COPPER(II) COMPLEXES OF N-CARBOXYMETHYL-D,L-THREONINE IN AQUEOUS SOLUTION. STRUCTURE OF AQUA (N-CARBOXYMETHYL-D,L-THREONINATO (2-)) COPPER(II)

Abstract

Abstract Formation constants for Cu(II) complexes with N-carboxymethyl-D,L-threonine (H2CMT = H2L) have been determined (I = 0.1M KNO3, 25°C) using the HYPERQUAD program with 652 potentiometric data from the titration of twelve solutions having different H2L concentrations and/or Cu(II)/H2L ratios. Refined values of long βpqr for the species CupLqLr = CuL, CuL2, CuL(OH) and CuL(OH)2 allow simulation of experimental titration curves with good agreement. Aqua (N-carboxymethyl-D,L-threoninato (2-)) copper(II) was synthesized and studied by X-ray diffraction and other physical methods. The structure (monoclinic system, space group P21/c, final R = 0.044 and Rw = 0.051) consists of infinite zigzag chains of [Cu(CMT) (H2O)] groups linked together by hydrogen bonds. The Cu(II) atom exhibits square pyramidal coordination with an additional sixth weak interaction (Cu-O = 2.568(4)A) which involves a terdentate-bridged carboxy-late group closely related to that already claimed in the structure of [Cu(CMPhe) (H2O)], ...