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Stereochemistry of hexacoordinated transition metal complexes with iminodiacetamide ligands

Hexacoordinated transition metal complexes of tridentate ligands L with ML2 stoichiometry can form several geometrical isomers: meridional, trans-facial, and delta or lambda cis-facial. The configuration of isomers is affected by steric and electronic properties of the ligands and coordinating ability of the counterions [1]. Derivatives of iminodiacetamide (imda) are studied as tridentate ligands and in all known complexes the iminodiacetamides act as O, N, O’ chelators. The Cambridge Structural Database (CSD) contains crystallographic data for less than 20 metal complexes with iminodiacetamide or its N- substituted derivatives. All reported complexes of N-substituted imda derivatives are trans-facial isomers [2]. In this communication we present the synthesis and characterization of phenyl iminodiacetamide derivatives (L1-L6) and their ML2 complexes with transition metals, M = Zn(II), Co(II), Ni(II) or Cd(II). The amide nitrogen atoms were substituted with phenyl groups in order to increase their solubility in common organic solvents and enable characterization of complexes in solution. To test the effect of the ligands electronic properties on the complex configuration, ligands were prepared with electron donor or electron withdrawing groups on the para- position of phenyl rings (R). The complexes were characterized in solid state (single crystal X-ray diffraction, IR, TG) and in solution (1H and 13C NMR, IR, UV-Vis).

Phenyl iminodiacetamide, synthesis and characterization

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