Preparation of amorphous water-soluble complexes of biometals with (1-hydroxyethylidene)diphosphonic acid, 2-aminoethanol, and 2-amino-2-(hydroxymethyl)propane-1,3-diol

Abstract

Multifold enhancement of solubility in water of Fe(III) and Mn(II) complexes with (1-hydroxyethylidene)diphosphonic acid has been achieved by their transformation into the corresponding salts via interaction of aqueous suspensions of the poorly soluble complexes with 2-aminoethanol and 2-amino-2-(hydroxymethyl)propane-1,3-diol. Molecular structure of tris(2-hydroxyethanaminium)(1-hydroxyethylidene)-diphosphonate has been determined. Potential agricultural efficiency of the prepared iron and manganese derivatives as well as zinc and copper complexes with (1-hydroxyethylidene)diphosphonic acid as a microfertilizer has been estimated.High solubility of metal complexes in water is a key factor of their efficient application as microfertilizer. Long-term storage of concentrated aqueous solutions (commercial form of many microfertilizers) under conditions of alternating temperature often results in precipitation of crystalline coordination compounds that are dissolved extremely slowly. We have earlier suggested a method to enhance the solubility of iron and manganese salts of (1-hydroxyethylidene)diphosphonic acid H 4 L via the controlled treatment with potassium and ammonium hydroxides [1]. The so formed mixed salts are transformed into colored gels upon water removal, and their further drying yields transparent glass, easily grinded into a powder. Long-term storage of concentrated solutions of the mixed salts over winter and spring does not result in precipitation, probably due to the amorphous structure of the coordination compounds.Herein we present a new method to enhance the solubility of iron and manganese salts via their treatment with 2-aminoethanol I and 2-amino-2-(hydroxymethyl)propane-1,3-diol II. The so prepared compounds as well as zinc and copper derivatives with (1-hydroxyethylidene)diphosphonic acid, readily soluble in water, were tested as microfertilizers.Amines [2] and aqueous ammonia [3] formed poorly soluble mixed salts with (1-hydroxyethylidene)-diphosphonic acid bound to transition or rare-earth metals. The crystalline compounds were isolated from the hot aqueous solutions under conditions of hydrothermal synthesis. On the contrary, the presence of one or three hydroxyl group(s) favored formation of amorphous compounds, readily soluble in water.

Preparation of Water-Soluble Chelated Iron(II) Compounds and Their Use as Microfertilizers. Influence of Solubility Promotors on the Structure of Spring Wheat Harvest under Foliar Treatment

“…Поэтому разработка эффективных методов получения водорастворимых соединений ОЭДФ с биометаллами представляет собой актуальную задачу. Один из способов достижения растворимости заключается в получении двойных калиевых или аммонийных солей (обработка координационного соединения KOH или NH 4 OH) [18], а также в получении аминиевых производных (обработка органическими аминами) [19][20][21][22][23]. Последние названы промоторами растворимости.…”