Amide Hydrolysis Reactivity of a N₄O-Ligated Zinc Complex:  Comparison of Kinetic and Themodynamic Parameters with Those of the Corresponding Amide Methanolysis Reaction

Abstract

Treatment of the mononuclear amide-appended zinc complex [(ppbpa)Zn](ClO4)2 (1(ClO4)2) with Me4NOH.5H2O in CD3CN/D2O (3:1) results in the formation of the deprotonated amide species [(ppbpa-)Zn]ClO4 (2). Upon heating in CD3CN/D2O, this complex undergoes amide hydrolysis to produce a zinc carboxylate product, [(ambpa)Zn(O2CC(CH3)3)]ClO4 (3). X-ray crystallography, 1H and 13C NMR, IR, and elemental analysis were used to characterize 3. The hydrolysis reaction of 1(ClO4)2 exhibits saturation kinetic behavior with respect to the concentration of D2O. Variable-temperature kinetic studies of the amide hydrolysis reaction yielded DeltaH++ = 18.0(5) kcal/mol and DeltaS++ = -22(2) eu. These activation parameters are compared to those of the corresponding amide methanolysis reaction of 1(ClO4)2.