Hydrothermal synthesis, structural characterisation and magnetic behaviour of hybrid complexes of N-(phosphonomethyl)iminodiacetate

Two new compounds containing multidentate chelating organic residues of N-(phophonomethyl)iminodiacetic acid (H(4)pmida), [M(pyr) (H2O)(4)][M-2(Hpmida)(2)(pyr)(H2O)(2)](.)2(H2O) (where pyr=pyrazine and M=Co2+ or Ni2+ for I and II, respectively) have been synthesised and structurally characterised by single-crystal and powder X-ray diffraction, elemental analysis, infrared spectroscopy, thermal analysis and solid-state (31)p MAS NMR. The compounds contain discrete binuclear anionic [M-2(Hpmida)(2)(pyr)(H2O)(2)](2-) units in which one pyrazine ligand bridges two M2+ cations which are completely trapped inside three five-membered chelate rings formed by the Hpmida(3-) ligands. These moieties close pack in the ac plane via a series of strong and highly directional O-H (...) O hydrogen bonds leading to the formation of anionic [Co-2(Hpmida)(2)(pyr)(H2O)(2)](n)(2n-) layers. One-dimensional cationic [M(pyr)(H2O)(4)](n)(2n+) coordination polymers are placed in-between and strongly hydrogen-bonded to these layers. The magnetic properties of these two materials are also reported. (c) 2005 Elsevier B.V. All rights reserved.