Structure and NMR properties of the dinuclear complex di-μ-azido-κ : -bis-[(azido-κ)(pyridine-2-carboxamide-κ ,)zinc(II)].

The new diamagnetic complex, [Zn(N)(CHNO)] or [Zn(pca)(μ-N)(N)] was synthesized using pyridine-2-carboxamide (pca) and azido ligands, and characterized using various techniques: IR spectroscopy and single-crystal X-ray diffraction in the solid state, and nuclear magnetic resonance (NMR) in solution. The mol-ecule is placed on an inversion centre in space group . The pca ligand chelates the metal centre the pyridine N atom and the carbonyl O atom. One azido ligand bridges the two symmetry-related Zn cations in the coordination mode, while the other independent azido anion occupies the fifth coordination site, as a terminal ligand. The resulting five-coordinate Zn centres have a coordination geometry inter-mediate between trigonal bipyramidal and square pyramidal. The behaviour of the title complex in DMSO solution suggests that it is a suitable NMR probe for similar or isostructural complexes including other transition-metal ions. The diamagnetic nature of the complex is reflected in similar H and C NMR chemical shifts for the free ligand pca as for the Zn complex.