Determination of pKa of the methylene moiety of the Ni(II) complexed glycine Schiff base with N-(2-benzoyl-4-chlorophenyl)-2-dibutylamino-acetamide by spectroscopic methods in non-aqueous conditions

Abstract

The C-H substitution of the methylene moiety of glycine in nickel(II) glycine Schiff bases has proven useful for the preparation of a variety of α-amino acids. Recently, it has been shown that the integration of electron withdrawing groups into the ligand system of these nickel(II) complexes enhances their reactivity. It is hypothesized that this enhanced reactivity is, in part, due to decreased pKa of the α-proton of glycine due to delocalization of the resulting charge. However, there is a lack information or direct evidence of the relationship between the pKa of the α-protons of glycine in these complexes and perturbation of the electronic system of the ligand in the literature. Therefore, to better understand the observed reactivity, a method to determine the pKa of these complexes in non-aqueous solvent conditions is needed. In this work, the method and data analysis to find the pKa of the Ni(II) complex of glycine Schiff base with N-(2-benzyoly-4-chlorophenyl)-2-dibutylamino-acetamide is described.