title: 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 [Hf(4)(OH)(6)(CH(3)COO)(2)(α-SiW(10)O(37))(2)](12-) (1) and [Hf(4)(OH)(6)(CH(3)COO)(2)(β-SiW(10)O(37))(2)](12-) (2) have been synthesized by reacting HfCl(4) with [γ-SiW(10)O(36)](8-) in potassium acetate solutions at pH = 3.6 and 4.8, respectively. Polyanions 1 and 2 comprise a tetrahafnium(iv) assembly {Hf(4)(OH)(6)(CH(3)COO)(2)} sandwiched between two dilacunary [α-SiW(10)O(36)](8-) (in 1) or {β-SiW(10)} (in 2) Keggin type decatungstosilicates. This implies that the starting precursor {γ-SiW(10)} isomerizes in situ to [β-SiW(10)O(37)](10-) and then to [α-SiW(10)O(37)](10-) by controlled variation of pH and temperature. The hydrated potassium salts of 1 and 2 were investigated in the solid state by single-crystal XRD, FT-IR, thermogravimetric and elemental analyses, and in solution by UV-Vis and (183)W NMR spectroscopy, and electrochemistry.
authors.affiliation: Jacobs University, School of Engineering and Science, P.O. Box 750 561, 28725 Bremen, Germany.
authors.forename: Awatef S
authors.initials: AS
authors.lastname: Assran
authors.forename: Sib Sankar
authors.initials: SS
authors.lastname: Mal
authors.forename: Natalya V
authors.initials: NV
authors.lastname: Izarova
authors.forename: Abhishek
authors.initials: A
authors.lastname: Banerjee
authors.forename: Andreas
authors.initials: A
authors.lastname: Suchopar
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sadakane
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kortz