Preparation of Iron(II) Water-Soluble Compounds Based on Iron(0), (1-Hydroxyethylidene)diphosphonic Acid, and Organic Amines

Abstract

The reaction of aqueous suspension of finely dispersed iron with one equivalent of (1-hydroxyethylidene) diphosphonic acid (H4L) results in poorly soluble iron(II) (1-hydroxyethylidene)diphosphate FeH₂L·H₂O. The reaction with two equivalents of the acid gives a water-soluble compound Fe(H₃L)₂, which undergoes disproportionation up to FeH₂L·H₂O and H₄L. The reaction of a FeH₂L·H₂O aqueous suspension with an organic amine results in the dissolution of the complex. Heating the FeH₂L·H₂O aqueous suspension in a pressure reactor at 150°C in the presence of KF catalytic amounts causes the formation of a new crystal phase and X-ray-amorphous admixtures.