Preparation of Water-Soluble Zinc(II) Complexes with Ethylenediaminetetraacetic Acid: Molecular Structure of Zinc Ethylenediaminetetraacetate Trihydrate

Poorly soluble zinc ethylenediaminetetraacetate zincate Zn[ZnL] reacts with sodium Na4L, potassium K4L, ammonium (NH4)(4)L, 2-ammonioethanol (H3NCH2CH2OH)(4)L, and hexamethylene-1,6-diammonium {H3N(CH2)(6)NH3}(2)L salts of ethylenediaminetetraacetic acid H4L to give readily soluble sodium Na-2[ZnL], potassium K-2[ZnL], ammonium (NH4)(2)[ZnL], 2-ammonioethanol (H3NCH2CH2OH)(2)[ZnL], and hexamethylene-1,6-diammonium {H3N(CH2)(6)NH3}[ZnL] ethylenediaminetetraacetate zincates. The reaction of tetrakis(triethylammonium) salt {(C2H5)(3)NH}(4)L with Zn[ZnL] does not give the expected bis(triethylammonium) ethylenediaminetetraacetate zincate {(C2H5)(3)NH}(2)[ZnL], but gives instead mono(triethylammonium) ethylenediaminetetraacetate zincate, {(C2H5)(3)NH}H[ZnL]; in aqueous solution, this product generates poorly soluble zinc ethylenediaminetetraacetate H-2[ZnL(H2O)]center dot 2H(2)O, which was studied by X-ray diffraction (CCDC no. 2172274).