Kinetic Studies of the Hydrolysis of Carboxylic Esters Catalysed by Ethylenediamine Nickel(Ii) Complexes

Abstract

Three novel ethylenediamine nickel(II) complexes, NiL1, NiL2 and NiL3, were synthesized and characterized, and used as mimic hydrolases in the catalytic hydrolysis of a carboxylic ester (PNPP, p-nitrophenyl picolinate). Analysis of the specific absorption spectra of the hydrolytic reaction systems indicated that the catalytic hydrolysis involved the key intermediates formed by PNPP with the nickel(II) complexes. The catalytic mechanism of PNPP hydrolysis was also proposed. The kinetic parameters of the catalytic hydrolysis were calculated, thus the activation energies (∓ 5%) for the catalytic hydrolyses are 15.1, 12.4 and 11.2 kJ mol −1, respectively.