A Three-Dimensional Framework Structure Constructed from 2-(2-Pyridyl-<i>N</i>-oxide) Ethylphosphonic Acid and Nd(III)

A multistep synthesis for 2-(2-pyridyl-N-oxide) ethylphosphonic acid 6-H2 is described along with its spectroscopic (IR, NMR) data and a single-crystal X-ray diffraction structure analysis. Combination of the ligand with Nd(OH)3 results in the formation of a complex Nd(6-H)3. Single-crystal X-ray diffraction analysis reveals a three-dimensional crystal network generated by hydrogen-bonded chains along the crystallographic c axis. The hydrogen bonds are formed between phosphonic acid anion (6-H)-1 protons on one chain and pyridyl N-oxide oxygen atoms in neighboring chains. The asymmetric unit contains 1/3[Nd(6-H)3] and there are two unique Nd(III) atoms, each with 3̄ point symmetry. As a result, each Nd(III) ion is bound to six (6-H)-1 ligands and the symmetry about the Nd(III) ion is octahedral with each vertex occupied by a phosphonate oxygen atom. The Nd−O bond lengths are essentially identical: Nd(1)−O(3), 2.336 (1) Å; Nd(2)−O(4), 2.340 (1) Å. The monoanionic ligand (6-H)-1, therefore, serves to bridge the unique Nd(III) centers.