An evidence for conversion of A-PW9O349− derivatives to A-PW10O379− derivatives. Synthesis and characterization of [(A-PW9O34)2(H2OM)3CO3]11− (M = Sm(III), Eu(III) and Gd(III)) and [(PW10Sm2O38)4(W3O8(H2O)2(OH)4)]22− (M = Sm(III) and Gd(III))

► A-PW9O349− reacts with aqueous carbonate solution of Sm(III), Eu(III) and Gd(III). ► The products are [(A-PW9O34)2(H2OM)3CO3]11− and [(PW10M2O38)4(W3O8(H2O)2(OH)4))]22−. ► The new complexes have been isolated and characterized by elemental analysis, IR, 31P NMR spectroscopy, TGA and X-ray single crystal structure analysis. ► The 31P NMR spectroscopy suggest decomposition of sandwich type complexes and formation of tetrameric species for Eu(III) derivatives.