{Nb O (OH) (CO ) }: A Macromolecular Polyoxometalate with Close to 300 Niobium Atoms.

A protein-sized (ca. 4.2×4.2×3.6 nm ) non-biologically derived molecule {Nb O (OH) (CO ) } (Nb ) 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, Nb is the second largest cluster so far reported in classic polyoxometalate chemistry (V, Mo, W, Nb, and Ta). Nb can be described as a giant windmill-like cluster aggregate of six nanoscale high-nuclearity PONb units {Nb O (OH) (CO ) } (Nb ) joined together by six additional Nb ions. Interestingly, the 47-nuclearity Nb 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 Nb cluster also provides a new type of topology to very limited family of Nb-O clusters.