Kinetic studies on the dissociation of triethylenetetramine complexes of nickel(II) and copper(II) in aqueous acid media

Abstract

From stopped-flow spectrophotometric studies on the kinetics of dissociation of [M(trien)]2+ (M=CuII, NiII) to Maq2+ and trien H44+ in aqueous acid medium, it has been established that the reaction occurs in a complex manner conforming to the relation $$k_{obs} = k_o + k'_H [H^ + ] + k''_H [H^ + ]^2 $$ At 250 C, I=0.1 mol dm−3 the values of the constants are ko (s−1)=1.2(Ni), 3.0(Cu); k′H (dm3 mol−1 s−1)=37 (Ni), 257 (Cu); k″H (dm6 mol−2 s−1)=0 (Ni), 83,300 (Cu). The enthalpy and entropy of activation for the reactions have been evaluated and a plausible reaction scheme is proposed and discussed.