Syntheses and molecular structures of monomeric and hydrogen-bonded dimeric Dawson-type trialuminum-substituted polyoxotungstates derived under acidic and basic conditions

Chika Nozaki Kato; Toshifumi Kashiwagi; Wataru Unno; Miyuki Nakagawa; Hidemitsu Uno

doi:10.1021/ic402650g

Syntheses and molecular structures of monomeric and hydrogen-bonded dimeric Dawson-type trialuminum-substituted polyoxotungstates derived under acidic and basic conditions

Inorg Chem. 2014 May 19;53(10):4824-32. doi: 10.1021/ic402650g. Epub 2014 Apr 28.

Authors

Chika Nozaki Kato¹, Toshifumi Kashiwagi, Wataru Unno, Miyuki Nakagawa, Hidemitsu Uno

Affiliation

¹ 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.

PMID: 24773497
DOI: 10.1021/ic402650g

Abstract

The syntheses and molecular structures of the two types of α-Dawson-type trialuminum-substituted polyoxometalates, [B-α-H3P2W15O59{Al(OH2)}3](6-) (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.