Structure and NMR properties of the dinuclear complex di-μ-azido-κ4 N 1:N 1-bis-[(azido-κN)(pyridine-2-carboxamide-κ2 N 1,O)zinc(II)

Cándida Pastor Ramírez,Yasmi Reyes Ortega,Samuel Hernández Anzaldo,Sylvain Bernès

doi:10.1107/s2056989020016680

Cándida Pastor Ramírez, Yasmi Reyes Ortega + Show 2 more

Open Access

https://doi.org/10.1107/s2056989020016680

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Abstract

The new diamagnetic complex, [Zn2(N3)4(C6H6N2O)2] or [Zn2(pca)2(μ1,1-N3)2(N3)2] 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 P . The pca ligand chelates the metal centre via the pyridine N atom and the carbonyl O atom. One azido ligand bridges the two symmetry-related Zn2+ cations in the end-on 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 1H and 13C NMR chemical shifts for the free ligand pca as for the Zn complex.

Highlights

Polynuclear complexes have received the attention of coordination chemists as they are ideal candidates for developing new functional molecular materials
Some complexes have been proposed as models for the active sites of zinc-containing enzymes (Parkin, 2000; Doring et al, 2002), while others have been studied for their catalytic properties (Dey et al, 2002) or for the purpose of producing OLED devices (Sano et al, 2000; Tokito et al, 2000; Ray et al, 2012)
We report the molecular structure of a dinuclear complex with bridging and non-bridging azido ligands, synthesized with picolinamide, a pyridine derivative with an amido group, suitable for the chelation of transition metals (Ðakovicet al., 2008)

Summary

Chemical context

Polynuclear complexes have received the attention of coordination chemists as they are ideal candidates for developing new functional molecular materials. Co-ligands are important for the structure and properties of the complex, especially if they can bridge metal centres. Several architectures occur depending on whether EE or EO bridges are present, which can be symmetric or asymmetric, single or multiple, and associated or not with other bridges (Goher et al, 2000; Maji et al, 2001) In this context, our group has paid attention to the synthesis of Zn2+ complexes including azido ligands, with the aim of using these diamagnetic compounds as NMR probes for other structurally related or analogous complexes. We report the molecular structure of a dinuclear complex with bridging and non-bridging azido ligands, synthesized with picolinamide, a pyridine derivative with an amido group, suitable for the chelation of transition metals (Ðakovicet al., 2008). Based on previous reports in the literature, the former can be assigned to bridging-EO azido ligands and the latter to

Structural commentary

NMR measurements and chemical shift calculations

Synthesis and crystallization