FORMATION AND STABILITY OF PROTON-AMINE-INORGANIC ANION COMPLEXES IN AQUEOUS-SOLUTION

Interaction of some amines with inorganic ligands was studied potentio metrically in aqueous solutions at 25 degrees C at different ionic str engths. The systems taken into account were: meta-PP, meta-TPP, en-PP, en-TPP, en-HPO42-, dap-SO42-, tetren-HPO42-, 6da-PP and 8da-TPP (meta = methylamine, en = ethylenediamine, tetren = tetraethylenepentamine, dap = 1,2-diaminopropane, 6da = 1,6-hexanediamine, 8da = 1,8-octanedi amine, PP = pyrophosphate, TPP = tripolyphosphate). Several ALH(r) spe cies are formed for all the studied mixed systems (A = amine, L = inor ganic ligand), and in some cases A(p)L(q)H(r) species were also found. The stability of mixed proton-ligand-ligand species is proportional t o the charges involved in the complexation reaction and, to some exten t, it depends on steric characteristic of the ligands. A simple relati onship has been found between formation constants of mixed ligand spec ies and charges involved in the complexation reaction. The ionic stren gth dependence of formation constants has been taken into account, and it was found that, also for these types of mixed complexes, a general equation independent of the nature of the reactants can be used.