Kato Chika Nozaki, Kashiwagi Toshifumi, Unno Wataru, Nakagawa Miyuki, Uno Hidemitsu
Department of Chemistry, Faculty of Science and ‡Green Chemistry Research Division, Research Institute of Green Science and Technology, Shizuoka University , 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan.
Inorg Chem. 2014 May 19;53(10):4824-32. doi: 10.1021/ic402650g. Epub 2014 Apr 28.
The syntheses and molecular structures of the two types of α-Dawson-type trialuminum-substituted polyoxometalates, B-α-H3P2W15O59{Al(OH2)}3 (1) and [B-α-H3P2W15O59{Al(OH)}2{Al(OH2)}]2(16-) (2), are described herein. The potassium and cesium salts of 1, K6[B-α-H3P2W15O59{Al(OH2)}3]·14H2O (K-1), and Cs6[B-α-H3P2W15O59{Al(OH2)}3]·13H2O (Cs-1) were formed by a stoichiometric reaction in water of trilacunary α-Dawson polyoxotungstate with aluminum nitrate under acidic conditions (pH ∼3). The potassium/sodium and tetramethylammonium/sodium salts of 2, K14Na2[B-α-H3P2W15O59{Al(OH)}2{Al(OH2)}]2·30H2O (KNa-2) and [(CH3)4N]14Na2[B-α-H3P2W15O59{Al(OH)}2{Al(OH2)}]2·39H2O (TMANa-2) were obtained under basic conditions (pH ∼9). These compounds were characterized by X-ray structure analyses, elemental analyses, thermogravimetric/differential thermal analyses, Fourier transform infrared, and solution (31)P, (27)Al, and (183)W NMR spectroscopy. The polyoxoanion 1 is a monomeric, α-Dawson-type structure, resulting in an overall C3v symmetry, while the polyoxoanion 2 is a hydrogen-bonded dimeric structure, resulting in an overall S3 symmetry in the solid state. The pH dependence of polyoxoanions 1 and 2 in aqueous solution was also investigated by (31)P NMR spectroscopy.
