Synthesis and structural characterization of a barium coordination polymer based on a μ<sub>2</sub>-monoatomic bridging 4-nitrobenzoate
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The synthesis, spectral characterization, crystal structure and properties of [Ba(H<sub>2</sub>O)<sub>2</sub>(NMF)<sub>2</sub>(4-nba)<sub>2</sub>], <b>1</b> (NMF = <i>N</i>-methylformamide; 4-nba = 4-nitrobenzoate), are reported. <sup>1</sup>H and <sup>13</sup>C NMR spectral data reveal the presence of NMF in <b>1</b>. A strong band at 1660 cm<sup>−1</sup> in the infrared spectrum indicates the binding of amide oxygen to Ba(II) which is confirmed by the single crystal structure. The unique Ba(II) in <b>1</b> situated on a mirror plane exhibits nine coordination and is bonded to two symmetry related monodentate terminal NMF ligands via the amide oxygen, and a terminal aqua ligand. The μ<sub>2</sub>-monoatomic bridging binding mode of each of a crystallographically independent 4-nba ligand and a unique water ligand link the Ba(II) cations into an infinite chain extending along <i>a</i>, leading to the formation of a 1D coordination polymer with Ba···Ba separations of 4.2522(3) Å. In the chain, the {BaO<sub>9</sub>} polyhedra are linked in a face sharing fashion. Thermal decomposition of <b>1</b> results in the formation of BaCO<sub>3</sub> residue. A comparative study of the structural chemistry of several barium coordination polymers is described.
