Ferric Chloride and Bromide Complexes with Xanthine and Hypoxanthine

Complexes of the type Fe(LH) 3 LX 2 (LH α xanthine or hypoxanthine; X α Cl or Br) were synthesized by refluxing 2:1 molar mixtures of LH and FeX 3 , in triethyl orthoformate-ethyl acetate for one week. Characterization studies suggest that the new complexes are hexacoordinated and monomeric, involving a cis-FeN 4 X 2 arrangement of the terminal ligands around the Fe 3 + ion. The hypoxanthine ligands probably bind via the N7 imidazole nitrogen to Fe(III). In the case of the xanthine complexes, the N7 and N9 imidazole nitrogens are considered as about equally likely to function as the binding site of the terminal neutral and monoanionic xanthine ligands.