β-{Cr[RC(CH2O)3]2Mo6O18}3−: the first organically-functionalized β isomer of Anderson-type polyoxometalates

Abstract

The exploration and discovery of new POM species with novel structural motifs are core prerequisites and permanent missions in the field of POM chemistry. It has been nearly 30 years since the first butterfly-shaped Anderson-type hetreopolyanions with a centred pentavalent Sb atom, [Sb(OH)₂Mo₆O₂₂]⁵⁻, named as the β isomer, was discovered in 1988. Yet the corresponding β isomers with a lower valence metal as the central heteroatom and its triol-functionalized organic derivatives have never been obtained. Herein, for the first time, two novel triol-functionalized butterfly-shaped heteropolyanions, β-{Cr[RC(CH₂O)₃]₂Mo₆O₁₈}³⁻ (R = NH₂, 1; C₂H₅, 2), were synthesized by the reaction of common flat Anderson-type POM, α-[Cr(OH)₆Mo₆O₁₈]³⁻, and triol ligands in hot DMF. Single crystal XRD analysis reveals that β-{Cr[RC(CH₂O)₃]₂Mo₆O₁₈}³⁻ is the first triol-functionalized β isomer of common α-type Anderson POMs. This study will enrich the family of POMs and provide an oportunity for the discovery of more potential POMs-based organic–inorganic hybrid materials.