Preparation of a water-soluble molybdenum(VI) complex with nitrilotriacetic acid and monoethanolamine. Molecular structure of triammonium [trioxo(nitrilotriacetato)molybdate] monohydrate (NH4)3[MoO3L]·H2O. Application of its solution to increase the productivity of red clover.

Abstract

Varying the ratios of ammonium heptamolybdate, nitrilotriacetic acid and 2-aminoethanol has made it possible to obtain a concentrated solution of the molybdenum complex, which remains stable during long-term storage and does not release solid sediment. In an aqueous solution, 2-aminoethanol replaces ammonium groups in ammonium heptamolybdate, producing mixed ammonium-amine derivatives (NH4)n(NH3CH2CH2OH)6-n[Mo7O24], which cause solution instability and precipitation. Ammonium cations in the HMA molecule can be completely replaced by 2-aminoethanol cations in the course of the reaction in aqueous medium with a sixfold molar excess of 2-aminoethanol to obtain the hexaamine derivative (NH3CH2CH2OH)6[Mo7O24]. In the ternary system ammonium heptamolybdate – nitrilotriacetic acid – 2-aminoethanol, the formation of highly soluble triammonium [trioxo(nitrilotriacetato)molybdate] monohydrate (NH4)3[MoO3L]·H2O (1) is formed, the crystal structure of which has been studied by X-ray diffraction analysis. Using red clover as an example, it has been shown that the resulting solution is agronomically more effective in comparison with a solution of a molybdenum complex with (1-hydroxyethylidene)diphosphonic acid. According to the RSA data, ammonium cations, hydrate water molecules and trioxo(nitrilotriacetato) anions are present in crystal 1 molybdenum, in which molybdenum atoms have the coordination of a distorted square bipyramide with two oxygen atoms of OMo groups and two oxygen atoms of carboxylate ligands in equatorial positions (2,024(5), 1,710(4) and 2,316(5), 2,436(5) Å). The axial angle O(2)Mo(1)N(2) is 147.6(2). The axial positions are occupied by oxygen and nitrogen atoms (the distances O(2)Mo(1) and N(2)Mo(1) are 1,762(5) and 2,185(4) Å accordingly). RSA data: (1) [C6H20MoN4O10, M = 404.20; monoclinic syngony, etc. gr. P21/s; cell parameters: a = 8,002(12) Å, b = 19.82(2) Å, c = 9.931(12) Å; β = 109.48(5), V = 1485(3) Å3, Z = 4; (h) = 1,808 g/cm3;  = 0.939 mm–1; F(000) = 824.0; 2q collection area: 5.98–56.98; –10 ≤ h ≤ 10, –25 ≤ k ≤ 25, –10 ≤ l ≤ 10; total reflections are 30512; independent reflections are 2958 (Rint = 0.0567); GOOF = 1.118; R-factor 0.0493].