A banana-shaped iron(III)-substituted tungstogermanate containing two types of lacunary polyoxometalate units

A novel polyoxotungstate cluster (H2en)2.5H9[Fe6Ge3W24O94(H2O)2] · 14H2O (1) (en = ethylenediamine) has been hydrothermally synthesized and structurally characterized by IR, TGA and single-crystal X-ray diffraction. The polyoxoanion skeleton of 1 is composed of two tri-FeIII substituted B-α-(Fe3GeW9O40) Keggin units connected by an unique hexavacant GeW6O26 Keggin fragment, leading to the first Fe(III)-containing banana-shaped tungstogermanate. Magnetic measurements of 1 reveal that the exchange interactions within the trimetal clusters are antiferromagnetic.