Isomerically pure complexes of [As2W18Cd4(H2O)2O68]10 and [As2W18Zn2(CdOH2)2O68]10 were synthesized in high yield by self-assembly of WO2 4 and HAsO2 4 (18 : 2) solution with the stoichiometric ratio of Cd2þ and Zn2þ ions. The complexes were characterized by elemental analysis, IR, Raman, 113Cd NMR spectroscopy, and single crystal structure analysis. Single crystal structure analysis was carried out on (NH4)10[As2W18Cd4(H2O)2O68] 23H2O which crystallized in the monoclinic system, space group C2/c with a¼23.512(3)A ˚ , b¼12.480(2)A ˚ , c¼30.583(4)A ˚ , ¼95.597(3), Z¼4, and V¼8931(2)A ˚ 3. The structure consists of two B-AsW9O9 34 Keggin moieties linked via a rhomb-like Cd4O14 group leading to a C2h symmetry sandwich-type complex. Double- and single-line 113Cd NMR spectra of [As2W18Cd4(H2O)2O68]10 and [As2W18Zn2(CdOH2)2O68]10, respectively, confirm C2h symmetry for both anions in solution. Replacement of Cd2þ with Zn2þ in [As2W18Zn4(H2O)2O68]10 takes place only under vigorous conditions.
