The crystal structures of a macrocycle containing 2,6-pyridino and piperazino subunits and of the tetrachlorocobaltate(II) salt of its diprotonated cation

Abstract

The multiheteromacrocycle C₂₆H₃₈N₆O₄ is prepared by reaction of 2,6-dichloropyridine with NN′-bis-(2-hydroxyethyl)piperazine. Counter data obtained from crystals of space group P2₁/c having a= 10.498(3), b= 4.748(2), c= 26.032(8)Å, β= 96.42(2)°, and Z= 2 were used in the refinement, which converged with R 0.043 for 1 060 observed data. The molecule possesses crystallographic C_i symmetry with the piperazino subunits in the chair conformation. Reaction of this macrocycle with CoCl₂ has led to diprotonation. Crystals of [C₂₆H₄₀N₆O₄][CoCl₄] conform to space group P2₁/c with a= 15.258(6), b= 28.676(12), c= 15.538(5)Å, β= 107.18(3)°, and Z= 8. Refinement using 2 239 observed data measured on a diffractometer has yielded R 0.108. The crystal structure consists of [C₂₆H₄₀N₆O₄]²⁺ ions having essentially identical conformations to the macrocycle C₂₆H₃₈N₆O₄, each forming two hydrogen bonds to tetrahedral [CoCl₄]^2– ions. The Co–Cl distances within the complex anions average 2.260(8)Å. The array of [CoCl₄]^2– anions approximates a C-centred structure with the true b axis halved.