{Nb₂₈₈O₇₆₈(OH)₄₈(CO₃)₁₂}: A Macromolecular Polyoxometalate with Close to 300 Niobium Atoms

Abstract

A protein-sized (ca. 4.2×4.2×3.6 nm³ ) non-biologically derived molecule {Nb₂₈₈ O₇₆₈ (OH)₄₈ (CO₃ )₁₂ } (Nb₂₈₈ ) containing up to 288 niobium atoms has been obtained, which is by far the largest and the highest nuclearity polyoxoniobate (PONb). Particularly, in terms of metal nuclearity number, Nb₂₈₈ is the second largest cluster so far reported in classic polyoxometalate chemistry (V, Mo, W, Nb, and Ta). Nb₂₈₈ can be described as a giant windmill-like cluster aggregate of six nanoscale high-nuclearity PONb units {Nb₄₇ O₁₂₈ (OH)₆ (CO₃ )₂ } (Nb₄₇ ) joined together by six additional Nb ions. Interestingly, the 47-nuclearity Nb₄₇ units generated in situ can be isolated and bridged by copper complexes to form an inorganic-organic hybrid three-dimensional PONb framework, which exhibits effective catalytic activity for hydrolyzing nerve agent simulant of dimethyl methylphosphonate. The unique Nb₄₇ cluster also provides a new type of topology to very limited family of Nb-O clusters.