A carbon-free inorganic–metal complex consisting of an all-nitrogen pentazole anion, a Zn(ii) cation and H2O

Abstract

A carbon-free inorganic–metal complex [Zn(H₂O)₄(N₅)₂]·4H₂O was synthesized by the ion metathesis of [Na(H₂O)(N₅)]·2H₂O solution with Zn(NO₃)₂·6H₂O. The complex was well characterized by IR and Raman spectroscopy, elemental analysis (EA), powder X-ray diffraction (PXRD), and differential scanning calorimetry (DSC). The structure of the complex was confirmed by single-crystal X-ray crystallography and a Zn(II) ion is coordinated in a quadrilateral bipyramid environment in which the axial position is formed by two nitrogen atoms (N1) from two pentazolate rings (cyclo-N₅⁻) and the equatorial plane is formed by four oxygen atoms (O1) from four coordinated water molecules. The thermal analysis of [Zn(H₂O)₄(N₅)₂]·4H₂O reveals that although water plays an important role in stabilizing cyclo-N₅⁻, dehydration does not cause immediate decomposition of the anion. However, cyclo-N₅⁻ decomposed into N₃⁻ and N₂ gas at 107.9 °C (onset). Based on its chemical compatibility and stability, the complex exhibits promising potential as a modern environmentally-friendly energetic material.