Unexpected N-coordination in sodium N-phenyltetrazol-5-selenones/thiones: Synthesis, crystal structure, and chalcogen-centered alkylation

Aromatic-substituted isoselenocyanates were reacted with sodium azide to yield novel sodium salts of phenyltetrazol-5-selenones, alongside analogous phenyltetrazol-5-thione derivatives for comparison. These compounds were fully characterized using single-crystal X-ray diffraction, NMR spectroscopy, IR/Raman spectroscopy, and high-resolution mass spectrometry. Surprisingly, X-ray crystallography revealed an unconventional coordination mode, with the sodium cation binding to the tetrazole nitrogen atoms rather than the selenium or sulfur centers, while preserving the C=Se/S double bonds. The electronic structure and delocalization effects were explored using DFT calculations, aromaticity criteria (EDDB and GIMIC), and vibrational spectroscopy in both solid and solution states. Hydrogen bonding studies demonstrated that nitrogen and chalcogen atoms in 2a and 5a interact with water, with S(Se)···HO bonds being significantly weaker than N···HO—consistent with the observed chalcogen-directed alkylation at Se/S centers. Additionally, the influence of deuterated solvents and temperature on (Herr, 2002)13С-77Se bond NMR parameters was established. This comprehensive study offers novel insights into the coordination chemistry and reactivity of tetrazole-based chalcogen derivatives, while also elucidating their structural and electronic properties. © 2025 Elsevier B.V., All rights reserved.