Coordination chemistry of iminodiacetic esters. Structural and spectroscopic characterization of copper (II) and zinc (II) monoethyliminodiacetato complexes

The dimethylester of iminodiacetic acid (NH(CH2CO2CH32) reacts with CuCl22H2O and ZnCl2 in aqueous ethanol to yield [Cu(idae)Cl(H2O)] (I) and [Zn(idae)Cl(H2O)] (II), respectively idae = O-ethyliminodiacetato). In both compounds the original ligand is monohydrolyzed and transesterificated by ethanol. When the reaction with copper chloride was carried out in methanol the corresponding methylmonoester copper compound, [Cu(idam)Cl(H2O)] (III) (idam = O-methyliminodiacetato), was the reaction product. The X-ray diffraction structure of compound I was obtained. It crystallizes in the monoclinic system, for 1456 observed independent reflections. The copper (II) atom is in a distorted octahedral geometry, with a fac coordination of the ligand. A chloride ion, a water molecule and a carboxylate oxygen from another molecule complete the coordination sphere. The compound presents a monodimensional zig-zag chain structure where the carboxylate oxygen of one ligand bridges two adjacent copper atoms. The chirality of the N and Cu atoms alternates in the chains. The zinc compound II was characterized by TGA and IR, 13C and 1H NMR spectroscopic methods, and presented a similar structure to compound I.