Synthesis and Physico-Chemical Studies on New Iron, Cobalt, Nickel and Copper Complexes of Some Carboxylic Acids

Abstract

New metal complexes of carboxylic acids have been prepared by a new method based on the electrochemical oxidation of iron, cobalt, nickel and/or copper in non-aqueous solution. The complexes were characterized by analytical, conductivity, spectral and magnetic measurements. The Co(II) and Ni(II) complexes are suggested to have an octahedral structure with partially covalent metal to ligand bonds. The 10 Dq, β and B values agree with those reported for the proposed geometry. Cu(II) complexes possess a distorted octahedral structure. The proton-ligand formation constant, pK^H _a, of isonicotinic acid and the stepwise stability constants of its Fe³⁺, Co²⁺ and Cu²⁺ complexes have been determined potentiometrically in dioxane-water (1:1). The stabilities of the formed complexes were found to be in the order Fe³⁺ > Cu²⁺ > Co²⁺ which agrees well with the Irving-Williams series.