A sandwiched-type carbonate-encapsulated yttrium-containing arsenotungstate(III) has been synthesized under mild reaction conditions. The polyanion [NaCH3COO{Y2(H2O)3(B-α-AsW9O33)2(W2O5)(CO3)}]12− (1) was isolated as a solid crystalline material by the reaction of a YIII salt with the sodium salt of trilacunary [AsW9O33]9− in sodium acetate solution. The sodium salt of the polyanion, i.e. Na12[Na(CH3COO){Y2(AsW9O33)2(W2O5)(CO3)(H3O)3}]·22H2O (1a), was characterized by various analytical techniques, such as FT–IR, single-crystal X-ray diffraction (SC–XRD), TGA (thermogravimetric analysis), 13C NMR and ESI–MS (electrospray ionization mass spectrometry). SC–XRD studies revealed that the polyanion crystallizes in the triclinic space group P\overline{1}. The structure showed that the polyanion is a carbonate-encapsulated sandwich-type species, consisting of two trilacunary B-α-[AsW9O33]9−, with a lone-pair-containing AsIII heteroatom, together with two extra tungsten centres and two yttrium cations at the sandwich position, where CH3COO− and Na+ ions act as linkers between the two polyanion units. In addition, we have also synthesized two carbonate-encapsulated germanotungstates(IV), without lone-pair-containing heteroatoms, with the formula [Ln3(A-β-GeW9O34)2(CO3)(H2O)3]13− [Ln = YIII (2) and YbIII (3)], i.e. Y2K3Na4[Y3(A-β-GeW9O34)2(CO3)(H2O)3]·19H2O (2a) and YbK8Na2[Yb(A-β-GeW9O34)2(CO3)(H2O)3]·16H2O (3a), and characterized them by FT–IR, SC–XRD, TGA and ESI–MS. Here, the lanthanide ions act as linkers, extending the structures into higher dimensions. Sodium and potassium ions also play a key role as linkers, further extending the structure. The packing shows the presence of certain hydrophilic pores within the structure.
Sandwich type polyoxometalates encapsulated into the mesoporous material: synthesis, characterization and catalytic application in the selective oxidation of sulfides
