New coordination modes in potassium edta salts: K₂[H₂edta]·2H₂O, K₃[Hedta]·2H₂O and K₄[edta]·3.92H₂O

Abstract

Three potassium edta (edta is ethylenediaminetetraacetic acid, H(4)Y) salts which have different degrees of ionization of the edta anion, namely dipotassium 2-({2-[bis(carboxylatomethyl)azaniumyl]ethyl}(carboxylatomethyl)azaniumyl)acetate dihydrate, 2K(+)·C(10)H(14)N(2)O(8)(2-)·2H(2)O, (I), tripotassium 2,2'-({2-[bis(carboxylatomethyl)amino]ethyl}ammonio)diacetate dihydrate, 3K(+)·C(10)H(13)N(2)O(8)(3-)·2H(2)O, (II), and tetrapotassium 2,2',2'',2'''-(ethane-1,2-diyldinitrilo)tetraacetate 3.92-hydrate, 4K(+)·C(10)H(12)N(2)O(8)(4-)·3.92H(2)O, (III), were obtained in crystalline form from water solutions after mixing edta with potassium hydroxide in different molar ratios. In (II), a new mode of coordination of the edta anion to the metal is observed. The HY(3-) anion contains one deprotonated N atom coordinated to K(+) and the second N atom is involved in intramolecular bifurcated N-H···O and N-H···N hydrogen bonds. The overall conformation of the HY(3-) anions is very similar to that of the Y(4-) anions in (III), although a slightly different spatial arrangement of the -CH(2)COO(-) groups in relation to (III) is observed, whereas the H(2)Y(2-) anions in (I) adopt a distinctly different geometry. The preferred synclinal conformation of the -NCH(2)CH(2)N- moiety was found for all edta anions. In all three crystals, the anions and water molecules are arranged in three-dimensional networks linked via O-H···O and C-H···O [and N-H···O in (I) and (II)] hydrogen bonds. K···O interactions also contribute to the three-dimensional polymeric architecture of the salts.

Effect on sludge disintegration by EDTA‐enhanced thermal‐alkaline treatment

“…The ratio of the number of hydrogen bond acceptors/donors in EDTA was 5:2 (Kovács, Nemcsok, & Kocsis, 2). Therefore, in the initial stage of sludge cracking, the large number of N, O hydrogen bond acceptors in the EDTA disodium salt would bind with H–O or H–N bond in the LB‐EPS, forming O–H–O and O–N–H type hydrogen bonds and resulting in the low intensities of H–O or H–N stretching vibration adsorption peaks (Krawczyk & Lis, ). The binding between O–H and EDTA would also explain why the O–H out‐of‐plane bending vibration peak was passivated in the spectra of R samples.…”

Contamination of lithium heparin blood by K2-ethylenediaminetetraacetic acid (EDTA): an experimental evaluation

“…Briefly, chelation entails the generation of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central atom. It is also noteworthy that the EDTA salts have different degrees of ionization ( 20 ). In our study we used vacuum tubes containing dipotassium EDTA (K 2 EDTA) formally known as 2-({2-[bis (carboxylatomethyl) azaniumyl]ethyl}(carboxylatomethyl)azaniumyl)-acetate dihydrate, 2K + · C 10 H 14 N 2 O 8 2− · 2H 2 O.…”