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

Abstract

The dimethylester of iminodiacetic acid (NH(CH 2CO 2CH 3 2) reacts with CuCl 2·2H 2O and ZnCl 2 in aqueous ethanol to yield [Cu(idae)Cl(H 2O)] (I) and [Zn(idae)Cl(H 2O)] (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(H 2O)] ( III) (idam = O-methyliminodiacetato), was the reaction product. The X-ray diffraction structure of compound I was obtained. It crystallizes in the monoclinic system, P2 1/c, a = 13.690(5), b = 5.275(4), c = 14.811(5) A ̊ , β = 106.57(3)°, Z = 4, final R = 0.034 and Rw = 0.038 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.