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

A new crystalline complex salt, 4,7,13,16,21,24-hexaoxa-1,10-diazaniabicyclo[8.8.8]hexacosane tetra(nitrato-O)copper(II) [H₂(Crypt-222)]²⁺ · [Cu(NO₃)₄]^2?(I), is synthesized and studied using X-ray diffraction analysis (space group P2₁/c, a = 10.264 Å, b = 14.798 Å, c = 19.516 Å, β = 100.20°, Z = 4). The structure is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.032 for 4050 independent reflections (CAD-4 automated diffractometer, λMoK _α radiation). Salt I exist in crystals as individual ions: the [Cu(NO₃)₄]^2? complex anion and the slightly disordered dication of 2.2.2-cryptand with two protonated nitrogen atoms. The Cu²⁺ cation has a square coordination somewhat distorted toward a flattened tetrahedron with four coordination bonds with the O atoms of the four NO ₃ ^? ligands. Trifurcate hydrogen bonds of the [H₂(Crypt-222)]²⁺ type are observed in the N-H(? O)₃ dication.