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Acta Cryst. (2007). E63, m1803-m1804 [ doi:10.1107/S1600536807025640 ]

Piperazinium hexaaquacobalt(II) bis[bis(pyridine-2,6-dicarboxylato)cobaltate(II)] octahydrate

H. Aghabozorg, J. Attar Gharamaleki, M. Ghadermazi, P. Ghasemikhah and J. Soleimannejad

Abstract: The title compound, (C₄H₁₂N₂)[Co(H₂O)₆][Co(C₇H₃O₄)₂]₂·8H₂O, was obtained by the reaction of cobalt(II) nitrate hexahydrate with the proton-transfer compound piperazinediium pyridine-2,6-dicarboxylate or (pipzH₂)(pydc) (where pipz is piperazine and pydcH₂ is pyridine-2,6-dicarboxylic acid) in aqueous solution. The anionic complex, [Co(pydc)₂]^2-, features six-coordinate Co^II with a distorted octahedral geometry. The structure also contains hexaaquacobalt(II) cations (site symmetry $\\overline{1}$ ), and piperazinium (site symmetry $\\overline{1}$ ) as counter-ions and eight uncoordinated water molecules. The torsion angles indicate that the (pydc)^2- units are almost perpendicular to each other. In the crystal structure, extensive O-HO, N-HO and C-HO hydrogen bonds, as well as ion pairing and distances for [pi] - [pi] interactions between anion fragments, play an important role in stabilizing the structure.

Online 6 June 2007