2081-12-1Relevant articles and documents
Tuning metal stoichiometry in heterometal alkoxides: First structurally characterised molecular precursor to BaZrO3
Veith, Michael,Mathur, Sanjay,Huch, Volker,Decker, Timo
, p. 1327 - 1332 (2007/10/03)
Manipulable metal ratios are accessible in a series of heterometal Ba-Zr alkoxides by changing the size and the charge of the ligands. The synthesis and characterisation of four mixed-metal Ba-Zr species [BaZr2(OtBu)10] (1), [Ba2Zr(OtBu)8(tBuOH)(THF)2] (2), [BaZr(OtBu)6(THF)2] (3) and [BaZr(OH)(OiPr)5(iPrOH)3]2 (4), based on different Ba/Zr stoichiometries, are reported. The molecular structures of 1, 2, and 4 have been determined by single-crystal X-ray diffraction studies. 1 exhibits a bow-tie structural motif in which a trigonally distorted six-coordinate barium atom is chelated by two bipyramidal {Zr(OtBu)5}- units. 2 reveals a triangular Ba2Zr(μ3-OrBu)2(μ 2-OtBu)3 core structure t formed by the fusion of three oclahedra built about two Ba atoms and a Zr atom. The structure is unique in terms of the distribution of terminal ligands at each of the metal centers. One of the barium atoms possesses one -OtBu and one tBuOH as terminal ligands, while the terminal ligands on the second barium atom are two THF molecules; the zirconium center bears -OtBu groups as the terminal ligands. Hydrolysis of compound 3 with one equivalent of water, followed by alcoholysis (iPrOH) of the resulting product, gave 4. The structure of 4 shows a planar tetrametallic Ba2Zr12 frame capped by two μ3-hydroxo ligands. The coordination figure of the zirconium atoms resembles a distorted octahedron, whereas the geometry of the barium centers is best described as capped trigonal prisms. Both 3 and 4 are excellent precursors to morphologically pure BaZrO3 ceramic by the sol-gel process.
