Isolation of an Asymmetric Lanthanide Polyoxometalate, Na12H[(W5O18)Tb(H2W11O39)]·42H2O, Containing Two Distinct Isopolyanions

AbstractThe structural characterization of a new, asymmetric polyoxoanion, Na 12 H[(W 5 O 18 )Tb(H 2 W 11 O 39 )]·42H 2 O, is reported herein. This new structure was isolated from a mixture of a number of compounds, including the symmetric Na 9 [Tb(W 5 O 18 ) 2 ] sandwich cluster, and the lanthanide-free cluster, Na 10 (H 2 W 12 O 42 ). The major product of the reaction was Na 9 [Tb(W 5 O 18 ) 2 ], and the compound reported here is a minor product that is obtained reproducibly. The salts of these three clusters do not differ significantly in their crystal habit, size, and color. The crystal structure of Na 12 H[(W 5 O 18 )Tb(H 2 W 11 O 39 )]·42H 2 O was determined by single-crystal X-ray diffraction and shows that the cluster is composed of a lacunary Lindqvist (W 5 O 18 ) 6− building block and an unusual lacunary metatungstate (H 2 W 11 O 39 ) 10− polyanion connected through a central Ln 3+ cation. The central Tb 3+ cation has a square antiprismatic symmetry, the lacunary metatungstate has a square pyramidal symmetry, and the lacunary Lindqvist polyanion exhibits a cuboctahedral symmetry. This is the first example of a crystallographically characterized sandwich cluster possessing a lacunary metatungstate (H 2 W 11 O 39 ) 10− ligand.Graphical Abstract[IMAGE]