Acta Crystallographica Section C

Crystal Structure Communications

Volume 64, Part 6 (June 2008)

metal-organic compounds

sq3137 scheme

Acta Cryst. (2008). C64, m217-m220 [ doi:10.1107/S0108270108010706 ]

Coordination behaviour and two-dimensional-network formation in poly[[-aqua-diaqua(₅-propane-1,3-diyldinitrilotetraacetato)dilithium(I)cobalt(II)] dihydrate]: the first example of an M^II-1,3-pdta complex with a monovalent metal counter-ion

U. Rychlewska, B. Warzajtis, M. I. Djuran, D. D. Radanovic, M. Dj. Dimitrijevic and S. Rajkovic

Abstract: The title compound, {[CoLi₂(C₁₁H₁₄N₂O₈)(H₂O)₃]·2H₂O}_n, constitutes the first example of a salt of the [M^II(1,3-pdta)]^2- complex (1,3-pdta is propane-1,3-diyldinitrilotetraacetate) with a monopositive cation as counter-ion. Insertion of the Li⁺ cation could only be achieved through application of the ion-exchange column technique which, however, appeared unsuccessful with other alkali metals and the ammonium cation. The structure contains two tetrahedrally coordinated Li⁺ cations, an octahedral [Co(1,3-pdta)]^2- anion and five water molecules, two of which are uncoordinated, and is built of two-dimensional layers extending parallel to the (010) lattice plane, the constituents of which are connected by the coordinate bonds. O-H_waterO hydrogen bonds operate both within and between these layers. The crystal investigated belongs to the enantiomeric space group P2₁ with only one ( [Lambda] ) of two possible optical isomers of the [Co(1,3-pdta)]^2- complex. A possible cause of enantiomer separation during crystallization might be the rigidification and polarization of the [M(1,3-pdta)]^2- core, resulting from direct coordination of Li⁺ cations to three out of four carboxylate groups constituting the 1,3-pdta ligand. The structure of (I) differs considerably from those of the other [M^II(1,3-pdta)]^2- complexes, in which the charge compensation is realized by means of divalent hexaaqua complex cations. This finding demonstrates a significant structure-determining role of the counter-ions.

Formula: [CoLi₂(C₁₁H₁₄N₂O₈)(H₂O)₃]·2H₂O