Insight into hexanuclear peroxotantalum complexes: synthesis, characterization, and efficient catalyst for amidation reaction

Polyoxometalates (POMs), large oxoanions of the group 5 and 6 elements, attract attention due to their use as oxidation-stable catalysts and ligands. Different from the well-known V, Mo, and W POMs, the group V POMs of Ta assemble and are stable only in highly alkaline solution rather than acidic solution. In this paper, we successfully synthesized and structurally characterized two unprecedented peroxotantalum-containing clusters, KNa2[HSe2(TaO2)(6)(OH)(4)(H2O)(2)O-13]center dot 15H(2)O (1) and Cs2K1.5Na1.5[Se-4(TaO2)(6) (OH)(3)O-18]center dot 17H(2)O (2), which comprises a 6-peroxo-6-tantalum core stabilized by two and four selenite centers, respectively. The simple, one-pot synthesis of 1 and 2 involving addition of sodium selenite into the acidified hexatantalate aqueous solution in the presence of hydrogen peroxide could represent a general procedure for incorporating heteroatoms into peroxo-polyoxotantalate species, thus opening new possibilities for this emergent branch of polyoxotantalate chemistry. Moreover, the catalytic properties of these two compounds were investigated using succinic anhydride and phenylamine as the model substrate, and compound 2 presents excellent catalytic activity in the amidation reactions of anhydrides and amines.

Automated summary

This paper reports the successful synthesis and structural characterization of two new polyoxotantalate clusters. These clusters have a 6-peroxo-6-tantalum core stabilized by selenite centers. The simple one-pot synthesis method opens up possibilities for incorporating heteroatoms into peroxo-polyoxotantalate species. Additionally, the compounds exhibit excellent catalytic activity in amidation reactions.