Preparation and characterization of chromium(III)–ethylenediamine-tetra-acetic acid (EDTA) complexes in which the EDTA is only partly co-ordinated and probably terdentate

Abstract

Complexes which analyse for Cr^IIIYH₃(Cl)₂(H₂O)₄ and Cr^IIIYH₃(Br)₂(H₂O)₄(where ethylenediaminetetra-acetate or EDTA = Y^4–) have been prepared by treating the complex [Cr^IIIYH(H₂O)] with hydrochloric and hydrobromic acids respectively. Evidence based on analysis, equivalent weight determinations, and conductivity and spectral measurements is consistent with the formulae [Cr^IIIYH₃(Cl)₂(H₂O)],3H₂O and [Cr^IIIYH₃(Br)₂(H₂O)],3H₂O, where the ethylenediaminetetra-acetate is probably terdentate in both cases. The related complex Rb[Cr^IIIYH₂(Cl)₂(H₂O)],H₂O has also been prepared. Possible structures are considered and of these one in which one of the nitrogens of the EDTA and the two carboxylate groups associated with it are unco-ordinated seems most likely.