Synthesis and Structure of Dawson Polyoxometalate-Based, Multifunctional, Inorganic–Organic Hybrid Compounds: Organogermyl Complexes with One Terminal Functional Group and Organosilyl Analogues with Two Terminal Functional Groups

Four novel multifunctional polyoxometalate (POM)-based inorganic–organic hybrid compounds, [α2-P2W17O61{(RGe)}]7– (Ge-1, R1 = HOOC(CH2)2– and Ge-2, R2 = H2C═CHCH2–) and [α2-P2W17O61{(RSi)2O}]6– (Si-1, R1 and Si-2, R2), were prepared by incorporating organic chains having terminal functional groups (carboxylic acid and allyl groups) into monolacunary site of Dawson polyoxoanion [α2-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[α2-P2W17O61(R1Ge)]·H2O MeN-Ge-1 and (Me2NH2)7[α2-P2W17O61(R2Ge)]·4H2O MeN-Ge-2, were obtained as analytically pure crystals, in 22.8% and 55.3% yields, respectively, by stoichiometric reactions of [α2-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[α2-P2W17O61{(R1Si)2O}]·4H2O MeN-Si-1 and (Me2NH2)6[α2-P2W17O61{(R2Si)2O}]·6H2O MeN-Si-2, were also obtained as analytically pure crystalline crystals, in 17.1% and 63.5% yields, respectively, by stoichiometric reactions of [α2-P2W17O61]10– with NaOOC(CH2)2Si(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 (31P) and solution (31P, 1H, and 13C) NMR, and X-ray crystallography.