A sandwich-type aluminium complex composed of tri-lacunary Keggin-type polyoxotungstate: synthesis and X-ray crystal structure of [(A-PW9O34)2{W(OH)(OH2)}{Al(OH)(OH2)}{Al(μ-OH)(OH2)2}2]7−Electronic supplementary information (ESI) available: Bond lengths (Å) and angles (°) for 1 (Table S1); bond valence sum calculations for 1 (Table S2). CCDC reference number 779365. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0dt00722f

The synthesis and molecular structure of a dimeric aluminium complex composed of tri-lacunary α-Keggin polyoxometalate is described. The polyoxometalate, K 6 Na[(A-PW 9 O 34 ) 2 {W(OH)(OH 2 )}{Al(OH)(OH 2 )}{Al(μ-OH)(OH 2 ) 2 } 2 ]·19H 2 O ( KNa-1 ), afforded by the reaction in water of a tri-lacunary Keggin polyoxotungstate with excess aluminium nitrate, followed by crystallization from water, was obtained as analytically pure, homogeneous, colorless crystals. The compound KNa-1 was characterized by elemental analysis, TG/DTA, FT-IR, solution NMR ( 31 P, 27 Al, and 183 W), and X-ray crystallography. The single-crystal X-ray structure analysis revealed that two 6-coordinate aluminium ions linked with two bridging hydroxyl groups and four water molecules, i.e. , [Al III 2 (μ-OH) 2 (OH 2 ) 4 ] 4+ ; a unit of a 6-coordinate tungsten ion linked with a hydroxyl group and a water molecule, i.e. , [W(OH)(OH 2 )] 5+ ; a unit of a 6-coordinate aluminium ion linked with a hydroxyl group and a water molecule, i.e. , [Al(OH)(OH 2 )] 2+ , were sandwiched between two tri-lacunary α-Keggin polyoxotungstates, resulting in an overall C s symmetry. This paper describes the synthesis and molecular structure of a dimeric aluminium complex composed of tri-lacunary α-Keggin polyoxometalate, K 6 Na[(A-PW 9 O 34 ) 2 {W(OH)(OH 2 )}{Al(OH)(OH 2 )}{Al(μ-OH)(OH 2 ) 2 } 2 ]·19H 2 O.