Synthesis, characterization and catalytic activity of coordination polymers derived from monohydroxybenzoic acids and divalent nickel ion

Three novel coordination polymers such as 2HBN, 3HBN and 4HBN, respectively, were obtained from the reaction of nickel nitrate with the sodium salts of the 2-hydroxybenzoic acid, 3-hydroxybenzoic acid and 4-hydroxybenzoic acid. All of these polymers show solubility neither in water nor in the common organic solvents. Therefore they were characterized, in the solid state, by vibrational-, electronic-, electron spin resonance (ESR) spectra and thermogravimetric analysis. Infrared spectra of the polymers confirm the ligand coordination to the metal ions through carboxyl group. The absorption and ESR spectra of the polymers are typical of octahedral nickel(II) complexes. Thermal decomposition of 2HBN, 3HBN and 4HBN seems like a multistep process, which starts with dehydration of adsorbed water followed by the release of coordination water and then fragments of the organic linkers leaving NiO as a final product above 480 °C. Coordination polymers have been of interest as materials for heterogeneous catalysis. Thus, 2HBN, 3HBN and 4HBN were tested as catalytic systems against the decarboxylative cross coupling reaction of a, b-unsaturated carboxylic acids with dioxane. Indeed, expected oxyalkylated products were achieved when 3HBN was used as a catalyst, whereas 2HBN and 4HBN not promoted the reaction. This may be associated to the enhanced electrophilicity of nickel(II) ion in 3HBN when compared to that of 2HBN and 4HBN

Author(s): Ramesh Kataria, Deachen Chuskit and Palani Natarajan

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