Synthesis,structure and properties of three novel transition-metal-containing tantalum-phosphate clusters

Peroxide ligation of aqueous metal-oxo clusters provides rich speciation and structural diversity.Here,three novel transition-metal derivatives of polyoxometalate anions,[Ni_(2)(H_(2)O)_(10){P_(4)Ta_(6)(O_(2))_(6)O_(24)}]^(6-)(1a),[Zn(H_(2)O)_(4){P_(4)Ta_(6)(O_(2))_(6)O_(24)}]^(8-)(2a)and[Cd(H_(2)O)_(4){P_(4)Ta_(6)(O_(2))_(6)O_(24)}]^(8-)(3a),have been successfully synthesized by adopting a one-pot reaction strategy.All of these hexatantalates are built from a new-type phosphorus-incorporated hexatantalates.We investigated the solution behaviors,and the peak assignments of the MS spectra indicated some degree of stability of them in water.Furthermore,the proton-conducting ability of compound 1a was also explored and it has shown well conductivity at high relative humidities,with conductivity achieved 1.22×10^(-3) S/cm(85℃,90%RH).

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,KNa_(2)[HSe_(2)(TaO_(2))_(6)(OH)_(4)(H_(2)O)_(2)O_(13)]·15H_(2)O(1)and Cs_(2)K_(1.5)Na_(1.5)[Se_(4)(TaO_(2))_(6)(OH)_(3)O_(18)]·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.