The antimony(iii)-bridged heteropolyanion sandwich dimers [SbIII3(A-α-XW9O34)2]11− (X = SiIV, GeIV) and C-shaped double-sandwich [SbIII6O2(PW6O26)(A-α-PW9O34)2]15−

Abstract

Interaction of potassium antimony(III) tartrate hydrate K₂(SbC₄H₂O₆)₂·3H₂O with the trilacunary Keggin derivatives [A-α-XW₉O₃₄]¹⁰⁻ (X = Si^IV, Ge^IV) and [A-α-PW₉O₃₄]⁹⁻ in aqueous acidic medium (pH 4.8) resulted in three novel polyanions, [Sb₃(A-α-XW₉O₃₄)₂]¹¹⁻ (X = Si^IV (1), Ge^IV (2)) and [Sb₆O₂(A-PW₆O₂₆)(A-α-PW₉O₃₄)₂]¹⁵⁻ (3), which were isolated as the hydrated potassium salts K₁₁[Sb₃(A-α-XW₉O₃₄)₂]·31H₂O (X = Si^IV (K-1), Ge^IV (K-2)) and the mixed potassium–sodium salt K₁₄Na[Sb₆O₂(A-PW₆O₂₆)(A-α-PW₉O₃₄)₂]·61H₂O (KNa-3) salts, respectively, and characterized by single-crystal X-ray diffraction, IR spectroscopy, as well as elemental and thermogravimetric analyses. The Sb^III-containing polyanions 1–3 possess unique structural features, as they represent the first examples of sandwich-type POMs with trigonal-pyramidal Sb^IIIO₃ linkers. The stability of 1–3 in aqueous media was investigated by multinuclear (¹⁸³W, ³¹P) NMR and UV-Vis spectroscopy.