A three-dimensional framework structure constructed from 2-(2-pyridyl-N-oxide) ethylphosphonic acid and Nd(III)

A multistep synthesis for 2-(2-pyridyl-N-oxide) ethylphosphonic acid 6-H ₂ 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 3 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.