Four novel multifunctional polyoxometalate (POM)-based inorganic-organic hybrid compounds, [alpha(2)-P2W17O61{(RGe)}](7-) (Ge-1, R-1 = HOOC(CH2)(2)- and Ge-2, R-2 = H2C=CHCH2-) and [alpha(2)-P2W17O61{(RSi)(2)O}(6-) (Si-1, R-1 and Si-2, R-2), were prepared by incorporating organic chains having terminal functional groups (carboxylic acid and allyl groups) into monolacunary site of Dawson polyoxoanion [alpha(2)-P2W17O61](10-). In these POMs, new modification of the terminal functional groups was attained by introducing organogermyl and organosilyl groups. Dimethylammonium salts of the organogermyl complexes, (Me2NH2)(7)[alpha(2)-P2W17O61(R1Ge)] center dot H2O MeN-Ge-1 and (Me2NH2)(7)[alpha(2)-P2W17O61(R2Ge)] center dot 4H(2)O MeN-Ge-2, were obtained as analytically pure crystals, in 22.8% and 55.3% yields, respectively, by stoichiometric reactions of [alpha(2)-P2W17O61](10-) with separately prepared Cl3GeC2H4COOH in water, and H2C = CHCH2GeCl3 in a solvent mixture of water/acetonitrile. Synthesis and X-ray structure analysis of the Dawson POM-based organogermyl complexes were first successful. Dimethylammonium salts of the corresponding organosilyl complexes, (Me2NH2)(6){alpha(2)-P2W17O61{(R1Si)(2)O}] center dot 4H(2)O MeN-Si-1 and (Me2NH2)(6)[alpha(2)-P2W17O61{(R2Si)(2)O}] center dot {6H(2)O MeN-Si-2, were also obtained as analytically pure crystalline crystals, in 17.1% and 63.5% yields, respectively, by stoichiometric reactions of [alpha(2)-P2W17O61](10-) with NaOOC(CH2)(2)Si(OH)(2)(ONa) and H2C=CHCH2Si(OEt)(3). These complexes were characterized by elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), FTIR, solid-state (P-31) and solution (P-31, H-1, and C-13) NMR, and X-ray crystallography.