The influence of lanthanide ionic radii on the formation and stability of the complexes: Synthesis, chemical properties and characterization of [(β-SiW_9O_(34))_2(H_2OM) _3CO_3]~(13-) M = Eu~(3+) and Gd ~(3+)

摘要

This study has investigated the reaction of A-β-SiW9O3410- with M = Ce~(3+), Pr~(3+), Nd~(3+), Sm~(3+), Eu ~(3+) and Gd~(3+) in aqueous Na_2CO_3 solution and found that sandwich-type polyoxometalates of [(β-SiW _9O_(34))_2(H_2OM)_3CO _3]~(13-) are formed only with Eu~(3+) and Gd ~(3+). The complexes were synthesized at room temperature and isolated as K_+/Na_+ salt, but single crystal structure determination was carried out on (NH_4)_(12)Na[(β-SiW _9O_(34))_2(H_2OGd)_3CO _3]·16.5H_2O (CH_(87)Gd_3N _(12)NaO_(90.50)Si_2W_(18)). The complex crystallizes in triclinic system, space group P-1 with a = 11.997, b = 19.618, c = 21.619, 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 (H_2OGd) _3CO_3 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-SiW_9O_(34))_2(H_2OM) _3CO_3]~(13-) M = Y~(3+) and Yb_(3+) analogue because of the larger ionic radii of Eu~(3+) and Gd ~(3+).