Some complexes of thiomalate with bivalent transition metal ions and gold (I)

Abstract

The following complexes of thiomalic acid (tmH 3) with Mn(II), Fe(II), Co(II) and Ni(II) have been prepared and characterized by elemental analyses, magnetic susceptibility measurements from room to liquid nitrogen temperature, and visible and IR spectra: A[M(tm)]· nH 2O where ALi, Na or K, MMn, Fe, Co or Ni, and n is variable; M(tmH)· nH 2O, where M = Mn, Fe or Co; and Ni(tmH 2) 2·2H 2O. The alkali metal salts are antiferromagnetic (Co and Mn), or weakly ferromagnetic (Fe and Ni), and thus the anions are likely to be polymerised. The stoichiometry suggests that triply-charged anions are present, and this is confirmed by the IR spectra which do not contain bands assignable to unionised carboxyl groups. In general, the reflectance spectra are characteristic of octahedrally coordinated transition metal ions, confirming that the anions are polymerised. The remaining complexes have IR spectra containing absorption bands due to unionised carboxyl groups, and their reflectance spectra are as expected for octahedral coordination. Since Ni(tmH 2) 2·2H 2O has a magnetic moment independent of temperature it is believed to be monomeric. The cobalt complex Co(tmH)·3H 2O may also be a monomer, but Mn(tmH)·2H 2O and Fe(tmH)·3H 2O are antiferromagnetic and ferromagnetic respectively, and are therefore believed to be polymers. Some complexes of gold(I) with thiomalic acid have been isolated. These are Au(tmH 2), Na 2[Au(tm)], Ca[Au(tm)]·2H 2O and Ba[Au(tm)]·H 2O. Reactions between Au(tmH 2) and sulphur-containing ligands lead to the release of some or all of the coordinated thiomalic acid. In the reaction of glutathione and cysteine with thiomalatogold(I) polymeric, mixed ligand complexes, i.e. bis(glutathionato)mono(thiomalato)trigold(I) and (cysteinato)(thiomalato)digold(I), were obtained. In the reaction with sodium diethyldithiocarbamate all the thiomalic acid was released and diethyldithiocarbamatogold(I) was precipitated. Albumin also produced a precipitate with thiomalatogold(I), but the thioether methionine did not.