4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]-hexacosane tetra(nitrato)zinc(II): Synthesis and crystal structure

A new complex salt 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]-hexacosane tetra(nitrato)zinc(II), [H₂(Crypt-222)][Zn(NO₃)₄]^2?, is synthesized and studied by X-ray diffraction analysis: space group $Pbar 1$ , a = 10.556 Å, b = 11.089 Å, c = 14.536 Å, α = 104.63°, β = 109.23°, γ = 99.22°, Z = 2. The structure is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.031 for 3897 independent reflections (CAD-4 automated diffractometer, λMoK _α radiation). The structural units of the crystal are the [Zn(NO₃)₄]^2? complex anion and somewhat disordered 2.2.2-cryptand dication (with two protonated nitrogen atoms). The Zn²⁺ cation forms four strong coordination bonds with the O atoms of four NO ₃ ^? ligands and four weak (secondary) bonds with the second O atoms of these ligands. While ignoring the latter, the Zn²⁺ cation has a strongly distorted tetrahedral configuration. The [H₂(Crypt-222)]²⁺ dication contains trifurcate hydrogen bonds N-H(…O)₃.