Complexes of rhodium with thiobis(ethylenenitrilo)tetraacetic acid; a potential bifunctional chelate for use in radiotherapy

Abstract

Reaction of rhodium trichloride with the potential bifunctional chelating agent thiobis(ethylenenitrilo)tetraacetic acid (H₄tedta) gave the complex [Rh(H₃tedta)Cl₂]·H₂O. Both chloride ligands are readily lost on refluxing in water, to give [Rh(Htedta)]·3H₂O which has been characterised by an X-ray study. Further reaction with dilute HX (X = Cl, Br or I) led to the monohalides [Rh(H₂tedta)X]·nH₂O shown by ¹³C-{¹H} NMR spectroscopy to have halide trans to sulfur. In contrast, thiocyanate is shown to bind trans to nitrogen. The complexes represent the first isolated mononuclear compounds of this thioether-containing analogue of ethylenediaminetetraacetate.