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Tuning Metal Stoichiometry in Heterometal Alkoxides: First Structurally Characterised Molecular Precursor to BaZrO 3
Author(s) -
Veith Michael,
Mathur Sanjay,
Huch Volker,
Decker Timo
Publication year - 1998
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199809)1998:9<1327::aid-ejic1327>3.0.co;2-u
Subject(s) - chemistry , octahedron , crystallography , barium , zirconium , crystal structure , trigonal bipyramidal molecular geometry , stoichiometry , metal , molecule , ligand (biochemistry) , pentagonal bipyramidal molecular geometry , inorganic chemistry , organic chemistry , biochemistry , receptor
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 [BaZr 2 (O t Bu) 10 ] ( 1 ), [Ba 2 Zr(O t Bu) 8 ( t BuOH)(THF) 2 ] ( 2 ), [BaZr(O t Bu) 6 (THF) 2 ] ( 3 ) and [BaZr(OH)(O i Pr) 5 ( i PrOH) 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(O t Bu) 5 } − units. 2 reveals a triangular “Ba 2 Zr(μ 3 ‐O t Bu) 2 (μ 2 ‐O t Bu) 3 ” core structure formed by the fusion of three octahedra 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 –O t Bu and one t BuOH as terminal ligands, while the terminal ligands on the second barium atom are two THF molecules; the zirconium center bears –O t Bu groups as the terminal ligands. Hydrolysis of compound 3 with one equivalent of water, followed by alcoholysis ( i PrOH) of the resulting product, gave 4 . The structure of 4 shows a planar tetrametallic Ba 2 Zr 2 frame capped by two μ 3 ‐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 BaZrO 3 ceramic by the sol‐gel process.