The influence of lanthanide ionic radii on the formation and stability of the complexes: Synthesis, chemical properties and characterization of [(β-SiW9O34)2(H2OM)3CO3]13− M = Eu3+ and Gd3+

This study has investigated the reaction of A-β-SiW9O3410- with M = Ce3+, Pr3+, Nd3+, Sm3+, Eu3+ and Gd3+ in aqueous Na2CO3 solution and found that sandwich-type polyoxometalates of [(β-SiW9O34)2(H2OM)3CO3]13− are formed only with Eu3+ and Gd3+. The complexes were synthesized at room temperature and isolated as K+/Na+ salt, but single crystal structure determination was carried out on (NH4)12Na[(β-SiW9O34)2(H2OGd)3CO3]·16.5H2O (CH87Gd3N12NaO90.50Si2W18). The complex crystallizes in triclinic system, space group P-1 with a = 11.997 Å, b = 19.618 Å, c = 21.619 Å, α = 64.332°, β = 82.876°, γ = 86.992° and Z = 2. The crystal structure of the complex consist of two lacunary A-β-SiW9O3410- Keggin moieties which are linked by a (H2OGd)3CO3 belt. The results prove the retention of the isomeric form of the starting lacunary anion A-β-SiW9O3410- upon the preparation of the complexes. The title new complexes are less stable than of [(β-SiW9O34)2(H2OM)3CO3]13− M = Y3+ and Yb3+ analogue because of the larger ionic radii of Eu3+ and Gd3+.