Kinetics and Mechanism of the Ligand Exchange Reaction Between Tetradentate Schiff Base N,N’-ethylen-bis (salicylaldimine) and Ni(N,N’-propylen-bis(salicylaldimine))

Abstract

Visible spectrophotometry is used to study the kinetics of ligand exchange in the system Ni(salpn)/H₂salen with or without triethylamine (NEt₃) and H₂O in dimethylformamide (DMF) solvent at 25 ± 0.1 °C and 0.01M NaNO₃ [H₂salen and H₂salpn are N,N’-ethylen-bis(salicylaldimine) and N,N’-propylen-bis(salicylaldimine), respectively]. It was found that the reaction rate is of the first-order with respect to Ni(salpn). In addition, the effect of NEt₃ andH₂O on the rate of the reaction was examined. The rate of the ligand exchange reaction was accelerated by adding NEt₃ to the reaction mixture. However, the ligand exchange rate was not changed by adding H₂O to the mixture reaction. The effects of NEt₃ and H₂O on the ligand exchange rate show that deprotonation/protonation of the H₂salen ligand and anionic form of H₂salen is important. On the basis of these results, the reaction mechanism is discussed.

KEYWORDS Kinetic, mechanism, Schiff base, Ni complexes, ligand exchange.