Study of lron(Ill), Cobalt(II), Nickel(ll), Copper(II) and Manganese(II) Chelates of Vanillin-Hydrazone

Chemical Laboratories, M. L. B. Girls' College, Bhopal-462 001

Manuscript received 9 November 1982, revised 4 January 1984, accepted 8 November 1984

Quantitative charcterisation of chelation reactions of vanillin-hydrazone (Van-by) with Fe^llI , Co^Il, Ni^lI, Cu^II and Mn^II has been done potentiometrically in 20% aqueous ethanolic solution. Stepwise and overall proton-ligand and metal-ligand formation constants, and the thermodynamic parameters (ΔG, ΔH and ΔS) have been raported at 30° and 0.1 M (KNO₃) ionic strength. The reactions have very high values of negative enthalpy change indicating high degree of covalent character in the metal-ligand bond.