Two dimeric head-on complexes of yttrium containing silico- and germanotungstate were isolated from the one-pot reaction of Y(NO3)(3)center dot 6H(2)O with the lacunary Na-10MW9O34]center dot 16H(2)O (M = Si and Ge) building blocks in an acetate buffer at pH 4.5. Both polyanions were structurally characterized using various solid-state analytics, such as single-crystal X-ray diffraction, single-crystal X-ray analysis shows that both polyanions crystallize in the monoclinic crystal system (S.G. P2(1)/c). FT-IR spectroscopy, or thermogravimetric analysis. The stability of the polyanion in aqueous solution was studied by multinuclear NMR spectroscopy (W-183, Y-89, Si-29, C-13, and H-1). As expected, the W-183 NMR spectra display six peaks in the intensity ratio of 4:4:2:4:4:4 which indicates that both polyanions exist as dimeric entities in aqueous solution.(C) 2010 Elsevier B.V. All rights reserved.