Alpha and beta isomers of tetrahafnium(iv) containing decatungstosilicates, [Hf4(OH)6(CH3COO)2(x-SiW10O37)2]12− (x = α, β)†
Abstract
The two dimeric, Hf-containing tungstosilicates [Hf4(OH)6(CH3COO)2(α-SiW10O37)2]12− (1) and [Hf4(OH)6(CH3COO)2(β-SiW10O37)2]12− (2) have been synthesized by reacting HfCl4 with [γ-SiW10O36]8− in potassium acetate solutions at pH = 3.6 and 4.8, respectively. Polyanions 1 and 2 comprise a tetrahafnium(IV) assembly {Hf4(OH)6(CH3COO)2} sandwiched between two dilacunary [α-SiW10O36]8− (in 1) or {β-SiW10} (in 2) Keggin type decatungstosilicates. This implies that the starting precursor {γ-SiW10} isomerizes in situ to [β-SiW10O37]10− and then to [α-SiW10O37]10− by controlled variation of pH and temperature. The hydrated