ORGANOPHOSPHORUS HERBICIDES AND PLANT-GROWTH REGULATORS .2. EQUILIBRIUM STUDIES IN AQUEOUS-SOLUTION OF THE COMPLEXATION OF TRANSITION METAL(II) IONS BY N-(PHOSPHONOMETHYL)IMINODIACETIC ACID AND RELATED-COMPOUNDS

Aqueous complex equilibria of nickel(II) ions with N-(phosphonomethyl)glycine, 1, N,N' [phosphinicobis (methylene)] bis (glycine), 2, N,N-bis (phosphonomethyl)glycine, 3, and N-(phosphonomethyl)iminodiacetic acid, 4, as well as of manganese(II), iron(II), cobalt(II) and zinc(II) ions with 4 have been investigated using glass electrode potentiometry. The conditions were: temperature, 25.0-degrees-C; and ionic strength, 0.10 mol dm-3 with respect to chloride ions. The complexation of 4 with copper(II) ions has been examined in the presence of a competing ligand, 4-nitrocatechol, 5. The results indicate that there is strong binding between the plant growth regulators and the metal ions which could affect soil solution speciation and consequently, the bioavailability of these metal ions to plants. Plausible structures of the metal-ligand complexes formed are proposed.