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-bi s (phosphonomethyl)glycine, 3, and N-(phosphonomethyl)iminodiacetic ac id, 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 w ith copper(II) ions has been examined in the presence of a competing l igand, 4-nitrocatechol, 5. The results indicate that there is strong b inding between the plant growth regulators and the metal ions which co uld affect soil solution speciation and consequently, the bioavailabil ity of these metal ions to plants. Plausible structures of the metal-l igand complexes formed are proposed.