub>3</sub><sup>-</sup>), hydrogen bonding
between the carboxylic acid groups and anions or solvate acetone molecules occurred, and only in one case was
a polymeric complex formed by self-assembly.
