Mixed ligand complex formation of FeIII with boric acid and typical N-donor multidentate ligands

Equilibrium study of the mixed ligand complex formation of FeIII with boric acid in the absence and in the presence of 2,2-bipyridine, 1,10-phenanthroline, diethylenetriamine and triethylenetetramine (L) in different molar ratios provides evidence of formation of Fe(OH)^2 plus Fe(OH)^2 plusFe(L)^3 plus Fe(H2BO4), Fe(OH)(H2BO4)–, Fe(OH)2(H2BO4)2 minus, Fe(L)(H2BO4) and Fe2(L)2(BO4)^ plus complexes. Fe(L)3 , 2 plus Fe(L)2(H2BO4) and Fe2(L)4(BO4)^ plus complexes are also indicated with 2,2´-bipyridine and 1,10-phenanthroline. Complex formation equilibria and stability constants of the complexes at 25 plus-minus1C in aqueous solution at a fixed ionic strength, I = 0,1 mol dm–3 (NaNO3) have been determined by potentiometric method.