Organic-soluble lacunary {M2(P2W15)2} polyoxometalate sandwiches showing a previously unseen αββα isomerism

Abstract

New polyoxometalate ‘sandwiches’ have been formed where two [P₂W₁₅O₅₆]¹²⁻ lacunary Dawson clusters encapsulate two transition metal ions to give clusters with the general formula [M^II₂(P₂W₁₅O₅₆)₂]²⁰⁻ (where M = Mn, Co, and Ni respectively), [Fe^III₂(P₂W₁₅O₅₆)₂]¹⁸⁻, and [Cu^II₄(P₂W₁₅O₅₆)₂]¹⁶⁻. The Mn, Co, and Ni clusters exhibit a hitherto unseen αββα isomeric geometry and all five compounds are associated with tetrabutylammonium cations which allow for their dissolution in non-aqueous solvent.