Metal chelates of N-carbamoylmethyl-iminodiacetate(2-) ion - Part IV. Isostructural ternary mixed-ligand cobalt(II) and nickel(II) chelates with N-carbamoylmethyl-iminodiacetate(2-) ion, imidazole and aqua ligands. Synthesis, molecular and crystal st

摘要

Stoichiometric reaction of CoCO3. Co(OH)(2). 2H(2)O, or NiCO3. 2Ni(OH)(2). 4H(2)O with H(2)ADA and imidazole (Him) in water yields crystalline samples of compounds aqua(imidazole)(N-carbamoylmethyl-iminodiacetato)metal(II), [M(ADA)(Him)(H2O)].1.5H(2)O (M = Co, compound I, dark pink: M = Ni, compound II, bluish). Single-crystal X-ray diffraction studies were carried out. Both complexes are isostructural (orthorhombic system, space group Pna2(1), Z = 8). These crystals consist of slightly asymmetrical octahedral coordination units linked in a tridimensional network stabilised by hydrogen bonds when all N-H bonds of ADA and Him and probably O-H bonds of water molecules are involved. The asymmetric unit has two independent but very similar complex molecules and three water ones. Coordination bond distances for I (average in Angstrom): Co-N(amino) = 2.14(1), Co-O(carboxyl) = 2.06(1), Co-O(carboxyl) = 2.08(1) and Co-O(amide) = 2.15(1) with ADA, Co-N(Him)= 2.04(1), and Co-O(aqua) = Coordination bond lengths for II (average in Angstrom): Ni-N(amino) = 2.08(1), Ni-O(carboxyl) = 2.04(1), Ni-O(carboxyl) = 2.06(1) and Ni-O(amide) = 2.012(1) with ADA, Ni-N(Him) = 2.01(1), and Ni-O(aqua) = 2.12(1). The ADA ligand acts as a tripodal tetradentate chelating one. On the basis of the octahedral structures of [Ni(ADA)(H2O)(2)], reported in the literature, and of the new compounds, it is concluded that there is a preference for the N(Him)donor atom to occupy the trans-position to the M-N(ADA) bond. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 58]