Syntheses, structures and properties of two multi-iron-samarium/multi-iron substituted germanotungstates

A heterometallic hexameric germanotungstate containing iron-lanthanide cluster fragments (enH₂)₁₃HK₉[Fe ₆Sm₆(H₂O)₁₂(α-GeW ₁₀O₃₈)₆]·42H₂O (1) and a hexairon substituted double sandwich-type germanotungstate (enH ₂)₆K[HFe₆(B-α-GeW₉O ₃₄)₂(α-GeW₆O₂₆)(H ₂O)₂]·11H₂O (2) (en = 1,2-ethylenediamine) have been hydrothermally synthesized and structurally characterized using elemental analyses, inductively coupled plasma atomic emission spectrometry, IR spectra, powder X-ray diffraction (PXRD), thermogravimetric (TG) analyses and single-crystal X-ray diffraction. The common features of 1 and 2 are that both are based on lacunary Keggin-type germanotungstate fragments. 1 is the first heterometallic hexameric germanotungstate consisting of six {Fe-(μ₃-O)₃-Sm} bridges, while two double sandwich-type fragments in 2 are connected together through two potassium cations forming hexameric germanotungstate units. The magnetic susceptibility measurements demonstrate the presence of antiferromagnetic interactions in both compounds.